Spinal anaesthesia for pelvic surgery: low concentrations of lignocaine and bupivacaine are effective with less adverse events.

BACKGROUND The aim of this study was to compare the clinical efficacy of 5% lignocaine, 2.5% lignocaine, 0.5% bupivacaine and 0.25% bupivacaine in subarachnoid block for pelvic surgeries. METHODS 80 adult ASA grades I and II patients of either sex between the ages of 18-60 yrs, undergoing routine pelvic surgery of short duration were included in this prospective, randomized double blind study. Patients were allotted by computer generated random number table into 4 groups of 20 patients each. Group A (n = 20): injected with 2 ml of 0.5% hyperbaric bupivacaine Group B (n = 20): injected with 2 ml of 0.25% hyperbaric bupivacaine Group C (n = 20): injected with 5% hyperbaric lignocaine Group D (n = 20): injected with 2.5% hyperbaric lignocaine The following parameters were measured every five minutes till 60 minutes and then every 15 minutes till recovery. 1. Onset of sensory block assessed by pin prick method bilaterally at middle of the shin. Maximum height of sensory block noted. 2. Onset of motor block assessed by inability to raise the leg. 3. Duration of sensory block judged as time to first postoperative analgesic requirement by the patient. 4. Duration of motor block assessed by return to Bromage scale of 1. 5. Non invasive blood pressure (NIBP) and Heart Rate- 6. Complications if any were noted -nausea, vomiting, headache, transient neurological symptoms Statistical analysis was done with Kruskal-Wallis, Mann-Whitney tests and ANOVA test. RESULTS The groups were comparable with respect to age, weight and male to female ratio (p <0.05). Time to onset of sensory block in seconds in groups A, B, C and D was 79.5 +/- 52.26, 104.24 +/- 24.53, 33.6 +/- 14.98 and 62.50 +/- 25.05 respectively. 5% lignocaine was observed to have statistically. significant shortest onset of sensory block compared to other three groups (p <0.05). The mean onset of motor block in seconds was 137.25 +/- 60.92, 240.75 +/- 73.31, 62.30 +/- 24.56, 119.5 +/- 56.51 sec in Groups A, B, C and D respectively with 5% lignocaine observed to have statistically significant fastest onset of time compared to the other groups (p <0.05). The upper dermatomal height reached was T8 or T9 in groups A, C & D. However in group B, the upper dermatomal height reached was T 10. Duration of sensory block in minutes was 172.5 +/- 49.64, 146 p.00 +/- 35.87, 105.9 +/- 31.68 and 133.6 +/- 17.68 in groups A, B, C & D respectively. 0.5% bupivacaine was observed to have the longest duration of sensory block compared to both the groups of lignocaine (p <0.01). The duration of motor block m minutes was 159.25 +/- 53.49, 137.4 +/- 15.71, 100.5 +/- 21.81, 110.0 +/- 27.76 respectively in groups A, B, C & D. The duration of motor blockade with 0.5% bupivacaine was significantly more as compared to 5% and 2.5% lignocaine (p <0.005). Nine, one, twelve and four boluses of intravenous boluses of ephedrine were required in Groups A, B, C & D respectively. Most of the boluses were required after 30 minutes in Group A as compared to 5% lignocaine wherein the doses were required in the initial 30 minutes post spinal. Four boluses each of intravenous atropine 0.3 mg were required in 0.5% and 0.25% bupivacaine which was not statistically significant amongst the four groups. Significantly more patients in 0.5% bupivacaine required intravenous boluses of ondansetron 4 mg; five in Group A, one each in Group B and C and none in Group D (p <0.05). None of the atients showed transient neurological symptoms till 5 days postoperatively. None of the patients of this series developed post spinal headache at any time till discharge of the patient from the hospital (8-1 0 days). CONCLUSION [corrected] For subarachnoid block for pelvic surgeries longer than two hours 0.25% bupivacaine is a better choice as compared to 0.5% bupivacaine. However for short duration surgeries lasting up to one hour, 2.5% lignocaine is a better choice as compared to 5% lignocaine as the lower concentrated solutions of bupivacaine and lignocaine are more haemodynamically stable compared to their higher concentrations and with similar duration of ensory and motor block.