Dissertations / Theses on the topic 'Cardiac surgery'

Background: Frailty is a geriatric syndrome of impaired resistance to stressors which has been implicated in the pathogenesis and prognosis of cardiovascular disease. Our objective was to systematically explore the role of frailty in patients with cardiovascular disease, and determine the incremental prognostic value of frailty (as measured by gait speed) for predicting adverse events in elderly patients with cardiovascular disease undergoing cardiac surgery.
Methods: After performing a systematic review of the literature, a multi-center prospective cohort of elderly patients undergoing cardiac surgery was assembled. Patients were evaluated with a questionnaire and timed 5-meter gait speed test, with frailty defined as a time taken to walk 5 meters ≥6 seconds. The composite endpoint was postoperative mortality or major morbidity.
Results: Based on nine previous studies, the prevalence of frailty was found to be 2-4 fold greater in patients with cardiovascular disease. Two studies suggested that frailty was a risk factor for mortality, although none specifically addressed frailty as a risk factor for adverse events in response to a cardiac surgery. Our cohort consisted of 131 patients undergoing cardiac surgery with a mean age of 75.8±4.4 years and 34% females. Thirty patients experienced the composite endpoint and frailty (slow gait speed) was an independent predictor (odds ratio 3.05, 95% confidence interval 1.23, 7.54). Addition of frailty to traditional risk assessment models resulted in notable improvements in model performance.
Conclusion: The prevalence of frailty is increased in patients with cardiovascular disease. Frailty, as measured by 5-meter gait speed, is a simple and effective test to identify a subset of vulnerable elders who have an incrementally higher risk of adverse events after cardiac surgery. Further studies are needed to validate the optimal cut-off for slow gait speed.
Objectif: La fragilité est un syndrome gériatrique qui signifie une diminution de la résistance au stress physiologique impliquée dans la pathogénèse et le pronostique des maladies cardiovasculaires. Notre objectif était de revoir de façon systématique le rôle de la fragilité dans les maladies cardiovasculaires et de déterminer la valeur incrémentielle de la fragilité (telle que mesurée par la vitesse de marche) pour prédire la mortalité et la morbidité chez les sujets âgés atteints de maladie cardiovasculaire subissant une chirurgie cardiaque.
Méthodes: Après avoir revu la littérature systématiquement, une cohorte multicentrique prospective de sujets âgés subissant une chirurgie cardiaque a été assemblée. Les sujets ont été évalués à l'aide d'un questionnaire et du test de vitesse de marche sur 5 mètres avec la fragilité définie comme étant un temps ≥6 secondes pour marcher 5 mètres. L'issue primaire étant un composé de la mortalité postopératoire et des complications majeures.
Résultats: Neuf études précédentes ont démontré que la prévalence de la fragilité était 2-4 fois plus élevée chez les patients avec une maladie cardiovasculaire. Deux études ont démontré que la fragilité était un facteur de risque pour la mortalité, cependant, aucune étude n'avait précisément adressé la fragilité comme facteur de risque après une chirurgie cardiaque. Notre cohorte incluait 131 sujets subissant une chirurgie cardiaque dont l'âge moyen était de 75.8±4.4 ans et 34% étaient des femmes. Trente patients ont développé l'issue primaire et la fragilité (faible vitesse de marche) était un prédicteur indépendant (odds ratio 3.05, 95% confidence interval 1.23, 7.54). L'inclusion de la fragilité au modèle de prédiction traditionnel a eu comme résultat une nette amélioration des performances du modèle.
Conclusion: La prévalence de fragilité est plus élevée chez les sujets âgés atteints de maladie cardiovasculaire. La vitesse de marche est un test simple et efficace pour identifier une sous-population de patients vulnérables ayant un risque plus élevé de mortalité et morbidité après une chirurgie cardiaque. D'autres études sont nécessaires pour valider la valeur seuil optimale de vitesse de marche.

Cardiac surgery is traditionally a heavy user of blood and blood products. Until recently, the benefits of transfusion have been largely assumed and the risks relatively ignored. This has prompted us to examine new ways of minimising patient exposure to donor red blood cells (RBC's). At the present time, most clinical guidelines for RBC transfusion are based mainly upon haemoglobin concentration ([Hb]). As [Hb] may be artificially depressed by the haemodiluting effect of the heavy clear fluid load associated with cardiac surgery, transfusing based upon [Hb] alone may overestimate the requirement for RBC's. Where such haemodilution is present, systemic oxygenation may be maintained through a viscosity mediated patho-physiological response. The work reported in this thesis attempts to explore the relative contribution of both red cell volume (RCV) and plasma volume (PV) to the anaemia encountered following cardiac surgery while also examining factors that may be associated with a low post-operative RCV. In addition, we have explored on a theoretical basis what [Hb] would represent a critical level of systemic oxygen delivery (DO2Crit). Taken together, this has allowed us to develop an RCV based transfusion guideline aimed at reducing the incidence of unnecessary (and potentially counter-productive) RBC transfusion. As RBC's may be associated with pulmonary endothelial damage, we have also studied the impact of the RCV guideline developed on post-operative acute lung injury (ALI). Finally, in a separate study, the merits of a simple activated clotting time (ACT) based system of anti-coagulation management for cardiopulmonary bypass (CPB) versus that of an individualised heparin management system (HMS) are described.

Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice. In cardiac surgery, one-third of the patients experience episodes of AF during the first postoperative days (postoperative AF), and patients with preoperative AF (concomitant AF) can be offered ablation procedures in conjunction with surgery, in order to restore ordinary sinus rhythm (SR). The aim of this work was to study the relation between postoperative AF and inflammation; the long-term consequences of postoperative AF on mortality and late arrhythmia; and atrial function after concomitant surgical ablation for AF. In 524 open-heart surgery patients, C-reactive protein (CRP) serum concentrations were measured before and on the third day after surgery. There was no correlation between levels of CRP and the development of postoperative AF. All 1,419 patients with no history of AF, undergoing primary aortocoronary bypass surgery (CABG) in the years 1997–2000 were followed up after 8.0 years. The mortality rate was 191 deaths/1,000 patients (19.1%) in patients with no AF and 140 deaths/419 patients (33.4%) in patients with postoperative AF. Postoperative AF was an age-independent risk factor for late mortality, with a hazard ratio (HR) of 1.56 (95% CI 1.23–1.98). Postoperative AF patients had a more than doubled risk of death due to cerebral ischaemia, myocardial infarction, sudden death, and heart failure compared with patients without AF. All 571 consecutive patients undergoing primary CABG during the years 1999–2000 were followed-up after 6 years. Questionnaires were obtained from 91.6% of surviving patients and an electrocardiogram (ECG) from 88.3% of all patients. In postoperative AF patients, 14.1% had AF at follow-up, compared with 2.8% of patients with no AF at surgery (p<.001). An episode of postoperative AF was found to be an independent risk factor for development of late AF, with an adjusted risk ratio (RR) of 3.11 (95% CI 1.41–6.87). Epicardial microwave ablation was performed in 20 open-heart surgery patients with concomitant AF. Transthoracic echocardiography was performed preoperatively and at 6 months postoperatively. At 12 months postoperatively 14/19 patients (74%) were in SR with no anti-arrhythmic drugs. All patients in SR had preserved left and right atrial filling waves (A-waves) and Tissue velocity echocardiography (TVE) showed preserved atrial wall velocities and atrial strain. In conclusion, postoperative AF is an independent risk factor for late mortality and later development of AF. There is no correlation between the inflammatory marker CRP and postoperative AF. Epicardial microwave ablation of concomitant AF results in SR in the majority of patients and seems to preserve atrial mechanical function.

