Why the fuss?

Acute renal injury is a common post-operative complication among high-risk patients and after major surgery, particularly cardiac and major vascular surgery, as is relevant to this study. The clinical relevance of ischaemic preconditioning continues to be controversial.

Even mild post-operative acute kidney injury (AKI) is associated with a wide range of poor perioperative outcomes, and current interventions have struggled to reduce such risk.

What is remote ischaemic preconditioning (RIPC)?

In an effort to protect an at-risk end organ from ischaemia (eg. heart, brain, kidneys), RIPC cyclically induces ischaemia in a remote site (typically an arm using an NIBP cuff). This activates physiological protective mechanisms against hypoxia and reperfusion injury in the target organ. It is cheap, easy and safe.

RIPC as a technique is based upon Murray’s 1986 observations of dog LAD arteries.

Although remote ischaemic (pre)conditioning has been demonstrated in animal models, human studies have been contradictory.

What was done...

This Shanghai research team randomised 130 patients undergoing open aortic arch replacement to receive either remote ischaemic preconditioning (4x 5-min-up 5-min-down) or sham preconditioning.

They found...

Fewer patients demonstrated renal injury at 7 days in the treatment group (55% vs 74%, ARR 95% CI 2-35%), in addition to shortening mechanical ventilation duration (18 vs 25 hours).

Practice changing? No

Although this study has shown a marked reduction in AKI in a uniquely very-high-risk group, as a sole small single-centered study it can barely be applied to the actual study population, let alone generalised to other high-risk groups.

Even when AKI in the control group was a massive 74%, the confidence interval for absolute risk reduction (2-35%) is so wide as to cast doubt on the credibility of this result.

Go deeper:

Meybohm (NEJM 2015), Hausenloy (NEJM 2015), and Menting (Cochrane 2017) failed to show any significant renoprotective effect from RIC in other high-risk groups.

summary

• Hui Zhou, Lijing Yang, Guyan Wang, Congya Zhang, Zhongrong Fang, Guiyu Lei, Sheng Shi, and Jun Li.
• From the Department of Anesthesiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
• Anesth. Analg. 2019 Jul 1; 129 (1): 287-293.

BackgroundAcute kidney injury is a common complication after open total aortic arch replacement but lacks effective preventive strategies. Remote ischemic preconditioning has controversial results of its benefit to the kidney and may perform better in high-risk patients of acute kidney injury. We investigated whether remote ischemic preconditioning would prevent postoperative acute kidney injury after open total aortic arch replacement.MethodsWe enrolled 130 patients scheduled for open total aortic arch replacement and randomized them to receive either remote ischemic preconditioning (4 cycles of 5-minute right upper limb ischemia and 5-minute reperfusion) or sham preconditioning (4 cycles of 5-minute right upper limb pseudo ischemia and 5-minute reperfusion), both via blood pressure cuff inflation and deflation. The primary end point was the incidence of acute kidney injury within 7 days after the surgery defined by the Kidney Disease: Improving Global Outcomes criteria. Secondary end point included short-term clinical outcomes.ResultsSignificantly fewer patients developed postoperative acute kidney injury with remote ischemic preconditioning compared with sham (55.4% vs 73.8%; absolute risk reduction, 18.5%; 95% CI, 2.3%-34.6%; P = .028). Remote ischemic preconditioning significantly reduced acute kidney injury stage II-III (10.8% vs 35.4%; P = .001). Remote ischemic preconditioning shortened the mechanical ventilation duration (18 hours [interquartile range, 14-33] versus 25 hours [interquartile range, 17-48]; P = .01), whereas no significant differences were observed between groups in other secondary outcomes.ConclusionsRemote ischemic preconditioning prevented acute kidney injury after open total aortic arch replacement, especially severe acute kidney injury and shortened mechanical ventilation duration. The observed renoprotective effects of remote ischemic preconditioning require further investigation in both clinical research and the underlying mechanism.

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