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

The Effect of Premedication on the Incidence of Gastroesophageal Reflux in 270 Dogs Undergoing General Anesthesia

The aim of this prospective, non-randomized study was to evaluate the effect of nine different premedication medications on the incidence of gastroesophageal reflux (GOR) in anesthetized dogs. Two hundred and seventy dogs undergoing non-intrathoracic, non-intrabdominal elective surgeries or invasive diagnostic procedures were included in the study, and were allocated into nine groups (30 dogs/group) defined by the type of premedication administered. Premedication consisted of dexmedetomidine with either morphine, pethidine or butorphanol, acepromazine with either one of the three opioids or midazolam with one of the above-mentioned opioids. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. Esophageal pH was measured with the use of a pH-meter electrode and a pH-value less than 4 and over 7.5 was considered to be GOR. The study revealed that 119/270 (44.1%) dogs experienced a reflux episode during anesthesia. The incidence of reflux did not differ among groups (p = 0.117). In group AB the dogs refluxed within 10 min of the beginning of pH-measurements, in comparison with group DB in which dogs refluxed within 30 min (p = 0.029). Invasive diagnostic procedures had a lower incidence of GOR in comparison to castrations (p = 0.09). The outcome of the study suggests that none of the opioids used increased the incidence of GOR in anesthetized dogs.

Factors Affecting Intraoperative Gastro-Oesophageal Reflux in Dogs and Cats

Simple Summary

Gastro-oesophageal reflux (GOR) is an anaesthetic complication that causes oesophageal inflammation and stricture in animals. The aim of this systematic review is to systematically identify the effect of preoperative fasting duration and drugs (anaesthetic and nonanaesthetic agents) on GOR in dogs and cats during anaesthesia. Seven studies were included in the meta-analysis. Many factors seem to affect the development of GOR in dogs and cats. However, there is a limited number of studies investigating these factors, and as the level of evidence is low-to-medium, no reliable conclusions can be extracted.

Abstract

In animals, gastro-oesophageal reflux (GOR) may occur during anaesthesia, and it can lead to severe consequences such as oesophagitis and oesophageal stricture. This systematic review investigates the effect of fasting duration and anaesthetic and nonanaesthetic drugs on GOR in dogs and cats during general anaesthesia. Fifteen clinical studies met the inclusion criteria in this systematic review. In thirteen studies the population was dogs, while in two studies the population was cats. In the meta-analysis, seven studies were included. Four studies on the effect of fasting duration on GOR in dogs were included in the meta-analysis. In total, 191 dogs had a fasting duration less than 5 h, while 311 dogs had a fasting duration more than 5 h. The heterogeneity of the studies was high and statistically significant (p = 0.0002, I² = 85%), but the overall effect was statistically nonsignificant (p = 0.82, odds ratio = 0.81, 95% CI 0.15, 4.26), in favour of the low fasting duration (<5 h). Concerning the effect of antacids on GOR, three studies were included in the meta-analysis. The heterogeneity of the studies was low and nonsignificant (p = 0.13, I² = 52%) and the overall effect was statistically nonsignificant (p = 0.24). The low number of studies and the diverse factors affecting the incidence of reflux prevented us from reaching valuable conclusions on the risk factors for GOR.

Evaluation of gastric residual volume in fasting diabetic patients using gastric ultrasound

BACKGROUND

Diabetic patients are claimed to have high risk of delayed gastric emptying; however, the evidence concerning residual gastric volume in fasting diabetic patients is not consistent. The aim of this work is to evaluate residual gastric volume in fasting diabetic patients for elective surgery.

METHODS

Fifty patients scheduled for elective surgery under general anaesthesia were included in the study. The study included 25 patients with at least 6-year history of diabetes and 25 healthy controls. Gastric ultrasound was performed to measure antral cross-sectional area in semi-sitting and right lateral positions. Nasogastric tube was inserted after induction of anaesthesia to aspirate and calculate the volume of gastric contents. Both study groups were compared according to antral cross-sectional area, residual gastric volume, risk of aspiration, in addition to demographic data.

