Utilization of fat emulsion during total parenteral nutrition in children

Aggressive early total parental nutrition in low-birth-weight infants

OBJECTIVE

This study aimed to compare nitrogen balance and biochemical tolerance of early aggressive versus late total parenteral nutrition in very-low-birth-weight (VLBW) infants over the first week of life.

STUDY DESIGN

In all, 32 ventilator-dependent preterm infants were prospectively randomized into two groups. The Early Total Parenteral Nutrition (ETPN) group received 3.5 g/kilo-day amino acids (AA), and 3 g/kilo-day of 20% Intralipid (IL), starting within 1 hour after birth. The Late Total Parenteral Nutrition group (LTPN), started on a solution containing glucose during the first 48 hours of life, followed by 2 g/kilo-day of AA and 0.5 g/kilo-day of IL. For the LTPN group AA and IL were each increased by 0.5 g/kilo-day to a maximum of 3.5 and 3 g/kilo-day, respectively.

RESULTS

Nitrogen retention was significantly greater in all infants in the ETPN group throughout the 7-day study period. All infants in the LTPN group were in negative nitrogen balance during the first 48 hours of life, while those in the ETPN group were in positive nitrogen balance throughout. The mean (+/-SD) nitrogen retention in the ETPN was 384.5 mg/kilo-day (+/-20.2), compared to 203.4 mg/kilo-day (+/-20.9) in the LTPN group (p <0.001). In each of the first 5 days of life, energy intake was significantly greater in the ETPN group compared to the LTPN group (p <0.001). Mean fluid intake during the study period was similar between, the ETPN and the LTPN groups (162 and 165 cm3/kilo-day, respectively). The mean weight gain was similar in the ETPN and LTPN groups. Plasma levels of cholesterol, triglycerides, bicarbonate, blood urea nitrogen, creatinine, and pH were similar in both groups during the study period. Mean (+/-SD) serum glucose in the LTPN group was higher, but remained in normal range (101.1+/-5.2 and 80.8+/-5.4 mg/kilo-day, respectively). The mean peak serum bilirubin was significantly higher in the ETPN group, compared to The LTPN group (7.7 and 6.2 mg/dl).

CONCLUSION

This study shows that aggressive intake of AA and IL can be tolerated immediately after birth by VLBW infants. Also, ETPN significantly increased positive nitrogen balance and caloric intake, without increasing the risk of metabolic acidosis, hypercholesterolemia, or hypertriglyceridemia.

Effect of intravenous lipid emulsions on hepatic cholesterol metabolism

BACKGROUND

Total parenteral nutrition offers the chance of survival to children who have had extensive gut resections or gut failure. However, in infants it is often associated with serious complications including cholestatic liver disease. The causes of these complications remain unclear, although it has been suggested that the lipid emulsions used in total parenteral nutrition may be responsible.

METHODS

An in vitro system was developed to study the effect of lipid emulsions on hepatic cholesterol metabolism using cultured hepatocytes.

RESULTS

Incubations of Hep G2 cells with medium containing Intralipid (Pharmacia and Upjohn, Milton Keynes, UK) demonstrated that the fat emulsion mediated a powerful dose-dependent but reversible inhibition of cholesterol uptake. In addition Intralipid was shown to stimulate the efflux of cholesterol from Hep G2 cells. The component or components of the Intralipid responsible for these effects and the mechanism by which they act remain to be established.

CONCLUSIONS

Intravenous lipid emulsions may interfere with hepatic cholesterol metabolism in vivo. This may have implications for the development of total parenteral nutrition-associated cholestasis in neonates.

Lipid metabolism of the micropremie

Intravenous lipid emulsions often provide substance for the very low-birth weight or extremely low-birth weight infant that need total parenteral nutrition. The process used in this type of treatment as well as the effects of such treatment are discussed at length in this article. Some of the main compounds of representative lipid emulsions are listed and evaluated and the benefits and consequences of their use are presented.

