ESTIMATION OF CEREBRAL BLOOD-FLOW AT BEDSIDE BY CONTINUOUS JUGULAR THERMODILUTION

The Kety-Schmidt technique can be regarded as the reference method for the measurement of cerebral blood flow (CBF). However, the method is somewhat cumbersome for routine use in the intensive care unit (ICU) a t the bedside. The continuous thermodilution technique developed many years ago for the measurement of coronary sinus blood flow can be appl ied for the measurement of jugular blood now (JBF). However, the measu rement of JBF by thermodilution has never been validated using the Ket y-Schmidt reference method. We first validate the continuous thermodil ution in vitro by comparison with a volumetric flow. The thermodilutio n method is accurate for flows between 50 and 900 ml min(-1) with a me an difference volumetric-thermodilution flow of -1 +/- 18 ml min(-1) ( mean +/- SD), and precise with a coefficient of variability ranging be tween 1.21% and 2.50%. In vivo accuracy was assessed by comparing in 1 5 comatose patients CBF measured using the Kety-Schmidt (CBFKS) method and estimated from JBF measured by thermodilution (CBFTH) at four lev els of arterial P(a)co(2) (25, 30, 35, and 40 mm Hg). The mean differe nce CBFKS - CBFTH is -0.9 +/- 3.6 ml min(-1) 100 g(-1). In vivo precis ion of the method was good, with a coefficient of variability of 4.1% in mean. We conclude that jugular continuous thermodilution technique is a reliable method for estimating CBF at the bedside. This technique allows repeated measurements jugular bulb blood sampling for brain me tabolic studies.