Strain-specific differences in lung tissue viscoelasticity of mechanically ventilated infant Sprague-Dawley and Wistar rats.

Rats are often used in ventilator-induced lung injury (VILI) models. However, strain-specific susceptibility for VILI has not been elucidated yet. The aim of this study was to demonstrate strain-specific differences in VILI in infant Sprague-Dawley and Wistar rats. VILI was compared in 2-wk-old pups after 8 h of protective or injurious ventilation. Pups were ventilated with tidal volumes (VT) of ∼7 mL/kg and positive end-expiratory pressures (PEEP) of 6 cmH2O (VT7 PEEP6) or with VT of ∼21 mL/kg and PEEP 2 cmH2O (VT21 PEEP2). Interleukin-6, macrophage inflammatory protein-2 (MIP-2), inflammatory cells, and albumin in bronchoalveolar lavage fluid (BALF); histology; and low-frequency forced oscillation technique (LFOT) and pressure-volume (PV) maneuvers were assessed. Alveolar macrophages, neutrophils, and MIP-2 derived from BALF revealed more pronounced VILI after VT21 PEEP2 in both strains. LFOT and PV analyses demonstrated rat strain-specific differences both at baseline and particularly in response to VT21 PEEP2 ventilation. Sprague-Dawley rats showed higher airway and tissue resistance and elastance values with no difference in hysteresivity between ventilation strategies. Wister rats challenged by VT21 PEEP2 experienced significantly more energy dissipation when compared with VT7 PEEP6 ventilation. In conclusion, both rat strains are useful for VILI models. The degree of VILI severity depends on ventilation strategy and selected strain. However, fundamental and time-dependent differences in respiratory system mechanics exist and reflect different lung tissue viscoelasticity. Hence, strain-specific characteristics of the respiratory system need to be considered when planning and interpreting VILI studies with infant rats.

Enteroviral myocarditis in neonates.

Enteroviruses are a leading cause of viral infections in children. While most enteroviral infections are mild and self-limiting, severe disease such as a viral sepsis syndrome, myocarditis, hepatitis and meningoencephalitis may occur. We present two cases of neonatal enteroviral myocarditis. Cardiorespiratory failure occurred in both cases, and severe shock refractory to conventional treatment required support with extracorporeal membrane oxygenation (ECMO). One child with coxsackievirus B3 myocarditis failed to recover and died after 3 weeks on ECMO, while one child could be decannulated successfully after 9 days of ECMO and recovered completely subsequently. In conclusion, neonatal myocarditis has a very high mortality, and ECMO should be considered early in neonates with rapid clinical and echocardiographic deterioration despite adequate inotropic support.

Increasing incidence of respiratory distress in neonates.

AIM: To document the change in the incidence of respiratory distress (RD), related interventions and mortality in neonates admitted to primary, secondary and tertiary neonatal units within a geographically defined population over a period of 30 years. METHODS: RD was defined as a clinical picture irrespective of the etiology. Information was collected retrospectively for 1974, 1984, 1994 and 2004 from all neonatal units in Switzerland. RESULTS: In the 30 years studied the proportion of infants hospitalized with RD increased from 1.9% to 3.8% of the whole neonatal population and from 30% to 53% of all infants admitted to a neonatal unit. Treatment of RD changed significantly. Mechanical ventilation decreased from 31% to 16%, nasal CPAP increased from almost 0% to 26% and surfactant administration increased from 0% to 53% in infants with hyaline membrane disease. Overall mortality decreased in infants with RD from 15.5% to 3.5%. CONCLUSIONS: The incidence of RD in infants admitted to neonatal units doubled over the last 30 years in a geographically defined neonatal population. This rise can predominantly be ascribed to infants with birth weight >2500 g and may reflect the corresponding increase in the rate of caesarean section.