Sensory block duration after spinal anaesthesia supplemented with intravenous dexamethasone: a randomised controlled double-blinded trial.

BACKGROUND: Intravenous dexamethasone prolongs duration of analgesia or sensory block after injection of local anaesthetics close to peripheral nerves by an average of 8 h. Uncertainty remains on the potential increase in the duration of sensory block after spinal anaesthesia. The objective of this randomised controlled double-blinded trial was to investigate whether dexamethasone i.v. prolongs the sensory block of spinal anaesthesia with bupivacaine when compared with a control group.

METHODS: Of 50 patients undergoing lower limb osteoarticular surgery under spinal anaesthesia with isobaric bupivacaine 15 mg i.t. with morphine 100 μg i.t. were randomised to receive either dexamethasone 0.15 mg kg-1 i.v. or normal saline 3 ml i.v. The primary outcome was duration of sensory block defined as the time elapsed between injection of the local anaesthetic in the intrathecal space and the regression of sensory block by two dermatomes compared with the highest dermatome blocked. Secondary outcomes included intravenous morphine consumption, pain scores at rest and on movement, postoperative nausea and vomiting, and blood glucose at 2, 24, and 48 h.

RESULTS: Median duration of sensory block was 135 (105-225) min in the dexamethasone group and 158 (135-240 min) in the control group (P=0.19). Patients in the dexamethasone group received less morphine at 24 h, had significantly less postoperative nausea and vomiting at 2 h and 24 h, and had increased blood glucose at 24 h. Other secondary outcomes were similar between groups.

CONCLUSION: Intravenous dexamethasone did not prolong the sensory block of spinal anaesthesia with isobaric bupivacaine. However, it reduced morphine consumption and rate of postoperative nausea and vomiting at 24 h, at the expense of an increased blood glucose.

CLINICAL TRIAL REGISTRATION: NCT03527576 (Clinicaltrials.gov).