Ultrasound-guided estimation of gastric residual volume using Perlas's formula: A validation study in patients

Background and aims: Bedside ultrasound (US) is used to evaluate gastric residual volume (GRV) and assess aspiration risk. We examined the accuracy of US-guided measurement of GRV using Perlas's formula, by two trained anaesthesiologists, in patients who had consumed different types and volumes of fluids.

Methods: Patients with no risk factors for delayed gastric emptying were included. Each assessor independently determined the baseline US-guided GRV. The patients were randomly allocated to receive no drink or 100 or 200 mL of water or milk. US-guided GRV was re-assessed within 5 min after the intervention. Investigators were blinded to the measurements performed by each other and to the randomisation arm. The primary outcome was the agreement between actual volumes consumed and estimated change in GRV.

Results: Agreement between actual volume consumed and estimated change in GRV was poor [Intra-class correlation coefficient (ICC) 0.46, 95% confidence interval (CI) 0.09 to 0.72; P = 0.09 for assessor 1 and ICC 0.37; 95% CI 0.02 to 0.66; P = 0.03 for assessor 2].

Conclusion: US-guided GRV measurements using Perlas's formula, performed by trained anaesthesiologists may not be a reliable measure of GRV.