Alterations in exogenous substrate metabolism in sepsis

Metabolic rates and substrate utilization patterns were evaluated by using a rate cecal ligation and perforation model. Animals that survived for 48 hours after the induction of sepsis were hypermetabolic and responded appropriately to varying exogenous substrate infusions. In contrast, animals that did not survive to 48 hours were premorbidly hypometabolic and failed to adjust their oxidation patterns in response to the exogenous substrate supply. These findings suggest the benefit of individually tailoring the supply of exogenous nutrients in critically ill patients with sepsis and of frequent reassessment of metabolic parameters, including the resting energy expenditure and respiratory quotient.

Central venous access with occlusive superior central venous thrombosis

Thrombotic occlusion of the entire superior central venous system is a rare complication of central venous catheterization. Three patients are presented with complete occlusion of the superior vena cava secondary to prolonged central venous catheterization. Thrombotic occlusion of the superior vena cava precludes central venous access by conventional techniques. Thoracotomy with direct catheterization of the right atrium and inferior vena cava cannulation represent alternative approaches but may be associated with significant morbidity. The present report describes a unique combined angiographic/operative technique designed to obtain central venous access with low morbidity in patients with occlusive thrombosis of the superior central venous system.

The effect of anorexia nervosa on bone morphometry in young women

Changes in bone morphometry during chronic undernutrition were evaluated in 14 young women with anorexia nervosa (mean age +/- SEM = 25.5 +/- 4.4 yrs). Bone morphometry studies using the second metacarpal of the left hand showed significant depression for percent cortical area (p less than 0.05); cortical area (p less than 0.001) and combined cortical thickness (p less than 0.01) as compared to age, sex and race matched controls. A trend (p less than 0.10) was observed in study subjects for reductions in bone width and total area. Using percent cortical area (PCA) as the standard, subjects had mean cortical bone morphometry equivalent to 60-year-old women. Appendicular bone mass is significantly decreased in adults with anorexia nervosa. Anorexia nervosa should be considered in the differential diagnosis of osteopenia in young women, and serves as a model for studying the effects of chronic calorie and mineral malnutrition on bone remodeling at the time of attainment of peak bone mass.

Interval nitrogen excretion and maintenance nitrogen requirements for parenteral nutrition in primates

This paper discusses a regression technique for determining maintenance nitrogen requirements in well-nourished primates (M fascicularis) on total parenteral nutrition. Animals were administered a continuous glucose infusion, and parenteral nitrogen intake was varied at constant time intervals in a random order (from 0 to 1 g nitrogen/kg/day). Interval nitrogen balance (intake minus urinary nitrogen output) was plotted against interval nitrogen intake. The x-intercept was defined as the maintenance nitrogen requirement. First, 24-h intervals were used at a nonprotein caloric intake of 85 kcal/kg/day (approximately 175% of primate resting energy expenditure) and the nutritional adequacy of the estimated requirement evaluated prospectively. Next, 8-h balance intervals were used and the maintenance nitrogen requirements predicted by this abbreviated technique were compared to those obtained using the longer method. Finally, the short-interval technique was repeated at two other levels of continuous glucose infusion (60 kcal/kg/day and 8 kcal/kg/day) and the effect on predicted nitrogen requirement examined. Maintenance parenteral nitrogen requirements for primates may be determined in 48 h using the abbreviated techniques.

Enhanced tumor response to cycle-specific chemotherapy by pulse total parenteral nutrition

