B-type natriuretic peptide in high-risk major surgery patients

Abstract

Editor—We read with great interest the article by Cuthbertson and colleagues1Cuthbertson BH Amiri AR Croal BL et al.Utility of B-type natriuretic peptide in predicting perioperative cardiac events in patients undergoing major non-cardiac surgery.Br J Anaesth. 2007; 99: 170-176Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar demonstrating the association of preoperative B-type natriuretic peptide (BNP) levels and adverse cardiac events. In 204 low to intermediate risk patients undergoing major non-cardiac surgery, moderately elevated preoperative BNP levels of 40 pg ml−1 predicted early postoperative death or myocardial injury (area under the ROC curve 0.72; 95% CI interval 0.59–0.86). This article underlines recent suggestions that the biochemical markers BNP and N-terminal pro-brain natriuretic peptide (NT-proBNP) outperform existing cardiac risk scores regarding prognostic importance.2Dernellis JM Panaretou MP Assessment of cardiac risk before noncardiac surgery: brain natriuretic peptide in 1590 patients.Heart. 2006; 92: 1645-1650Crossref PubMed Scopus (112) Google Scholar 3Feringa HH Schouten O Dunkelgrun M et al.Plasma N-terminal pro-B-type natriuretic peptide as long-term prognostic marker after major vascular surgery.Heart. 2007; 93: 226-231Crossref PubMed Scopus (69) Google Scholar Unfortunately, the short in-hospital observation period of 72 h limits the significance and clinical importance of this hitherto largest blinded trial on the prognostic power of preoperative BNP. Although the majority of myocardial infarctions occurs within the first 48 h after surgery, delayed postoperative myocardial infarction is a well-known complication and may have been missed in this trial. Furthermore, as mentioned in the editorial4Sear JW Howard-Alpe G Preoperative plasma BNP concentrations: do they improve our care of high-risk non-cardiac surgical patients?.Br J Anaesth. 2007; 99: 151-154Abstract Full Text Full Text PDF PubMed Scopus (7) Google Scholar accompanying this study, postoperative determination of NT-proBNP provides additional prognostic information to preoperative levels regarding in-hospital and long-term cardiac outcome.5Mahla E Baumann A Rehak P et al.N-terminal pro-brain natriuretic peptide identifies patients at high risk for adverse cardiac outcome after vascular surgery.Anesthesiology. 2007; 106: 1088-1095Crossref PubMed Scopus (69) Google Scholar BNP and NT-proBNP are released from cardiac myocytes in response to ischaemia or myocardial stretch and plasma levels correlate well with the extent of inducible ischaemia.6Bibbins-Domingo K Ansari M Schiller NB et al.B-type natriuretic peptide and ischemia in patients with stable coronary disease: data from the Heart and Soul study.Circulation. 2003; 108: 2987-2992Crossref PubMed Scopus (210) Google Scholar Preoperative ‘stable’ levels of natriuretic peptides therefore do not necessarily reflect the variable dynamic consequences of the intra- and postoperative stress response which culminates in adverse in-hospital7Landesberg G Mosseri M Zahger D et al.Myocardial infarction after vascular surgery: the role of prolonged stress-induced, ST depression-type ischemia.J Am Coll Cardiol. 2001; 37: 1839-1845Crossref PubMed Scopus (221) Google Scholar and long-term cardiac outcome.8Bursi F Babuin L Barbieri A et al.Vascular surgery patients: perioperative and long-term risk according to the ACC/AHA guidelines, the additive role of post-operative troponin elevation.Eur Heart J. 2005; 26: 2448-2456Crossref PubMed Scopus (80) Google Scholar Thus, although we recognize that the importance of postoperative NT-proBNP determination in non-cardiac surgery was just very recently published, the significance of the results of Cuthbertson and colleagues would have been further improved by a prolonged observation period and by additional postoperative BNP determinations. B. H. Cuthbertson* (on behalf of the authors) Aberdeen, UK *E-mail: [email protected] Editor—In reply to the interesting points made by Dr Mahla and colleagues, we agree with many of the statements made in their letter. However, the measurement of BNP in the postoperative period does not add any additional predictive power to preoperative BNP measurement in the prediction of these short-term outcomes such as early postoperative cardiac events (unpublished data from same cohort). Further, our work on the predictive power of BNP for medium term mortality is about to be published in the American Journal of Cardiology within the next 2 months. I am sure the respondents will find this paper interesting. Although we may have missed some of the postoperative cardiac events occurring in hospital in this cohort due to our timing of measurements, we feel that any significant events will be detected in medium term mortality analysis. As they state, other work suggests this is the case.