Serum fatty acid concentrations in patients on postoperative parenteral nutrition with and without fat

Essential fatty acid status in patients on long-term home parenteral nutrition

BACKGROUND

Patients on total parenteral nutrition are known to be at risk of the development of essential fatty acid deficiency, presenting as a syndrome with scaly skin lesions and characterized by low plasma and erythrocyte linoleic acid concentrations. The essential fatty acid status of patients on long-term home parenteral nutrition who do have access to oral feeds has not been studied.

METHODS

With the use of an isocratic high-performance liquid chromatography method, fatty acids were measured in the erythrocytes and plasma of 25 nonfasting patients on long-term home parenteral nutrition and the findings compared with those of 46 hospital outpatients not on nutrition support and five laboratory staff.

RESULTS

Statistically significant differences in the two groups were limited to the erythrocytes. Linoleic acid was significantly lower (25.2 vs 40.7 mumol/10(6) red blood cells, p < .0001) and showed a significant correlation with triceps skinfold thickness (r = .52, p = .013). Palmitoleic and oleic acids were higher in patients than controls (10.8 vs 8.4 mumol/10(6) red blood cells, p = .009; 61.2 vs 51.7 mumol/10(6) red blood cells, p = .003).

CONCLUSIONS

Despite IV linoleic acid administration, patients on long-term home parenteral nutrition have low erythrocyte stores of this essential fatty acid. This appears to be related to their low body fat stores. We suggest that they may be using much of the infused linoleic acid as an energy source and therefore are at risk of subclinical essential fatty acid deficiency.

Evaluation of reference ranges for fatty acids in serum

Long chain fatty acid fractionation has become a valuable tool in the management of patients maintained on total parenteral nutrition. While many clinicians prefer to use absolute concentrations to monitor a patient's fatty acid status, reference ranges are not available. Previous reference range studies reported values in terms of percentages only and calculated ranges parametrically. However, due to the non-Gaussian distributions of some serum fatty acids, it is necessary to calculate reference ranges non-parametrically. Serum from blood donors (n = 130) were collected and analyzed for total fatty acids by gas-liquid chromatography. Results for each of the fatty acids were calculated both as a concentration and as a percentage of the total fatty acids measured.

Fat emulsion in surgical patients with liver disorders

Total parenteral nutrition (TPN) with fat emulsion was evaluated in 68 patients with liver disorders who were admitted to the First Department of Surgery, Osaka City University Medical School. All patients received transabdominal direct operation for esophageal varices. Immediately after their operations, 28 received TPN with carbohydrate and fat emulsion as an energy source (FAT group), and 40 received TPN with only carbohydrate as an energy source (non-FAT group). Liver function tests, blood glucose levels, intravenous fat tolerance tests, serum lipid levels, fatty acid composition of serum total lipids, and nitrogen balance of the two groups were compared during postoperative TPN. The administration of fat emulsion during postoperative TPN in patients with liver disorders did not worsen the results of liver function tests and the relatively low levels of blood glucose were retained, thereby correcting the abnormalities in the fatty acid composition of serum total lipids. Rates of clearance of fat emulsion during postoperative TPN were significantly higher than in the preoperative period, and changes in serum lipid levels revealed no tendency toward retention of fat emulsion administered intravenously. Nitrogen balance and change in body weight during postoperative TPN were similar in both groups. These results suggest that for patients with liver disorders, the administration of fat emulsion is useful during postoperative TPN.