Necrotizing enterocolitis and total parenteral nutrition-associated cholestasis

The proportion of patients with total parenteral nutrition (TPN)-associated cholestasis (TPN-AC) who have necrotizing enterocolitis (NEC) has increased markedly in the past ten years. Little is known about how these diseases affect each other. We retrospectively studied 24 patients with NEC and bowel necrosis or perforation who required surgical intervention. Patients were divided into two groups: those who had received TPN (NEC + TPN, n = 17) and those who had not (NEC, n = 7). As cholestasis was present clinically, or prolonged TPN was anticipated, liver biopsy was done. Bile acid levels were measured in both serum and bile in 13 patients. Six patients, who underwent bowel resection and enterostomy, had a second liver biopsy and measurement of bile acid levels at stoma closure. Our results showed that in 13 patients for whom bile acid levels were measured (NEC + TPN, n = 6) (NEC, n = 7), serum bile acid level was significantly elevated in both groups over normal for age. Biliary bile acid levels were correspondingly depressed in both groups suggesting a failure of bile acid transport. All patients had abnormal liver histology, but the pattern of injury differed between the two groups. Those in the NEC group had biliary stasis and mild hepatocyte degeneration. In contrast, 15 of 17 in the NEC + TPN group had advanced injury specific for TPN-AC. All six patients managed on TPN and partial enteral feeding before a second biopsy had no change in bile acid levels and progression of histologic injury. We conclude that NEC alone can cause functional cholestasis and histologic liver injury but does not cause the specific progressive damage caused by TPN. NEC may make the liver more susceptible to the effects of TPN. Partial enteral feeding does not halt or reverse this injury.

Biliary lipid composition and bile acid profiles during and after enteral fast of total parenteral nutrition in the rabbit

Feeding and fasting influence biliary lipid composition. With total parenteral nutrition (TPN), it is possible to study the effects of a long-term "enteral fast" on biliary lipid composition without the metabolic ill-effects of nutrient deprivation. We compared the lipid and bile acid (BA) contents of hepatic and gallbladder biles in rabbits on completion of a 14-day regimen of TPN with those in rabbits returned to oral feeds for 6 weeks after a similar spell of TPN. Chow-fed rabbits served as controls. With TPN, plasma phospholipid and cholesterol levels were elevated. Basal bile flow and the secretion of bile acids and phospholipids were decreased in the TPN and post-TPN groups, while the cholesterol secretion rate was essentially unchanged. During TPN, the molar percent of cholesterol (relative to bile acids and phospholipid) in hepatic bile was increased. Biliary glycolithocholic acid (GLCA; as a percent of total conjugated BA) in hepatic bile increased from 1.7% (0.9% SEM) in the chow-fed to 8.5% (1.5% SEM) during TPN. In TPN and post-TPN groups, the gallbladder was enlarged to more than twice normal (chow-fed) size, and contained a dark, mucoid bile (biliary sludge). In this bile, (a) there was a 2.5-fold increase in bile acid concentration; and (b) the molar percent of cholesterol decreased while that of bile acids increased. TPN produced a state of functional cholestasis, which extended into the post-TPN period. Gallbladder distension was the common denominator of the hepatobiliary dysfunction in the TPN and post-TPN rabbits. With sequestration of bile acids in the gallbladder during and after TPN, the circulating bile acid pool was constricted, and the enterohepatic circulation impaired. As cholesterol secretion was low at all times, cholesterol supersaturation did not occur. The molar percent of cholesterol in gallbladder bile decreased, while that of bile acids increased; this suggests absorption of cholesterol by gallbladder mucosa. The increase in biliary GLCA probably resulted from bacterial biotransformation of glycochenodeoxycholic acid to lithocholic acid and its increased absorption from the cecum during TPN.