Ischaemic heart disease (IHD) is the leading cause of death worldwide and according to the World Health Organisation the number of patients with IHD will reach 19 million by 2020 if current trends continue. While coronary artery bypass graft (CABG) surgery remains the treatment of choice for the severest form of the disease, the detrimental effects of peri-operative myocardial injury particularly in the form of myocardial ischaemia-reperfusion injury (IRI) accounts for significant levels of morbidity and mortality particularly in high-risk patients. The past four decades have seen advances in cardioprotective strategies especially within the disciplines of cardioplegia and anaesthesia. Despite this, improvements in patient survival have been limited. Researchers and clinicians alike have called for novel ways of protecting the heart, directing their attention to cellular and mitochondrial pathways which may hold the key to improving survival. This thesis covers a fascinating exploration into the cardioprotective effects brought about by the inhibition of the mitochondrial permeability transition pore (mPTP) using cyclosporin A (CsA), as well as the role of remote ischaemic preconditioning (RIPC) in limiting the extent of myocardial injury in the setting of complex cardiac bypass surgery. In summary, this thesis examines both pharmacological and non-pharmacological strategies for protecting the heart in the setting of cardiac surgery. Despite decades of advancement in research within this field, the consequences of ischaemia-reperfusion injury remain ever-present. As a result, it is hoped that the research in this thesis will make a positive contribution to the body of evidence currently available for the benefit of patients with IHD.

Brain injury continues to be one of the most feared complications following cardiac procedures. While clinically overt cerebrovascular accidents are extremely well characterised and relatively rare under optimised conditions, at the other end of the spectrum, subclinical brain injury – which consists of post-operative cognitive dysfunction and silent brain infarcts (SBIs) – is poorly defined but of greater incidence. The lack of knowledge of subclinical brain injury is in large part due to lack of an objective means of measurement, meaning it is quantified using variable definitions and generally subjective clinical assessments. Structural magnetic resonance neuroimaging techniques are a potentially useful tool that can objectively characterise subclinical brain injury by providing a means to measure the neural network disruption that underlies even subtle cognitive and emotional deviations. The aim of this thesis was (i) to frame the true extent of the problem that is subclinical brain injury after cardiac surgery and (ii) to develop structural MRI techniques that might produce a biomarker to objectively measure neural network changes associated with subclinical brain injury.

The occurrence of major adverse cardiac events (MACE) is a common perioperative complication and contributing factor for the increase risk of morbidity and mortality in adult patients undergoing non-cardiac surgery. The most reasonable and evidence-based option to reduce the risk of MACE and perioperative morbidity and mortality is a consistent assessment of the functional capacity for non-cardiac patients prior to non-cardiac surgical procedures. According to Fleisher et al. (2014), individuals with a decreased or unmeasurable functional capacity should be referred to a cardiologist for evaluation and cardiac risk stratification prior to surgery. The Duke Activity Status Index (DASI) tool has demonstrated to be an effective tool in assessing functional capacity and identifying individuals without a known cardiac history who may be at risk for perioperative cardiac complications.

This quality improvement project focused on the implementation and use of the DASI tool into the preexisting formal preoperative procedure. Use of the DASI tool focused on accurate measurements of the surgical patient’s functional capacity and evaluation of potential risk factors for MACE. As a result of using the DASI tool in the preoperative process, several non-cardiac adult patients were recognized as being at risk for MACE and underwent cardiac interventional procedures following referral to a cardiologist for preoperative evaluation. Assessing functional capacity using the DASI tool prior to non-cardiac surgical procedures has proven to be both valuable and medically beneficial for the non-cardiac adult patients in evaluation of the risk for MACE.

Thesis advisor: Dorothy A. Jones
Cardiac surgery is frequently performed as a surgical intervention within the United States; but there is little known about how the older adult (70 years of age or greater) experiences cardiac surgery and recovery over time. This qualitative research study utilized narrative methodology to interview 13 older adults to inform understanding of the older adult's cardiac surgical experience. The purpose of this study was to describe the story of the older adult both coming to surgery (preoperative period) and during the transitional time of the acute recovery period following cardiac surgery (up to 8 weeks after cardiac surgery). The primary research question asked was "What stories do older adults tell of their experience of cardiac surgery from the preoperative period through the first 2 months postoperatively?" Using narrative analysis of participant discourse, consisting of both structural (re-storying of narrative content) and thematic analysis of interview content, there emerged an overarching story of older adult experience of cardiac surgery which can be described thematically as: Moving toward healing: engaged in and appreciating life while conscious of time passing amidst the primacy and struggle of the symptom experience. Knowledge gained from this study can help to broaden the understanding of the experience and the trajectory of older adult recovery after cardiac surgery, and also serves to inform nursing education and practice models, nursing interventions, instrument development and innovative models of care designed to support the perioperative care of older adults
Thesis (PhD) — Boston College, 2015
Submitted to: Boston College. Connell School of Nursing
Discipline: Nursing

Cardiac disease is common and many cases require invasive surgical intervention. Most cardiac surgeries, for example, require stopping the patient’s heart. A percutaneous, beating heart, catheter-based system has been proposed as a less invasive option. Toward this goal, a mechanical device for bracing cardiac catheters against safe structures in the heart has been developed to allow more robust probing of heart tissue. The device presented here is rigid in its bracing conformation to support a catheter inside of the cardiac chambers, but is compliant enough to be delivered to the heart via the patient’s vasculature. This brace aims to provide comparable surgical dexterity in a less invasive protocol.
Engineering Sciences

Minimally invasive surgery refers to modifications to traditional procedures that reduce the disruption of the body’s normal function. This thesis examined three techniques designed to reduce the invasiveness of major cardiac procedures. Coronary artery bypass grafting performed without cardiopulmonary bypass or any manipulation of the ascending aorta (anaortic off-pump) was found to reduce the incidence of post-operative stroke, mortality and other complications. An anaortic off-pump surgical technique that achieves achieve complete revascularisation and utilising total-arterial grafts was developed. Transcatheter aortic valve implantation (TAVI) is a novel minimally invasively method of treating severe aortic stenosis. Despite the complexity of the procedure, TAVI was successfully introduced into an Australian hospital with excellent perioperative outcomes. The transapical approach was demonstrated to be a feasible alternative in patients who were not suitable for transfemoral access, though there was increased risk of vascular and bleeding complications. Prophylactic extracorporeal membrane oxygenation in selected very high-risk TAVI patients may also help avoid the consequences of intraoperative complications and the need for emergent support. Lastly, a novel minimally invasive strategy for managing high-risk patients with combined aortic stenosis and multivessel coronary artery disease was described. Robotic ‘telemanipulators’ have enabled complex cardiac procedures to be performed via port-access. Systematic reviews of published studies demonstrated improved postoperative recovery in robotic-assisted coronary and mitral valve surgery, whilst maintain the quality of the procedure. High intra-procedural costs are largely offset by faster discharge from hospital and return to work. A step-wise program for introducing robotic-assistance into coronary surgery was developed and implemented in an Australian public hospital. Though major challenges limited progression.

