Sequential changes in the metabolic response in severely septic patients during the first 23 days after the onset of peritonitis

Impaired energy metabolism during neonatal sepsis: the effects of glutamine

Neonatal sepsis is an important cause of morbidity and mortality as a result of multiple organ system failure, particularly in neonates requiring total parenteral nutrition. Suitable therapies and support are needed both to prevent sepsis and to prevent multiple organ failure. After bacterial infection, pro-inflammatory cytokines trigger the antimicrobial activity of macrophages and neutrophils, resulting in production of reactive species such as H2O2, NO, superoxide and peroxynitrite. However, excess production can lead to host tissue damage. Incubation of either hepatocytes or heart mitochondria from neonatal rats with these reactive species, or with cytokines, leads to impairment of mitochondrial oxidative function, and in an animal model of neonatal sepsis similar results to thein vitrofindings have been demonstrated. Recentin vivostudies, using indirect calorimetry of suckling rat pups, show that during endotoxaemia there is a profound hypometabolism, associated with hypothermia. Having determined that cellular oxidative function may be impaired during sepsis, it is of great importance to try to identify therapeutic measures. Much interest has been shown in glutamine, which may become essential during sepsis. It has been shown that hepatic glutamine is rapidly depleted during endotoxaemia. When hepatocytes from endotoxaemic rats were incubated with glutamine, there was a restoration of mitochondrial structure and metabolism.In vivo, intraperitoneal injection of glutamine into endotoxic suckling rats partially reversed hypometabolism, markedly reduced the incidence of hypothermia and improved clinical status. These results suggest that glutamine has a beneficial effect during sepsis in neonates.

How perioperative fluid balance influences postoperative outcomes

Fasting, anaesthesia and surgery affect the body's physiological capacity not only to control its external fluid and electrolyte balance but also the internal balance between the various body fluid compartments. Conversely, abnormalities of fluid and electrolyte balance may adversely affect organ function and surgical outcome. Perioperative fluid therapy has a direct bearing on outcome, and prescriptions should be tailored to the needs of the patient. The goal of fluid therapy in the elective setting is to maintain the effective circulatory volume while avoiding interstitial fluid overload whenever possible. Weight gain in elective surgical patients should be minimized in an attempt to achieve a 'zero fluid balance status'. On the other hand, these patients should arrive in the anaesthetic room in a state of normal fluid and electrolyte balance so as to avoid the need to resuscitate fluid-depleted patients in the anaesthetic room or after the induction of anaesthesia. Optimal fluid delivery should be part of an overall care package that involves minimization of the period of preoperative fasting, preoperative carbohydrate loading, thoracic epidural analgesia, avoidance of nasogastric tubes, early mobilization, and early return to oral feeding, as exemplified by the enhanced recovery after surgery programme.

Quantification of amino acid transport through interstitial fluid: assessment of four-compartment modeling for muscle protein kinetics

The purpose of this study was to assess a novel technique for quantifying in vivo muscle protein metabolism and phenylalanine transport in septic patients and normal volunteers and thereby assess the influence of sepsis on muscle protein kinetics. In patients resuscitated from sepsis, blood flow and edema may influence the extent of muscle loss. Six adult patients septic from pneumonia underwent a study protocol consisting of infusion of isotopic phenylalanine, indocyanine green dye, and sodium bromide; biopsies of skeletal muscle; and sampling from the femoral artery, vein, and interstitial fluid. Study results demonstrate a substantial net catabolism of muscle, an accelerated flux of phenylalanine, and an increased leg blood flow for septic patients compared with normal volunteers. For septic patients and normal volunteers, the rate of phenylalanine transport through the interstitium was rate limiting for the movement of phenylalanine between vasculature and muscle. Measurements demonstrate a concentration gradient of phenylalanine favoring the net efflux of amino acids from the leg in the septic patients. Despite whole body edema, the extracellular fluid volume within muscle of septic patients was similar to normal. These findings demonstrate that the extent of muscle loss in critically ill patients results from the net increase in the rate of muscle protein breakdown, which subsequently drives amino acids through the interstitial compartment down their concentration gradient. Therefore, any effective therapy to correct illness-induced muscle catabolism should be directed at altering the rates of breakdown and synthesis of muscle protein and are not likely related to tissue edema.

Supportive care in acute respiratory distress syndrome

Although the central focus of acute respiratory distress syndrome (ARDS) is the pathology within the lung, ARDS is very much a systemic disease. As such, the whole body needs care and support while the disease process within the lung runs its course. The issues of pain management, sedation, fluid balance, nutrition, metabolic and hormonal processes, infection control, and patient positioning are important for any patient in a critical care setting. For patients with ARDS, the required ventilatory support and ARDS-associated systemic inflammation mandate the above supportive measures.

Minimal access colonic surgery: is it truly minimally invasive?

Laparoscopic colonic surgery has an established role in the management of both benign and malignant conditions. Proposed benefits from laparoscopic surgery include decreased pain, decreased metabolic disturbance to the patient and faster recovery. It is now generally accepted that pro-inflammatory mediators, including cytokines, are to a great extent responsible for the metabolic changes associated with injury and surgery, and that these metabolic changes are related to postoperative recovery. Cytokine levels in the serum are decreased after major laparoscopic colorectal surgery compared with open surgery. However, the cytokine concentration in abdominal drain fluid is the same independent of the size of the incision and these concentrations are far higher than those found in the serum suggesting that the peritoneal would from the surgery itself is more important to metabolic events than the skin wound used to access the abdominal cavity to perform the operation. When looked at critically in programmes where patients are optimally managed perioperatively, there appears to be minimal metabolic benefit from performing a major colonic resection using minimal access surgery. Thus, it appears that the wound is critical when the operation involves only minor peritoneal disruption, such as in laparoscopic cholecystectomy, but when large peritoneal defects are created, such as in major colorectal surgery, then the skin wound becomes irrelevant to metabolism and hence recovery. Thus, minimal access does not necessarily equate to minimal invasion and the terms should not be used interchangeably in the context of laparoscopic colorectal surgery.

Hemodynamic and metabolic effects of selective beta1 adrenergic blockade during sepsis

BACKGROUND

Selective beta adrenergic antagonists are commonly used to reduce myocardial demise in patients at risk for cardiac-related death. The purpose of this study was to examine the hemodynamic and metabolic effects of cardiac selective beta adrenergic blockade in patients.

METHODS

Muscle protein kinetics were quantified using isotopic tracer methodology in 6 moderately septic, mechanically ventilated patients with pneumonia before and then at the conclusion of a 3-hour infusion of esmolol of sufficient dose to reduce heart rate by 20% from baseline. A battery of hemodynamic measurements as facilitated by a thermodilution pulmonary artery catheter and indirect calorimetry were also measured before and after the 3-hour selective beta adrenergic blockade.

RESULTS

Selective beta adrenergic blockade was associated with the 20% reduction in heart rate and a comparable decrease in cardiac output. Esmolol administration failed to affect systemic or pulmonary vascular resistance, oxygen consumption, hepatic or leg blood flow, energy expenditure, or ATP availability/energy charge within muscle. Esmolol infuse did incite a shift in fuel oxidation toward an increase in palmitate oxidation and with a decrease in the oxidation of glucose. There was no demonstrable influence beta1 adrenergic blockade on muscle protein kinetics.

