Composition of fat in enteral diets can influence outcome in experimental peritonitis

An animal model of protracted acute peritonitis was used to study the effects on survival of different amounts and types of dietary fat. Guinea pigs (n = 132) were provided with gastrostomies and allowed to recover. Intraperitoneal osmotic pumps were then placed, allowing for effusion of viable bacteria during the next week. Three days after pump implantation, the animals were randomized to receive one of nine diets, differing only in fat content (3.5%, 14%, or 56% of total calories) and fat composition (100% Microlipid [primarily safflower oil, rich in linoleic acid], 100% MaxEPA [fish oil containing 35% omega-three fatty acids], or a 50:50 mixture of both oils). At the end of 2 weeks, survival rates were compared. Among all types of fat used, the level of fat did not affect outcome, with survival rates of 13% (6 of 45) at the low level of fat used, 30% (13 of 44) at the medium level, and 26% (11 of 43) at the high level (P greater than 0.10). However fat composition significantly influenced survival across all levels of fat, with a 39% (17 of 44) survival rate in the groups given equal amounts of Microlipid and MaxEPA, compared either to 21% (9 of 44) for the 100% Microlipid groups, or to 9% (4 of 44) for the 100% MaxEPA groups (p less than 0.05). A second experiment was performed with 58 animals fed five different mixtures of fats, all at 14% of total calories. Diets were made with fat ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 Microlipid to MaxEPA. The survival rate in the 50:50 group was 83% (10 of 12), which is significantly higher than the survival rates with any of the others (p less than 0.05). It is concluded that the amount of fat in the diet does not strongly influence outcome in this model. However an equal mixture of safflower and fish oils significantly improves survival rates compared to diets made with single-oil preparations.