Background: Previous research indicates that for some individuals, quality of life (QoL) post-cardiac surgery (CABG or PTCA ) declines from pre-surgery levels. Using the framework of Leventhal's Common-Sense Model, this longitudinal study examined the associations between patients' illness perceptions and coping strategies, their QoL, attendance at cardiac rehabilitation and lifestyle changes. It was hypothesised that a more negative profile of illness beliefs (weaker control beliefs, belief in more severe consequences, poorer understanding of the condition, and negative emotional representations) together with the use of more emotional coping strategies would be associated with poorer QoL. It was also hypothesised that attendance at cardiac rehabilitation would be associated with greater control beliefs, more severe consequences and a causal attribution of lifestyle. Sample and Methods: 113 patients (93 male, mean age 66 (8.93) who were about to undergo cardiac surgery were recruited from two hospitals. Questionnaire measures of illness perceptions (IPQ-R), coping (CHIP) and cardiac-specific QoL (MacNew) were administered at four time points: pre-surgery, post-surgery, post cardiac rehabilitation, and one-year follow up. Data on attendance at rehabilitation and health behaviours were collected via hospital records and patient report. Results: The best predictors of QoL were not cognitive representations of the cardiac problems, but negative emotional representations and associated emotion-focussed coping strategies, implying that an emotion-regulation intervention could be targeted to improve outcome. The predictive ability of initial QoL on QoL at later stages implies this might be best introduced pre-surgery. Having less severe consequence beliefs prior to surgery predicted greater attendance at cardiac rehabilitation. A better understanding of the cardiac condition predicted attendance at cardiac rehabilitation. There was no evidence of change in lifestyle post-rehabilitation.Discussion: The findings that emotional representations of cardiac problems and the use of emotion focussed coping strategies were predictors of quality of life suggest that interventions to foster adaptive emotion regulation may improve outcome in these patients. Findings with respect to attendance at rehabilitation varied somewhat from the previous literature, possibly because the present study sampled patients who were having elective surgery, rather than those who had recently had a heart attack. The importance of studying defined populations and also the issue of when measures are obtained in relation to cardiac events were also highlighted.

Includes bibliographical references.
The vast majority of patients with penetrating cardiac injuries do not reach the hospital alive as the pre-hospital mortality rate for these injuries is in the region of 86%. The patients that do reach the hospital alive are potential survivors and it is obviously crucial that any cardiac injury is detected and managed appropriately. Most of these injuries present with either cardiac tamponade or hypovolaemic shock and are relatively straightforward to diagnose and require immediate surgery. There is, however, a group of patients that are relatively stable with an underlying cardiac injury and it is in these patients that a potential or occult cardiac injury needs to be identified.

Major vascular surgery is associated with a substantial risk of cardiovascular events and death. This risk is of increased importance in prophylactic elective open Abdominal Aortic Aneurysm (AAA) repair, where a balance of risk of rupture and postoperative outcome is assessed prior to management decisions. Further, the UK Small Aneurysm Trial has shown that prophylactic repair of an AAA has no survival benefit for the first three years due to the major adverse cardiac event (MACE) rate of 5-15%. There is however no ideal method of predicting this risk. Cardiac Troponin I (cTnI) is a contractile protein that is a highly sensitive and specific marker of myocardial necrosis. A few case reports have commented on the finding of preoperative asymptomatic elevated cTnI levels and poor outcome in a small number of patients undergoing major vascular surgery. There are however no studies looking at its incidence in the vascular surgical population or its utility as a preoperative marker. Several studies have noted that B-type natriuretic peptide (BNP), a diagnostic and prognostic marker of heart failure, may have a role in predicting MACE in settings including major vascular surgery. There are no studies that have investigated this role in AAA repair alone. The aim of this thesis is to investigate the incidence of, and to determine a possible role for, preoperative elevated cTnI in major vascular surgery. The further aim is to determine if a single preoperative BNP level correlated with MACE and all-cause mortality in elective open AAA repair in both the short and long-term. Comparisons to current accepted risk indices in AAA, and a possible role for BNP in EndoVascular Aneurysm Repair (EVAR) will also be investigated. Patients were recruited in two cohorts: Firstly, a prospective, 2 year observational single centre cohort study of all patients undergoing a vascular procedure, with an expected cardiac event rate >5%, recruited patients who had no clinical or ECG evidence of myocardial ischaemia. Preoperative cTnI was performed in all and postoperative screening (clinical assessment, ECG and cTnI) for cardiac events was performed at days 2, 5 and 30. 213 patient were recruited, of whom 11 (5.2%) had an asymptomatic elevated preoperative cTnI (>0.02 ng/ml). Eight of these patients proceeded directly to theatre, and 2 were delayed but later underwent surgery with a persistently elevated cTnI. Of these 10 patients, 5 (50%) died and 4 (40%) suffered MACE. The remaining patient was delayed due to the poor outcome of the preceding patients, and later underwent an uncomplicated aortic bifurcation graft with a normal cTnI level which had been preceded by coronary intervention. Secondly, a prospective, 2 year observational multi-centre cohort study in the 3 largest vascular units in Glasgow (Gartnavel General Hospital, Glasgow Royal Infirmary and Southern General Hospital) was performed between August 2005 and August 2007, recruiting all patients who were admitted for both elective open AAA repair and EVAR. Preoperative BNP levels were performed and batch analysed at the end of the study. Postoperative screening for cardiac events was performed as described above. Data was collected to allow calculation of risk indices associated with outcome in AAA repair (Glasgow Aneurysm Score [GAS], Vascular physiology only Physiological and Operative Severity Score for enUmeration of Mortality [V{p}-POSSUM], Vascular Biochemical and Haematological Outcome Model [VBHOM], Revised Cardiac Risk Index [RCRI] and Preoperative Risk Score of the Estimation of Physiological Ability and Surgical Stress Score [PRS of E-PASS]). Follow-up was continued to a minimum of 3 years, where possible, with cause of death recorded. 106 of 111 patients were recruited. The median [interquartile range] BNP concentrations in the 16 patients (15%) who suffered immediate postoperative MACE was 206 [118-454] vs 35 [17-61] pg/ml in the remainder (p=0.001). ROC analysis indicated a BNP concentration of 99.5 pg/ml best predicted MACE (area under the curve 0.927), with sensitivity of 88% and specificity of 89%. The BNP in patients who suffered cardiac death was significantly higher than in those that did not (median BNP 496 [280-881] vs 38 [18-84] pg/ml, p=0.043). ROC analysis revealed a cut-off of 448 pg/ml (AUC 0.963), with sensitivity 80%, specificity 100%, positive predictive value 100% and negative predictive value 99%. Not only did higher values of BNP predict MACE, but it was also found to predict all-cause mortality in the immediate (median BNP 100 [84-521] vs 35 [17-81], p=0.028), intermediate (median BNP 201 [97-496] vs 35 [17-73], p<0.001) and long-term (median BNP 98.5 [58-285] vs 32 [17-71.5], p<0.001) postoperative periods. ROC analysis revealed decreasing BNP levels to predict outcome over time, with a BNP of >60.5 pg/ml (AUC 0.761) found to best predict death at 3 years. Whilst BNP was found to predict outcome, most risk indices performed poorly. The GAS, VBHOM and RCRI performed poorly and did not predict any outcome measure. V(p)-POSSUM was, however, found to predict all outcome measures (p=0.028, p=0.030, p=0.038 for MACE, cardiac death and all-cause mortality respectively). The PRS component of E-PASS was found to predict MACE (p=0.019) and cardiac death (p=0.017). BNP performed better than any risk index. During the study period only 40 of 42 patients admitted for elective EVAR were recruited. Of these 40, only 3 suffered a non-fatal MI and 1 died of respiratory failure. BNP was not found to predict MACE or death in this cohort, and due to the small number of patients, and events, no strong conclusions could be drawn. Whilst preoperative elevated cTnI was found to identify patients that were at an increased risk of both postoperative MACE and death following their major vascular surgical procedure, its use in elective open AAA repair is limited due to infrequent occurrence. Preoperative serum BNP concentration, however, predicted postoperative MACE, cardiac death and all-cause mortality in patients undergoing elective open AAA repair on immediate, intermediate and long term follow-up. Further, BNP performed better than any current risk index for elective open AAA surgery. This simple blood test, therefore, offers valuable information regarding risk stratification of prospective surgical patients and should be considered a part of routine preoperative assessment in this prophylactic procedure.

