Lung Transplantation: Anesthetic Implications

Introduction^1,2

• End-stage lung disease may be due to parenchymal disease (obstructive, restrictive, or infectious) or pulmonary vascular disease (Table 1).

• Lung transplantation is the only therapeutic option for end-stage lung disease
  • However, it has the lowest long-term survival of all solid organ transplants.²
  • PGD is leading cause of death after transplantation.
• Prognosis after lung transplantation:
  • More than 50% risk of death within 2 years from lung disease if transplant is not performed
  • More than 80% likelihood of surviving more than 90 days posttransplant
  • More than 80% likelihood of surviving 5 years posttransplant from an overall medical perspective, assuming the graft remains functional

Surgical Approaches³

• Patients may undergo single-lung or double-lung transplantation.
  • Single lung: chronic obstructive pulmonary disease (COPD), other interstitial lung diseases; these patients may also undergo double lung transplantation
  • Double lung: infectious/suppurative lung disease, pulmonary arterial hypertension
  • Older patients may benefit from single lung transplantation due to shorter operative time
• Surgical approach may involve unilateral or bilateral thoracotomies, clamshell incision, or midline sternotomy.
• They may be performed with or without MCS.

Preoperative Assessment²

• Preoperative anesthetic assessment should include evaluation of medical comorbidities, ability to tolerate surgery/anesthesia, and modifiable risk factors.
  • The degree of disability and frailty are independent risk factors for poor outcomes.
  • Cardiovascular assessment should include evaluation for heart failure and atherosclerotic disease.
  • Baseline renal function and risk for perioperative renal dysfunction should be assessed.
  • Poorly controlled diabetes mellitus is associated with poor outcomes.
  • In rapidly worsening pulmonary disease refractory to medical therapy, extracorporeal membrane oxygenation (ECMO) may be considered as a bridge to transplantation.⁴

Intraoperative Management

Monitors and Vascular Access²

• Standard American Society of Anesthesiologists monitors, including electrocardiography, noninvasive blood pressure, pulse oximetry, end-tidal carbon dioxide, end-tidal volatile concentration, and temperature
  • If using peripheral venoarterial-ECMO (VA-ECMO), the pulse oximeter should be placed on the right upper extremity, right ear, or nose to monitor for differential hypoxemia.
  • The relationship between measured end-tidal volatile anesthetic concentration and concentration in the brain may be abnormal in end-stage lung disease.
    • Depth of anesthesia monitoring is recommended (e.g., bispectral index monitor).
• Cerebral oximetry
• Arterial line for blood pressure monitoring and frequent arterial blood gases
  • If using peripheral VA-ECMO, the arterial line should be placed in the right upper limb.
• Central venous introducer/catheter
  • Consider avoiding the right internal jugular vein to preserve this vein for peripheral venovenous-ECMO cannulation if needed
• Pulmonary artery catheter: if no contraindications to placement
  • Intra and postoperative monitoring of pulmonary artery pressures, volume status/filling pressures, cardiac output, mixed venous oxygen concentration
• Transesophageal echocardiography
  • Comprehensive exam, including assessment for the presence of a patent foramen ovale, right ventricular (RV) function, and degree of tricuspid regurgitation, and pulmonary vein velocities
• Adequate vascular access should be ensured, including the use of large-bore peripheral intravenous catheters.

Perioperative Sedation²

• Patients presenting for lung transplantation often have minimal cardiopulmonary reserve
  • They have a high risk for complications from respiratory depression
  • Sedation/anxiolysis should be avoided prior to the operating room.
    • Especially if on supplemental O₂ or pulmonary hypertension
  • Extreme caution should be used if providing sedation/anxiolysis in the operating room.
    • Monitor closely for hypoventilation, hypercarbia, and hypoxia

Induction and Maintenance²

• These patients are at an increased risk for cardiovascular collapse with induction, including RV failure
  • Starting inotropic infusion at induction in patients with pulmonary hypertension and/or RV dysfunction should be considered.
• The surgeon and perfusionist should be immediately available for the emergent initiation of MCS should the patient acutely decompensate with induction of anesthesia.
• Preinduction femoral arterial and venous lines in high-risk patients should be ensured to allow for rapid cannulation for MCS.
• Starting an inhaled pulmonary vasodilator should be considered prior to induction.
• Apneic time should be minimized to avoid hypoxia and hypercarbia.
• Maintenance anesthetic should be tailored to the patient’s pathophysiology, surgical approach, and use of MCS.
  • If gas exchange or blood flow to the lungs is compromised (e.g., unable to achieve adequate minute ventilation; use of MCS), total intravenous anesthesia is preferred.