RESULTS

The diabetic group showed higher median (quartiles) antral cross-sectional area (13.8 [9.5-19.5] mm² versus 8.8 [5.5-10.5] mm² , P < 0.001), and higher calculated gastric residual volume, (177 [96-275] mL versus 83 [50-109] mL, P < 0.001) compared to the control group. The diabetic group also showed higher aspirated volume through the nasogastric tube compared to the control group (150 [85-210] mL versus 75 [35-87] mL, P < 0.001). The correlation was very good between calculated residual gastric volume using ultrasound measures and volume of aspirated gastric contents through nasogastric tube.

CONCLUSION

Patients with long standing diabetes showed higher residual gastric volume compared to healthy controls after fasting 8 hours for elective surgery.

Influence of Eating Schedule on the Postprandial Response: Gender Differences

Ingestion of a meal induces conscious sensations depending of the characteristics of the meal and the predisposition of the eater. We hypothesized that the eating schedule plays a conditioning role, specifically, that an extemporaneous meal is less rewarding than when eaten at the habitual schedule. We conducted a randomized parallel trial in 10 women and 10 men comparing the responses to a consistent savoury lunch-type meal (stewed beans) eaten at the habitual afternoon schedule or at an unconventional time in the morning. Schedule and gender differences were analyzed by repeated measures analysis of covariance. In women, the sensory experience induced by the probe meal, particularly postprandial satisfaction, was weaker when eaten at an unconventional time for breakfast. Men were resilient to the schedule effect and experienced the same sensations regardless of the timing of ingestion; the effect of the eating schedule was significantly more pronounced in women for fullness (F(1,55) = 14.9; p < 0.001), digestive well-being (F(1,36.8) = 22.3; p < 0.001), mood (F(1,12.4) = 13.8; p < 0.001), and anxiety (F(1,11.9) = 10.9; p = 0.001). No differences in the physiological responses induced by the afternoon and morning meals were detected either in women or men. Our data indicate that women are more susceptible to changes in meal schedule than men.

Qualitative and quantitative ultrasound assessment of gastric content

Objective:

Pulmonary aspiration of the gastric contents is one of the most feared complications in anesthesia. Its prevention depends on preoperative fasting as well as identification of risky patients. A reliable diagnostic tool to assess gastric volume is currently lacking. The aim of this study performed on volunteers was to evaluate the feasibility of ultrasonography to identify qualitative and quantitative gastric content.

Method:

A standardized gastric scanning protocol was applied on 67 healthy volunteers to assess the gastric antrum in four different situations: fasting, after ingesting clear fluid, milk and a solid meal. A qualitative and quantitative assessment of the gastric content in the antrum was performed by a blinded sonographer. The antrum was considered either as empty, or containing clear or thick fluid, or solids. Total gastric volume was predicted based on a cross-sectional area of the antrum. A p-value less than 0.05 was considered statistically significant.

Results:

For each type of gastric content, the sonographic characteristics of the antrum and its content were described and illustrated. Sonographic qualitative assessment allowed to distinguish between an empty stomach and one with different kinds of meal. The predicted gastric volume was significantly larger after the consumption of any food source compared to fasting.

Conclusion:

Bedside sonography can determine the nature of gastric content. It is also possible to estimate the difference between an empty gastric antrum and one that has some food in it. Such information may be useful to estimate the risk of aspiration, particularly in situations when prandial status is unknown or uncertain.

Ultrasonography in gastroenterology

Ultrasonography (US) is a safe and available real-time, high-resolution imaging method, which during the last decades has been increasingly integrated as a clinical tool in gastroenterology. New US applications have emerged with enforced data software and new technical solutions, including strain evaluation, three-dimensional imaging and use of ultrasound contrast agents. Specific gastroenterologic applications have been developed by combining US with other diagnostic or therapeutic methods, such as endoscopy, manometry, puncture needles, diathermy and stents. US provides detailed structural information about visceral organs without hazard to the patients and can play an important clinical role by reducing the need for invasive procedures. This paper presents different aspects of US in gastroenterology, with a special emphasis on the contribution from Nordic scientists in developing clinical applications.

