Background: Gastric emptying is frequently delayed in critical illness which compromises the success of nasogastric nutrition. The underlying motor dysfunctions are poorly defined. Aims: To characterise antro-pyloro-duodenal motility during fasting, and in response to gastric and duodenal nutrient, as well as to ev aluate the relationship between gastric emptying andmotility, in the critically ill. Subjects: Fifteen mechanically ventilated patients from a mixed intensive c are unit; 10 healthy volunteers. Methods: Antro-pyloro-duodenal pressures were recorded during fasting, after intragastric administration (100 ml; 100 kcal), and during small intestinal infusion of liquid nutrient (6 hours; l kcal/min). G astric emptying was measured using a 13C octanoate breath test. Results: In heal thy subjects, neither gastric nor small intestinal nutrient affected antro-pylo ro-duodenal pressures. In patients, duodenal nutrient infusion reduced antral a ctivity compared with both fasting and healthy subjects (0.03 (0-2.47) waves/mi n v 0.14 (0-2.2) fasting (p = 0.016); and v 0.33 (0-2.57)/min in healthy subje cts (p = 0.005)). Basal pyloric pressure and the frequency of phasic pyloric pre ssure waves were increased in patients during duodenal nutrient infusion (3.12 ( 1.06) mm Hg; 0.98 (0.13)/min) compared with healthy subjects (-0.44 (1.25) mm H g; p < 0.02 after 120 minutes; 0.29 (0.15)/min; p = 0.0002) and with fasting (- 0.06 (1.05) mm Hg; p < 0.03 after 160 minutes; 0.49 (0.13)/min; (p = 0.0001). Ga stric emptying was delayed in patients (gastric emptying coefficient 2.99 (0.2) v 3.47 (0.1); p = 0.015) and inversely related to the number of pyloric pressure waves (r = -0.563, p = 0.029). Conclusions: Stimulation of pyloric and suppres sion of antral pressures by duodenal nutrient are enhanced in the critically ill and related to decreased gastric emptying.
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