Cerebrospinal fluid concentrations of propofol during anaesthesia in humans

The concentration of propofol in and surrounding the human brain during pro pofol anaesthesia is unknown. We measured simultaneously the concentration of propofol in cerebrospinal fluid (CSF) from an indwelling intraventricula r catheter and the concentration in arterial blood in five neurosurgical pa tients before, during induction (at 2.5 and 5 min) and during a maintenance propofol infusion (at 15 and 30 min). After induction of anaesthesia with propofol 2 mg kg(-1), anaesthesia was maintained with an infusion of 8 mg k g(-1) h(-1) for 15 min and then reduced to 6 mg kg(-1) h(-1). The plasma co ncentration of propofol increased rapidly during induction and reached a pl ateau concentration of mean 2.24 (SD 0.66) mu g ml(-1) after 5 min. The con centration of propofol in CSF showed a slower increase during induction and remained almost constant at 35.5 (19.6) ng ml(-1) at 15-30 min after induc tion. The CSF concentration of propofol that we measured was 1.6% of the pl asma concentration and consistent with the high protein binding of the drug in plasma.