Comparative Evaluation of Classical Subarachnoid Block, Unilateral Subarachnoid Block and Low-Dose Subarachnoid Block in High-Risk Patients Undergoing Lower Limb Surgeries

Abstract

BACKGROUNDSubarachnoid block is a popular anaesthetic technique because of its rapid onset, safety and simplicity. A special technique of subarachnoid block named spinal hemi-block was described for one-limb surgeries, which was also known as spinal hemianalgesia or unilateral spinal anaesthesia. Addition of fentanyl to bupivacaine is an established technique to reduce the dose of anaesthetic and to maintain haemodynamic (1) stability. FACTORS AFFECTING UNILATERAL SPINALFive main factors should be considered when trying to restrict spinal block (2) to the operative side. 1. The density of local anaesthetic solution compared with CSF. AIMTo compare the efficacy of classical subarachnoid block using 0.5% bupivacaine, unilateral subarachnoid block using 0.5% bupivacaine and low-dose subarachnoid block using 0.5% bupivacaine 1.5 mL with 0.5 mL of fentanyl (2) (25 micrograms) in highrisk patients undergoing unilateral lower limb surgeries (6) based on the following parameters. 1. Haemodynamic stability in the intraoperative period. 2. Onset and Quality of subarachnoid block. MATERIALS AND METHODSA total of 60 high-risk patients undergoing surgery on one lower limb were divided into three groups. Control Group-Received 2 mL of 0.5% Bupivacaine intrathecally and turned to supine position immediately. Study Group I: Received 1.5 mL of 0.5% Bupivacaine with 25 µg (0.5 mL) Fentanyl intrathecally and kept in lateral decubitus position for 10 minutes and then turned supine. Study Group II: Received 2 mL of 0.5% Bupivacaine intrathecally and kept in lateral decubitus position for 10 minutes and then turned supine. Heart rate, Systolic and Diastolic blood pressure were recorded before and after the spinal every five minutes for 60 minutes and in the recovery room and thereafter every 30 minutes till the time oral analgesic was given. Sensory blockade was assessed in the dependent as well as non-dependent limb separately. Using Modified Bromage scale, both the dependent as well as non-dependent limbs were assessed separately for the motor blockade at 0, 5, 10, 15 and every 5 minutes after surgical position. Side effects such as nausea, vomiting, and pruritus were recorded in the intraoperative and postoperative period. RESULTSThe occurrence of hypotension requiring treatment was more in the control group (30%) versus Study Group I(15%) and Study Group II(15%) which is statistically significant(p<0.02). The occurrence of bradycardia requiring treatment was more in the Control group (30%) versus Study Group I(15%) and Study Group II(15%) which is statistically significant (p<0.02). An analysis of motor blockade in the 3 groups showed that Study Group I and Study Group II produced lesser degree of motor blockade when compared to the Control Group. This difference was found to be statistically significant (p<0.05). CONCLUSIONWe conclude that in high-risk patients undergoing unilateral lower limb surgeries: 1. Unilateral low-dose subarachnoid block offers better haemodynamic stability during the intraoperative period. 2. ...