Perlas' method may help anaesthesiologists estimate stomach residual volume using ultrasound

Aspiration is a problem for patients undergoing sedation or general anaesthesia because their lower oesophageal sphincter tone and protective airway reflexes are impaired. Previous studies have employed bedside ultrasonography (US) to determine peri-operative aspiration risk and advise anaesthesia treatment by evaluating stomach residual volume (GRV). However, since all measurements were taken by licenced sonographers in some of these investigations, the findings may not be repeatable.

Researchers have found in a new study that gastric residual volume (GRV) readings taken by radiologists and qualified anaesthesiologists had little concordance. The learning curve for anaesthesiologists to become competent in the gastric Ultrasound is little documented. Recently published study tried to see how accurate it was for trained anaesthesiologists to quantify gastric residual volume (GRV) using Perlas' formula in patients who received two different kinds and quantities of liquids.

The study comprised patients who had no risk indicators for delayed stomach emptying. The baseline US-guided GRV was calculated separately by each evaluator. The patients were given either no drink or 100 or 200 mL of water or milk at random. Within 5 minutes of the intervention, the US-guided GRV was re-assessed. The investigators were blinded to each other's measurements as well as the randomization arm. The agreement between actual amounts eaten and projected changes in GRV was the major result.

There was little agreement between the actual amount eaten and the projected change in GRV. [ICC 0.46, 95% confidence interval (CI) 0.09 to 0.72; P = 0.09 for assessor 1; ICC 0.37, 95% CI 0.02 to 0.66; P = 0.03 for assessor 2].

Prior to induction of anaesthesia, recognition of a high GRV allows the anaesthesiologist to take adequate steps to minimise the danger of aspiration. Methods based on US-guided ACSA measurement have been demonstrated to have high agreement with real GRV among the numerous methodologies outlined for GRV evaluation. The estimated change in GRV and the actual amount of fluid swallowed as judged by qualified anaesthesiologists, as well as between measurements taken by the assessors, were shown to have poor agreement in this investigation. The kind of fluid or the amount of fluid had no influence on the agreement between measurements.

Reference –

Khandekar, Sayali S.; Doctor, Jeson R.; Awaskar, Shilpa K.; Alex, Nidhin K.; Medha, Lipika R.; Ranganathan, Priya, Ultrasound-guided estimation of gastric residual volume using Perlas's formula: A validation study in patients, Indian Journal of Anaesthesia: April 2022 - Volume 66 - Issue 4 - p 255-259

doi: 10.4103/ija.ija_783_21