Modernizing perioperative fasting: Liberal clear liquids, glucagon-like peptide-1 receptor agonists, and point-of-care gastric ultrasound

ABSTRACT

Preoperative fasting was historically introduced to reduce pulmonary aspiration during anesthesia; however, contemporary evidence increasingly challenges the assumption that “longer is safer.” Aspiration is a rare event and is primarily determined by patient- and procedure-related risk factors rather than fasting duration alone, whereas prolonged fasting is consistently associated with patient discomfort and adverse physiological consequences. Risk assessment has become more complex with emerging clinical factors, most notably the widespread use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs), which may delay gastric emptying and lead to residual solid gastric contents despite adherence to guideline-recommended fasting intervals. International recommendations for perioperative GLP-1 RA management remain heterogeneous, underscoring the need for pragmatic, risk-stratified strategies that balance aspiration risk mitigation with metabolic stability. Point-of-care gastric ultrasound is increasingly recognized as a valuable bedside decision-support tool, enabling qualitative and quantitative assessment of gastric contents in uncertain or high-risk scenarios and informing airway management and procedural timing. This review synthesizes the current evidence supporting liberal preoperative intake of clear liquids and highlights the transition from rigid, time-based rules toward individualized, physiology-informed approaches to perioperative hydration and nutrition.

Introduction

Preoperative fasting is one of the oldest and most deeply ingrained practices in anesthesiology and was historically introduced to reduce the risk of pulmonary aspiration during the induction of anesthesia. Mendelson’s observations in 1946 linking gastric aspiration to severe maternal morbidity and mortality during obstetric anesthesia established preoperative fasting as a cornerstone of perioperative safety.[1] For decades thereafter, the guiding principle has been simple: longer fasting is assumed to provide greater protection. However, contemporary evidence increasingly challenges this assumption for clear liquids, demonstrating that prolonged fasting from clear fluids does not meaningfully reduce the risk of aspiration, while simultaneously imposing significant physiological and patient-centered burdens. In contrast, appropriate fasting from solid foods remains essential for gastric emptying and aspiration risk reduction.[2]

Modern anesthetic practices have evolved substantially since the era when fasting guidelines were first conceived. Advances in airway management, anesthetic pharmacology, perioperative monitoring, and postoperative care have dramatically altered the risk of developing complications. Large audits, including the Fourth National Audit Project (NAP4) in the United Kingdom, have demonstrated that although aspiration remains a rare event, it continues to carry a disproportionately high morbidity and mortality.[3] Importantly, these data also suggest that aspiration risk is not reliably predicted by fasting duration alone, but rather by a complex interplay of patient factors, gastrointestinal (GI) physiology, pharmacological influences, and airway management strategies.[4]

Among these emerging factors, novel pharmacotherapies have introduced additional complexity into preoperative fasting assessment. The widespread use of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) for diabetes, obesity, and cardiometabolic diseases has introduced a novel and clinically relevant mechanism of delayed gastric emptying, predominantly affecting the processing of solid contents through impaired antral motility and pyloric regulation, often in the absence of apparent GI symptoms.[5]

This review synthesizes the current evidence on preoperative fasting practices, with particular emphasis on the liberalization of clear liquid intake, examines emerging challenges related to novel pharmacotherapies, and explores the evolving role of gastric ultrasonography (US) in perioperative care. By integrating guideline recommendations with contemporary clinical data, we propose a framework for transitioning from dogmatic fasting rules to a more individualized, evidence-based, and patient-centered approach to perioperative nutrition and aspiration-risk management.