Exogenous nutrient administration has been shown to significantly stimulate tumor growth in numerous animal models. The present study was performed to determine if substrate-induced alterations in tumor metabolism could be exploited to potentiate tumor response to cycle-specific chemotherapy. Following subcutaneous mammary tumor (AC-33) implantation, 55 female Lewis/Wistar rats were randomly assigned to one of three nutritional regimens for 48 hr: (1) protein-depleted chow (0.03% protein) ad lib per os, (2) standard rat chow (22.0% protein) ad lib per os, or (3) total parenteral nutrition (TPN; 18.6% dextrose/2.8% amino acids). One-half of the animals in each group received a single dose of methotrexate (5 mg/kg im) while the remaining animals received placebo (saline) injections. At sacrifice, methotrexate-treated animals receiving TPN demonstrated a significantly smaller tumor volume (0.47 +/- 0.44 cm3) compared to animals given either protein depleted chow (1.30 +/- 0.76 cm3) or standard rat chow (1.34 +/- 0.83 cm3) (P less than 0.01). In this animal model, adjuvant TPN was found to significantly potentiate tumor response to cycle-specific chemotherapy with no detectable exacerbation of host toxicity.

A quantitative evaluation of stress associated with indwelling superior vena cava cannulae in rats

"Nonrestraining" superior vena cava (SVC) cannulae are commonly used in rat metabolic studies. The objective of this study was to evaluate the level of stress and metabolic alterations associated with surgical placement and subsequent maintenance and use of an indwelling intravenous cannula as measured by resting energy expenditure (REE), respiratory quotient (RQ), urinary nitrogen excretion, and substrate utilization pattern. Nine rats underwent SVC cannulation and six rats underwent sham operation. Postoperatively, animals were starved for 48 hr and then refed either parenterally or orally for 48 hr. Sham-operated animals adapted appropriately to starvation within 24 hr by decreasing REE 14% and increasing utilization of fat (RQ:0.89----0.78). Hypometabolic adaptation to starvation was delayed in cannulated animals until the second postoperative day, but appropriate alterations in energy substrate utilization were not affected by the presence of cannulae. Cannulae did not affect the metabolic response to oral refeeding with similar increases in REE and similar patterns of substrate utilization in sham-operated and cannulated animals. Animals refed parenterally demonstrated higher REE and apparent fat deposition (RQ greater than 1) consistent with continuous hypercaloric glucose administration. Urinary nitrogen excretion was not affected by the presence of cannulae. Cannula-associated metabolic alterations are minimal and transient and do not preclude detection and quantification of alterations associated with composition or utilization of exogenous substrates.

Energy expenditure in acute trauma to the head with and without barbiturate therapy

The increased energy expenditure associated with severe trauma to the head appears genuine but exhibits wide variation in its magnitude. Patients with severe acute trauma to the head without barbiturate treatment are hypermetabolic with an average energy expenditure 26 per cent over predicted. Barbiturate therapy abolishes this hypermetabolism and decreases energy expenditure to 14 per cent below predicted. In the individual patient, there appears to be a close relationship between the degree of suppression of energy expenditure and the serum barbiturate level. However, this relationship would appear to be different in each patient, and therefore, for this group, a significant correlation between energy expenditure and serum barbiturate level does not exist. The wide variability of energy expenditure in individual patients makes the estimation of energy expenditure by population predictive formulas imprecise. This may lead to incorrect estimates of caloric requirements and inappropriate provision of exogenous energy substrates. Although for those patients receiving energy expenditure and serum barbiturate levels in the individual may further aid in estimating the caloric expenditure for each individual, in order to provide appropriate amounts of calories to the patient with trauma to the head, energy expenditure should be measured in each instance.

Macronutrient requirements in the malnourished cancer patient. How much of what and why?

Malnutrition is a prevalent problem in the hospitalized cancer population. Although the pathophysiology of cancer cachexia is incompletely understood, it assumes considerable clinical relevance because malnutrition is a potentially treatable problem associated with poor outcome. Once the clinician has made a decision to initiate enteral or parenteral nutritional support, the practical issue of macronutrient prescription necessitates review of existing animal and human data in order to formulate guidelines for nonprotein energy and nitrogen requirements for efficacious nutritional support in the malnourished cancer patient.

