Severe obstructive pulmonary disease results in increased airway resistance, reduced expiratory flow rates, and high residual lung volumes. There is a point at which the expiratory airway obstruction and lung hyperinflation become so severe that the chest wall cannot physically expand to accommodate a normal tidal volume, resulting in restrictive physiology superimposed on obstructive disease. This condition is usually refractory to medical management and substantially limits daily activity. This patient’s age and lack of other significant systemic illness allowed her to be considered a transplant candidate.

Chronic obstructive pulmonary disease (COPD) (36%), idiopathic pulmonary fibrosis (21%), emphysema secondary to α₁-antitrypsin deficiency (7%), and cystic fibrosis (16%) are the most common obstructive disorders in adults undergoing lung transplantation. At one time, concerns about mediastinal displacement and profound ventilation/perfusion mismatch secondary to hyperinflation of the remaining native lung prevented surgeons from attempting SLT for emphysema. However, clinical experience has demonstrated that many emphysemic patients can be successfully treated by SLT. Due to the severe shortage of organs for transplant, single-lung procedures have been advocated as a means to increase the number of recipients. However, with 5-year survival rates after SLT approaching only 50% and increasing experience suggesting that bilateral lung transplantation (BLT) for COPD is associated with improved functional outcomes and improved long-term survival, BLT emerged as a formidable (alternative) approach to treat this patient population. The improved survival with BLT may possibly be due to the later development of bronchiolitis obliterans syndrome (BOS) as well as a trend for higher quality of life score compared with SLT. Nonetheless, although transplantation may improve the quality of life for patients with severe COPD, the decision for SLT or BLT remains controversial and is based on the individual situation taking into account regional organ allocation policies, individual center experience, and organ availability.

The first successful (i.e., the patient left the hospital) SLTs were performed in 1983 for idiopathic pulmonary fibrosis. Since that time, the procedure has been applied to patients suffering from various end-stage pulmonary diseases (Table 4.1). In general, the underlying
disease processes produce lung dysfunction that can be broadly characterized as obstructive, restrictive, infectious (e.g., cystic fibrosis and bronchiectasis), or vascular. As of 2008, most SLTs have been performed for obstructive lung disease, followed by idiopathic pulmonary fibrosis. The most common indications for BLT are cystic fibrosis and obstructive lung disease.

Reflecting a loss of lung parenchymal elasticity and compliance, end-stage restrictive disease is characterized by profoundly reduced lung volumes and diffusing capacity but relative preservation of ventilatory flow rates. Comparison of flow-volume loops representing obstructive and restrictive diseases is shown in Figure 4.1. The underlying disease process also tends to obliterate pulmonary microvasculature, thereby chronically increasing vascular resistance, producing pulmonary hypertension, and predisposing to cor pulmonale. Most patients with restrictive disease are good candidates for an SLT because the stiff, vasoconstricted native lung will receive relatively little ventilation and perfusion and can therefore usually be left without compromising the transplanted lung.

Infectious lung disease such as cystic fibrosis is the most frequent indication for lung transplantation in patients younger than 18 years. Characterized by chronic infection and the production of copious purulent secretions, patients with cystic fibrosis primarily exhibit obstructive functional abnormalities with increased airway reactivity. Under most circumstances, residual lung volumes and functional residual capacity are increased and bronchodilators have little effect on expiratory flow rates. Because of potential infectious cross-contamination of the transplanted lung, chronic infectious disease represents a contraindication to SLT. However, SLT with contralateral pneumonectomy has been performed as an alternative solution.

Pulmonary vascular disease with severe pulmonary hypertension and right ventricular dysfunction has also emerged as an indication for transplantation. Pathologically, severe PA hypertension can result from idiopathic proximal vascular processes such as persistent pulmonary hypertension (PPH) or secondary to chronically increased pulmonary blood flow (e.g., left-to-right intracardiac shunt, leading to Eisenmenger syndrome) or pulmonary venous hypertension from left-sided heart diseases. Pulmonary hypertension may precipitate chronic hypoxemia via an intracardiac defect that allows for development of a right-to-left shunt. Improved medical therapy for PPH, particularly with continuous long-term intravenous prostacyclin infusions or sildenafil, has affected the numbers of patients undergoing lung transplantation for this disease.

