Why Fast Past Midnight?

Patient Experience

By: Daniel Cook

Published: 12/19/2019

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Patients who carbo-load before procedures can better handle the physical stress of surgery and recover sooner.


No food or drink past midnight is slowly giving way to carbo-loading up to 2 hours before surgery. Fasting past midnight has been an unwritten Ordinance of the OR for almost 75 years. We can trace its origins to an obstetrician and cardiologist named Curtis Mendelson, who in 1946 reported in an influential study that you could avoid aspiration during general anesthesia for delivery by restricting oral intake during labor.

“Pre-op fasting is a concept that’s been ingrained in surgeons and anesthesiologists since medical school,” says Gregg Nelson, MD, PhD, FRCSC, a professor at the Tom Baker Cancer Centre in Calgary, Alberta, Canada. “But in reality, the practice isn’t supported by evidence. In fact, evidence shows it may result in patient harm.”

A fasting state — when food has been completely digested and stored — occurs as soon as 4 hours after eating and can lead to post-op insulin resistance, hyperglycemia and dehydration. On the other hand, patients who carbohydrate load by drinking 50 g of maltodextrin reconstituted in a clear liquid or pre-surgery complex-carbohydrate drinks up to 2 hours before surgery are more physically prepared to endure the rigors of surgery.

Their blood glucose and blood pressure levels are stable, and they’re less likely to experience insulin resistance from the stress of surgery. They’ll also be in less pain and at lower risk of suffering post-op infections — factors that impact patient satisfaction and lead to better outcomes. You also can’t ignore the importance of improving the patient experience. Patients who consume a formulated drink before arriving for surgery feel fuller and hydrated, and therefore more comfortable and potentially less anxious.

It’s important to know which type of fluids patients should consume in the hours leading up to surgery. “Many surgical professionals believe sports drinks or apple and cranberry juices are effective options,” says Dr. Nelson. “But those drinks don’t contain enough of the complex carbohydrates needed to optimize patients for surgery. The take-home message is that drinks must have at least 50 g of complex carbohydrate in order to elicit the proper response.”

Letting patients drink clear fluids before surgery seems like a no-brainer, especially because most anesthesia guidelines now recommend that patients stop eating solid foods 6 hours before surgery, but be permitted to drink clear fluids up until 2 hours before procedures begin. (The American Society of Anesthesiologists issued those directives in updated guidelines published in 2017.) Still, involve your anesthesia team, who understandably might still heed Dr. Mendelson’s warning, when adding carbohydrate-rich drinks to your pre-op protocols.

“Aspiration is their biggest fear when they put patients under sedation or use a general anesthetic,” says Bryan Collier, DO, FACS, a professor of surgery and director of surgical nutrition at the Virginia Tech Carilion School of Medicine in Roanoke, Va. “However, the literature shows drinking glucose and water 2 hours before anesthesia empties from the stomachs of patients without gastric emptying issues.”

Healthy eating habits

PARTNERS IN CARE Efforts to improve outcomes after surgery have led to patients and providers becoming more aware of the importance of pre-op nutrition.

Efforts to improve patients’ nutritional status before surgery should also include screening for malnutrition, regardless of a patient’s outward appearance — an obese individual isn’t necessarily well nourished, points out Dr. Nelson. Detailed screening tools are available, but he says 2 basic questions can be used to quickly identify patients who might need further assessment:

  • Have you lost weight in the past 6 months without trying to lose this weight?
  • Have you been eating less than usual for more than a week? Patients who screen positive for malnourishment should receive counseling from a dietician or nutritionist before having surgery.

Putting patients on a healthy diet and prescribing a prehab exercise routine — one is ineffective without the other — for 4 to 6 weeks leading up to their procedures helps to build lean body mass and reduces the body’s inflammatory response to surgery.

Dr. Collier says optimized nutrition regimens should involve a high-protein diet, which includes eating between 1.0 g and 1.5 g of protein per kilo per day (an average-sized person weighing 70 kg should eat about 100 g of protein). He gives his patients more practical advice: Eat 3 scrambled eggs for breakfast, a protein shake during the day and a palm-sized piece of chicken, meat or fish at dinner. They’re also instructed to eat fewer carbs and more vegetables than fruit.

A growing movement

Patients are still asked to comply with a directive that's based on assumptions instead of solid evidence.

Much of the evidence that supports carbohydrate loading and avoiding pre-op fasting is based on major open colorectal surgery, says Dr. Nelson. He points out, however, that the nutritional status of patients undergoing outpatient procedures should be optimized as much as possible, especially as more involved surgeries move to the ambulatory setting.

“Patients in the same-day setting can still benefit from efforts to optimize their diet, even though outpatient procedures might not be as complex as major inpatient procedures,” explains Dr. Nelson.

Understanding the importance of optimizing patients’ pre-op nutritional status is increasing as more facilities implement Enhanced Recovery After Surgery (ERAS) protocols and manage entire episodes of care as part of bundled payment agreements. “Dietary interventions before elective surgery should be part of a formal prehabilitation program that focuses on nutrition, exercise and mental health,” says Dr. Nelson.

Dr. Collier hopes more surgeons focus on preparing patients for surgeries instead of trying to fill open spots in a schedule, especially if a patient hasn’t had adequate time to prehab for the procedure. Surgeon convenience, he says, should never trump getting patients into a better state of healing.

“Involving patients in preparing their bodies for surgery gives them ownership in their own care and will have them working harder to achieve excellent outcomes,” says Dr. Collier.

He touts teamwork to deliver on the big-picture importance of pre-op nutrition. “We all want patients to have excellent outcomes, and every member of the care team must work together to make that happen,” he adds. “Everyone has to be on the same page in terms of how to get patients back to baseline as quickly and as safely as possible.”

Dr. Collier is surprised it’s taken this long for more surgical professionals to buy into having patients enter surgery in a nutritionally optimized state. “But,” he adds, “we’re seeing a shift in their thinking as they begin to accept that pre-op nutrition recommendations are based on evidence-based perioperative care.” OSM

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