Browse the corpus

The bidirectional Glenn (BDG) and hemi-Fontan are the types of surgical techniques used to create superior cavopulmonary anastomosis, the second stage repair in Fontan completion. This activity reviews pertinent anatomy and highlights the role of the interprofessional team in managing patients who undergo the bidirectional Glenn procedure. Objectives: Identify the indications of the bidirectional Glenn procedure. Apply the bidirectional Glenn procedure technique. Identify the potential complications of the bidirectional Glenn procedure. Access free multiple choice questions on this topic.

The bidirectional Glenn (BDG) and hemi-Fontan are surgical techniques used to create superior cavopulmonary anastomosis, the second stage repair in Fontan completion (see Image. Superior Cavopulmonary Anastomosis). They are performed in patients with an anatomic or functional single ventricle. Whether it is right or left, the single ventricle must, therefore, provide blood supply to the higher resistance systemic circulation and the lower resistance pulmonary circulation until surgical correction is undertaken. The BDG procedure, or hemi-Fontan, helps eliminate volume load on the single ventricle and simplifies the operative procedure at Fontan. Several centers have reported decreased mortality and morbidity of the Fontan procedure in those who have undergone BDG or hemi-Fontan. All patients with a single ventricle must eventually undergo a Fontan procedure to achieve separation of their systemic and pulmonary circulations. A patient with a completed Fontan procedure has systemic venous return diverted to the pulmonary circulation, driven by central venous pressure and affected by intrathoracic pressure changes and systemic ventricular relaxation. As of 2018, there are an estimated 50,000 to 70,000 patients with a Fontan circulation, 40% of these patients older than 18.[1] About 1000 Fontan procedures are performed annually in the United States.[2]

A traditional bidirectional Glenn procedure, undertaken to balance pulmonary and systemic blood flow via a shunt, has a mortality rate of less than 2 percent.[16] NPC-QIC data revealed that postoperative complications occurred in approximately 30% of patients and included emergency cardiac catheterization (9%), new onset of neurologic deficit (9%), reoperation (6%), cardiac arrest (3%), and feeding difficulties that necessitated fundoplication or gastrostomy tube placement (15%).[17] Multivariate analysis revealed that the most common risk factors for postoperative complications included the presence of mitral stenosis, aortic atresia, female gender, and failure to thrive perioperatively. In a smaller-sized patient, reduced SVC size can make cannulation challenging and lead to a gradient at the cannulation site after tying a purse-string suture. A large-bore venous cannula in the SVC in such a patient may impede cerebral venous drainage and lead to neurologic dysfunction. Factors that exacerbate postoperative blood loss in this population include age less than 2 years, reoperation, use of aspirin, hypoxemia, and deep hypothermic bypass. Almost all patients undergoing a BDG will need a repeat sternotomy, with an increased risk for blood loss due to mediastinal adhesions and CPB-induced arrhythmias. Anesthesiologists and surgeons should discuss the need for antifibrinolytic agents, multiple large-bore intravenous access for administering blood products, and the application of external cardioversion or defibrillation pads. In addition, a CPB circuit should be primed, and heparin should be available in case of an emergent need for a bypass.

