The relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass.
OBJECTIVE
Neurological impairment occurs in up to 25% of infants undergoing cardiopulmonary bypass with or without circulatory arrest. Potential causes include alterations in cerebral blood flow, hypoxia and embolisation. During cardiopulmonary bypass, arterial oxygen tension is maintained at levels which under normal conditions cause cerebral vasoconstriction; this is a potential mechanism for ischaemia. The aim of this study was to explore the relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass.


METHODS
Near infrared spectroscopy was used to explore the relation between arterial oxygen tension and cerebral blood flow in 14 patients (median age 8 months; range 1 month to 10 years 11 months). The relations between arterial oxygen tension, arterial carbon dioxide tension, temperature, haematocrit, pump flow rate, mean arterial pressure and cerebral blood flow, were examined using multivariate analysis.


RESULTS
There was no relation between cerebral blood flow and arterial oxygen tension, but a highly significant relation was observed between cerebral blood flow and pump flow rate, with cerebral blood flow decreasing 4.2-fold per L.m-2.min-1 decrease of pump flow rate.


CONCLUSIONS
There was no relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass, but low pump flow rate may lead to reduced cerebral blood flow.
Chow
G
G
Department of Neurosciences, Institute of Child Health/Great Ormond Street Hospital for Children, London, UK.
Roberts
I G
IG
Fallon
P
P
Onoe
M
M
Lloyd-Thomas
A
A
Elliott
M J
MJ
Edwards
A D
AD
Kirkham
F J
FJ
D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002545:Brain Ischemia / Q000503:physiopathology*; D002315:Cardiopulmonary Bypass; D002648:Child; D002675:Child, Preschool; D005260:Female; D006330:Heart Defects, Congenital / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D002534:Hypoxia, Brain / Q000503:physiopathology; D007223:Infant; D007431:Intraoperative Complications / Q000503:physiopathology; D008297:Male; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow / Q000502:physiology; D012307:Risk Factors; D014661:Vasoconstriction / Q000502:physiology
D010100:Oxygen