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Pulmonary and systemic hemodynamic effects of nitrous oxide in infants with normal and elevated pulmonary vascular
Insights
Nitrous oxide (N2O) caused mild decreases in heart rate, blood pressure, and cardiac index in infants after heart surgery. Unlike adults, N2O did not increase pulmonary vascular resistance in these pediatric patients.
Area of Science:
- Pediatric Cardiology
- Anesthesiology
- Critical Care Medicine
Background:
- Congenital heart disease repair often requires intensive care.
- Hemodynamic monitoring is crucial in infants post-cardiac surgery.
- Nitrous oxide's effects on pulmonary vascular resistance (PVR) in adults are well-documented but less so in infants.
Purpose of the Study:
- To investigate the hemodynamic effects of 50% nitrous oxide in infants following congenital heart disease repair.
- To compare the response in infants with normal versus elevated pulmonary vascular resistance index (PVRI).
Main Methods:
- 12 sedated infants undergoing mechanical ventilation were studied.
- Hemodynamic parameters were measured during 50% nitrogen (control) and 50% nitrous oxide.
- Measurements were repeated to ensure reproducibility.
Main Results:
- Heart rate decreased by 9%, mean arterial blood pressure by 12%, and cardiac index by 13%.
- These systemic hemodynamic changes were statistically significant but generally not clinically significant.
- No significant changes in pulmonary artery pressure or PVRI were observed in either group.
Conclusions:
- Nitrous oxide causes mild systemic depressant effects in infants, similar to adults.
- Crucially, nitrous oxide does not elevate pulmonary artery pressure or PVRI in infants, unlike in adults.
Abstract:
The hemodynamic response to 50% nitrous oxide was studied in 12 sedated but responsive infants in the intensive care unit following repair of their congenital heart disease. One-half of the infants studied had an elevated pulmonary vascular resistance index (PVRI greater than 3.5 Wood units). During mechanical ventilation with a fractional inspired O2 concentration (FIO2) of 0.5, hemodynamic parameters were measured after equilibration with 50% nitrogen and then after 50% nitrous oxide. The sequence was repeated once to assure reproducibility of the responses. Average heart rate decreased by 9%, mean arterial blood pressure decreased by 12%, and cardiac index decreased by 13% in both the elevated and normal PVRI groups each time nitrous oxide was given. Although statistically significant, these changes would not generally be clinically important except in infants with severely compromised cardiovascular reserve. In contrast, pulmonary artery pressure and PVRI were not significantly changed by administration of 50% nitrous oxide in either the group with normal PVRI or the group with preexisting elevated PVRI. We conclude that while these mild depressant effects of nitrous oxide on systemic hemodynamics in infants are similar to those previously reported in adults, in infants nitrous oxide does not produce the elevations in pulmonary artery pressure and pulmonary vascular resistance seen in adults.