The Prognostic Value of Pre- and Post-Operative BNPs in Patients Undergoing Noncardiac Surgery
Editor's Note: Commentary based on Rodseth RN, Biccard BM, Le Manach Y, et al. The Prognostic Value of Pre-Operative and Post-Operative B-Type Natriuretic Peptides in Patients Undergoing Noncardiac Surgery. J Am Coll Cardiol 2014;63:170-80.
Natriuretic peptides (NP) are commonly used for diagnosis and prognosis in heart failure patients. Recently the NPs have been found to predict risk in other patient groups like acute coronary syndrome, atrial fibrillation, valvular heart disease and sepsis. It has been demonstrated that pre-operative NP measurement could be useful in predicting cardiovascular complications in patients undergoing non cardiac surgery. However, it is largely unknown if there is any incremental utility of assessing post-operative NP levels in this subset of patients, in addition to the pre-operative NP.
A meta-analysis was conducted including eighteen eligible prospective observational studies with 2,179 patients with pre and post-operative NP values for predicting mortality and non-fatal myocardial infarction at 30 and 180 days. A baseline model was created using revised cardiac risk index > 3, type of surgery (vascular versus non-vascular) and urgency of surgery. Pre and post-operative NPs were added to this model to compare the outcomes and net reclassification index was used to study any further improvement in risk stratification of using a post-operative NP.
Two thirds of the study population was male, mean age 68 years, mostly undergoing vascular surgery. Mortality at 30 and 180 days was 2.8% and 8.4%, respectively. 10.8% patients had died or experienced nonfatal MI at 30 days and 16.8% at 180 days. Event rate at 30 and 180 days was 21.8% and 37% respectively in patients with pre-operative NP level above the threshold versus 4.9% and 13.3% in those below the threshold. Adding post-operative NP to the baseline model including pre-operative NP significantly improved the net reclassification index at 30 (NRI 20%; p< 0.001) and 180 days (NRI 11%; p=0.003). Independent predictors of outcome at 30 and 180 days were elevated pre-operative NP (OR 1.9), post- operative NP (OR 3.7 and 2.2), and revised cardiac risk index > 3 (OR 2.3 and 2.2). Three quarters of patients were noted to have an increase in NP levels after surgery and the remaining demonstrated a decrease. Change in NP levels was not found to be predictive of outcomes.
Detailed systemic analysis of multiple studies reveals incremental utility of measuring post-operative natriuretic peptides to improve risk prediction of mortality and non-fatal MI in patients undergoing non cardiac surgery.
The authors demonstrate that there is utility of measuring NP levels post-operatively in addition to the pre-operative values in risk stratification of patients undergoing non cardiac surgery. However, the analysis does not take into account other post-operative variables which could potentially affect the specificity of NP in this setting, such as post-operative infection and degree of renal dysfunction. The million dollar question seems to be at what point do we intervene and would that intervention change outcome? Theoretically, an elevated pre-operative NP value could allow us to strategize therapies for elective surgeries by adding statin and beta blockers and optimizing the volume status. The post-operative NP measurement will give us another window of opportunity to intervene if the NP value continues to go up and perhaps help us identify patients who are at higher risk for developing cardiovascular complications, despite pre-operative modifications.
Despite a growing literature to support the use of peri-operative biomarkers to screen high risk patients undergoing non cardiac surgery, the major guidelines have shyed away from recommending routine use to risk stratify these patients. This recommendation is based on the observation that there is inconsistent intermediate and long term association and there is lack of treatment related outcome data. At this point, we need further prospective studies to answer these questions before we can start incorporating pre- and post-operative natriuretic peptide measurements into our routine clinical practice.
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