Arterial-to-end-tidal carbon dioxide tension difference in children with congenital heart disease.
OBJECTIVE
This study estimated the arterial-to-end-tidal carbon dioxide tension difference (deltaPaCO2-PE'CO2) in children with congenital heart disease; evaluated whether hyperventilation can reduce this difference; and analyzed the relationship between the difference and the oxygen saturation (SaO2) and hemoglobin level.


METHODS
Prospective clinical study.


METHODS
Tertiary health care center.


METHODS
One hundred patients scheduled for correction of their underlying cardiac defect with either right-to-left or left-to-right intracardiac shunts were divided into 4 groups (n = 25 each): (1) N1, cyanotic with severe pulmonary artery hypertension; (2) N2, cyanotic with normal or decreased pulmonary artery pressure (PAP); (3) N3, acyanotic with normal or mild increases in PAP and severe increases in pulmonary blood flow (PBF); and (4) N4, acyanotic with normal PAP and normal or mild increase in PBF.


METHODS
All the patients received the same anesthetic regimen. The initial settings for tidal volume, respiratory rate, and inspiratory-to-expiratory (I:E) ratio were 10 mL/kg, 15 to 30 breath/min, and inspired time 40% of the total respiratory period with a 10% end-inspiratory pause. After the measurement of oxygen saturation, PO2, Hb, and deltaPaCO2-PE'CO2, all the children were hyperventilated (tidal volume: 14-15 mL/kg, respiratory rate: 5-6 breaths/min more than the initial rate, I:E ratio: same) to observe its effects on the deltaPaCO2-PE'CO2.


RESULTS
The deltaPaCO2-PE'CO2, when predicted from the oxygen saturation, hemoglobin concentration, and PaO2, was found to be greater than the observed value in the first 3 groups (p < 0.001); whereas in group N4 these 2 values were comparable. It was also found that the gradient was higher when there was a decrease in SaO2 and an increase in the hemoglobin level. After hyperventilation, in groups N1 and N3, deltaPaCO2-PE'CO2 was decreased when compared with their baseline values; this reduction was not as much as predicted (p = 0.363 and 0.236, respectively). However, in groups N2 and N4 posthyperventilation, the deltaPaCO2-PE'27 CO2 was decreased significantly below their baseline measurements. These decreases were as much predicted.


CONCLUSIONS
The deltaPaCO2-end-tidal carbon dioxide (PE'CO2) can be increased both in cyanotic and acyanotic children. Increased PAP is as important as increased PBF or right-to-left shunting in producing disorders in carbon dioxide homeostasis. Hyperventilation is of little use in reducing deltaPaCO2-PE'CO2 in children with high PAPs and pulmonary hyperperfusion.
Choudhury
Minati
M
Department of Cardiac Anaesthesia, Cardiothoracic and Sciences Center, All India Institute of Medical Sciences, New Delhi, India. minatichoudury2002@yahoo.co.in
Kiran
Usha
U
Choudhary
Shiv Kumar
SK
Airan
Balram
B
D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood*; D002675:Child, Preschool; D006330:Heart Defects, Congenital / Q000097:blood* / Q000503:physiopathology; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007223:Infant; D010101:Oxygen Consumption / Q000502:physiology; D011379:Prognosis; D011446:Prospective Studies; D011669:Pulmonary Wedge Pressure / Q000502:physiology; D012720:Severity of Illness Index; D013990:Tidal Volume / Q000502:physiology
D006454:Hemoglobins; D002245:Carbon Dioxide