Cognitive impairment is a common consequence of cardiac surgery using cardiopulmonary bypass and embolisation of particulate and gaseous debris is believed to be the most important cause. Using a new generation of transcranial Doppler (TCD) ultrasonography the aim was to quantify gaseous and solid cerebral microemboli during different cardiac surgical procedures and to relate this to cerebral abnormalities identified using magnetic resonance imaging techniques. A substantial reduction in microembolic load was demonstrated with avoidance of cardiopulmonary bypass (CPB). The majority of microemboli detected during cardiac surgical procedure~ were gaseous and use of CPB was associated with a significantly higher proportion of solid microemboli - regarded as potentially more harmful. Reduction or elimination of aortic m~ipulation resulted in a significant reduction in intraoperative cerebral microembolisation with the potential for reduction of postoperative cerebral injury. Microemboli are not' only restricted to the intraoperative period and could be detected postoperatively following aortic valve replacement. Use ofa mechanical prosthesis is associated with significant increases in solid and gaseous microemboli. Functional magnetic resonance imaging (FMRI) performed serially in patients pre- and postoperatively demonstrated a significant overall reduction in taskassociated activation in the postoperative period. However, increased activation in certain regions of interest suggested a compensatory mechanism or adaptive change that may contribute to functional recovery after cerebral injury from microemboli. Then comparing off-pump and on-pump surgery, there was a significant reduction in prefrontal cerebral activation in patients undergoing on-pump surgery but preservation of cerebral activity following off-pump surgery. These changes in activation correlate with intraoperative microembolic load and were persistent at longer-term follow-up. Magnetic resonance spectroscopy of the frontal white matter showed no significant reductions in N-acetyl aspartate (NAA) levels - a marker of neuronal integrity. This was reassuring indicating that neuroaxonal damage is an unlikely explanation of the functional cerebral changes observed with FMRI. Careful assessment and further understanding of the pathophysiology of postoperative neurological injury would allow the development of targeted neuroprotective strategies aiming to reduce the rate and severity of this important complication

Les transfusions de globules rouges représentent le traitement principal de l’anémie. La décision de transfuser représente un vrai dilemme clinique. L’anémie et les transfusions de globules rouges sont toutes les deux associées à des risques et à un moins bon devenir des patients, alors que le bénéfice des transfusions sanguines reste difficile à démontrer. C’est pour cela que la décision de transfuser ne doit pas être pris à la légère et qu’elle doit tenir compte de la balance antre les risques des transfusions de globules rouges et les risques de l’anémie. L’anémie, définie comme un taux d’hémoglobine sous la moyenne pour l’âge, est fréquente chez les enfants en péri-opératoire de chirurgie cardiaque. Les conséquences de l’anémie sont une diminution du transport en oxygène vers les cellules. Le taux d’hémoglobine sous lequel la demande tissulaire en oxygène est compromise n’est pas connue et dépend de l’état de santé du patient et de ses comorbidités. Les causes peropératoires de l’anémie sont surtout le saignement et l’hémodilution. Une diminution de la production d’érythropoïétine endogène, une dérégulation du métabolisme du fer, une production défectueuse de la moelle et la répétition des prélèvements sanguins contribuent à l’anémie postopératoire. L’anémie est associée à des évènements indésirables et un moins bon devenir, mais cette association semble en grande partie expliquée par la pathologie sous-jacente, elle-même associée à l’anémie. Les transfusions en globules rouges sont fréquentes en chirurgie cardiaque pédiatrique. Le rapport bénéfice-risque des transfusions sanguines reste difficile à évaluer. Alors que les études rapportant des bénéfices clairs des transfusions sanguines restent rares, plusieurs travaux observent une association entre les transfusions en globules rouges et une augmentation de la morbidité et mortalité. En outre, les transfusions sanguines demeurent une ressource rare et chère.

Le but de ce travail est de contribuer à une meilleure utilisation des transfusions sanguines chez les patients de chirurgie cardiaque pédiatrique. Dans la première partie du travail, nous avons étudié les déterminants des transfusions en globules rouges et du saignement, qui représentent une des causes principales de transfusion sanguine chez ces patients. Une meilleure identification et une prise en charge adéquate des facteurs qui mènent aux transfusions sanguines devraient diminuer le nombre de transfusions inappropriées. Dans la deuxième partie de ce travail, nous nous sommes penchés sur l’association entre les transfusions sanguines et le mauvais pronostic des patients en étudiant deux approches :l’âge des globules rouges transfusés et l’indication transfusionnelle. Une meilleure compréhension des facteurs associés à un moins bon pronostic devrait permettre de mieux définir les patients qui bénéficieraient réellement de transfusions en globules rouges.

