Responsiveness of cerebral vessels to changes of blood pressure and partial pressure of carbon dioxide after a transient period of cardiac arrest in dogs

Abstract

Post-ischemic cerebral hypoperfusion supposedly due to constriction of cerebral vessels is considered to be one of the most important factors limiting the recovery of the brain after cerebral ischemia. An experimental study on dogs was carried out to determine the changes in the responsiveness of cerebral vessel to the dilating effects of increase of arterial pressure (AP) and of CO 2 inhalation after 3–6 min of cardiac arrest. Responsiveness was measured by the ratio of change in intracranial pressure (ICP) to change in AP ( ΔICP ΔAP ) and to change in P Co 2 ( ΔICP ΔP CO 2 ), since in a bony cranium the changes in cerebral vessel diameter are reflected by instantaneous ICP change. ΔICP/gDAP following the administration of intravenous epinephrine was 33%, 43%, 36%, 37% and 16% of pre-ischemic value 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. ΔICP ΔP CO 2 following 10% CO 2 inhalation was 13%, 32%, 55%, 50%, 70% and 75% of pre-ischemic value 1 2 h, 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. Normal ΔICP/central venous pressure (ΔCVP) was observed during the post-ischemic period, although statistical analysis was not done. From this we concluded: (1) After 3–6 min of cardiac arrest, cerebral arteries constricted for more than 5 h during post-ischemic period. (2) These arteries did not respond well to the dilating effects of increased arterial pressure or CO 2 inhalation, but after 3 h their responses to CO 2 inhalation returned to their pre ischemic levels. (3) The intracranial pressure became more or less dependent on CVP during post-ischemic period.