BACKGROUND: Arterial hypotension secondary to a sympathectomy from a spinal block remains to be a major concern among anesthesiologists. Preloading and use of vasoconstrictor agents have been used to prevent this. The modification of level of blockade through position change will be explored in this study METHODS: A randomized double-blind study was done to evaluate the effects of prolonged lateral positioning on the spread of block and hemodynamic variables after spinal anesthesia with hyperbaric tetracaine. Two hundred twenty five (n=225) ASA PS I-III patients for unilateral lower limb surgery under spinal anesthesia were given tetracaine 0.6 percent heavy with volume adjusted to height. The patients were randomized into 3 groups: Group I (conventional, n=75)were placed supine immediately after spinal injection; Group 11 (n=75) were maintained for 10 minutes in the lateral position before being turned supine; and Group III (n=75) remained for 15 minutes then turned supine. Dermatomal sensory levels and degrees of motor block for both dependent and nondependent sides were recorded for all the groups as well as the incidence of hypotension and bradycardia RESULTS: The study showed that although there were few patients with complete unilateral block in the 10-(n=4) and 15-minute (n=6) groups, the maximum height of sensory level attained as well as the maximum degree of motor block effected were significantly higher on the dependent side for both experimental groups than the nondependent side (P0.001). The conventional patients all showed equal bilateral distribution of spinal block. The time to onset, two-segment regression of sensory block, and one-degree regression of motor block were significantly faster in the conventional group than the experimental groups (P0.001). The incidence of hypotension in both 10-minute (13 percent) and 15-minute groups (5 percent) were significantly lower than in the conventional group (39 percent). The conventional group also had greater mean systolic and diastolic blood pressure changes from the baseline (P0.001). No significant difference was noted in the incidence of bradycardia among the groups (P0.05). CONCLUSION: Prolonged lateral positioning with hyperbaric tetracaine produces asymmetric spinal blockade and effectively reduces the incidence of adverse hemodynamic effects such as hypotension in both the 10-minute and 15-minute groups. (Author)
Human ; HYPOTENSION ; ANESTHESIA ; SPINAL, SURGERY ; ANESTHESIA, LOCAL