Cerebrospinal fluid pressure changes during the induction phase of anaesthesia

Cerebrospinal fluid pressure (CSFP) by lumbar puncture, systemic blood pressure (BP) and pulse rate (PR) were measured for 15 minutes during the induction phase of general anaesthesia in seven groups of six healthy female patients each. Intravenous drugs, thiopentopne 5 mg . kg-1, alfathesin 50 microliters . kg-1 and diazepam 0.5 mg . kg-1 given in 10 to 20 seconds caused a fall of CSFP and BP, whereas ketamine 2 mg . kg-1 and a three-minute induction with halothane three per cent, trichloroethylene one per cent, or methoxyflurane 0.75 per cent caused a sharp highly significant but short-lived rise of CSFP. Unlike ketamine, trichlorethylene and methoxyflurane, halothane caused a simultaneous significant fall of BP. To rule out apprehension as the cause of the rise of CSFP with inhalation agents a second challenge was given with similar concentrations of the vapours while patients were asleep. These still produced a sharp and significant rise of CSFP.