CONCLUSIONS

Cardiac selective beta adrenergic blockade with esmolol reduces cardiac output in proportion to the percentage decreases in heart rate in moderately severe septic patients without adversely affecting oxygen utilization or hepatic, peripheral blood flow.

Lactic Acidosis in Gabonese Children with Severe Malaria Is Unrelated to Dehydration

BACKGROUND

Hyperlactatemia is an important and common complication of severe malaria. We investigated changes in fluid compartment volumes in patients with severe malaria and control patients with the use of bioimpedence analysis.

METHODS

We estimated extracellular water and total body water volumes in a total of 180 children: 56 with severe malaria, 94 with moderate malaria, 24 with respiratory tract infection, and 6 with severe diarrhea.

RESULTS

There was a mean (+/-SD) decrease in total body water volume of 17+/-24 mL/kg (or 3% of total body water volume) in patients with severe malaria. This compares with a mean (+/-SD) decrease in total body water volume of 33+/-28 mL/kg (or 6% of total body water volume) in patients with severe diarrhea. There was no increase in extracellular water volume in patients with severe malaria, suggesting no significant intravascular volume depletion in patients with severe malaria. There was no relationship between lactatemia and any changes in fluid compartment volumes.

CONCLUSIONS

The changes in fluid volumes that were observed are unlikely to be of physiological significance in the pathophysiology of severe malaria.

Nutrition support for patients in the intensive care unit

Enteral nutrition (EN) is the mainstay of nutrition delivery within intensive care seeking to capitalise on its benefits for the gastrointestinal tract and associated immune system, but this has brought new challenges in delivery to the sick. The hoped for benefit has led to the mistaken belief by some that parenteral nutrition (PN) is no longer required. However, a greater appreciation of the risks of EN delivery in the sick patient combined with improvements in PN formulation and use help explain why PN is not as risky as some have believed. Real outcome benefits have been described with the new glutamine containing PN formulations. PN remains important in the presence of gastrointestinal feed intolerance or failure.

Impact of oedema on recovery after major abdominal surgery and potential value of multifrequency bioimpedance measurements

Background

The consequences of generalized oedema following major abdominal surgery are under-recognized, and its causes are poorly understood.

Methods

Thirty-eight patients (21 men and 17 women) were observed for the occurrence of oedema after major abdominal surgery. Oedema formation was related to fluid balance, changes in whole-body bioimpedance (Z) measured at four frequencies (5, 50, 100 and 200 kHz), and clinical outcome.

Results

The 20 patients who developed oedema were older than those who did not (mean(s.d.) 73(9) versus 63(14) years; P = 0·007). Fluid intake over the first 5 days after surgery was similar in both groups, but those with oedema excreted less total fluid (16·9(2·4) versus 19·7(3·5) litres; P = 0·022). Oedema was associated with a delay in tolerating solid food (P = 0·001) and opening bowels (P = 0·020), a prolonged hospital stay (median 17 (range 8–59) versus 9 (range 4–27) days; P = 0·001) and more postoperative complications (13 of 20 versus four of 18 patients; P = 0·011). The preoperative ratio of whole-body impedance at 200 kHz to that at 5 kHz was higher in those who subsequently developed oedema (0·81(0·03) versus 0·78(0·02); P = 0·015).

Conclusion

The development of oedema after major abdominal surgery is associated with increased morbidity. Age and reduced ability to excrete administered fluid load are significant aetiological factors and bioimpedance analysis can potentially identify patients at risk.

Early enteral administration of immunonutrition in critically ill children: results of a blinded randomized controlled clinical trial

OBJECTIVES

In a blinded, prospective, randomized, controlled clinical trial, we compared nitrogen balance (NB), nutritional indices, antioxidant catalysts, and outcome in critically ill children given an immune-enhancing formula (I) or conventional early enteral nutrition (C).

METHODS

Fifty patients, 103 +/- 7 months old, with disorders prompting admission to the pediatric intensive care unit, including sepsis, respiratory failure, and severe head injury, were enrolled in the study. Within 12 h of admission, patients were randomized to receive I (n=25) or C (n=25). Caloric intake was aimed at meeting patient's predicted basal metabolic rate by day 2 and predicted energy expenditure by day 4, irrespective of group assignment. Outcome endpoints and complications were recorded; NB, transthyretin, retinol-binding protein, transferrin, zinc, copper, and metabolic indices were measured on days 1 and 5 and compared with clinical and nutritional characteristics within and between groups.

RESULTS

Both diets achieved their initial targets of covering predicted basal metabolic rate by day 2 and predicted energy expenditure by day 4. Twenty four-hour NB became positive in 40% of patients in group C and occurred in 64% of patients in group I by day 5. Only in group I did the mean NB become positive by day 5 (0.07+/-0.07 g/kg versus -0.24+/-0.03 g/kg on day 1, P<0.001) compared with group C in which the mean NB remained negative (-0.06+/-0.04 g/kg versus -0.25+/-0.06 g/kg on day 1, P<0.001). By day 5, nutritional indices and antioxidant catalysts showed a higher increasing trend in group I compared with group C and higher osmolality (P<0.02), sodium (P<0.03), and urea (P<0.04). Diarrhea for group I (P<0.02) and gastric distention for group C (P<0.04) were the most frequently recorded complications. Mortality or length of stay did not differ between groups, but there was a trend for less gastric gram plus isolates (P<0.05) or for Candida species (P<0.04) and nosocomial infections in group I compared with group C.

CONCLUSIONS

Although less well tolerated, immunonutrition is a feasible method of early enteral nutrition in the pediatric intensive care unit. It has a favorable effect on nutritional indices and antioxidant catalysts, but not on outcome hard endpoints. Although it poses a higher metabolic burden to the patient, it shows a trend to improve colonization and infection rates. Appropriate modifications for specific age populations might improve its tolerability and benefits among critically ill children.

IGF-I stimulates protein synthesis in skeletal muscle through multiple signaling pathways during sepsis

Chronic septic abscess formation causes an inhibition of protein synthesis in gastrocnemius not observed in rats with a sterile abscess. Inhibition is associated with an impaired mRNA translation initiation that can be ameliorated by elevating IGF-I but not insulin. The present study investigated the ability of IGF-I signaling to stimulate protein synthesis in gastrocnemius by accelerating mRNA translation initiation. Experiments were performed in perfused hindlimb preparations from rats 5 days after induction of a septic abscess. Protein synthesis in gastrocnemius from septic rats was accelerated twofold by the addition of IGF-I (10 nM) to perfusate. IGF-I increased the phosphorylation of translation repressor 4E-binding protein-1 (4E-BP1). Hyperphosphorylation of 4E-BP1 in response to IGF-I resulted in its dissociation from the inactive eukaryotic initiation factor (eIF) 4E.4E-BP1 complex. Assembly of the active eIF4F complex (as assessed by the association eIF4G with eIF4E) was increased twofold by IGF-I in the perfusate. In addition, phosphorylation of eIF4G and ribosomal protein S6 kinase-1 (S6K1) was also enhanced by IGF-I. Activation of mammalian target of rapamycin, an upstream kinase implicated in phosphorylating both 4E-BP1 and S6K1, was also observed. Thus the ability of IGF-I to accelerate protein synthesis during sepsis may be related to a stimulation of signaling to multiple steps in translation initiation with an ensuing increased phosphorylation of eIF4G, eIF4E availability, and S6K1 phosphorylation.

