Effect of hypotension induced by ATP and adenosine on brain surface oxygen tensions in the sheep.

A multitipped oxygen electrode has been used to measure cortical surface oxygen tensions in the sheep. A histogram of the pattern of supply of oxygen to cortical tissue within the microcirculation during normal conditions is presented. Systemic arterial pressure was reduced to a mean of 30 mmHg with either Adenosine or ATP, and further oxygen tension measurements undertaken. The oxygen histogram was shifted to the left in these circumstances, and there was an increase in the frequency of occurrence of very low tissue oxygen tensions. This suggests that the use of these agents to induce profound hypotension may be associated with significant ischaemia within the microcirculation.