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Arterial to end-tidal carbon dioxide tension difference in children with congenital heart disease

J A Short1, S T Paris, P D Booker

  • 1Royal Liverpool Children's Hospital, UK.

British Journal of Anaesthesia
|September 28, 2001
PubMed

Insights

In children with congenital cyanotic heart disease, the difference between arterial and end-tidal carbon dioxide tension (PaCO2-PE'CO2) is affected by shunting and pulmonary hypoperfusion. Additional factors like pulmonary congestion can further increase this difference.

Area of Science:

  • Pediatric Cardiology
  • Respiratory Physiology
  • Critical Care Medicine

Background:

  • Congenital cyanotic heart disease involves right-to-left intracardiac shunting, adding venous blood to arterial circulation.
  • This shunting creates an obligatory difference between arterial and end-tidal carbon dioxide tension (PaCO2-PE'CO2).
  • The PaCO2-PE'CO2 difference is influenced by oxygen saturation, hemoglobin concentration, and PaCO2 levels.

Purpose of the Study:

  • To investigate factors influencing the clinically observed PaCO2-PE'CO2 difference in children with congenital cyanotic heart disease.
  • To compare predicted PaCO2-PE'CO2 differences with measured values in pediatric cardiac surgery patients.
  • To explore the impact of pulmonary hypoperfusion and ventilation-perfusion mismatch on PaCO2-PE'CO2.

Main Methods:

  • Studied 60 children undergoing cardiac surgery.
  • Compared predicted PaCO2-PE'CO2 differences with measured values.
  • Assessed the influence of oxygen saturation changes with increased fraction of inspired oxygen (FIO2).

Main Results:

  • Observed PaCO2-PE'CO2 values frequently exceeded predicted values, suggesting pulmonary hypoperfusion.
  • Pulmonary hypoperfusion did not fully explain the observed differences in all patients.
  • Significant improvement in oxygen saturation with increased FIO2 indicated ventilation-perfusion mismatch.

Conclusions:

  • Pulmonary hypoperfusion is a significant contributor to elevated PaCO2-PE'CO2 in these children.
  • Ventilation-perfusion mismatch, potentially due to pulmonary congestion from left-to-right shunts, also increases the PaCO2-PE'CO2 difference.
  • Multiple factors contribute to the PaCO2-PE'CO2 difference beyond simple intracardiac shunting.

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