Alteration in pyruvate metabolism in the liver of tumor-bearing rats

Weight loss associated with tumor burden has been postulated to be due to an energy imbalance resulting from increased hepatic gluconeogenesis secondary to Cori cycle activity. The mechanisms which control pyruvate metabolism are inherent to the control of gluconeogenesis in the liver. Therefore, the metabolism of pyruvate was evaluated in a transplanted tumor model in rodents which has previously shown an increased rate of hepatic gluconeogenesis. Female Lewis-Wistar rats received a s.c. injection of a suspension of mammary tumor cells in the left flank. Tumor-bearing rats were allowed ad libitum food consumption, and non-tumor-bearing controls were pair-fed to the consumption of their tumor-bearing cohorts. At Days 12, 13, and 14 following inoculation, tumor-bearing and non-tumor-bearing controls were used for in vivo body composition analysis or subjected to isolated liver perfusion. Animals were not fasted prior to sacrifice. Pyruvate use by the livers of tumor-bearing and pair-fed non-tumor-bearing rats was evaluated in the presence of 8 mM glucose and 5 mM lactate. Pyruvate clearance was increased by 270%, and pyruvate intake was increased by 212% compared to pair-fed non-tumor-bearing rats. Oxidation of pyruvate to CO2 was increased 130%, and pyruvate conversion to lactate was increased by 197% above that seen in pair-fed non-tumor-bearing rats. Gluconeogenesis from pyruvate was increased by 184% in tumor-bearing rats. The increased gluconeogenesis in tumor-bearing rats above that of control animals at a 5 mM lactate concentration suggests that some factor, other than substrate supply, may stimulate gluconeogenesis in tumor-bearing rats. Although the use of pyruvate was greater in tumor-bearing rats, the disposal of pyruvate carbon into CO2, lactate, and glucose was proportionally the same in both groups. Therefore, these data suggest that the increased metabolism of pyruvate in tumor-bearing rats is controlled by a mechanism affecting cellular pyruvate transport.

Energy expenditure in primary malnutrition during standardized exercise

When eight malnourished females without organic disease, were subjected to a controlled treadmill exercise test, they expended less total energy than females of normal body weight. The malnourished subjects consumed less oxygen than the control subjects, but oxygen consumption increased with increasing work load. The resting energy expenditure of the malnourished subjects was less than predicted values, but body composition as determined by muscle mass, total body water and thyroxine levels were within normal limits. Although decreased energy expenditure associated with malnutrition, has been attributed to decreased oxygen transport and altered hemoglobin, the malnourished subjects in this study did not have reduced hemoglobin levels. Metabolic adaptation may have occurred in order to improve the efficiency of aerobic metabolism. In order to confirm this theory, energy expenditure should be assessed under conditions of maximal oxygen intake.

Total body water and total body potassium in anorexia nervosa

In the ill hospitalized patient with clinically relevant malnutrition, there is a measurable decrease in the ratio of the total body potassium to total body water (TBK/TBW) and a detectable increase in the ratio of total exchangeable sodium to total exchangeable potassium (Nae/Ke). To evaluate body composition analyses in anorexia nervosa patients with chronic uncomplicated semistarvation, TBK and TBW were measured by whole body K40 counting and deuterium oxide dilution in 10 females with stable anorexia nervosa and 10 age-matched female controls. The ratio of TBK/TBW was significantly (p less than 0.05) higher in anorexia nervosa patients than controls. The close inverse correlation found in published studies between TBK/TBW and Nae/Ke together with our results suggest that in anorexia nervosa, Nae/Ke may be low or normal. A decreased TBK/TBW is not a good indicator of malnutrition in the anorexia nervosa patient. The use of a decreased TBK/TBW ratio or an elevated Nae/Ke ratio as a definition of malnutrition may result in inappropriate nutritional management in the patient with severe nonstressed chronic semistarvation.

