Gastric emptying in adults: an overview related to anaesthesia

Gastric Emptying of Orange Juice With and Without Pulp: A Point-of-Care Ultrasound Study

Purpose The American Society of Anesthesiologists (ASA) preoperative fasting recommendations regarding fruit juice with pulp is unclear. In addition, it is debatable whether orange juice without pulp should be treated as a clear liquid. Our objective is to determine the gastric emptying time of orange juice with and without pulp. Methods This is an observational study of gastric emptying time using point-of-care ultrasound (POCUS). Thirty-five adult volunteers were enrolled in this study. Exclusion criteria included pregnancy, diabetes, body mass index > 40 kg/m², previous lower esophageal or upper abdominal surgery, hiatal hernia, and upper gastrointestinal bleed. The study was carried out on three separate days for each volunteer. After fasting a minimum of 8 h, the volunteers were asked to drink 240 ml of water on day 1, orange juice without pulp on day 2, and orange juice with pulp on day 3. Gastric volumes were estimated using gastric antrum cross-sectional area at fasting state, and then 30, 60, 90 120, 180, and 240 min after drinking until the gastric volume returned to baseline. Results A gastric volume of 1.5 mL/kg was defined as a baseline. All subjects' gastric volume returned to baseline 90 min after drinking water. More than 97% of the subjects who drank orange juice without pulp and 93.9% of the subjects who drank orange juice with pulp reached a gastric volume of less than 1.5 mL/kg after 2 h. All subjects' gastric volume returned to baseline 3 h after drinking orange juice with pulp. Conclusions Orange juice without pulp can be treated as a clear liquid in a majority of patients who do not have conditions that would cause delayed gastric emptying. Orange juice with pulp required 3 h to empty.

Effects of Bromocriptine on Glucose and Insulin Dynamics in Normal and Insulin Dysregulated Horses

The objectives of the study were to study the effects of the synthetic ergot alkaloid (EA), bromocriptine, on glucose and lipid metabolism in insulin dysregulated (ID, n = 7) and non-ID (n = 8) mares. Horses were individually housed and fed timothy grass hay and two daily concentrate meals so that the total diet provided 120% of daily DE requirements for maintenance. All horses were given intramuscular bromocriptine injections (0.1 mg/kg BW) every 3 days for 14 days. Before and after 14 days of treatment horses underwent a combined glucose-insulin tolerance test (CGIT) to assess insulin sensitivity and a feed challenge (1 g starch/kg BW from whole oats) to evaluate postprandial glycemic and insulinemic responses. ID horses had higher basal plasma concentrations of insulin (P = 0.01) and triglycerides (P = 0.02), and lower concentrations of adiponectin (P = 0.05) compared with non-ID horses. The CGIT response curve showed that ID horses had slower glucose clearance rates (P = 0.02) resulting in a longer time in positive phase (P = 0.03) and had higher insulin concentrations at 75 min (P = 0.0002) compared with non-ID horses. Glucose (P = 0.02) and insulin (P = 0.04) responses to the feeding challenge were lower in non-ID compared to ID horses. Regardless of insulin status, bromocriptine administration increased hay intake (P = 0.03) and decreased grain (P < 0.0001) and total DE (P = 0.0002) intake. Bromocriptine treatment decreased plasma prolactin (P = 0.0002) and cholesterol (P = 0.10) and increased (P = 0.02) adiponectin concentrations in all horses. Moreover, in both groups of horses, bromocriptine decreased glucose clearance rates (P = 0.02), increased time in positive phase (P = 0.04) of the CGIT and increased insulin concentrations at 75 min (P = 0.001). The postprandial glycemic (P = 0.01) and insulinemic (P = 0.001) response following the oats meal was lower after bromocriptine treatment in all horses. In conclusion, in contrast to data in humans and rodents, bromocriptine treatment reduced insulin sensitivity in all horses, regardless of their insulin status. These results indicate that the physiological effects of EA might be different in horses compared to other species. Moreover, because bromocriptine shares a high degree of homology with natural EA, further investigation is warranted in horses grazing endophyte-infected grasses.

