Related Experiment Videos
Hemodynamic responses to PaCO2 in children after open heart surgery
1Intensive Care Unit, IWK Hospital for Children, Dalhousie University, Halifax, NS, Canada.
Insights
In children after heart surgery, moderate hypercarbia (high carbon dioxide levels) and its correction significantly impact hemodynamics. Minor CO2 changes, however, show no significant effect on cardiac index.
Area of Science:
- Pediatric critical care medicine
- Cardiovascular physiology
- Respiratory management
Background:
- Ventilator-dependent children post-open heart surgery are susceptible to acute alterations in partial arterial carbon dioxide pressure (PaCO2).
- Hemodynamic stability is crucial in this patient population, yet the precise effects of PaCO2 variations remain incompletely understood.
Purpose of the Study:
- To investigate the hemodynamic consequences of acute changes in PaCO2 in pediatric patients recovering from open heart surgery.
- To determine the threshold of PaCO2 alteration that elicits significant hemodynamic responses in this vulnerable group.
Main Methods:
- Studied ten ventilator-dependent children after open heart surgery.
- Monitored end-tidal CO2 and PaCO2 levels, with five children experiencing inadvertent hypercarbia (PaCO2 > 50 torr).
- Analyzed changes in cardiac index (CI), oxygen delivery, pulmonary pressure, systemic vascular resistance, and right ventricular stroke work index.
Main Results:
- Significant hemodynamic alterations, including changes in CI and systemic vascular resistance, occurred in children with moderate hypercarbia and during its correction.
- No significant hemodynamic changes were observed when PaCO2 alterations were less than or equal to 12 torr (range 28-50 torr).
- Larger PaCO2 reductions were noted in the hypercarbic group compared to others (25 vs. 12 torr).
Conclusions:
- Acute alterations in PaCO2 ≤ 12 torr do not significantly affect CI in children post-open heart surgery.
- Moderate hypercarbia and its correction to a PaCO2 of 30 torr are associated with significant central hemodynamic effects.
- Commonly monitored physiological variables may not reflect significant hemodynamic changes despite large PaCO2 variations.
Abstract:
We studied the hemodynamic effects of acute alterations in PaCO2 in ten ventilator-dependent children after open heart surgery. Despite end-tidal CO2 monitoring, five children inadvertently developed PaCO2 greater than 50 torr during the study. Increasing and decreasing PaCO2 in these children resulted in significant parallel changes in cardiac index (CI), oxygen delivery, physiologic shunt, mean pulmonary pressure, and right ventricular stroke work index, and inverse changes in systemic vascular resistance index (p less than .01). No significant hemodynamic changes were observed with alterations in PaCO2 in children whose PaCO2 remained less than 50 torr. These findings are partly related to significantly larger reductions in PaCO2 which occurred in the hypercarbic children compared to the others (25 vs. 12 torr; p less than .001). Heart rate, mean arterial BP, and venous filling pressures did not change significantly in either group. We conclude that mean alterations in PaCO2 less than or equal to 12 torr (range 28 to 50) have no significant effect on CI in children after open heart surgery. However, moderate hypercarbia and its correction to a mean PaCO2 of 30 torr are associated with significant effects on central hemodynamics. Moreover, no significant changes in the commonly monitored physiologic variables were observed despite large variations in PaCO2.