Biliary lithocholate and cholestasis during and after total parenteral nutrition: an experimental study

To evaluate the role of lithocholic acid (LCA) in the etiology of parenteral nutrition-associated cholestasis (PN-AC), we studied (i) the changes in the percentage of biliary LCA and (ii) the emergence and resolution of cholestatic changes in the liver after total parenteral nutrition (TPN) and after 6 weeks of oral feeding following the TPN. We compared these changes in rabbits on TPN support (via a central vein) for 14 days (TPN, n = 8) with those after 6 weeks of refeeding (Post-TPN, n = 8). Age-matched rabbits on lab chow served as controls (CHOW, n = 8). At the end of the diet regimens, the common bile duct was cannulated under anesthesia, and hepatic bile collected for measurements of bile flow and bile acid (BA) secretion rates, and BA profiles. The 60-min biliary excretion of sulfobromophthalein (BSP) after an intravenous bolus (5 mg/kg) was determined. A liver biopsy was taken for light microscopy. After 14 days of TPN, bile flow was reduced by 60%, bile acid secretion by 52%, and BSP excretion by 38%. On refeeding, only the BSP excretory rate recovered fully. In the TPN group, histology of the liver showed hepatocellular degeneration and portal tract inflammation; these resolved after refeeding leaving a mild portal fibrosis in 4/8 rabbits. Total colonic stasis occurred during TPN. With TPN, a decrease in the percentage of biliary glycochenodeoxycholate and an increase in LCA% were seen, whereas after refeeding the increase was in the percentage of glycoursodeoxycholate. An LCA% > or = 6 was associated with liver cell damage. After 6 weeks of refeeding, the structural cholestasis disappeared, but the decreases in basal bile flow and bile acid secretion (functional cholestasis) persisted. These data associate an increase in biliary LCA with the emergence of cholestasis during TPN in rabbits.

The effect of cholecystokinin-octapeptide on the hepatobiliary dysfunction caused by total parenteral nutrition

PURPOSE

Patients on total parenteral nutrition (TPN) commonly have hepatobiliary dysfunction. Interruption of the enterohepatic circulation (EHC) and gallbladder stasis are part of the pathogenesis. Cholecystokinin-octapeptide (CCK-OP), by emptying the gallbladder, stimulates the EHC. This study was performed to determine whether daily CCK-OP infusions can ameliorate the hepatobiliary dysfunction caused by TPN.

METHODS

Rabbits maintained on a standard TPN for 12 days were divided into two groups. One group (n = 6) received daily intravenous doses of CCK-OP, and the other (n = 13) received TPN only. A lab-chow-fed (LCF) group (n = 8) served as controls. The authors studied bile flow and bile acid secretion rates, sulfobromophthalein (BSP) secretion, gallbladder emptying in response to CCK-OP, and liver histology.

RESULTS

The LCF group had a bile flow of 82.3 microL/kg/min; that for the TPN-only group was 45.7 microL/kg/min (P < .001). The daily CCK-OP group did not improve more than the TPN-only group, with a bile flow of 45.8 microL/kg/min (P = NS). Bile acid secretion was 0.64 mumol/kg/min for the LCF group, 0.46 for the TPN-only group (P = NS), and 0.46 for the daily CCK-OP group (P = NS). TPN impaired the ability of the gallbladder to empty, and this was restored with daily CCK-OP. In the LCF group, the mean BSP secretion was 81.7% of a 5-mg/kg bolus within 60 minutes, compared with 72.5% in the daily CCK-OP group (P = NS) and 63.5% in the TPN-only group (P < .01). Histological examination of the liver showed that daily CCK-OP produced less periportal inflammation and fibrosis, although all TPN groups had hepatocyte damage in the centrilobular area.

CONCLUSION

Stimulation of the EHC with daily CCK-OP infusions during TPN decreased periportal inflammation and fibrosis, maintained gallbladder emptying capacity, and improved organic anion (BSP) secretion, although bile flow and bile acid secretion were not improved, and hepatocyte damage persisted.

Total parenteral nutrition-associated cholestasis: clinical and histopathologic correlation

Cholestatic jaundice is the major complication of total parenteral nutrition (TPN) in infants and children. The pathogenesis of this syndrome is poorly understood. The aims of this study were: (1) to define the histologic liver injury in relation to the clinical course of infants on TPN and (2) to determine whether enteral feeding will reverse or halt these changes. We identified 31 infants treated for severe gastrointestinal disease for whom liver histology was available from 1987 to 1991. Clinical records and liver biopsy (23) or autopsy specimens (13) were reviewed. Five patients had biopsies at two subsequent operations. The clinical diagnosis was necrotizing enterocolitis (24), atresia or stenosis (3), midgut volvulus (2), Hirschsprung's disease (1), and sepsis (1). Twenty-one of 31 infants were premature and had a mean birth weight of 1,868 g. Twenty-five of 31 were on TPN and 28 of 31 had received some enteral feeding by the time of the biopsy. Enteral feeding was begun as early as possible in all infants even if continued TPN was necessary for full support. Cholestasis occurred in 71% of premature infants versus 22% of full-term babies. Infants with cholestasis had been on TPN for a longer time (37 days v 18) with a correspondingly shorter period of enteral feeding (17 days v 27). Mean total bilirubin level was 14 in patients with cholestasis and 5 in those without, but the bilirubin level did not correlate with the extent of histological injury and was frequently normal despite marked histological damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatobiliary dysfunction during total parenteral nutrition is caused by infusate, not the route of administration

