Use of indirect calorimetry in the nutritional management of burned patients

Energy expenditure during severe acute pancreatitis

Energy expenditure (EE) was measured, during 3 consecutive days, in six patients suffering from acute pancreatitis. Measurements were achieved postoperatively, under mechanical ventilation, using a mass spectrometer system. EE represented 1.49 times (range: 1.08-1.78) the predicted resting energy expenditure (PREE) according to the reevaluated Harris-Benedict equation. There was a weak positive correlation between EE and core temperature and a negative correlation between EE and nitrogen balance. EE/PREE was not different between septic and nonseptic patients (1.58 +/- 0.06 vs. 1.39 +/- 0.07). The calculations of nutrient oxidation rate indicated a high protein catabolic rate, a neoglucogenesis, and a lipolysis.

Determinants of urinary nitrogen excretion in burned patients

A retrospective study of urinary urea excretion has been performed in 91 burned patients. Maximum mean excretion occurred between days 5 and 8 after injury. The rate of excretion during this peak period correlated significantly with the sex and age of the patient as well as the burn size. It is suggested that peak nitrogen excretion may be more accurately predicted if all three variables are considered. However, the wide variation seen in patient response and differences in clinical management mean that regular measurement of urinary urea excretion still provides the most reliable guide to dietary protein requirements after a burn.

Increased survival after major thermal injury. A nine year review

This study has reviewed the results of burn care in a burn center between 1978 and 1986. The total population included 1,458 patients. Mean burn size was 19 percent total body surface area, mean patient age was 24.4 years, and overall survival rate was 92 percent. We separately analyzed patients with burns of 30 percent total body surface area or greater during both halves of the study with respect to survival and length of hospital stay. Before 1982, patient survival was 59 percent and mean length of hospital stay was 28.1 days. Since that, the survival rate increased to 77 percent and mean length of hospital stay increased to 35.2 days. The early burn mortality rate remained nearly constant during the period of study (17 percent during the first half of the study and 16 percent during the second half), but the late mortality rate decreased significantly during the second half of the study (24 percent versus 8 percent, p less than 0.01). These data demonstrate increased survival rates after major thermal injury due to improvements in prevention and treatment of sepsis and other late complications of thermal injury.

Individualizing nutrition in patients with acute respiratory failure requiring mechanical ventilation

Provision of adequate nutrition is recognized as a therapeutic necessity to maintain inspiratory muscle strength and prevent weaning failures in patients with acute respiratory failure requiring mechanical ventilation. Total caloric needs are empirically estimated by calculation of basal energy expenditure and modified by correction factors for concurrent levels of stress. Energy requirements can vary considerably from empiric estimations and may be better defined by indirect calorimetry that measures oxygen consumption and carbon dioxide production. Protein constituents are initiated empirically until patient-specific urea nitrogen excretion is available. The addition of fat emulsion as 20-50 percent of total daily calories limits lipogenesis, prevents excessive carbon dioxide production, and provides a volume-concentrated caloric source to fluid-restricted patients. Manipulation of nutrient composition can improve or impair ventilatory weaning and nutritional rehabilitation. The significance of substrate utilization is reviewed and recommendations for establishing nutritional regimens for mechanically ventilated adults with acute respiratory failure are provided.

Closed-loop control of blood pressure, ventilation, and anesthesia delivery

Closed-loop control systems have been in use for over 4,000 years, yet applications in medicine have developed only recently. When compared with manual control, closed-loop controllers for blood pressure, ventilation, and anesthesia delivery provide more rapid and more precise control of mean pressure, end-tidal CO2, and end-tidal anesthetic concentrations. Closed-loop control systems perform better in almost all situations. It must be remembered however, that the best anesthesiologist may perform better than the controller, particularly in his ability to anticipate clinical events which effect control. Although the convenience, precision of control, and immunity to distractions are reason enough to further pursue their development, their final application to clinical care will depend on the inclusion of appropriate safeguards and supervisory software algorithms to protect the systems from failure.

Nutritional considerations for the burned patient

The metabolic response to injury is one of marked catabolic hormonal predominance resulting in hypermetabolism and protein wasting. Energy expenditure increases with increasing severity of injury, but reaches a maximum of twice resting energy expenditure when 50 per cent TBSA is burned. We agree with the nutritional recommendations of the group at the Boston Shriner's Burn Institute and the Massachusetts General Hospital. These include providing calories at twice the resting energy expenditure, as predicted by the Harris-Benedict equations, for patients with greater than 30 per cent BSAB; protein is provided at 2.5 gm per kg per day based on ideal body weight. It is important to recognize that these are optimal goals, but their attainment must be governed by safety considerations for the patient. It is probably safe to supplement intake with a multivitamin and vitamin C, as well as zinc, but our understanding of micronutrient therapy for stressed patients is rudimentary.