1988 Volume 28 Issue 2 Pages 117-122
The effects of hyperbaric oxygen and hypotension on postischemic cerebral edema were studied in cats. The middle cerebral artery (MCA) was transorbitally occluded for 3 hours and reperfused for 3 hours, and cats whose cortical blood flow (CoBF) decreased to lower than 10ml/100g/min with MCA occlusion were included in the study. Ten cats were used as controls, six were in the hypotension group, and six were in the hyperbaric group (hyperbaric oxygen plus hypotension). The hyperbaric oxygen (2 atm of pure oxygen) was started 1 hour after MCA occlusion and was administered for 1 hour. Just before and during reperfusion, the mean arterial blood pressure was lowered about 50mmHg from the baseline value via administration of adenosine triphosphate and dipyridamole. In the control group, the preocclusive CoBF (measured by the hydrogen clearance method) was 65.9±20.6ml/100g/min, whereas just after reperfusion it was 35.0±21.5ml/100g/min. Three hours after reperfusion the CoBF was 8.2±11.0ml/100g/min. In the hypotension group, these values were 53.9±14.0, 40.6±19.6, and 18.1±12.2ml/100g/min, respectively. In the hyperbaric group, the values were 49.8±8.9, 36.6±13.5, and 27.5±9.0ml/100g/min, respectively. The intracranial pressure (ICP) increased from 9.1±8.6 to 90.0±22.6mmHg in the control group, from 4.5±6.5 to 37.7±10.1mmHg in the hypotension group, and from 1.7±3.5 to 29.8±20.9mmHg in the hyperbaric group. The water content (measured by the drying/weighing method) of the affected hemisphere was 79.7±0.5% in the control group, 79.1±0.5% in the hypotension group, and 78.3±0.5% in the hyperbaric group.
Hypotensive reperfusion improved the CoBF, ICP, and water content. Hyperbaric oxygen plus hypotension were more effective than hypotension alone. Hypotensive reperfusion decreases the vascular volume and reduces the strain on the vasoparalytic vascular wall, thereby decreasing vasogenic edema. Hyperbaric oxygen improves the metabolism of the vascular wall during ischemia and maintains the strength of the vessel wall against intravascular pressure. Thus, hyperbaric oxygen reduces brain edema more than vascular volume. Together, hyperbaric oxygenation and hypotensive reperfusion are useful as adjuncts to acute cerebral revascularization.
