HCA – Hypothermic Circulatory Arrest

Temperature is a major factor directly affcting cerebral metabolism by reducing the cerebral metabolic rate of oxygen ( CMRO₂) by approximatelty 7%/C reduction in temperature (Goiver et al.1984, Kent and Peirce 1974). Despate the many years of discussion regarding hypothermia, the optimal temperature at which hypothermic circulatory arrest shopuld be caried out continues to be controversial.

Profound hypothermia (15C to 17C) gave better cerebral protectionthan deep hypothermia (18C to 20C) during prolonged hypothermic circulatory arrest in a canine model. (Gillinov et al.1993)

Cerebral oxygen consumption decreases progressively as thre temperature is redused, being 5% of the baseline at 8C; 20% at 13C; and 39% at 18C (Mezrow et al.1994).

No clinical sequela were seen following 90 minutes of HCA at 18C (Mezrow et al.1995a) and both clinical and histological evidence of cerebral injury was demonstrated in pigs after 90 of HCA at 20C. (Midulla at al.1994)