Physiological and clinical basis for liberal clear fluid fasting

Gastric emptying of clear liquids

Clear liquids are characterized by rapid, predictable, and physiologically efficient gastric emptying. In contrast to solid food, which requires antral trituration and reduction of particle size to less than approximately 2 mm before passage through the pylorus, clear liquids contain no large particles; therefore, they traverse the stomach without the need for mechanical processing. Consequently, gastric emptying of clear fluids follows an exponential pattern.[6] Radionuclide scintigraphy studies have demonstrated that approximately 90% of an ingested clear liquid empties from the stomach within the first hour, with near-complete emptying occurring within 2 h. In comparison, complete gastric emptying of a standard solid meal typically requires 3–5 h, whereas indigestible solids may remain in the stomach for 6–12 h.[7] The human stomach is a highly distensible organ capable of accommodating substantial volumes before a clinically relevant rise in intragastric pressure occurs, typically at volumes around 800 mL. As gastric distension increases, a compensatory rise in lower esophageal sphincter (LES) tone occurs, helping to preserve the gastroesophageal pressure barrier. Following an overnight fast of more than 8 h, the residual gastric volume in healthy adults averages 20–30 mL, with some interindividual variability. These small residual volumes are far below the threshold required to challenge LES competence or promote gastroesophageal reflux in individuals with normal sphincter function. These physiological observations indicate that, under normal circumstances, gastric volume alone is unlikely to constitute a clinically meaningful risk of aspiration.[8] Evidence now indicates that the presence of small volumes of clear fluid within the stomach (typically ≤1.5 mL·kg^–¹, corresponding to approximately 50–100 mL in most adults) is physiologically well tolerated and does not meaningfully increase the risk of aspiration when appropriate airway management strategies are employed. Accordingly, the concept of an “empty stomach” has evolved from a rigid, time-dependent definition to a functional, volume- and physiology-based paradigm, providing a sound mechanistic foundation for liberalized clear liquid fasting policies in modern anesthetic practice.

Established guideline recommendation: the 2-h clear liquid rule

The American Society of Anesthesiologists (ASA) first updated its official fasting guidelines in 1999.[9] Subsequent updates published in 2017 and 2023 explicitly stated that clear liquids may be consumed up to 2 h before anesthetic induction for elective procedures. This recommendation was based on physiological evidence summarized in the ASA 2017 guidelines, where meta-analyses of randomized controlled trials demonstrated no meaningful differences in gastric volume or gastric pH between patients fasting for 2–4 h and those fasting for more than 4 h after clear liquid intake.[10,11] Similarly, the European Society of Anaesthesiology and Intensive Care (ESAIC) and other international organizations actively recommend the intake of clear liquids up to 2 h before surgery for adults. Importantly, ESAIC further extends this physiological rationale to pediatric practice, recommending that children may safely consume clear fluids up to 1 h before anesthesia, supported by large prospective data demonstrating no increase in aspiration risk.[12]

Implementation gap and ultraliberal fasting practices in real-world settings

Beyond the established 2-h clear liquid recommendation endorsed by international guidelines, several centers have explored even more liberal, practice-based approaches aimed at improving patient comfort and real-world adherence to fasting policies. In a multicenter study published by Marsman et al.[13] in 2023, a liberal fasting policy allowing the intake of clear liquids until shortly before surgery (“sip till send”) was implemented and compared with standard fasting practices in more than 16,000 patients, while approximately 60,000 patients served as controls under conventional fasting rules. Despite a median fasting time for clear liquids of approximately 74 min in the liberal group, no significant difference was observed between the groups in terms of regurgitation or aspiration incidence. The few aspiration events observed in the liberal group were attributable to confounding factors, such as solid food aspiration or unrecognized bowel obstruction. Furthermore, the similarity in fasting duration between patients who experienced intraoperative regurgitation and those who did not support the absence of a direct association between a 1 and 2-h clear liquid fasting interval and increased risk was observed.

