Sequelae & Complications of PneumonectomyPresentation Transcript
Sequelae and Complications of Pneumonectomy By Nabil Ali Assisstant Lecturer Chest Department, Banha University.
Pneumonectomy, or surgical removal of an entire lung, is performed most frequently for management of bronchogenic carcinoma.
Pneumonectomy may rarely be required for pulmonary metastases or for a variety of forms of benign disease, such as inflammatory lung disease (eg, pulmonary tuberculosis, fungal infections, and bronchiectasis), traumatic lung injury, congenital lung disease, and bronchial obstruction with a destroyed lung.
Because of the significant loss of lung function following pneumonectomy as well as the fact that many patients undergoing lung resection have abnormal lungs prior to surgery, it is critical to assess a patient's functional reserve and the predicted pulmonary function following pneumonectomy.
Patients with a preoperative FEV1 of greater than 2 L appear to be at low risk and require no further testing, provided there is no clinical or radiographic evidence of pulmonary hypertension.
Patients with a preoperative FEV1 of less than 2 L should have their predicted postoperative FEV1 (ppoFEVI) estimated. This is performed by multiplying the patient's preoperative FEV1 by the percentage of perfusion to the remaining lung, as determined by a quantitative lung perfusion scan.
Patients with a ppoFEV1 greater than or equal to 800 mL, or greater than 40 percent of predicted, have an estimated mortality rate of approximately 15 percent.
Patients with ppoFEV1 values less than 800 mL have typically been excluded from participating in studies assessing the risk of death due to pneumonectomy. However, it is not necessarily to exclude any patient from undergoing pneumonectomy for potentially curable disease solely on the basis of preoperative pulmonary function testing for three reasons:
1• A prospective study has yet to be performed to determine the mortality rate in patients with ppoFEV1 values below 800 mL.
2• There have been retrospective reports of low mortality rates in the older literature in patients who almost certainly had ppoFEV1 below 800 mL following pneumonectomy.
3• It cannot be assumed that the ppoFEV1 is consistently accurate.
Some authors have suggested that Cardiopulmonary exercise testing be used to determine if a patient can survive lung resection, particularly in those patients with relatively low or borderline ppoFEV1. Cardiopulmonary exercise testing has the theoretical advantage of assessing the patient's cardiopulmonary function and reserve. However, the studies addressing exercise testing have not been definitive.
Most studies support the conclusion that patients with a preoperative maximum oxygen consumption (VO2max) less than 10 mL/kg/min are at high risk of death (>30 percent), while those with a preoperative VO2max greater than 15 mL/kg/min have an acceptable risk (<15 percent).
MORTALITY RATES AND RISK FACTORS
• A right-sided pneumonectomy is associated with a higher mortality rate, ranging from 10 to 12 percent compared with 1 to 3.5 percent for left-sided pneumonectomy. While the reasons are not certain, likely factors include several life-threatening complications that are encountered more frequently after right pneumonectomy (eg, postpneumonectomy space empyema, bronchopleural fistula, and postpneumonectomy pulmonary edema).
• The specific type of surgical resection is an independent risk factor for mortality. As an example, pleuropneumonectomy with chest wall resection are associated with a 3-fold increase in mortality compared to a simple pneumonectomy. In contrast, completion pneumonectomy (ie, a reoperation to remove the remaining portion of a previously, partially resected lung) has not been found to be a significant risk factor.
• Pneumonectomy performed emergently for trauma or massive hemoptysis is associated with a mortality rate exceeding 35 percent, likely reflecting the severity of the underlying process.
• Several comorbid medical illnesses have been identified as risk factors for increased mortality. These include underlying lung disease, coronary artery disease, congestive heart failure, atrial fibrillation, hypertension, hemiplegia, active cigarette smoking, and weight loss greater than 10 percent within the 6 months preceding surgery.
• While some studies have demonstrated that increased age (eg, >60 to 75 years) is a risk factor for increased mortality with pneumonectomy, others have not.
• The level of experience of the surgeon performing the operation may affect the mortality rate. A lower mortality rate for lung cancer resection has been demonstrated when the surgery is performed by a thoracic surgeon rather than a general surgeon.
Immediately following pneumonectomy, air fills the space previously occupied by the lung (ie, the postpneumonectomy space, or PPS).
Unlike the situation with most other forms of thoracic surgery, a chest tube is not inserted following pneumonectomy, and the air is therefore not evacuated.
Over time, a number of changes result in a decrease in the size of the PPS, including elevation of the hemidiaphragm, hyperinflation of the remaining lung, and shifting of the mediastinum towards the PPS.
At the same time, there is progressive resorption of air in the PPS and replacement with fluid.
Chest radiographic findings immediately after surgery demonstrate the trachea to be midline and the PPS to be filled with air.
