Anästhesiologische Aspekte der Schwangerschaft und Entbindung bei einer Patientin nach modifizierter Fontan-Operation

Zusammenfassung

Es wird über die Schnittentbindung einer 20jährigen Patientin berichtet, die sich wegen einer Tricuspidalatresie mit funktionell univentrikulärem Herzen einer modifizierten Fontan-Operation unterzogen hatte. Die Kreislaufverhältnisse nach einer solchen operativen Korrektur zeichnen sich durch eine weitgehend nicht-pulsatile, passive Pulmonaldurchblutung unter Umgehung des rechten Ventrikels aus. Die Schnittentbindung wurde für die 32. Schwangerschaftswoche geplant. Die Narkose wurde unter invasivem Monitoring der zentralvenösen und arteriellen Drücke mit 24 mg Etomidat, 1,5 mg Norcuron und 75 mg Succinylcholin eingeleitet. Bis zur Entbindung wurde die Narkose mit 0,5–0,7% Halothan ohne Lachgas unterhalten. Die Entbindung erfolgte 8 min nach Narkoseeinleitung bei normalen Apgar-Werten. Die Anästhesie wurde mit Fentanyl und Midazolam sowie 50% Lachgas fortgeführt. Der postoperative und postpartale Verlauf war bis auf einen oberflächlichen Wundinfekt komplikationslos. Dieser Fallbericht zeigt, daß Patientinnen nach einer modifizierten Fontan-Operation die hämodynamische Belastung einer Schwangerschaft ohne Komplikationen tolerieren können und die Funktion des rechten Ventrikels keine unabdingbare Voraussetzung für eine erfolgreiche Entbindung darstellt. Da viele der inzwischen einer Fontan-Operation unterzogenen Patientinnen heute in einem gebärfähigen Alter sind, sollten Anästhesisten mit der Problematik der Fontan-Zirkulation vertraut sein, um peripartal die Kreislaufhomöostase unter funktionellem Ausschluß des rechten Ventrikels aufrechterhalten zu können.

Abstract

The number of patients with congenital cyanotic heart disease who reach child-bearing age is increasing. This is partly a consquence of the high long-term survival and the haemodynamic benefits resulting from the Fontan procedure, which is used for the definitive palliation of such cyanotic heart disease as tricuspid atresia and single ventricle. However, so far little experience has been recorded with pregnant patients who have undergone right ventricular exclusion procedures. The particular physiology of a univentricular heart and a passive, non-pulsatile blood flow through the lungs has significant implications for the anaesthetic obstetric management of these patients. We report a case of successful pregnancy and caesarean delivery after a modified Fontan procedure.

Case report. The patient was a 30-year-old pregnant woman with a singleton pregnancy. At the age of 20, after four palliative shunt operations, she had undergone a modified Fontan operation due to tricuspid atresia with a single ventricle, d-transposition of the great arteries, pulmonary atresia and a single atrium. Following the Fontan repair, she initially suffered from intermittent Wolff-Parkinson-White syndrome and isorhythmic AV dissociation. The pregnancy was uneventful, and caesarean section was scheduled for 32 weeks' gestation. Because of the increased risk of thrombosis, the patient was treated with s.c. heparin preoperatively; for this reason, epidural anaesthesia was excluded, though it may otherwise be preferred for such patients. Amoxicilline was used to prevent endocarditis. At the date of caesarean delivery her body weight was 54 kg and boy height, 155 cm. Before induction of anaesthesia, a central venous and a radial artery catheter were placed for invasive pressure monitoring. An exaggerated left lateral tilt position was used to avoid aortocaval compression. After careful preoxygenation, anaesthesia was induced with 24 mg etomidate, 1.5 mg norcuronium, and 75 mg succinylcholine. Halothane 0.5–0.7% in oxygen was used during the first few minutes of surgery. Central venous pressure under mechanical ventilation was 20 mmHg, while the heart rate varied between 70 and 90 bpm. Delivery was accomplished 8 min after the induction of anaesthesia. The Apgar scores after 1 and 5 min were 9 and 10, respectively. Anaesthesia was continued with fentanyl, midazolam and nitrous oxide 50%. The remainder of surgery was unevenful. The child is now 5 years old and healthy. The mother has a near-normal activity level and does not need any help to care for her child.

Discussion. After a modified Fontan repair, i.e. atriopulmonary or total cavopulmonary anastomosis, the pulsatile pulmonary blood flow is converted to a passive, non-pulsatile blood flow that depends critically both on the pressure gradient between right (RAP) and left atrial pressure (LAP) and on pulmonary vascular resistance (PVR). Thus, the maintenance of an adequate transpulmonary pressure gradient and avoidance of an increase in PVR are of major importance for the obstetric anaesthetic management in patients who have undergone right ventricular exclusion procedures. Impairment of venous return caused by slight caval compression or high airway pressure may reduce cardiac output more critically than in patients with a normal circulation.

Conclusion. This case demonstrates that the haemodynamic consequences of pregnancy and of caesarean delivery under general anaesthesia can be tolerated in post-Fontan patients despite the absence of a contractile pulmonary ventricle.