Low birthweight infants and total parenteral nutrition immediately after birth. II. Randomised study of biochemical tolerance of intravenous glucose, amino acids, and lipid

This randomised study aimed to compare the biochemical tolerance of three parenteral regimens administered during the first 48 hours of life. Twenty nine infants were randomised to either: (a) glucose 10%; (b) glucose 10%/amino acids; (c) glucose 10%/amino acids/lipid. Blood samples for plasma amino acid profiles, cholesterol, and triglyceride concentrations were taken on arrival in the neonatal unit and again between 36 and 48 hours of life. Arterial or capillary blood gas analysis and blood glucose estimates were performed routinely during the first 48 hours of life. There was a sharp decline in plasma amino acid concentrations in the group following (a) compared with the two groups following (b) and (c) regimens. In all groups plasma triglyceride and cholesterol were not significantly different before and after 48 hours of lipid infusion. Peak mean (SE) bilirubin concentrations (203 (12) v 181 (19) v 220 (20) mumol/l) and the need for phototherapy (nine v eight v five infants) were similar for each of the groups. Hypoglycaemia occurred most frequently during the (b) regimen and least commonly in the (c) group. There are potential health gains from giving parenteral nutrition to low birthweight infants immediately after birth, and this study indicates that restriction of nutritional intake immediately after birth in preterm infants may cause significant metabolic disturbance. This can be prevented by starting a regimen of intravenous amino acids and lipid immediately after birth.

Three-in-one parenteral nutrition: a safe and economical method of nutritional support for infants

The medical records of 20 infants under 1 year of age who received parenteral nutrition (PN) for a minimum of 1 week were reviewed. Patients were divided into two groups based on the method of PN administration. One group received PN by the traditional two-plus-one method where lipid emulsion is given separately from the dextrose-amino acid mixture. The second group received PN by the three-in-one method where lipid emulsion is admixed with the dextrose and amino acids. There were no statistically significant differences between the two groups in the amount of calories, lipid, dextrose, protein, calcium, and phosphorus received per kg of body weight. Average daily weight gain was not statistically different, and no obvious trends were noted in serum biochemical parameters between the two groups. Average total PN days for the groups (13 +/- 7 days for the two-plus-one group vs 39 +/- 35 days for the three-in-one group) were significantly different (p less than 0.05). A cost comparison of the two methods of PN administration indicated that the two-plus-one method costs our hospital $11.78 more per day than the three-in-one solution. We conclude that the three-in-one method of PN administration is safe, efficacious, and cost effective for infants under 1 year of age.

Serum fatty acid profiles after intravenous medium chain triglyceride administration

The serum fatty acid profiles of patients receiving either intravenous medium or long chain triglycerides were studied. Seventeen hospitalized patients, dependent on total parenteral nutrition, were randomly enrolled into a prospective study. The total parenteral nutrition (TPN) delivered amino acids and glucose and either a 75% medium chain triglyceride and 25% long chain triglyceride (MCT group) physical mixture or all long chain triglyceride (LCT group), as the respective fat sources. The amino acids and glucose were given continuously, and the lipid was given for 10 hours each day over five days. Fatty acid profiles on serum triglycerides and free fatty acids were done in the morning before any lipid was given and also later in the afternoon, near the end of the lipid administration, on days 1, 3 and 5. Medium chain fatty acids rose quickly in the triglyceride fraction in patients given MCT. Rapid MCT hydrolysis occurred as evidenced by the appearance of medium chain fatty acids in the free fatty acid fraction in the afternoon sampling. Clearance of the hydrolyzed medium chain free fatty acids (MCFFA) occurred so that little, if any, were present in the morning sampling one day later. Long chain fatty acids, as either triglycerides or free fatty acids, showed expected increases during the daily infusion, but not of such relative magnitude as the medium chain fatty acids. Medium chain fatty acid incorporation into the phospholipid or cholesterol ester fractions by the end of the five-day feeding period was present but minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of intravenous fat emulsion in the surgical newborn

The metabolism of an intravenous (IV) fat emulsion was investigated by the combination of chemical balance and computerized indirect calorimetry techniques in 21 newborns (birth weight, 3.0 +/- 0.1 kg; mean +/- SE). All babies were appropriate for gestational age and received total parenteral nutrition after a major surgical procedure. The study was divided into two consecutive periods. Phase 1 consisted of infusion of 10% glucose and 2% amino acid solutions for 24 hours, and phase 2 involved the "Intralipid utilization test" (isocaloric and isovolemic infusion of Intralipid 10% for four hours). The caloric intake was 67.1 +/- 1.9 kcal/kg/d during both phases of the study. The resting energy expenditure was 44.8 +/- 1.6 and 46.5 +/- 1.8 kcal/kg/d during phases 1 and 2 respectively. During glucose/amino acid infusion, 12 patients oxidized endogenous fat, and de novo lipogenesis from glucose was observed in nine. During the Intralipid infusion, there was a significant and progressive decrease of carbon dioxide production, respiratory quotient, and carbohydrate utilization (oxidation plus conversion to fat). Net lipogenesis ended and fat utilization significantly increased. By the second hour of Intralipid infusion, 58% of energy expenditure was derived from fat oxidation. The drop in carbon dioxide production correlated positively with the decrease in carbohydrate utilization (r = .07; P less than .001). During the third and fourth hours of phase 2, the percentage of fat utilized was negatively correlated with the amount of fat given (r = -.07; P less than .01). The surgical neonate showed rapid metabolic adaptation to Intralipid infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary nodules secondary to total parenteral alimentation

