Whole body protein kinetics in severely septic patients. The response to glucose infusion and total parenteral nutrition

Growth hormone therapy initiated before starvation ameliorates the catabolic state and enhances the protein-sparing effect of total parenteral nutrition

The effect of 7 days of subcutaneously administered bovine growth hormone (bGH) (0.2 mg kg-1 day-1; n = 4) or an equivalent volume of 0.15 mol l-1 saline (n = 3) on protein metabolism was assessed in lambs. The catabolic response to 48 h of starvation and subsequent hypocaloric total parenteral nutrition (TPN) was measured using primed constant intravenous infusions of [15N]urea and [14C]leucine. Following 48 h of starvation and 7 h of TPN, bGH-treated animals had a significantly decreased rate of net protein catabolism compared with controls (mean(s.e.m.) 2.4(0.2) versus 3.2(0.3) g kg-1 day-1, P < 0.01). The mean(s.e.m.) rate of whole-body protein catabolism was also significantly decreased in bGH-treated animals at 10.9(0.3) g kg-1 day-1 compared with 12.9(0.7) g kg-1 day-1 in saline-treated controls (P < 0.05). In addition, the rates of net and whole-body protein catabolism decreased significantly (P < 0.05) during the period of hypocaloric parenteral feeding to mean(s.e.m.) values of 2.3(0.2) and 8.6(0.6) g kg-1 day-1 respectively in bGH-treated animals. By contrast, in saline-treated controls net and whole-body protein catabolism continued to increase during hypocaloric parenteral feeding. There was a significant decrease (P < 0.05) in the rate of [14C]leucine uptake in tissues of the gastrointestinal tract, heart and diaphragm in bGH-treated animals compared with controls. These results demonstrate that daily administration of growth hormone decreases the catabolic response to a metabolic stress, resulting in the conservation of protein in the heart, diaphragm, gastrointestinal tract and musculoskeletal system by a primary anticatabolic action. In addition, growth hormone therapy initiated before induction of the catabolic state enhances the protein-sparing effects of TPN. Further study is justified to determine whether growth hormone therapy initiated before elective or urgent surgery in the nutritionally depleted patient may have a role in reducing the severity of the postoperative catabolic state, particularly in the patient in whom a complicated course is anticipated.

Metabolic basis for management of the septic surgical patient

The physiologic events accompanying postoperative septic complications in surgical patients represent a coordinated response to bacterial invasion, which is aimed at maintaining the function of key organ systems. When sepsis is prolonged or overwhelming, physiologic dysfunction and multiorgan failure develop. This review outlines the pathophysiologic response to sepsis and correlates it with recent therapeutic advances in the metabolic management of the postoperative septic patient.

Enhancement of the anabolic effects of growth hormone and insulin-like growth factor I by use of both agents simultaneously

The use of growth hormone (GH) as an anabolic agent is limited by its tendency to cause hyperglycemia and by its inability to reverse nitrogen wasting in some catabolic conditions. In a previous study comparing the anabolic actions of GH and IGF-I (insulin-like growth factor I), we observed that intravenous infusions of IGF-I (12 micrograms/kg ideal body wt [IBW]/h) attenuated nitrogen wasting to a degree comparable to GH given subcutaneously at a standard dose of 0.05 mg/kg IBW per d. IGF-I, however, had a tendency to cause hypoglycemia. In the present study, we treated seven calorically restricted (20 kcal/kg IBW per d) normal volunteers with a combination of GH and IGF-I (using the same doses as in the previous study) and compared its effects on anabolism and carbohydrate metabolism to treatment with IGF-I alone. The GH/IGF-I combination caused significantly greater nitrogen retention (262 +/- 43 mmol/d, mean +/- SD) compared to IGF-I alone (108 +/- 29 mmol/d; P < 0.001). GH/IGF-I treatment resulted in substantial urinary potassium conservation (34 +/- 3 mmol/d, mean +/- SE; P < 0.001), suggesting that most protein accretion occurred in muscle and connective tissue. GH attenuated the hypoglycemia induced by IGF-I as indicated by fewer hypoglycemic episodes and higher capillary blood glucose concentrations on GH/IGF-I (4.3 +/- 1.0 mmol/liter, mean +/- SD) compared to IGF-I alone (3.8 +/- 0.8 mmol/liter; P < 0.001). IGF-I caused a marked decline in C-peptide (1,165 +/- 341 pmol/liter; mean +/- SD) compared to the GH/IGF-I combination (2,280 +/- 612 pmol/liter; P < 0.001), suggesting maintenance of normal carbohydrate metabolism with the latter regimen. GH/IGF-I produced higher serum IGF-I concentrations (1,854 +/- 708 micrograms/liter; mean +/- SD) compared to IGF-I only treatment (1,092 +/- 503 micrograms/liter; P < 0.001). This observation was associated with increased concentrations of IGF binding protein 3 and acid-labile subunit on GH/IGF-I treatment and decreased concentrations on IGF-I alone. These results suggest that the combination of GH and IGF-I treatment is substantially more anabolic than either IGF-I or GH alone. GH/IGF-I treatment also attenuates the hypoglycemia caused by IGF-I alone. GH/IGF-I treatment could have important applications in diseases associated with catabolism.

