CSF pressure measurement during anesthesia: an unreliable technique

Background: The measurement of cerebrospinal fluid (CSF) pressure is necessary for many clinical indications. Its accuracy may be compromized in frightened or uncooperative children who find it difficult to relax sufficiently. The aim of the present study was to evaluate possible effects of general anesthesia on CSF pressure values. Methods: Lumbar puncture was performed under general anesthesia in 15 patients aged 4.5-20 years for the evaluation of headaches associated with a swollen optic nerve. Cerebrospinal fluid pressure was measured with a manometer when the patient was fully anesthetized (opening pressure) and then continuously recorded until the patient regained consciousness. The opening pressure was compared with the lowest pressure measured at the termination of the procedure (end-measurement pressure). Results: Seventeen pressure measurements were performed in 15 patients. In all but two measurements, differences were noted between the opening and end pressure, ranging from 5 to 13 cmH(2)O. The opening pressure was abnormally high in 16 measurements, and the end pressure was abnormally high in seven. The difference between the two measurements was highly significant (P < 0.001). Conclusions: Lumbar puncture performed under general anesthesia may yield two pressure measurements. Many factors, such as hypercarbia and the anesthetic agent used, may influence the results. Owing to the dynamic changes in CSF pressure, measurements made under anesthesia may be unreliable.