The impact of parenteral nutrition on the body composition of patients with acute pancreatitis

BACKGROUND

Nutrition support by the enteral route is now the preferred modality in patients with severe acute pancreatitis. Parenteral nutrition is now required to supplement enteral nutrition when the latter is not able to provide the full nutritional requirement. We report the changes in body composition, plasma proteins, and resting energy expenditure (REE) during 14 days of parenteral nutrition (PN) in patients with acute pancreatitis.

METHODS

Total body protein (TBP), total body water (TBW), and total body fat (TBF) were measured by neutron activation analysis and tritium dilution before and after PN. Fat-free mass (FFM) was derived as the difference between body weight and TBF. REE was measured by indirect calorimetry. Protein index (PI) was the ratio of measured TBP to TBP, calculated from healthy volunteers.

RESULTS

Fifteen patients with acute pancreatitis (11 men, 4 women; median age 56, range 30-80 years) were studied. Thirteen patients had severe acute pancreatitis (Atlanta criteria), and 1 patient died. The gains in body weight (1.05 +/- 0.77 kg), TBW (0.49 +/- 0.87 kg), TBP (0.20 +/- 0.22 kg), FFM (0.73 +/- 0.92 kg), TBF (0.32 +/- 0.95 kg), and REE (146 +/- 90 kcal/d) after 14 days of PN were not significant. Plasma prealbumin increased by 46.5% (p = .020). When patients (n = 6) with intercurrent sepsis and recent surgery were excluded, there were significant increases in TBP (0.65 +/- 0.17 kg, p = .005) and PI (0.060 +/- 0.011, p = .0006).

CONCLUSIONS

Body composition is preserved in acute pancreatitis during 14 days of PN. In patients without sepsis or recent surgery, PN is able to significantly increase body protein stores.

Diminished ERK 1/2 and p38 MAPK phosphorylation in skeletal muscle during sepsis

Sepsis induces weight loss and the loss of skeletal muscle proteins, in part through an inhibition of protein synthesis secondary to an inhibition of the key steps controlling mRNA translation in skeletal muscle. We have previously shown that sepsis decreases the phosphorylation of eIF4E. The present study examines the phosphorylation of Erk 1/2 MAPK and p38 MAPK in skeletal muscle of rats with a chronic (5-day) intra-abdominal septic abscess. Mnk1 catalyzes the phosphorylation of eIF4E, and Mnk1 is activated by phosphorylation via Erk1/2 MAPK and p38 MAPK. Sepsis resulted in a significant decrease in the steady-state phosphorylation of Erk 1/2 and p38 MAPKs compared with sterile inflammation. To examine the mediators responsible for decreased phosphorylation of Erk 1/2 and p38 MAPKs, rats were treated with TNF binding protein (TNFbp) or infused for 24 h with TNF. Treatment of septic rats with TNFbp resulted in an increase in the phosphorylation of both Erk 1/2 and p38 MAPKs in skeletal muscle. This was associated with enhanced phosphorylation of eIF4E. In contrast, constant intravenous infusion of TNF-alpha for 24 h resulted in a complete inhibition of p38 MAPK phosphorylation while Erk 1/2 MAPK phosphorylation was increased. The net effect was a modest increase in eIF4E phosphorylation. The results suggest altered regulation of Erk 1/2 and p38 MAPK signal translation pathways by endogenously produced TNF, or some compound dependent on TNF may modulate, in part, the phosphorylation state of eIF4E in skeletal muscle during sepsis.

Surgical treatments of infants with necrotizing enterocolitis

With the improvements in neonatal intensive care, necrotizing enterocolitis (NEC) has become the most common gastrointestinal emergency amongst infants in neonatal intensive care units. The incidence of NEC varies between 1 and 8% of neonatal intensive care unit admissions and the disease has a mortality rate between 20 and 40%. There are a number of surgical options available to the paediatric surgeon depending on the clinical condition of the infant and the extent of the disease. However owing to a paucity of prospective data in this field and a lack of randomized controlled trials there is little consensus as to which is the most appropriate. Primary peritoneal drainage has become very popular in North America and Europe for the treatment of perforated NEC in very low-birthweight infants. It is a useful manoeuvre in the resuscitation of critically ill infants and in some of these infants, further operation may be avoided completely by inserting a peritoneal drain. Others however remain too unwell to undergo laparotomy and may die. Two randomized controlled trials are currently underway to determine the real benefit of peritoneal drainage. Laparotomy in very small neonates has become safer with improvements in anaesthesia and intensive care management. Resection and primary anastomosis has been proposed as a valid treatment modality in neonates with both focal and multifocal disease. The advantage of resection and primary anastomosis over stoma formation is still controversial. Different surgical techniques such as diverting jejunostomy or 'clip and drop' have been described to deal with extensive disease and avoid massive small bowel resection. Prospective studies and randomized controlled trials are needed to define the best operative treatment for neonates with severe NEC.

Energy balance in critical illness

Energy balance is the difference between energy consumed and total energy expended. Over a given period of time it expresses how much the body stores of fat, carbohydrate and protein will change. For the critically-ill patient, who characteristically exhibits raised energy expenditure and proteolysis of skeletal muscle, energy balance information is valuable because underfeeding or overfeeding may compromise recovery. However, there are formidable difficulties in measuring energy balance in these patients. While energy intake can be accurately recorded in the intensive care setting, the measurement of total energy expenditure is problematic. Widely used approaches, such as direct calorimetry or doubly-labelled water, are not applicable to the critically ill patient. Energy balance was determined over periods of 5-10 d in patients in intensive care by measuring changes in the fat, protein and carbohydrate stores of the body. Changes in total body fat were positively correlated with energy balance over the 5 d study periods in patients with severe sepsis (n 24, r 0.56, P = 0.004) or major trauma (n 24, r 0.70, P < 0.0001). Fat oxidation occurred in patients whose energy intake was insufficient to achieve energy balance. Changes in body protein were independent of energy balance. These results are consistent with those of other researchers who have estimated total energy requirements from measurements of O2 consumption and CO2 production. In critically-ill patients achievement of positive non-protein energy balance or total energy balance does not prevent negative N balance. Nutritional therapy for these patients may in the future focus on glycaemic control with insulin and specialised supplements rather than on energy balance per se.

L-alanyl-L-glutamine-supplemented parenteral nutrition improves infectious morbidity in secondary peritonitis

BACKGROUND & AIMS

A growing number of randomized clinical trials suggest that glutamine (Gln) supplementation may be beneficial in a selected group of patients and conditions. However, the effects of Gln-enriched total parenteral nutrition (TPN) on recovery from acute intra-abdominal infection have not been thoroughly investigated. Therefore, the aim of this study was to investigate whether the provision of Gln-enriched TPN after surgical and medical treatment of secondary peritonitis improves infectious morbidity.