Effects of recombinant human growth hormone in patients with severe sepsis

The objective of this study was to evaluate the safety and the effect of recombinant exogenous growth hormone (GH) on nitrogen production in patients with severe sepsis. It was designed as a prospective, randomized, placebo-controlled trial, and performed in the medical intensive care unit of a university hospital. Twenty patients admitted with septic shock and receiving standard parenteral nutrition served as subjects. Treatment consisted of GH 0.1 mg/kg/day or placebo administered as continuous intravenous infusion on the second, third, and fourth days after admission. The study period was eight days. During GH administration, nitrogen production decreased significantly in the GH group and increased in controls (p < 0.01). Nitrogen balance became slightly positive in the GH group during treatment: 1.2 +/- 6.4 versus controls -3.7 +/- 3.8 g/day (day 3) (p < 0.05). Within 24 hours after cessation of treatment, differences between GH and controls disappeared. 3-Methylhistidine excretion as a measure of absolute muscle breakdown declined during the study period, but did not differ between groups. The levels of insulin, insulinlike growth factor 1, glycerol, free fatty acids, and beta-hydroxybutyrate increased during treatment. Despite continuous intravenous administration, GH levels gradually declined during the 3 treatment days, indicating increased metabolic clearance. Side effects other than insulin resistance were not observed. Growth hormone administration reduces nitrogen production and improves nitrogen balance in patients with severe sepsis. These effects are not sustained after cessation of treatment.

Metabolism and nutritional frontiers in pediatric surgical patients

The successful treatment of pediatric surgical disease requires an understanding of the acute metabolic stress response. Poor clinical outcome can result when the metabolic demands of acute injury exceed the ability of endogenous host mechanisms to compensate. Appropriate exogenous supplementation may provide the metabolic and nutritional support crucial to recovery. As knowledge in this area grows, more effective treatment strategies are evolving. The potential for further advances, especially in the infant critical care population, offers the hope for substantial progress in the near future.

Nutrition in acute pulmonary disease

Acutely stressed patients with chronic pulmonary disease have a particular need for accurate nutritional assessment and appropriate nutritional therapy. Loss of skeletal muscle, often extensive, can be paralleled by dramatic alterations in cellular function; inadvertent provision of excessive calories or of individual substrates may produce more harm than benefit. In the absence of a single "gold standard" for nutritional assessment and monitoring, no single value should take precedence over the entire clinical picture, which should be thoughtfully assessed and reassessed, with both the patient's nutritional needs and the consequences of their provision kept in mind. In the future, assessments of the impact of nutritional intervention will probably rely more heavily on functional tests of specific organs and of the immune system. Intervention will be based not only on provision of calories, individual substrates, vitamins, and minerals, but also on control of the inflammatory response in order that the nutrients may be properly utilized.

