Effect of neuromuscular blockade on oxygen consumption and energy expenditure in sedated, mechanically ventilated children.

OBJECTIVE: To quantify the effects of neuromuscular blockade (NMB) on energy expenditure for intubated, mechanically ventilated, critically ill children. DESIGN: A prospective, unblinded clinical study. Each subject was studied twice, before and after establishment of NMB. SETTING: A tertiary care pediatric intensive care unit. PATIENTS: Critically ill children undergoing mechanical ventilation and receiving ongoing sedation were eligible, if they had a cuffed endotracheal tube and were physiologically stable. INTERVENTIONS: A total of 20 children (age, 1 to 15 yrs) were studied in an unblinded, crossover fashion. All were mechanically ventilated via a cuffed endotracheal tube, with ventilator rate and tidal volume adequate to provide complete ventilation, and F(IO2) <0.6. Absence of gas leak around the endotracheal tube was assured, and all patients were sedated using continuous infusions of midazolam and/or fentanyl; no changes in ventilator settings, nutritional input, or inotropic drug dose were permitted during the study period. Each patient underwent indirect calorimetry immediately before establishment of NMB. NMB was then induced, and indirect calorimetry was repeated. Complete blockade was verified using a peripheral nerve stimulator. In each case, the two sets of measurements were completed within a 1-hr period. MEASUREMENTS AND MAIN RESULTS: Data analyzed included identifying and diagnostic information, oxygen consumption, and carbon dioxide production. Energy expenditure was calculated using standard formulas. Oxygen consumption and energy expenditure values obtained before and after the establishment of NMB were compared by using paired Student's t-test. NMB reduced oxygen consumption from 6.54+/-0.49 mL/kg/min to 5.90+/-0.40 ml/kg/min, and energy expenditure was reduced from 46.5+/-3.7 kcal/kg/24 hrs to 41.0+/-2.8 kcal/kg/24 hrs (p < .001 in each case). The reduction in oxygen consumption was 8.7+/-1.7%, and that in energy expenditure 10.3+/-1.8%, of pre-NMB values, respectively. CONCLUSION: NMB significantly reduces oxygen consumption and energy expenditure in critically ill children who are sedated and mechanically ventilated; the degree of reduction is small.

Nonradiographic assessment of enteral feeding tube position.

OBJECTIVE: To determine whether a clinical, nonradiographic criterion can be used to predict when the tip of a blindly placed feeding tube is in the small intestine. DESIGN: Prospective sample. SETTING: Pediatric intensive care unit at a tertiary care children's hospital. PATIENTS: Critically ill children requiring transpyloric feeding. INTERVENTIONS: The small bowel was intubated, using a blind, bedside transpyloric feeding tube placement protocol. The feeding tube was considered to be in the small bowel when <2 mL of a 10- mL aliquot of insufflated air could be aspirated from the feeding tube. This clinical criterion was confirmed with an abdominal radiograph. MEASUREMENTS AND MAIN RESULTS: Patient age ranged from 1 month to 19 yrs (median 6 months). Weight ranged from 2.2 to 60 kg (median 4.9). Median time to feeding tube placement was 10 mins (range 5 to 60). Eighty-nine percent of the patients were mechanically ventilated, while 28% of these patients were pharmacologically paralyzed. Seventy-five feeding tubes were inserted. There were no known complications. Ninety-nine (74/75) percent of the feeding tubes were positioned in the small bowel. The inability to aspirate insufflated air correctly predicted small bowel intubation with 99% certainty (Sequential Probability Ratio Test, p = .05 and power = .80). This test incorrectly predicted the position of only one feeding tube, the 26th, which was in the stomach. Of the 74 feeding tubes positioned in the small bowel, 13 feeding tubes were in the duodenum and 61 were in the jejunum. CONCLUSIONS: The inability to aspirate insufflated air confirms the transpyloric position of a feeding tube. Other clinical criteria did not successfully predict small bowel intubation. Use of this single test may obviate confirmatory abdominal radiographs in carefully selected patients and may lead to more cost-effective and timely initiation of enteral feedings.