TOTAL AND REGIONAL CEREBRAL BLOOD-FLOW DURING PERFUSION FROM THE LATERAL VENTRICLE TO THE CISTERNA MAGNA IN THE CONSCIOUS DOG - EFFECT OF HEMORRHAGIC HYPOTENSION AND RETRANSFUSION ON CEREBRAL BLOOD-FLOW

  • 1 January 1980
    • journal article
    • research article
    • Vol. 7  (3) , 333-342
Abstract
Autoregulation of regional cerebral blood flow (rCBF) may occur in conscious dogs with ventriculocisternal perfusion (VCP) during moderate hypotension. Six dogs were perfused for 360 min using mock CSF. A 120-min control period was followed by 180 min of moderate hemorrhagic hypotension (mean arterial pressure [SAP] 60-80 mm Hg). The lost blood (.apprx. 40% of the calculated blood volume) was retransfused after 300 min of perfusion and an additional 60 min of observation concluded the study. The rCBF was measured at 120, 240 and 360 min of perfusion using labeled microspheres of 15 .mu.m diameter. Cardiac output (CO) was 2.8 .+-. 0.41 l/min at 120 min, decreased to 1.4 .+-. 0.10 l/min after hemorrhage and rose after retransfusion to 2.2 .+-. 0.13 l/min. The percentage of cardiac output (%CO) received by the brain was 1.8 .+-. 0.37% at 120 min, 3.8 .+-. 0.44% at 240 min and 2.2 .+-. 0.22% after retransfusion (P < 0.05). There was no significant change in rCBF during hypotension. The regional cerebral blood flow was significantly elevated in the thalamus, mesencephalon, pos and medulla after retransfusion, indicating a local alteration of set point in the plateau of the autoregulatory curve. Cerebral venous pH (measured in internal maxillary venous blood) decreased significantly during hemorrhage to 7.25, while cerebral arteriovenous difference of O2 and arteriovenous pH increased significantly during hemorrhage. Autoregulation of total cerebral blood flow (CBF) during acute moderate hypotension remains intact during VCP at a rate of 0.2 ml/min using a perfusate of a constant pH; CSF-pH appears not to be of major significance for the autoregulation of CBF in moderate hypotension.