Brain pH monitoring during ischemia

Brain tissue acidosis can result from ischemia when cerebral blood flow reduction reaches a critical value. The portable, battery-operated Khuri pH monitor has been used previously in a large number of patients undergoing cardiopulmonary bypass surgery to monitor the intramyocardial pH during aortic clamping. It was found to be easy to use, reliable, and a strong predictor of myocardial preservation. The goal of this study was to evaluate the applicability of this monitor in the measurement of brain pH.

Fifteen New Zealand white rabbits underwent general endotracheal anesthesia. A right frontal craniotomy was performed and a pH/temperature glass electrode was inserted in the frontal lobe. Both common carotid arteries were exposed in the neck and prepared for occlusion. Three rabbits were used as control; their brain pH was recorded over 60 minutes. Twelve rabbits underwent bilateral common carotid artery occlusion of varying duration and their brain pH measurements were recorded.

There was no significant difference in pH levels at baseline in the two groups (p = 0.604). There were significant differences in pH over time between the control and occlusion group (p = 0.016). The pH dropped steadily and significantly in the occlusion group (p = 0.008), whereas little change in pH was noted over time in the control group (p = 0.366).

The portable Khuri pH monitor has been used by cardiothoracic surgeons to monitor the myocardium during bypass procedures. Our experimental pilot study found it to be reliable in measuring the brain pH and to be relatively simple to use. It is approved by the Food and Drug Administration (FDA). We believe it may be of benefit to neurosurgeons.