Detection of postoperative sepsis in infants with the use of metabolic stress monitoring.

OBJECTIVES: To evaluate the ability of serial protein metabolic monitoring to detect postoperative injury due to serious bacterial infection in infants by comparing changes observed in these protein parameters with more conventionally accepted indexes of infection. DESIGN: Retrospective review of infants whose postoperative course was complicated by bacterial infection compared with a matched cohort of infants in whom bacterial infection did not develop postoperatively. SETTING: Neonatal and pediatric intensive care units at the Wake Forest University Medical Center, Winston-Salem, NC. PATIENTS: Critically ill infants (N = 40) recovering from major surgical intervention. MAIN OUTCOME MEASURES: Serum C-reactive protein, prealbumin, and tumor necrosis factor concentrations were compared with the white blood cell count, immature-total neutrophil ratio, and body temperature obtained within 24 hours before and following the new onset of culture-established postoperative bacterial infection in 13 infants. These infants were compared with a matched cohort of 27 infants in whom postoperative bacterial infection did not develop. RESULTS: Only C-reactive protein (P = .0001) and prealbumin (P = .0003) levels were significantly altered in association with the onset of serious bacterial infection (paired t test). The C-reactive protein levels were clearly superior to all other variables in predicting postoperative infection (at cutoff point > 6.0 mg/dL; sensitivity, 92%; specificity, 96%). The predictive power of prealbumin level was lower, but acceptable (at cutoff point < or = 9.0 mg/dL; sensitivity, 85%; specificity, 74%). CONCLUSIONS: Monitoring of serial protein metabolic stress with C-reactive protein and prealbumin levels in infants following operations is more effective than the white blood cell count, immature-total neutrophil ratio, or temperature in detecting serious postoperative infections.

Relationship of metabolic indexes to postoperative mortality in surgical infants.

Acute injury is known to evoke a metabolic stress response, characterized by cytokine release and reprioritization of hepatic protein synthesis to increase acute phase proteins at the expense of visceral proteins. The impact of these evolving, stress-induced, perioperative metabolic changes on clinical outcome in surgical infants has not yet been determined. The cytokine (tumor necrosis factor [TNF]), acute phase protein (C-reactive protein [CRP]), and visceral protein (prealbumin [PA]) responses to acute metabolic stress were evaluated in 41 infants (average age, 47 days) preoperatively and on postoperative days 1 through 7 (POD 1 to 7) following major surgery. Infants were retrospectively grouped according to whether they survived (group 1) or died within 30 days of surgery (group 2). Peak CRP values in the postoperative period were also included for both groups. Peak CRP levels (14.9 +/- 5.5 v 8.1 +/- 5.7 mg/dL) were significantly increased (P = .0056) and preoperative prealbumin levels (6.0 +/- 2.7 v 11.0 +/- 5.2 mg/dL) were significantly decreased (P = .0005) in group 2 (nonsurvivors) compared with group 1 (survivors). Though serum TNF levels were substantially increased in nonsurvivors compared with survivors, both preoperatively (16.5 +/- 35.2 v 0.6 +/- 2.6 pg/mL) and on POD 1 (3.6 +/- 6.8 v 0.6 +/- 2.7 pg/mL), these values did not reach statistical significance (P > .05). The most significant difference (P = .0001) was observed in persistently depressed late (POD 4 to 7) prealbumin levels in nonsurvivors relative to survivors (5.3 +/- 3.1 v 10.5 +/- 4.3 mg/dL), suggesting an increased risk of poor outcome if acute metabolic stress had not abated by this time.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of total body water measurements using whole-body magnetic resonance imaging versus tritium dilution in primates.

Standard techniques conventionally used to assess body composition have various drawbacks which include a requirement for specialized equipment and expertise not widely available, radiation exposure, extensive study time periods, and limited clinical utility. Anthropometric methods, which are more clinically feasible, also involve substantially greater calculation error. This study was designed to compare a newly developed whole-body magnetic resonance (MR) imaging technique with standard tritium dilution (THO) to measure total body water (TBW) in eight primates (Macaca fascicularis). Sedated primates underwent whole-body MR imaging (10-12 contiguous 50-mm slices) and TBW was computed using a previously validated program. After 5 days to allow for primate recovery and stabilization, TBW measurements were repeated using THO methodology. Linear regression analysis of TBWMRI (72.1 +/- 5.7% body wt) compared with TBWTHO (73.8 +/- 3.2% body wt) yielded a Pearson correlation of r = 0.8145, P = 0.02 with a mean squared error of 2.14. Whole-body MR imaging determination of TBW correlates well with THO, requires less time (20 min versus 24 hr), and does not expose the subject to radiation. This study suggests that whole-body MR imaging is an accurate technique for in vivo body composition analysis. As demonstrated by the body size of this investigational primate model, the technique maybe particularly applicable to the study of human infants.

Serum visceral protein levels reflect protein-calorie repletion in neonates recovering from major surgery.

Protein catabolism resulting from acute metabolic stress causes significant postoperative decreases in visceral proteins, including albumin (Alb) and prealbumin (PA). Although clinical trials have suggested an advantage of PA over Alb in monitoring the visceral protein response to nutritional supplementation following surgery, the capability of the neonate to generate such a response has yet to be evaluated. Therefore, this study was undertaken to determine if PA is superior to Alb in assessing postoperative repletion of the visceral protein pool in neonates. Serum Alb and PA levels were measured and energy balance (EB) and protein intake (PI) were recorded in 10 neonates less than 48 hours after major surgery and again following 4 consecutive days of positive EB. Resting energy expenditure (REE) was measured using indirect calorimetric methodology. Mean PI (g/kg/d) was lower (0.78 +/- 0.78) and mean EB (kcal/kg/d) was negative (-2.92 +/- 10.05) less than 48 hours postoperatively compared with mean PI (2.52 +/- 0.57; P = .0006) after 4 consecutive days of positive EB (34.84 +/- 16.5; P = .0004). Mean percent change (mean% delta) from negative EB to positive EB was significantly greater for PA (100%; P = .0002) as compared with Alb (18.5%). These data appear to support the conclusion that serial serum PA levels are superior to Alb to monitor the visceral protein response to nutritional supplementation in neonates following surgery.