Fentanyl increases cerebrospinal fluid pressure in normocapnic volunteers

In a double blind randomized study, the effect of fentanyl 1 microgram kg-1 i.v. or placebo on mean lumbar cerebrospinal fluid pressure (CSFP), mean arterial pressure, cerebral perfusion pressure, transcutaneous PCO2 and heart rate was studied in 10 spontaneously breathing volunteers in the lateral decubitus position via a 22-gauge spinal needle inserted into the subarachnoidal space at level L3/L4. Fentanyl increased mean CSFP (+/- SD) from 12.4 +/- 2.7 mmHg to 16.0 +/- 2.3 mmHg (P < 0.05) without significant changes in the other variables. No significant changes in any of the measured variables were seen after administration of placebo. Cerebral perfusion pressure decreased significantly after fentanyl (P < 0.05).