Gastric Residual Volume Assessment by Gastric Ultrasound in Fasting Obese Patients: A Comparative Study

Background

Gastric ultrasound is an emerging tool for preoperative evaluation of gastric content and volume.

Objectives

To assess gastric residual volume in normal-weight and obese patients scheduled for elective surgery.

Methods

This prospective observational study was conducted on 100 patients assigned to two groups of 50 patients each. The obese group included patients with body mass index (BMI) of 30 - 40 and American Society of Anesthesiologists (ASA) grade II and those with BMI > 40 and ASA III without other comorbidities; the normal-weight group included patients with normal BMI and ASA I. Gastric volume was predicted in each group using sonographic measurement of antral cross-sectional area (CSA) in semi-sitting and right lateral positions (RLP); the two groups were compared to assess the risk of aspiration for each group preoperatively.

Results

Despite intergroup differences in antral CSA, the sonographically predicted gastric volume was < 1.5 mL/kg in both groups in both positions. Both groups were at a low risk for aspiration, and 98% of the patients showed grade 0 or 1 in antrum assessments, corresponding to an empty antrum and minimal fluid only in the RLP, respectively. Only 2% of the patients in both groups showed a distended antrum in both positions.

Conclusions

Despite the differences in CSA between obese and normal-weight participants in both positions (obese > normal-weight), both groups showed a low predicted gastric residual volume < 1.5 mL/kg and were at low risk for aspiration, provided that fasting was initiated at least 8 hours before elective surgery.

Gastric content assessed with gastric ultrasound in paediatric patients prescribed a light breakfast prior to general anaesthesia: A prospective observational study

BACKGROUND

A light breakfast has been found to empty from the stomach within 4 hours in healthy volunteers.

AIM

The aim of this study was to investigate whether a light breakfast of yoghurt or gruel empties from the stomach within 4 hours, in children scheduled for general anaesthesia.

METHOD

In this observational cohort study, children aged 1-6 years scheduled for elective general anaesthesia were prescribed free intake of yoghurt or gruel 4 hours prior to induction. They were subsequently examined with gastric ultrasound within 4 hours of ingestion. In case of gastric contents, the gastric antral area was measured, and gastric content volume (GCV) was calculated.

RESULTS

Twenty children were included in the study and the ingested amount of gruel or yoghurt ranged 2.5-25 mL kg^-1 . In 15 cases, the stomach was empty with juxtaposed walls and no further measurements were made. In four cases, there was fluid present in the stomach, but the calculated gastric contents were <0.5 mL kg^-1 . One patient had solids in the stomach, and GCV in this patient was calculated to 2.1 mL kg^-1 . The patient with solids present had ingested 25 mL kg^-1 of gruel 4 hours prior to assessment. The planned procedure was therefore delayed 1 hour. There were no cases of pulmonary aspiration or vomiting.

CONCLUSION

A light breakfast 4 hours prior to induction may be considered, but there is need for further studies on safe limits for the volume ingested.

Operative fasting guidelines and postoperative feeding in paediatric anaesthesia-current concepts

Preoperative fasting period is the prescribed time prior to any procedure done either under general anaesthesia, regional anaesthesia or sedation, when oral intake of liquids or solids are not allowed. This mandatory fasting is a safety precaution that helps to protect from pulmonary aspiration of gastric contents which may occur any time during anaesthesia. We searched PUBMED for English language articles using keywords including child, paediatric, anaesthesia, fasting, preoperative, gastric emptying. We also hand searched references from relevant review articles and major society guidelines. Association of Paediatric Anaesthesiologists of Great Britain and Ireland (APAGBI), the French Language Society of Paediatric Anaesthesiologists and the European Society of Paediatric Anesthetists recommends clear fluid intake upto one hour prior to elective surgery unless specific contraindications exists. Current guidelines recommend fasting duration of 4 hours for breastmilk, 6 hours for milk and light meals and 8 hours for fatty meals. The European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines recommend that oral intake can be initiated within hours of surgery in most patients. While fluids can be started almost immediately, the introduction of solids should be done more cautiously.

