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Predicting energy needs in critical illness can be difficult because of uncertainties about the influence of multiple factors on energy expenditure. Understanding these components is important to avoid limiting optimal outcome by underfeeding and to avoid complications of overfeeding. Prediction strategies often use a patient's weight to estimate needs. For overweight patients, there is controversy as to whether actual or modified weight should be used in predictions. This study was designed to evaluate a proposed technique to improve the accuracy of predicting energy needs in critically ill, overweight subjects. Subjects' energy needs were predicted [with Harris-Benedict equation (HBE) and kilojoules per kilogram (KPK) strategies] by using both actual weight and an adjusted weight developed to attempt to more accurately reflect lean mass. Results were compared with measured energy expenditure determined by indirect calorimetry. Results indicated that use of actual weights in predictions for overweight subjects may lead to overfeeding. Use of adjusted weights led to more accurate energy predictions with the KPK than with the HBE strategy. Adjusted-weight strategies could explain > 45% of the variability of resting energy expenditure in subjects 130-159% of ideal body weight. Results of this study suggest that using adjusted weights with the KPK prediction strategy may be preferable for this population, particularly for patients > or = 130% of ideal body weight. This study also indicated that multiple diagnoses may not lead to increased energy requirements.

Leukotriene B4 (LTB4) serum and plasma concentrations were reported to be higher in some asthmatic patients than in normal subjects; however, reported LTB4 concentrations in normal subjects vary widely. One study suggested that blood clotting causes the increased LTB4 concentration.To determine whether LTB4 concentration is increased in asthmatic patients, and whether it is affected by clotting.We studied seven normal subjects and nine clinically stable asthmatic patients. Venous blood was drawn into test tubes without additives; containing heparin; or containing heparin and cyclo- and lipoxygenase inhibitors. Cells were separated after 30 minutes. Leukotriene B4 was measured by radioimmunoassay following its extraction from serum or plasma. In three subjects, plasma was separated also at times 0 through 30 minutes.Serum and plasma concentrations of LTB4 in normal volunteers and asthmatic patients were similar, but the variance of LTB4 concentrations among the asthmatic patients was significantly higher than in the normal subjects. Leukotriene B4 concentrations, measured in plasma only, were significantly reduced in both asthmatic and nonasthmatic subjects in the presence of inhibitors. There was no significant difference in LTB4 concentrations between time 0 and 30 minutes, but there was considerable variability.We conclude that clotting is unlikely to affect serum LTB4 concentrations. Leukotriene B4 serum and plasma concentrations are not consistently increased in asthmatic patients; however, LTB4 is synthesized during and possibly after blood has been drawn. Proper handling of the specimens and probably the addition of cyclo-oxygenase and lipoxygenase inhibitors is of the utmost importance for accurate LTB4 determination.

Patients with extensive small-bowel resection may experience malabsorption and nutrient deficiencies. We evaluated the ability to absorb fat and fat-soluble vitamins in a short-gut patient. For 18 wk after stopping intravenous lipid, while consuming a low-lactose, low-fat diet, he exhibited no clinical manifestations of essential fatty acid deficiency (EFAD). Serum 20:4n-6 (20:4 omega-6) and 18:2n-6 fatty acid concentrations were normal, whereas the concentration of 20:3n-9 remained less than or equal to 0.1% of total serum fatty acids. Although serum vitamin A was normal, beta-carotene was undetectable despite oral supplementation. Prothrombin time was elevated until parenteral vitamin K was given. This patient has fat absorption adequate to prevent EFAD but inadequate absorption of fat-soluble vitamins. In patients with short bowel, the requirements for parenteral lipids and fat-soluble vitamins should be determined independently.

Human epidemiology studies demonstrate an inverse correlation between serum levels of vitamin A and the incidence of lung cancer. While such studies suggest that vitamin A may have a role in cancer prevention, the intent of this study was to investigate the use of vitamin A status parameters as markers for detection of occult lung cancer. In the first of two phases of this study, we established criteria for a prospective screening study. Serum levels of retinol-binding protein (RBP), zinc, retinol, and beta-carotene in lung cancer patients were compared to levels in controls. For the second phase, a prospective screening study, 100 ambulatory male cigarette smokers over the age of 45 were enrolled. Subjects were excluded if they had a known diagnosis of cancer, recent weight loss, or serum albumin less than 3.5 g/dl. Subjects with RBP less than 4.2 mg/dl and retinol less than 42 micrograms/dl were classified as high-risk; those remaining were classified as controls. A chest X-ray (CXR) was obtained on all 17 high-risk subjects and on 26 of the 83 controls. CXR was read and follow-up was performed by physicians without knowledge of this study. Lung cancer was detected in 24% (4/17) of the high-risk subset, and 4% (1/26) of the controls. These data suggest that retinol and RBP may be useful in lung cancer screening for selecting a high-risk population that warrants further examination.

