Effect of height-based spinal anesthetic dose versus conventional dose on hemodynamics in lower limb surgeries in geriatric patients: a randomized controlled trial

Background: An adequate dose of spinal anesthetic is very crucial in elderly surgical patients. The routine method to calculate the dose in a particular patient is usually based upon the weight of the patient, but the effect cannot always be predictable. We evaluated the efficacy and safety of the height-based dose of spinal anesthetic versus the conventional dose on intraoperative hemodynamics and spinal block characteristics in geriatric patients scheduled for lower limb surgeries. Methodology: This single-blinded, parallel-group, randomized, clinical trial enrolled 56 patients, aged 60 y or above who were scheduled for lower limb orthopedic surgeries under spinal anesthesia. The patients were randomly divided into two groups. In the height-based group, 0.06 mg of 0.5% hyperbaric bupivacaine/cm height of the patient was administered intrathecally. The control group received a fixed dose of 12.5 mg of 0.5% hyperbaric bupivacaine intrathecally. All patients received 25 mu g of fentanyl (0.1 mg / 2 ml) intrathecally. The incidence of hypotension was the primary outcome. The incidence of bradycardia, highest sensory level, onset and duration of sensory and motor block, incidence of shivering, the total dose of bupivacaine, total amount of fluid infused, vasopressors needed, and blood loss were the secondary outcomes. Results: The incidence of hypotension was significantly reduced in patients receiving height-based spinal dose compared to those in which standard dose was administered (57.1% vs. 82.1%, P = 0.042). The duration of sensory blocks was significantly shorter in height-based group compared to the control group (116 +/- 32.77 vs. 90.59 +/- 19.66 min; P = 0.001) as was the duration of the motor block (153.18 +/- 42 and 117 +/- 25.37 min; P < 0.001). Conclusion: In geriatric patients undergoing orthopedic lower limb surgery, the height-based dose of spinal anesthesia was effective and safe in reducing the incidence of hypotension with fast recovery from sensory and motor block.