Beneficial effects of dexmedetomidine on ischaemic myocardium of anaesthetized dogs

We have studied the effect of dexmedetomidine during coronary artery stenosis (CAS) 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 micrograms kg-1, respectively. Dexmedetomidine decreased plasma concentrations of noradrenaline by mean 71 (SEM 9)%, heart rate by 8 (4)%, cardiac output by 30 (6)% and increased mean arterial pressure by 23 (10)%. Dexmedetomidine reduced blood flow in non-ischaemic myocardium and in the ischaemic epicardial layer by 16 (8)%, but blood flow was preserved in the ischaemic mid-myocardial and subendocardial layers. Consequently, dexmedetomidine increased the ischaemic-non-ischaemic blood flow ratio. Dexmedetomidine did not change myocardial oxygen consumption but decreased myocardial oxygen demand from 4.91 (0.33) to 3.76 (0.25) mumol min-1 g-1, thereby reducing the oxygen deficiency of the ischaemic myocardium from 1.47 (0.37) to 0.29 (0.32) mumol min-1 g-1.