A seven-year-old male, who had a retro-peritoneal alveolar rhabdomyosarcoma and was on total parenteral alimentation (TPN) developed multiple pulmonary nodules, indistinguishable from metastases. These proved to be multiple lipid emboli on open biopsy.

Metabolic utilization of linoleic acid from fat emulsion in infants during total parenteral nutrition

The metabolic utilization of linoleic acid (C18:2w6) from intravenous (iv) soybean oil emulsion via its conversion to higher homologues and prostaglandin biosynthesis was studied in 21 infants. The infants were of normal birth weight, in good clinical and metabolic condition, and aged from 1-4 months. They all received total parenteral nutrition after birth for more than 1 month; the only lipid was provided by iv Intralipid 20%, at levels approximating 350 mg/kg/24 h of linoleic acid (2.5% of the infants' total daily energy intake). Study of the fatty acids of plasma and erythrocyte phospholipids in these infants, compared to healthy controls of the same age (N = 26), showed that 350 mg/kg/24 hr of C18:2w6 supply resulted in normalization of erythrocyte phospholipid fatty acid distribution. This was particularly true of the higher homologues of C18:2w6 (C18:3w6, C20:3w6, and C20:4w6). This suggested that delta 6 and delta 5 desaturation activities are normal in these conditions with this C18:2w6 supply. These results were confirmed by the study of 24-hr urinary excretion of prostaglandins PGE1 and PGE2. With 350 mg/kg/24 hr of C18:2w6 supply their urinary levels were not significantly different from those observed in normal children of the same age receiving an equivalent oral C18:2w6 intake.

Plasma phospholipid fatty acids and urinary excretion of prostaglandins PGE1 and PGE2 in infants during total parenteral nutrition, with continuous or sequential administration of fat emulsion

During total parenteral nutrition, using an identical supply of fat emulsion (350 mg/kg/24 hr) to correct essential fatty acid deficiency in children, the efficacy of two methods of administration was studied: continuous over 24 hr, or discontinuous 3 hr/day. At the beginning of the study, all the infants (1-4 months old) had proven essential fatty acid deficiency. After at least 1 month of one of the two nutritional protocols (continuous or discontinuous), plasma phospholipid fatty acid composition and PGE1 and PGE2 urinary excretion were measured. The results obtained indicate better utilization of the fat emulsion when it is administered almost every day, in continuous infusion over 24 hr (1 g/kg/24 hr of Intralipid 20%).

Total parenteral nutrition in children

This article first focuses on the indications for total parenteral nutrition and the effect of its use on the outcome of various nutrient-depleting diseases in infants and children. This is followed by a discussion of some of the newer nutrient additions to total parenteral nutrition regimens, such as biotin, carnitine, zinc, copper, iron, and others.

The effect of 15-hour fat infusions of varying dosage on bilirubin binding to albumin

Intravenous fat emulsions (1, 2, and 3 g/kg) were administered over 15 hr to 20 appropriate for gestational age premature infants with physiologic hyperbilirubinemia to determine the effect of fat infusions on the serum free fatty acid:albumin molar ratio (F/A) and on unbound bilirubin. Significant increases (p less than 0.05) in F/A occurred with each increase in lipid dose in infants less than 30 wk gestation, but not in infants greater than or equal to 30 wk gestation. There was a direct linear correlation (r = 0.65, p less than 0.001) between F/A ratio and unbound bilirubin (estimated fluorometrically by the ratio of albumin-bound bilirubin/reserve bilirubin binding capacity, B/R). The largest increases in unbound bilirubin (albumin-bound bilirubin/reserve bilirubin binding capacity) were seen in infants with F/A greater than 4.0. The gestational age of infants with F/A greater than 4.0 was significantly less (p less than 0.01) than infants with F/A less than 4.0 (28.7 +/- 0.47 vs. 31.1 +/- 0.40 wk, mean +/- SEM). In 10/58 infusions there was a fall in unbound bilirubin, unrelated to birthweight, gestational age, postnatal age, however, during these infusions the end-infusion F/A was greater than or equal to 3.0. We conclude that 1 g/kg of lipid emulsion infused over a 15-hr period has minimal risk of decreasing bilirubin binding in premature infants less than 30 wk gestation. As doses of 2 or 3 g/kg are used, these infants may be at risk of decreased bilirubin binding, due to elevations in the F/A ratio. Monitoring of the F/A ratio may identify infants at risk for decreased bilirubin binding during lipid infusion and provide guidelines for determining the appropriate lipid dose.

