The ‘full stomach’: full time for sloppy terminology?

The role of supraglottic airway devices in obstetric anaesthesia

PURPOSE OF REVIEW

To discuss the role of supraglottic airway devices as rescue and primary airway devices in pregnant patients.

RECENT FINDINGS

General anaesthesia in pregnant patients is associated with increased incidence of difficult and failed intubation, especially when performed for caesarean deliveries. The Difficult Airway Society and the Obstetric Anaesthetists' Association guidelines for the management of failed intubation recommend the use of second-generation supraglottic airway devices as a rescue airway strategy when failed intubation occurs. This practice is now widely accepted and embedded in routine teaching and clinical practice. On the other hand, there is little but growing evidence describing the use of supraglottic airway devices as the primary airway device and an alternative to endotracheal intubation for patients undergoing elective and emergency caesarean deliveries under general anaesthesia. Most of the published research supporting this practice was done on carefully selected patients who were nonobese and who did not have gastroesophageal reflux or anticipated difficult airway. Despite demonstrating high insertion success rates and low complication rates, these studies were underpowered and have thus far, failed to provide robust data on the true risk of aspiration in this setting.

SUMMARY

Based on current scientific data, the evidence for the safe use of supraglottic airway devices as primary airway devices during general anaesthesia for caesarean deliveries is not compelling. However, their use as rescue airway devices remains a well established strategy supported by international guidelines.

Point-of-Care Ultrasound to Assess Gastric Content in Pediatric Emergency Department Procedural Sedation Patients

OBJECTIVES

There is debate regarding the timing of procedural sedation and analgesia (PSA) in relation to fasting status. Point-of-care ultrasound (POCUS) provides the ability to measure gastric content and is being used as a surrogate for aspiration risk in anesthesia. We sought to evaluate the gastric content of pediatric emergency department (PED) patients undergoing PSA using POCUS.

METHODS

We performed a prospective observational study using a convenience sample of pediatric patients undergoing PSA between July 1, 2018, and June 30, 2019. Following a brief history, gastric content was measured using POCUS in both supine and right lateral decubitus positions at 2-hour intervals until the time of PSA. Qualitative content and calculated volume were classified based on the Perlas Model of anesthesia "Risk" assessment.

RESULTS

Ninety-three patients were enrolled with 61.3% male and mean age of 6.5 years. Gastric content was determined in 92 patients. There were 79.3% that had "high risk" content at the time of PSA, with a median fasting time of 6.25 hours and no serious adverse events. Fasting duration had a weak to moderate ability to predict "risk" category (area under the curve = 0.73), with no patient (n = 17) who underwent multiple evaluations awaiting PSA progressing from "high" to "low risk."

CONCLUSIONS

The majority of PED patients undergoing PSA at our institution had "high risk" gastric content with no clinically significant change occurring during serial evaluations. This calls into question the utility of delaying PSA based upon fasting status and lends support to a more comprehensive risk-benefit approach when planning pediatric PSA.

Evaluation of gastric contents using ultrasound in full-term pregnant women fasted for 8 h: a prospective observational study

BACKGROUND

We aimed to evaluate the gastric volume and contents after an 8-h fasting period in full-term, non-laboring, pregnant women following a standardized meal.

METHODS

In this prospective observational study, we included full-term pregnant women scheduled for elective cesarean delivery. The participants were instructed to fast after a standardized meal (apple juice, bread, and cheese). Participants were scanned in the semi-recumbent and right-lateral positions 8 h after the standardized meal. The primary outcome was the proportion of patients with gastric volume > 1.5 mL kg^-1 calculated by two equations. Secondary outcomes included the antral cross-sectional area and gastric volume. Data are expressed as frequency (%, 95% confidence interval [CI]), mean ± standard deviation (95% CI of the mean), or median (quartiles) as appropriate.

RESULTS

Forty-one women were available for the final analysis. For the primary outcome, one participant (2.4%, 95% CI of 0.06 to 12.8%) had gastric volume > 1.5 mL kg^-1, and none had solids in the antrum. For the secondary outcomes, the mean (95% CI of the mean) of the antral cross-sectional area was 2.11 ± 0.72 (1.88 to 2.34) cm² and 4.08 ± 1.80 (3.51 to 4.65) cm² during the semi-recumbent and right-lateral position, respectively. The median (quartiles) gastric volume was 0.53 (0.32, 0.66) mL kg^-1 and 0.33 (0.13, 0.52) mL kg^-1 as estimated by Perlas et al. and Roukhomovsky et al. equations, respectively.

