Friday, January 06, 2012

Update on Ingestion of Food and Fluids During Labor

Since C.L. Mendelson's report in 1946 (Mendelson C.L. The aspiration of stomach contents into the lungs during obstetric anesthesia. Am J Obstet Gynecol 1946; 52: 191-205.), most anesthesiologists assumed a very conservative stance used with obstetrical surgical patients with a "nil per os" (Latin for nothing by mouth or "NPO") for maximum safety. Is a slowing of the contraction pattern due to dehydration and no food/fuel? If so, does this also contribute to a slowed labor pattern and ultimately augmentation? More importantly, does having nothing in the stomach lower gastric acidity enough to protect the esophagus from corrosion should aspiration occur? Does being NPO eliminate Mendelson’s Syndrome?

Conversely, midwives and some physicians will allow fluids, soups, crackers, etc. during the early and active phases of labor. Can fluids or food during labor, along with IV fluids lower gastric acidity by giving the acid something to break down and facilitate the contraction pattern, possibly avoiding some interventions such as augmentation? And statistically, what is the likelihood of Mendelson's Syndrome or death from pneumonia due to aspiration?

According to Joy Hawkins, M.D. of the University of Colorado Health Sciences Center, scant key scientific data exists to show that laboring women who are kept NPO are less likely to die due to aspiration than women who had some sort of food or fluids. Without food, a laboring woman's body enters into ketosis. Starvation ketosis occurs when the pregnant body is starved, especially of carbohydrates. With starvation ketosis, tissues begin to breakdown and the byproducts of this ketabolism are called ketones, which actually aggravate nausea and possibly vomiting. So does keeping a woman NPO actually potentiate Mendelson's Syndrome? Additionally during pregnancy, women experience reflux due to delay emptying of stomach contents thought to be due to higher levels of progesterone, decreased motilin levels and the growing uterus applying pressure to the digestive system including the stomach valve. Do these hormonal influences along with NPO ketosis make things worse?

Dr. Robert Galser, M.D. of the University of Pennsylvania Medical Center says that we cannot afford to speculate as aspiration is a very real problem, especially for the mother who has general anesthesia with a cesarean section. Although Mendelson's research was mainly on rats and rabbits, it is suggested that IV's help to prevent ketosis while keeping stomach contents at a minimum. Currently, there is no evidence that moderate levels of ketosis are harmful to the fetus. Penny Simkin found that of several stressors in labor, being NPO was minimally stressful compared to not being active in labor.

In 2009, Maharaj (European Journal of Obstetrics, Gynecology and Reproductive Biology, September) stated that while the incidence of aspiration pneumonitis is rare, it is the fear of the birth-attendant to bear full responsibility if a patient inhales gastric contents when giving in to demands for liberal fluid and food regimes during labor that governs practice. While the bulk of evidence supports fluid intake in labor, there are insufficient published studies to draw conclusions about the relationship between fasting times and the risk of pulmonary aspiration during labor.

Singata, Tranmer and Gyte wrote in a 2010 Cochrane Database Systematic Review of restricting oral and fluid intake during labor (five studies and 3130 women), that the evidence “shows no benefits or harms” and that there “is no justification for the restriction of the fluids and food in labour for women at low risk for complications.

So is restricting food and fluids during labor a technocratic ritual or based on research? Since the basis for the restriction had the foundation of research in the 1940's when general anesthesia was the standard for cesarean sections, have we not progressed from there to the point where a significantly fewer number of women are exposed to general anesthesia for childbirth, with an even significantly fewer number of women aspirating acidic vomitus during anesthesia? Is this another case of "this is how we've always done it?"

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