Special considerations required for the formulation and administration of total parenteral nutrition therapy in the elderly patient

Providing total parenteral nutrition (TPN) to hospitalised patients is not a benign procedure and can be associated with appreciable risks including the development of septic, mechanical and/or metabolic complications. In the older patient, the risks are heightened due to the effects of aging on vital organ function, as well as on the body's ability to respond to injury and infection. In addition, the existence of co-morbid disease will increase the rate of complications. The design of nutritional regimens must account for the changes in body composition and function with age in order to reduce the risks of nutrition-related complications. As a consequence of the reduction in lean body mass and organ function, coupled with the need to mobilise endogenous protein during acute metabolic stress, it is prudent to provide protein intakes of 1.5 g/kg/day, similar to amounts given to younger adult populations. In contrast, the caloric intake should be reduced by as much as 30% from amounts given younger adults of equivalent height and weight in order to avoid the dangers of overfeeding. Single-fuel systems may be better choices in those with acute cardiovascular disease, as glucose is a preferred fuel in this setting, whereas a mixed-fuel system will generally allow improved glucose homeostasis in the diabetic patient. Once TPN is instituted, metabolic management may be as important as nutritional support. Critical illness is associated with a variety of electrolyte disorders which are often accentuated by concurrent drug therapy and pre-existing co-morbid disease. The older patient is often less able to withstand abrupt changes in metabolic homeostasis. These points underscore the importance of the careful application of TPN therapy in the older patient.

Effect of glutamine-supplemented total parenteral nutrition on the small bowel of septic rats

In order to study the effect of total parenteral nutrition (TPN) with or without glutamine supplementation in septic rats, septic Wistar albino rats were randomly assigned to receive 0.23 g of nitrogen and 113 kJ (100 g BW)(-1) per day in the form of amino acids with (group 2) or without (group 1) glutamine supplementation or 10% (w/v) glucose only (group 3). After 4 days of TPN treatments, rats receiving glutamine-supplemented TPN had a cumulative nitrogen balance of -24.4 +/- 3.3 mg N, which was significantly (P < 0.001) better compared to other TPN-treated groups. Septic rats of group 2 survived sepsis significantly (P < 0.001) better than those in groups 1 and 3. Glutamine-supplemented TPN treatment resulted in significant increases in jejunal weight (P < 0.001), DNA and protein contents (P < 0.001), villous height (P < 0.001) and crypt depth (P < 0.001) when compared with septic rats of group 1. Septic rats of group 2 extracted and metabolised glutamine by the small bowel at higher rates (P < 0.001) than that observed in septic rats of group 1. Increases in jejunal glutaminase (38.2%, P < 0.001) and decreases in glutamine synthetase (41.7%, P < 0.001) activities were observed in response to glutamine-supplemented TPN treatment. It is concluded that the administration of glutamine-supplemented TPN is beneficial to the small bowel of septic rats.

Total parenteral nutrition 1990. A review of its current status in hospitalised patients, and the need for patient-specific feeding

The decision to initiate total parenteral nutrition (TPN) in hospitalised patients should be based on the presence of clinically significant starvation and dysfunction of the gastrointestinal tract. It must also take into account the clinical status of the patient, considering major treatment strategies and the need for prolonged hospitalisation, the benefits of feeding and the attendant risks of central venous alimentation. Recent evidence in surgical patients in intensive care provides the impetus for early parenteral feeding; withholding TPN and inducing a cumulative caloric deficit of greater than or equal to 10,000 calories has been associated with a survival disadvantage compared to those patients with a positive caloric balance. Moreover, the incidence of serious organ failure was consistently higher in the group with cumulative caloric deficits. Additional evidence favouring the provision of TPN exists, but the axiom 'if the gut works, use it' still prevails. Exceptions to this precept do exist, however, particularly in critically ill patients. The metabolic derangements encountered in these patients could be so severe that it may be impossible to correct the electrolyte and acid-base abnormalities via the enteral route. For example, such patients may have large potassium requirements and/or severe alkalaemia necessitating systemic acidification with hydrochloric acid, precluding enteral delivery due to gastrointestinal intolerance. In this setting, combined enteral feeding with 10 to 20 ml/h to maintain gut integrity (via a post-pyloric feeding tube) and TPN during the acute phases of illness is an exciting possibility. Once the decision to feed is made, the amount of nutrition prescribed may assume equal importance with respect to patient outcome. The frequent use of the Harris-Benedict equation, plus a multiplying factor for stress, may overestimate caloric requirements; this is particularly true during critical illness. The dangers of overfeeding may be just as harmful as not feeding at all. The use of indirect calorimetry provides the most accurate measurement of resting energy expenditure. However, in the absence of indirect calorimetry, modified equations to estimate caloric needs are available. Caution must be observed as caloric intakes exceeding the range of 25 to 35 kcal/kg may be dangerous, particularly in the severely ill patient with preexisting organ failure. The amount of protein and the 'calorie-mix' necessary for optimal nutritional support is open to debate. Recent evidence has demonstrated no additional benefit to nitrogen balance in severely septic patients when protein was given at a level exceeding 1.5 g/kg/day.(ABSTRACT TRUNCATED AT 400 WORDS)

