“Nil per os (alternatively nihil/non/nulla per os) (NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase which translates as "nothing through the mouth". In the United Kingdom, it is translated as nil by mouth (NBM).

Typical reasons for NPO instructions are the prevention of aspiration pneumonia, e.g. in those who will undergo general anesthetic, or those with weak swallowing musculature, or in case of gastrointestinal bleeding, gastrointestinal blockage, or acute pancreatitis. Alcohol overdoses that result in vomiting or severe external bleeding also warrants NPO instructions for a period.

When patients are placed on NPO orders prior to surgical general anesthesia, physicians would usually add the exception that patients are allowed a very small drink of water to take with their usual medication. This is the only exception to a patient's pre-surgery NPO status. Otherwise, if a patient accidentally ingested some food or water, the surgery would usually be canceled or postponed for at least 8 hours.”

“In 1946 Dr. Curtis Mendelson hypothesized that the cause of pneumonia following general anesthesia was aspiration of the stomach contents, due to delayed gastric emptying in labor. He noted that food could be vomited 24-48 hours after being eaten. Dr. Mendelson experimented on rabbits to examine the effects of content in their lungs. Aspiration (taking the particles into your lungs) of undigested food could cause obstruction, but not aspiration pneumonia, and no deaths were due to aspiration of fluids with a neutral pH. The rabbits only died when they aspirated materials containing hydrochloric acid. He said by forbidding food and drink in labor you could reduce stomach volume, thereby decreasing the risk of maternal problems from acid aspiration while under general anesthesia. We also found that there were two factors that increased the risk of maternal problems:

• A volume of an aspirate of 25+ mm
• A pH of 2.5 higher (biggest problem)

However, in the 40's and 50's general anesthesia was used much more often for labor and delivery. For example, most forceps were done under general anesthesia. Gases were given with a face mask, often opaque, which hampered the anesthesiologist's view of the airway. Dr. Robert Parker, in 1950, largely blamed aspiration on poor anesthetic technique and poor quality of the practitioners.

“The risks of aspiration are only a problem when general anesthesia is used (3.5-13% of cesareans), and the technique has improved. Anesthesiologists now have more quality control.

So the two solutions that have been the most popular have been the IV and antacids before a cesarean surgery.

IV fluids are not always reasonable solution to hydration problems, as they have problems of their own: over load, closer monitoring of intake and output, hyperinsulinism in infants after 25 g of glucose, and the salt free solutions can result in serious hyponatraemia in mom and baby. And the antacids are usually given in the quantity of 30 mm, a volume known to increase the risks of aspiration pneumonia.

We also know that restricting food in labor can cause problems of its own. Besides the stress factors, restricting intake during labor can cause dehydration and ketosis.”

• Stress factors caused by denial of food and water
• Dehydration
• Ketosis
• Longer labor: women who are allowed to eat and drink to comfort in labor have shorter labor (by an average of 90 minutes)
• May need augmentation with Pitocin
• May require more pain medications
• In one study, babies had lower apgar scores than of those in the control group. [2]

II. Aspiration Prevention

Clear Liquids.

There is insufficient published evidence to draw conclusions about the relationship between fasting times for clear liquids and the risk of emesis/reflux or pulmonary aspiration during labor. The consultants and ASA members both agree that oral intake of clear liquids during labor improves maternal comfort and satisfaction. Although the ASA members are equivocal, the consultants agree that oral intake of clear liquids during labor does not increase maternal complications.

Recommendations.

The oral intake of modest amounts of clear liquids may be allowed for uncomplicated laboring patients. The uncomplicated patient undergoing elective cesarean delivery may have modest amounts of clear liquids up to 2 h before induction of anesthesia. Examples of clear liquids include, but are not limited to, water, fruit juices without pulp, carbonated beverages, clear tea, black coffee, and sports drinks.∥ The volume of liquid ingested is less important than the presence of particulate matter in the liquid ingested. However, patients with additional risk factors for aspiration (e.g., morbid obesity, diabetes, difficult airway) or patients at increased risk for operative delivery (e.g., nonreassuring fetal heart rate pattern) may have further restrictions of oral intake, determined on a case-by-case basis.