Hyperbaric oxygen reduces infarct volume in rats by increasing oxygen supply to the ischemic periphery

Objective: Hyperbaric oxygen (HBC) increases oxygen supply to anoxic areas. To examine the therapeutic effect of HBO on ischemic stroke, we measured infarct volume as well as cerebral blood flow (CBF), oxygen supply, and lipid peroxidation in the ischemic periphery. Design: Prospective experimental study in rats. Setting: Experimental laboratory in a university teaching hospital. Subjects: Thirty-eight adult rats. Intervention: The rats were anesthetized (1% halothane) and intubated. Focal ischemia was induced by ligating the right middle cerebral and right common carotid arteries. Nineteen animals were exposed to 2 hrs of HBO (100% oxygen, 3 atmospheres absolute), initiated 10 mins after the onset of ischemia. The remaining animals were kept at ambient pressure and used as controls. Measurements and Main Results:At the initiation of ischemia, CBF measured by a laser-Doppler flow probe placed in the ischemic periphery was reduced to 47% +/- 11% and 51% +/- 15% of normal levels in animals exposed or not to HBO, respectively. These altered values were not affected further by administration of HBC and remained stable throughout a 2-hr observation period. Arterial oxygen pressure and content were significantly increased to 1571 +/- 130 torr (209.41 +/- 17.32 kPa; p < .0001) and 1.03 +/- 0.04 mmol/dL (p < 0.0001), respectively, in HBC-treated animals compared with nontreated animals (139 +/- 14 torr [18.53 +/- 1.87 kPa] and 0.86 +/- 0.04 mmol/dL, respectively), The calculated increase in the oxygen supply to the ischemic periphery was 20%. The infarct volume of HBO-treated animals measured 24 hrs after the onset of focal cerebral ischemia was significantly reduced by 18% (HBO-treated, 132 +/- 13 mm(3) vs. nontreated, 161 +/- 29 mm(3); p = .02), Lipid peroxidation was unchanged after 120 mins of HBO administration in the cerebral cortex where the laser-Doppler flow probe was placed. Conclusions: HBO at 3 atmospheres absolute reduced infarct volume by increasing oxygen supply to the ischemic periphery without aggravating lipid peroxidation, suggesting that HBO can be useful In treating stroke victims. (Crit Care Med 2000; 28: 2831-2836).