Askanazi J

Nutrition and the respiratory system

SUMMARYMalnutrition and weight loss are among the signs of a poor prognosis in the natural history of patients with COLD.123, 124 Patients whose only source of daily nutrition is 2–31 of 5% dextrose suffer malnutrition and weight loss. This has been documented to be detrimental.Currently, there are insufficient data to propose the optimum form and amount of nutritional intake. Thus, it is appropriate to suggest moderation in nutritional support of patients with compromised pulmonary reserve. Glucose infusions may be expected to replenish tissue glycogen and, hence, be associated with improved work performance; however, CO2 production is significantly increased. However, an increased RQ may provide a more favorable alveolar Po2 which could be important in patients with COLD during room air breathing. Fat emulsions are commercially available, can minimize CO2 production, and have been shown to be N sparing. However, serum hyperlipemia may compromise pulmonary diffusing capacity. Increasing nitrogen intake can increase ventilatory drive, but this may lead to a feeling of dyspnea and be detrimental in patients unable to increase minute ventilation.Parenteral nutrition should be guided by whether the goal is to: (a) preserve lean body mass in patients who are in satisfactory nutritional condition but whose return to oral intake is not imminent, or (b) restore lean body mass in patients who have lost greater than 10% of normal body weight. In patients where the intent is maintenance of lean body mass, nutritional support should be designed to attain calorie and nitrogen equilibrium. Practically speaking, this means: (1) energy intake of 1–1.2 χ energy expenditure; (2) nitrogen intake of 200–300 mg/kg. At this institution, 50% of the nonprotein calories are given as fat emulsions. In patients where the goal is restoration of lean body tissue, the nutritional regimen should be designed to achieve a distinctively positive calorie and nitrogen balance. Energy intake is set at 1.4–1.6 χ energy expenditure. Nitrogen intake is between 250–400 mg/kg body weight. One-half of the nonprotein calories are given as lipid.These recommendations are based upon limited data and indirect evidence. Further studies of nutrition and respiration are needed to construct more definitive guidelines in this important area of clinical care.

Risks and Benefits of Home Parenteral Nutrition in the Acquired Immunodeficiency Syndrome

The gastrointestinal tract is a major target of the human immunodeficiency virus. Many AIDS patients have weight loss and/or diarrhea. Parenteral nutrition can be used to treat malnutrition associated with malabsorption. We reviewed retrospectively the clinical course of 22 patients with AIDS and weight loss greater than 10% who received home parenteral nutrition (HPN) for 56.2 patient-months. Mean weight loss was 21.4%, mean duration of HPN 2.55 months, mean age 37.4 years. Fifteen patients gained weight, six stabilized and two continued to lose weight. Nine patients returned to previous activity. Five died. The rates of catheter-related sepsis, complications, and metabolic disturbances were 0.12, 0.25, and 0.12/100 catheter days, respectively, results identical to those reported in other patient populations where HPN is commonly applied. We found that HPN induced weight gain and clinical improvement in most patients without higher risks of sepsis than in patients with malignancies.

Parenteral Nutrition and Oral Intake: Effect of Glucose and Fat Infusions

The effect of intravenous nutrition on voluntary oral intake was studied in healthy male volunteers. Subjects were confined to the Surgical Metabolic Unit for the 17 to 19 day study and were restricted to commercial liquid diet. Each study consisted of three consecutive phases: (1) Ringers lactate (RL), (2) peripheral parenteral nutrition (PPN) administered for 5 or 6 days as a combination of glucose (caloric load equal to 34% resting energy expenditure, REE), fat (34% REE), and amino acids (17% REE) or a single nutrient infusion of glucose (68% REE), fat (68% REE), glucose (34% REE), or fat (34% REE), and (3) RL for the third period. When all three nutrients or glucose alone (68% REE) were given, subjects decreased daily voluntary food intake within 24 to 48 hr by an amount that closely compensated for the infused calories. Intake was reduced by only 20% to 40% of the infused calories when fat alone (68% REE) was given. There were no significant effects when the lower levels of glucose and fat were given. These data suggest the presence of a postabsorptive control of food intake in humans that is sensitive to the circulating supply of fuels.

Clinical and Immunologic Effects of Lipid-Based Parenteral Nutrition in AIDS

The effect of lipid-based parenteral nutrition was assessed in eight patients with AIDS and weight loss of 10% or greater. All patients received home parenteral nutrition consisting of a lipid-based system with 50% of nonprotein calories given as fat. Measurements were made of body weight, serum albumin, and immune function as assessed by mitogen responses, P24 antigen levels and T-cell counts. Over a period of 2 months, weight gain and improved well-being were noted in all patients. An improved in vitro lymphocyte mitogenic response to phytohemagglutinin and to concanavalin A was also noted. No change in T-cell subsets was observed. Viral cultures and P24 serum levels also remained unchanged. Lipid-based parenteral nutrition is safe and probably efficacious in AIDS.

Increased body temperature secondary to total parenteral nutrition.

Administration of total parenteral nutrition (TPN) (glucose/amino acids), on the 2nd day after surgery, to a 26-year-old male with multiple fractures resulted in a rise in rectal temperature from 37.6 to 39°C. Resting energy expenditure showed a sustained 23% increase when the nutritional intake was changed from 5% dextrose to TPN. This case demonstrates that the increased metabolic rate associated with administration of TPN in acutely injured patients may be associated with an increase in body temperature.

Ventilatory effects of the stress hormones in normal man.

The ventilalory responses to catecholamine infusions have been well studied. Increases in plasma levels of cortisol and glucagon during stress may exert a synergistic effect with epinephrine. We examined the effect of epinephrine and a combined hormone infusion in four normal postabsorptive subjects. On three separate occasions each subject was assigned randomly to receive a 5.5-h infusion of saline (control), epinephrine (1.2 μg/ min min). or epinephrine plus cortisol (5 mg/m2-min) plus glucagon (3 mg/kg min). Oxygen consumption (Vo2), CO2 production, minute ventilation (Ve), tidal volume (Vt), frequency (f), inspiratory flow, and in-spiratory time during room-air breathing and inhalation of 2% and 4% CO2 were measured before infusion and during the last 2 h of infusion, using a noninvasive canopy system. Vo2 increased significantly (p < .05) from the control condition during both combined and epinephrine infusions (23% and 11%, respectively). The increase in Ve was related linearly to the increase in Vo2, and was primarily due to an increase in Vt; however, there was a small rise in f. The Ve-Paco2 regression during CO2 inhalation was shifted leftward to an equal degree during both infusions. These data indicate that cortisol and glucagon augment the calorigenic action of epinephrine; ventilatory effects are augmented in relation to the changes in Vo2.