Patient-centered outcomes

One of the primary objectives of liberalizing preoperative clear liquid fasting duration is to improve patient comfort and the overall perioperative experience. Although prolonged fasting has traditionally been regarded as safe in terms of aspiration risk, it constitutes a substantial physical and psychological burden on patients. Individuals kept on nil per oral (NPO) for extended periods frequently experience thirst, dry mouth, hunger, restlessness, and anxiety; in habitual caffeine consumers, withdrawal symptoms, such as headache, may also occur. Clinical studies have demonstrated that excessive fasting is associated with increased preoperative anxiety and fatigue and may contribute to a higher incidence of postoperative nausea and vomiting (PONV).[14,15] Despite clear recommendations allowing clear liquids up to 2 h before anesthesia, real-world adherence remains poor. In the Thirst study (46 centers, 12 European countries; n = 5100 elective adult patients), the median preoperative clear liquid fasting time was 12 h and 95% of patients fasted for more than 4 h, with fewer than 1% drinking within 2 h of anesthesia. These contemporary data highlight a persistent implementation gap and reinforce the need for institutional quality-improvement strategies to ensure adherence to the recommended practice of allowing clear liquid intake up to 2 h before anesthesia, where appropriate.[16]

Permitting the intake of clear liquids closer to the time of surgery significantly alleviates thirst and hunger and enhances the patient experience without compromising safety. This approach has been explicitly emphasized in the 2023 updated guidelines of the ASA, which identify fasting-related adverse effects, such as hunger, thirst, and nausea, as patient-centered outcomes that should be actively avoided. The guidelines indicate that the vast majority of patients prefer the intake of clear, preferably carbohydrate-containing liquids, up to 2 h before surgery, rather than prolonged fasting.[11]

Postoperative oral intake: completing the continuum

Contemporary enhanced recovery concepts emphasize that preoperative fasting should not be unnecessarily prolonged during the postoperative period. Accordingly, the historically common practice of routine NPO orders after surgery has been largely abandoned for most surgical procedures. Current international guidelines (ASA, ESAIC, ERAS, and ESPEN) recommend resuming oral intake as early as feasible in patients who have safely emerged from anesthesia and have adequate airway protective reflexes.[11,12,17,18] In most cases, initiating oral intake of clear liquids during the immediate recovery phase is considered safe.

Early postoperative oral intake is a cornerstone of ERAS protocols. Evidence from randomized controlled trials and meta-analyses has demonstrated that early feeding is associated with faster GI recovery, lower postoperative complication rates, and shorter hospital length of stay without an increased risk of anastomotic leakage or other surgical complications.

Special Patient Populations

Diabetes mellitus

Patients with diabetes mellitus, particularly those with long-standing disease or suboptimal glycemic control, face a heightened risk of delayed gastric emptying, primarily driven by diabetic autonomic neuropathy. A significant clinical challenge is that gastroparesis can remain “silent,” existing without overt GI symptoms. Consequently, a patient’s fasting history may offer a false sense of security regarding aspiration risk. Furthermore, clinicians must balance this risk against the metabolic dangers of overfasting. Prolonged caloric restriction can precipitate hypoglycemia, ketosis, and perioperative dehydration. While standard clear liquid intervals are generally safe for well-controlled, asymptomatic patients, those with suspected gastroparesis require a meticulous assessment rather than a standard protocol.[12]

Obesity and bariatric surgery

Historically, obesity was treated as a definitive risk factor for pulmonary aspiration, leading to overly conservative fasting mandates. However, modern evidence shifts this perspective: obesity in isolation does not appear to delay the gastric emptying of clear liquids. Hence, obesity alone is not an indication for prolonged fasting times. However, increased aspiration risk is related to the presence of gastroesophageal reflux disease (GERD)/obstructive sleep apnea (OSA)/delayed gastric emptying from diabetes, etc., Gastric US and scintigraphy studies confirm that the emptying profiles of obese patients largely mirror those of nonobese individuals. As a result, major clinical guidelines now support standard clear liquid intervals for asymptomatic obese patients. In contrast, patients undergoing bariatric surgery or those with obesity-related comorbidities, such as GERD, OSA, or diabetes, may warrant a more cautious, individualized approach.[18] Particular attention needs to be paid in cases of postbariatric surgery—gastric bypass/balloon placement patients, etc., where they are at significant risk for aspiration with delayed gastric emptying or anatomical changes to the emptying track pose the risks.

