Preoperative fasting: New guidelines for elective procedures

By Carol Nathan | Fact-checked by Anastasia Climan, RDN, CD-N
Published March 30, 2023

Key Takeaways

  • The American Society of Anesthesiologists (ASA) has issued updated 2023 guidelines with recommendations for healthy patients undergoing elective procedures.

  • For these patients, preoperative fasting is important for reducing the risk of pulmonary aspiration of gastric contents.

  • New updates in the guidelines cover the use of clear liquids, whether protein should be added to clear liquids, the issue of chewing gum, and pediatric recommendations. 

The rationale for preoperative fasting is to minimize total gastric content, which will lower the risk of regurgitation and potential pulmonary aspiration during surgery. Pulmonary aspiration of gastric contents is rare but potentially life-threatening.

The American Society of Anesthesiologists (ASA) has issued updated guidelines for preoperative fasting, based on extensive literature reviews.[] These guidelines are for use in healthy patients undergoing elective procedures.

Definitions in the guidelines 

Healthy patients: Defined as those without comorbid conditions that might increase the risk of aspiration, including, but not limited to, esophageal disorders, diabetes, pregnancy, obesity, and opioid use.

Preoperative fasting: Defined by the 2017 version of these guidelines[] as a specified period of time before a surgical procedure when patients are not allowed to ingest liquids or solids orally.

Perioperative pulmonary aspiration: Defined as “aspiration of gastric contents occurring after induction of anesthesia, during a procedure, or in the immediate postoperative period.” 

Anesthesia care during procedures: Refers to general anesthesia, regional anesthesia, or procedural sedation and analgesia.

It is important for clinicians to study the updated guidelines, because some of the recommendations are new to this version.

Carbohydrate-containing clear liquids with or without protein

The updated guideline reaffirms previous statements that clear liquids are safe to drink until 2 hours prior to an elective operation. Clear liquids, according to the ASA, include water, black coffee, black tea, and juice without pulp. 

The ASA notes that “simple or complex carbohydrate-containing clear liquids appear to reduce hunger compared with noncaloric clear liquids. The addition of protein to preoperative carbohydrate-containing clear liquids did not seem to either benefit or harm healthy patients.”

Carbohydrate-containing clear liquids vs fasting

The guidelines state that, for patients with a low aspiration risk, taking carbohydrate-containing clear liquids until 2 hours preoperatively was reported by patients to be preferred to absolute fasting. In addition, patient satisfaction with both simple and complex carbohydrate-containing clear liquids was preferred over noncaloric clear liquids. 

Protein-containing clear liquids

From the studies the ASA reviewed in updating their guidelines, they found inconclusive evidence regarding an effect of protein-containing clear liquids on residual gastric volume. 

Therefore, no recommendation could be made for protein-containing liquids over other liquids.

Chewing gum before surgery

One of the more interesting aspects of this guideline update relates to whether chewing gum before anesthesia induction affects residual gastric volume, gastric pH, or pulmonary aspiration rates. Apparently, chewing gum during the fasting period before an elective operation is a common tactic by patients. 

However, the guideline authors found that any benefits of gum chewing were insufficient to encourage patients to chew before surgery, so they do not recommend it. However, if a patient chews gum anyway, for personal comfort, for example, it is not necessary to delay the scheduled elective procedure. The authors were careful to mention that it is imperative to make sure all patients take chewing gum out of their mouth before any sedative or anesthetic is administered.

One-hour clear liquid fasting in pediatric patients

The study authors purposefully reviewed the evidence for any benefits or harms of 1-hour vs 2-hour clear liquid fasting in pediatric patients undergoing elective procedures. They concluded that, to avoid prolonged fasting in children, clear liquids should be allowed in children at low risk of aspiration as close to 2 hours before procedures as possible. 

Although there are numerous drawbacks of prolonged fasting in children, there is still controversy as to the timing of clear liquids. 

What this means for you 

The American Society of Anesthesiologists emphasizes that every facility needs to make sure that all clinical team members are aware of these updates to the guidelines on preoperative fasting. They recommend that institutions update their policies, printed literature, and signage accordingly. Although the updates are based on a thorough review of the literature and clinical evidence, there are still research gaps and major uncertainties regarding the approaches recommended. It is important for clinicians to make sure that patients follow preoperative fasting recommendations.

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