Intrathecal Injection of Hyperbaric Bupivacaine Versus a Mixture of Hyperbaric and Isobaric Bupivacaine in Lower Abdominal Surgery: A Randomized Controlled Trial

Background: Bupivacaine hydrochloride is widely used as the primary drug for spinal anesthesia. Objectives: This research aimed to evaluate the intrathecal administration of both isobaric and hyperbaric bupivacaine (HB) in lower abdominal surgery. Methods: A randomized, controlled, double-blind trial was conducted on 50 patients classified as American Society of Anesthesiologists (ASA) class I to II, scheduled for lower abdominal surgery under spinal anesthesia. The patients were allocated randomly into two groups of similar size. Group A (control group) received 20 mg HB 0.5% intrathecally. Group B (case group) received 10 mg HB 0.5% and 10 mg isobaric bupivacaine (IB) 0.5%. Results: There was a significant decline in heart rate and mean arterial pressure in Group A compared to Group B (P < 0.05). Group A had a significantly greater sensory level at 10 and 20 minutes than Group B (P = 0.008 and 0.006, respectively). Group A had an earlier duration in reaching Bromage 3 and the first need for analgesia, compared to group B (P = 0.001 and 0.003, respectively). Conclusions: In lower abdominal surgery, the intrathecal administration of HB with IB increased hemodynamic stability and duration of both sensory and motor blockade but with slower recovery from anesthesia compared to HB alone.