Abstract
BACKGROUND: Nitroglycerin (TNG) has been shown to reverse myocardial ischaemia (MI). Observational studies have suggested that prophylactic doses of intravenous TNG is effective in reducing the incidence of intraoperative MI. However, the results of previous randomised controlled trials are not as convincing. As a result, the effectiveness of prophylactic TNG in the prevention of intraoperative MI remains controversial. The purpose of this study was to evaluate whether prophylactic intravenous TNG can prevent the incidence of intraoperative MI. In addition, we also analyzed haemodynamic changes (heart rate [HR], mean blood pressure [MBP], and pulmonary capillary wedge pressure [PCWP]) from TNG in both pre and post anaesthesia induction as an indicator of the decrease in preload.
METHODS: This quantitative systematic review was performed according to the criteria outlined in the PRISMA statement. A comprehensive literature search was conducted to identify clinical trials which involved the administration of TNG in comparison to a placebo. The data from the individual trials were combined and the DerSimonian and Laird random-effects model was used to calculate either the pooled Relative Risk (RR) or the demonstrated weighted mean difference (WMD) in addition to the corresponding 95% confidence intervals (CI). The data was analyzsed to clarify differences in the incidence of MI. We also analysed haemodynamic changes (HR, MBP, and PWCP) between TNG and the placebo. The heterogeneity of the results was examined by Cochrane’s Q and I2 test.
RESULTS: Using electronic databases, we selected 8 trials for our review. Prophylactic intravenous TNG did not result in a decreased incidence of MI (RR= 0.61; 95% CI, 0.33 to 1.13; p=0..12; I2=55, Cochran’s Q = 13.3). In terms of haemodynamic changes pre and post anaesthesia induction, intravenous TNG significantly reduced the MBP in comparison to the placebo. MBP; pre induction; WMD = -7.27; 95% CI -14.2 to -0.33; P = 0.04; I2 = 97%; Cochrane’s Q = 136.9, post induction; WMD = -0.60; 95% CI -10.3 to -2.09; P = 0.003; I2 = 68%; Cochrane’s Q = 9.48)
CONCLUSIONS: Our analyses showed that prophylactic intravenous TNG does not reduce the incidence of intraoperative MI. Prophylactic doses of intravenous TNG significantly reduced the MBP both pre and post anaesthesia induction. From these results, prophylactic intravenous TNG provided little clinical benefit as it was not effective preventing the incidence of intraoperative MI.

The effectiveness of prophylactic doses of intravenous nitroglycerin in preventing the incidence of myocardial ischaemia under general anaesthesia; a systematic review and meta-analysis