Predictors of Peri-Operative Risk Acceptance by South African Vascular Surgery Patients at a Tertiary Level Hospital

Background: Vascular surgical patients have an elevated cardiac risk following non-cardiac surgery. The decision whether to proceed with surgery is multidimensional. Patients must balance the considerations in favour of surgery with those favouring conservative treatment, which requires weighing peri-operative risk against morbidity associated with non-surgical treatment.Methods: The aim of this prospective correlational study was to determine the proportional contributions of (i) pain, (ii) impulsivity, (iii) patients’ perception of the benefits of surgery, (iv) patients’ perception of peri-operative risk and (v) the predicted peri-operative risk on acceptance of peri-operative risk by vascular surgical patients. Sixty patients were prospectively recruited by convenience sampling from the Inkosi Albert Luthuli Central Hospital vascular surgery clinic between April 2014 and June 2014. Written informed consent was obtained. Patients completed a questionnaire which documented demographics, pain assessment, impulsivity screen (Barratt Impulsiveness Scale 11), patients’ perception of surgery, predicted peri-operative risk (South African Vascular Surgical Cardiac Risk Index) and acceptance of peri-operative risk. Data were analysed using descriptive statistics and linear regression (SPSS version 22).Results: The patients’ perception of the benefits of surgery (β 0.36, 95% CI 0.14–0.70, p = 0.005) was the only predictor of peri-operative risk acceptance. The associations between the other potential predictors and the outcome were insignificant.Conclusion: The perceived benefit of surgery was the most important predictor of acceptance of peri-operative risk in this cohort.Keywords: Pain, Peri-operative Risk, Shared Decision-making, Vascular Surger

The pharmaco-economics of peri-operative beta-blocker and statin therapy in South Africa

We conducted a pharmaco-economic analysis of the prospective  peri-operative  studies of beta-blocker and statin administration for major  elective non-cardiac surgery, using the Discovery Health claims costs for 2004. This analysis shows that acute peri-operative beta-blockade and statin  therapy could result in a cost saving through a reduction in major   perioperative cardiovascular complications in patients with an expected  peri-operative major cardiovascular complication rate exceeding 10% following elective major non-cardiac surgery. The validity of these findings is dependent on whether the incidence of cardiovascular complications following major  noncardiac surgery reported in the international literature is found to be similar in South Africa

Peri‐operative cardiac arrest in children as reported to the 7th National Audit Project of the Royal College of Anaesthetists

The 7th National Audit Project of the Royal College of Anaesthetists studied peri‐operative cardiac arrest. An activity survey estimated UK paediatric anaesthesia annual caseload as 390,000 cases, 14% of the UK total. Paediatric peri‐operative cardiac arrests accounted for 104 (12%) reports giving an incidence of 3 in 10,000 anaesthetics (95%CI 2.2–3.3 per 10,000). The incidence of peri‐operative cardiac arrest was highest in neonates (27, 26%), infants (36, 35%) and children with congenital heart disease (44, 42%) and most reports were from tertiary centres (88, 85%). Frequent precipitants of cardiac arrest in non‐cardiac surgery included: severe hypoxaemia (20, 22%); bradycardia (10, 11%); and major haemorrhage (9, 8%). Cardiac tamponade and isolated severe hypotension featured prominently as causes of cardiac arrest in children undergoing cardiac surgery or cardiological procedures. Themes identified at review included: inappropriate choices and doses of anaesthetic drugs for intravenous induction; bradycardias associated with high concentrations of volatile anaesthetic agent or airway manipulation; use of atropine in the place of adrenaline; and inadequate monitoring. Overall quality of care was judged by the panel to be good in 64 (62%) cases, which compares favourably with adults (371, 52%). The study provides insight into paediatric anaesthetic practice, complications and peri‐operative cardiac arrest

Utility of B-type natriuretic peptide in predicting medium-term mortality in patients undergoing major non-cardiac surgery

