Tuesday, 11 September 2012

Ischaemic Preconditioning and the Brain

I am currently principal investigator in Sheffield for a large multi centre  international surgical study called ERRICA.
This study is investigating the effect of remote ischaemic preconditioning on outcomes after heart surgery in high risk patients.  Essentially, after induction of anaesthesia, the upper limb is made ischaemic with a cuff three times for 3 minutes separated by three episodes of reperfusion. The hypothesis is that repeated ischaemia  of the limb will confer protection to any organ that is made ischaemic within a period of time of the preconditioning. The evidence for ischaemic preconditioning in animals is strong but in humans less so. Regrettably, for various reasons, I do not think that this trial will answer the questions that are being posed. Nonetheless, I am sure the technique has merit. I have always assumed that the protection is mediated by circulating mediators. In he ERRICA study, there will be proteomic studies of recruited patients.
I was surprised (pleasantly) to read a paper about the mechanism of remote ischaemic preconditioning.  This study in rats suggests that the mechanism is mediated through the central nervous system, the brainstem in fact. I do think that ischaemic preconditioning could have a very important role in organ protection whether in cardiac surgery or transplantation. More work however is needed to demonstrate effectiveness in humans and to elucidate the mode of action.