Cerebral Oximetry-Monitored Nitroglycerin Infusion and Tissue Perfusion during Rewarming of Cardiopulmonary Bypass in Cardiac Surgery: A Prospective Randomized Trial.

Jia-Lin Chen,Hung-Yen Ke,Yung-Chi Hsu,Chih-Yuan Lin,Chi-Hsiang Chung,Po-Shun Hsu,Tso-Chou Lin,Go-Shine Huang,Chien-Sung Tsai

doi:10.3390/jcm11030712

Abstract

Background: Nitroglycerin facilitates microcirculation and oxygen delivery through vasodilation. The purpose of this study was to clarify the effects of nitroglycerin-induced vasodilation and potential hypotension on tissue perfusion under cerebral oximetry monitoring during rewarming in cardiopulmonary bypass. Methods: Elective cardiac surgical patients were randomly assigned to either a nitroglycerin group (n = 32) with an intravenous infusion of 1–5 mcg/kg/min or a control group (n = 31) with 0–0.1 mcg/kg/min infusion, since the initiation of rewarming. Perioperative arterial blood gas data were collected in addition to hemodynamic variables, cerebral oximetry values, urine output, and postoperative outcomes. Results: Nearly one-fifth (6/32) of patients in the nitroglycerin group experienced transient (≤5 min) profound hypotension (mean arterial blood pressure ≤40 mmHg) after the initiation of infusion. There were no significant differences between groups in terms of perioperative levels of cerebral oximetry, cardiac index, plasma glucose, lactate, bicarbonate, base excess, or post-bypass activated coagulation time. In the nitroglycerin group, urine output was nonsignificantly higher during cardiopulmonary bypass (p = 0.099) and within 8 h after surgery (p = 0.157). Perioperative transfused blood products, postoperative inotropic doses, extubation time, and intensive care unit stay were comparable for the two groups. Conclusions: Initiation of intravenous nitroglycerin infusion (at 1–5 mcg/kg/min) during rewarming in hypothermic cardiopulmonary bypass resulted in transient profound hypotension in one-fifth of patients and did not improve perioperative cerebral oxygenation, tissue perfusion, and coagulation in cardiac surgery.

Highlights

Before the commencement of this study, statistical power analyses performed with G*Power [13] revealed that a sample size of 27 patients per group was required to achieve 80% power for an effect size of 0.78 in the primary endpoint of post-Cardiopulmonary bypass (CPB) blood glucose levels [14] because we did not find any previously published data on lactate levels following nitroglycerin infusion during rewarming of CPB
According to Taiwan’s prescribing information for nitroglycerin infusion, a dose of 1–5 mcg/kg/min is recommended for maintaining intraoperative hypotension, whereas 0.05–0.1 mcg/kg/min is appropriate for acute congestive heart failure
Intravenous infusion of nitroglycerin at 1–5 mcg/kg/min during rewarming of CPB resulted in transient profound hypotension in nearly one-fifth of patients

Summary

Introduction

Intravenous low-dose (0.05–0.1 mcg/kg/min) administration of nitroglycerin before and during CPB could prevent a decrease of cerebral oximetry value through vasodilation during CPB [2], but had no significant effect on arterial blood oxygen tension during cardiac surgery [8]. The purpose of this study was to clarify the effects of nitroglycerin-induced vasodilation and potential hypotension on tissue perfusion under cerebral oximetry monitoring during rewarming in cardiopulmonary bypass. Results: Nearly one-fifth (6/32) of patients in the nitroglycerin group experienced transient (≤5 min) profound hypotension (mean arterial blood pressure ≤40 mmHg) after the initiation of infusion. Conclusions: Initiation of intravenous nitroglycerin infusion (at 1–5 mcg/kg/min) during rewarming in hypothermic cardiopulmonary bypass resulted in transient profound hypotension in one-fifth of patients and did not improve perioperative cerebral oxygenation, tissue perfusion, and coagulation in cardiac surgery

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