Relationships between serum total iron-binding capacity and transferrin

The relationship between serum transferrin ( TFN ) and serum total iron-binding capacity (TIBC) in a clinical setting was evaluated in two related studies. The initial study evaluated 101 blood samples representing a cross-section of hospitalized adults. The samples were double assayed for TIBC using clinical and research methodologies. TFN was assayed by a commercial radial immunodiffusion method. Clinical laboratory TIBC correlated well with research laboratory TIBC (r = 0.87, slope = 0.97, p less than 0.001, n = 50) and the relationship of TIBC to TFN yielded the following equation: TFN = 0.83 TIBC -5.6 (r = 0.82, p less than 0.001, n = 101) where TFN = mg/100 ml and TIBC = micrograms/100 ml. The second study evaluated a new TIBC assay and its effect on the TIBC/ TFN relationship. Additionally, the TFN -TIBC relationship was evaluated at low normal and abnormal TIBC levels. In this second study, TFN = 1.0 TIBC -18.8 (r = 0.88, p less than 0.01, n = 126). Subsample analysis for specimens with TIBC between 105 and 160 showed a TIBC- TFN regression line that was not significantly different than the entire sample. Inclusion of ancillary patient data such as hemoglobin and hematocrit did not improve the relationship between TFN and TIBC in either study. The relationship was unaffected by age, sex, race, disease, treatment, fever, surgery, degree of nutritional support, blood transfusion, or blood chemistry parameters in either study. Laboratories deriving TFN from measured TIBC as a nutritional status indicator must determine the relationship for the specific procedures being used in their laboratories.

Energy expenditure in malnourished gastrointestinal cancer patients

Cancer cachexia, a common finding in patients with gastrointestinal (GI) malignancy, is frequently attributed to tumor-induced aberrations in host energy expenditure. To characterize the frequency and severity of aberrations in energy expenditure in GI cancer patients, and to identify the potential influence of tumor characteristics in this group, the authors measured resting energy expenditure (REE) by indirect calorimetry in 173 patients and compared REE to predicted-energy expenditure (PEE) from the Harris-Benedict formulae based on current body weight. Fifty-eight percent of patients had abnormal REE (normal REE = +/- 10% PEE); 36% (62 of 173) were hypometabolic (REE less than 90% PEE), and 22% (39 of 173) were hypermetabolic (REE greater than 110% PEE). Host and tumor factors were compared between metabolic groups to identify potential determinants of abnormal energy expenditure. Differences between groups cannot be explained by differences in patient age, sex, body size, nutritional status, tumor burden, or duration of disease. Resting energy expenditure does not correlate with percent of weight loss, serum albumin, or duration of disease. Analysis by tumor site reveals patients with pancreatic or hepatobiliary tumors to be predominantly hypometabolic; gastric cancer patients tend to be hypermetabolic, whereas patients with colorectal or esophageal neoplasms are more evenly distributed across metabolic groups, the largest portion being normometabolic (X2 = 20.7, P less than 0.02). The majority of GI cancer patients have abnormal REE which is unpredictable and not uniformly hypermetabolic. The determinants of these abnormalities do not appear to be age, sex, body size, nutritional status or tumor burden. Primary tumor site is a major determinant of energy expenditure in GI cancer patients.

Alteration of tumor cell kinetics by pulse total parenteral nutrition. Potential therapeutic implications

Previous work has demonstrated that substrate-induced alterations of tumor metabolism can be exploited to potentiate tumor response to cycle-specific chemotherapy (methotrexate, Adriamycin [doxorubicin] ). This study was performed to investigate the biologic mechanism responsible for this phenomenon by determining the effect of short-term total parenteral nutrition (TPN) on tumor cytokinetics. Forty-two female Lewis/Wistar rats with subcutaneous mammary tumor implants (AC-33) underwent superior vena caval cannulation, and were randomized to receive either TPN or normal saline intravenously. Animals receiving TPN were killed at 2, 6, 12, 24, and 48 hours after initiating TPN; control animals given normal saline were killed at 0, 24, and 48 hours after randomization. At the time animals were killed tumor cytokinetic analysis was performed by flow cytophotometry. The percentage of tumor cells in S-phase was significantly increased in animals after only 2 hours of TPN (55.5 +/- 9.1%) compared with the control group (43.7 +/- 7.7%) (P less than 0.01). The ratio of sensitive/resistant tumor cells to S-phase-specific chemotherapy was effectively increased in animals receiving adjuvant TPN (1.31 +/- 0.43) compared with control animals (0.80 +/- 0.25) (P less than 0.015). This alteration in tumor cytokinetics provides one explanation for the enhanced tumor response to cycle-specific chemotherapy previously observed with pulse TPN administration.