Cholestatic jaundice is the major complication of total parenteral nutrition (TPN). Both the intravenous (IV) route of nutrition and the enteral fast have been implicated as causes of TPN-associated cholestasis (TPN-AC). The purpose of this study was to determine whether TPN-AC is caused by the TPN solution itself or the IV route of administration and enteral fast. Prepubescent rabbits (n = 24) were divided into four groups: CONTROL, fed standard lab chow; TPN, received a standard hyperalimentation solution of dextrose, Aminosyn, and lipids via the jugular vein; ENT, received the same hyperalimentation solution via a duodenostomy tube; and OSM, received a polymeric formula (Osmolite) via a duodenostomy tube. After 14 days on these diets, we measured bile flow, bile acid excretion, sulfobromophthalein (BSP) excretion, plasma amino acid profile, serum liver enzymes, and liver histology. Statistical analysis was by analysis of variance. Hyperalimentation solution significantly depressed hepatobiliary function, whether it was given IV or by gut. Bile flow in both the TPN (36.4 microL/kg/min) and ENT (46.2) groups was significantly less than CONTROL (84.5) or OSM (62.9). Hepatic secretory function, measured by excretion of the cholephilic dye BSP, was depressed in both TPN and ENT (57% and 55% of IV dose excreted in bile over 60 minutes, respectively) compared with CONTROL (84%) or OSM (71%). Serum liver enzymes were normal in all groups. Histological injury similar to TPN-AC in humans (portal inflammation and hepatocyte degeneration) was seen in both groups receiving the hyperalimentation solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Early hepatobiliary dysfunction during total parenteral nutrition: an experimental study

The etiology and pathophysiology of the liver disease associated with total parenteral nutrition (TPN) are unknown. In this study, we have attempted to define the early changes in hepatobiliary function during TPN in young rabbits nourished totally by the intravenous route for 3, 5, and 15 days, with age-matched rabbits on lab chow serving as controls. A decrease in basal bile flow along with elevations of serum bile acids and cholesterol was seen. The capacity for biliary secretion of sulfobromophthalein and of ursodeoxycholic acid was measured at the end of each diet regimen. Early impairment of biliary sulfobromophthalein (BSP) secretion was seen after 5 days of TPN, with no further deterioration after 15 days. Maximal bile acid secretory rate and bile flow, in response to the ursodeoxycholic acid load, were decreased after 15 days of TPN. Furthermore, after 15 days of TPN, both the volume of gallbladder bile and its bile acid content increased. The combined effects of the enteral fast and the intravenous administration of all nutrients were bile acid sequestration in an adynamic gallbladder with interruption of the enterohepatic circulation. In the parenterally fed rabbit, we have demonstrated bile secretory failure and gallbladder sludge, the two common complications of clinical TPN. These may be the early events that subsequently lead to cholestasis and liver damage in neonates maintained on prolonged TPN.

Hepatic organic anion transport kinetics and bile flow during short-term total parenteral nutrition in the rabbit

