Journal of Invasive Cardiology

Attempts were made to run separate analyses for studies that reported values of troponin at 24 hours and area under the curve (AUC) troponin at 72 hours, but this resulted in small sample sizes and unreliable results (data not shown). An analysis for the interaction of RIPC and beta-blockers or sevoflurane/desflurane was also not possible, because no study reported outcomes stratified for the use of these drugs. Only 2 studies reported data on mortality, and thus the effect of RIPC could not be estimated.

The analysis of the impact of RIPC on creatinine levels included 3 studies with patients undergoing open AAA repair^61-63 and 2 studies with patients undergoing on-pump CABG.^42,58 Patients undergoing RIPC had a significant reduction in the levels of creatinine in the first few days after surgery (SMD, 0.28; 95% CI, -0.49 to -0.08; P=.007; I2 = 51%) (Figure 6).

Discussion

Overall, our meta-analysis suggests that RIPC is an effective cardiac and renal protective strategy across different interventions as measured by biomarkers. In addition, we demonstrate for the first time that it reduces the incidence of myocardial infarction in the perioperative period for patients undergoing cardiovascular interventions.

Although the results obtained are similar to a previously published meta-analysis by Takagi et al,⁶⁴ the SMD obtained by our analysis is lower (SMD, -0.54; 95% CI, -1.01 to -0.08 for ours vs SMD, -0.81; 95% CI, -1.29 to -0.33 for Takagi’s study). Since our analysis included 2 recent large trials with negative results,^42,43 we can argue that this lower SMD is associated with a truly stronger effect. Besides, their meta-analysis had a small sample size (4 studies with a total of 184 patients), unexpected lack of heterogeneity, poor comparison between different interventions, and inability to compare different types of ischemic stimulus,⁶⁵ all limitations that we tried to avoid.

We made an effort to compare the effectiveness of RIPC across different interventions: cardiac surgery (ie, CABG and heart valve replacement surgery), PCI both during elective and ST-elevation myocardial infarction and AAA repair (open and endovascular). In adults undergoing cardiac surgery, RIPC reduces the chances of myocardial injury significantly (SMD, -0.68; 95% CI, -1.20 to -0.16) and further subgroup analysis suggests that this benefit is higher in on-pump CABG (SMD, -0.49; 95% CI, -1.20 to 0.22; P=.18). However, this impact was not confirmed in the largest study on RIPC for CABG so far, published by Rahman et al.⁴²