Weight gain and nutritional efficacy in anorexia nervosa

To evaluate the usefulness of interval weight change in assessing nutritional support efficacy, we studied four anorexia nervosa patients (52% ideal body weight) requiring long-term total parenteral nutrition (TPN) for 63 +/- 18 days. Fluid and electrolyte deficits were corrected before the initiation of nutritional support. Resting energy expenditure was measured before the initiation of TPN and weekly thereafter, using indirect calorimetry. Daily caloric expenditure was estimated at 1.1 X resting energy expenditure, based on previous studies of continuous heart rate monitoring in this patient population. Daily excess calories were calculated as caloric intake minus caloric expenditure. Each patient was weighed daily and linear regression analysis (excess calories versus weight change) was performed for individual patients and the group over intervals of varying length. There was no individual or group correlation between excess calories and weight gain on a daily or weekly interval basis. Cumulative weight changes over the long-term course of TPN correlated significantly with cumulative excess calories for each patient and the whole group (r = +0.82, p less than 0.01). The excess calories required to gain a kilogram body weight ranged from 5569 to 15619 kcal/kg with a mean of 9768. Cumulative long-term weight changes during nutritional repletion in anorexia nervosa are meaningful indicators of caloric balance, but short interval weight changes (daily, weekly) are not. The caloric cost of weight gain is variable in this population.

Adjuvant, pulse total parenteral nutrition and tumor response to cycle-specific and cycle-nonspecific chemotherapy

Previous work has demonstrated that substrate-induced alterations of tumor metabolism can be exploited to enhance tumor response to a cycle-specific chemotherapeutic agent (methotrexate). This study was designed to further investigate the biologic mechanism of this phenomenon by determination of tumor response to additional cycle-specific (Adriamycin) and cycle-nonspecific (Cytoxan) chemotherapeutic agents. Significant potentiation of tumor response during adjuvant total parenteral nutrition (TPN) was observed with methotrexate and Adriamycin but not with Cytoxan. This may imply that tumor sensitization by adjuvant TPN occurs by acceleration of the growth rate of proliferating tumor cells and not by recruitment of dormant tumor cells into the cell cycle.

Enhanced tumor response to cycle-specific chemotherapy by parenteral amino acid administration

Forced feeding has been shown to effectively stimulate tumor metabolism in numerous animal models. Significant acceleration of tumor growth by exogenous nutrient administration is generally considered to be detrimental to the host. The present study was performed to determine if substrate-induced alterations in tumor metabolism could be exploited to enhance tumor response to cycle-specific chemotherapy. Following subcutaneous mammary tumor implantation (AC-33) and protein depletion, 39 female Lewis/Wistar rats were randomly assigned to one of four nutritional regimens for 48 hr: (1) protein-depleted food (0.03% protein) ad libitum po, (2) parenteral carbohydrate (18.6% dextrose), (3) parenteral amino acids (2.8% amino acids), or (4) total parenteral nutrition (18.6% dextrose/2.8% amino acids). Methotrexate (5 mg/kg im) was administered to all animals 2 hr after initiating these nutritional regimens. Tumor volume and host toxicity were monitored throughout the study. At sacrifice, significant reduction in tumor volume was observed in animals receiving parenteral amino acids (0.37 +/- 0.24 cm3) and total parenteral nutrition (0.25 +/- 0.18 cm3) compared to the group receiving protein-depleted food po (0.70 +/- 0.22 cm3) (p less than 0.01). In this animal model, the parenteral administration of amino acids with or without the addition of hypertonic dextrose was found to effectively potentiate tumor response to methotrexate without increasing host toxicity.

