Anesthetic exposure during pregnancy is viewed as a relatively routine medical practice. However, recent rodent studies have suggested that common anesthetic agents can damage the developing brain. Here we assessed this claim in a higher order species by exposing previously instrumented near-term pregnant sheep at gestational day 122 (+/-1) to a combination of midazolam, sodium thiopental, and isoflurane at clinically relevant doses and means of anesthetic delivery (i.e., active ventilation). Four hours of maternal general anesthesia produced an initial increase in fetal systemic oxygenation and a sustained increase in fetal cerebral oxygenation, as determined by in utero near-infrared spectroscopy. Postexposure monitoring failed to identify changes in physiologic status that could be injurious to the fetal brain. Finally, through the histologic assessment of noninstrumented sheep at the same gestational time point, we found no evidence for a direct fetal neuro-toxic effect of our triple-drug regimen. Collectively, these results appear to corroborate the presumed safety of inhalational anesthetic use during pregnancy.

Previous studies with near-term sheep determined that carbon dioxide pneumoperitoneum produces respiratory acidosis but does not decrease fetal oxygenation. In contrast, the current findings indicate that in the preterm fetus, insufflation-induced hypercapnia and acidosis are accompanied by prolonged fetal hypoxia and cardiovascular depression. This result suggests that additional work should be conducted to confirm the presumed safety of conducting minimally invasive procedures during the second trimester.

Any adverse preterm fetal response to maternal surgery should not be attributed solely to the actions of general anesthesia upon the fetus.

Topics: Pharmacology P regnant women may require sedation, anesthesia, or pain control for nonobstetric-related care. The a 2adrenergic receptor (a 2 AR) agonist dexmedetomidine (DEX) has sedative, anxiolytic, and analgesic actions and can reduce the dose requirements for other sedative and analgesic drugs through synergistic effects with opioids and benzodiazepines. Clinical investigations of DEX have not included significant numbers of pregnant patients; in fact, most studies have excluded pregnant women. This study was designed to determine the maternal and fetal responses to an intravenous infusion of DEX in sheep.The study was performed on 9 preterm pregnant ewes at gestational day 92, a time relatively equivalent to the end of the second trimester in humans. Surgical anesthesia was induced with IV sodium thiopental and maintained with isoflurane in oxygen. Standard surgical techniques were used to insert catheters into maternal femoral artery and jugular vein as well as bilateral fetal femoral arteries. A flow probe was placed around the left uterine artery to record uterine blood flow (UBF). The fetal head was exteriorized to install near-infrared spectroscopy probes to assess changes in fetal cerebral oxygenation during and after drug administration to the mother. The fetus was then returned to the uterus. After the procedure, infiltration of the surgical incision with bupivacaine and intramuscular nalbuphine hydrochloride were used to control postoperative pain. Animals recovered for 48 hours before the DEX-exposure experiment was conducted. Maternal and fetal cardiovascular data along with UBF were recorded. Fetal cerebral oxygenation, measured by changes in oxygenated, deoxygenated, and total hemoglobin (Hb) (oxyHb, deoxyHb, and totalHb, respectively), was quantitated with the near-infrared spectroscopy monitor. After a baseline recording period of 30 to 60 minutes, drug exposure was begun using human-dosing guidelines. Each ewe received an IV bolus injection of DEX, 1.0 mg/kg followed by a constant IV infusion of 1.0 mg/kg/h. The infusion was stopped after 3 hours and the experiment halted 2 hours later. Hemodynamic and fetal cerebral oxygenation data were continuously recorded during the study; maternal and fetal arterial blood samples were obtained at 30-minute intervals.The statistical analyses focused on the 3 primary endpoints: changes in fetal cerebral oxygenation, maternal and fetal cardiovascular status, and arterial blood gas status.All animals tolerated the DEX infusion with no complications during or after drug exposure. Profound sedation occurred within minutes of starting the infusion; consciousness returned within 30 to 60 minutes after discontinuation of the infusion. During the infusion, the sheep were unresponsive to painful stimuli. The ewes had a normal respiratory pattern throughout the exposure period, as evidenced by the arterial blood gas values that remained normal throughout the study. Only blood glucose levels in both the ewe and fetus continued to rise during DEX infusion, p...