Is cerebral blood flow/metabolic mismatch during rewarming a risk factor after profound hypothermic procedures in small children?
The relation between cerebral blood flow and oxygen consumption was studied in six children during cardiac operations with profound hypothermia. A combination of topical cooling and core cooling was used to reduce the nasopharyngeal temperature to 15 degrees C. The alpha-stat principle for pH management was used. Blood flow and oxygen consumption decreased significantly with temperature. At a nasopharyngeal temperature of 15 degrees C, blood flow was reduced to 25% of the awake level, corresponding to 34% of the asleep value obtained 15-30 min after intubation. Oxygen consumption decreased to 25% of the asleep value. During stable profound hypothermia, venous saturation in the jugular bulb was at the same level as 15 min after intubation (70%). Markedly lower values were observed during topical cooling, and particularly during rewarming (down to 21%), indicating a mismatch between cerebral blood flow and oxygen consumption. The speed of rewarming correlated with the fall in venous oxygen saturation (rs = 0.82, P less than 0.05). It is suggested that periods of cerebral blood flow/metabolic mismatch during topical cooling and rewarming may explain postoperative cerebral dysfunction after deep hypothermic procedures. A moderate speed of rewarming is advocated.
van der Linden
J
J
Brompton Hospital, London, UK.
Ekroth
R
R
Lincoln
C
C
Pugsley
W
W
Scallan
M
M
Tydén
H
H
D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D002675:Child, Preschool; D006330:Heart Defects, Congenital / Q000601:surgery*; D006801:Humans; D007036:Hypothermia, Induced; D007223:Infant; D007231:Infant, Newborn; D010101:Oxygen Consumption; D012044:Regression Analysis; D012307:Risk Factors