Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration

Application to Healthy Patients Undergoing Elective Procedures: An Updated Report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration

Anesthesiology. 2017;126(3):376-393. 

In This Article

Methodology

Definition of Preoperative Fasting and Pulmonary Aspiration

For these guidelines, preoperative fasting is defined as a prescribed period of time before a procedure when patients are not allowed the oral intake of liquids or solids. Perioperative pulmonary aspiration is defined as aspiration of gastric contents occurring after induction of anesthesia, during a procedure, or in the immediate postoperative period. Throughout these guidelines, the term "preoperative" should be considered synonymous with "preprocedural," as the latter term is often used to describe procedures that are not considered to be operations. Anesthesia care during procedures refers to general anesthesia, regional anesthesia, or procedural sedation and analgesia.

Purposes of the Guidelines

The purposes of these guidelines are to provide direction for clinical practice related to preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration and to reduce the severity of complications related to perioperative pulmonary aspiration. Clinical practice includes, but is not limited to, withholding of liquids and solids for specified time periods before surgery and prescribing pharmacologic agents to reduce gastric volume and acidity. Enhancements in the quality and efficiency of anesthesia care include, but are not limited to, the utilization of perioperative preventive medication, increased patient satisfaction, avoidance of delays and cancellations, decreased risk of dehydration or hypoglycemia from prolonged fasting, and the minimization of perioperative morbidity. Complications of aspiration include, but are not limited to, aspiration pneumonia, respiratory compromise, and related morbidities.

Focus

Prevention of perioperative pulmonary aspiration is part of the process of preoperative evaluation and preparation of the patient. The guidelines specifically focus on preoperative fasting recommendations, as well as recommendations regarding the administration of pharmacologic agents to modify the volume and acidity of gastric contents during procedures in which upper airway protective reflexes may be impaired.

Airway management techniques that are intended to reduce the occurrence of pulmonary aspiration are not the focus of these guidelines. For example, a rapid-sequence induction/endotracheal intubation technique or awake endotracheal intubation technique may be useful to prevent this problem during the delivery of anesthesia care. The guidelines do not address the selection of anesthetic technique, nor do they address enhanced recovery protocols not designed to reduce the perioperative risk of pulmonary aspiration.

The intended patient population is limited to healthy patients of all ages undergoing elective procedures. The guidelines do not apply to patients who undergo procedures with no anesthesia or only local anesthesia when upper airway protective reflexes are not impaired and when no risk factors for pulmonary aspiration are apparent.

The guidelines may not apply to or may need to be modified for patients with coexisting diseases or conditions that can affect gastric emptying or fluid volume (e.g., pregnancy, obesity, diabetes, hiatal hernia, gastroesophageal reflux disease, ileus or bowel obstruction, emergency care, or enteral tube feeding) and patients in whom airway management might be difficult. Anesthesiologists and other anesthesia providers should recognize that these conditions can increase the likelihood of regurgitation and pulmonary aspiration, and that additional or alternative preventive strategies may be appropriate.

Application

These guidelines are intended for use by anesthesiologists and other anesthesia providers. They also may serve as a resource for other health care professionals who advise or care for patients who receive anesthesia care during procedures.

Task Force Members and Consultants

In 2015, the ASA Committee on Standards and Practice Parameters requested that the updated guidelines published in 2011 be re-evaluated. This current update consists of a literature evaluation and an update of the evidence-based guideline nomenclature. A summary of recommendations is found in appendix 1 (Table 1).

The previous update was developed by an ASA-appointed Task Force of ten members, including anesthesiologists in both private and academic practice from various geographic areas of the United States and consulting methodologists from the ASA Committee on Standards and Practice Parameters.

The original guidelines and the previous update in 2011 was developed by means of a seven-step process. First, the Task Force reached consensus on the criteria for evidence. Second, original published research studies from peer-reviewed journals relevant to preoperative fasting and pulmonary aspiration were reviewed and evaluated. Third, expert consultants were asked to: (1) participate in opinion surveys on the effectiveness of various preoperative fasting strategies and pharmacologic agents and (2) review and comment on a draft of the guidelines developed by the Task Force. Fourth, opinions about the guideline recommendations were solicited from a random sample of active members of the ASA. Fifth, the Task Force held an open forum at a major national meeting to solicit input on its draft recommendations. Sixth, the consultants were surveyed to assess their opinions on the feasibility of implementing the updated guidelines. Seventh, all available information was used to build consensus within the Task Force to finalize the updated guidelines.

Availability and Strength of Evidence

Preparation of these guidelines followed a rigorous methodological process. Evidence was obtained from two principal sources: scientific evidence and opinion-based evidence (appendix 2).

