Second report of an experimental study of cerebrocardiopulmonary resuscitation (CCPR) in dogs with reference to a new continuous brain cooling method, using a Resusci Pump TM-1.

In our previous report, the effect of CCPR (an intracarotid hypothermic infusion combined with the existing CPR) has been described by the authors on dogs in which cardiac arrest had been induced by the inhalation of nitrous oxide. This report contains a new continuous brain cooling method, using a Resusci Pump TM-1 which has been newly devised by us and which has a carotid-carotid bypass in order to reduce oxygen consumption and cerebral metabolism while maintaining a continuous cerebral blood flow. Cardiac arrest was induced experimentally by electrical stimulation. The duration of cardiac arrest was 5 to 10 min duration. The continuous brain cooling was carried out during the period of 10-30 min. Through the experiment, we have investigated vital signs, acid base balance, cardiac output, carotid arterial blood flow, oxygen availability of the brain tissue, and regional cerebral blood flow in both groups of CPR and CCPR . As for the clinical signs and cardiac output, there were no significant differences between two groups. Oxygen availability of the brain tissue and regional blood flow were much more improved in CCPR group than in CPR group. The brain was selectively cooled by means of the continuous brain cooling. This resulted in the minimum effect on circulatory and respiratory system as compared to the effects caused by general hypothermia. Furthermore, the continuous brain cooling decreased cerebral metabolism and CMRO2, and prevented a progressive development of cerebral hypoxia Cerebral perfusion at a given constant pressure may protect the brain tissue from the disturbance of cerebral microcirculation. Therefore, we might expect the continuous brain cooling to have a beneficial effect on cerebral respiration, circulation and metabolism.