BACKGROUND During caesarean delivery under spinal anaesthesia hypotension may be managed by norepinephrine in preference to phenylephrine due a perception of less bradycardia and fewer reductions in cardiac output. OBJECTIVE As the optimum prophylactic dose of norepinephrine is unclear, we aimed to investigate its dose–response for preventing postspinal hypotension in caesarean delivery. DESIGN A randomised, double-blinded, dose-finding study. SETTING Jiaxing University affiliated Women and Children Hospital, Jiaxing, China. PATIENTS Ninety-nine patients undergoing elective caesarean delivery from 1 February to 5 August: excluding patients with ASA III or above, preeclampsia or hypertension, pre-existing or gestational diabetes, BMI more than 35 kg m−2, height less than 150 cm or with more than 175 cm, or with contraindications to local anaesthesia. INTERVENTIONS Patients received 0, 0.04, 0.05, 0.06 or 0.07 μg kg−1 min−1 preventive norepinephrine infusions immediately after intrathecal injection of 10 mg bupivacaine with 5 μg sufentanil. MAIN OUTCOME MEASURES The norepinephrine (Median effective dose) or (95% effective dose) ED50 and ED95, which were estimated using Probit analysis to compare haemodynamic changes associated with the different doses. RESULTS The incidence of hypotension was 70, 47.4, 40, 20 and 15% in the 0, 0.04, 0.05, 0.06 and 0.07 μg kg−1 min−1 groups, respectively. The ED50, ED80 and ED95 values were 0.029 (95% CI 0.008 to 0.042 μg kg−1 min−1), 0.068 (95% CI 0.055 to 0.099 μg kg−1 min−1) and 0.105 μg kg−1 min−1 (95% CI 0.082 to 0.172 μg kg−1 min−1), respectively. Apgar scores or umbilical arterial pH were similar among groups. CONCLUSION The ED50, ED80 and ED95 were 0.029, 0.068 and 0.105 μg kg−1 min−1 respectively. A 0.07 μg kg−1 min−1 norepinephrine infusion may be optimum for preventing postspinal hypotension after intrathecal injection of 10 mg bupivacaine combined with 5 μg sufentanil. TRIAL REGISTRATION Chinese Clinical Trial Registry (identifier: ChiCTR-TRC-1800014614).

No abstract

BackgroundStudies have shown that dexmedetomidine (Dex) can prolong the duration of analgesia when added to local anaesthetic as an adjuvant in a central or peripheral nerve block. We hypothesized that intrathecal Dex can reduce the ED95 of spinal hyperbaric bupivacaine. Therefore, we conducted this prospective, double-blinded, randomized study to verify our hypothesis.MethodsNinety patients were allocated into the Dexmedetomidine group (received bupivacaine + 5 mcg dexmedetomidine) and the Control group (received bupivacaine + the same volume of saline) using a double-blinded and randomized method. The first patient in each group received 5 mg of IT hyperbaric bupivacaine, and the next dose for the following patient was determined by the probability of successful anaesthesia of the previous neighbouring dose. An improved up-down sequence allocated method combined with probit analysis was used to determine the ED95 of intrathecal hyperbaric bupivacaine for the two groups.ResultsThe ED95 and 95% confidence intervals (95% CI) of IT hyperbaric bupivacaine of the Dex group and Control group were 8.4 mg (95% CI, 6.5~ 13.8 mg) and 12.1 mg (95% CI, 8.3~ 312.8 mg), respectively. The duration of sensory block was longer in the Dex group than in the Control group (110.3 ± 35.3 vs 67.5 ± 26.2). The duration of analgesia was also longer in the Dex group than in the Control group (224.9 ± 45.4 vs 155.1 ± 31.6). The consumption of postoperative rescued sufentanil was significantly higher in the Control group than in the Dex group.ConclusionIntrathecal 5 mcg dexmedetomidine potentiated hyperbaric bupivacaine antinociception by 31% in spinal anaesthesia for patients undergoing caesarean section.Trial registrationWe registered this study in a Chinese Clinical Trial Registry (ChiCTR) centre on Nov 1st 2016 and received the registration number: ChiCTR-IPR-16009699.

