Suppression of the gut luminal aerobic flora to reduce nosocomial infections was tested in a prospective, randomized, double-blind, placebo-controlled clinical trial in patients in a surgical intensive care unit who had persistent hypermetabolism. Forty-six patients were randomized to receive either norfloxacin, 500-mg suspension every 8 hours, together with nystatin, 1 million units every 6 hours, or matching placebo solutions administered through a nasogastric tube within 48 hours of surgical intensive care unit admission. Selective gut decontamination with the experimental therapy or placebo solutions continued for at least 5 days or until the time of surgical intensive care unit discharge. Patients were monitored with routine surveillance cultures for the development of nosocomial infections, as defined by criteria from the Centers for Disease Control. All other therapy was given as clinically indicated, including systemic antibiotics. The selective gut decontamination group experienced a significant reduction in the incidence of nosocomial infections and a reduced length of stay. However, these results were not associated with a concomitant decrease in progressive multiple organ failure syndrome, adult respiratory distress syndrome, or mortality.
Urinary urea nitrogen (UUN) has been used as an estimate of total urinary nitrogen (TUN) when calculating nitrogen output for nitrogen balance (NB) studies. UUN is assumed to constitute 80 to 90% of the total nitrogen output; when estimating TUN from UUN, UUN values are multiplied by 1.25 to correct for non-urea nitrogen components. In order to evaluate the validity of estimating total urinary nitrogen output from measured UUN in a clinical setting, 491 UUN:TUN paired studies were performed on 24-hour urine collections in general surgical/trauma patients who had measured TUN outputs ranging from 0.04 to 54.0 g/d. Assessment of 315 NB studies was done to compare NB values of those calculated by using UUN as an estimate of TUN with those calculated from measured TUN. Patients in both studies were subdivided into four stress categories, using TUN/day as the index: less than 5 g, 5-10 g, 10-15 g, and greater than 15 g. On average, 80 to 90% of TUN is represented by the UUN. However, in our patient population the variability ranged from 12 to 112%. If these UUN values are used as estimates for TUN in calculating NB, variations of up to 12 g/d would result. Application of the correction factor of 1.25 is not consistent in correcting for nonurea nitrogen components in this clinical setting. The use of actual rather than estimated TUN may be a more accurate and appropriate method than UUN when calculating NB.
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