The effects of sedation on gastric emptying and intra-gastric meal distribution in critical illness

Objective: To evaluate the effects of sedation with morphine and midazolam (M&M) versus propofol on gastric emptying in critically ill patients. Design: Descriptive study. Setting: Mixed medical and surgical intensive care unit. Patients: Thirty-six unselected, mechanically ventilated, critically ill patients. Interventions: Gastric scintigraphic data were analysed retrospectively according to whether patients were receiving M&M (n=20; 14M, 6F) or propofol (n=16; 7M, 9F). Measurements were performed over 4h after administration of 100ml of Ensure (R), labelled with 20MBq Tc-99m. Measurements and results: Gastric half-emptying time (t(1/2)) and total and regional (proximal and distal stomach) meal retention (%) were assessed. The median t(1/2) of patients receiving M&M (153 (IQR: 72-434) min) was significantly longer than that of patients receiving propofol (58 (34-166) min, p=0.02). Total gastric retention was greater in patients receiving M&M compared to those receiving propofol (p<0.01). Proximal (p=0.02) but not distal (p=0.80) gastric retention was greater in patients who received M&M. Patients who received M&M were more likely to have >= 5% meal retention at 240min than thosetreated with propofol (95% (19/20) vs. 56% (9/16); p=0.01). Changes in blood glucose concentrations during the study were similar in the two groups. Conclusions: In critical illness, patients receiving M&M for sedation are more likely to have slow gastric emptying, and proximal meal retention than those receiving propofol. The apparent beneficial effects of propofol-based sedation need confirmation by a prospective randomised controlled study.