Effect of amino acid composition of parenteral solutions on nitrogen retention and metabolic response in very-low-birth weight infants

To evaluate the influence of amino acid preparations on the metabolic response of parenterally fed immature newborn infants, nitrogen retention and plasma amino acid concentrations were compared in very-low-birth-weight infants given two parenteral regimens differing only by the composition of the infused amino acids (Travasol 10% blend B and Vamin 7%). The intakes of fluid, nitrogen, and calories were comparable. The nitrogen retention was 72% +/- 7% with Vamin and 65% +/- 6% with Travasol. The differences in plasma amino acid concentrations were consistent with the composition of the amino acid solutions. During the infusion of Vamin the increased intake of aromatic amino acids resulted in high plasma levels of tyrosine (256 +/- 233 mumol/L, range 67 to 894 mumol/L). The infusion of Travasol resulted in high plasma levels of methionine (114 +/- 39 mumol/L, range 53 to 260 mumol/L) and an elevated load of glycine, which was accompanied by an abnormally high urinary loss of this amino acid. Despite these metabolic imbalances, the growth rate over the whole study was adequate. These results emphasize the importance of the composition of amino acid solutions on the metabolic response of the very immature preterm infant.

Tolerance of intravenously administered lipid in newborns

The tolerance for intravenously administered Intralipid in 262 premature and sick newborns was studied. The serum concentrations of triglycerides and of free fatty acids were determined during total parenteral nutrition including Intralipid in a maximum daily dose of 2 g/kg. A serum concentration of 1.5 mmol/l or higher was found in 270 out of 985 triglyceride determinations (27.4%). In the 262 infants serum triglyceride concentrations were found elevated once or more in 117 cases (44.7%). Serum free fatty acids concentrations were normal. A highly significant inverse correlation (p less than 0.001) between birth weight and triglyceride level was found. Elevated serum triglyceride concentrations were observed especially in preterm small-for-gestational-age infants.

Human plasma lipoproteins and total parenteral nutrition with intravenous fat emulsion

Lipoprotein concentration and composition before and after Intralipid infusion were investigated in seven adult surgical patients receiving continuous total parenteral nutrition. Plasma samples were obtained prior to parenteral alimentation, after 7 days of glucose/amino acid solution without Intralipid, and again following 5 days of daily Intralipid. Cholesterol, triglyceride, protein, and phospholipid concentrations were determined on very low-, low-, and high-density lipoprotein from each specimen. After Intralipid very low-density lipoprotein concentration fell to 29% (p less than 0.015) of pre-Intralipid levels. There was no substantial increase in low-density lipoprotein phospholipid post-Intralipid to suggest the presence of lipoprotein-X. Plasma total triglyceride levels declined by 33% after Intralipid (p less than 0.01) and plasma total cholesterol levels rose by 40% (p less than 0.02). In our patients, in whom metabolic mechanisms were not saturated, it would appear that Intralipid was metabolized by activated lipoprotein lipase pathways, without the appearance of hyperlipidemia or abnormal lipoproteins.

Triglyceride and fatty acid clearance in neonates following safflower oil emulsion infusion

Fifteen neonates requiring parenteral nutrition with lipid emulsion were given a 1.0 g/kg dose of safflower oil emulsion to evaluate triglyceride (TGY) and free fatty acid clearance. The dose was infused intravenously over 4 hr, and serum was obtained at 0, 2, 4, 6, and 8 hr. Peak serum TGY averaged 592 mg/dl for the appropriate for gestational age newborns and 606 mg/dl for the small for gestational age babies. The small for gestational age neonates had significantly higher serum free fatty acids at 2 and 4 hr into the infusion than did the appropriate for gestational age infants. Peak serum free fatty acids ranged from 0.915 to 3.233 mM in the appropriate for gestational age babies and 2.518 to 3.586 mM in the small for gestational age infants. In contrast to previous work with soybean oil emulsion, we did not demonstrate differences in TGY clearance between small for gestational age and appropriate for gestational age neonates and did demonstrate a markedly elevated serum TGY in these critically ill newborns. Serum TGY and free fatty acids must be monitored in newborns administered intravenous fat emulsion to avoid the complications of iatrogenic hyperlipemia.

