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The role of brain natriuretic peptide in prognostication and reclassification of risk in patients undergoing vascular surgery*
SummaryThe aim of this study was to determine whether measurement of pre‐operative brain natriuretic peptide can significantly improve risk stratification of vascular surgical patients. The study endpoint was postoperative raised troponins. Net reclassification improvement was determined for risk categories based on the Revised Cardiac Risk Index. Two reclassifications were conducted based on either the optimal discriminatory point or brain natriuretic peptide tertiles. Two hundred and sixty‐seven patients were studied of whom 36 (13.5%) had raised postoperative troponin. The Revised Cardiac Risk Index score and the pre‐operative brain natriuretic peptide were independent predictors of postoperative troponin elevation (p = 0.02 and p = 0.001, respectively). Reclassification based on the optimal discriminatory point significantly improved risk stratification (net reclassification improvement 38.3% (95% CI 9.3–67.3%), p = 0.01 for the entire cohort and 70.3% (95% CI 27.1–113.6%), p = 0.002 for intermediate risk patients). The brain natriuretic peptide tertiles only improved stratification of intermediate risk patients (net reclassification improvement 50.0% (95% CI 16.7–83.3%), p = 0.01). We have shown that measurement of pre‐operative brain natriuretic peptide is relevant in the context of risk assessment in this cohort of patients.
Correlation between cerebral tissue and central venous oxygen saturation during off-pump coronary bypass graft surgery
We compared simultaneous regional cerebral oxygen saturation and central venous oxygen saturation at different time periods in 20 adult patients (median age, 57.9; range, 35 to 76 years) undergoing off-pump coronary artery bypass (OPCAB) graft surgery (n= 20). Mean arterial pressure (MAP), partial pressure of carbon dioxide (PcvCO2), heart rate, haematocrit (Hct), lactate and patient oxygen saturation (SpO2) were also recorded as a secondary analysis to determine independent predictors of cerebral desaturation and interactions between predictors. The cross-sectional analysis performed at each time point showed several significant moderate to strong positive correlations between central venous oxygen saturation and both right and left cerebral oxygen saturations; however, right cerebral saturations correlated better with central venous saturations than left cerebral saturation. Partial pressure of carbon dioxide (PcvCO2) was identified as a major predictor of cerebral saturation 0.59 ( p < 0.001). Central venous saturation can be used as a surrogate measure of cerebral oxygen saturation during OPCAB surgery.
The pathophysiology of peri‐operative myocardial infarction
SummaryIt is generally believed that plaque rupture and myocardial oxygen supply‐demand imbalance contribute approximately equally to the burden of peri‐operative myocardial infarction. This review critically analyses data of post‐mortem, pre‐operative coronary angiography, troponin surveillance, other pre‐operative non‐invasive investigations, and peri‐operative haemodynamic predictors of myocardial ischaemia and/or myocardial infarction. The current evidence suggests that myocardial oxygen supply‐demand imbalance predominates in the early postoperative period. It is likely that flow stagnation and thrombus formation is an important pathway in the development of a peri‐operative myocardial infarction, in addition to the more commonly recognised role of peri‐operative tachycardia. Research and therapeutic interventions should be focused on the prediction and therapy of flow stagnation and thrombus formation. Plaque rupture appears to be a more random event, distributed over the entire peri‐operative admission.
A meta‐analysis of the prospective randomised trials of coronary revascularisation before noncardiac vascular surgery with attention to the type of coronary revascularisation performed
SummaryProspective randomised trials of coronary revascularisation prior to noncardiac surgery have shown no survival benefit following noncardiac surgery. However, these studies have not differentiated the outcomes associated with coronary artery bypass grafting (CABG) and percutaneous coronary interventions. We performed a meta‐analysis of the randomised controlled trials of pre‐operative coronary revascularisation for noncardiac surgery, extracting data for 30 day and long term all‐cause mortality and myocardial infarction (MI) following revascularisation, according to the type of revascularisation performed. Pre‐operative percutaneous coronary intervention was associated with significantly increased 30 day MI and composite death and MI. Pre‐operative CABG was associated with a significantly improved long term composite outcome of death and MI compared to percutaneous coronary interventions. The adverse effect of percutaneous coronary interventions on both short and long term outcomes in vascular surgical patients should be taken into consideration when interpreting these trials. CABG may improve long term outcomes in vascular surgical patients. The indications for and timing of CABG in vascular surgical patients needs further research.
Investigation of predictors of increased creatine kinase levels following vascular surgery and the association with peri-operative statin therapy.