We assessed the ability of pre-operative B-type natriuretic peptide (BNP) levels to predict medium-term mortality in patients undergoing major noncardiac surgery. During a median 654 days follow-up 33 patients from a total cohort of 204 patients (16%) died. The optimal cut-off in this cohort, determined using a receiver operating characteristic curve, was >35pg.mL-1. This was associated with a 3.47-fold increase in the hazard of death (p=0.001) and had a sensitivity of 70% and a specificity of 68% for this outcome. These findings extend recent work demonstrating that BNP levels obtained before major noncardiac surgery can be used to predict peri-operative morbidity, and indicate that they also forecast medium-term mortality.This work was supported by a grant from TENOVUS Scotland. The Health Services Research Unit is core-funded by the Chief Scientists Office of the Scottish Executive Health Department.Peer reviewedAuthor versio

Peri-operative cardiac morbidity: prediction, prevention and the novel role of B-type natriuretic peptide

Cardiovascular disease is the leading cause of death in surgical patients and because of this a number of strategies have been utilised to attempt to predict the cardiac risk of surgery. Theoretically, accurate pre-operative risk stratification would allow patients at low risk to have their surgery expedited efficiently, whilst those at higher risk could have a change made to their treatment plan such as peri-operative cardiac optimisation or in some cases, modification of the operative procedure. Despite this rationale, no guidelines currently exist in the United Kingdom for the management of the surgical patient at high cardiac risk. This may partly reflect the limited methods of risk stratification currently available. Clinical scoring systems are simple and inexpensive but limited by their predictive value. Trans-thoracic echocardiography provides prognostic information but is inconsistent, adding little to clinical information alone. The most accurate methods of pre-operative cardiac risk prediction at the present time are dobutamine stress echocardiography and dipyridamole thallium scanning. However they are expensive, time consuming and have shown poor positive predictive ability, even in high risk cohorts. Few studies have studied the usefulness of biochemical markers in the prediction of post-operative cardiac events. In particular, no information was available in the literature regarding the role of B-type natriuretic peptide (BNP) in the prediction of cardiac events in non-cardiac surgical patients; despite the fact that its measurement has been shown to be an important prognostic tool in both non-surgical and cardiac surgical cohorts. In this thesis the aim was to determine whether pre-operative BNP concentration related to cardiac outcome following non-cardiac surgery; and also to determine whether measurement of other markers such as C- reactive protein (CRP) and cardiac troponin I (CTnI) would be of benefit in pre-operative cardiac risk stratification. To assess the effectiveness of plasma BNP measurement in the prediction of peri-operative cardiac morbidity a pilot study of 41 patients undergoing vascular surgery was conducted. To ensure that any post-operative rise in CTnI was due to operative stress, this was measured pre-operatively along with CRP. Median pre-operative BNP concentration was significantly higher in patients who suffered a post-operative cardiac event (cardiac death, non-fatal myocardial infarction (MI)) than in those who did not (210 (165-380) pg/ml vs. 34.5 (14-70) pg/ml, p<0.001). On the basis of these results a single-centre, prospective, observational cohort study was performed of all patients undergoing non-cardiac surgery. Of the 149 patients recruited to this study, 15 had a cardiac event. The median BNP in those patients having a cardiac event was more than ten-times higher than in those who did not (351 (127-1034) vs. 30.5 pg/ml (11-79.5), p<0.001). A BNP concentration of 108.5pg/ml was the best performing cut-off value having a sensitivity and a specificity of 87%. Although CTnI had originally been measured to ensure that any post-operative rise was due to operative stress, 3 patients had a pre-operative elevation all of whom underwent lower extremity amputation. The amputation group, and in particular those patients who had a raised pre-operative cTnI were therefore analysed further. Amputation patients in general had a high cardiac event rate (23%); however the outcome in those patients who had a raised pre-operative cTnI was particularly poor with 2 suffering a cardiac death post-operatively and one suffering a non-fatal MI. A pre-operative rise in CTnI was the only significant single predictor of peri-operative cardiac events in patients undergoing amputation (p= 0.009). Pre-operative CRP concentration was measured routinely in vascular patients. The concentration in those who had a cardiac event was significantly higher than those who did not (69 (0-260) vs. 12 (0-285), (p=0.003). The cardiac event rate rose with each logarithmic increment in CRP concentration (0-10mg/l (5.7%); 11-100mg/l (22.4%), >100mg/l (55.6%) (p=0.002). Measurement of CRP was of most potential benefit in patients undergoing aortic aneurysm surgery. In conclusion, this thesis has shown that pre-operative measurement of biochemical markers (BNP, CTnI, and CRP) can allow accurate peri-operative risk stratification. BNP concentration in particular was a sensitive and specific predictor of cardiac outcome. Careful case selection using a combination of clinical assessment and the results of these markers may lead to a reduction in the cardiac event rate