Pregnancy

Pregnancy introduces unique physiological stressors, such as reduced LES tone and increased intra-abdominal pressure, both of which theoretically elevate aspiration risk. However, contemporary practice distinguishes between the active labor setting and elective procedures.

Pregnancy is associated with physiological changes that may influence aspiration risk, including reduced LES tone mediated by progesterone, increased intra-abdominal pressure from the gravid uterus, and delayed gastric emptying during labor due to pain, opioid use, and stress responses. These factors historically led to overly conservative fasting practices in all pregnant patients. Contemporary guidance, however, distinguishes clearly between active labor and elective, nonlaboring settings.

In women who are not in active labor—such as those scheduled for elective cesarean delivery or other procedures—gastric emptying of clear liquids remains comparable to that of nonpregnant adults. International guidelines therefore support the intake of clear fluids up to 2 h before anesthesia in this population.[11,19] Allowing clear liquids mitigates maternal dehydration, reduces the incidence of hypotension during neuraxial anesthesia, and improves overall comfort without increasing aspiration risk.

In contrast, active labor represents a dynamic physiological state in which gastric emptying becomes unpredictable. Pain, anxiety, endogenous catecholamine release, and frequent opioid administration contribute to delayed gastric emptying, and the urgency of potential operative intervention limits the reliability of fasting history.[10] In this context, a more conservative approach is warranted, and women in established labor are often managed as having a potentially “full stomach,” with appropriate airway precautions tailored to the clinical scenario.

Pediatric patients

Prolonged preoperative fasting in children can be harmful, with an increased risk of hypoglycemia and dehydration.[20] ESAIC recommends that children should be encouraged to drink clear fluids until 1 h before induction of anesthesia.[12] The large-scale, international, prospective EUROFAST study, which included more than 300,000 pediatric anesthesia cases, classified participating centers according to their fasting policies as “standard” (≥2 h), “moderately liberal” (≥1 h), and “ultra-liberal” (allowing clear liquid intake until the patient was called to the operating room). The results demonstrated that 1-h fasting or “sip till send” approaches did not increase the risk of aspiration or other complications compared with the traditional 2-h fasting rule. Across all groups, the incidence of confirmed pulmonary aspiration was extremely low (approximately 1 in 5000–10,000 cases) and there were no statistically significant differences between groups. No aspiration-related mortality was reported in any of the children. These data suggest that in healthy pediatric patients, the fasting duration for clear liquids may be safely reduced from 2 to 1 h or even shorter.[21] The liberal clear fluid policy improves comfort, hemodynamic stability, and better perioperative glycemic control.

Emerging Challenge: Glucagon-like Peptide-1 Receptor Agonists

GLP-1 RAs and glucose-dependent insulinotropic peptide receptor agonists (GIP RAs) are increasingly used for diabetes and weight loss management, exerting metabolic effects partly by delaying gastric emptying.[22] GLP-1 RA introduces a growing perioperative challenge, as these agents are associated with high rates of retained gastric contents despite adherence to standard fasting guidelines, thereby increasing the risk of aspiration.[23] The UK National Audit Project 7 (NAP7) identified major airway complications occurring in approximately 1 in 670 general anesthetics (95% confidence interval (CI) 1 in 454–988). Airway complications were the second most common cause of perioperative cardiac arrest (22%), and pulmonary aspiration accounted for 6% of these airway events. Aspiration-related cardiac arrest occurred in approximately 1 in 25,000 cases and carried a mortality exceeding 42%.[24]

GLP-1 RA and GIP RA are endogenous incretin hormones released from the gut in response to luminal glucose levels. Both enhance glucose-dependent insulin secretion, modulate glucagon release, promote lipolysis, activate hypothalamic satiety centers, and slow gastric emptying. Their effects on GI motility involve both peripheral and central mechanisms. GLP-1 receptors on vagal afferents and the myenteric plexus mediate the inhibition of gastric motor function via nitrergic and cAMP pathways, with signal integration in the nucleus tractus solitarius. Vagal inhibition reduces antral contractility, increases fundal compliance and pyloric tone, suppresses gastric and duodenal peristalsis, and decreases acid secretion.[25]

