Cerebral oxygenation during paediatric cardiac surgery: identification of vulnerable periods using near infrared spectroscopy.
OBJECTIVE
Neurologic sequelae remain a well recognised complication of paediatric cardiac surgery. Monitoring of cerebral oxygenation may be a useful technique for identifying vulnerable periods for the development of neurologic injury. We sought to measure regional cerebral oxygenation in children undergoing cardiac surgery using near infrared spectroscopy to ascertain such vulnerable periods.


METHODS
Observational study of 18 children (median age 1.3 years) undergoing cardiac surgery (17 with cardiopulmonary bypass, 8 with circulatory arrest). Regional cerebral oxygenation was monitored using the INVOS 3100 cerebral oximeter and related to haemodynamic parameters at each stage of the procedure.


RESULTS
Prior to the onset of bypass, 10 patients had a decrease in regional cerebral oxygenation of > or = 15% points, reaching an absolute haemoglobin saturation less than 35% in 5 cases. The most common cause was handling and dissection around the heart prior to and during caval cannulation. With institution of bypass, regional cerebral oxygenation increased by a mean 18% points to a mean maximum of 75%. During circulatory arrest regional cerebral oxygenation decreased with rate of decay influenced by temperature at onset of arrest (0.25%/min at < 20 degrees C; 2%/min at > 20 degrees C). Reperfusion caused an immediate increase in regional cerebral oxygenation followed by a decrease during rewarming. Discontinuation of bypass caused a precipitous decrease in regional cerebral oxygenation in 5 patients, reaching less than 50% in 3 patients.


CONCLUSIONS
These observations suggest that the pre- and early post-bypass periods are vulnerable times for provision of adequate cerebral oxygenation. Near infrared spectroscopy is a promising tool for monitoring O2 supply/demand relationships especially during circulatory arrest.
Daubeney
P E
PE
Wessex Cardiothoracic Centre, Southampton General Hospital, UK.
Smith
D C
DC
Pilkington
S N
SN
Lamb
R K
RK
Monro
J L
JL
Tsang
V T
VT
Livesey
S A
SA
Webber
S A
SA
D001921:Brain / Q000378:metabolism*; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D002648:Child; D002675:Child, Preschool; D005260:Female; D006324:Heart Arrest, Induced; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007432:Intraoperative Period; D008297:Male; D008991:Monitoring, Physiologic; D010092:Oximetry; D010100:Oxygen / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared
D010100:Oxygen