METHODS

Thirty-three patients with secondary peritonitis were randomly assigned to receive either standard (n=16) TPN or L-alanyl-L-glutamine-supplemented (n=17) TPN, after medical and surgical treatment of the infectious focus. The two TPN formulae were isonitrogenous and isocaloric, which commenced the morning after surgery and ran continuously for 10 consecutive days. The control group received standard TPN, while the treatment group was given L-alanyl-L-glutamine, 0.40 g/kg/d (Dipeptiven, Fresenius Kabi, Bad Homburg, Germany). Infectious morbidity, nitrogen balance, leukocytes, lymphocytes, subpopulations CD(4) and CD(8), Immunoglobulin A (IgA), total proteins, albumin, hospital and intensive care unit (ICU) stays, and mortality were evaluated. Statistical analysis included one-way ANOVA, the unpaired Student's t-test, the Mann-Whitney U-test, chi(2) test, or Fisher's exact test.

RESULTS

Patients in both groups were comparable prior to the operation. Nitrogen balance and the levels of albumin and IgA were significantly better than those in the control group. Also, a significant reduction in the infectious morbidity was found in the Gln-treated group. Lymphocyte counts as well as subpopulations CD(4) and CD(8), and proteins showed a propensity to improvement and a tendency to reduced rates of mortality were observed when comparing the groups. Hospital and ICU stays were similar.

CONCLUSION

L-alanyl-L-glutamine-supplemented TPN improved the infectious morbidity of patients with secondary peritonitis. Gln supplementation to parenteral nutrition may be an alternative for enhancing host defenses and improving infectious morbidity.

Body temperature and heat production in suckling rat endotoxaemia: beneficial effects of glutamine

BACKGROUND/PURPOSE

Sepsis is an important cause of neonatal mortality. The aim of the study was to investigate the metabolism of endotoxic neonatal rats and the potential beneficial effect of glutamine.

METHODS

Suckling rats received intraperitoneal saline (control; C), endotoxin (300 microg/g LPS; E), saline+glutamine (2 mmol/g; CG), endotoxin+glutamine (EG), saline+leucine (2 mmol/g; CL) or endotoxin+leucine (EL). Sepsis score (0-8) and rectal temperature were monitored. Hypothermia was defined as rectal temperature less than 32 degrees C. Oxygen consumption (VO2, mL/kg/h), a determinant of heat production, was measured by indirect calorimetry. Data (mean +/- SEM) were compared by analysis of variance (ANOVA), paired t test or Fisher's Exact test.

RESULTS

Endotoxic (E) rats had significantly lower VO2 than C rats from 90 minutes postinjection to the end of the experiment, 210 minutes (VO2 from 150 to 210 minutes: C 671 +/- 45; E 429 +/- 36, P <.0004; n = 8; paired t test). VO2 of CL or CG rats was elevated between 90 and 210 minutes compared with control, but significantly (P <.01) only in the L group (C 706 +/- 31; CG 871 +/- 63; CL 984 +/- 31; n = 7-9, ANOVA). VO2 was significantly higher (P <.05) in EG rats than E rats (E 460 +/- 29; EG 654 +/- 68; n = 9-10). In the EL group, VO2 was raised but was not significantly different from E (E 460 +/- 29; EL 637 +/- 52; n = 8-10). EG rats were significantly less hypothermic between 90 and 210 minutes (58 of 132 measurements) compared with E (95 of 147; P =.0007, Fisher's Exact test), whereas the EL group were similarly hypothermic (74 of 120) to E (P =.7). Sepsis score was significantly lower in the EG group than both E and EL groups (E 4.9 +/- 0.3; EG 3.6 +/- 0.3; EL 5.0 +/- 0.3; n = 40; P <.01; ANOVA).

CONCLUSIONS

Neonatal endotoxaemia lowers VO2, heat production, and body temperature. Glutamine and leucine both cause nutrient-induced thermogenesis in control animals and restore VO2 of endotoxic animals. Glutamine additionally increases rectal temperature, reduces incidence of hypothermia, and improves clinical signs of endotoxic rats. This suggests that glutamine may be beneficial for nutrition in neonatal sepsis.

Effect of sepsis syndrome on neonatal oxygen consumption and energy expenditure

OBJECTIVE

To evaluate oxygen consumption (VO2), carbon dioxide production, and energy expenditure (EE) in full-term neonates with early-onset neonatal septicemia daily for 7 days beginning at the day of clinical diagnosis of sepsis.

METHODS

A total of 17 spontaneously breathing full-term neonates, 10 with clinical signs of sepsis and 7 healthy neonates (control group), were enrolled in the study. Age at first study day was 3 +/- 0.9 days in both groups. Sepsis syndrome was defined as a systemic response to a bacterial infection with clinical signs of infection, elevated values of interleukins 6 and 8 and C-reactive protein, and abnormal white blood cell count and positive blood cultures (9 group B streptococci, 1 Escherichia coli). Measurements of VO2 and carbon dioxide production were performed daily for 7 days by means of indirect calorimetry.

RESULTS

In the septic infants, VO2 and EE were increased by about 20% at days 1 to 3 and by 15% at day 4 when compared with the controls. From days 1 to 3, EE averaged 57 +/- 3 kcal/kg/d in the septic neonates and 47 +/- 2 kcal/kg/d in the controls. At day 4, EE was 55 +/- 2 and 47 +/- 2 kcal/kg/d, respectively. Energy intake was about the same in both groups, whereas weight gain during the 7 study days was significantly lower in the sick patients than in the control group (19 +/- 2 g/d vs 33 +/- 9 g/d and 5.4 +/- 0.5 g/kg/d vs 9.4 +/- 2.6 g/kg/d, respectively). Increased EE was associated with increased heart rate (126 +/- 4 vs 112 +/- 4 min(-1) at day 1) and respiratory rate (56 +/- 6 vs 40 +/- 4 min(-1) at day 1). There were no differences in rectal temperature (37.3 +/- 0.4 degrees C vs 37.4 +/- 0.2 degrees C), skin temperature (36.5 +/- 0.4 degrees C vs 36.6 +/- 0.3 degrees C), and oxygen saturation (96 +/- 3% vs 96 +/- 3%) between the 2 groups.

CONCLUSIONS

Neonates with sepsis syndrome have elevated VO2 and EE values that could explain impaired growth during the illness period and may make the infants vulnerable to insufficient calorie supply during the acute phase of septic disease.

Distinguishing starvation from cachexia

The poor response to hypercaloric feeding in ill adults may be caused by failure to distinguish cachexia from starvation (Table 1). The chief difference between starvation and cachexia is that refeeding reverses starvation but is less effective for cachexia. The ineffectiveness of refeeding in treating cachexia may explain some of the poor results from direct nutritional interventions in clinical trials. Simple starvation should respond to voluntary or involuntary hypercaloric feedings. The failure to demonstrate a more positive response may be caused by underlying cachexic states.

