Effect of preanesthetic medication on carbon dioxide tension in children with congenital heart disease.

Hypercarbia during the postoperative period following repair of congenital heart defects in children has been associated with acute pulmonary hypertension. Because decreases in respiratory rate (RR) and digital pulse oximetry (SpO2) have been observed after preanesthetic medication of similar children, it is possible that hypercarbia and pulmonary hypertension may be unappreciated risks in premedicated children during the preoperative period. As the first step in addressing this question, changes in transcutaneous and end-tidal PCO2 (PtcCO2 and PetCO2) were examined after preanesthetic medication of children prior to cardiac surgery. Forty-four children were randomly assigned to receive either intramuscular morphine, 0.2 mg/kg, and scopolamine, 0.01 mg/kg, or oral midazolam, 0.75 mg/kg, 1 hour before anesthetic induction. PtcCO2, PetCO2, SpO2, RR, and sedation score were monitored. Significant sedation occurred after both premedication regimens. Following morphine/scopolamine, PtcCO2 increased from 36 +/- 4 (mean +/- SD) to 43 +/- 6 mmHg (P < 0.01), PetCO2 increased from 35 +/- 3 to 40 +/- 5 mmHg (P < 0.01), SpO2 decreased from 93 +/- 2 to 91 +/- 4% (P < 0.01), and RR decreased from 30 +/- 10 to 24 +/- 7 breaths/minute (P < 0.01). After midazolam, PtcCO2 increased from 35 +/- 4 to 40 +/- 6 mmHg (P < 0.01), PetCO2 increased from 34 +/- 5 to 39 +/- 3 mmHg (P < 0.01), SpO2 decreased from 93 +/- 6 to 90 +/- 7% (P < 0.01), and RR decreased from 33 +/- 13 to 30 +/- 13 breaths/minute (P < 0.01). Clinically significant increases in PtcCO2 (> 45 mmHg) occurred in nine patients, including five with pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)