Guidelines for pre-operative cardiac risk assessment and perioperative cardiac management in non-cardiac surgery : the Task Force for Preoperative Cardiac Risk Assessment and Perioperative Cardiac Management in Non-cardiac Surgery of the European Society of Cardiology (ESC) and endorsed by the European Society of Anaesthesiology (ESA)

Non-cardiac surgery; Pre-operative cardiac risk assessment; Pre-operative cardiac testing; Pre-operative coronary artery revascularization; Perioperative cardiac management; Renal disease; Pulmonary disease; Neurological disease; Anaesthesiology; Post-operative cardiac surveillanc

The utility of B-type natriuretic peptide in predicting postoperative cardiac events and mortality in patients undergoing major emergency non-cardiac surgery

B-type natriuretic peptide (BNP) levels predict cardiovascular risk in several settings. We hypothesized that they would identify individuals at increased risk of complications and mortality following major emergency non-cardiac surgery.Forty patients were studied with a primary end-point of a new post-operative cardiac event, and/or development of significant ECG changes, and/or cardiac death. The main secondary outcome was all cause mortality at 6 months. Preoperative BNP levels were higher in 11 patients who suffered a new postoperative cardiac event (p=0.001) and predicted this outcome with an area under the receiver operating characteristic curve of 0.85 (CI=0.72-0.98,p=0.001). A pre-operative BNP value >170pg.ml-1 has a sensitivity of 82% and a specificity of 79% for the primary end-point. In this small study, pre-operative BNP levels identify patients undergoing major emergency non-cardiac surgery who are at increased risk of early post-operative cardiac events. Larger studies are required to confirm these data.Peer reviewedPreprin

The effect of peri‐operative dexmedetomidine on the incidence of postoperative delirium in cardiac and non‐cardiac surgical patients: a randomised, double‐blind placebo‐controlled trial

Delirium occurs commonly following major non-cardiac and cardiac surgery and is associated with: postoperative mortality; postoperative neurocognitive dysfunction; increased length of hospital stay; and major postoperative complications and morbidity. The aim of this study was to investigate the effect of peri-operative administration of dexmedetomidine on the incidence of postoperative delirium in non-cardiac and cardiac surgical patients. In this randomised, double-blind placebo-controlled trial we included 63 patients aged >= 60 years undergoing major open abdominal surgery or coronary artery bypass graft surgery with cardiopulmonary bypass. The primary outcome was the incidence of postoperative delirium, as screened for with the Confusion Assessment Method. Delirium assessment was performed twice daily until postoperative day 5, at the time of discharge from hospital or until postoperative day 14. We found that dexmedetomidine was associated with a reduced incidence of postoperative delirium within the first 5 postoperative days, 43.8% vs. 17.9%, p = 0.038. Severity of delirium, screened with the Intensive Care Delirium Screening Checklist, was comparable in both groups, with a mean maximum score of 1.54 vs. 1.68, p = 0.767. No patients in the dexmedetomidine group died while five (15.6%) patients in the placebo group died, p = 0.029. For patients aged >= 60 years undergoing major cardiac or non-cardiac surgery, we conclude that the peri-operative administration of dexmedetomidine is associated with a lower incidence of postoperative delirium

