Effects of On-Pump and Off-Pump Coronary Artery Bypass Surgery on Metabolic Profiles in the Early Postoperative Period

Abstract

We read, with great interest, the recent article from the Journal of Cardiothoracic and Vascular Anesthesia comparing metabolic profiles following on-pump and off-pump coronary artery bypass surgery.1Sanfilippo F. Chiarenza F. Cassisi C. et al.The effects of on-pump and off-pump coronary artery bypass surgery on metabolic profiles in the early postoperative period.J Cardiothorac Vasc Anesth. 2016; 30: 909-916Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar Despite large randomized controlled trials demonstrating similar outcomes for both techniques,2Lamy A. Devereaux P.J. Prabhakaran D. et al.Off-pump or on-pump coronary-artery bypass grafting at 30 days.N Engl J Med. 2012; 366: 1489-1497Crossref PubMed Scopus (526) Google Scholar, 3Diegeler A. Börgermann J. Kappert U. et al.Off-pump versus on-pump coronary-artery bypass grafting in elderly patients.N Engl J Med. 2013; 368: 1189-1198Crossref PubMed Scopus (354) Google Scholar the debate between proponents of each technique seems to rage on. While we found the results to be interesting, especially the fractionally higher use of vasopressors after off-pump coronary artery bypass graft, we have some concerns about the lack of intraoperative data available to the authors. This study aimed to compare metabolic profiles of patients in the immediate postoperative period, and we believe that the intraoperative management of such patients could be relevant over the following 24 hours. The readers are provided with a brief recipe of a typical anesthetic from the institution. However, we feel the lack of further details limits the strength of the study. Isoflurane is known to have a role in myocardial ischemic preconditioning4Kersten J.R. Schmeling T.J. Pagel P.S. et al.Isoflurane mimics ischemic preconditioning via activation of K(ATP) channels: Reduction of myocardial infarct size with an acute memory phase.Anesthesiology. 1997; 87: 361-370Crossref PubMed Scopus (452) Google Scholar, 5Lotz C. Zhang J. Fang C. et al.Isoflurane protects the myocardium against ischemic injury via the preservation of mitochondrial respiration and its supramolecular organization.Anesth Analg. 2015; 120: 265-274Crossref PubMed Scopus (19) Google Scholar; therefore, the relative use of isoflurane or propofol infusion for the maintenance of anesthesia may be relevant. Use of intraoperative vasopressors or inotropes also can have a marked influence on the postoperative period. For example, a loading dose of enoximone could affect both myocardial contractility and vasopressor requirement dramatically in the immediate postoperative period. Furthermore, duration of cardiopulmonary bypass was not stated for the on-pump group. There is ample evidence of prolonged bypass times having a significant effect on metabolic state immediately following surgery,6Whitten C.W. Hill G.E. Ivy R. et al.Does the duration of cardiopulmonary bypass or aortic cross-clamp, in the absence of blood and/or blood product administration, influence the IL-6 response to cardiac surgery?.Anesth Analg. 1998; 86: 28-33PubMed Google Scholar, 7Salis S. Mazzanti V.V. Merli G. et al.Cardiopulmonary bypass duration is an independent predictor of morbidity and mortality after cardiac surgery.J Cardiothorac Vasc Anesth. 2008; 22: 814-822Abstract Full Text Full Text PDF PubMed Scopus (248) Google Scholar and any extreme outliers in this group could have skewed the results. While we found the results of the study highly valuable and of definite interest, we would recommend caution in drawing firm conclusions from this retrospective data set.