Authors
A Robertson1; 1 Great Ormond Street Hospital for Children, UK Objective
Patients with a combination of vein of Galen malformation and congenital cardiac disease present a challenge in the setting of cardiopulmonary bypass to the extent that it has been reported only once before. Other case reports describe poor outcome without intervention or a hybrid peratrial approach with the express intent of avoiding CPB. A further case series recommended “conservative management” until the VGM had been successfully eradicated. We present the case of a 23 day old female neonate, weighing 2.8 kilograms with dissection of the patent ductus arteriosus and pulmonary artery in combination with VGM. The patient had a background of suspected Loeys-Dietz syndrome manifesting as a dilated ascending aorta. This was presumably the main contributor to the development of the vascular dissection, in combination with circulatory hyperdynamism. The aneurysm’s false lumen extended from its origin in the inferior aspect of the proximal aortic arch. Method
The CPB strategy was to provide arterial blood flow at a cardiac index high enough to compensate for the VGM shunt. A Hoffman gate clamp was used on the CPB circuit venous drainage line. pH-stat blood gas management was used to maintain high blood flow to the head during cooling to maximise cerebral protection. It was considered that the use of alpha-stat blood gas management during cooling may have restricted cerebral arteriolar blood flow distal to the VGM thus increasing the shunt. The pH-stat-induced increased CO2 blood content also served to potentially restrict the flow across the PDA due to increased pulmonary vascular resistance, thereby helping to maintain systemic perfusion. The partial restriction of the venous drainage line was in order to maintain a positive CVP. It was feared that decompression of the central veins would increase the cerebral shunt pressure gradient, and therefore shunt flow. Ventilation was maintained because the CPB strategy of keeping the heart full. Results
The mean central venous pressures were 6.0 mmHg and 6.9 mmHg during cooling and rewarming respectively. Mean arterial pressures for the corresponding periods were 36.4 mmHg and 39.2 mmHg. The resultant mean cerebral perfusion pressures were 30.4mmHg and 32.3mmHg. The patient remained ventilated on minimal settings until the aortic cross clamp was placed and cardioplegia delivered immediately prior to initiation of deep hypothermic circulatory arrest (DHCA). During cooling, the flank and head NIRS rose from baseline values of 78% and 55% respectively to 96% and 81% at the start of DCHA. Surgical repair of the lesion took place during a DHCA period of 26 minutes. The nadir NIRS values at the end of DHCA were 51% and 58%. Following reinstitution of CPB the same strategies were employed as for the cooling phase of the procedure. The patient was weaned from CPB successfully and extubated 72 hours post-surgery and showed no apparent signs of neurological deficit. Conclusion
Placing a patient with VGM onto CPB is considered high risk, if not contraindicated. The danger is that systemic arterial blood is shunted across the VGM in such a significant quantity so as to reduce cerebral and somatic perfusion to the extent that hypoxic ischaemic injury is induced. Although PDA and MPA dissection is rare, we postulate that VGM patients with other congenital cardiac lesions requiring surgical correction could potentially benefit from the perfusion strategy we describe here. Although VGM may be successfully treated prior to any cardiac surgery, a known complication of endovascular interventions to occlude VGM in the setting of cardiac septal defects is paradoxical embolization. A protective CPB strategy to facilitate intra-cardiac repair prior to endovascular VGM intervention may be advantageous. 
