Background: The dosage of local anaesthetic and the time the patient m
ust be kept in the lateral decubitus position for a unilateral spinal
anaesthesia is not known. The aim of this study was to determine the i
deal dosage of hyperbaric bupivacaine and the time required for the la
teral decubitus position for a unilateral spinal block. Methods: Ninet
y patients who were scheduled to receive spinal block for surgery in t
he lower extremity were randomised into 9 groups (n=10). The spinal bl
ock was performed through the L-4-L-5 intervertebral space with the pa
tient in the lateral decubitus position. Patients in groups Ia, Ib, Ic
; IIa, IIb, IIc; IIIa, IIIb, IIIc received 1.5 ml of 0.5%, 2 ml of 0.5
%, and 2.5 ml of 0.5% hyperbaric bupivacaine solutions, respectively.
The patients were turned to the supine position for 5 min after the in
jection in groups Ia, IIa, IIIa, 10 min after the injection in groups
Ib, IIb, mb, and 15 min after the injection in groups Ic, IIc, IIIc. T
he onset and regression of sensory and motor block were checked and co
mpared between the dependent and non-dependent sides in each group. Re
sults: The rate of block progression of the non-dependent side was hig
her in the groups receiving 2.5 ml 0.5% hyperbaric bupivacaine solutio
n than in the other groups; at the same time the level of block was hi
gher and the duration of block was longer. The incidence of hypotensio
n was 10-20% in these groups. In the 2 ml 0.5% hyperbaric bupivacaine
solution groups, a satisfactory block level and duration of anaesthesi
a for surgery was obtained. The rate of block progression to nondepend
ent side in the groups receiving 1.5 ml of 0.5% hyperbaric bupivacaine
solution was lower than the other groups, but the duration of block w
as shorter and the level of block was lower than the other groups. Con
clusion: For unilateral spinal anaesthesia in lower extremity operatio
ns, 2ml 0.5% hyperbaric bupivacaine solution for operations above the
knee and 1.5 ml 0.5% hyperbaric bupivacaine solution for operations be
low the knee and keeping the patients for 10 min in the lateral decubi
tus position were found to be appropriate.