Introduction: Pregnancy can severely exacerbate pre-existing cardiac disease leading to possible decompensation in the mother and a high risk of foetal death. We describe the anaesthetic management of 5 patients who underwent cardiopulmonary bypass (CPB) to replace the aortic valve. In all cases the relative risks of continuing or terminating the pregnancy or undergoing valve surgery were discussed with the patients and the risks explained.
Method: All patients underwent standard perioperative care and monitoring. During surgery the foetal heart rate and blood flow in the uterine arteries, foetal aorta, ductus venosus and cerebral arteries were measured by either trans-vaginal or trans-abdominal ultrasound. CPB utilized a standardized technique of pulsatile flow, mean arterial pressures of 65 mmHg, maternal haemoglobin >10gm/dL and mild hypothermia of 35°C. Anaesthesia was maintained with high dose fentanyl and propofol infusions. A low dose GTN infusion to promote uterine blood flow and prevent uterine contractions was used in all cases.
Results: All patients were extubated within 8 hours of surgery and had an uneventful postoperative course. All patients maintained normal uterine blood flow during CPB. Only case 3 demonstrated signs of severe foetal distress during CPB despite increasing both flow and maternal blood pressure and the foetus died 10 days postoperatively. In case 5 the foetus tolerated CPB well and appeared normal for the first 4 days. It died of an unknown cause on day 5.
Discussion: The challenge of these cases is to understand the physiological changes of normal pregnancy, maintain maternal well being during surgery and CPB and to manipulate maternal physiology to ensure foetal well being. Despite case reports and reviews , the effects of cardiopulmonary bypass on the foetus is still poorly understood.
1 Strickland RA, Oliver WC, Chantigen RC, et al. Anaesthesia, cardiopulmonary bypass and the pregnant patient. Mayo Clin Proc 1991; 66: 411.