Hyperbaric levobupivacaine versushyperbaric ropivacaine in spinal anaesthesiafor lower limb surgeries-a randomized control trial

Spinal anaesthesia has severalbenefits as it provides prolonged post-operative analgesic effect, has rapid onsetand offset, easy administration, is pocket friendly, reliable, safe, patient isawake unlike in general anaesthesia and there is decreased risk of aspiration.

Earlierhyperbaric solutions of Levobupivacaine and Ropivacaine were prepared in operatingroom but now hyperbaric solutions of these drugs are available in the market inconcentration of 0.5% and 0.75% respectively each combined with 80 mg of dextrose.The disadvantageof preparing these hyperbaric solutions in operating room was that density of eachnewly prepared solution was different, so the results could not be reproduced reliably.

Previousstudies by Casati used Levobupivacaine and Ropivacaine by adding dextrose (30mg)in operating room and the specific gravities of the Hyperbaric Bupivacaine was 1.00874g/ml,Hyperbaric Levobupivacaine was 1.00945g/ml and Hyperbaric Ropivacaine was 1.00876g/ml.6

This canbe compared with the newer preparations available of Hyperbaric Levobupivacainewhich has specific gravity of 1.025-1.035 and Hyperbaric Ropivacaine which has specificgravity of 1.025-1.035. The newer preparations of both Hyperbaric Levobupivacaineand Hyperbaric Ropivacaine contains 80mg dextrose in each ml and have similar specificgravity.

As earlier studies on hyperbaric ropivacaine and levobupivacaine,solutions used were prepared by addition of dextrose prior to administration,so baricity was unreliable with specific gravity unknown. Hence, in this study, we aim tocompare the efficacy of two newly available hyperbaric preparations of hyperbaricLevobupivacaine and hyperbaric Ropivacaine in lower limb surgeries.

Spinal Anaesthesia will be administered to thepatient in L2-L3 interspace with patient sitting using a midline approach using25G spinal needle. According to randomization, patient will receive either preservativefree formulation of hyperbaric ropivacaine 0.75% (3ml) or hyperbaric levobupivacaine0.5% (3ml). No adjuvant medication will be added to either local anaesthetic.

After completion of the spinal injection, patientwill be immediately made to lie supine with operating table horizontal. The patientwill be evaluated for sensory and motor block, for every 2 minutes for first 20minutes, every 3 minutes for next 30 minutes, every 10 minutes for 60 minutes, andfinally every 15 minutes until the sensory block has regressed to S1 dermatome.

The patient will be administered Inj. Midazolam1mg iv after spinal Anaesthesia has been given. During the surgery the patient’spulse, Systolic Blood pressure, Diastolic Blood pressure, Mean Arterial Pressure,heart rate will be recorded every 3 minutes for 30 minutes and then every 5 minsfor next 30mins and then 15mins until completion of the surgery.

The sensory level of the block will be assessedin a caudal to cephalad direction, using loss to pin prick sensation, and the C5-C6dermatome is used as an unblocked reference point.

 The motor Block will be assessed using the ModifiedBromage Scale.Readiness for surgery is defined as loss of pinprick sensation ≥ T10 with modified Bromage≥2. During surgery, evaluation of themotor block will be suspended until the end of the procedure. If the patient complainsof pain, Inj Butorphanol 1 mg I.V. will be administered. If additional sedationis needed, midazolam 1 mg I.V. will be administered. The total dose of any givenmedication will be recorded. If the patient still feels pain, general anaesthesiawill be provided and the case will be excluded from the study. Any complications,side effects and adverse effects up to 24 hours postoperatively will be noted.