An unusual case of osmotic diarrhea that persisted despite fasting led to the discovery of an unexpected source of hospital-acquired diarrhea. Numerous patients were subsequently found to have onset of diarrhea shortly after the initiation of treatment with theophylline elixir. Although theophylline can promote gastrointestinal secretion and motility, this effect should be independent of the route of theophylline administration and the stool should be characteristic of secretory rather than osmotic diarrhea. Patients taking no food orally while taking theophylline elixir continued to have osmotic diarrhea in excess of 1,000 ml/24 hr. Patients whose therapy was switched to intravenous or solid oral theophylline had resolution of diarrhea within 24 hours. The brand of theophylline elixir used was formulated with 30 gm of sorbitol per 240 mg of theophylline; thus a standard regimen of theophylline elixir was delivering four laxative doses of sorbitol daily. A cursory review revealed that many medicinal elixirs are formulated with sorbitol, despite being designated "sugar-free." When patients have osmotic diarrhea in the hospital, beware the medicinal elixir.

Leukotriene B4 (LTB4), an arachidonic acid metabolite released by neutrophils and macrophages, helps regulate host immune response to antigenic stimulation. LTB4 affects the chemokinesis, aggregation, and enzyme release of neutrophils and stimulates activity of cytotoxic T cells, natural killer cells, and suppressor T cells. LTB4 also has a positive affect on the margination of monocytes and macrophages in the lung in response to inflammatory stimuli. Cigarette smoking represents an inflammatory stimulus in the lung and affects (decreases) the in vitro release of LTB4 by alveolar, macrophages in comparison with that by alveolar macrophages of nonsmokers. By utilizing a sensitive and specific radioimmunoassay we have detected LTB4 concentrations in serum from smokers and nonsmokers. Furthermore, our preliminary data show mean LTB4 concentrations in the serum of smokers to be nearly 60-fold greater than those in nonsmokers, 211 (SEM 35) vs 3.6 (SEM 1.5). Because systemic quantities of LTB4 are now measurable, quantification of this immune system regulatory may be useful in evaluating inflammatory disease states.

Heparin sodium is routinely used in the prophylaxis against deep venous thrombosis in medical and surgical patients. While most physicians are aware of heparin-induced thrombocytopenia and skin necrosis, the association of heparin and hyperkalemia is less well recognized. We present four cases in which the use of heparin was associated with hyperkalemia and discuss the pathophysiology. Our findings suggest that hyperkalemia can develop with the use of low-dose heparin, within seven days of initiating heparin therapy, and that patients with diabetes mellitus or chronic renal insufficiency are especially predisposed to this complication.

Leukotriene B4 (LTB4), an arachidonic acid metabolite released by neutrophils and macrophages, helps regulate host immune response to antigenic stimulation. LTB4 affects the chemokinesis, aggregation, and enzyme release of neutrophils and stimulates activity of cytotoxic T cells, natural killer cells, and suppressor T cells. LTB4 also has a positive affect on the margination of monocytes and macrophages in the lung in response to inflammatory stimuli. Cigarette smoking represents an inflammatory stimulus in the lung and affects (decreases) the in vitro release of LTB4 by alveolar, macrophages in comparison with that by alveolar macrophages of nonsmokers. By utilizing a sensitive and specific radioimmunoassay we have detected LTB4 concentrations in serum from smokers and nonsmokers. Furthermore, our preliminary data show mean LTB4 concentrations in the serum of smokers to be nearly 60-fold greater than those in nonsmokers, 211 (SEM 35) vs 3.6 (SEM 1.5). Because systemic quantities of LTB4 are now measurable, quantification of this immune system regulatory may be useful in evaluating inflammatory disease states.

• Heparin sodium is routinely used in the prophylaxis against deep venous thrombosis in medical and surgical patients. While most physicians are aware of heparin-induced thrombocytopenia and skin necrosis, the association of heparin and hyperkalemia is less well recognized. We present four cases in which the use of heparin was associated with hyperkalemia and discuss the pathophysiology. Our findings suggest that hyperkalemia can develop with the use of low-dose heparin, within seven days of initiating heparin therapy, and that patients with diabetes mellitus or chronic renal insufficiency are especially predisposed to this complication. (Arch Intern Med1985;145:1070-1072)