Metabolic effects of recombinant human growth hormone: isotopic studies in the postabsorptive state and during total parenteral nutrition

We have performed a series of isotopic studies in 25 adult patients with sepsis and/or trauma in order to determine the metabolic effects of recombinant human growth hormone (rHGH) administration. Twelve of the patients were receiving total parenteral nutrition, and 13 were eating a normal ward diet and were studied postabsorption. Energy and protein kinetics were quantified isotopically before rHGH administration and following a 3-day course of rHGH (20 units subcutaneously daily). In the total parenteral nutrition group the rate of net loss of protein decreased from 0.82(0.17) g kg-1 day-1 to 0.43(0.20) g kg-1 day-1 (P less than 0.02) following the administration of rHGH. The rate of appearance of leucine was not altered, suggesting that the improvement in nitrogen balance following rHGH was because of an increased rate of protein synthesis rather than reduced catabolism. In the postabsorptive group, rHGH treatment significantly increased the rate of appearance of free fatty acids (from 7.4(2.2) mumol kg-1 min-1 to 11.1(2.6) mumol kg-1 min-1, P less than 0.03) and free fatty oxidation (from 1.3(0.4) mumol kg-1 min-1 to 1.7(0.4) mumol kg-1 min-1, P less than 0.06), while the rate of leucine oxidation was reduced (from 0.44(0.05) mumol kg-1 min-1 to 0.26(0.03) mumol kg-1 min-1, P less than 0.005). Glucose appearance and oxidation remained unchanged. These results suggest that fat was being oxidized in preference to protein, which resulted in a reduction in the net rate of loss of protein of 0.3 g kg-1 day-1 (P less than 0.05). We conclude that rHGH administration is capable of significantly reducing net protein loss in septic or injured surgical patients. Recombinant HGH may be clinically useful in supporting critically ill surgical patients who require intensive nutritional support.

Effect of administered human growth hormone on protein metabolism in septic rats

The effect of administered human growth hormone (hGH) on protein metabolism in septic rats was investigated. Fifty-three male Wistar rates with SVC cannulation were divided into four groups. Group I (n = 10) underwent sham-operation. Sepsis was induced by cecal ligation in group II (n = 19), group III (n = 10), and group IV (n = 14). Isocaloric, isonitrogenous glucose/amino acids were infused for 4 days. hGH was administered in group III (100 mU/day) and group IV (200 mU/day) every day. Cumulative nitrogen balance (mg/kg) in group IV was significantly higher than in group II (p less than 0.01): group I, 1264 +/- 355; group II, 117 +/- 693; group III, 92 +/- 735; group IV, 1001 +/- 279. Cumulative urinary excretion of 3-methylhistidine (3-MH, mg/kg) did not differ between group II and group IV: group I, 6.2 +/- 0.9; group II, 12.0 +/- 2.2; group III, 13.4 +/- 2.9; group IV, 10.5 +/- 2.3. Serum albumin level in group IV (1.8 +/- 0.2 g/dl) was significantly higher than in group II (1.5 +/- 0.2 g/dl) (p less than 0.01). Blood urea nitrogen level in group IV (12.6 +/- 2.3 mg/dl) was significantly lower than in group II (18.8 +/- 7.4 mg/dl) (p less than 0.05). Although serum levels of glucose, insulin, triglyceride, and phospholipid were higher in sepsis groups than in sham-operated group, those levels did not differ among sepsis groups. Administration of hGH, 200 mU/day, resulted in marked nitrogen retention and had little effect on 3-MH excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of insulin and glucose oxidation in mediating the protein catabolism of burns and sepsis