Nonlinear kinetic analysis of the elimination of lipid emulsion administered intravenously to dogs

A model based on a Michaelis-Menten nonlinear kinetic approach was used to analyze the kinetics of elimination of an intravenously infused lipid emulsion in the dog. The emulsion was administered at doses of 0.3, 3, or 6 g of lipid/kg of body weight. The model was applicable to all data regardless of the kinetic order of the elimination process operating. This can be either zero (linear), mixed, or first order (exponential). Furthermore, it was also found that parameters derived with the model can be used to predict the kinetics of elimination at different dosages. However, it was also shown that elimination parameters for a single bolus dose of lipid emulsion cannot be used to predict the manner in which a continuously infused dose will be eliminated.

Limited value of nephelometry in monitoring the administration of intravenous fat in neonates

To evaluate the usefulness of nephelometry in predicting hyperlipidemia in neonates receiving intravenous fat (IVF), 23 infants in our neonatal intensive care nursery had simultaneous measurements of the serum IVF level (as determined by nephelometry), triglyceride, cholesterol, and free fatty acid/albumin molar ratio. There was a positive correlation between the serum IVF level and triglycerides, but the IVF level did not reliably predict elevated triglycerides, cholesterol, or free fatty acid-albumin molar ratio. Thus, neonates receiving IVF emulsions cannot be monitored by nephelometry alone. Adequate monitoring requires measurement of specific lipid fractions.

Effect of heparin on lipoprotein profile during parenteral fat infusions

Long-term administration of Intralipid to infants raises the potential risk of cumulative hyperlipemia. The elimination of lipoproteins from the blood during 3 hours of Intralipid infusion (0.33 grams per kilogram per hour) was investigated in five term infants during two infusion periods without and with heparin. A single intravenous injection of heparin (100 micron per kilogram) preceded the period of Intralipid infusion. During the nonheparin periods levels of triglycerides (L-particles) rose progressively to 1320 +/- 133 milligrams per 100 milliliters plasma, whereas during the heparin periods levels rose more moderately and peaked at 636 +/- 197 milligrams per 100 milliliter plasma (p less than 0.001-0.05). The study suggests that the heparin effect is still apparent for a period of 6 hours and repeated bolus injections may keep triglyceride levels at approximately normal concentrations during constant Intralipid infusion (0.166 grams per kilograms per hour).

Carnitine blood concentrations and fat utilization in parenterally alimented premature newborn infants

To investigate the relationships among carnitine intake, carnitine blood concentrations, and the ability to utilize exogenous fat, total carnitine, free carnitine, acylcarnitine, beta-hydroxybutyrate, free fatty acid and triglyceride plasma concentrations were measured in 26 parenterally alimented appropriate-for-gestational-age premature infants before and at the end of a four-hour infusion of Intralipid, 1 gm/kg body weight. There was an increase in plasma levels of AC, BOB, FFA, and TG, but a decrease of FC, TC was unaffected by the infusion, but strongly correlated with calculated carnitine intake. At the end of the fat infusion, AC and BOB were positively correlated, and FFA negatively correlated with TC. The results demonstrate the proportion of AC to FC to be an additional indicator of fatty acid utilization and suggest that decreased carnitine intake in premature infants may impair fatty acid oxidation and ketogenesis.

Effect of parenteral hyperalimentation on serum lipoproteins and on lipoprotein lipase activity of adipose tissue and skeletal muscle

This study reports on the effects of parenteral nutrition with glucose along or in combination with Intralipid on heparin-releasable lipoprotein lipase (LPL) activity of adipose tissue and skeletal muscle and on serum lipoproteins. Thirteen patients with postoperative hypercatabolism and nine patients with caloric malnutrition were studied. The average adipose tissue LPL activity increased 5-fold during 4-day glucose infusion (P less than 0.001) and 7.4-fold during Intralipid plus glucose infusion (P less than 0.001). In contrast, no change occurred in the LPL activity of skeletal muscle. Glucose infusion caused a significant increase in VLDL and LDL triglyceride concentrations and the Intralipid plus glucose infusion was followed by a rise in LDL and HDL triglyceride concentrations. HDL cholesterol decreased by 26% (P less than 0.01) during glucose and by 19% (P less than 0.05) during Intralipid plus glucose. Apoprotein A I was very low already at the start of parenteral alimentation and it did not change during either nutrition. The HDL cholesterol and apoprotein A I and A II levels were each positively correlated with adipose tissue LPL activity before parenteral nutrition but not after it.