En ce qui concerne les déterminants des transfusions sanguines, nous avons démontré que l’anémie préopératoire était significativement associée aux transfusions sanguines péri-opératoires. Les enfants qui saignent reçoivent beaucoup de produits sanguins. Nous avons déterminé les patients à risque de saignement afin de les reconnaître et les soumettre à des tests de coagulation rapides pour orienter le type de produits sanguins à transfuser en fonction des anomalies de coagulation mises en évidence. Puisque l’anticoagulation par héparine est systématique chez les patients opérés sous circulation corporelle, nous avons étudié si notre protocole de neutralisation de l’héparine avec de la protamine était adéquat. En effet, la persistance d’héparine circulante ainsi qu’un surdosage en protamine sont associés à des saignements postopératoires. Un ratio protamine-héparine de 1:2 semble permettre une neutralisation adéquate de l’héparine chez la majorité des patients sans les exposer à un surdosage en protamine. Finalement, nous avons démontré qu’une stratégie transfusionnelle restrictive en postopératoire permettait de diminuer l’exposition aux transfusions sanguines sans augmenter la morbidité et mortalité de ces enfants. Cela signifie qu’on pourrait éviter des transfusions en globules rouges en prenant en charge l’anémie préopératoire, en développant un algorithme de prise en charge précoce du saignement peropératoire et en diminuant le seuil transfusionnel postopératoire.

La deuxième partie de ce travail avait pour but de préciser l’association qu’il existe entre les transfusions en globules rouges et la morbidité et mortalité postopératoire. L’âge du sang n’a pas l’air d’être un facteur influençant le pronostic des enfants opérés de chirurgie cardiaque. Par contre, ce travail a permis de montrer que c’est probablement l’indication transfusionnelle ou la raison qui mène à la transfusion, plutôt que la transfusion en elle-même qui est associée à un moins bon pronostic. L’association entre les transfusions sanguines et un moins bon pronostic est probablement surestimée par la présence de facteurs confondants comme l’indication transfusionnelle. Les transfusions en globules rouges seraient plutôt un marqueur de risque qu’un facteur de risque de mauvais pronostic.

En conclusion, ce travail contribue au développement de stratégies transfusionnelles plus rationnelles en chirurgie cardiaque pédiatrique. Reposant sur une approche multidisciplinaire, elles assurent une prise en charge structurée et orientée permettant de diminuer l’exposition des enfants aux produits sanguins, avec pour objectif une amélioration du pronostic et une réduction des coûts de prise en charge de ceux-ci.
Doctorat en Sciences médicales
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Bachelors
Health and Public Affairs
Nursing

Aortocoronary bypass or valve surgery usually require cardiac arrest using cardioplegic solutions. Although, in principle, in a number of cases beating heart surgery (so-called off-pump technique) is possible, aortic or valve surgery or correction of congenital heart diseases mostly require cardiopulmonary arrest. During this condition, the heart-lung machine also named cardiopulmonary bypass (CPB) has to take over the circulation. It is noteworthy that the invention of a machine bypassing the heart and lungs enabled complex cardiac operations, but possible negative effects of the CPB on other organs, especially the brain, cannot be neglected. Thus, neuroprotection during CPB is still a matter of great interest. In this review, we will describe the impact of CPB on the brain and focus on pharmacological and non-pharmacological strategies to protect the brain.

Introduction: Hospital acquired infections (HAIs) are an important cause of morbidity and mortality following paediatric cardiac surgery. Aim: To determine the incidence, risk factors for and outcome of postoperative HAIs in the Paediatric Intensive Care Unit (PICU) of the Red Cross War Memorial Children's Hospital (RCWMCH) in Cape Town. Methods: A prospective observational study of all postoperative cardiac patients admitted to PICU from September 2011 to March 2012. The definitions of laboratory confirmed blood stream infections (BSI), urinary tract infections (UTI), and surgical site infections were based on the Centres of Disease Control criteria. Ventilator associated pneumonia (VAP) was diagnosed using a modification of the Clinical Pulmonary Infection Score (CPIS). Results: 110 patients (median age 19 months; 43% male) undergoing 126 surgical procedures were enrolled. Sixty HAIs occurred in 43 (39%) patients (68.3% pulmonary; 13.3% blood; 11.7% wound; 3.3% urine; 3.3% tissue). Nine (8.2%) patients died and their deaths were not related to HAIs.

Despite increasingly sophisticated perioperative management, cardiovascular complications continue to be major challenges for the clinician. As a growing number of elderly patients with known coronary artery disease (CAD) or with risk factors for CAD are undergoing non-cardiac surgery, cardiovascular complications will remain a significant clinical problem in the future. The overall objective of this thesis was to study the incidence of myocardial damage and perioperative adverse cardiac events, to determine predictors of poor outcome and to assess the effect of a medical intervention in patients at risk undergoing non-cardiac surgery. The studies in this thesis were conducted on a total of 952 patients undergoing non-cardiac surgery. Studies I and IV were multicenter studies; whereas the patients included in studies II and III underwent non-cardiac surgery at Linkoping University Hospital, Sweden. The correlation between postoperative myocardial damage and short- and long-term outcome were studied in 546 patients, aged 70 years or older undergoing non-cardiac surgery of at least 30 minutes duration. This study showed a close correlation between postoperative myocardial damage and poor short- as well as long-term outcome. Elevated Troponin T was a strong independent predictor of mortality within one year of surgery. In 186 patients with ASA physical status classification III or IV undergoing non-elective surgery, the incidence of myocardial damage was 33%. In this study preoperative myocardial damage was an independent predictor of major adverse cardiac events in the postoperative period. In 69 patients with ASA physical status classification III & IV undergoing acute hip surgery, we found a close correlation between elevated NT-proBNP value prior to surgery and cardiac complications in the postoperative period. To study the effect of acetylsalicylic acid on postoperative myocardial damage and cardiovascular events, 220 patients at risk were randomized to receive 75 mg of acetylsalicylic acid or placebo 7 days prior to surgery until the third postoperative day. This study showed that treatment with acetylsalicylic acid resulted in an 8% (95% CI 1-15%) absolute risk reduction of having a postoperative major adverse cardiac event. No statistically significant differences of bleeding complications were seen between the groups. In conclusion, this thesis contributes to the understanding of the clinical relevance of elevated cardiac markers (with or without clinical or ECG signs of myocardial damage) in patients undergoing elective or emergency surgery. Moreover, we have identified predictors of poor outcome in the perioperative period that could be used as tools for identifying patients at risk. Finally, we have shown that continuing acetylsalicylic acid in the perioperative period reduced the risk of major adverse cardiac events within 30 days of surgery.