UnlabelledAlthough peri-operative statin administration is likely to be cardioprotective, there remains a concern about the risk of rhabdomyolysis and associated renal failure following statin administration in the peri-operative period. The aim of this study was to determine independent predictors of creatine kinase (CK) elevation following vascular surgery.DesignA retrospective cohort study was conducted. A multivariate analysis using binary logistic regression was conducted of clinical, surgical and laboratory factors which may be associated with a CK exceeding five times the upper limit of normal (ULN).ResultsFour independent predictors associated with a CK > 5 ULN were identified. Statin therapy was protective [odds ratio (OR) 0.096, 95% confidence interval (CI) 0.014-0.68, p = 0.019], and a serum creatinine > 180 micromol*l(-1), positive serum troponins and embolectomy and/or fasciotomy were associated with CK elevation (OR 3.32, 95% CI: 1.03-10.7, p = 0.04; OR 5.84, 95% CI: 1.52-22.4, p = 0.01; OR 5.62, 95% CI: 1.14-27.8, p = 0.03 respectively). Statin therapy was associated with decreased mortality (OR 0.26, 95% CI: 0.08-0.86, p = 0.028).ConclusionIt may be preferable to continue statin therapy in vascular surgical patients even when CK is elevated, as this may decrease mortality if the CK elevation is in the presence of pre-existing renal dysfunction, peri-operative cardiac events or following embolectomy or fasciotomy. Further investigation is required to confirm this observation.
A meta‐analysis of the utility of C‐reactive protein in predicting early, intermediate‐term and long term mortality and major adverse cardiac events in vascular surgical patients
SummaryWe conducted a meta‐analysis of the utility of pre‐operative C reactive protein (CRP) in predicting early (< 30 days), intermediate (30–180 days) and long term (> 180 days) mortality and major adverse cardiac events (MACE; cardiac mortality and nonfatal myocardial infarction (MI) combined) following vascular surgery. Of 291 studies identified, ten prospective patient cohorts were identified. A pre‐operative CRP > 3 mg.l−1 was not associated with 30‐day all‐cause mortality, cardiac mortality, nonfatal myocardial infarction or MACE. Intermediate‐term all‐cause mortality, cardiac death and MACE showed a trend to a worse outcome (odds ratio (OR) 9.07, 95% confidence interval (CI) 0.86–96.28, p = 0.07; OR 8.71, 95% CI 0.5–153.1, p = 0.14 and OR 2.81, 95% CI 0.78–5.18, p = 0.15 respectively). Long term all cause mortality (OR 2.40, 95% CI 1.15–5.02, p = 0.02), cardiac death (OR 5.66, 95% CI 1.71–18.73, p = 0.005) and MACE (OR 2.76, 95% CI 1.38–5.55, p = 0.004) were significantly increased.
A meta‐analysis of the utility of pre‐operative brain natriuretic peptide in predicting early and intermediate‐term mortality and major adverse cardiac events in vascular surgical patients
SummaryWe conducted a meta‐analysis of the utility of pre‐operative B‐type natriuretic peptide (BNP) and N‐terminal‐pro B‐type natriuretic peptide in predicting early (< 30 days) and intermediate (< 180 days) term mortality and major adverse cardiac events (cardiac death and nonfatal myocardial infarction) in patients following vascular surgery. A Pubmed Central and EMBASE search was conducted up to January 2008. Of 81 studies identified, seven prospective observational studies were included in the meta‐analysis representing five patient cohorts: early outcomes (504 patients) and intermediate‐term outcomes (623 patients). A B‐type natriuretic peptide or N‐terminal‐pro B‐type natriuretic peptide above the optimal discriminatory threshold determined by receiver operating characteristic curve analysis was associated with 30‐day cardiac death (OR 7.6, 95% CI 1.33–43.4, p = 0.02), nonfatal myocardial infarction (OR 6.24, 95% CI 1.82–21.4, p = 0.004) and major adverse cardiac events (OR 17.37, 95% CI 3.31–91.15, p = 0.0007), and intermediate‐term, all‐cause mortality (OR 3.1, 95% CI 1.85–5.2, p < 0.0001), nonfatal myocardial infarction (OR 2.95, 95% CI 1.17–7.46, p = 0.02) and major adverse cardiac events (OR 3.31, 95% CI 2.1–5.24, p < 0.00001). B‐type natriuretic peptide and N‐terminal‐pro B‐type natriuretic peptide are potentially useful pre‐operative prognostic tests in vascular surgical patients.