The gastric emptying response shows marked interindividual variability and is dose dependent. Patients with rapid baseline emptying demonstrate pronounced delays, whereas those with diabetic gastroparesis may respond minimally.[26] Short-acting agents produce greater acute slowing and maintain their clinical efficacy, whereas long-acting agents show attenuated effects over time due to tachyphylaxis.[27,28,29,30] Higher doses consistently prolong the gastric emptying half-time.[31]

Clinical evidence and aspiration risk

Many patients presenting for elective surgery while receiving GLP-1 RA may be asymptomatic yet harbor significant residual gastric contents (RGC), creating a “silent full stomach” during anesthesia induction. Early concerns arose from case reports of regurgitation or aspiration despite fasting. In elective endoscopy, GLP-1 RA use increased RGC (odds ratio (OR) 4.86), pulmonary aspiration (OR 2.29), and interrupted procedures (OR 3.22).[32] Propensity-matched data showed higher aspiration pneumonia rates (0.83% vs 0.63%; hazard ratio 1.33).[33] Elective surgery series reported GLP-1 RA users with increased reflux, regurgitation, or aspiration events (OR 10.37), but the rates of tracheal soiling were comparable to those reported in the literature in patients undergoing general anesthesia.[34] However, a meta-analysis found no statistically significant increase in aspiration risk (OR 1.04, 95% CI 0.87–1.25),[23] highlighting the “aspiration paradox” and the limitations of aspiration as a rare outcome endpoint.

Heterogeneity of the guidelines

The perioperative management of GLP-1 RAs is characterized by marked heterogeneity across international guidelines, reflecting differing interpretations of limited evidence and varying prioritization of airway safety versus metabolic stability.[5,19,35] The early ASA guidance in June 2023, prompted by aspiration case reports, adopted a precautionary approach recommending the cessation of daily GLP-1 RAs on the day of surgery and weekly agents for one week. This evolved in the 2024 Multi-Society Update toward risk-stratified, individualized management, with shared decision-making, advising continuation in most elective patients, and withholding only in “high-risk” individuals (dose-escalation phase, high doses, active GI symptoms, or comorbid delayed gastric emptying), with consideration of a 24-h liquid diet.[35]

In contrast, the ESAIC guidance for 2024 remains conservative and indication-based. It recommends holding weekly GLP-1 RAs for one week in diabetes and two weeks in obesity treatment and withholding daily agents on the day of surgery, alongside a universal 24-h clear fluid diet, treating all users as having a potential “full stomach.”[19]

The UK multidisciplinary consensus adopts the most pragmatic stance, advocating the continuation of GLP-1 RAs irrespective of the indication. Brief cessation is pharmacologically ineffective for long-acting agents and risks perioperative hyperglycemia, a proven driver of surgical site infections and acute kidney injury. Instead, it emphasizes shared decision-making, aspiration-risk mitigation, regional anesthesia, advanced airway strategies, and bedside gastric US assessment [Table 1].[5]

Table 1.

Comparison of current guidelines on perioperative management of patients receiving GLP-1 receptor agonists

