The effect of neuromuscular blockade on oxygen consumption in sedated and mechanically ventilated pediatric patients after cardiac surgery

Objective  To measure the effect of intense neuromuscular blockade (NMB) on oxygen consumption (VO₂) in deeply sedated and mechanically ventilated children on the first day after complex congenital cardiac surgery. Design  Prospective clinical interventional study. Setting  Pediatric intensive care unit of an university medical centre. Measurements and results  Nine mechanically ventilated and sedated children (weight 2.8–8.7 kg) were included. All children were treated with vasoactive drugs. The level of sedation was quantified using the comfort score, Ramsay score and bispectral index (BIS). The intensity of NMB was quantified using acceleromyography and VO₂ was measured using indirect calorimetry. Analgo-sedation using various intravenous agents was targeted at a deep level (comfort score < 18, BIS < 60 and Ramsay score > 4). NMB was achieved by intravenous administration of rocuronium. All measurements were conducted before, during and after recovery from a period of intense NMB. Baseline values were VO₂ 6.1 ml/(kg min) (SD 1.3), comfort score 13 (SD 0.7), BIS 42.5 (SD 14.2), mean blood pressure 54.0 mmHg (SD 10.5), mean heart rate 129.9 bpm (SD 28.9) and mean core temperature 36.7°C (SD 0.5). There were no significant differences in VO₂ or other parameters between baseline, during NMB and the recovery phase. Conclusion  Neuromuscular blocking agents do not reduce oxygen consumption in deeply sedated and mechanically ventilated children after congenital cardiac surgery.