Gordon Wong, Li Rui, Michael Irwin

University of Hong Kong, Hong Kong SAR

Introduction: Remifentanil has previously been demonstrated to precondition the heart.1 Ischaemic post conditioning (IPoC) has been shown to involve opioid receptors (ORs). 2 This study investigates whether remifentanil confers cardioprotection when given after the start of the index ischaemic event.

Methods: Experiments were performed using the open chest rat model where 30 minutes of ischaemia was induced followed by 2 hours reperfusion. Prior to final reperfusion, the rats received either remifentanil postconditioning (RPoC) (5 mins at 20ug/kg/min), or IPoC (3 cycles of 10-s reperfusion interspersed with 10-s ischemia). These procedures were repeated in the presence of specific kappa OR antagonist nor-binaltorphimine (nBNI) or mu OR antagonist naltrindole (NTD), administered 10 mins before the respective postconditioning manoeuvres. The hearts were then excised and infarct size (IS) was determined and expressed as a percentage of the area at risk (AAR).

Results: Both RPoc and IPoc reduced IS /AAR to a similar extent when compared to control (p<0.05). This protective effect was abolished by the prior administration of any one the antagonists. Sole administration of the antagonists during ischaemia had no effect on the infarct size.

Conclusions: Remifentanil confers cardiac protection when given either before the ischaemic event or just before reperfusion.

1 Zhang et al Anesthesiology 2004; 2Youngho Jang et al Anesthesiology 2008.