Cerebral physiology in paediatric cardiopulmonary bypass.
OBJECTIVE
To analyze studies of neurological injury after open-heart surgery in infants and children and to discuss the effects of cardiopulmonary bypass, hypothermia and deep hypothermic circulatory arrest on cerebral blood flow, cerebral metabolism and brain temperature.


METHODS
Articles were obtained from the databases, Current Science and Medline, from 1966 to present. Search terms include cardiopulmonary bypass (CPB), hypothermia, cerebral blood flow (CBF), cerebral metabolism and brain temperature. Information and abstracts obtained from meetings on the topic of brain and cardiac surgery helped complete the collection of information.


RESULTS
In adults the incidence of neurological morbidity is between 7 to 87% with stroke in about 2-5%, whereas the incidence of neurological morbidity increases to 30% in infants and children undergoing cardiopulmonary bypass. Besides the medical condition of the patient, postoperative cerebral dysfunction and neuronal ischaemia associated with cardiac surgery in infants and small children are a combination of intraoperative factors. Deep hypothermic circulatory arrest impairs CBF and cerebral metabolism even after termination of CPB. Inadequate and/or non-homogenous cooling of the brain before circulatory arrest, as well as excessive rewarming of the brain during reperfusion are also major contributory factors.


CONCLUSIONS
Newer strategies, including the use of low-flow CPB, pulsatile CPB, pH-stat acid-base management and a cold reperfusion, are being explored to ensure better cerebral protection. Advances in monitoring technology and better understanding of the relationship of cerebral blood flow and metabolism during the different modalities of cardiopulmonary bypass management will help in the medical and anaesthetic development of strategies to improve neurological and developmental outcomes.
Pua
H L
HL
Department of Anaesthesia, Hospital for Sick Children, University of Toronto, Ontario, Canada.
Bissonnette
B
B
D000136:Acid-Base Equilibrium; D000328:Adult; D001831:Body Temperature / Q000502:physiology; D001921:Brain / Q000378:metabolism / Q000502:physiology*; D001927:Brain Diseases / Q000209:etiology; D002545:Brain Ischemia / Q000209:etiology; D006348:Cardiac Surgical Procedures / Q000009:adverse effects; D002315:Cardiopulmonary Bypass / Q000009:adverse effects / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology; D002561:Cerebrovascular Disorders / Q000209:etiology; D002648:Child; D017679:Cryotherapy; D006324:Heart Arrest, Induced / Q000009:adverse effects; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects; D007223:Infant; D016343:Monitoring, Intraoperative; D011183:Postoperative Complications; D015427:Reperfusion Injury / Q000209:etiology; D017694:Rewarming