BENEFICIAL-EFFECTS OF DEXMEDETOMIDINE ON ISCHEMIC MYOCARDIUM OF ANESTHETIZED DOGS

We have studied the effect of dexmedetomidine during coronary artery s tenosis (GAS) in dogs. Three periods of 15 min of CAS were induced at 40-min intervals in two groups of dogs (dexmedetomidine compared with placebo). Dexmedetomidine was administered before the second and third periods of CAS in doses of 1 and 3 mu g kg(-1), respectively. Dexmede tomidine decreased plasma concentrations of noradrenaline by mean 71 ( SEM 9) %, heart rate by 8 (4) %, cardiac output by 30 (6) % and increa sed mean arterial pressure by 23 (10) %. Dexmedetomidine reduced blood flow in non-ischaemic myocardium and in the ischaemic epicardial laye r by 16 (8) %, but blood flow was preserved in the ischaemic mid-myoca rdial and subendocardial layers. Consequently, dexmedetomidine increas ed the ischaemic-non-ischaemic blood flow ratio. Dexmedetomidine did n ot change myocardial oxygen consumption but decreased myocardial oxyge n demand from 4.91 (0.33) to 3.76 (0.25) mu mol min(-1) g(-1), thereby reducing the oxygen deficiency of the ischaemic myocardium from 1.47( 0.37) to 0.29 (0.32) mu mol min(-1) g(-1).