A comparative study of 0.5%  Hyperbaric Levobupivacaine, 0.5%  Hyperbaric Bupivacaine and 0.75% Hyperbaric Ropivacaine for spinal anesthesia in perianal surgeries: A randomized control trial                                                                                                                                                                  

Spinal anaesthesia is the most efficient technique that provides fast surgical anaesthetic block through very small dose of local anaesthesia into the subarachnoid space. It produces profound nerve block to large part of the body. However, the control of spread of local anaesthetic through the CSF to provide block that is adequate for the proposed surgery is a challenge. Bupivacaine is a racemic mixture containing equal proportions of S and R isomers. It is being used because of its long duration of action and beneficial sensory and motor block. However this might be a disadvantage for short to intermediate duration procedures. Levobupivacaine is S enantiomer of bupivacaine and better alternative to bupivacaine in terms of cardiac and central nervous system toxicity .It produces less motor block than bupivacaine when administered intrathecally at low doses. Ropivacaine is less lipophilic than bupivacaine and has less affinity towards large myelinated motor fibers resulting in relatively reduced motor blockade.This feature of high sensory and low motor affinity is advantageous in cases where motor blockage isn’t desired. Perianal surgeries are short procedures that require good intra operative anesthesia and post operative analgesia since perianal region have dense sensory supply. Hence profound sensory block over motor block for short period is desired. This study will be done to compare the duration of sensory and motor blockade of 0.5% hyperbaric bupivacaine, 0.5% hyperbaric levobupivacaine and 0.75% hyperbaric ropivacaine. This study will include 69 ASA 1 and ASA 2 patients between the age group of 18 to 65 years undergoing perianal surgeries. Patients will be divided into 3 groups (23 each)  randomly via computer generated sequence. A detailed preanesthetic evaluation and all relevant investigations will be done a day prior to surgery. All patients will be informed about the anaesthetic procedure and an informed consent will be taken for the same. Patients will be kept nil per oral- 6 hours for solids and 2 hours for clear liquids. Tablet Alprazolam 0.25mg will be given the night before the surgery and Tablet Pantoprazole 40 mg morning of the surgery. All patients will have a patent 20 Gauge intravenous peripheral line and will be preloaded with 500 ml of Ringer lactate solution.On the day of surgery, baseline vitals will be recorded. The patients will be monitored using standard monitors - Pulse Oximeter, Electrocardiogram (ECG) and Noninvasive Blood Pressure (NIBP).Under strict aseptic precaution, patient in sitting  position, local anesthesia of skin will be given with 2ml of 2% lignocaine at L2-3 or L3-4 intervertebral space. Lumbar puncture will be done using 25G Quincke Babcock spinal needle. The drug will be injected slowly after confirming free and clear backflow of CSF. After injecting the drug, the patient will be made to sit for 1minute and then lie down in supine position. The primary outcome variable will be the duration of sensory and motor blockade. This will include the time taken for two segment regression and degree of block assessed by Modified Bromage scale. The secondary outcome will be to compare the onset of sensory and motor blockade. This will be assessed by time taken for the block to reach T12 and modified Bromage of 4.Any adverse hemodynamic effects will be added as secondary variable.The data collected will be tabulated for statistical analysis