Prehepatic total parenteral nutrition in the chair-adapted primate

The relative efficacy of prehepatic and central venous infusion of total parenteral nutrition (TPN) was evaluated in a chair-adapted primate model. Four adult male monkeys (Macaca fascicularis) underwent surgical placement of a silastic catheter in both the portal vein (PV) and superior vena cava (SVC). Following recovery (10 days), each animal received two courses of TPN (100 kcal and 4 g of protein/kg/day) for 10 days each via the PV and SVC in an alternating crossover manner. The prehepatic (PV) infusion of TPN in the well nourished, chair-adapted primate results in maintenance of weight (PV: delta - 0.07 kg; SVC:delta - 0.07 kg), nitrogen equilibrium (PV:+ 0.8 g N/day; SVC: + 0.7 g N/day), and trends in serum albumin (PV:delta - 0.35 g %; SVC: delta - 0.38 g %), and total iron binding capacity (PV:delta + 44 mg %; SVC:delta + 8.67 mg %) comparable to the SVC route. No significant abnormalities in liver enzyme production were observed with either route of infusion. Whole body protein synthesis rates using 15N-glycine tracer were likewise comparable (PV = 2.05 g N/kg/day; SVC = 2.18 g N/kg/day). Prehepatic delivery and primary hepatic modulation of substrates does not substantially improve the efficacy of parenteral nutrient administration. Intestinal modification of substrates may be the most important contributing factor in the supposed superiority of enteral alimentation.

Estimation of fecal nitrogen in patients with liver disease

The use of a fecal nitrogen (FN) predictive equation (Am J Clin Nutr 1978; 31:12-22, Cheng) based on dietary nitrogen intake (Nin) [FN (mg/kg/day) = 10.817 + 0.03 Nin(mg/kg/day)] was evaluated in patients with liver disease with and without concomitant lactulose therapy. Ten male cirrhotics were studied in 27 3-day nitrogen balance studies including measured daily total urinary nitrogen, total FN, and Nin calculated from weighted food records. The Cheng formula accurately predicted FN in cirrhotics not receiving lactulose who demonstrated normal digestion and absorption of dietary protein. However, the formula did not accurately reflect FN excretion in patients receiving lactulose who showed impaired protein digestibility and significantly increased fecal weight. The Cheng predictive equation is a useful index of FN excretion in patients with liver disease whose digestive and absorptive capacities are not compromised by exogenous factors.

Tumor effects on gluconeogenesis in the isolated perfused rat liver

Alterations in metabolism in the tumor-bearing host can be explained by: 1) alterations of metabolic processes in the tumor itself, and/or 2) tumor effects on host metabolism. Tumor effects on host liver metabolism were studied using an isolated perfused rat liver preparation. The livers of fasted female Lewis Wistar rats with and without transplanted subcutaneous mammary tumors were perfused for 1 hr with medium containing 5 mM glucose and physiological levels of amino acids. The rate of gluconeogenesis, as measured by conversion of 14C-lactate to 14C-glucose, showed a significant increase in the rate of glucose production from lactate in tumor-bearing rats (2.40 vs 2.00 mumol/min/100 gm). Hepatic glycogen and 14C-glycogen content were not significantly different between the two groups. In order to evaluate whether this tumor model exhibits characteristic changes in metabolism previously reported in other animal tumor models, serum lactate, triglyceride, glucose, and blood urea nitrogen were measured in non-perfused animals. The serum concentration of lactate and triglycerides were significantly higher in tumor-bearing rats (0.9 mM vs 2.7 mM lactate; 244 mg % vs 365.5 mg % triglycerides). Serum glucose and blood urea nitrogen were not significantly different in the two groups. An effect of tumor on host energy metabolism and serum metabolite levels is demonstrated. A method for the study of host-tumor metabolic interactions is described.