Enhanced recovery after surgery-Preoperative fasting and glucose loading-A review

In this review, we explore the rationale and history behind the practice of preoperative fasting in elective surgery including the gradual move toward longer fasting and the more recent change in direction of practice. Gastric emptying physiology and the metabolic effects of prolonged fasting and carbohydrate loading are examined. Most recent guidelines related to these topics are discussed and practical recommendations for implementing these guidelines are suggested.

Normal gastric emptying time of a carbohydrate-rich drink in elderly patients with acute hip fracture: a pilot study

Background

Guidelines for fasting in elderly patients with acute hip fracture are the same as for other trauma patients, and longer than for elective patients. The reason is assumed stress-induced delayed gastric emptying with possible risk of pulmonary aspiration. Prolonged fasting in elderly patients may have serious negative metabolic consequences. The aim of our study was to investigate whether the preoperative gastric emptying was delayed in elderly women scheduled for surgery due to acute hip fracture.

Methods

In a prospective study gastric emptying of 400 ml 12.6% carbohydrate rich drink was investigated in nine elderly women, age 77–97, with acute hip fracture. The emptying time was assessed by the paracetamol absorption technique, and lag phase and gastric half-emptying time was compared with two gender-matched reference groups: ten elective hip replacement patients, age 45–71 and ten healthy volunteers, age 28–55.

Results

The mean gastric half-emptying time in the elderly study group was 53 ± 5 (39–82) minutes with an expected gastric emptying profile. The reference groups had a mean half-emptying time of 58 ± 4 (41–106) and 59 ± 5 (33–72) minutes, indicating normal gastric emptying time in elderly with hip fracture.

Conclusion

This pilot study in women with an acute hip fracture shows no evidence of delayed gastric emptying after an orally taken carbohydrate-rich beverage during the pre-operative fasting period. This implies no increased risk of pulmonary aspiration in these patients. Therefore, we advocate oral pre-operative management with carbohydrate-rich beverage in order to mitigate fasting-induced additive stress in the elderly with hip fracture.

Trial registration

ClinicalTrials.gov NCT02753010. Registered 17 April 2016, retrospectively. 

High-Risk Residual Gastric Content in Fasted Patients Undergoing Gastrointestinal Endoscopy: A Prospective Cohort Study of Prevalence and Predictors

In this prospective cohort study, we examined the residual gastric contents of 255 fasted patients undergoing gastrointestinal endoscopy. The volume and pH of residual gastric contents collected by suction under direct visualisation during gastroscopy were accurately quantified. All patients completed the minimum two-hour fast for clear fluids and 97.2% of patients completed the minimum six-hour fast for solids. High-risk residual gastric content, defined as volume >25 ml and pH <2.5, was present in 12.2% (95% CI 8.7% to 16.7%) of patients. We used multiple logistic regression analysis to identify demographic and clinical factors associated with high-risk residual gastric content. The odds of having high-risk residual gastric content were reduced with increase in age (adjusted odds ratio 0.77, 95% CI 0.61 to 0.96, P=0.0230), and use of a proton pump inhibitor or histamine type 2 receptor antagonist (adjusted odds ratio 0.24, 95% CI 0.10 to 0.55, P=0.0013), and were increased in male patients (adjusted odds ratio 2.36, 95% CI 1.06 to 5.28, P=0.0348). Notably, residual gastric content was classified as high-risk in 20.4% of patients who did not take a proton pump inhibitor or histamine type 2 receptor antagonist versus only 5.6% of those who did. Our findings suggest that, despite currently recommended fasting, males presenting for endoscopy are more likely to have high-risk gastric content than females, and that the incidence appears to be reduced with increasing age, and by the use of proton pump inhibitors or histamine type 2 receptor antagonists, we were unable to confirm or exclude an effect of body mass index, peptic pathology, diabetes or other clinical or demographic factors in our study population.