Despite congenital heart malformations are currently treated in infancy and childhood, a great number of patients still need surgical treatment in adult age. For this reason, we have embarked on a multicentric study involving 7 major italian centers (Padova, Milano S.Donato, Milano Niguarda, Bergamo, Bologna, Massa, Napoli), so as to evaluate the impact of cardiac surgery in adults with congenital heart disease in our country and survival determinants. In addition, clinical late morbidity was analyzed in order to to evaluate correlated pre-operative and operative risk factors. Methods We collected data of 856 patients who underwent 1179 procedures from January,1st 2000 to December 31st 2004. Patients were divided into three groups: Group I- Palliation (3.1%): any operation performed to improve patientâ's clinical status without restoring normal anatomy or physiology. Bidirectional cavopulmonary anastomosis and pulmonary artery banding were the most frequent procedures. Group II- Repair (69.7%): first operation performed in the patient, to achieve an anatomic or physiologic repair by separation of the pulmonary from systemic circulation (including also Fontan-types, and 1 and ’½ ventricle repairs). Most frequent procedures were: atrial septal defect closure (35.8%), partial anomalous pulmonary venous connection repair (7.2%), ventricular septal defect closure (5.3%). Group III- Reoperation (27.4%): all procedures performed after repair either anatomic or physiologic. The most frequent procedures were conduit replacement (9.8%), aortic (8.6%) or pulmonary valve replacement (7.7%) . Results Preoperatively 34.6% of patients were in NYHA class I, 48.4% in class II, 14.2% in class III and 2.8% in class IV. Sinus rhythm was present in 83%. There were 1179 procedure performed in 856 patients (1.37 procedure/patient), with a hospital mortality of 3.1%. Overall mean intensive care unit stay was 2.3 days (range:1-102 days). Major complications were reported in 247 pts (28.8%), with postoperative arrhythmias being the most frequent (26%). At mean follow-up of 22 months (range 1 month- 5.5 years), 86% of data were available. Late death occurred in 5 patients (0.5%). Patients were in NYHA class I in 79.3 % , II in 17.6%, III in 2.9%, and only one patient in class IV (0.11%). Ability index was class I in 82%, class II in 13.7% and class III in 2.3%. Overall survival estimates is 82.6% , 99% and 91.8% at 5 years for groups I, II, III respectively. Freedom from adverse events at 5 years is 91% for acyanotic vs 63.9 % for preoperative cyanotic patients (p < 0.0001). Multivariate Cox analysis identifies among the most powerful incremental risk factors for survival preoperative NYHA class IV in cyanotic patients (Hazard Ratio-HR- 8.6, p value 0.001), preoperative NYHA class III (HR 2.7, p value 0.023), and reoperation (HR 2.3, p value 0.029). In addition, multivariate Cox analysis for postoperative morbidity expressed as NYHA class greater than 1, identifies among the most powerful incremental risk factors the length of ICU stay (HR 1.037, CI=1.002-1.072, p=0.036), number of operations (HR 1,445 CI=1,1213-1,721, p<0.001), cyanosis (HR 1,555, CI1,035-2,335, p=0,034), alteration of cardiac rhythm before surgery (HR 1,124, CI=1,040-1,215, p=0,03), pre-operative NYHA class>1 (Hazard Ratio 1,573, CI=0,954-2,593, p=0.076), age > 40y (HR 1,466, CI1,014-2,119, p=0.042). Conclusions Surgery for congenital heart disease in adult age is a safe and a low risk treatment. However patients with preoperative cyanosis show a higher incidence of late non-fatal complications. In addition, better preoperative clinical conditions are correlated with better late clinical outcomes, thus early repair (before cardiac and non cardiac organ deterioration occurs) is advocated.

Despite the benefits of coronary artery bypass graft surgery (CABG), graft closure can still occur and lead to the development of unstable angina, myocardial infarction (MI) and death. Secondary prevention is thus greatly needed in order to prevent future cardiovascular events in the post-CABG patient. Few studies have examined the benefits of cardiac medical therapy specifically among CABG patients. A review of randomized controlled trials (RCT's) was first conducted in order to understand what constitutes appropriate cardiac medical therapy in the post-CABG patient.
The use of aspirin, clopidogrel, coumadin, anti-lipid agents, anti-ischemic medications (beta-blockers, CCB's, nitrates) and ACE inhibitors was then examined among patients enrolled in the Routine versus Selective Exercise Treadmill Testing After Coronary Artery Bypass Graft Surgery (ROSETTA-CABG) Study. We examined the use of these medications among all patients as well as patients with various co-morbidities.

Depression following cardiac surgery is more common than appreciated and can adversely impact length of stay, recovery, and quality of life. The purpose of this study was to identify those at increased risk of developing post-operative depression and to intervene early to decrease the mortality and morbidity associated with post-operative depression. This study prospectively analyzed various patient characteristics, socio-economic factors, and fatalism to determine their relationship to post-operative depression. If a correlation was identified, then pre-operative intervention could be initiated to mitigate the adverse effects of depression on recovery.

Consecutive patients scheduled for coronary bypass or valve surgery were screened for inclusion in the study. Patients under the age of 40, those with pre-existing depression, and patients needing reoperation were excluded. One hundred twenty-five patients who met criteria were followed over a 12-week period. Baseline data relating to heart surgery (Euroscore), socio-economic demographics, depression score (PHQ9), and a fatalism scale were collected. Follow-up assessments for depression occurred at 6 weeks and at 12 weeks post-surgery. Data were collected by chart review and direct face-to-face interviews, and were analyzed utilizing SAS software.

Eighty-four men and 41 women met the inclusion criteria. One hundred fourteen (91%) completed follow-up at 6 weeks, and 105 (84%) completed the follow-up at 12 weeks. The mean fatalism score was 49.4 (22-88), and the mean depression score was 4.0(0-11). Fatalism, Euroscore, baseline PHQ-9 score, gender, race, marital status, education level, church membership, and diabetes explained 22% of the variability in PHQ-9 scores at both 6 and 12 weeks. However, this was not significant (p=> 0.05).

Fatalism was found to be associated with depression, but socio-demographic factors explained more variability in depression at 6 weeks and 12 weeks. Further studies to identify other determinants of postoperative depression are warranted. The results suggest that pre-operative interventions to limit subsequent depression should be explored.

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Bachelors
Nursing
Nursing

Background Worldwide, the number of patients suffering from surgical complications account for a significant burden on healthcare systems. Myocardial injury after non-cardiac surgery (MINS) is a new entity that has recently been identified as an independent risk factor associated with 30-day all-cause mortality. The risk of death increases approximately 10 fold following MINS in the perioperative period. Diagnosing myocardial injury in nonsurgical patients often relies on specific symptomatology and clinical findings combined with special investigations. However, in surgical patients, more than 80% of patients with postoperative myocardial injury will be asymptomatic, and hence the majority of diagnoses will be missed. Studies identifying the prevalence and risk factors for MINS have been conducted in countries with a different surgical population to South Africa. The primary outcome of this study was to investigate the prevalence of MINS after non-cardiac, elective, elevated risk surgery in South Africa. Methods Patients undergoing elevated risk, elective, non-cardiac surgery ≥ 45 years of age were enrolled via convenience sampling. The new 5th generation, high sensitivity cardiac troponin T (hscTnT) blood test was used to identify MINS. Blood samples were taken between 24 to 72 hours after surgery. Exclusion criteria included patients with known renal disease, a recent cardiac event, pulmonary embolism or sepsis. Results A total of 244 patients were included in the study. The prevalence of MINS was 4.9% (95% CI 2.2-7.6) which was not significantly different (p=0.078) to reports from international prospective observational studies. Conclusion Elective, elevated risk surgical patients in South Africa have a similar incidence of MINS when compared to patients from international studies. As the risk profile of South African patients is significantly lower than other similar international observational studies, it is possible that the prevalence of MINS is more common in South Africa, when patients are adjusted for cardiovascular risk profile. The burden of MINS on public health morbidity is therefore likely to be proportionally more in South Africa when compared to international reports. This may suggest that the calibration of international cardiovascular risk prediction models is incorrect for South African patients, or there are confounding comorbidities which should be included in South African cardiovascular risk prediction models. Larger studies are required to confirm this hypothesis however, and should also aim to address the need for appropriate cardiovascular risk predicting models in South Africa, to ensure timeous identification of patients at risk of MINS.

