Endogenous distress in ventilated full-term newborns with acute respiratory failure

The main rationale behind the continuous analgesia/sedation currently practiced in the treatment of neonates with severe respiratory failure in intensive care is an attempt at shielding the sick newborn from exogenous stress and pain caused by diagnostic and therapeutic interventions. Until now, however, the factors which influence endogenous, disease-related distress have been largely ignored.

We retrospectively studied the daily need for analgesics and sedatives (fentanyl, midazolam, pentobarbital, thiopental) of 40 full-term newborns with severe respiratory failure who had been ventilated for at least 48 h over an observational period of 2-5 days. Dosing of the analgesics and sedatives was based on a neonatal sedation score for ventilated infants. These daily amounts were converted to a normative comparative dose (analgesic/sedative need = ASN) and compared with the oxygenation index (OI) as a measure of the degree of pulmonary insufficiency.

Depending on the duration of ventilation, an increasingly close correlation between the ASN and the OI was detected: the index of correlation (r) was detected to be 0.65 on the second day, but increased up to 0.94 after 5 days. The subgroup of patients who had been ventilated for more than 3 days (n = 8) consistently showed a very high correlation, ranging from r = 0.86 to r = 0.94.

Our results indicate a direct relationship between severity of pulmonary failure (expressed as OI) and degree of disease-related distress (reflected by ASN). This supports the hypothesis that in full-term neonates under mandatory intensive care for severe respiratory failure, endogenous distress caused by the primary disease itself, in addition to exogenous distress caused by therapeutic and diagnostic interventions, is key factor for the determination of the required amount of analgesic and sedative drugs.