Controversy exists with respect to choice of SLT versus BLT for patients with idiopathic pulmonary arterial hypertension (IPAH). Because a native lung can usually be left intact without compromising a transplanted lung (which will receive most of blood flow), some patients with pulmonary arterial vascular disease may be reasonable candidates for SLT, with concurrent repair of any cardiac anomalies. Early reports indicated poorer functional recovery and higher mortality after SLT versus BLT for PPH. Some reports suggest the earlier manifestation of BOS in patients after SLT versus BLT, and although survival curves diverge 3 years after transplantation, controversy remains whether or not procedure type is the main cause. Some centers have adopted BLT as the mainstay of treatment for patients presenting with IPAH.

Although the first human lung allograft was performed in 1963, transplantation of one or both lungs did not emerge as a viable therapeutic option for patients with end-stage lung disease until the 1980s. The ultimate emergence of this procedure can be largely attributed to advances in the prevention and treatment of airway complications, infections, and rejection. Since initiation of an international registry for lung transplantation in the mid-1980s, the number of procedures reported yearly rose sharply, until beginning to slow in 1993. To date, the highest yearly total was 3,725 in 2011. Despite this volume, the number of patients awaiting lung transplantation continues to exceed the limited donor supply. As of the 2014 international registry, 47,647 lung transplantations had been reported worldwide.

In general, patients with severe end-stage lung disease are considered candidates for transplantation when their life expectancy is less than 2 to 3 years. They have minimal disease of other organ systems, and they are mentally and psychologically capable of following strict regimens for rehabilitation and immunosuppressive therapy. These criteria contribute to a high (>80%) likelihood of surviving the lung transplantation for at least 90 days and 5-year posttransplant survival from a general medical standpoint. Specific criteria, including age, are dependent on the type of lung disease and whether the planned procedure is SLT or BLT. Recent data reveal that the age of lung transplant recipients is increasing with approximately 35% now 60 years of age and older compared to 15% in 1998. The average age of the recipient is 35.5 years. In contrast to inclusion criteria formulated when lung transplantation was in its infancy, concomitant steroid therapy, previous intrathoracic surgery, mechanical ventilation, and right ventricular failure are no longer considered absolute contraindications.

SLT is often preferred because of the extreme shortage of donor organs; however, as experience increases with BLT and the improvement in outcomes compared with SLT, many centers are performing BLT more frequently than SLT. The only absolute contraindication to SLT is infectious lung disease (e.g., cystic fibrosis and bronchiectasis) because leaving the native lung could endanger the long-term viability of the transplanted lung. As noted earlier, severe emphysema was once thought of as a contraindication to SLT because of the probability of mediastinal shift and marked ventilation mismatch between the highly distensible native lung and the graft. This is only rarely of clinical significance, and it is now accepted that SLT can be successfully performed in patients with obstructive disease. Although SLT is technically easier and advocated for more difficult recipients, such as those with prior thoracic surgery or coexisting illnesses, functional improvements are often better with BLT. In addition, the status of the donor lungs further influences the decision of whether to perform a single or bilateral procedure. Finally, transplantation of two lobes from two living related donors for patients with inflammatory disease who are unlikely to survive the wait for a cadaver donor is gaining acceptance. From a practical standpoint, the decision to perform an SLT or a BLT has little impact on preoperative management because both procedures necessitate the same level of preparation.

It is extremely important that anesthesiologists be broadly familiar with the surgical methods because manipulation of the heart and lungs at specific points during the transplantation can produce marked cardiopulmonary disturbances. Ideally, the anesthesiologist should anticipate these changes and adapt the anesthetic management accordingly.