Long-term stable cultures of rat hepatocytes: an in vitro model to study acute and chronic hepatic inflammation

Engineered tissues provide an opportunity to investigate important physiological processes difficult to study in whole perfused organs and animal models. For example, a hepatocyte culture model consisting of rat hepatocytes cultured in a collagen sandwich configuration, which exhibits stable differentiated liver-specific functions, may be useful to investigate liver pathophysiology. To investigate systemic inflammation-related hepatic failure, we chronically exposed hepatocytes to the inflammatory mediators interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) for up to 4 weeks. IL-6 (2.5 ng/mL) transiently suppressed albumin (-90%) and chronically increased fibrinogen (+6-fold) production. IL-6 inhibited urea synthesis at 2.5 ng/mL and stimulated it at 0.025 ng/mL. IL-1beta (10 ng/mL) inhibited albumin (-90%), urea (-40 to 50%), and IL-6-stimulated fibrinogen (-90%) secretion. The inhibitory effect of IL-1beta on urea secretion was dose-dependent. Furthermore, IL-1beta transiently stimulated nitric oxide (NO) synthesis; however, NO did not mediate the effect of IL-1beta on albumin and fibrinogen production, and played a minor role in IL-1beta-mediated urea synthesis suppression. In conclusion, IL-1beta and IL-6 exert, via a direct effect on hepatocytes, long-term inhibitory effects on hepatic functions that are potentially important for the survival of the host, which may contribute to hepatic dysfunction in prolonged inflammatory states.

Metabolism and nutritional support in the surgical neonate

Various factors can influence the metabolism of surgical neonates. These include prematurity, operative stress, critical illness, and sepsis. The nutritional management of surgical infants with congenital or acquired intestinal abnormalities has improved after the introduction of parenteral nutrition. This article is focused on the energy and protein metabolism of surgical neonates with particular reference to the metabolic response to operative trauma and sepsis. The metabolic utilization of intravenous nutrients also is discussed. The metabolic response to operative trauma is different between neonates and adults. Infants have high rates of protein turnover and are avid retainers of nitrogen. Energy expenditure increases only transiently (4 to 6 hours) after major surgery in neonates. Protein turnover and catabolism seems not to be affected by major operative procedures in neonates. In neonates on parenteral nutrition, carbohydrate and fat have an equivalent effect on protein metabolism. The main determinants of fat utilization are carbohydrate intake and resting energy expenditure. Parenteral nutrition in surgical neonates is associated with increased production of oxygen-free radicals. This seems to be related to intravenous fat administration. Promoting fat utilization by reducing the carbohydrate to fat ratio in the intravenous diet reduces free radical activity to a similar extent as fat exclusion. Glutamine appears to be safe for use in neonates and infants and is "conditionally essential" in very-low birth weight infants and in septic neonates. Enteral glutamine supplementation in very-low birth weight infants reduces the risk of sepsis. The metabolism of surgical neonates is affected by operative trauma, critical illness, and sepsis. Nutritional support in surgical neonates has a profound impact on outcome. Exogenous glutamine can modulate immune, metabolic, and inflammatory responses. Further investigations are needed to clarify the clinical benefit of parenteral or enteral glutamine administration in surgical neonates.

Nutritional support

Despite the increasing obesity of the American population, many chronically ill patients are malnourished. When this malnutrition is combined with the hypermetabolic response and protein catabolism of an acute event, such as an operation, nutritional support becomes an important facet for optimal critical care. This chapter reviews the basic tenants of nutritional support with special emphasis on patients with pulmonary compromise. Important aspects of caloric and protein support are discussed and enteral nutrition is emphasized because of its numerous advantages and documented improvement in outcome.

Clinical review: Intensive care follow-up--what has it told us?

The majority of intensive care practitioners, until comparatively recently, was content to discharge surviving patients to the care of referring primary specialty colleagues who would undertake subsequent inpatient and outpatient care. With the exception of mortality statistics from clinical studies, the practitioners were thus denied the opportunity of understanding the full impact of critical illness on a patient and their family. The concept of the intensive care follow-up clinic has developed more recently, and is run commonly on multidisciplinary lines. These clinics serve a number of purposes, but importantly have drawn attention to broader patient-centred outcomes after intensive care. Investigators are just beginning to identify, and in some cases quantify, the postdischarge burden on patient and family; additional useful data have also come from follow-up of specific disease states. The purpose of the present review is to highlight some of the important issues that impact on recovery from critical illness towards an acceptable quality of postdischarge life. We have concentrated on the adult literature, and specifically on studies that inform us about the more general effects of critical illness. Head and spinal injury are thus largely ignored, as the effects of the primary injury overwhelm the effects of 'general' critical illness.

Metabolic response and parenteral nutrition in trauma, sepsis, and burns

Trauma, sepsis, and burns cause abnormal manifestations in the body. These manifestations can cause alterations in body metabolism, which complicates nutritional management. Goals of nutrition support with assessment modifications for a constantly changing population are reviewed. Patients in such stress states as burns, trauma, and sepsis many times need altered nutrition. This article outlines guidelines for total parenteral formula modification and monitoring, and discusses other complications such as drug interactions with parenteral formulas.

Influence of parenteral nutrition on postoperative recovery in an experimental model of peritonitis

BACKGROUND AND AIMS

There seems to be no clear-cut indications for routine TPN support after major elective surgery. The present study was designed to investigate whether TPN could improve the results of standard surgical care for acute peritonitis (laparotomy plus antibiotics).

ANIMALS AND METHODS

Peritonitis was induced in 48 New Zealand rabbits (day -2). On day 0, appendectomy and peritoneal lavage were performed, ceftriaxone (250 mg, i.m./24 h.) was started and animals were randomly assigned to receive regular fluids (RF), glucose-based TPN (G-TPN) or isocaloric fat-based TPN (F-TPN) for 6 days.

MAIN OUTCOME MEASURES

Balance studies (days 1-3), s-albumin, thyroid hormones and urinary catecholamines were determined at various points of the experiment. At postmortem, wound infection, residual intra-abdominal infection and laparotomy wound breaking strength were recorded.

RESULTS

Peritonitis produced a fall in weight, s-albumin and T3. At day 6, weight-loss was more pronounced in RF than in G-TPN or F-TPN (-7 vs 1.5 vs -1.2%;P=0.0001) but s-albumin and T3 concentrations were similar. Diuresis (377 vs 268 vs 269 mL/3 days; P=0.01) was higher and water balance lower (373 vs 511 vs 480 mL/3 days; P=0.01) in Group RF. Although the differences were not statistically significant (P<0.2), persistent infection and wound breaking strength were slightly worse in the pooled TPN groups compared with the RF group (19 vs 6% and 542 vs 701 g, respectively).

CONCLUSIONS

TPN failed to improve relevant biochemical markers and clinical outcome after laparotomy for peritonitis.

The effect of glutamine supplementation in patients following elective surgery and accidental injury

The metabolic response to injury, whether a controlled elective surgical procedure or an accidental injury, is characterized by the breakdown of skeletal muscle protein and the translocation of the amino acids to visceral organs and the wound. At these sites, the substrate serves to enhance host defenses, and support vital organ function and wound repair. Glutamine (GLN) plays a major role in these processes, accounting for approximately one third of the translocated nitrogen. From available data, GLN-supplemented intravenous nutrition in patients undergoing elective surgery improves nitrogen balance, helps correct the decreased GLN concentration found in the free intracellular skeletal muscle amino acid pool and enhances net protein synthesis (particularly in skeletal muscle). Six randomized blind trials (two multicentered investigations) reported a decreased length in hospital stay in postoperative patients receiving GLN supplementation. After blunt trauma, GLN supplementation increased plasma concentrations, attenuated the immunosuppression commonly observed and decreased the rate of infection. Patients with burn injury have low GLN plasma and intramuscular concentrations; turnover and synthesis rate are accelerated, yet apparently inadequate to support normal concentrations. These data suggest that GLN supplementation has important effects in catabolic surgical patients, but the exact mechanisms to explain these events remain unknown, and more research is required to explain the apparent benefits of dietary GLN.