The prediction of adverse outcomes following major non-cardiac surgery

The prediction of adverse outcomes following major non-cardiac surgery is complex. Clinical variables and risk factors, functional status, electrocardiography and non-invasive cardiac investigations can all be used to assess and stratify the risk of post-operative cardiac morbidity or mortality. Multiple factors can be combined into bed-side scoring systems. Increasingly, cardiac biomarkers such as b-type natriuretic peptide (BNP) have been shown to predict heart failure and mortality in non-surgical populations. In the studies in this thesis, I have investigated the incidence of peri-operative cardiac morbidity and mortality in patients undergoing major non-cardiac surgery and identified clinical variables that predicted adverse outcomes. I have tested the utility of BNP for prediction of cardiac complications. I have investigated the long-term survival of the patients in the cohort to identify predictors of reduced survival. I have examined the predictive value of the pre-operative 12-lead ECG for adverse outcomes. I have also studied the utility of a commonly used risk scoring system, the revised cardiac risk index (RCRI), for prediction of cardiac events. The study was a prospectively performed observational study of consecutive patients undergoing major surgery. The cohort consisted of patients undergoing aortic surgery (25.8%), lower limb bypass surgery (29.8%), amputation (25.2%) and laparotomy (20.0%). The patients underwent post-operative screening for myocardial infarction; consisting of serial ECG and troponin measurement. The end-points were major adverse cardiac event (MACE), defined as myocardial infarction or cardiac death and all-cause mortality. Long term follow-up was performed following discharge. Three hundred and forty-five patients were recruited to the trial. Forty-six patients (13.3%) suffered a peri-operative MACE and twenty-seven patients (7.8%) died in the post-operative period (six weeks). Independent predictors of peri-operative MACE were pre-operative anaemia, urgent surgery, a history of hypertension and age > 70 years. Pre-operative BNP was significantly higher in patients who subsequently went on to have a peri-operative MACE, compared with those who did not. An elevated BNP was an independent predictor of both MACE and peri-operative mortality on multivariate analysis. A low BNP was highly indicative of an uneventful post-operative period, with a negative predictive value of 96% for MACE and 95% for all-cause mortality. Traditional clinical markers of heart disease, such as past history of ischaemic heart disease, prior myocardial infarction, cerebro-vascular disease or history of cardiac failure provided no predictive utility for either MACE or mortality. The mortality rate at 1 year was 19.1%. The median follow-up period was 953 days (IQR 661-1216 days). Age > 70 years, diabetes, hypertension, renal impairment, a history of left ventricular failure, anaemia and urgent surgery were associated with reduced long-term survival. A BNP concentration of 87.5 pg/ml provided the best combined sensitivity and specificity for prediction of long-term mortality. Patients with an elevated BNP (>87.5 pg/ml) had a significantly reduced survival and BNP >87.5 pg/ml independently predicted reduced survival on Cox regression analysis. Urgent surgery and anaemia were also independent predictors of reduced long-term survival. An abnormal ECG was observed in 41% of patients recruited. An abnormal ECG was associated with an increased peri-operative MACE and mortality rate. Ventricular strain and prolonged QTc (>440ms) were ECG abnormalities that predicted MACE on multivariate analysis. Patients with an abnormal ECG, but no prior cardiac history, represent a high risk group that may benefit from optimisation. The studies in this thesis have identified that BNP, a simple pre-operative blood test, provides valuable information regarding the risk of both peri-operative morbidity and mortality, and long-term survival after major non-cardiac surgery. Improved risk stratification could allow targeted intervention and medical optimisation prior to surgery with the aim of modifying the risk of adverse outcomes