One of the major concerns in spinal anesthesia with lidocaine is its short duration of action. Enhancement is necessary in some situations during surgery, because surgeons encounter with unexpected events and need more time. Therefore there is a need to increase anesthesia duration in these situations. Many studies investigated various additives with different administration routes to enhance spread and duration of spinal block with lidocaine. Because we only have morphine sulfate in our clinics and the sulfate compounds are neurotoxic, we cannot prescribe it by intrathecal route; for this reason we investigated effects of intravenous morphine on the spinal anesthesia with lidocaine. Methods: This double blinded randomized clinical trial study was performed on 36 patients who were allocated to two groups. All patients underwent spinal anesthesia with lidocaine by the same method. Patients in the case group received morphine plus midazolam intravenously as the additive medication and in the control group received normal saline plus midazolam. Duration, spinal block level, recovery time, sedation score and adverse effects were compared between the two groups. Results: This study showed that although intravenous morphine can provide better safe sedation (p-value < 0.01), it has no effect on the level (p-value: 0.42) and duration of spinal block (p-value: 0.26). Although heart rate and blood pressure had significant decrease in the case group (p-value < 0.01 and
Key words: Spinal anesthesia, lidocaine, morphine, intravenous morohine
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