The effect of ethanol on the release of opioids from oral prolonged-release preparations

Recent experience has prompted the US FDA to consider whether ethanol ingestion may modify the release characteristics of prolonged-release formulations, where dose dumping may be an issue for patient safety. The influence of ethanol on the in vitro release of opioid drugs from some prolonged-release formulations utilizing different release technologies was examined. Results indicated that the prolonged-release mechanisms remained intact under the testing conditions, although one product showed initial sensitivity to ethanol in its release characteristics. Nevertheless, in this case, extrapolation of the findings to likely outcome in vivo indicated no risk of dose-dumping. It is proposed that prolonged-release medicinal products should be tested during development to ensure robustness to the effects of ethanol on drug release.

Modern preoperative fasting guidelines: a summary of the present recommendations and remaining questions

This chapter is complementary to the others in this volume focusing on preoperative fasting routines. In it we discuss some of the issues in need of more research to define best practice. One of these is the role of fasting in emergency patients. Modern preoperative fasting recommendations almost exclusively deal with elective patients. In emergency patients preoperative fasting cannot secure gastric emptying to reduce the risk of pulmonary aspiration. Hence, surgery should be timed according to the urgency of the situation, and the patient should always be treated as if the stomach was full. More data are needed to better define what is going on in the gastrointestinal tract during the perioperative period in these patients. In certain patient groups--such as patients with diabetes, gastro-oesophageal reflux disease and/or obesity--the data are insufficient to give complete guidance to best practice. Preoperative fasting guidelines also affect fluid balance and perioperative fluid management, a topic of debate in recent years. In addition, carbohydrate-enriched fluids for oral use in the preoperative phase have been shown to have a positive effect on postoperative metabolism. Recent studies also suggest that the immune system would be less affected by surgery with such preparations. Last but not least, new scientific evidence alone is not enough to change daily practice. Active implementation of new evidence is also needed. To improve perioperative care, anaesthesiologists, surgeons and the nursing staff must work together.

Pre-operative fasting guidelines: an update

Liberal pre-operative fasting routines have been implemented in most countries. In general, clear fluids are allowed up to 2 h before anaesthesia, and light meals up to 6 h. The same recommendations apply for children and pregnant women not in labour. In children <6 months, most recommendations now allow breast- or formula milk feeding up to 4 h before anaesthesia. Recently, the concept of pre-operative oral nutrition using a special carbohydrate-rich beverage has also gained support and been shown not to increase gastric fluid volume or acidity. Based on the available literature, our Task Force has produced new consensus-based Scandinavian guidelines for pre-operative fasting. What is still not clear is to what extent the new liberal fasting routines should apply to patients with functional dyspepsia or systematic diseases such as diabetes mellitus. Other still controversial areas include the need for and effect of fasting in emergency patients, women in labour and in association with procedures done under 'deep sedation'. We think more research on the effect of various fasting regimes in subpopulations of patients is needed before we can move one step further towards completely evidence-based pre-operative fasting guidelines.

Strategies for prophylaxis and treatment for aspiration

The absolute incidence of aspiration is difficult to define because of its relatively low occurrence and difficulty in diagnosis. The gastric volume predisposing to aspiration is larger than 30 ml. Fasting times for fluids have reduced; however, a large meal may require 9 hours of preoperative fasting. Preoperative carbohydrate-enriched beverages may attenuate postoperative catabolism. Aspiration occurs most frequently during induction and laryngoscopy. Awake fibre-optic intubation may be a suitable alternative in high-risk cases for aspiration. The role of cricoid pressure in anaesthesia needs re-evaluation as radiological and clinical evidence suggest that it may be ineffective and may impede intubation and ventilation. Chemoprophylaxis does not reduce the severity of aspiration pneumonitis as gastric bile is unaffected by these agents and induces a worse pneumonitis than gastric acid. Patients may be discharged home 2 hours after aspirating provided they are clinically unaffected and have postoperative surveillance.

