Background and methods: Calcium-channel blockers may attenuate vasospasm after transient ischemia and improve organ blood flow after resuscitation. Our aim was to assess the effect of diltiazem on systemic oxygen delivery and consumption, hemodynamics, electroencephalogram (EEG), and organ blood flow after restoration of spontaneous circulation. After a 3-min period of asphyxial cardiac arrest, 14 pigs (20 to 27 kg) were randomly allocated to treatment with either diltiazem (0.1 mg/kg bolus followed by an iv infusion of 0.025 mg/min/kg over 120 mins) or placebo, given at 5 mins after successful resuscitation. Organ blood flow was measured using tracer microspheres 120 mins after resumption of spontaneous circulation.
Results: Median systemic oxygen delivery index values at 30, 60, and 120 mins after restoration of spontaneous circulation were 18.2 mL/min/kg (range 14.8 to 20.7), 16.8 mL/min/kg (13.2 to 20.8), and 19.6 mL/min/kg (16.9 to 21.0), respectively, in the diltiazem group and 13.1 mL/min/kg (11.2 to 14.6), 11.9 mL/min/kg (10.3 to 13.3), and 14.7 mL/min/kg (11.4 to 17.2), respectively, in the control group (p less than .05 for all three comparisons). At the same points in time, median systemic oxygen consumption indices were 3.2 mL/min/kg (range 2.2 to 3.7), 2.1 mL/min/kg (1.9 to 3.0), and 2.6 mL/min/kg (1.8 to 3.8) in the diltiazem group and 2.8 mL/min/kg (2.1 to 4.0), 2.7 mL/min/kg (1.7 to 4.3), and 2.3 mL/min/kg (1.6 to 3.8) in the placebo group (NS). Diltiazem enhanced the postarrest recovery of EEG total power. Right and left cerebral blood flow 120 mins after restoration of spontaneous circulation was significantly (p less than .01) higher in the diltiazem group in comparison with the control group.
Conclusions: Diltiazem causes an increase in systemic oxygen delivery index by promoting vasodilation, but it does not change systemic oxygen consumption index in comparison to placebo treatment. It may be that an impairment in local autoregulation and/or in oxidative metabolism at the cellular or subcellular level was the reason why diltiazem did not improve these derangements. The observed increase in cerebral blood flow and in EEG recovery may be beneficial to the brain after a period of asphyxia.