Energy expenditure in malnourished cancer patients

It is widely believed that the presence of a malignancy causes increased energy expenditure in the cancer patient. To test this hypothesis, resting energy expenditure (REE) was measured by bedside indirect calorimetry in 200 heterogeneous hospitalized cancer patients. Measured resting energy expenditure (REE-M) was compared with expected energy expenditure (REE-P) as defined by the Harris-Benedict formula. The study population consisted of 77 males and 123 females with a variety of tumor types: 44% with gastrointestinal malignancy, 29% with gynecologic malignancy, and 19% with a malignancy of genitourinary origin. Patients were classified as hypometabolic (REE less than 90% of predicted), normometabolic (90-110% of predicted) or hypermetabolic (greater than 110% of predicted). Fifty-nine per cent of patients exhibited aberrant energy expenditure outside the normal range. Thirty-three per cent were hypometabolic (79.2% REE-P), 41% were normometabolic (99.5% REE-P), and 26% were hypermetabolic (121.9% REE-P) (p less than 0.001). Aberrations in REE were not due to age, height, weight, sex, nutritional status (% weight loss, visceral protein status), tumor burden (no gross tumor, local, or disseminated disease), or presence of liver metastasis. Hypermetabolic patients had significantly longer duration of disease (p less than 0.04) than normometabolic patients (32.8 vs. 12.8 months), indicating that the duration of a malignancy may have a major impact upon energy metabolism. Cancer patients exhibit major aberrations in energy metabolism, but are not uniformly hypermetabolic. Energy expenditure cannot be accurately predicted in cancer patients using standard predictive formulae.

Resting energy expenditure in morbid obesity

Resting energy expenditure (REE) was measured in 112 morbidly obese adults prior to elective gastric bypass surgery. The patients studied ranged from 157 to 327% of ideal body weight. Standard nutritional assessment indices (serum total protein, albumin, total iron binding capacity, hematocrit, and white blood cell count) were within normal limits. REE was estimated by the Harris-Benedict formula using both current weight and ideal weight. Measured REE was significantly less than expected (p less than 0.01) using current weight and significantly greater than expected (p less than 0.01) when ideal weight was used as the standard. Linear regression analysis between standard indices that reflect resting metabolic rate in normal adults and measured REE in study patients did not demonstrate sufficient correlation to be clinically useful in this patient population. Standard surgical therapy may result in highly variable weight loss in this population if the wide range of resting energy expenditure and the consequential variability in individual caloric deficits is not considered. Standard predictors do not identify those patients likely to be unsuccessful with a given weight loss regimen.

Nutritional assessment in the seriously ill patient

A consensus definition of malnutrition does not exist. We define "clinically relevant malnutrition" as the state of altered nutritional status that adversely affects clinical outcome. Over four years we have attempted to delineate a clinically applicable and validated nutritional assessment approach. This was accomplished through multiple clinical studies on a large number of surgical patients many of whom were seriously ill. Although an initial prospective study in 64 patients confirmed the relationship between certain nutritional markers and outcome, we found that 97% of patients had at least one abnormality, while 35% had three or more abnormalities, clearly documenting the imprecision in unselected battery testing. In a subsequent retrospective analysis of 161 patients, serum albumin (Alb), serum transferrin (TFN), triceps skinfold (TSF), and skin test reactivity (DH) proved to be the best markers of clinically relevant malnutrition and their relative quantitative importance is embodied in our Prognostic Nutritional Index (PNI), where PNI (% risk) = 158 - 16.6 (Alb) - 0.78 (TSF) - 0.20 (TFN) - 5.8 (DH). In numerous prospective studies of different patient groups, a large percentage of which were critically ill, the PNI has been shown to be a reliable nutritional assessment tool for diagnosing clinically relevant malnutrition. Furthermore, we have shown that seriously malnourished patients classified by the PNI will clinically benefit from preoperative nutritional support. The relevance of baseline and serial nutritional assessment to the nutritional care of the critically ill patient is discussed.