Preoperative assessment

Although anaesthetic and surgical procedures should be individualised for every patient, in practice many preoperative protocols and routines are used generally. In this article, we aim to emphasise: why preoperative assessment is important; how it should be done, and by whom; what can be expected; and the importance of test selection based on patients' needs and on scientific evidence of effectiveness. We outline the roles of preoperative medical assessment in otherwise healthy patients. Clinical history, preoperative questionnaires, physical examination, routine tests, individual risk-assessment, and fasting policies are investigated by review of published work. Cost of routine preoperative assessment, the anaesthetist's legal responsibility, and patients'views in the preoperative process are also considered. A thorough clinical preoperative assessment of the patient is more important than routine preoperative tests, which should be requested only when justified by clinical indications. Moreover, this practice eliminates unnecessary cost without compromising the safety and quality of care. Education and training of medical doctors should be more scientifically guided, emphasising the relevance of effectiveness, and cost-effectiveness in clinical decision-making and complemented by audit.

Preoperative fasting

BACKGROUND AND METHODS

To avoid pulmonary aspiration, fasting after midnight has become standard in elective surgery, but recent studies have found no scientific support for this practice. Several anaesthesia societies now recommend a 2-h preoperative fast for clear fluids and a 6-h fast for solids in most elective patients. The literature supporting such fasting recommendations was reviewed.

RESULTS

The recommendations are safe and improve well-being before operation, mainly by reducing thirst. A carbohydrate-rich beverage given before anaesthesia and surgery alters metabolism from the overnight fasted to the fed state. This reduces the catabolic response (insulin resistance) after operation, which may have implications for postoperative recovery.

CONCLUSION

Most patients having elective operations can be allowed a free intake of clear fluids up to 2 h before anaesthesia. Preoperative carbohydrates reduce postoperative insulin resistance.

Double-blind, randomized study of the effect of cisapride on gastric emptying in critically ill patients

OBJECTIVES

To investigate the absorption of the gastrokinetic drug, cisapride, and effect of cisapride on gastric emptying in critically ill patients; and to assess the usefulness of clinical signs of gastric emptying.

DESIGN

Prospective, randomized, controlled study.

SETTING

Medical/surgical/trauma intensive care unit (ICU) in a university hospital.

PATIENTS

Twenty-seven consecutively enrolled patients, aged 18 to 65 yrs, with normal hepatic and renal biochemistry who were not receiving enteral nutrition and who had no contraindications to enteral nutrition. These patients were expected to stay in the ICU for at least 4 days.

INTERVENTIONS

Patients were randomized to receive either placebo or rectal cisapride, 60 mg initially followed by two doses of 30 mg at 8-hr intervals.

MEASUREMENTS AND MAIN RESULTS

Gastric emptying was estimated, using acetaminophen absorption on day 1 of the study. Placebo or cisapride was administered and a second acetaminophen absorption test for gastric emptying was carried out on day 2,24 hrs after the first test. Four patients were excluded because of incomplete data. Statistical analysis was performed, using the area under the acetaminophen absorption curve from 0 to 60 mins as the primary measure of gastric emptying. There was no significant change in the area under the acetaminophen absorption curve from 0 to 60 mins from day 1 to day 2 in patients who received placebo or cisapride. Using the combination of the time to maximum acetaminophen concentration (< or = 30 mins) with a maximum concentration (> 12 mg/L) to define "normal" emptying, on day 1, four of the 11 placebo patients had the "normal" gastric emptying, and by day 2, five patients fulfilled this criterion. Before administration of cisapride, four of the 12 patients fulfilled this criterion, whereas nine fulfilled the criterion after receiving cisapride. There was a large variation in gastric emptying from day 1 to day 2; a power calculation suggests that approximately 150 patients would have to be studied to determine the effect of cisapride. There was no correlation between gastric emptying and the volume of gastric aspirate or the presence of bowel sounds. Plasma cisapride concentrations 4 hrs after the third dose, during the second acetaminophen absorption test, averaged 53 ng/mL (range 20 to 111).

CONCLUSIONS

Rectal cisapride in the dose given achieved average plasma concentrations similar to those concentrations achieved in healthy subjects after 30 mg of cisapride rectally. There is a large variation in gastric emptying from one day to the next and large numbers of patients are required to determine if cisapride administration improves early gastric emptying in critically ill patients. The volume of gastric aspirate and the presence of bowel sounds do not correlate with gastric emptying.

