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Persistent low cerebral blood flow velocity following profound hypothermic circulatory arrest in infants
B O'Hare1, B Bissonnette, D Bohn
1Department of Anaesthesia, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Infants undergoing heart surgery with profound hypothermic circulatory arrest (PHCA) experience reduced cerebral blood flow velocity (CBFV) in the pediatric intensive care unit. This sustained hypoperfusion may contribute to neurological issues after surgery.
Area of Science:
- Pediatric Cardiology
- Neurocritical Care
- Cardiovascular Surgery
Background:
- Congenital heart disease (CHD) repair in infants can lead to acute neurological complications.
- Hypothermic cardiopulmonary bypass (CPB) and profound hypothermic circulatory arrest (PHCA) are associated with reduced oxygen delivery and altered cerebral metabolism postoperatively.
Purpose of the Study:
- To investigate the duration of cerebral blood flow velocity (CBFV) changes in infants following PHCA.
- To determine if cerebral hypoperfusion persists into the pediatric intensive care unit (PICU) after PHCA.
Main Methods:
- Ten infants undergoing CHD surgery were divided into mild hypothermic CPB or PHCA groups.
- Sequential measurements of CBFV, cerebral perfusion pressure, and other physiological variables were recorded in the PICU.
Main Results:
- The PHCA group demonstrated consistently reduced CBFV compared to the mild hypothermic CPB group (P < 0.05).
- Reduced CBFV in the PHCA group persisted for at least four hours postoperatively.
- No significant differences in cerebral perfusion pressure, temperature, hematocrit, or PaCO2 were observed between groups.
Conclusions:
- Sustained reduction in CBFV occurs after PHCA in infants, extending into the postoperative period.
- This persistent hypoperfusion, despite adequate cerebral perfusion pressure, may contribute to neurological morbidity.
- Findings suggest a prolonged period of cerebrovascular unreactivity following PHCA.
Abstract:
Acute neurological morbidity following repair of congenital heart disease (CHD) in infancy is well recognized, particularly with the modalities of hypothermic cardiopulmonary bypass (CPB) and profound hypothermic circulatory arrest (PHCA). Reduced O2 delivery (perfusion defect) during rewarming following PHCA has been shown in the operating room. This reduction in cerebral blood flow coincides with disordered cerebral metabolism and oxygen utilisation after PHCA. The objective of this study was to extend the period of investigation of cerebral blood flow velocity (CBFV) behaviour in infants following PHCA to determine if hypoperfusion persisted in the paediatric intensive care unit (PICU). Ten patients undergoing CHD surgery were divided, based on the pump modality employed, into either mild hypothermic CPB or profound hypothermic CPB with circulatory arrest. Following admission to the PICU, sequential recordings of the mean CBFV in the middle cerebral artery, anterior fontanelle pressure, haemodynamic variables, tympanic membrane temperature, haematocrit and PaCO2 were performed. The PHCA group had a consistently reduced CBFV compared with the control group (P < 0.05). The CBFV values at one, two and four hours were 60 +/- 11, 51.8 +/- 11.4 and 52.6 +/- 11.9 respectively in the mild hypothermic CPB group. The CBFV values at one, two and four hours were 26.6 +/- 6.8, 32.6 +/- 10 and 34 +/- 8 respectively in the PHCA group. There was no difference in cerebral perfusion pressure between both groups. Tympanic temperature, haematocrit and PaCO2 did not vary between groups at any interval. This study demonstrates a sustained reduction in the CBFV pattern following PHCA into the postoperative period despite adequate cerebral perfusion pressures. This abnormality correlates with electroencephalographic aberrations documented after PHCA. It supports the concept of a prolonged unreactive cerebrovascular bed which could potentially contribute to the acute neurological morbidity following PHCA in neonates.