Anesthesia for Obstetrics and Gynecology - Anesthesia for Nonobstetric Surgery During Pregnancy
Anesthesia for Nonobstetric Surgery During Pregnancy
Approximately 1% to 2% of women undergo nonobstetric surgery during pregnancy. Purely elective surgical procedures are relatively contraindicated in pregnancy and should be postponed until 6 weeks postpartum. If a surgical procedure must be performed, the second trimester is the preferred time. The objectives in the anesthetic management include the following:
- Maternal safety. Induction and emergence from general anesthesia are more rapid in pregnant patients due to the increase in minute ventilation and decrease in FRC. Uterine displacement to minimize aortocaval compression should be considered as early as the second trimester. Local anesthetic potency is also increased in these patients. The dose should be reduced because lower plasma concentrations are associated with toxicity. During any anesthetic, oxygen transport to the placenta must be maintained.
- Teratogenicity. Some practitioners avoid the use of N2O in the first and second trimesters because of its interference with DNA synthesis. Recent studies show an increase in neuronal apoptosis in animals exposed to volatile anesthetics. This effect has not been confirmed in humans. The teratogenic effect of all other anesthetics has not been demonstrated in humans. Organogenesis in the first trimester contraindicates all but emergency surgery. When feasible, surgery should be delayed until at least 2 to 6 weeks postpartum.
- Reversal of residual neuromuscular block. The use of the combination of neostigmine and glycopyrrolate might expose the fetus to unopposed neostigmine and cause fetal bradycardia, as placental permeability to glycopyrrolate is lower than to neostigmine.
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