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 energ y expenditure for intubated, mechanically ventilated, critically ill childr en. Design:A prospective, unblinded clinical study. Each subject was studied tw ice, before and after establishment of NMB. Setting: A tertiary care pediatric intensive care unit. Patients: Critically ill children undergoing mechanical ventilation and rec eiving ongoing sedation were eligible, if they had a cuffed endotracheal tu be 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 cuffe d endotracheal tube, with ventilator rate and tidal volume adequate to prov ide complete ventilation, and Ro, <0.6. Absence of gas leak around the endo tracheal tube was assured, and all patients were sedated using continuous i nfusions of midazolam and/or fentanyl; no changes in ventilator settings, n utritional input, or inotropic drug dose were permitted during the study pe riod. Each patient underwent indirect calorimetry immediately before establ ishment of NMB. NMB was then induced, and indirect calorimetry was repeated . Complete blockade was verified using a peripheral nerve stimulator. In ea ch case, the two sets of measurements were completed within al-hr period. Measurements and Main Results: Data analyzed included identifying and diagn ostic information, oxygen consumption, and carbon dioxide production. Energ y expenditure was calculated using standard formulas. Oxygen consumption an d energy expenditure values obtained before and after the establishment of NMB were compared by using paired Student's t-test. NMB reduced oxygen cons umption from 6.54 +/- 0.49 ml/kg/min to 5.90 +/- 0.40 mL/kg/ min, and energ y 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 consumptio n was 8.7 +/- 1.7%, and that in energy expenditure 10.3 +/- 1.8%, of pre-NM B values, respectively. Conclusion: NMB significantly reduces oxygen consumption and energy expendi ture in critically ill children who are sedated and mechanically ventilated ; the degree of reduction is small.