We have investigated the responsiveness of protein kinetics to insulin and the role of glucose oxidation rate as a mediator of the protein catabolic response to burn injury and sepsis by assessing the response of leucine and urea kinetics to a 5-h hyperinsulinemic euglycemic clamp with and without the simultaneous administration of dichloroacetate (DCA) (to further increase glucose oxidation via stimulation of pyruvate dehydrogenase activity) in eight severely burned and eight septic patients. Leucine and urea kinetics were measured by the primed-constant infusions of [1(-13)C]leucine and [15N2]urea. Compared with controls, basal leucine kinetics (flux and oxidation) were significantly elevated (P less than 0.01) in both groups of patients. Hyperinsulinemia elicited significant (P less than 0.05) decreases in leucine kinetics in both groups of patients. Consistent with this observation, hyperinsulinemia caused urea production to decrease significantly (P less than 0.05) in both patient groups. The administration of DCA to patients during hyperinsulinemia elicited a significant increase in glucose oxidation rate compared with the clamp rate (P less than 0.05), and the percent of glucose uptake oxidized increased from 45.5 +/- 5.5 to 53.5 +/- 4.8%; yet the response of leucine and urea kinetics to the clamp plus DCA was not different from the response to the clamp alone. These results suggest that the maximal effectiveness of insulin to suppress protein breakdown is not impaired and that a deficit in glucose oxidation or energy supply is probably not playing a major role in mediating the protein catabolic response to severe burn injury and sepsis.

Low protein diets improve survival from peritonitis in guinea pigs

Enteral diets with different protein content were tested to determine their effect on outcome in a model of protracted bacterial peritonitis. Hartley guinea pigs were provided with gastrostomies, and 1 week later, osmotic pumps were implanted into the peritoneal cavity to allow for continuous release of live bacteria over the course of 1 week. Three days after pump implantation, the animals began receiving isocaloric enteral diets that contained 5%, 10%, 15%, or 20% of total calories as protein. After 2 weeks of observation, the survivors were killed. All animals lost weight during the 2-weeks period, but there was no difference in weight lost. Nitrogen balance correlated with dietary protein. The mortality rate was significantly higher in the groups that received 15% and 20% of total calories compared with the group that received 5% (p less than 0.05). Although dietary protein in the 5% group was insufficient for meeting the nutritional needs of the animal, survival was best in this group. Possible explanations are that protein restriction in this model may either augment host defence or impair bacterial virulence.

Metabolic response to sepsis and trauma

This review examines current knowledge regarding the metabolic responses to trauma and sepsis. The factors which may mediate the responses are discussed and the potential value of pharmacological or nutritional manipulation is reviewed.

Metabolic effects of recombinant human growth hormone in patients receiving parenteral nutrition

Recombinant human methionyl growth hormone (Protropin) (Genetech, Inc., San Francisco, CA) administered to normal volunteers receiving hypocaloric parenteral nutrition minimized weight loss and induced positive nitrogen balance. To evaluate whether growth hormone (GH) can promote anabolism in surgical patients, 11 stable malnourished individuals were studied. In the initial trial, subjects received a constant parenteral infusion of a hypocaloric diet that provided approximately 1100 kcal/24 hr and 1.3 g protein/kg/24 hr for at least 2 weeks. During 1 week, GH 10 mg was given subcutaneously daily, whereas the other week served as the control. Daily balance studies demonstrated that administration of GH resulted in significant retention of nitrogen (+3.4 g/24 h) and phosphorus (+218 mg/24 h), despite provision of only 60% of caloric requirements. With GH, serum blood urea nitrogen (BUN) and potassium fell, whereas glucose and insulin tended to rise, and levels of insulin-like growth factor 1 increased three to fourfold. Weight gain occurred with GH and was associated with positive mineral and water balance. Six patients received GH (10 mg subcutaneously daily) for 13-25 consecutive days after an initial control week. Significant nitrogen and phosphorus retention occurred over the entire period of GH administration, and no significant side effects were observed. In these depleted patients, GH caused significant and sustained nitrogen retention over a wide range of nutritional support. GH appears to enhance the efficacy of parenteral nutrition in stable individuals requiring repletion of body protein.