[Studies on the pharmacokinetics of carbohydrates as a basis for their use in parenteral feeding]

Comparison of glucose, LCT, and LCT plus MCT as calorie sources for parenterally nourished rats

Protein and fat metabolism were studied in fed and protein-depleted rats. The rats were given one of three isocaloric, isonitrogenous nutrient mixes parenterally. The nutritional regimens differed in the source of nonprotein calories: i) glucose, ii) an emulsion containing long-chain fatty acid triglyceride esters (LCT), and iii) an emulsion containing both LCTs and medium-chain fatty acid triglycerides (MCT). Nitrogen balance, protein synthesis and breakdown, fat deposition in the liver, and the periuterine fat pads were measured using [15N]glycine as the tracer for the protein metabolism and deuterium for the lipid studies. Results are as follows. i) Nitrogen retention and protein synthesis were greater in the fed rats treated with glucose than with LCT. ii) Nitrogen fluxes were lower with LCT than with glucose. iii) Extensive lipogenesis in the liver was only found with the glucose-treated rats. iv) None of the caloric regimens promoted lipogenesis in the periuterine fat pads. v) With the two lipid-containing regimens there was a relative depletion of the depot fat in the periuterine fat pads relative to their glucose-treated counterparts. v) Although the MCT-containing emulsion did not cause hepatomegaly, its apparent caloric effectiveness was lower than that of either glucose or LCT. vi) Chain elongation is not a major pathway for MCT metabolism in parenterally nourished rats.

Medium chain triglycerides in parenteral nutrition

Until recently, medium chain triglycerides (MCT) have not been used in parenteral nutrition (PN) although they are considered to be ideal sources of energy on account of their biochemical properties. The tolerance and utilization of 10% fat emulsion with 75% MCT was tested on 10 healthy males after an overnight fast. During an infusion period of 6 hr the total fat supply rate was 0.12 g/kg body weight/hr. A commercial 10% fat emulsion (Lipofundin-S-10) served as control. The fat emulsion containing MCT was tolerated without any side effects. Compared with the commercial fat emulsion, the increase of triglycerides was markedly lower and clearing of the serum was completed earlier. By gas chromatographic analysis of the serum fatty acid pattern, medium chain fatty acids rapidly achieved a steady state. During infusion of the fat emulsion containing MCT, the production of ketone bodies was considerably higher although acidosis was not induced. The results obtained indicate that the fat solutions containing MCT bypass gluconeogenesis and are utilized quickly without side effects.

[Differences in postoperative metabolism after pre- and postoperative beginning of total parenteral nutrition]

In this study we intended to investigate the influence of a 24-h-preoperative total parenteral nutrition (TPN) therapy--10 surgical patients, group 1--compared with the postoperative beginning of TPN--9 surgical patients, group 2--on the postoperative metabolism. Most probably due to preoperatively depleted glycogen storages in G 2, the urinary carbohydrate losses declined more rapidly postoperatively compared with G 1. 45 mMol/l of sodium did not cover the postoperative requirements of G 1. Although we administered 90 mMol/l of potassium/24 h, several patients of G 1 needed an additional substitution. No additional phosphate substitution was necessary in either group. Except for a slight positive balance on the operation day, fluid balance was well balanced on all the other days in G 1. From postoperative day 2 on, G 2 developed a deficit of free water. It could be demonstrated very clear in this study that the postoperative fluid and electrolyte requirements are strongly influenced even by a short-term preoperative fasting period.

Serum enzyme, bilirubin, uric acid, and cholesterol concentration changes during 7 days of total parenteral nutrition

Lactic dehydrogenase, glutamic oxalacetic transaminase, and alkaline phosphatase remained within normal limits during 7 days of total parenteral nutrition. Five patients showed a rise of total bilirubin up to 1.1 mg/100 ml on the fifth postoperative day, with no change in serum enzymes. Uric acid concentration fell continuously up to the third postoperative day (but within normal limits) and remained decreased until the end of infusion. During the preoperative nutrition period and after surgical intervention, cholesterol concentration showed a steep fall. Very low cholesterol concentrations can cause an alteration of erythrocyte membrane synthesis and should, therefore, be avoided.