BACKGROUND: Ondansetron has been shown to reduce the incidence of hypotension and vasopressor requirement during spinal anesthesia for obstetric and nonobstetric surgery. However, the magnitude of this effect has not been fully quantified. In this parallel-group, randomized, double-blinded study, we determined the effective dose in 50% of subjects (ED50) of a prophylactic phenylephrine infusion for preventing hypotension in patients who received a single dose of intravenous ondansetron 4 mg or saline control before combined spinal–epidural anesthesia for elective cesarean delivery. ED50 values obtained were compared to estimate the effect of ondansetron versus placebo on vasopressor requirement. METHODS: Sixty parturients were randomly assigned to receive ondansetron (group O) or saline control (group C) 10 minutes before positioning for induction of spinal anesthesia. A prophylactic phenylephrine infusion was used to prevent hypotension. The first patient in each group received a phenylephrine infusion at the rate of 0.5 µg/kg/min. The infusion rate for each subsequent patient was varied with increments or decrements of 0.05 µg/kg/min based on the response of the previous patient, and the effective dose of the phenylephrine infusion for preventing hypotension in 50% of patients (ED50) was calculated for each group and compared using up-down sequential analysis. Probit regression was applied as a backup and sensitivity analysis was used to compare ED50 values for phenylephrine between groups by comparing calculated relative mean potency. RESULTS: The ED50 (mean [95% confidence interval (CI)]) of the rate of phenylephrine infusion was lower in group O (0.24 µg/kg/min [0.10–0.38 µg/kg/min]) compared with group C (0.32 µg/kg/min [0.14–0.47 µg/kg/min]) (P < .001). The total consumption of phenylephrine (mean ± standard deviation [SD]) until delivery was lower in group O (316.5 ± 25.9 µg) than in group C (387.7 ± 14.7 µg, P = .02). The estimate of relative median potency for phenylephrine for group O versus group C was 0.74 (95% CI, 0.37–0.95). CONCLUSIONS: Under the conditions of this study, intravenous ondansetron 4 mg reduced the ED50 of a prophylactic phenylephrine infusion by approximately 26% in patients undergoing cesarean delivery under combined spinal–epidural anesthesia.

BackgroundAddition of intrathecal magnesium sulfate to local anesthetics has been reported to potentiate spinal anesthesia and prolong analgesia in parturients. The current study was to determine whether intrathecal magnesium sulfate would reduce the dose of hyperbaric bupivacaine in spinal anesthesia with bupivacaine and sufentanil for cesarean delivery.MethodsSixty healthy parturients undergoing scheduled cesarean delivery were randomly assigned to receive spinal anesthesia with 0.5% hyperbaric bupivacaine and 5 μg sufentanil with either 0.9% sodium chloride (Control group) or 50% magnesium sulfate (50 mg) (Magnesium group). Effective anesthesia was defined as a bilateral T5 sensory block level achieved within 10 min of intrathecal drug administration and no additional epidural anesthetic was required during surgery. Characteristic of spinal anesthesia and the incidence of side effects were observed. The ED50 for both groups was calculated using the Dixon and Massey formula.ResultsThere was no significant difference in the ED50 of bupivacaine between the Magnesium group and the Control group (4.9 mg vs 4.7 mg) (P = 0.53). The duration of spinal anesthesia (183 min vs 148 min, P < 0.001) was longer, the consumption of fentanyl during the first 24 h postoperatively (343 μg vs 550 μg, P < 0.001) was lower in the Magnesium group than that in the Control group.ConclusionsIntrathecal magnesium sulfate (50 mg) did not reduce the dose requirement of intrathecal bupivacaine, but can extend the duration of spinal anesthesia with no obvious additional side effects.Trial registrationThis study was registered with Chinese Clinical Trial Registry (ChiCTR) on 15 Jul. 2014 and was given a trial ID number ChiCTR-TRC-14004954.