Routine preoperative gastric emptying is seldom indicated. A study of 85,594 anaesthetics with special focus on aspiration pneumonia

BACKGROUND

The aim of this study was to determine the incidence and severity of pulmonary aspiration of gastric contents during anaesthesia, to determine the short- and long-term morbidity, and to evaluate present routines for preoperative gastric emptying. During the study period, preoperative gastric emptying was done only when intestinal obstruction was suspected.

METHODS

We routinely record prospectively all problems during and after anaesthesia by means of a database. All data for the 5 years from 1989 to 1993, a total of 85594 anaesthetic procedures, were analyzed. The hospital charts were also reviewed for those patients where aspiration to the lungs had occurred.

RESULTS

Pulmonary aspiration of gastric contents was detected in 25 cases; all occurred in patients receiving general anaesthesia. The incidence was 4.1 times higher in emergency procedures than in electives. There were no aspirations in 30199 patients receiving regional anaesthesia. The complication occurred in all phases of anaesthesia, but clinical morbidity was low in most cases. Three cases showed serious morbidity immediately after the event, but recovered. Two cases showed serious long-term morbidity, but also recovered completely. No patients died. No cases, except possibly one, might have been prevented by stricter routines for preoperative gastric emptying.

CONCLUSION

We found a low incidence of pulmonary aspiration. When it occurs, it carries a low risk for serious morbidity. Emergency cases for general anaesthesia are most at risk. Regional anaesthesia is considered safe. There is no evidence that preoperative gastric emptying should be routinely done in emergency cases, except in patients with suspected ileus/ subileus.

Gastric emptying of a light hospital breakfast. A study using real time ultrasonography

While intake of clear fluids 2-3 h before surgery is considered safe as it does not influence gastric content, it is not known if the same applies to a light breakfast meal. We therefore studied gastric emptying of a light breakfast in healthy, female volunteers without evidence of gastrointestinal motility disorders. The test meal consisted of one slice of buttered toast with jam, one cup of coffee without milk or sugar and one glass of pulp-free orange juice taken together with a paracetamol mixture. Using gastric ultrasonography, the stomach was identified without problems in all subjects, and gastric emptying curves using changes in gastric antral area and serum-paracetamol were obtained. Emptying of the fluid phase started immediately after intake of the meal. All subjects had solid particles in the stomach 120 min after the meal, 3 patients were considered empty after 180 min, 6 after 210 min and all after 240 min. The gastric antral area returned to fasting value significantly faster than the disappearance of solid particles; median 150 min versus 210 min; P = 0.01. Our results show that in healthy subjects the stomach cannot be considered empty for solid particles the first 4 h after a light breakfast meal. To secure some safety limits, we suggest a 6-h mandatory preoperative fast after a light breakfast.

Preoperative assessment and postoperative management of the elderly surgical patient

The population undergoing surgery is aging and this trend will continue for many decades to come. Better anaesthetic and surgical techniques are lowering the risk-benefit ratio for surgery, making it an increasingly attractive treatment option. Good preoperative assessment and postoperative management form an integral part of strategies to minimise morbidity and mortality while maximising hospital efficiency.

[Perioperative fasting in children: current data]

Perioperative fasting aims at decreasing the incidence of gastric content inhalation during anesthesia. Current knowledge concerning gastric emptying and the epidemiology of pulmonary aspiration authorizes new perioperative fasting guidelines. If prolonged fasting does not guarantee gastric emptiness at the induction of anesthesia, shortening preoperative fasting by allowing clear fluids two hours before surgery does not modify gastric content and does not increase the risk of gastric content aspiration, while enhancing the patient comfort by reduction of the fasting period. On the other hand, after surgery, the mandatory intake of water significantly increases the incidence of postoperative vomiting. Therefore new guidelines may be applied for children operated in ambulatory surgery settings: 1) clear fluids may be allowed until 2-3 hours before operation, 10 ml.kg-1, or even ad libitum for some authors (by clear fluids one means water, tea, coffee, apple juice, syrup with water); 2) drinking is not absolutely necessary before discharge from day care surgery unit and should be left to the child's own assessment.