Body water compartment measurements: a comparison of bioelectrical impedance analysis with tritium and sodium bromide dilution techniques

BACKGROUND AND AIMS

This study was undertaken to assess the comparability of body water compartment estimates in healthy volunteers using single and dual frequency bioelectrical impedance analysis (BIA) with established reference methods of tritium and NaBr dilution.

METHODS

Total body water (TBW) was estimated in 10 healthy volunteers using single frequency (50 kHz) BIA (Bodystat 1500), dual frequency (5 and 200 kHz) BIA (Bodystat Dualscan 2005) and tritium dilution. Extracellular water (ECW) was measured with dual frequency BIA and NaBr dilution. BIA was performed using distal tetrapolar electrodes in the supine position. Venous blood was sampled for measurement of background concentrations of tritium and NaBr using a beta counter and high performance liquid chromatography respectively. 10 ml tritiated water (3.7 MBq) and 50 ml 5% NaBr solution were then injected intravenously and blood samples taken from the opposite arm every 45 min for 4.5 h for estimation of concentrations of tritium and NaBr.

RESULTS

There was good correlation (r(2)=0.76) between estimates of ECW using dual frequency BIA and NaBr dilution, with the former overestimating ECW by approximately 1 L. However, this difference varied systematically with body weight. Although TBW measurements obtained by single and dual frequency BIA correlated well with estimates using tritium dilution (r(2)=0.96 and 0.95 respectively), single frequency BIA underestimated TBW by approximately 1 L and dual frequency BIA by approximately 5 L compared to tritium dilution.

CONCLUSION

TBW measurements obtained using the single frequency BIA device were more accurate than those obtained using the dual frequency BIA device. Dual frequency BIA provided a reasonably accurate estimate of ECW.

Sequential changes in the metabolic response to orthotopic liver transplantation during the first year after surgery

OBJECTIVE

To quantify the sequential changes in the metabolic response occurring in patients with end-stage liver disease after orthotopic liver transplantation (OLT).

SUMMARY BACKGROUND DATA

Detailed quantification of the changes in energy expenditure, body composition, and physiologic function that occur in patients after OLT has not been performed. Understanding these changes is essential for the optimal management of these patients.

METHODS

Fourteen patients who underwent OLT for end-stage liver disease had measurements of resting energy expenditure, body composition, and physiologic function immediately before surgery and 5, 10, 15, 30, 90, 180, and 360 days later.

RESULTS

Resting energy expenditure was significantly elevated after surgery (24% above predicted), peaking around day 10 after OLT, when it averaged 42% above predicted. A significant degree of hypermetabolism was still present at 6 months, but at 12 months measured resting energy expenditure was close to predicted values. Before surgery, measured total body protein was 82% of estimated preillness total body protein. During the first 10 days after OLT, a further 1.0 kg (10%) of total body protein was lost, mostly from skeletal muscle. Only 54% of this loss was restored by 12 months. Significant overhydration of the fat-free body was seen before OLT, and it was still present 12 months later. Although significant losses of body fat and bone mineral occurred during the early postoperative period, only body fat stores were restored at 12 months. Both subjective fatigue score and voluntary hand grip strength improved rapidly after OLT to exceed preoperative levels at 3 months. At 12 months grip strength was close to values predicted for these patients when well. Respiratory muscle strength improved less markedly and was significantly lower than predicted normal levels at 12 months.

CONCLUSIONS

Before surgery, these patients were significantly protein-depleted, overhydrated, and hypermetabolic. After surgery, the period of hypermetabolism was prolonged, restoration of body protein stores was gradual and incomplete, and respiratory muscle strength failed to reach expected normal values. Our measurements indicate that OLT does not normalize body composition and function and imply that a continuing metabolic stress persists for at least 12 months after surgery.

Beyond body mass index

Body mass index (BMI) is the cornerstone of the current classification system for obesity and its advantages are widely exploited across disciplines ranging from international surveillance to individual patient assessment. However, like all anthropometric measurements, it is only a surrogate measure of body fatness. Obesity is defined as an excess accumulation of body fat, and it is the amount of this excess fat that correlates with ill-health. We propose therefore that much greater attention should be paid to the development of databases and standards based on the direct measurement of body fat in populations, rather than on surrogate measures. In support of this argument we illustrate a wide range of conditions in which surrogate anthropometric measures (especially BMI) provide misleading information about body fat content. These include: infancy and childhood; ageing; racial differences; athletes; military and civil forces personnel; weight loss with and without exercise; physical training; and special clinical circumstances. We argue that BMI continues to serve well for many purposes, but that the time is now right to initiate a gradual evolution beyond BMI towards standards based on actual measurements of body fat mass.

Effect of pentoxifylline on nitrogen balance and 3-methylhistidine excretion in parenterally fed endotoxemic rats

Pentoxifylline interrupts early gene activation for tumor necrosis factor, interleukin-1, and interleukin-6 production and improves survival from experimental sepsis. These effects can alter nitrogen loss during critical illness. To determine the dose-dependent influence of pentoxifylline on nitrogen loss, 44 male Sprague-Dawley rats (220 to 265 g) were randomized to receive parenteral nutrition only (PN), PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide (LPS) at 9 mg x kg(-1) x d(-1), or PN plus LPS plus a continuous infusion of pentoxifylline at either 25 (PEN25) or 100 mg x kg(-1) x d(-1) (PEN100) for 48 h. Before randomization, all animals underwent intravenous cannulation and 40 h of PN adaptation. All animals received isocaloric, isonitrogenous PN (160 kcal x kg(-1) x d(-1) and 1.0 gN x kg(-1) x d(-1)) and were kept nil per os except for water ad libitum. Administration of LPS significantly worsened nitrogen balance for all three groups compared with PN control; however, pentoxifylline only modestly improved nitrogen balance compared with LPS (206 +/- 255, -497 +/- 331, -332 +/- 329, and -310 +/- 383 mg/48hr for the PN, LPS, PEN25, and PEN100 groups, respectively; P < 0.001). Pentoxifylline did not significantly change 3-methylhistidine urinary excretion compared with LPS (573 +/- 180, 705 +/- 156, 780 +/- 326, and 683 +/- 266 microg/48 h for the PN, LPS, PEN25, and PEN100 groups, respectively, P not significant). Pentoxifylline, given in therapeutic doses after an endotoxin challenge, modestly, but not significantly, improved nitrogen balance. Urinary 3-methylhistidine excretion was not influenced by pentoxifylline. A dose-dependent effect by pentoxifylline on these markers was not evident.