Comparison of the pharmacokinetics of erlotinib administered in complete fasting and 2 h after a meal in patients with lung cancer

BACKGROUND

The recommended dose of erlotinib is 150 mg daily either 1 h before a meal (complete fasting) or 2 h after a meal (2 h post-meal), because of the food effect.

METHODS

We conducted a cross-over pharmacokinetic study to compare the fed bioequivalence in the two conditions.

RESULTS

Twenty-three patients with non-small cell lung cancer were included in the analysis. AUC0-24 and C max in the 2-h post-meal status were significantly higher than in the complete fasting status (GMR = 1.33, P < 0.001; GMR = 1.44, P < 0.001, respectively). However, because the concentration of erlotinib did not reach the steady state within 7 days in the complete fasting state, we conducted analyses only on day 14, which showed no significant difference in AUC0-24 or C max between the two conditions. The more rapid increase in AUC0-24 and C min did not produce any earlier and more severe toxic events.

CONCLUSION

The AUC0-24 increased significantly faster (48-53 % greater) in the 2-h post-meal status than in complete fasting status, which suggested that the two gastric emptying states might differ in their absorption. However, there was no clinically significant difference in bioavailability or toxicity between the two clinically used fed conditions at least in 14 days.

Perioperative pulmonary aspiration is infrequent and low risk in pediatric anesthetic practice

Recent studies have reported perioperative pulmonary aspiration in pediatric practice to be an uncommon problem associated with low morbidity and mortality. This paper examines the recent publications in both the adult and pediatric literature and looks at some of the potential risk factors involved, both patient and anesthetic, in the development of aspiration of gastric contents. We also look at the risk of severe morbidity following pulmonary aspiration and speculate on possible reasons behind the assertion that pulmonary aspiration in pediatric anesthetic practice is rare and a low-risk event.

Ultrasound assessment of gastric content and volume

Pulmonary aspiration of gastric content is a serious anaesthetic complication that can lead to significant morbidity and mortality. Aspiration risk assessment is usually based on fasting times. However, fasting guidelines do not apply to urgent or emergent situations and to patients with certain co-morbidities. Gastric content and volume assessment is a new point-of-care ultrasound application that can help determine aspiration risk. This systematic review summarizes the current literature on bedside ultrasound assessment of gastric content and volume relevant to anaesthesia practice. Seventeen articles were identified using predetermined criteria. Studies were classified into those describing the sonographic characteristics of different types of gastric content (empty, clear fluid, solid), and those describing methods for quantitative assessment of gastric volume. A possible algorithm for the clinical application of this new tool is proposed, and areas that require further research are highlighted.

Effect of the preliminary hydration on gastric emptying time for water in healthy volunteers

BACKGROUND

International guidelines allow healthy patients to drink clear liquid up to 2 h before general anesthesia. Recently, MRI measurements have been used for tracking gastric volume in humans. Hence, we used MRI to examine the gastric emptying rate of water in healthy volunteers with or without prior water loading.

METHODS

Fifteen healthy volunteers were enrolled. The participants had MRI examinations on separate days under two different protocols: The preliminary hydration protocol (group H) and the water restriction protocol (group R). After the intake of water, MR imaging was performed every 10 min for 60 min. The gastric content was outlined as area of interest (AOI), and the AOI area of each slice was summated to calculate the volume of gastric contents.

RESULTS

The 50% reduction time of gastric volume in group R and group H was 18+/-9 and 16+/-8 min (mean+/-SD), respectively. There were no significant changes between the two groups.

CONCLUSION

The gastric emptying time for water evaluated with MRI was not affected by preliminary hydration, which shows the safety of repeated oral hydrations in the pre-operative period.

