Comparative efficacy of two doses of hyperbaric bupivacaine (10 and 12.5 mg) for unilateral spinal anesthesia in patients with lower limb wounds and uncompensated blood loss

BACKGROUND: Unilateral spinal anesthesia minimizes hemodynamic compromise in patients with blood loss, but the optimal dose of hyperbaric bupivacaine in this population remains undefined. AIM: To compare the efficacy of two doses (10 and 12.5 mg) of 0.5% hyperbaric bupivacaine in unilateral spinal anesthesia in patients with injuries and wounds of the lower limbs and uncompensated blood loss. METHODS: A total of 61 patients (all men) with injuries, wounds of the lower limbs, and signs of uncompensated blood loss were examined (shock index: 0.89 [0.81; 1.23] conventional units; hemoglobin: 9.37 [7.65; 12.3] g/dL). They underwent surgery under unilateral spinal anesthesia and were divided into two groups. Group 1 included 21 patients who received 10 mg of 0.5% hyperbaric bupivacaine during unilateral spinal anesthesia. Group 2 included 40 patients who received 12.5 mg of 0.5% hyperbaric bupivacaine during unilateral spinal anesthesia. For all patients, the dynamics of sensory (5-point scale) and motor blockade (modified Bromage scale), the frequency of vasopressor support, the need for additional analgesia, and adverse events were assessed. RESULTS: An adequate unilateral block was achieved in 100% of patients. In group 2, compared with group 1, sensory and motor blockade developed faster in the first 10 minutes (p 0.05); however, after the 15th minute, partial spread of the block to the contralateral side was observed (the difference Δ between the limbs decreased from 2.3 to 1.5 points, p 0.001). The frequency of vasopressor support was 16.4% (11.5%—phenylephrine, 4.9%—norepinephrine); additional analgesia was required in 4 (6.6%) patients in group 1. No adverse events related to anesthesia were recorded. The need for vasopressors correlated with the delay in blood loss replacement, not with the fact of performing unilateral spinal anesthesia. CONCLUSION: Both doses of 0.5% hyperbaric bupivacaine provide adequate anesthesia. The 12.5 mg dose allows for faster blockade but is associated with partial spread to the contralateral side. The 10 mg dose is preferable when maximum unilateral blockade is required. If the selection criteria are met and timely infusion therapy is provided, unilateral spinal anesthesia is safe in patients with uncompensated moderate blood loss. The need for vasopressors is associated with delayed blood loss replacement.