Domain	SPAQI 2025	ESAIC 2025	ASA 2024 Update	UK/Association of Anaesthetists
Aspiration risk with GLP-1 RAs	High risk—even asymptomatic patients may have a full stomach	Risk acknowledged, but evidence considered limited	Risk acknowledged, but evidence considered limited	Risk acknowledged but incidence considered low
Recommendation on drug discontinuation	GLP-1 RAs may be continued if no significant GI symptoms (severe nausea, vomiting, and unable to tolerate oral intake and do not include fullness or early satiety) are present	Duration of cessation is indication based. Diabetes: Daily dose: stop 1 day before surgery Weekly dose: stop one week before surgery (two weeks in patients with obesity)	Risk stratification: High risk—hold Long acting (weekly dose)—one week prior Short acting (daily dosing)—one day prior Low risk—continue therapy	GLP-1 RAs can generally be continued irrespective of dose, duration, or indication
Fasting strategy	Stop solid food for 24 h; clear liquids allowed; in the absence of significant GI symptoms	24 h clear liquid diet	High-risk patients—24 h liquid diet	Standard fasting is sufficient
Management in symptomatic patients	Treat as full stomach → RSI, gastric US, or postpone surgery if needed	Full stomach approach	Shared decision-making, RSI with tracheal intubation	RSI may be considered if symptoms are present
Role of gastric ultrasound	Strongly recommended, particularly in symptomatic patients or if the drug has not been withheld	May be used, but not mandatory	Recommended but not mandatory	May be considered in high-risk patients
Overall strategy	Conservative: continue drug + extended fasting + airway protection	Individualized, risk-based approach	Individualized, risk-based approach	Liberal: drug continuation with standard fasting

GLP-1 RA=glucagon-like peptide-1 receptor agonist, ESAIC=European Society of Anaesthesiology and Intensive Care, ASA=American Society of Anaesthesiologists, RSI=rapid sequence induction, SPAQI=Society for Perioperative Assessment and Quality Improvement, US=ultrasound, GI=gastrointestinal, UK= United Kingdom

Practical perioperative management

International guidelines show significant heterogeneity regarding the withholding of GLP-1 RA.

1. Adopt risk stratification based on the phase, drug dosage, regime, presence of symptoms, and medical conditions exacerbating delay in gastric emptying.

2. The risks versus benefits of GLP-1 RAs and metabolic consequences, and aspiration risk should be considered.

3. If cessation is considered the best course, an indication-based approach for the duration of cessation should be adopted, and discussion with an endocrinologist should be considered if bridging therapy is necessary or practical to reduce metabolic complications. Cessation for 1–2 weeks still may not guarantee full return of gastric motility.

4. Employ a shared decision-making model and discuss the risk of pulmonary aspiration and mitigation strategies with the patient.

5. In high-risk patients, consider a preoperative liquid or clear fluid diet for 24 h before surgery. For asymptomatic patients, the Society for Perioperative Assessment and Quality Improvement (SPAQI) consensus statement recommends the “24-8-4” Rule, which involves fasting for 24 h for solids, 8 h for high-carbohydrate liquids (≥10% glucose), and 4 h for low-calorie clear liquids.[36]

6. Consider point-of-care US for risk stratification and identification of high-risk patients (1.5 ml/kg or solid contents).

7. Regional anesthesia (peripheral nerve blocks or spinal anesthesia) should be considered as the primary technique, and sedation should be avoided if appropriate.

8. For patients requiring general anesthesia, mitigation strategies should be considered to reduce the risk of pulmonary aspiration during the induction, maintenance, and emergence from anesthesia. These strategies include the use of prokinetics (erythromycin and metoclopramide), orogastric decompression, head-end elevation, prioritization of endotracheal intubation over supraglottic devices, rapid sequence intubation with cricoid pressure, and awake extubation.

9. Patients should generally restart their GLP-1 RA once they have resumed their usual diet and are tolerating oral intake without significant nausea.

As the use of GLP-1 RAs continues to grow, further large-scale RCTs evaluating the effectiveness of various withholding intervals and the efficacy of prokinetic regimens in normalizing gastric volumes are needed. Until such data are available, a “safety-first” paradigm is the most appropriate strategy for protecting this rapidly expanding patient population.

