Evaluation of USG guided Pre extubation GRV (Gastric Residual Volume) measurements in relation to NBM (Nil by Mouth) duration in critically ill adult patients on mechanical ventilation

Majority of critically ill patients are intubated for mechanical ventilation in the icu and are enterally fed according to recent guidelines. However, no evidence-based recommendation is available regarding fasting times prior to extubation.

When an extubation is planned, patients do not always present with normal neurological status yet, and are at risk of vomiting and aspiration. Extubation may also fail and require re-intubation with similar risks. Thus, pre-operative fasting guidelines are often extrapolated to the critical care setting, aiming for an empty stomach at extubation, with perceived decreased risks of aspiration. However, the gastric and gut motility pathophysiology is significantly different in critically ill patients (frequent gastroparesis, liquid continuous feeding, etc.) compared to planned surgery patients. The extrapolation of practice validated in the later population may be inadequate. The stomach may be empty earlier than expected, leading to unnecessary prolonged fasting times. Prolonged fasting pre extubation can  predispose patient to hypoglycemic episodes, and also lead to deficit in the caloric intake over time.

Gastric ultrasound for GRV monitoring may help assessing gastric content status and the risk of aspiration prior to extubation.

Monitoring GRV involves obtaining frequent GRV measurements and employing appropriate interventions in patients with large GRVs. Gastric residual volume is an essential component of monitoring Enteral feeding to assess tolerance of feed.