A prospective randomized comparative study of hyperbaric ropivacaine 0.75% versus hyperbaric bupivacaine 0.5% in spinal anaesthesia for elective infraumbilical surgeries

The duration of the sensory block with ropivacaine is found to be similar with bupivacaine and the motor block was significantly shorter. Due to less lipophilic property and stereo selective structure ropivacaine has significantly higher threshold for cardio toxicity and CNS toxicity than bupivacaine. As hyperbaric ropivacaine is now commercially available we plan to study its efficacy and safety compared to the routine hyperbaric bupivacaine in patients undergoing spinal anesthesia for elective infraumbilical surgeries. Anesthesiology resident (blinded to the study) will examine the patients preoperatively to ensure that the inclusion criteria is met. Informed consents will be taken of the eligible participants, and they will be kept nil per oral for solids 6 hours and for liquids 2 hours prior to the surgery. Patients will be allocated into two groups - Group B receiving - 5% hyperbaric  bupivacaine and Group R - receiving 0.75% hyperbaric ropivacaine.Onset of analgesia at T10 will be noted. The sensory level will be checked every 2 minutes as described above until the level does not ascend any further for 4 consecutive readings. Sensory level will be checked every 5 minutes thereafter till the end of 1 hour, and every 15 minutes thereafter till 2-segment regression and sensory recovery (around S2-S4 segments) occur. Motor blockade will be assessed by modified Bromage scale (0-1-2-3) at similar intervals as assessment of sensory block. Motor blockade will be evaluated at 2-minute intervals till a modified Bromage score of 3 is obtained or till maximum motor blockade is achieved. This time is noted as onset of motor blockade. The time at which ankle movement returns is noted to indicate recovery from motor blockade. Blood pressure will be recorded every 5 minutes for the first hour and every 15 minutes thereafter till complete sensory and motor recovery More than a 25% decrease in mean arterial pressure will be treated with intravenous fluids and vasopressor (mephentermine 3 mg/bolus). Heart rate will be recorded every 5 minutes for the first hour and every 15 minutes thereafter till recovery from sensory and motor blockade. A heart rate < 50/min will be considered as bradycardia but will be treated only if associated with hypotension. A respiratory rate less than 8/min or pulse oximetry values less than 95% on room air will be taken as significant and nasal oxygen 3 to 5 litres/min will used as rescue. Any adverse effects such as nausea, vomiting, pruritus will be noted. The inference concluded from the study shall enhance our knowledge about 0.75% hyperbaric ropivacaine and may lead to preferential selection of the drug.