Plasma disappearance of sulfobromophthalein (BSP) after an intravenous bolus (5 mg/kg) was determined in six lab chow-fed (LCF) rabbits and in six rabbits maintained on total parenteral nutrition (TPN) for 5 days. A common bile duct cannula enabled measurements of bile flow and biliary BSP excretion. Compartmental analysis of the biexponential plasma disappearance curve yielded three fractional transfer rates, plasma to liver (hepatic uptake), liver to plasma (reflux), and liver to bile (canalicular excretion). The transfer rates for hepatic uptake were 0.253 +/- 0.061/min for LCF and 0.147 +/- 0.040/min for TPN (P less than 0.01) and for the canalicular excretion of BSP were 0.038 +/- 0.019/min for LCF and 0.019 +/- 0.002/min for TPN (P less than 0.05). Model-computed rates for BSP excretion in bile over 60 min were lower with TPN (61%) than with LCF (80%); the measured excretory rates were 53% for TPN rabbits and 75% of injected dose for LCF animals. Basal biliary flow was reduced by 50% in the TPN group. With a two-compartmental model, assuming two pools and three transfer rates, we have demonstrated for the first time significant decreases in hepatic uptake and canalicular excretion of the organic anion BSP during TPN. A decrease in hepatic blood flow due to the enteral fast of TPN could have contributed in part to the decreased hepatic uptake. But, because the second exponent of the biexponential curve is independent of hepatic blood flow, the decrease in liver to bile transfer rate is a true approximation of a diminished canalicular excretory capacity during TPN. It is concluded that the movement of organic anions along the hepatic BSP/bilirubin transport system is impaired early during TPN.

End-tidal CO2 and tissue pH in the monitoring of acid-base changes: a composite technique for continuous, minimally invasive monitoring

The infrared CO2 analyzer continuously monitors the CO2 tension in exhaled air at end-tidal expiration. In experimental animals, we found a consistent relationship between PaCO2 and end-tidal CO2 (ET.CO2) in the normal steady state, and in acid-base disturbances (respiratory acidosis and alkalosis, and hypoperfusion acidosis). Paired data analyses of PaCO2 (X) and ET.CO2 (Y) yielded correlation coefficients of r = 0.98 (Y = 0.96X + 4.43) during progressive hypercarbia (PaCO2: 32----110 torr), and r = 0.93 (Y = 0.89X + 0.93) during hyperventilation hypocapnia (PaCO2: 41----14 torr). The relationship between PaCO2 and ET.CO2 was seen during hypovolemic shock if pulmonary perfusion was maintained uniform in all areas of lung. The ability of the ET.CO2 sensor to predict instantaneously the PaCO2 makes it attractive enough to be used in conjunction with the subcutaneous tissue pH(pHe) sensor in the management of acid-base disturbances. After hypercarbia (FiCO2 0.15 X 40 min; PaCO2/ET.CO2: 100/101 torr), when the dogs were returned to room air, abruptly both the ET.CO2 and pHe sensors were sensitive to the changes in Fi.CO2. But the response of the ET.CO2 was swifter. The advent of transcutaneous gas monitors has shown that intermittent blood gas analyses, however frequent, are inadequate for the monitoring of the rapidly altering blood gas status in the acutely ill. The ability of the pHe sensor to identify whole-body acidosis and alkalosis combined with the speed and ease of the ET.CO2 monitor in pinpointing hypercarbic and hypocarbic states makes this two-parameter system suitable for the continuous, noninvasive monitoring of the critically ill.

Continuous monitoring of pH in the tissue mode: evaluation of a miniature sensor during acidosis and tissue hypoperfusion

The in vivo performance of a 20G copolymer pH sensor, needlelike in configuration, was studied in the normal dog, and dogs made acidotic by the constant infusion of lactic acid, or by the induction of tissue perfusion defects. Sensors were placed at two extravascular sites in the leg, deep subcutaneous (pHe/sc), and intramuscular in the adductor (pHe/im). This pH sensor is a silver wire capped by a H+-specific polymer; it has a built-in reference system. Its electrochemical characteristics and in vivo performance are similar to those of glass pH electrodes. The continuously monitored values were compared with discrete arterial blood gas analyses at 10 to 20 minute intervals. The baseline values in 15 dogs under general anesthesia were: pH/art 7.331 +/- .042, pHe/sc 7.291 +/- .076, and pHe/im 7.265 +/- .102 (mean +/- SD; n = 45 observations each). During metabolic acidosis (lactic acid infusion), the direction and rates of change were similar in pHe/sc and pHe/im. Tissue perfusion defects were induced by moderate-to-severe hemorrhage (single or repeated bleeds) or operative shock (splenectomy and exteriorization of bowel). Both pHe/sc and pHe/im fell sharply, with a more gradual drop in pH/art. In those who survived after infusion of shed blood or dextran-40, pHe recovered rapidly. In the moribund, pHe continued to deteriorate. This pH sensor is a sensitive prognosticator of acid-base changes in the tissue. The in vivo drift is small: 0.008 pH per hour. The placement of the sensor via an intracath cannula in the subcutaneous tissue of the thigh is recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal development of lipid-clearing enzymes in the suckling animal

