Effect of remote ischemic preconditioning on acute kidney injury in nondiabetic patients undergoing coronary artery bypass graft surgery: a secondary analysis of 2 small randomized trials

Abstract

Background: Novel treatment strategies are required to reduce the development of acute kidney injury (AKI) in patients undergoing cardiac surgery. In this respect, remote ischemic preconditioning (RIPC), a phenomenon in which transient nonlethal ischemia applied to an organ or tissue protects another organ or tissue from subsequent lethal ischemic injury, is a potential renoprotective strategy.

Study design: Secondary analysis of 2 randomized trials.

Setting & participants: 78 consenting selected nondiabetic patients in a university teaching hospital undergoing elective coronary artery bypass graft (CABG) surgery recruited to 2 previously reported randomized studies.

Intervention: RIPC consisted of three 5-minute cycles of right forearm ischemia, induced by inflating a blood pressure cuff on the upper arm to 200 mm Hg, with an intervening 5 minutes of reperfusion, during which time the cuff was deflated. The control consisted of placing an uninflated cuff on the arm for 30 minutes.

Outcomes: AKI measured using Acute Kidney Injury Network (AKIN) criteria, duration of hospital stay, in-hospital and 30-day mortality.

Results: Numbers of participants with AKI stages 1, 2, and 3 were 1 (3%), 3 (8%), and 0 in the intervention group compared with 10 (25%), 0, and 0 in the control group, respectively (P = 0.005). The decrease in AKI was independent of the effect of concomitant aortic valve replacement and cross-clamp times, which were distributed unevenly between the 2 groups.

Limitations: Retrospective analysis of data. More patients in the RIPC group underwent concomitant aortic valve replacement with CABG; although we have corrected statistically for this imbalance, it remains an important confounding variable.

Conclusions: RIPC induced using transient forearm ischemia decreased the incidence of AKI in nondiabetic patients undergoing elective CABG surgery in this retrospective analysis. A large prospective clinical trial is required to study this effect and clinical outcomes in patients undergoing cardiac surgery.

Figure 1

CONSORT (Consolidated Standards of Reporting Trials) flow diagram of patients included in the present study. Study 1 and study 2 refer to previously reported studies from which data were retrospectively analyzed for outcomes in the present study. Study 1 was registered at ClinicalTrials.gov as study number NCT00397163. Abbreviations: AKI, acute kidney injury; RIPC, remote ischemic preconditioning.

Figure 2

Graph shows trends in serum creatinine levels in the 2 groups at baseline and during 72 hours postoperatively. There was no significant difference between the 2 groups using analysis of variance with repeated measures. Note: Conversion factor for creatinine in mg/dL to μmol/L, ×88.4. Abbreviation: RIPC, remote ischemic preconditioning.

Figure 3

Graph shows serial inotrope scores during the 72-hour postoperative period (IScore followed by time in hours) in adult patients undergoing elective coronary artery bypass graft surgery. Compared with control, remote ischemic preconditioning (RIPC) has no effect on inotrope scores. Inotrope scores were calculated using the formula: Inotrope score = Dosages (in μg/kg/min) of Dopamine + Dobutamine + [(Adrenaline + Noradrenaline + Isoproterenol) × 100] + [Enoximone × 15], adapted from Ko et al. There was no significant difference between inotrope scores at different times using analysis of variance with repeated measures. Values presented as mean ± standard error of the mean.