SLT is usually performed in the lateral decubitus position through a thoracotomy incision, often with the upper leg and pelvis angled to allow groin exposure for potential femoral cannulation and CPB. In contrast, bilateral sequential lung transplantation is usually performed with the patient supine through a “clamshell” incision (bilateral anterior thoracotomies with or without transverse sternotomy). For both SLT and BLT, intermittent single-lung ventilation is required during dissection of the native lung to be removed and implantation of the graft. Once stable single-lung ventilation is established, dissection of the lung to be transplanted is initiated with isolation of the PA. To assess the cardiopulmonary response to diverting the entire cardiac output through one lung, progressive temporary occlusion of the vessel is first performed manually; if well tolerated, the vessel is then clamped and stapled. After ligation of the PA, the pneumonectomy is completed. Implantation of the graft begins with anastomosis of the airway. In the past, the bronchial anastomosis was wrapped with an omental pedicle, mobilized through a small abdominal incision in an effort to improve blood supply to the airway and promote healing. However, the use of a “telescoping” bronchial anastomosis has now largely obviated the need for omental wrapping. The PA branch is then attached to the graft, followed by anastomosis of a cuff of the left atrium containing the pulmonary veins. The implanted lung is then partially inflated, the left atrial cuff and pulmonary veins de-aired, and circulation to the organ restored. If the attempt to establish adequate hemodynamics and oxygenation after reperfusion of the transplanted lung is unsuccessful, this is the time to consider using extracorporeal membrane oxygenation (ECMO) or CPB. In a sequential BLT, this is often the point in the case where the decision may be made to place the patient on extracorporeal support prior to attempting to transplant the second lung. The use of extracorporeal support for BLT often varies by institutional and patient factors. If an en bloc technique for BLT is used, CPB is required. Additional surgical technique for BLT is described in the following text.

Patients presenting for SLT with chronic PPH of primary or secondary etiology often exhibit severe compromise of the right ventricular function. To avoid additional right ventricular compromise, many institutions choose to institute partial normothermic CPB during SLT for PPH or in patients with severe pulmonary hypertension and right ventricular dysfunction secondary to restrictive or obstructive disease. Cannulation is typically through the femoral artery and the right atrium unless simultaneous correction of an intracardiac defect is planned. In such patients, conventional aortic and single- or double-stage atrial cannulation are performed. Implantation of the lung is otherwise performed in the same manner as described earlier.

BLT was first described by the Toronto Lung Transplant Group in the mid-1980s as en bloc implantation of both lungs simultaneously. The procedure is performed through a median sternotomy using hypothermic CPB, cardioplegic cardiac arrest, and single tracheal (or double bronchial) anastomosis of the trachea and main PA. Although the procedure initially produced encouraging results, considerable limitations related to technical complexity, morbidity, mortality, and application to many patients with end-stage lung disease soon became apparent. Not surprisingly, use of the procedure declined sharply and has now been largely replaced by the bilateral sequential implantation technique, which does not uniformly require hypothermic CPB. Introduced in 1990, bilateral sequential (or bilateral single) lung transplantation has become the surgical procedure of choice when replacement of both lungs is necessary. According to the 2014 international registry, approximately 75% of the transplants performed in 2012 were BLTs. As noted earlier, in contrast to SLT, bilateral sequential lung transplantation procedures are performed in the supine position. In general, the procedure can be regarded as having two phases. First, the most severely compromised lung (as determined by preoperative ventilation/perfusion lung scanning) is removed during ventilation of the “good” contralateral lung. Implantation is achieved through a bronchial anastomosis as with an SLT. The second lung is then removed and transplanted during ventilation of the new lung alone. As noted
earlier, if there is hemodynamic or ventilatory instability during ventilation of the new lung alone, extracorporeal support may be instituted prior to implanting the second lung.