The outcome of 121 children who underwent palliative cardiac surgery at the Red Cross War Memorial Children's Hospital over a 5 year period, 1980 1984, was retrospectively examined. 79 children had systemic artery to pulmonary artery shunt operations (SPS), 40 had pulmonary artery bands (PAB) and 2 had surgical septectomies. SPS was most often done for children with Tetralogy of Fallot (TOF, 26 cases) or complex univentricular hearts with right ventricular outflow tract obstruction (27 cases). PAB was done chiefly for ventricular septa! defects, alone (VSD, 8 cases) or with coarctation of the aorta (9 cases). Children were referred from a wide area with 63 cases being referred from other major centres and foreign countries. Overall, 36 children died (30 % mortality): 5 died at surgery, 6 within 48 hours of surgery, a further 5 within 31 days; and 20 died after 31 days. SPS and PAB had the same early mortality rates ( 13 % ) • SPS had higher late and overall mortality rates (20 and 33 %) than PAB (10 and 23 %). Age at operation was found to be the most significant determinant of the overall mortality rate: children less than six months had a mortality of 42 % and those over 6 months, 13 % • The children were grouped into those with lesions which were probably correctable and those that were unlikely to be so, based on diagnosis and age at surgery: those with correctable lesions had a lower overall mortality (22 %) than those with uncorrectable lesions (43 %). Where the surgery was performed as an emergency, there was a higher overall and early mortality (55 and 35 respectively), compared to those operations which were performed electively ( 25 and 9 % ) • The presence of other medical conditions, for example congenital abnormalities and infections, was also a determinant of death (44 % mortality if other medical condition present, 26 % if absent). sex, population group, home address and type of surgery performed did not significantly affect mortality when examined by multivariate analysis. Using routine methods of follow up, it was initially thought that 17 % of all patients (22 % of survivors) were lost to follow up. An important determinant of this was the referral centre. 31 % of cases from other major centres and 20 % of foreign cases were lost, as compared to 8 % of cases from smaller towns near Cape Town and 2 % of children from Cape Town. Population group (35 % Blacks, 14 % Coloureds and 7 % Whites were lost), and palliative operation (23 % SPS, and 5 % PAB lost) were also significant determinants. It was possible to trace 12 of the 20 children who were thought to be lost to follow. 8 had died, 3 were still awaiting correction and 1 was traced and received corrective surgery. The records of the children who underwent cardiac surgery in 1987 were also analysed. There was no difference in the demographic characteristics of either group, and the early mortality was the same. This study shows that the outcome after palliative cardiac surgery is poor, with a high mortality rate and children often being lost to follow up. The decision to palliate rather than to correct a congenital heart defect must be made after balancing these risks with those of early correction for the particular surgical team. Should palliative surgery be undertaken, careful follow up is essential to ensure that complications of palliation do not set in and that corrective surgery is done at the optimal time.

This thesis evaluates three most important etiological factors for organ injury namely, intravenous fluid, cardiopulmonary bypass (CPB) and blood transfusion, and considers their effects on endothelial dysfunction. This thesis evaluates 1. The safety of current fluid therapy, 2. The effects of novel versus established volume expanders on endothelial function and Acute Kidney Injury (AKI), 3. The effect of Sildenafil on renal glycocalyx in post-CPB AKI and 4. The effect of standard and modified red cell transfusions on lung and kidney injury. Using a systematic assessment of randomised controlled trials comparing colloids and crystalloids, we found that Hydroxyethylstarches are associated with increased risk of mortality and AKI. On the contrary, there was no evidence that Gelatins, Dextrans and Crystalloids were associated with increased harm. We evaluated the supremacy of novel AQIX RS-1® for intravenous resuscitation in a swine model of general anesthesia but failed to show its superiority as an endothelial and organ protective agent compared to Hartmann’s solution. We characterized that CPB mediated AKI is associated with modifications of Glycosaminoglycans and core protein components of Glycocalyx, but also that CPB induces detrimental changes in endothelial surface markers; vWF, Thrombomodulin, VE-Cadherin. These structural modifications caused direct reduction in Nitric Oxide bioavailability, renal artery vasomotor function and invoked AKI in swine. Post CPB-AKI was prevented by restoration of depleted NO bioavailability using Sildenafil Citrate without restoration of glomerular endothelial membrane (GEM) constituents. We explored the pathogenesis of Transfusion Related Acute Lung Injury (TRALI) and implicate alterations in red cell metabolomics; endothelial dysfunction, inflammation, microparticles and labile Iron and use a translational porcine model of TRALI to test red cell Rejuvenation coupled with red cell washing as a promising therapy. The work in this thesis has supported or generated ideas of novel pragmatic randomised clinical trials that seek to make direct difference in outcomes after cardiac surgery.