Validation of a model to predict all-cause in-hospital mortality in vascular surgical patients.
ObjectiveTo develop and validate a pre- and postoperative model of all-cause in-hospital mortality in South African vascular surgical patients.MethodsWe carried out a retrospective cohort study. A multivariate analysis using binary logistic regression was conducted on a derivation cohort using clinical, physiological and surgical data. Interaction and colinearity between covariates were investigated. The models were validated using the Homer-Lemeshow goodness-of-fit test.ResultsIndependent predictors of in-hospital mortality in the pre-operative model were: (1) age (per one-year increase) [odds ratio (OR) 1.03, 95% confidence interval (CI) 1.0-1.06), (2) creatinine > 180 micromol.l(-1) (OR 6.43, 95% CI: 3.482-11.86), (3) chronic beta-blocker therapy (OR 2.48, 95% CI: 1.38-4.48), and (4) absence of chronic statin therapy (OR 2.81, 95% CI: 1.15-6.83). Independent predictors of mortality in the postoperative model were: (1) age (per one-year increase) (OR 1.05, 95% CI: 1.02-1.09), (2) creatinine > 180 micromol.l(-1) (OR 5.08, 95% CI: 2.50-10.31), (3) surgery out of hours without statin therapy (OR 8.27, 95% CI: 3.36-20.38), (4) mean daily postoperative heart rate (HR) (OR 1.02, 95% CI: 1.0-1.04), (5) mean daily postoperative HR in the presence of a mean daily systolic blood pressure of less than 100 beats per minute or above 179 mmHg (OR 1.02, 95% CI: 1.01-1.03) and (6) mean daily postoperative HR associated with withdrawal of chronic beta-blockade (OR 1.02, 95% CI: 1.01-1.03). Both models were validated.ConclusionThe pre-operative model may predict the risk of in-hospital mortality associated with vascular surgery. The postoperative model may identify patients whose risk increases as a result of surgical or physiological factors.
Heart Rate and Outcome in Patients with Cardiovascular Disease Undergoing Major Noncardiac Surgery
There is an increasing awareness that an elevated resting heart rate is associated with increased all-cause mortality in the general population and that this may be an independent coronary risk factor. This review was undertaken to determine whether heart rate is predictive of increased mortality and major morbidity in noncardiac surgical patients and whether heart rate manipulation improves perioperative outcome. A search of Medline from 1966 until October 2007 was conducted using the terms “heart rate “, “surgery”, “cardiac “, “morbidity”, “mortality” and “perioperative”. The main findings were that an elevated perioperative heart rate, an absolute increase in heart rate and heart rate lability are independent predictors of both short- and long-term adverse outcomes in patients at cardiovascular risk undergoing major noncardiac surgery. Although prospective nonrandomised and retrospective data suggest heart rate control improves perioperative outcome, there is conflicting evidence from randomised trials that perioperative heart rate control improves outcome. This may be because drug-associated bradycardia influences mortality in the perioperative period. Further studies reporting the absolute heart rate, the absolute change of heart rate and the time period of the observations are needed to identify ‘early warning systems’, which may allow earlier triage and improved outcome. Enthusiasm for this approach must be tempered by the appreciation that a J-shaped relationship probably exists between heart rate and morbidity, particularly following bradycardic therapy. Therefore, any bradycardic manipulation of heart rate in the perioperative period must be accompanied by simultaneous attention to other physiological variables associated with increased morbidity and mortality.
A peri‐operative statin update for non‐cardiac surgery. Part II: Statin therapy for vascular surgery and peri‐operative statin trial design
SummaryThis is the second of two review articles evaluating peri‐operative statin therapy. In surgical patients, the utility of peri‐operative statin therapy is strongly suggested by retrospective studies, although it is probably overestimated, as important confounding factors have not been controlled for and hence the literature is considered to be currently inconclusive.This review examines the potential mechanisms and indications for peri‐operative statin protection, the efficacy of acute peri‐operative beta‐blockade in addition to statin therapy, the effect of peri‐operative statin therapy withdrawal and the implications of comorbidities associated with peri‐operative cardiovascular risk on statin therapy. Recommendations concerning appropriate dosing, duration, therapeutic targets and necessary investigations when prescribing peri‐operative statins are made. Peri‐operative study design recommendations are suggested, so that future meta‐analyses may be more informative. Recommendations are made regarding retrospective reporting of statin studies to minimise the bias inherent in a number of the current retrospective studies on this subject.