CONCLUSION

After 8-h fasting following a standardized meal, full-term pregnant non-laboring women are less likely to have a high residual gastric volume.

Anaesthesiologists' clinical judgment accuracy regarding preoperative full stomach: Diagnostic study in urgent surgical adult patients

BACKGROUND

In urgent situations, preoperative full stomach assessment mostly relies on clinical judgment. Our primary objective was to assess the diagnostic performance of clinical judgment for the preoperative assessment of full stomach in urgent patients compared to gastric point-of-care ultrasound (PoCUS). Our secondary objective was to identify risk factors associated with PoCUS full stomach in urgent patients.

METHODS

We led a prospective observational study at our Hospital, between January and July 2016. Adult patients admitted for urgent surgery were eligible. Patients with altered gastric sonoanatomy, interventions reducing stomach content, impossible lateral decubitus were excluded. Clinical judgment and risk factors of full stomach were collected before gastric PoCUS measurements. Ultrasonographic full stomach was defined by solid contents or liquid volume ≥ 1.5 ml kg^-1. Diagnostic performance was assessed through sensitivity, specificity, accuracy, positive and negative predictive value.

RESULTS

The prevalence of clinical and PoCUS full stomach in 196 included patients was 29% and 27%, respectively. Positive and negative predictive values were 42% (95% CI: 32.3-52.6%) and 79% (95% CI: 74.9-83.4%), respectively. Patients with PoCUS full stomach were clinically misdiagnosed in 55% of cases. PoCUS full stomach was associated with abdominal or gynaecological-obstetrical surgery (OR 3.6, 95% CI: 1.5-8.8, P < 0.01) but not with fasting durations. Positive solid intake after illness onset with respect to 6-h solid fasting rule was associated with PoCUS low-risk gastric content (OR 0.4, 95% CI: 0.2-0.9, P = 0.03).

CONCLUSIONS

Clinical judgment showed poor-to-moderate performance in urgent surgical patients for the diagnosis of full stomach. Gastric PoCUS should be used to assess risk of full stomach in this population.

Point-of-Care Ultrasound to Assess Gastric Content

Gastric ultrasound (US) is a growing modality within the point-of-care ultrasound (POCUS) field. It provides the ability to directly measure an individual patient's gastric content and has potential use as both a clinical and a research tool. Here, we review the historical development of current gastric US models and their clinical application within the field of general anesthesia, describe the US findings and technique for using POCUS to assess gastric content, and discuss the current and potential applications of gastric POCUS within the emergency department.

"Full Stomach" Despite the Wait: Point-of-care Gastric Ultrasound at the Time of Procedural Sedation in the Pediatric Emergency Department

OBJECTIVES

The objective was to use gastric point-of-care ultrasound (POCUS) to assess gastric contents and volume, summarize the prevalence of "full stomach," and explore the relationship between fasting time and gastric contents at the time of procedural sedation.

METHODS

This was a prospective study of patients aged 2 to 17 years fasting prior to procedural sedation. A single sonographer scanned each patient's gastric antrum in two positions: supine with the upper body elevated and right lateral decubitus (RLD). Gastric content (empty, liquid, or solid) was noted, and the gastric volume (mL/kg) was estimated from antral cross-sectional area (CSA). "Full stomach" was defined as any solid content or >1.2 mL/kg of liquid gastric content.

RESULTS

We enrolled 116 subjects, with a median fasting time of 5.8 hours. Of the 107 with evaluable images, 74 patients, 69% (95% confidence interval [CI] = 60%-77%), were categorized as having a full stomach. Each hour of fasting was associated with lower odds (odds ratio = 0.79, 95% CI = 0.65-0) of a full stomach. However, the knowledge of fasting time alone provides little ability to discriminate between risk groups (C-index = 0.66).

CONCLUSIONS

Gastric POCUS classified many patients as having a full stomach at the time of expected procedural sedation, despite prolonged fasting times. These findings may inform risk-benefit considerations when planning the timing and medication choice for procedural sedation.