ObjectiveTo determine the dose of hyperbaric bupivacaine 0.5% required for unilateral spinal anesthesia during diagnostic knee arthroscopy.Patients and methodsThis prospective, randomized, clinical study was performed in 80 patients who were assigned to four groups to receive different doses of intrathecal hyperbaric bupivacaine (5 mg, 7.5 mg, 10 mg and 12.5 mg in Groups 1, 2, 3, and 4 respectively). Onset of sensory and motor block, hemodynamic changes, regression of motor block, and incidence of complications were recorded.ResultsUnilateral sensory block was reported in 90% and 85% of patients in Group 1 and Group 2, respectively, but not in any patient in Group 3 and Group 4. Unilateral motor block (modified Bromage scale 0) was reported in 95% of patients in Group 1, 90% in Group 2, and only 5% in Group 3, while no patient in Group 4 showed unilateral motor block. The time required for regression of motor block (Bromage scale 0) was prolonged with higher doses. The incidence of nausea, vomiting, and urine retention was similar in the study groups.ConclusionUnilateral sensory and motor block can be achieved with doses of 5 mg and 7.5 mg hyperbaric bupivacaine 0.5% with a stable hemodynamic state. However, 7.5 mg of hyperbaric bupivacaine 0.5% was the dose required for adequate unilateral spinal anesthesia.

Background:Cisatracurium in clinical practice is devoid of histamine-induced cardiovascular effects. On the other hand, 2 ED95 doses of cisatracurium (100 µ g/kg) do not create satisfactory intubating conditions such as those seen with equipotent doses of atracurium. The recommended intubating dose of cisatracurium is 3 ED95. To understand this discrepancy better, we evaluated the potency and onset of atracurium and cisatracurium.Materials and Methods:The study designed as randomized controlled clinical trial to compare between atracurium (2×ED95) and different doses of cisatracurium (2×ED95, 4×ED95, 6×ED95) regarding onset time, duration of action, condition of intubation, hemodynamic effects, and sings of histamine release clinically. Sixty four patients were randomly assigned to one of four groups, the first group (group 1) received 2×ED95 dose of atracurium, group 2 received 2×ED95 dose of cisatracurium, group 3 received 4×ED95 dose of cisatracurium, while group 4 received 6×ED95 dose of cisatracurium. The Datex relaxograph (Type NMT-100-23-01, S/N: 37541) for neuromuscular monitoring was used.Results:HR, MABP was statistically significant increased post-intubation with administration of 2×ED95 dose of atracurium in group 1 and the same dose of cisatracurium in group 2 but 5-20 min later was not statistically significant with administration of 4×ED95 and 6×ED95 doses of cisatracurium in groups 3 and 4, respectively. Onset time was found to be significantly lower with 2×ED95 dose of atracurium than with the same dose of cisatracurium. At the same time, higher doses of cisatracurium (4×ED95 and 6×ED95) showed onset time and longer duration of action that was significantly lower than with atracurium and with lower dose of cisatracurium (2×ED95). Only 6×ED95 dose of cisatracurium showed statistically significant difference versus the atracurium dose with higher percentages of patients with excellent condition of intubation. 4×ED95 and 6×ED95 doses of cisatracurium were significantly better than 2×ED95 dose of cisatracurium. 2×ED95 dose of atracurium and 2×ED95 dose of cisatracurium were similar, while 4×ED95 and 6×ED95 doses of cisatracurium were significantly better than atracurium and 2×ED95 dose of cisatracurium.Conclusion:The same dose (2×ED95 dose) atracurium is more effective neuromuscular blocking agent than cisatracurium, while higher doses of cisatracurium 4×ED95 and 6×ED95 provide more effective, more rapid neuromuscular blocking with longer duration of action, stable hemodynamic status, and no associated signs of histamine release clinically.