What's new in Obstetric Anesthesia? The 2013 Gerard W. Ostheimer lecture

Intrathecal magnesium sulfate does not reduce the ED50 of intrathecal hyperbaric bupivacaine for cesarean delivery in healthy parturients: a prospective, double blinded, randomized dose-response trial using the sequential allocation method

Background

Addition 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.

Methods

Sixty 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.

Results

There 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.

Conclusions

Intrathecal 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 registration

This study was registered with Chinese Clinical Trial Registry (ChiCTR) on 15 Jul. 2014 and was given a trial ID number ChiCTR-TRC-14004954.

[Obstetrical aspects of perioperative medicine]

Recently the most frequently applied surgical procedure worldwide has been Cesarean section. It is essential to perform the operation without any complication. In addition, a fast postoperative recovery must be provided, because all mothers must have the chance for being together with their newborn infant even on the first day. The maternal mortality rates of Cesarean section significantly decreased in the last decades due to the planned team work as well as the widely applied regional (spinal and epidural) anesthetic procedures. Apart from the obstetrician and neonatologist the anesthesiologist is the member of the perinatal team, too, who is responsible for the patient's perioperative care. To prevent complications and have an early successful treatment the anesthesiologist should be informed by the pregnant woman' s health status in time in order to be able to plan the perioperative management. The high-risk groups of pregnant women, the most common causes of maternal death and possibilities of prevention and treatment are discussed.