Within 24 hours the ipsilateral hemidiaphragm becomes slightly elevated, the mediastinum shifts slightly towards the PPS, and fluid starts accumulating in the PPS. As a general rule, fluid accumulates at a rate of approximately two rib spaces per day. After two weeks, 80 to 90 percent of the PPS is filled with fluid.
Complete opacification of the hemithorax after pneumonectomy takes an average of approximately 4 months, with a range from 3 weeks to 7 months.
Only a minority of patients have complete obliteration of their PPS, with most patients having residual fluid and/or air.
Unexpectedly rapid accumulation of fluid into the PPS in the immediate postoperative period should raise concerns for hemorrhage into the PPS, infection of the PPS, or the development of a chylothorax.
The location of vital organs such as the heart and great vessels, liver, and spleen changes significantly following pneumonectomy as a consequence of mediastinal shift and elevation of the hemidiaphragm.
Extreme care must be taken prior to inserting a needle or chest tube into the PPS, due to the risk of injury to vital organs that have shifted position following the surgery. An imaging study such as ultrasound or CT scan to help locate vital organs prior to draining the PPS is recommended.
PULMONARY FUNCTION FOLLOWING PNEUMONECTOMY
• Postpneumonectomy lung volumes fall, but typically less than expected for removal of approximately 50 percent of the original lung tissue. This is especially true for residual volume and is a consequence of overexpansion of the remaining lung. However, despite this overexpansion, there is no pathological evidence of emphysema in the remaining lung.
• Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) usually decrease by less than 50 percent.
• Diffusing capacity for carbon monoxide (DLCO) also decreases by less than 50 percent, and is usually normal when corrected for lung volume.
• Lung compliance decreases, airway resistance increases, and dead space may either increase or decrease.
• Arterial oxygen saturation, PO2, and PCO2 at rest do not change in those patients with little or no disease in the remaining lung.
There is little subsequent decline in lung function that can be attributed to pneumonectomy beyond one year after the procedure.
Long-term studies have demonstrated minimal further change in FEV1 up to 20 years after pneumonectomy, with annual decrements in FEV1 that are 3 to 4 ml per year, which is less than that expected for the general population.
CARDIOVASCULAR FUNCTION FOLLOWING PNEUMONECTOMY
Right ventricular ejection fraction decreases by about 20%, right ventricular end-diastolic volume increases by 20%, and left ventricular function does not change after pneumonectomy.
As long as the remaining lung is relatively normal, there is no significant change in resting values of systolic pulmonary artery pressure, pulmonary vascular resistance, or central venous pressure after lung resection.
Postpneumonectomy pulmonary edema
Although the pathogenesis is unknown and probably multifactorial, it is thought to represent a form of the acute respiratory distress syndrome (ARDS). It does not appear to be a complication of cardiac dysfunction, sepsis, pneumonia, or aspiration.
Postpneumonectomy pulmonary edema is characterized clinically by respiratory distress and hypoxemia within 72 hours of surgery. Treatment is supportive, including avoidance of fluid overload. Mortality rates exceed 50 percent.
One review of postpneumonectomy pulmonary edema suggests that the underlying mechanism of injury may be due to high inspired oxygen concentrations, associated with single-lung ventilation or ischemic and reperfusion injury to the remaining lung.
Postpneumonectomy syndrome reflects extrinsic compression of the distal trachea and mainstem bronchus due to shifting of the mediastinum and hyperinflation of the remaining lung.
It occurs more than 6 months following surgery and has even been reported 35 years after surgery. It is more common in patients who undergo surgery in childhood and is almost exclusively seen after right pneumonectomy.
The syndrome is characterized by development of progressive dyspnea, cough, inspiratory stridor, and recurrent pneumonia in patients at least 6 months after surgery. It can be fatal if left untreated.
Treatment consists of surgical repositioning of the mediastinum and filling of the PPS with a non-absorbable material.
In patients undergoing pneumonectomy for suppurative lung disease, purulent material can spill into the unoperated lung at the time of surgery. Respiratory failure and death have been reported from this complication.
Prevention of intraoperative spillage is therefore critically important, and includes such measures as endobronchial separation with a double-lumen endotracheal tube, prone positioning, and perioperative bronchoscopy to remove secretions.
PLEURAL SPACE COMPLICATIONS
Empyema in the postpneumonectomy space occurs with a frequency of approximately 5 percent.
Early empyema occurs within 10 to 14 days of surgery and is commonly associated with a bronchopleural fistula.
Late empyema, in which infection is most often acquired via a hematogenous route, occurs more than 3 months after pneumonectomy and has been reported even up to 40 years following surgery.