Factors that exacerbate postoperative blood loss in this population include age less than 2 years, reoperation, use of aspirin, hypoxemia, and deep hypothermic bypass. Almost all patients undergoing a BDG will need a repeat sternotomy, with an increased risk for blood loss due to mediastinal adhesions and CPB-induced arrhythmias. Anesthesiologists and surgeons should discuss the need for antifibrinolytic agents, multiple large-bore intravenous access for administering blood products, and the application of external cardioversion or defibrillation pads. In addition, a CPB circuit should be primed, and heparin should be available in case of an emergent need for a bypass. Following the completion of the BDG, exacerbated hypoxemia is one of the most common postoperative complications caused by a suboptimal ventilation strategy or diminished PBF. If oxygenation does not improve the following optimization of volume status and ventilation strategy, collateral vessels from the upper body to the systemic circulation should be investigated. These vessels may require coil embolization in a persistently hypoxemic patient. Early extubation is recommended in these patients as spontaneous ventilation will augment cardiopulmonary-cerebral circulation, and PaO2 and PaCO2 should be optimized. Elevating the head of the bed and maintaining the neck in a neutral position will enhance cerebrovenous drainage and prevent hypoxemia. Systemic hypertension can occur in patients following a BDG as the cerebral circulation requires a higher venous pressure following surgical intervention. Following the BDG, cerebral venous pressure is equal to PA pressure and elevated to a mean of 12 to 18 mmHg. Hypertension can result from the body's aim to maintain cerebral perfusion pressure. Pleural effusions are one of the important complications postoperatively that can prolong the duration of hospitalization and are known to happen in 9% of children. Though the cause remains uncertain, increased left-to-right shunting from some collaterals can be the cause in some cases. Sometimes, pulmonary arteriovenous (AV) fistulas can be formed in children who have undergone the BDG procedure and Kawashima operation, as these exclude hepatic venous circulation to the lungs on the first pass, suggesting a hepatic factor as a cause for pulmonary AV fistulas, which can cause desaturations.

Pleural effusions are one of the important complications postoperatively that can prolong the duration of hospitalization and are known to happen in 9% of children. Though the cause remains uncertain, increased left-to-right shunting from some collaterals can be the cause in some cases. Sometimes, pulmonary arteriovenous (AV) fistulas can be formed in children who have undergone the BDG procedure and Kawashima operation, as these exclude hepatic venous circulation to the lungs on the first pass, suggesting a hepatic factor as a cause for pulmonary AV fistulas, which can cause desaturations. Patients with failing BDG physiology develop elevated venous pressures that reduce PBF, impair oxygenation, and inhibit cerebral venous drainage. Decreased cerebral perfusion can result from high cerebral venous pressures in low systemic blood pressure. The failing Glenn circuit is often caused by atrioventricular valve regurgitation, leading to reduced cardiac output. Jolley et al identified seizures, cerebral hemorrhage, and embolic stroke as common complications in this population. If a BDG patient requires extracorporeal membrane oxygenation (ECMO) support, increased morbidity and mortality are associated with renal injury, neurologic injury, and persistent acidosis.[18][19] Analysis from the NPC-QIC revealed that the use of ECMO does not predict prolonged hospital stay following BDG.[20]

Experienced institutions have excellent outcomes following the BDG, with operative survival over 96%.[29] Infants with a stage 1 repair involving a Sano modification may require an earlier BDG repair at 3 months but have not shown increased morbidity or mortality.[30] There has been some push to encourage an earlier BDG repair to reduce interstage mortality.[31] Jaquiss et al reported on an earlier BDG in 85 patients with HLHS. Patients were divided into surgical intervention at 4 months (33 patients) and greater than 4 months (52 patients) and compared for preoperative and postoperative variables. Six-year survival and functional assessment were not different between the 2 groups, although the group of younger patients exhibited more profound hypoxemia and required longer hospitalization. Ultimately, the younger group exhibited a similar outcome following Fontan's completion. Carlo et al investigated 92 patients 30 days following BDG repair; 8 of these patients died, and 3 required a cardiac transplant.[32] These complications were associated with severe tricuspid valve regurgitation and low weight at the time of BDG.[30]

A good operating team, along with pediatric cardiac anesthesiologists, OR nurses, and perfusionists running the cardiopulmonary bypass, are required for the procedure to go smoothly. There should be a good handoff between the OR team and the ICU team that receives the patient after the surgery. An interprofessional ICU team of nurses trained in cardiac intensive care, cardiac intensivists, and respiratory therapists is vital in taking good care of the patients post-operatively.

Monitoring of these children at every step is important from the time of procedure until the child gets discharged from the hospital. The teamwork of the above-mentioned personnel helps to minimize prevent, and treat the complications that arise during hospitalization.