Gastric US as a decision-making tool

Current fasting guidelines are not specifically tailored for patients at an increased risk of delayed gastric emptying or pulmonary aspiration.[37,38] Providers also face the challenge of unclear NPO status, as seen in poor historians, patients with dementia, language barriers, and noncompliant patients.[39,40]

In this context, clinicians rely on guidelines based on fixed fasting intervals for both solid food and liquids. However, evidence indicates that a nonnegligible proportion of patients may still have incomplete gastric emptying despite adherence to these recommendations, and only a minority of these patients have identifiable risk factors for delayed gastric emptying.[41]

Gastric US is a safe, noninvasive, and low-cost point-of-care imaging technique used to assess gastric content and volume, primarily through examination of the gastric antrum. It provides qualitative information (empty stomach, clear fluid, or solid content) as well as quantitative estimates of gastric volume based on antral measurements.[42] However, its accuracy is operator-dependent and influenced by the level of training and experience, with studies demonstrating a potential for misclassification even after standardized training.[43]

In clinical practice, gastric US can assist in identifying patients at increased risk of pulmonary aspiration during anesthesia or procedural sedation. For quantitative assessment, examinations are typically performed in the right lateral decubitus position using a low-frequency curvilinear transducer placed in the epigastrium. The gastric antrum is visualized between the left lobe of the liver and the pancreas, anterior to the aorta. A collapsed, round (“bull’s-eye”) antrum is consistent with an empty stomach [Figure 1], whereas a distended antrum indicates the presence of gastric contents. Clear liquids appear hypoechoic and homogeneous [Figure 2], while solid contents demonstrate a hyperechoic, heterogeneous “frosted glass” pattern [Figure 3]. Measurement of the antral cross-sectional area, particularly in the right lateral decubitus position, allows the estimation of gastric content and volume. This information may contribute to a broader clinical assessment in situations where fasting status is uncertain or where additional risk factors for aspiration coexist. However, gastric content represents only one component of aspiration risk, which is multifactorial and influenced by patient characteristics, surgical context, and airway management. Accordingly, current guidelines do not recommend routine use of gastric US in elective surgery, but rather suggest its selective use in specific clinical scenarios.[44]

Figure 1.

Gastric ultrasound assessment of gastric contents showing an empty stomach with a collapsed, round antrum (bull’s-eye sign). Abbreviations: IVC, inferior vena cava

Figure 2.

Distended antrum consistent with gastric contents; clear fluids are visualized as a homogeneous, hypoechoic pattern. Abbreviations: SMA, superior mesenteric artery

Figure 3.

Gastric ultrasound assessment demonstrating a distended antrum containing solid gastric contents, with a heterogeneous echogenic pattern consistent with solid material. Abbreviations: SMV, superior mesenteric vein

However, current evidence does not support the routine use of gastric US alone to justify the safe use of supraglottic airway devices based solely on gastric volumes that fall within the expected range for fasted patients. This limitation is particularly relevant in patients taking GLP-1 RAs, who frequently have additional risk factors for delayed gastric emptying, making the interpretation of US findings more complex.

Furthermore, the accuracy and reliability of gastric US are significantly reduced in certain patient populations, including those with a history of gastric surgery or large known or occult hiatal hernia. In these situations, altered gastric anatomy can impair visualization and volume estimation, limiting the clinical usefulness of this technique.[45]

The role of prokinetic agents in optimizing preoperative gastric emptying

Clinical evidence supporting prokinetic use

Prokinetic agents are traditionally used to induce gastric emptying and avoid pulmonary aspiration in patients. However, according to the 2011 ESAIC Guidelines on Perioperative Fasting, there is insufficient evidence to recommend the routine use of prophylactic antacids or prokinetics before elective surgery in nonobstetric patients (evidence level 1++, recommendation grade A). The evidence is conflicting; some studies have reported increased gastric pH and decreased gastric residual volume, while others have reported negative results.[20] The same message of inconsistent evidence was delivered in 2017 by the ASA Practice Guidelines on Preoperative Fasting, where the administration of prokinetics and antacids was not recommended as a routine practice but may be considered for high-risk patients to prevent the risk of aspiration.[10] Years have passed since the publication of these guidelines, and new studies have become available in this timeframe, but they are still conflicting. While some data show no impact,[46] some studies show that premedication with erythromycin, metoclopramide, or domperidone accelerates gastric emptying compared to placebo, decreases gastric volume, and reduces PONV before elective surgery.[47,48,49] Promising data have also been reported on emergency and/or improperly fasted patients,[50] including patients with opioid dependence; however, issues in the study design warrant cautious interpretation.