[Differences in postoperative metabolism in reference to pre- and postoperative initiation of total parenteral nutrition. I]

We investigated the postoperative metabolism of patients undergoing gastric resection by beginning total parenteral nutrition pre- (group 1) and postoperatively (group 2). A third group remained fasting until 3 h after the surgical intervention. Because of the high serum glucose concentrations and the high glucose losses in the 24-h urine on the operation day in group 1 and 2 only the base glucose requirement (150--250 g/24/h) should be given in the early postoperative period. The low blood glucose concentration in group 3 and the elevated lactate values in group 2 underline this recommandation. Compared with group 2 and 3, group 1 had low free fatty acid concentrations of 250 micronVal/l because of the continuous pre-, intra-, and postoperative infusion. Compared with normal metabolic conditions, the free fatty acids do not seem to have the same insulin-antagonizing effect in the posttraumatic state. The fall of cholesterol after the surgical trauma reached its maximum after 12--15 h and amounted to about 40 mg% in the first two groups. Albumin and total protein fell continuously in group 1 and 2. The electrophoresis in group 1 showed a rise of alpha 1- and alpha 2-globulin to more than double the initial value, the beta-globulin showed only slight changes, the gamma-globulin dropped only slightly up to the 4th postoperative day. As a sign of an augmented catabolism the serum urea concentration rose during the postoperative state. Group 1 and 2 had a favourable nitrogen balance. The postoperative bilirubin rise could be held lower in group 1 compared to group 2.

[Fructose tolerance and utilization in healthy and chronically diseased liver]

In 12 patients with liver cirrhosis (LC) and 11 normal subjects (N) equimolar (0.75 g/kg/h for 4 hrs.) 14C-(1)-glucose and 14C-(1)-fructose infusions were administered. When given fructose, N and LC showed only a small increase of serum-glucose and -fructose concentrations in steady state. In N and LC the total fructose clearance was significantly higher than the total glucose clearance. No differences were found between N and LC. The metabolic clearance was equal in both groups when given fructose, whereas during glucose infusion lower in LC than in N. 30% of the infused 14C-fructose were recovered in 14C-glucose. The renal loss in both groups was higher for glucose than for fructose. A more extensive renal 14C-excretion during infusion of 14C-fructose was due to a higher 14C-lactate excretion.

[Changes in several important metabolic parameters and insulin level during a 7-day total parenteral nutrition under pre- and postoperative conditions]

After the 24 hours preoperative infusion period 0.37% glucose, 0.05% fructose and 1.28% xylitol of the infused amount were excreted in the urine. Postoperatively fructose was the best metabolized energy donator before xylitol and glucose. As a sign of an undisturbed hepatic synthesis of lipoproteins the triglycerides rose up to the 5th postoperative day. During the parenteral nutrition and the additional surgical intervention the cholesterol fell from 192.3 to 128.5 mg/100 ml on the first postoperative day. The infusion solutions caused a rise of the insulin concentration from 23.2 to 46.3 U/l on the operation day. There is a positive nitrogen balance of 3.5 g/24 h on the operation day. The slight negative balance of - 1.15 g/24 h on the first postoperative day is reduced to - 0.61 g/24 h on the postoperative day. The changes of the enzymes LDH, GOT and AP were at normal range. The postoperative changes were due to the surgical intervention. Without a simultaneous change of enzymes, 5 patients had a rise of bilirubin up to 1.1 mg/100 ml. To avoid a too great loose of phosphate during a long-term parenteral nutrition period, it is important to put up a balance.

[Effect of maltose, following long-term intravenous infusion, on the metabolism]

6 healthy subjects received a 20% electrolyte containing maltose solution over a period of 6 hours. The concentration of maltose rose up to 109 (76-215 mg/100 ml). During the infusion period 3,7 (1,9-7,7) g maltose were excreted. The concentration of glucose and insulin was not altered, although the renal glucose loss was 20,2 (7,5-38,7) g. In the same period 49,8 +/- 13,2 mval potassium and 135,4 +/- 35 mval sodium were eliminated. Maltose induced an osmotic diuresis which was not caused by hyperglycemia. Such a type of osmotic substance has not been described before.