A randomised study of lidocaine and prilocaine for spinal anaesthesia

Transient neurologic symptoms (TNS) are common after lidocaine-induced spinal anaesthesia (SA). Recent data indicate that TNS may be less frequent after prilocaine-induced spinal anaesthesia, for which reason the isobaric solution was compared with lidocaine.

One hundred patients scheduled for short urologic procedures under spinal anaesthesia were randomised to receive 80 mg prilocaine or lidocaine, both 20 mg/ml. The clinical course and the duration of anaesthesia were monitored. The following day an anaesthesiologist unaware of the randomisation interviewed the patients using a structured questionnaire.

Following prilocaine spinal anaesthesia the mean time until 2-segment regression was 123(SD 42) min and total sensory block lasted 221(49) min, compared to 106(26) and 181(48) min following lidocaine. TNS occurred in 7/49 patients in the lidocaine group and in 2/50 in the prilocaine group (ns).

TNS occurred also after isobaric prilocaine SA. The frequency was not significantly different from that following lidocaine SA but larger studies are needed to establish the relative risk of TNS following SA induced by the two local anaesthetics. Isobaric prilocaine has a longer duration of action than an equal dose of lidocaine and may be an alternative drug for spinal anaesthesia of intermediate or short duration.