Randomized Comparative Study to Assess the Efficacy of 0.5percentHyperbaric Bupivacaine 0.5percent Hyperbaric Levobupivacaine and 0.5percent Isobaric Levobupivacainefor Spinal Anaesthesia in total Knee Replacement Surgery

This is a double-blinded randomised comparative study involving 81patients between 18 and 70 undergoing elective total knee replacement surgery and is graded ASA grade [American Society of Anesthesiologists] I-III. After obtaining ethical approval from the institute and written informed consent from all patients, they will be randomly divided into three groups of 27 using a computer-generated table and the opaque envelope technique. Before undergoing anesthesia, every patient will undergo a pre-anesthetic evaluation.After transferring the patient to the operating table, we will attach monitors for ECG (electrocardiogram), Spo2 (peripheral capillary oxygen saturation), and NIBP (noninvasive blood pressure). Additionally, we will secure an 18-G intravenous catheter and administer 10 ml/kg of Ringer’s lactate to the patient over 10 minutes. Before anaesthesia, we will explain the sensory and motor assessment method to the patient. To perform a sub-arachnoid block, we will use a 25 G Quinke spinal needle and inject the 3 ml study drug slowly over 15 seconds (according to the group allocation] in the L3/L4 intervertebral space after confirming free-flowing cerebrospinal fluid. Patients will be placed in the supine position immediately after intrathecal injection. The surgical procedure can be initiated only after the sensory block of at least T12 level has been reached, along with a motor block of modified Bromage grade 2 or less. If these conditions are not met within 20 minutes, the spinal anaesthesia is considered unsuccessful, and the procedure will be converted to general anaesthesia.After injecting the intrathecal drug, the study parameters will be observed by an anaesthesiologist who is blinded to the type of drug given to the patient. The onset of the sensory block will be defined as the time taken for loss of sharp sensation with the pinprick test until the T12 dermatome level after injecting the drug (T1). The recordings will be noted every minute for the 20 min. The time taken to achieve adequate motor block (T2), defined as a score of 2 on the modified Bromage scale, will be recorded by testing the motor block every minute until a score of 2 is achieved. The motor blockade will be assessed using the modified Bromage scale (modified Bromage scale: 1 = unable to move feet or knees, 2 = able to move feet only, 3 = just able to move knees, 4 = full flexion of knees with detectable weakness of hip flexion while supine, 5 = no detectable weakness of hip flexion while supine, 6 = able to perform partial knee bend). Surgery will commence once adequate sensory (T12) and motor (modified Bromage 2) blocks are achieved. Maximum level of sensory block achieved will also be noted If there is inadequate sensory or motor block after 20 minutes, the patient will be excluded from the study. Patients undergoing surgery will be transferred to the post-anesthesia care unit for continuous monitoring. During this time, their sensory level and motor blockade will be checked every 10 minutes. The duration of the sensory block (T3) will be measured from the onset of the sensory block (T12 level) to the point of regression of the sensory block to the L4 dermatome. The duration of the motor block (T4) will be measured from the onset of the motor block (as defined by the modified Bromage scale 2) to the achievement of the modified Bromage scale six after the surgery. Additionally, the interval between administering the subarachnoid block and the patient’s first request for supplemental analgesia will be recorded (T5).Blood pressure and heart rate will be monitored every minute for the first 10 minutes and then every 5 minutes until the surgery is completed. If the systolic blood pressure (SBP) falls below 90 mmHg or there is a decrease of 20% or more from the baseline value, it will be considered a hypotensive episode. To manage hypotension, 250 ml of Ringer’s lactate will be infused quickly, and incremental doses of intravenous mephentermine, starting with 3 mg, will be given. Clinically relevant bradycardia, defined as a heart rate (HR) below 50 bpm, will be managed with incremental doses of 0.3 mg intravenous atropine. Total dose of atropine or mephentermine required will be noted. Side effects like hypotension, bradycardia, nausea and vomiting will be noted.