Limitations and safety considerations

Potential specific side effects exist for each prokinetic agent used. Metoclopramide carries the risk of extrapyramidal symptoms, tardive dyskinesia, and QT prolongation. Short perioperative courses are usually safe, but the risk increases with dose and duration.[51] Domperidone has a lower incidence of extrapyramidal symptoms because of its predominant peripheral effect but has been associated with cardiac dysrhythmias (QT prolongation), which led to its removal in Europe from the over-the-counter space to availability only by prescription.[52] The side effects of erythromycin include abdominal pain, nausea, and diarrhea. Caution should be exercised when erythromycin is co-administered with agents that influence or are influenced by cytochrome P450 (CYP) 3A4 variants because of the risk of sudden cardiac death. The use of erythromycin agents should be balanced with the potential for tachyphylaxis due to the downregulation of target receptors and the potential development of bacterial resistance.[52]

Across 39 RCTs of systemic prokinetics for postoperative ileus, no major adverse drug effects were observed.[53] In elective colorectal surgery, GI motility agents (including prokinetics) improve GI recovery without increasing anastomotic leaks, NG reinsertion, or readmission.[54] However, most trials are small and methodologically weak; thus, adverse events may be underestimated, and serious harms cannot be excluded.[53] The risk-benefit balance remains unclear due to heterogeneous populations, drug types, indications, and outcomes.[51] In addition, few anesthesia trials specifically assess aspiration, pneumonia, or survival; most focus on surrogate endpoints (gastric emptying, residual volumes). Short perioperative courses of prokinetic agents appear reasonably safe at the population level and can improve GI transit; however, robust data on serious complications and anesthesia-specific outcomes are limited. The use of prokinetic agents should probably be targeted to high-risk or symptomatic patients, with ECG and drug interaction vigilance.

Future directions

Future advances in perioperative fasting should focus on moving beyond rigid, time-based rules toward individualized, risk-based strategies. Fasting duration alone is an imperfect surrogate for aspiration risk and fails to account for patient heterogeneity, evolving pharmacological therapies, and modern anesthetic practices. Integrating patient-specific factors such as comorbidities, type and urgency of surgery, anesthetic technique, and medications affecting gastric motility, particularly GLP-1 RAs, will be essential for safer and more rational fasting decisions. The wider adoption of point-of-care gastric US is likely to play a central role in this transition. By enabling direct assessment of gastric contents, US can complement clinical judgment and guideline recommendations, especially in high-risk or uncertain situations. In parallel, emerging digital and AI-assisted decision-support tools may help operationalize individualized fasting policies by synthesizing clinical variables, pharmacological profiles, and US findings into practical risk assessments. Such tools have the potential to improve consistency and safety without replacing clinician expertise. Finally, greater harmonization of international guidelines is needed. Current discrepancies between society recommendations reflect uncertainty rather than true disagreement and may contribute to practice variability. Collaborative, evidence-driven consensus efforts will be critical to aligning future guidelines around a shared, patient-centered framework. Ultimately, the goal is not shorter fasting per se, but safer, more personalized perioperative care grounded in physiology rather than tradition.

Conclusions

Prolonged preoperative fasting does not guarantee patient safety and should no longer be regarded as a reliable standalone strategy for aspiration prevention. Contemporary perioperative care requires a balanced approach that integrates aspiration risk with gastric physiology, pharmacological influences, point-of-care imaging, and patient-centered outcomes. As anesthetic practice continues to evolve, the future of preoperative fasting lies not in extending restrictions, but in adopting smarter, individualized assessments that prioritize both safety and patient well-being.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.