Chest radiographs may be helpful in suggesting the diagnosis. Specific radiographic findings include a shift of the mediastinum away from the PPS, failure of the mediastinum to shift normally in the immediate postoperative period, development of a new air-liquid level, or a sudden change in a preexisting air-liquid level.
The diagnosis is confirmed by image guided sampling and analyzing the fluid in the PPS.
Bronchopleural fistula occurs with a frequency ranging from 1.5 to 4.5 percent, and is associated with a mortality ranging from 29 to 79 percent. Bronchopleural fistulas occurring within one week of surgery are not necessarily associated with an empyema, whereas those occurring more than two weeks after surgery are associated with an empyema.
Risk factors for formation of a bronchopleural fistula include right-sided procedures, residual tumor, concurrent radiation therapy or chemotherapy, age greater than 60 years, and poor wound healing.
Esophagopleural fistula formation occurs with a frequency of 0.5 percent and is more common after right-sided procedures.
Most develop at least a year after pneumonectomy and are due to recurrent tumor eroding into the esophagus. Because esophagopleural fistulas are always associated with an empyema, symptoms are identical to those accompanying a late postpneumonectomy empyema.
Diagnosis can be confirmed by performing a barium swallow.
Chylothorax, which occurs with a frequency less than one percent, develops within 15 days of surgery, usually in those patients who undergo concurrent lymph node resection. The diagnosis should be considered when there is rapid filling of the PPS in the immediate postoperative period.
Asymptomatic patients with slow accumulation of chyle can be treated conservatively with bowel rest, and the chylothorax eventually resolves spontaneously.
Patients with signs and symptoms of elevated central venous pressure, tachycardia, dyspnea, and hypotension as well as radiographic evidence of rapid filling of the PPS require drainage and surgical repair.
Rapid filling of the PPS with blood can occur within 24 hours of surgery. This complication is more common after pleuropneumonectomy or pneumonectomy for suppurative lung disease.
The clinical presentation may be with hypotension and shock due to the loss of intravascular blood volume. The mainstay of treatment is surgical re-exploration and control of bleeding sources.
Contralateral pneumothorax is a rare complication that is usually seen in the immediate postoperative period.
Proposed mechanisms have included intraoperative damage to the contralateral mediastinal pleura, or rupture of preexisting blebs or bullae.
Signs and symptoms include sudden onset of dyspnea and hypoxemia, and the diagnosis is confirmed by chest radiography.
Management includes evacuation of the air in the pleural space in order to achieve re-expansion of the underlying lung. Mortality is approximately 50 percent.
Cardiac arrhythmias occur in approximately 20 percent of cases, with most cases (80 percent) presenting within 72 hours of surgery. Over 65 percent of these arrhythmias are atrial fibrillation. Risk factors for development of an arrhythmia include age greater than 65 years, right pneumonectomy, pre-existing coronary artery disease, and hypertension.
Amiodarone has been shown to be safe and effective in convert patients with postoperative atrial fibrillation back into sinus rhythm after lung resection.
Myocardial infarction following pneumonectomy occurs with a frequency of 1.5 to 5 percent. Management follows the usual considerations for management of myocardial infarction in other settings. Mortality from this complication following pneumonectomy is in excess of 50 percent.
Pulmonary embolism following pneumonectomy can originate from several sources. In addition to the deep venous system of the lower extremities, thromboembolism can rarely originate from the pulmonary artery stump. Air embolism after pneumonectomy is rare and can usually be avoided by using a split-bronchus endotracheal tube and only ventilating the non-operated lung.
Herniation of the heart through the defect in the pericardium and into the empty pleural (postpneumonectomy) space can result in torsion and twisting of the heart.
Usually seen within 3 days of surgery, presenting as sudden onset of hypotension and shock, cyanosis, chest pain, and superior vena cava syndrome.
Treatment involves emergent surgery to reposition the heart and close the pericardial defect to prevent recurrence. Cardiac herniation may be prevented by primary closure of the pericardial defect at the time of pneumonectomy, or by suturing the edges of the pericardial defect to the myocardium.
Ninety percent of patients develop mild thoracic scoliosis after pneumonectomy due to shrinkage of the thoracic cage after surgery. Associated symptoms have not been reported in the postoperative period.
Postpneumonectomy paralysis is a rare complication due to intraoperative injury to the left lower intercostal arteries. These vessels feed the arteria magna, which in turn provides much of the blood supply to the thoracolumbar region of the spinal cord. This complication can also result from development of an epidural hematoma.
In some cases it may be complicated by development of cardiac tamponade. Diagnosis can be suggested by a pericardial "crunch" on physical examination or by a chest radiograph; treatment requires emergent surgery.
Gastric volvulus is a rare complication that has been seen more than one year following surgery. It probably occurs as a result of anatomic changes after surgery.