Airway and Ventilatory Management^2,5,6

• An intubation strategy should be selected that will optimize the chance of first-pass success.
• The choice of endotracheal tube (ETT) is determined by the surgical approach and use of MCS.
  • If surgery is performed without MCS, lung isolation is required.
  • If surgery is performed with MCS, lung isolation may not be necessary.
• Lung isolation can be performed with a double-lumen ETT or a single-lumen tube with a bronchial blocker.
• Ventilator management
  • High tidal volumes and inspiratory pressures should be avoided at all stages of the surgery
  • Tidal volumes lower than or equal to 8cc/kg and inspiratory pressures lower than or equal to 25cmH₂O should be recommended.
• Ventilation should be further tailored to the primary lung pathology.
  • COPD: avoid dynamic hyperinflation
  • Restrictive lung disease: often need higher airway pressures, positive end-expiratory pressure (PEEP), and I:E ratios
  • Cystic fibrosis: may require hyperventilation to maintain gas exchange; frequent suctioning of secretions
• Intraoperative ventilator management can modify the risk of developing PGD
  • Goal fraction of inspired oxygen (FiO₂) less than 0.4 during reperfusion
  • Use the lowest FiO₂ necessary to maintain PaO₂ greater than 70mmHg
  • After graft implantation, recommend tidal volumes less than 6cc/kg of the donor’s predicted body weight
  • Recommend peak inspiratory pressures (PIP) less than 25cmH₂O and PEEP 6-8cmH₂O

Perioperative MCS^2,4,7

• Not all lung transplants require MCS; it is used in 30- 50% of lung transplantations.
• If intraoperative MCS is necessary, VA-ECMO or cardiopulmonary bypass (CPB) is most commonly used
• Potential indications for MCS:
  • PaO₂ less than 80mmHg on FiO₂ of 1.0
  • PIP more than 35cmH₂O
  • Suprasystemic pulmonary artery pressures
  • Inability to use lung-protective ventilation
  • Inability to perform lung isolation if needed
  • Need for intracardiac repair or complete ventricular decompression
• ECMO
  • Configuration depends on patient needs, although VA-ECMO most common
  • Patients on VV-ECMO prior to transplant may have their configuration changed to VA-ECMO intraoperatively
  • May be associated with better outcomes compared to off-pump lung transplantation
• CPB
  • Allows for open-heart procedures
  • Use of CPB is an independent risk factor for the development of PGD.
• ECMO and CPB are compared and contrasted in Table 2.

Transfusion and Fluid Management²

• Euvolemia should be maintained but avoid excessive fluid administration should be avoided.
  • Excessive fluid administration is associated with the development of PGD.
    • Increased hydrostatic forces in the pulmonary microcirculation can worsen lung injury, particularly in the setting of a disrupted lymphatic system.
  • Volume overload can also worsen RV dysfunction.
• Red blood cell transfusions should be minimized.
  • Red blood cell and fresh frozen plasma transfusions are associated with an increased risk of PGD.

Pulmonary Vasodilators^2,5

• Pulmonary vasodilators may be used to reduce shunting and pulmonary artery pressures.
  • Patients with pulmonary arterial hypertension may present with a continuous pulmonary vasodilator infusion.
    • Abrupt discontinuation of the infusion can lead to rebound pulmonary hypertension.
• Inhaled pulmonary vasodilators include nitric oxide and epoprostenol.
  • The inhaled route is preferred intraoperatively to avoid systemic vasodilation.
  • It should be selectively delivered to ventilated portions of the lung, improving V/Q matching.
  • RV afterload should be reduced by reducing pulmonary vascular resistance; help support RV function.

Postoperative Care

Pain Management^1,6

• Parenteral and enteral analgesics
  • Opiates/opioids carry the risk of respiratory depression.
  • Acetaminophen
  • Nonsteroidal anti-inflammatory drug should be avoided due to the risk of postoperative renal dysfunction.
• Regional anesthesia
  • Thoracic epidural is considered the historical gold standard for postoperative pain control; however, nonneuraxial regional techniques are increasingly being used.
  • A thoracic epidural typically placed at the T4-T5 or T5-T6 levels.
    • Considerations include coagulation status, potential for hypotension
  • Paravertebral catheters
    • Mostly examined in the setting of thoracic surgery; potentially noninferior to thoracic epidural.
  • Serratus anterior plane block (SAPB) or erector spinae plane block
    • Limited data available; SAPB may be noninferior to thoracic epidural for postthoracotomy pain
• Cryoablation: shown to have a similar analgesic outcome as a thoracic epidural.

Ventilator Management^1,4

• Protective ventilation for the allograft
  • Low tidal volumes, ideally less than 6 ml/kg, avoidance of high inspiratory pressures, permissive hypercarbia, utilization of PEEP to support oxygenation, and minimization of FiO₂
• Early extubation should be pursued if no graft dysfunction and hemodynamic stability.
• Avoid PEEP or use minimal PEEP in single lung transplant patients to avoid overdistention of the native lung

PGD^2,6,8

• PGD is the leading cause of death after lung transplantation
• It typically occurs within 72 hours of transplant
• It is defined as a PaO₂/FiO₂ ratio less than 300 and/or pulmonary edema on chest X-ray.
• Risk factors modifiable by the anesthesiologist:
  • Avoid excessive intraoperative blood product or fluid administration
  • Avoid hyperoxia during allograft reperfusion
  • Avoid hyperinflation, large tidal volumes, and elevated PIPs
• Treatment remains supportive with lung-protective ventilation and early postoperative MCS in the case of severe PGD.

Infections⁸

• The incidence of bacterial pneumonia is 10-20% within the first 30 days, despite antibiotic prophylaxis.
• Bacterial pneumonia is the primary cause of mortality in the first 30 days.