Effectiveness of intrathecal buprenorphine versus butorphanol as adjuvant in 0.5 percent levobupivacaine in lower limb surgeries.

This prospective, randomized, double blind study will be conducted after approval from the institutional ethics committee and informed written consent of patients will be taken. A study of 105 patients, aged 18-60 years, belonging to ASA physical status 1 or 2 and scheduled for elective lower limb orthopedic surgeries will be randomized into three groups using random numbers generated by the computer. Patients in group A (Gp A) will receive 2.8 ml of 0.5% hyperbaric levobupivacaine with 0.2 ml (containing 20 μg) butorphanol, a total volume of 3 ml intrathecally. Similarly, 60 μg of buprenorphine will be added to 2.8 ml of 0.5% hyperbaric levobupivacaine to make a total volume of 3 ml to be given intrathecally to patients in group B (Gp B) and Group C (Gp C) will receive 0.5% heavy levobupivacaine with preservative free NS to make total volume of 3ml.

All patients will undergo a complete general physical examination and systemic examination and will be explained the linear visual analogue scale (LVAS) scoring system for pain during the pre-anaesthetic check-up. The LVAS used is a 11-cm line where 0 denote “no pain” while 10 denote “worst pain imaginable”.

Patients in whom spinal anaesthesia or the study drugs are contraindicated will be excluded from the study. Patients with neurological disease, spinal deformities, local skin infection or mental disorders; those who were morbidly obese, hemodynamically unstable or had coagulation disorders, or patients with liver disease, impaired renal functions, ASA Physical status >2 or a history of opioid dependence will also be excluded from the study.

Patients will be kept fasting for 8 hours to solids and 4 hours to clear fluids preoperatively and receive no premedication. In the operation theatre, an intravenous line will be established. The intrathecal drugs will be prepared by a trained pharmacist beforehand to maintain the blinding process. Baseline heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), respiratory rate (RR) and peripheral arterial oxygen saturation (SpO2) will be recorded for all subjects. All patients will receive 10 ml/kg of ringer lactate solution as preload within 20- 30 minutes. The primary investigator will enter the operation theatre after this period and will be blinded to the patient allocation. All spinal blocks will be given by the same anaesthesiologist. Subarachnoid block will be performed under strict aseptic conditions in the sitting position with neck flexed at the level of L 3-4 inter vertebral space using 25 G Quincke’s spinal needles. The midline approach will be used to perform the spinal blocks after infiltrating the skin with 2% Lidocaine. The test drug will be injected over 15 seconds. Following the subarachnoid block, the patient will be put in supine position.

Intraoperatively, HR, SBP, DBP, RR and SpO2 will be recorded at 3 minutes (min) intervals for the first 30 min from the time of injection of spinal solution and there after every 15 min for the complete period of surgery. This data will be recorded by the attending anaesthesiologist and the primary investigator, who were unaware of the patient allocation. Hypotension (MAP <60 mmHg) will be treated with fluid boluses and 6 mg intravenous (IV) boluses of ephedrine, while bradycardia (HR <50bpm) will be treated with 0.6 mg IV atropine. Respiratory depression is defined as a respiratory rate <8 breaths/min or a SpO2 of <90% on room air. All patients will be given supplemental O2 via face mask at 6 l/min if the SpO2 decreased below 90%.

The highest level of sensory block will be determined in the midclavicular line bilaterally, by pinprick test using a 20-G hypodermic needle every 2 min till the level has stabilized for four consecutive tests. The highest level of sensory block and the time taken to attain it from the time of the intrathecal injection will be recorded. Further sensory testing will be performed at 20-min intervals till the recovery of S2 dermatome. Motor block will be assessed using the modified Bromage scale (grade 0 = no motor block; grade 1 = inability to raise extended legs, able to move knees and feet; grade 2 = inability to raise extended leg and move knee, able to move feet and grade 3 = complete motor block of the lower limbs) till achievement of the highest sensory level; at the end of the surgery and then at 30 min intervals till the patient has no motor blockade.

Side effects such as hypotension, bradycardia, nausea, vomiting, sedation, pruritis, shivering and respiratory depression were recorded. The time to voiding will also be recorded. The quality of postoperative analgesia will be assessed using LVAS at 15 min, 30 min and thereafter every 30 min, till 2 hours postoperatively; and then every hour, till 4 hours postoperative duration. The time of first request of rescue analgesia will be recorded. Patients reporting an LVAS score of ≥4 will be treat with 15mg/kg PARACETAMOL IV infusion, as rescue analgesic.

The data will be compiled using Microsoft excel (2019) and will be analyzed using paired/unpaired t tests and Fisher’s exact tests on the Epi Info software (version 8.0) to assess the statistical difference between the groups. A P value of <0.05 will be accepted as statistically significant.