Energy metabolism of infants and children with systemic inflammatory response syndrome and sepsis

OBJECTIVE

To evaluate whether critically ill children with systemic inflammatory response syndrome (SIRS) or sepsis have altered resting energy expenditure (REE) and substrate utilization.

SUMMARY BACKGROUND DATA

Studies in adults with sepsis have shown increased energy expenditure and mobilization of endogenous fat. In infants and children, energy metabolism and substrate utilization during sepsis have not been characterized.

METHODS

Metabolic studies were performed in 21 critically ill children with SIRS or sepsis. Twenty-one stable control children, matched for weight, were also studied. Seven patients required inotropic support and 17 received mechanical ventilation. Fifteen patients with SIRS had evidence of bacterial, fungal, or viral infection and were considered septic. Respiratory gas exchange was measured by computerized indirect calorimetry for 1 to 2 hours continuously.

RESULTS

The REE of patients with SIRS or sepsis was not different from that of controls. Similarly, there were no differences in carbon dioxide production and oxygen consumption. Resting energy metabolism was not different between patients with SIRS and patients with sepsis. In addition, the presence of low platelet count or inotropic support did not affect resting energy metabolism. The median respiratory quotient of patients with SIRS or sepsis was 0.88 (range 0.75-1.12), indicating mixed utilization of fat and carbohydrate; this was not significantly different from that of controls. The Pediatric Risk of Mortality Score was not significantly correlated with REE or respiratory quotient.

CONCLUSIONS

The energy requirements of children with SIRS or sepsis are not increased. Their resting metabolism is based on both carbohydrate and fat utilization. The authors speculate that these children divert the energy for growth into recovery processes.

Effect of lipopolysaccharide and cytokines on oxidative metabolism in neonatal rat hepatocytes

BACKGROUND/PURPOSE

Lipopolysaccharide (LPS) and cytokines produced during neonatal sepsis trigger free radical production, which eventually results in inhibition of liver metabolism. Studies in adults have indicated a hypermetabolic response to sepsis; however, evidence for a hypermetabolic response in neonates is equivocal. This study was carried out to determine whether LPS and cytokines can cause liver hypermetabolism in neonates.

METHODS

The initial bacterial insult and cytokine cascade were mimicked by the addition of lipopolysaccharide (Escherichia coli 055:B5), tumour necrosis factor (TNF-alpha), and interleukin-6 (IL6) during the isolation of hepatocytes by collagenase digestion from 11- to 13-day-old Wistar rats. Hepatocyte oxygen consumption was measured polarographically with cells respiring on palmitate (0.5 mmol/L). Myxothiazol, a specific inhibitor of mitochondrial respiration, was used to distinguish extra- and intramitochondrial oxygen consumption. Morphologic changes were assessed by electron microscopy.

RESULTS

The addition of LPS, TNF-alpha and IL6 during hepatocyte isolation resulted in a 10% decrease in cell yield (P <.05) compared with untreated controls; however, cell viability was unchanged (n = 31). Both total and extramitochondrial oxygen consumption were significantly greater in treated cells compared with untreated controls (P <.05, Student's t test). Electron microscopy indicated that LPS, TNF-alpha, and IL6 did not cause ultrastructural changes to hepatocytes.

CONCLUSIONS

The increase in oxygen consumption was predominantly extramitochondrial and likely to be caused by increased oxygen requirement for cytosolic detoxification and repair purposes. This study shows that liver hypermetabolism metabolism can occur in response to LPS and cytokines. However, during in vivo neonatal sepsis, additional free radical damage may blunt this hypermetabolic response.

Determinants of skeletal muscle catabolism after severe burn

OBJECTIVE

To determine which patient factors affect the degree of catabolism after severe burn.

SUMMARY BACKGROUND DATA

Catabolism is associated with severe burn and leads to erosion of lean mass, impaired wound healing, and delayed rehabilitation.

METHODS

From 1996 to 1999, 151 stable-isotope protein kinetic studies were performed in 102 pediatric and 21 adult subjects burned over 20-99. 5% of their total body surface area (TBSA). Patient demographics, burn characteristics, and hospital course variables were correlated with the net balance of skeletal muscle protein synthesis and breakdown across the leg. Data were analyzed sequentially and cumulatively through univariate and cross-sectional multiple regression.

RESULTS

Increasing age, weight, and delay in definitive surgical treatment predict increased catabolism (P < .05). Body surface area burned increased catabolism until 40% TBSA was reached; catabolism did not consistently increase thereafter. Resting energy expenditure and sepsis were also strong predictors of net protein catabolism. Among factors that did not significantly correlate were burn type, pneumonia, wound contamination, and time after burn. From these results, the authors also infer that gross muscle mass correlates independently with protein wasting after burn.

CONCLUSIONS

Heavier, more muscular subjects, and subjects whose definitive surgical treatment is delayed are at the greatest risk for excess catabolism after burn. Sepsis and excessive hypermetabolism are also associated with protein catabolism.

Phase angle from bioelectrical impedance analysis remains an independent predictive marker in HIV-infected patients in the era of highly active antiretroviral treatment

BACKGROUND

Highly active antiretroviral treatment (HAART) reduces the risk of wasting in HIV infection and may alter the prognostic weight of wasting. The phase angle from bioelectrical impedance analysis (BIA) can be interpreted as a surrogate marker for the catabolic reaction to chronic HIV infection and opportunistic disease.

OBJECTIVE

Our objective was to assess the prognostic ability of the phase angle in HIV-infected patients in the era of HAART.

DESIGN

Two cross-sectional observation studies were conducted in 1996 and 1997 at a German university outpatient HIV clinic. In the 1996 and 1997 cohorts, HAART was prescribed to 17 of 212 and 168 of 257 patients at baseline and to 179 of 212 and 234 of 257 patients during observation, respectively. Whole-body BIA was assessed at 50 KHz. Time to clinical progression and survival were calculated by using Cox proportional hazard models with time-dependent covariates. Median observation times were 1000 and 515 d for the 1996 and 1997 cohorts, respectively.

RESULTS

Higher phase angle was associated with a lower relative mortality risk, adjusted for viral load and CD4(+) cell count, of 0.49 (95% CI: 0.30, 0.81) per degree in 1996 and of 0.33 (95% CI: 0.18, 0.61) in 1997. The influence of phase angle on time to clinical progression, adjusted for viral load and CD4(+) cell count, was not significant in 1996 but the relative risk was 0.58 (0.36, 0.83) in 1997.

CONCLUSION

Despite the favorable effects of HAART on the nutritional status of HIV-infected persons, low phase angle remains an independent adverse prognostic marker of clinical progression and survival.

Growth hormone decreases muscle glutamine production and stimulates protein synthesis in hypercatabolic patients

We determined the effects of 24-h recombinant human growth hormone (rhGH) infusion into a femoral artery on leg muscle protein kinetics, amino acid transport, and glutamine metabolism in eight adult hypercatabolic trauma patients. Metabolic pathways were assessed by leg arteriovenous catheterization and muscle biopsies with the use of stable amino acid isotopes. Muscle mRNA levels of selected enzymes were determined by competitive PCR. rhGH infusion significantly accelerated the inward transport rates of phenylalanine and leucine and protein synthesis, whereas the muscle protein degradation rate and cathepsin B and UbB polyubiquitin mRNA levels were not significantly modified by rhGH. rhGH infusion decreased the rate of glutamine de novo synthesis and glutamine precursor availability, total branched-chain amino acid catabolism, and nonprotein glutamate utilization. Thus net glutamine release from muscle into circulation significantly decreased after rhGH administration ( approximately 50%), whereas glutamine synthetase mRNA levels increased after rhGH infusion, possibly to compensate for reduced glutamine precursor availability. We conclude that, after trauma, the anticatabolic action of rhGH is associated with a potentially harmful decrease in muscle glutamine production.