Modern fasting guidelines in children

Pediatric fasting guidelines are intended to reduce the risk of pulmonary aspiration of gastric contents and facilitate the safe and efficient conduct of anesthesia. Recent changes in these guidelines, while assuring appropriate levels of patient safety, have been directed at improving the overall perioperative experience for infants, children, and their parents. Now after nearly 15 years of practice worldwide, the relative safety and benefits of allowing clear liquids up to 2 hr prior to anesthesia for otherwise healthy children are well established. Shortened fasting periods for breast milk (3 hr), formula (4 hr) and light meals (6 hr) are supported by accumulated experience and an evolving literature that includes evidence of minimal gastric fluid volumes (GFVs) at the time of surgery. Ideal fasting intervals for children with disorders that may affect gastrointestinal transit have yet to be determined.

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.

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.

Gastroesophageal reflux and aspiration of gastric contents in anesthetic practice

General anesthesia may predispose patients to aspiration of gastroesophageal contents because of depression of protective reflexes during loss of consciousness. In addition, some patients may be at increased risk of pulmonary aspiration because of retention of gastric contents caused by pain, inadequate starvation, or gastrointestinal pathology resulting in reduced gastric emptying and gastroesophageal reflux. Despite increasing knowledge of the problems associated with aspiration, the relatively small incidence and associated mortality rates in the perioperative period do not appear to have changed markedly over the last few decades. In this review article, the physiological factors associated with an increased risk of gastroesophageal reflux and aspiration are considered together with some of the methods that are used to prevent aspiration. In particular, preoperative starvation, the use of drugs designed to increase gastric pH, recent developments in airway devices, and appropriate application of cricoid pressure are critically appraised.

Changing preoperative fasting policies. Impact of a national consensus

BACKGROUND

Liberalisation of preoperative fasting rules has been discussed and recommended in the anaesthesia literature in recent years. In Norway, a national consensus on this issue was reached in 1993. The aim of the present study was to investigate whether a national consensus on fasting recommendations led to a change in fasting policies in Norwegian anaesthesia departments.

METHODS

A questionnaire on preoperative fasting routines was sent to all Norwegian anaesthesia departments in 1993 and repeated in 1996.

RESULTS

Written local guidelines for preoperative fasting were present in 85% of the institutions in both surveys. Of the hospitals, 69% had changed their local guidelines after the national consensus. In 1996 more hospitals allowed less than 6 h fasting for clear liquids in children (93% versus 71% in 1993; P < 0.005). A similar tendency was noted in adults (79% versus 63% in 1993; P = 0.1). In contradiction to the national guidelines, 31% of the departments reported that they allowed less than 6 h fasting after a light breakfast in the morning of surgery in 1996. The corresponding number for 1993 was 21% (ns).

CONCLUSION

The new, consensus-based national fasting guidelines have been associated with a change towards more liberal fasting policies in Norwegian departments of anaesthesia. However, as not all local changes were supported by the national consensus, other sources of information were used when local policies were decided.

Sonographic observations of the gastroduodenal junction in neonatal piglets

Knowledge of the function of the gastroduodenal junction is important, as changes in its motility are associated with gastrointestinal disorders. Sonographic observations were made of the stomach and duodenum of 19 neonatal piglets, 2-6 d of age. Contractions of the stomach and duodenum were identified clearly; the overall rate of gastric contractions was about 4 min-1. The percentage of contractions in which there was a closure of the terminal pyloric antrum and pyloric canal varied, being 57.2% +/- 4.6% in the first postprandial hour and 43.1% +/- 3.0% in the third. Antegrade flow of digesta principally occurred preceding a closure of the pyloric antrum and canal. During contractions of the pyloric antrum, the torus pyloricus moved caudally to fill the lumen of the pyloric canal. Our sonographic method provided a noninvasive technique for studying the form and function of gastroduodenal motility in the neonate, suitable for investigating factors that alter gastric emptying.