Patients undergoing major vascular surgery are at high risk of complications around the time of their surgery. This is because many of them have generalised arterial disease. During surgery blood flow is reduced at the site of surgery, which results in a lack of oxygen and nutrients being delivered to the body tissues (ischaemia). After the blood supply is restored, further damage can occur because of cellular responses and the blood flushing through the tissues. This is known as ischaemia-reperfusion injury.
Ischaemic preconditioning is a method where short periods of induced ischaemia (about 10 minutes) followed by reperfusion are used to protect against the prolonged periods of ischaemia required for surgery. Preconditioning can be carried out on the blood vessels where ischaemia will later occur or remotely, on different blood vessels. The clinical application of remote ischaemic preconditioning for patients undergoing open surgical or endovascular surgeries such as aneurysm repair, carotid endarterectomy, and revascularisation is not known.
We performed a systematic search of the literature to identify all the randomised controlled trials conducted on this topic. A total of 232 patients in four trials were randomised to remote ischaemic preconditioning or no preconditioning for three different operations on blood vessels. Based on the evidence from these small trials, there were too few data to be able to say whether remote ischaemic preconditioning has any beneficial or harmful effects. The studies varied in the surgical procedures, outcome measures and the way remote ischaemia was induced. The number of deaths around the time of surgery was not clearly different between the two groups. Heart attacks (myocardial infarction) may have been reduced in the remote ischaemic preconditioning group but this was apparent in only one trial and was not consistent across the trials. Unplanned critical care admissions tended to increase in the remote ischaemic preconditioning group. All the trials had a high risk of bias and the safety of this technique needs to be confirmed in trials with adequate numbers of participants.