Age-related changes in the enzyme activities in the storage and secretory pools of extrahepatic lipoprotein lipase and hepatic triglyceride lipase were determined during a primed/constant infusion of heparin for 2 hr in puppies between birth and 18 wk of life. Lipoprotein lipase activity was low in the first 4 wk of suckling. Its storage pool increased 6-fold in the next 14 wk, with a less dramatic rise in the secretory pool. Sustained increases in the activity of this enzyme were seen late when (1) the pup was being weaned, and (2) the insulin-dependent glucoregulatory mechanism had matured. Both phases of hepatic triglyceride lipase were well developed at birth reflecting the metabolic maturity of the liver at birth. The ability to clear intravenous lipid during a 2-hr infusion was also measured in the pups. The rate of Intralipid utilization increased from 198 +/- 43 mg/kg/hr in the first week of life to 424 +/- 20 mg/kg/hr at 12 wk. Blood Intralipid homeostasis was causally related to increased activity in the storage and secretory pools of lipoprotein lipase. The progressive increase in lipoprotein lipase activity and the maintenance of the secretory capacity was dependent on the growth of the muscle mass and its capillary bed. Endogenous insulin rather than the fat content of the feed appeared significant in the postnatal development of the heparin-releasable lipid clearing enzymes.

The storage and synthetic pools of heparin-releasable lipoprotein lipase and hepatic triacylglycerol lipase in the growing puppy

Age-related changes in the activities of extrahepatic lipoprotein lipase and hepatic triacylglycerol lipase were determined during a primed/constant-rate infusion of heparin for 2 h in puppies between birth and 18 weeks of age. The early (storage) and late (synthetic) phases were measured. Both phases of hepatic triacylglycerol lipase activity were well developed in the first week, reflecting the metabolic maturity of the liver at birth. During the 18 weeks of study, the activity remained relatively unchanged except for a sharp peak at 12 weeks. Extrahepatic lipoprotein lipase activity was low in the first 4 weeks of suckling. Its storage pool increased 6-fold in the next 14 weeks, with a less marked rise in its late (synthetic) pool. Sustained increases in the activity of this enzyme were first noticed during weaning, when the insulin-secretory response matured. Endogenous insulin-secretory capacity rather than the fat content of the feed appeared significant in the postnatal development of lipoprotein lipase (Clearing-factor lipase) activity.

Depression of glucose utilization by Intralipid in the post-traumatic period: an experimental study

We investigated the accelerated clearance of Intralipid (IL) in the immediate post-traumatic period and the influence of the concomitant rise in fatty acid ((FFA) metabolism on carbohydrate tolerance. As a result we postulate that intermediary products of fatty acid oxidation inhibit key enzymes in the glycolytic pathway. The fatty acidemia and its metabolic sequlae can be avoided by intermittent Intralipid supplementation (at low rates) during TPN. It will assure (1) a larger carbohydrate-to-fat caloric ratio during infusion and (2) cyclical regeneration of the enzyme systems involved in lipid metabolism.

Parenteral nutritional support in children with cancer

Acute and chronic starvation is often associated with childhood cancer. Total parenteral nutrition (TPN) with 20% glucose and 3.0% amino acids, and minerals and vitamins was instituted to treat or prevent malnutrition in 41 children with cancer, ages three months to 18 years. TPN was required for anorexia, vomiting and diarrhea associated with anti-cancer therapy in 33 patients for intestinal complications or surgery in nine, and for preoperative correction of malnutrition in two. During TPN, general nutrition and appearance improved in all patients. Weight gain was noted in most. Despite gastrointestinal complications which usually require the interruption of chemotherapy and irradiation, in 21 children treatment could be continued at full dose with nutritional support by TPN. TPN was discontinued in six patients when blood cultures became positive. Sepsis was treated successfully by removal of the central venous catheter in all six and administration of antibiotics in three. No metabolic complications were noted. TPN appears to be a safe and effective means of combating the malnutrition which may occur with cancer and its therapy.