Standard fasting does not empty the stomach of an adolescent on a GLP-1 agonist

Design

Prospective cohort study with qualitative and quantitative gastric ultrasound, single institution, 2023-2024

Population

67 adolescents aged 10 to 18 (20 on GLP-1 receptor agonists, 27 otherwise at risk, 20 controls), median age 14.8 years

Primary outcome

Residual gastric contents - solids present or gastric fluid volume 1.5 ml per kg or more

Effect

Solids present in 16/20 (80 per cent) on GLP-1 agonists, 17/27 (63 per cent) at-risk and 1/20 (5 per cent) controls, after a median 13-hour solid fast (adjusted P < 0.02)

Glucagon-like peptide-1 receptor agonists are licensed from age 10 for type 2 diabetes and from 12 for obesity, and adolescents on them are now appearing on ordinary operating lists. This prospective cohort scanned them. Sixty-seven patients aged 10 to 18 at one institution were grouped as taking a GLP-1 agonist (20), otherwise at risk of delayed gastric emptying (27), or healthy controls (20). Everyone fasted to standard guidance, and in practice the median fast was 13 hours for solids and 12 for clear fluids - considerably longer than the eight and one hours required.

Sixteen of the 20 patients on a GLP-1 agonist, 80 per cent, had solid gastric contents visible on ultrasound. So did 17 of 27 in the at-risk group, 63 per cent. Among healthy controls it was 1 of 20, 5 per cent. The difference held after propensity adjustment for age, body mass index, sex, race and fasting time (P < 0.02).

The change to practice is direct: fasting duration is not a reliable proxy for an empty stomach in this group, and a 13-hour fast did not produce one. Scan the stomach before induction where gastric ultrasound is available, and where it is not, treat the adolescent on a GLP-1 agonist as having a full stomach and plan the airway accordingly. Note also the at-risk comparator, at 63 per cent - this is not only a GLP-1 problem, and the adolescent with reflux, diabetes or another emptying risk deserves the same caution. Sixty-seven patients at one centre is a small study, but the direction is unambiguous and the cost of assuming otherwise is aspiration.

• Ask every adolescent preoperatively about GLP-1 receptor agonists by drug name, not by asking about diabetes.
• Perform gastric ultrasound before induction where it is available, whatever the fasting time.
• Where it is not available, plan the airway as for a full stomach.
• Do not extend the fast as the solution; a 13-hour median fast did not empty these stomachs.
• Apply the same caution to adolescents otherwise at risk of delayed emptying, where 63 per cent had solids.

The statistics, in plain English

With 20 patients in the exposed group, 80 per cent means 16 people, so the proportion is imprecise even though the contrast with 5 per cent in controls is stark. Propensity adjustment for age, body mass index, sex, race and fasting time addresses the obvious confounders but cannot handle unmeasured ones such as what was actually eaten. The high rate in the at-risk comparator group is important context: it means the finding is about delayed emptying generally, with GLP-1 agonists as one strong cause rather than a unique one.

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