Background: To evaluate if the speed of intrathecal injection affects the lateral distribution of spinal block during unilateral spinal anaesthesia with 1% hyperbaric bupivacaine.
Design: prospective, randomized, double-blind study.
Setting: anaesthesia Department at a University Hospital.
Patients: 30 ASA physical status I-II patients, scheduled for elective orthopedic surgery involving one lower limb only (ankle and foot surgery).
Interventions: after placing the patients in the lateral decubitus position with the site to be operated on dependent, dural puncture was performed at L3-L4 interspace using a 25-Gauge Whitacre spinal needle. After the needle hole had been turned toward the dependent side, patients were randomized to receive 8 mg of 1% hyperbaric bupivacaine injected over either 40 sec (Group SLOW, n = 15) or 3 sec (Group FAST, n = 15). The lateral position was maintained for 15 min.
Measurements: a blind observer evaluated the evolution of sensory (pinprick test) and motor (modified Bromage scale) blocks on both the dependent and nondependent sides until the regression of motor block by one degree.
Results: No differences in the maximal sensory level on both the dependent and nondependent sides were observed in the two groups. Unilateral sensory block was onserved in 6 patients in group SLOW (40%) and in 5 patients in group FAST (33%), (p = not significant[NS]. Unilateral motor block was observed in 9 patients in group SLOW (60%) and in 10 patients in group FAST (66%) (NS).
Conclusions: Extremely reduced speeds of intrathecal injection did not improve the lateral distribution of spinal block when injecting 8 mg of 1% hyperbaric bupivacaine through a pencil-point directional spinal needle.