Pulmonary fat accumulation after intralipid infusion in the preterm infant

Eight preterm infants who died after 'Intralipid' infusion had fat accumulation in the lungs. The rate of infusion in six of the infants was below the recommended maximum for preterm infants and in no case was the plasma lipaemic on regular visual inspection. Histological examination revealed varying degrees of lung involvement. The commonest finding was distension of empty pulmonary capillaries, but specific staining techniques for fat showed that the capillaries were engorged with large lipid globules. Removal of accumulated fat by histiocytes was seen in infants dying some time after cessation of intralipid infusion. Analysis of homogenised lung showed that those who died after intralipid infusion had a significantly greater (p < 0.001) concentration of lioleic acid, a marker for intralipid, than infants who died without receiving parenteral fat solution. Fat accumulation after intralipid infusion may be common but unrecognised and may seriously exacerbate ventilation/perfusion inequalities.

Serum intralipid levels in neonates during parenteral nutrition: the relation to gestational age

To detect hyperlipidemia, serum Intralipid levels have been monitored by nephelometry (light scanning index) in children on total parenteral nutrition with glucose, amino acids, and Intralipid during the past 2 yr. Sufficient data were available in 93 neonates to analyze the effect of an Intralipid dose on serum levels in infants of different gestational ages. Guided by monitoring, Intralipid was given by constant infusion at a dose varying between 0.5 to 6.0 g/kg/day. Median post natal age at the start of therapy was 7 days. Gestational age varied from 27 to 32 wk in 36 infants (Group I), 33 to 36 wk in 18 (Group II), and was more than 37 wk in 39 (Group III). Of Group I infants, 28% developed hyperlipidemia (Intralipid level greater than 100 mg/100 ml) as compared to an incidence of 7% in Groups II and III. Peak Intralipid levels were highest in Group I and regression analysis also indicated that Intralipid was least well tolerated by this group. The dose response during the first 48 hr of Intralipid therapy was not significantly different from dose response later. Similarly, diagnosis did not seem to affect the dose-response. Dose recommendations were based on analysis of dose response lines. Even using these guidelines monitoring of serum Intralipid is advisable to avoid hyperlipidemia during Intralipid therapy. It is recommended that measurements of serum Intralipid be made several times per week in very low birth weight infants (Group I), and weekly in more mature neonates after a safe maximum Intralipid dose is established.

An evaluation of methods to monitor infants receiving intravenous lipids

Nephelometric measurement of light-scattering index and visual estimates of turbidity have been advocated to monitor serum Intralipid levels. This study describes a simple modified fluorometric method for accurately measuring lipid particles in serum and examines the reliability of such estimates compared with other chemical measurements. Ten percent IL was diluted with either saline or serum to various concentrations (0 to 250 mg/dl). The LSI showed an excellent correlation with known IL standard solutions in saline or serum (R = 0.99) and with triglyceride concentrations (R= 0.98). One hundred nine blood samples were obtained from 35 patients (28 neonates) receiving IL. An elevated TG, free fatty acid, or cholesterol level could not be reliably predicted from the LSI. The ability of clinical personnel to visually grade the degree of turbidity was evaluated by having them assign a turbidity score of 0 to 4+ to 39 hematocrit tubes which contained clear, hemolyzed, or icteric serum, each of which had IL concentrations varying from 0 to 292 mg/dl. The 15 tubes of identical IL concentration of 99 mg/dl were graded from 0 to 4+ by two of the observers, from 1 to 4+ by three of the observers, and 0 to 3+, 1 to 3+, and 2 or 3+ by one each of the observers. This study shows that (1) in vitro fluorometric LSI correlates well with IL concentrations; (2) in vivo correlations of LSI with FFA, cholesterol, and TG are poor; and (3) personnel are unable to reliably grade turbidity by visual examination of hematocrit tubes. Infants on IL should be monitored by TG and FFA levels.