Dose response study of lidocaine 1% for spinal anaesthesia for lower limb and perineal surgery.
OBJECTIVE
To compare the sensory and motor block produced by three different volumes of intrathecal lidocaine 1% and thereby determine the appropriate volume to administer for surgery of the lower limbs and perineum.


METHODS
Forty-eight patients scheduled for perineal or lower limb surgery were randomly assigned to receive 4, 6 or 8 ml lidocaine 1% intrathecally. The onset, spread, duration and regression of analgesia and motor block and side effects were evaluated (by a blinded observer whenever possible).


RESULTS
The maximum cephalad spread in the 6 ml (T8 +/- 3) and 8 ml (T4 +/- 1.7) groups were higher than the 4 ml group (T12 +/- 2.2, P < 0.01). In the 4 ml group, six patients (33%) did not achieve analgesia to T12 and four (22%) did not have complete motor blockade. Patients given 8 ml had longer duration of block (duration at T12: 104 +/- 23 vs 60 +/- 24, 67 +/- 14 min. P < 0.01: 8 ml vs 4, 6 ml) and slower recovery times (sensory recovery: 188 +/- 27 vs 142 +/- 27, 157 +/- 28 min. P < 0.01; 8 ml vs 4, 6 ml). Two patients (18%) from the 8 ml group and one (5%) from the 6 ml group had transient hypotension.


CONCLUSIONS
Four millilitres intrathecal lidocaine 1% is adequate for perineal surgery but for lower limb procedures, 6 ml is more appropriate as it consistently provides sensory analgesia above L1 dermatome and complete motor block. Eight ml gives an unnecessarily high block with higher incidence of hypotension.
Department of Anaesthesia, Tan Tock Seng Hospital, Singapore, Republic of Singapore. beng_ling_liam@notes.ttsh.gov.sg
B L
BL
Liam
C F
CF
Yim
J L
JL
Chong
D000328:Adult; D000775:Anesthesia, Spinal / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007866:Leg / Q000601:surgery*; D008012:Lidocaine / Q000008:administration & dosage / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009407:Nerve Block; D010147:Pain Measurement; D010502:Perineum / Q000601:surgery*
D000779:Anesthetics, Local; D008012:Lidocaine