Abstract 3372: Remote Ischaemic Pre-conditioning in Human Coronary Artery Bypass Surgery: From Promise to Disappointment
Aims We assessed whether remote ischaemic pre-conditioning (RIPC) improves myocardial, renal and lung protection in non-diabetic patients undergoing on-pump multi-vessel coronary artery surgery.
Methods Single center prospective, randomized, placebo intervention-controlled trial (placebo n=82; RIPC n=80). Patients, investigators, anesthetists, surgeons and critical care teams were all blind to group allocation. Subjects were randomized (1:1) to RIPC (or placebo) stimuli (3x upper limb (or dummy arm) 5 minute cycles of 200mmHg cuff inflation/deflation) during sternotomy and conduit procurement. Anesthesia, perfusion, cardioplegia and surgical techniques were standardized. The primary end point was 48hour area under the curve (AUC) for troponin T (cTnT) release. Secondary end points were 6hour and peak cTnT, electrocardiographic changes, cardiac index, incidence of low cardiac output episodes (LCOE), inotrope and vasoconstrictor use, renal dysfunction and lung injury.
Results Groups were well matched on demographic and operative variables. There was one hospital death. Between placebo and RIPC, there was no difference in median(IQR)AUC48h cTnT(ng.ml−1.48h−1, general linear model); 28(19–39) vs 30(22–38), 6hr-cTnT(ng.ml−1); 0.93(0.59–1.35) vs 1.01(0.72–1.43), peak cTnT(ng.ml−1); 1.02(0.74–1.44) vs 1.04(0.78–1.51), de novo left bundle branch block (4 vs 0%) or Q waves (5.3 vs 5.5%). Serial cardiac indices (L.min−1m−2) were not different on repeated measures ANOVA (4h 2.51±0.55 vs. 2.54±0.55). IABP usage(8.5 vs 7.5%), LCOE incidence(24 vs 34%), inotrope(39 vs 50%) and vasoconstrictor usage(66 vs 64%) were not different. Dialysis requirement(1.2 vs 3.8%), peak creatinine (median(IQR) 106μmol.L−1(96–123) vs 110(95–131)) and AUC urinary albumin-creatinine ratios 69(40–112) vs 58(32–85)) were not different. Intubation times; median(IQR), 937min(766–1402) vs 895(675–1180), 6 hour; 37(28–45) vs 36(29–43) and 12 hour pO2/FiO2 ratios 34(26–43) vs 35(28–41) were similar. Case urgency did not influence RIPC effect.
Conclusion In contrast to prior smaller studies, RIPC did not reduce troponin release, improve post-operative hemodynamics or afford enhanced renal or lung protection in this double-blind study.