Anesthesia in the News
  • Effect of Epidural Analgesia in Labor on Gastric Emptying

    The initial description of aspiration pneumonia in 66 parturients by Curtis Lester Mendelson in 1946 led to advocacy for measures to prevent this complication of general anesthesia, which included strict fasting during labor.  Since then, the rise of regional anesthesia techniques and advances in obstetric anesthesia have both contributed to a significant reduction in the incidence of peripartum aspiration pneumonia.  Today, the mortality rate associated with aspiration is less than 1 in 1 million pregnancies in the United States (Creanga et al. 2017).  Consequently, some medical authorities questioned strict fasting during labor, and more liberal practices have advocated for and implemented clear fluids in some countries for more than 20 years (Beggs et al. 2002; Berry et al. 1997).

    Guidelines vary

    Current US and European guidelines permit clear fluids during labor, although US guidelines are more conservative than European guidelines, allowing only moderate amounts of clear fluids for uncomplicated laboring women (Practice Guidelines for Obstetric Anesthesia: An Updated Report by the American Society of Anesthesiologists Task Force on Obstetric Anesthesia and the Society for Obstetric Anesthesia and Perinatology. 2016; Smith et al. 2011).  US and European guidelines differ regarding solid food during labor.  While the European guidelines permit the oral intake of low-residue food during labor, guidelines of the American Society of Anesthesiologists and the Society for Obstetric Anesthesia and Perinatology prohibit any solid food during labor.  The primary reason for this discrepancy is the lack of reliable data regarding gastric emptying of solid food during labor.

    Authors of a small prospective comparative study recently published in the journal Anesthesiology sought to test their hypothesis that the gastric emptying fraction of a light meal would be reduced in parturients receiving epidural analgesia and parturients with no labor analgesia compared with nonpregnant and pregnant women.

    Gastric emptying measured by ultrasound

    The authors sought to determine and compare the gastric emptying after intake of a standardized light meal in women in labor with epidural analgesia (Parturient Epidural Group), women in labor without epidural analgesia (Parturient-No Epidural Group), pregnant women not in labor (Pregnant Control Group) and nonpregnant women (Nonpregnant Control Group) using a reliable, noninvasive ultrasound tool.  They hypothesized that the gastric emptying fraction of a light meal measured during a 15- to 90-minute period would be reduced by at least 30% in parturients with labor epidural compared with the Nonpregnant Control Group and the Pregnant Control Group.

    To check their premise, 10 subjects were enrolled and tested in each of the 4 Groups.  All volunteers and parturients were 40 years of age or younger, had no significant medical history (American Society of Anesthesiologists Physical Status I), had fasted for at least 6 hours for solids and 1 hour for clear liquids, and had an empty stomach on first ultrasound examination.

    For women in the Parturient–Epidural Group, epidural analgesia was provided by an initial bolus of 12 ml followed by a continuous epidural infusion of 3 ml/h and patient-controlled boluses (5 ml with a 15-min lock-out interval) of a mixture 1 mg/ml of ropivacaine and 0.25 µg/ml sufentanil, and the test meal was ingested within the first hour after the induction of epidural analgesia.

    Following the initial ultrasound, each subject ingested a light meal (125 g yogurt; 120 kcal) within 5 minutes.  Next, ultrasound measurements of the antral area were performed at 15, 60, 90, and 120 minutes.  The primary outcome measures were the antral cross-sectional areas measured 15 and 90 minutes after ingestion of the meal.  The fraction of gastric emptying at 90 minutes was calculated as [(antral area90 min/antral area15 min) – 1]×100, and half-time to gastric emptying was also determined.

    Achieving statistical significance

    Of the 43 women included in the study, 2 women in the Parturient–Epidural Group did not complete the session (inconclusive first ultrasound examination [n = 1]; gave birth within 120 min of the test meal [n = 1]) and 1 woman in the Pregnant Group did not complete the session because her stomach was full at the first ultrasound.  These patients were replaced by other participants, and thus 40 women (10 per Group) were included and analyzed.  Women included in the Parturient–No Epidural Group were either women who did not wish to receive any labor epidural (n = 2) or women who did receive epidural analgesia later in labor following completion of the study (n = 8).

    The median (interquartile range) fraction of gastric emptying at 90 minutes was 52% (46 to 61), 45% (31 to 56), 7% (5 to 10), and 31% (17 to 39) for nonpregnant women, pregnant women, parturients without labor analgesia, and parturients with labor epidural analgesia, respectively (P<0.0001).  The fraction of gastric emptying at 90 minutes was statistically significant and lower in the Parturient-Epidural Group than in the Nonpregnant and Pregnant Control Groups.  In addition, the fraction of gastric emptying at 90 minutes was statistically significant and lower in the Parturient-No Epidural Group than in the Parturient-Epidural Group.

    Caution remains about gastric emptying

    The main findings in this prospective study were the statistically and clinically significant lower gastric emptying fractions and longer half-times to gastric emptying of a light meal in parturients receiving epidural analgesia compared with those fractions in nonpregnant and pregnant participants.  According to the study authors, another important finding was the statistically significant lower gastric emptying fraction in parturients not receiving epidural analgesia compared to parturients receiving epidural analgesia, as well as the nonpregnant and pregnant controls.

    “Taken together, the results of the current study suggest that patient-controlled epidural analgesia with a low concentration of ropivacaine and sufentanil significantly improves gastric motility and emptying compared to that seen in natural labor without analgesia,” they concluded.

    Because the gastric emptying of a light meal was delayed in a clinically significant way for parturients receiving epidural analgesia and was further delayed in parturients not receiving epidural analgesia in comparison with pregnant and nonpregnant women, the researchers believe that their study’s results should lead anesthesia providers to remain cautious about permitting solid foods during labor, particularly when no epidural analgesia is used.

    They further noted that their research underscores the value of gastric ultrasound both for monitoring gastric contentsand for guiding the decision to fast or feed during labor.

    The complete study can be located at no cost here:  “Pregnancy and Labor Epidural Effects on Gastric Emptying: A Prospective Comparative Study.”

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