Scientific Evidence. Scientific evidence used in the development of these updated guidelines is based on cumulative findings from literature published in peer-reviewed journals. Literature citations are obtained from healthcare databases, direct internet searches, Task Force members, liaisons with other organizations, and from manual searches of references located in reviewed articles.

Findings from the aggregated literature are reported in the text of the guidelines by evidence category, level, and direction and in appendix 2 (Table 2). Evidence categories refer specifically to the strength and quality of the research design of the studies. Category A evidence represents results obtained from randomized controlled trials (RCTs) and Category B evidence represents observational results obtained from nonrandomized study designs or RCTs without pertinent comparison groups. When available, Category A evidence is given precedence over Category B evidence for any particular outcome. These evidence categories are further divided into evidence levels. Evidence levels refer specifically to the strength and quality of the summarized study findings (i.e., statistical findings, type of data, and the number of studies reporting/replicating the findings). In this document, only the highest level of evidence is included in the summary report for each intervention-outcome pair, including a directional designation of benefit, harm, or equivocality.

Category A: RCTs report comparative findings between clinical interventions for specified outcomes. Statistically significant (P< 0.01) outcomes are designated as either beneficial (B) or harmful (H) for the patient; statistically nonsignificant findings are designated as equivocal (E).

  • Level 1: The literature contains a sufficient number of RCTs to conduct meta-analysis,§ and meta-analytic findings from these aggregated studies are reported as evidence.

  • Level 2: The literature contains multiple RCTs, but the number of RCTs is not sufficient to conduct a viable meta-analysis for the purpose of these updated guidelines. Findings from these RCTs are reported separately as evidence.

  • Level 3: The literature contains a single RCT and findings are reported as evidence.

Category B: Observational studies or RCTs without pertinent comparison groups may permit inference of beneficial or harmful relationships among clinical interventions and clinical outcomes. Inferred findings are given a directional designation of beneficial (B), harmful (H), or equivocal (E). For studies that report statistical findings, the threshold for significance is P< 0.01.

  • Level 1: The literature contains observational comparisons (e.g., cohort, case-control research designs) with comparative statistics between clinical interventions for a specified clinical outcome.

  • Level 2: The literature contains noncomparative observational studies with associative statistics (e.g., relative risk, correlation, sensitivity and specificity).

  • Level 3: The literature contains noncomparative observational studies with descriptive statistics (e.g., frequencies, percentages).

  • Level 4: The literature contains case reports.

Insufficient Literature: The lack of sufficient scientific evidence in the literature may occur when the evidence is either unavailable (i.e., no pertinent studies found) or inadequate. Inadequate literature cannot be used to assess relationships among clinical interventions and outcomes because a clear interpretation of findings is not obtained due to methodological concerns (e.g., confounding of study design or implementation) or the study does not meet the criteria for content as defined in the "Focus" of the guidelines.

Opinion-based Evidence. All opinion-based evidence (e.g., survey data, open forum testimony, internet-based comments, letters, and editorials) relevant to each topic was considered in the development of these updated guidelines. However, only the findings obtained from formal surveys are reported in the current update.

Opinion surveys were developed by the Task Force to address each clinical intervention identified in the document. Identical surveys were distributed to expert consultants and a random sample of ASA members.

Category A: Expert Opinion: Survey responses from Task Force–appointed expert consultants are reported in summary form in the text, with a complete listing of consultant survey responses reported in appendix 2 (Table 3).

Category B: Membership Opinion: Survey responses from active ASA members are reported in summary form in the text, with a complete listing of ASA member survey responses reported in appendix 2 (Table 4).

Survey responses from expert and membership sources are recorded using a 5-point scale and summarized based on median values.**

  • Strongly Agree: Median score of 5 (at least 50% of the responses are 5)

  • Agree: Median score of 4 (at least 50% of the responses are 4 or 4 and 5)

  • Equivocal: Median score of 3 (at least 50% of the responses are 3, or no other response category or combination of similar categories contain at least 50% of the responses)

  • Disagree: Median score of 2 (at least 50% of responses are 2 or 1 and 2)

  • Strongly Disagree: Median score of 1 (at least 50% of responses are 1)

Category C: Informal Opinion: Open forum testimony obtained during development of these guidelines, Internet-based comments, letters, and editorials are all informally evaluated and discussed during the formulation of guideline recommendations. When warranted, the Task Force may add educational information or cautionary notes based on this information.

‡Society for Ambulatory Anesthesia 12th Annual Meeting, Orlando, Florida, 1997.
§All meta-analyses are conducted by the ASA methodology group. Meta-analyses from other sources are reviewed but not included as evidence in this document.
**When an equal number of categorically distinct responses are obtained, the median value is determined by calculating the arithmetic mean of the two middle values. Ties are calculated by a predetermined formula.

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