Cerebrospinal fluid catecholamine levels and duration of spinal anaesthesia.

The effects of catecholamines added to dibucaine on the duration of spinal anaesthesia and cerebrospinal fluid catecholamine levels were studied. Free norepinephrine levels increased from 0.107 ng.ml-1 before anaesthesia to 5.8 ng.ml-1 and 1,238 ng.ml-1 after 1.0 microgram or 100 micrograms norepinephrine had been added to the local anaesthetic. The effects of 2.5 micrograms of either norepinephrine or epinephrine added to dibucaine on the duration of motor blockade and sensory regression time were compared. The duration of both were significantly prolonged by added norepinephrine from 96 +/- 17 min to 193 +/- 20 min (sensory blockade) and from 116 +/- 14 min to 204 +/- 34 min (motor blockade), but were not changed by addition of epinephrine. These data suggest that a 2.5 micrograms dose of norepinephrine is sufficient to prolong the duration of spinal anaesthesia and more effective than the same dose of epinephrine.