Objective: Surfactant replacement therapy for the neonatal respiratory distress syndrome has shown beneficial effects on lung function and survival. Recently, rapid fluctuations of haemodynamics and cerebral perfusion following surfactant instillation have been described and an association with the development of intraventricular haemorrhage has been proposed. Therefore, alternative methods of surfactant therapy that reduce the effects on cerebral perfusion have to be explored. Does instillation of surfactant influence blood pressure and cerebral blood flow in rabbits with severe respiratory failure? Can nebulisation of surfactant prevent these adverse effects on blood pressure and cerebral blood flow?
Interventions: Surfactant (Alveofact, 100 mg/kg body weight) was nebulised using the MiniNEB nebuliser, or instilled, in 12 rabbits with severe respiratory failure induced by lung lavage. Assessed were blood gasses, mean arterial blood pressure (MABP) and cerebral blood flow over the left carotid artery, using ultrasonic transit-time flow probes.
Results: Partial pressure of oxygen in arterial blood increased quickly after instillation, from 8.7 +/- 1.3 to 24.9 +/- 6.4 kPa after 15 min, and increased gradually during nebulisation from 8.0 +/- 0.5 to 24.5 +/- 4.6 after 120 min. After instillation, MABP decreased 22 +/- 5% (in 8 min) and cerebral blood flow dropped even more: 64 +/- 9% within 8 min. During nebulisation, MABP did not change significantly and cerebral blood flow decreased gradually, 31 +/- 14% over 90 min.
Conclusions: Surfactant instillation was followed by a rapid decrease in MABP and an even more pronounced drop in cerebral blood flow, while during nebulisation MABP did not change and cerebral blood flow decreased less and more gradually.