Support of respiratory failure in the pediatric surgical patient

Lung Development and Susceptibility to Ventilator-induced Lung Injury

RATIONALE

Ventilator-induced lung injury has been predominantly studied in adults.

OBJECTIVES

To explore the effects of age and lung development on susceptibility to such injury.

METHODS

Ex vivo isolated nonperfused rat lungs (infant, juvenile, and adult) were mechanically ventilated where VT was based on milliliters per kilogram of body weight or as a percentage of the measured total lung capacity (TLC). In vivo anesthetized rats (infant, adult) were mechanically ventilated with pressure-limited VTs. Allocation to ventilation strategy was randomized.

MEASUREMENTS

Ex vivo injury was assessed by pressure-volume analysis, reduction in TLC, and histology, and in vivo injury by lung compliance, cytokine production, and wet- to dry-weight ratio.

MAIN RESULTS

Ex vivo ventilation (VT 30 ml.kg(-1)) resulted in a significant reduction (36.0 +/- 10.1%, p < 0.05) in TLC in adult but not in infant lungs. Ex vivo ventilation (VT 50% TLC) resulted in a significant reduction in TLC in both adult (27.8 +/- 2.8%) and infant (10.6 +/- 7.0%) lungs, but more so in the adult lungs (p < 0.05); these changes were paralleled by histology and pressure-volume characteristics. After high stretch in vivo ventilation, adult but not infant rats developed lung injury (total lung compliance, wet/dry ratio, tumor necrosis factor alpha). Surface video microscopy demonstrated greater heterogeneity of alveolar distension in ex vivo adult versus infant lungs.

CONCLUSION

These data provide ex vivo and in vivo evidence that comparable ventilator settings are significantly more injurious in the adult than infant rat lung, probably reflecting differences in intrinsic susceptibility or inflation pattern.

How low can you go? Effectiveness and safety of extracorporeal membrane oxygenation in low-birth-weight neonates

PURPOSE

Controversy exists regarding the criteria for placement of infants on extracorporeal membrane oxygenation (ECMO) at low birth weights. The authors hypothesized that ECMO is effective and safe in babies under 2 kg and sought to examine outcome and survival rate in these infants.

METHODS

All patients less than 30 days old in the Extracorporeal Life Support Organization (ELSO) registry (n = 14,305) were divided into those less than 2 kg (n = 663) and more than 2 kg (n = 13,642). Multiple regression analysis determined factors that predicted survival rate and the lowest safe weight for ECMO.

RESULTS

Overall survival rate was 76% and was lower in infants less than 2 kg (> or =2 kg, 77% v <2 kg, 53%, P <.0001). Survival rate was significantly lower for patients with diaphragmatic hernia (CDH), bleeding, and intracranial hemorrhage (ICH) by regression. The incidence of ICH in babies less than 2.0 kg was 6% versus 4% in those more than 2.0 kg (P <.05). Regression analysis determined that the lowest weight at which a survival rate of 40% could be achieved was 1.6 kg.

CONCLUSIONS

Cannulation for ECMO may be safe and effective in babies under 2.0 kg and potentially as low as 1.6 kg. Judicious anticoagulation might limit bleeding, which occurred in a minority of these patients.