Technological advances over the past four decades have decreased the major complications or mortality in cardiac surgery. However, a significant number of patients suffer from adverse neurological and cognitive outcomes which, in turn, remain an important cause of postoperative morbidity and are responsible for an increasing proportion of perioperative deaths. Adverse neurological and cognitive outcomes after cardiac surgery are the result of multiple preoperative and/or intraoperative factors. While demographic, biomedical, and psychological disorders (e.g., anxiety and depression) represent preoperative variables associated with postoperative adverse outcomes, intraoperative cerebral hypoperfusion, microembolization and neuroinflammation that are related to cardiopulmonary bypass also represent a major cause of impairment after surgery. Despite a growing interest in adverse psychological outcomes after cardiac surgery, the psychobiological mechanisms underlying postoperative cognitive decline have to be investigated yet. In this dissertation, four studies are described, that were meant to examine cognitive decline and depression after cardiac surgery and some psychobiological mechanisms underlying the afore-mentioned phenomena. The main aim of Experiment I was to provide further evidence about the preoperative relationships among anxiety, depression, cognitive dysfunctions and risk-stratification scores, namely the Stroke Index and European System for Cardiac Operative Risk Evaluation, in patients undergoing cardiac surgery. It was found that both the risk-stratification scores showed significant correlations with cognitive performance, whereas only the European System for Cardiac Operative Risk Evaluation was significantly associated also with anxiety and depression. The main goal of Experiment II and III was to investigate the hemodynamic cerebral factors underlying cognitive decline after cardiac surgery. Experiment II was designed to examine whether cerebral hypoperfusion may represent a predictor of cognitive decline in patients undergone cardiac surgery after controlling for common demographic and biomedical risk factors. Experiment II showed that hypoperfusion in the left middle cerebral artery selectively predicted the incidence of cognitive decline after surgery, whereas blood flow velocity in the right middle cerebral artery was unrelated to postoperative cognitive decline. Hence, cardiac surgery patients with reduced left cerebral blood flow velocity preoperatively are at greater risk for postoperative cognitive decline. Left cerebral hypoperfusion may also represent an independent predictor of cognitive decline in cardiac surgery patients. Experiment III was designed to determine the effects of lateralization and type of microembolization on postoperative cognitive decline in patients who had undergone heart valve surgery. Experiment III showed that microembolization in the left middle cerebral artery significantly correlated with early and late (i.e., 3-month follow-up) postoperative cognitive decline, while microembolization in the right middle cerebral artery was unrelated to early and late cognitive decline. Moreover, an association between solid microemboli with early but not late postoperative cognitive decline was noted. In contrast, gaseous microembolization was related to both early and late cognitive decline. Given the relevant role played by depression as a risk factor for postoperative adverse clinical and cognitive outcomes, the main aim of the Experiment IV was to examine, postoperatively, whether electroencephalographic activity could reflect the influence of depression during an emotional imagery task requiring the subject being involved in a cognitive task (retrieval and imagery), which is emotionally laden. There was no difference between groups in resting electroencephalographic activity, whereas patients with depression showed a significant reduced frontal theta power during the emotional imagery task compared to those without depression. Also, a significant correlation was selectively found between frontal theta power and emotional reappraisal. Taken together these experiments provide a better understanding of the psychological and physiological mechanisms underlying postoperative cognitive decline and depression in cardiac surgery patients. In conclusion, the present thesis suggests the need for including preoperative and postoperative evaluation of cognitive and affective status as well as objective hemodynamic and/or electroencephalographic measures to accurately predict and/or treat patient’s dysfunctional psychological outcomes after cardiac surgery
Le innovazioni tecnologiche conseguite nella seconda metà del XX secolo hanno ridotto le complicazioni maggiori e la mortalità nei pazienti sottoposti a cardiochirurgia. Nonostante gli evidenti benefici clinici nella pratica medica, un numero significativo di pazienti presenta disfunzioni neurologiche e/o psicologiche nel periodo postoperatorio che, a loro volta, sono responsabili per l’incremento della mortalità perioperatoria e della morbidità postoperatoria. Tali disfunzioni neurologiche e cognitive in seguito a cardiochirurgia sono il risultato di diversi fattori preoperatori e/o intraoperatori. Mentre le variabili demografiche, biomediche e psicologiche (tra cui ansia e depressione) rappresentano importati fattori preoperatori associati allo stato di salute postoperatorio, l’ipoperfusione cerebrale, l’embolizzazione e/o i processi neuroinfiammatori associati al bypass cardiopolmonare durante la chirurgia rappresentano fattori di rischio intraoperatori per le disfunzioni neurologiche e cognitive postoperatorie. Sebbene vi sia un sempre crescente interesse nello studio delle disfunzioni psicologiche in seguito a cardiochirurgia, i meccanismi psicobiologici sottostanti il declino cognitivo postoperatorio devono ancora essere indagati. Perciò, nella presente tesi sono descritti quattro studi che, per prima cosa, avevano lo scopo di indagare l’entità del declino cognitivo e della depressione in seguito a cardiochirurgia e, in secondo luogo, miravano ad identificare alcuni fattori di stampo psicobiologico coinvolti nel declino cognitivo e depressione postoperatori. L’Esperimento I mirava, come scopo principale, a fornire nuove evidenze circa la relazione, nel periodo preoperatorio, tra ansia, depressione, disfunzioni cognitive e punteggi di rischio biomedico (lo Stroke Index e l’European System for Cardiac Operative Risk Evaluation) in pazienti in attesa di intervento cardiochirurgico. I risultati del presente studio hanno indicato che, mentre entrambi i punteggi di rischio biomedico erano associati allo stato cognitivo preoperatorio dei pazienti cardiochirurgici, solo l’European System for Cardiac Operative Risk Evaluation teneva in considerazione anche i fattori di rischio associati all’ansia e depressione. Lo scopo principale degli Esperimenti II e III era indagare l’associazione fra fattori emodinamici cerebrali perioperatori e disfunzioni cognitive in seguito a cardiochirurgia. L’Esperimento II è stato disegnato per indagare se l’ipoperfusione cerebrale preoperatoria potesse essere un predittore di declino cognitivo postoperatorio nei pazienti sottoposti a cardiochirurgia, anche dopo aver controllato per i più comuni fattori di rischio demografici e biomedici. L’Esperimento II ha mostrato che l’incidenza del declino cognitivo si associava selettivamente all’ipoperfusione nell’arteria cerebrale media sinistra, mentre la velocità di flusso ematico nell’arteria cerebrale media destra non correlava con il declino cognitivo postoperatorio. L’ipoperfusione cerebrale sinistra, quindi, sembra rappresentare un fattore di rischio indipendente per il declino cognitivo in pazienti sottoposti a cardiochirurgia. L’Esperimento III è stato disegnato per determinare il ruolo dell’asimmetria e della natura della microembolizzazione intraoperatoria sul declino cognitivo postoperatorio in pazienti sottoposti a chirurgia valvolare. L’Esperimento III ha mostrato che la microembolizzazione intraoperatoria nell’arteria cerebrale media sinistra correlava significativamente sia con il declino cognitivo nell’immediato postoperatorio (alle dimissioni) che a distanza nel tempo (a 3 mesi dall’intervento chirurgico), mentre gli eventi embolici nell’arteria cerebrale media destra non erano associati né al declino cognitivo immediato né a distanza nel tempo. Inoltre, i microemboli solidi correlavano significativamente con il declino cognitivo immediato ma non al follow-up di 3 mesi. Al contrario, è stata riscontrata un’associazione significativa tra gli eventi microembolici gassosi ed il declino cognitivo immediato e a 3 mesi di distanza dall’intervento chirurgico. Dato il ruolo rilevante giocato dalla depressione come fattore di rischio per le disfunzioni cognitive postoperatorie, lo scopo principale dell’Esperimento IV è stato quello di indagare, nel periodo postoperatorio, se e come la depressione potesse influenzare l’attività elettroencefalografica durante un compito di imagery emozionale, il quale, a sua volta, implica sia un’elaborazione di tipo cognitivo che emozionale. Sebbene nessuna differenza tra i gruppi sia stata riscontrata nell’attività elettroencefalografica a riposo, rispetto ai controlli non depressi, si osservava nei pazienti depressi una ridotta attività theta frontale durante il compito di imagery emozionale. Inoltre, una ridotta ampiezza della theta frontale si associava selettivamente a disregolazione emozionale (ridotta capacità di reappraisal). Questi esperimenti, considerati nel loro insieme, forniscono una migliore e più approfondita comprensione dei meccanismi psicologici e fisiologici sottostanti il fenomeno del declino cognitivo e depressione postoperatori in pazienti cardiochirurgici. In conclusione, la presente tesi suggerisce la possibilità di includere sia una valutazione cognitiva e affettiva pre e postoperatoria che misure emodinamiche e/o elettroencefalografiche oggettive in grado di predire e/o facilitare il trattamento delle disfunzioni psicologiche postoperatorie nei pazienti sottoposti a cardiochirurgia