Nutritional support in sepsis: still skeptical?

The immediate metabolic response to a septic challenge is probably adaptive, meaning that nutritional interference, mainly via the parenteral route, during this early phase of instability can do more harm than good. During the later phases, a gradual increase in enteral nutrition, at the expense of parenteral nutrition, combined with the administration of nutraceuticals such as glutamine and omega-3 fatty acids, can counteract wasting and modulate the complex inflammatory response and immunosuppression associated with sepsis. In these times of scarce resources, there is an urgent need to clearly document the efficacy of immuno/pharmaconutrients, individually and in combination, enterally or parenterally, before proposing them for routine management of septic patients in the intensive care unit.

Protein-sparing effect in skeletal muscle of growth hormone treatment in critically ill patients

OBJECTIVE

To investigate the effect of growth hormone (GH) treatment on skeletal muscle protein catabolism in patients with multiple organ failure in the intensive care unit (ICU).

SUMMARY BACKGROUND DATA

Skeletal muscle depletion affects the incidence of complications and the length of hospital stay. A protein-sparing effect of GH treatment in skeletal muscle of long-term ICU patients was hypothesized.

METHODS

Twenty critically ill ICU patients were randomized to treatment with GH (0.3 U/kg/day) or as controls. Percutaneous muscle biopsy samples were taken before and after a 5-day treatment period starting on day 3 to 42 of the patient's ICU stay. Protein content, protein synthesis, water, nucleic acids, and free amino acids in muscle were analyzed.

RESULTS

The protein content decreased by 8% +/- 11% in the control patients, with no significant change in the GH group. The fractional synthesis rate of muscle proteins increased in the GH group by 33% +/- 48%, and muscle free glutamine increased by 207% +/- 327% in the GH group. Total intramuscular water increased by 12% +/- 14% in the control group as a result of an increase in extracellular water of 67% +/- 86%; these increases were not seen in the GH group. In contrast, the intracellular water increased by 6% +/- 8% in the GH group.

CONCLUSION

Treatment with GH for 5 days in patients with multiple organ failure stimulated muscle protein synthesis, increased muscle free glutamine, and increased intracellular muscle water.

Fever and sepsis during neutropenia are associated with expansion of extracellular and loss of intracellular water

BACKGROUND AND AIMS

Shifts from intracellular to extracellular water are features of a catabolic reaction to sepsis. Bedside assessment of fluid shifts was carried out in neutropenic patients at high risk of systemic infection.

METHODS

Multifrequency bioelectrical impedance analysis was performed in 41 patients with leukemia or high-malignant lymphoma and chemotherapy-induced neutropenia.

RESULTS

Hydration was stable during afebrile periods except for transient intra- and extracellular dehydration after chemotherapy. The risk of over-hydration and dehydration increased 3-fold during fever. Over-hydration was more severe when occurring during fever. Extracellular water was highly variable and tended to increase, and intracellular water was slowly depleted. During sepsis, these alterations were enhanced. Changes in hydration status did not predict subsequent progression to sepsis because it developed more slowly than other symptoms of infection.

CONCLUSIONS

Extracellular over-hydration and intracellular dehydration are observed in febrile infection in neutropenia, similar to severe sepsis. If the technical limits of bioelectrical impedance are taken into account, this method may be useful for non-invasive monitoring of these features of metabolic stress.

Changes in weight, fluid balance and serum albumin in patients referred for nutritional support

BACKGROUND AND AIMS

Starvation and injury impair the excretion of an excess sodium and water load, resulting in oedema and hypoalbuminaemia, which may have adverse effects on gastrointestinal physiology. We have retrospectively assessed clinical signs and fluid balance in 44 adult patients referred for nutritional support for >== 10 days.

METHODS

Clinical evidence of oedema was noted. Oedematous patients were managed with a low sodium (0-50 mmol/day), low volume (2 l/day) feed. Some also received albumin and a diuretic. Body weight was recorded daily and serum albumin three times weekly. The lowest recorded weight during nutritional support and the weight at the time of discharge were correlated with serum albumin concentration.

RESULTS

The 21 patients with oedema had acute surgical conditions and complications such as sepsis while the 23 non-oedematous patients had chronic conditions with gradual nutritional depletion. During nutritional support the mean (SEM) weight in kg of the oedematous patients fell from 79.3 (2.9) to 69.2 (3.2) (P>> 0.00001) and subsequently rose to 70.1 (3.2) (P= 0.005). Corresponding values for the non-oedematous patients were 61.4 (4.0), 60.2 (3.9) (P>> 0.05) and 61.2 (3.7) (P= 0.002) respectively. Weight reduction reflected negative salt and water balance and correlated with a rise in serum albumin (r = -0.61 for oedematous and r = -0.65 for non-oedematous patients) largely reflecting reversal of previous dilution.

CONCLUSION

These findings have important implications for the salt and water content of perioperative fluid and nutritional prescriptions. They also emphasize the dilutional component of hypoalbuminaemia in these patients.

Metabolic response to neonatal surgery

The energy and protein metabolism of newborn infants differs from that of older individuals. Although energy expenditure and protein turnover are higher in newborn infants than in adults, the metabolic response to surgery in neonates has not been fully characterized. Preliminary studies indicate that metabolic response to operative stress is different in infants and adults: infants have an increased metabolic rate postoperatively for only 6 to 12 hours and do not have increased protein catabolism. More studies are needed in "stressed" newborn infants to further characterize substrate use and the metabolism of single organs.

Deterrents to the successful clinical use of growth factors that enhance protein anabolism

Participants in competitive sports have demonstrated that the use of growth factors and other anabolic agents enhance human performance, yet physicians are slow to adopt this approach in patients who have a disease-related decrease in strength and activity. Growth factors should be thought of as the next major step forward in providing more efficient and effective nutritional support to catabolic or wasted patients. The obstacles to the use of these agents include: the lack of convincing clinical studies; concerns with safety; anabolic effects and the patient's nutritional status; interaction with diet and route of nutrient administration; the training of health professionals to administer growth factors; and cost. The benefits from these agents should be directly translated into improved patient outcome. To achieve this goal, a uniquely educated group of investigators, working with sophisticated representatives from the pharmaceutical industry, must emerge to construct appropriate protocols and determine desirable endpoints to evaluate the true societal benefits of these agents.

Indirect calorimetry: can this technology impact patient outcome?

This review of 23 papers involving indirect calorimetry published over the past 18 months shows how our understanding of the metabolic response to injury has changed, highlights the problems introduced by use of predictive equations and alterations in indirect calorimetry testing protocol, and emphasizes the need to monitor cumulative energy balance by comparing daily caloric intake to energy expenditure.