How would you evaluate and prepare a patient with chronic bronchiectasis scheduled for pneumonectomy? Briefly enumerate the postoperative complications.
Prethoracotomy assessment involves all of the factors of a complete anesthetic assessment: past history, allergies, medications, upper airway.
The concurrent illness in the thoracic surgical patient is bronchi ecstasies which causes the dominant clinical feature of impairment of expiratory airflow.Assessment of the severity of Bronchiectasis is on the basis of the FEV1% of predicted values. The American Thoracic Society currently categorizes stage I as greater than 50% predicted ,stage II as 35% 50%, and stage III as less than 35%. Stage I patients should not have significant dyspnea, hypoxemia, or hypercarbia, and other causes should be considered if these are present.
Respiratory Drive
Many stage II or III patients have an elevated Paco2 at rest and this CO2 retention is due to to an inability to maintain the increased work of respiration (WResp) required to keep the Paco2 normal in patients with mechanically inefficient pulmonary function .
Right Ventricular Dysfunction
Right ventricular (RV) dysfunction occurs in a majority of patients,the dysfunctional right ventricle is poorly tolerant of sudden increases in afterload, such as the change from spontaneous to controlled ventilation.RV function becomes critical in maintaining cardiac output as the pulmonary artery pressure rises. The RV ejection fraction does not increase with exercise in COPD patients as it does in normal patients. Chronic recurrent hypoxemia is the cause of the RV dysfunction and the subsequent progression to cor pulmonale.
Cor pulmonale is to be ruled out in patients with an FEV1 less than 1 L more so in patients with a FEV1 less than 0.6 L. The only therapy that has been shown to improve long-term survival and decrease right-sided heart strain in is oxygen. Patient who have resting Pao2 less than 55 mm Hg should receive supplemental home oxygen; this includes those who desaturate to less than 44 mm Hg with usual exercise. The goal of supplemental oxygen is to maintain a Pao2 of 60 to 65 mm Hg.
Preoperative Therapy for Bronchiectasis
There are four treatable complications of bronciectasis that are to be treated prior to surgery. These are atelectasis, bronchospasm, respiratory tract infections, and pulmonary edema .
A comprehensive program of pulmonary rehabilitation involving physiotherapy, exercise, nutrition, and education can improve functional capacity for patients with severe Bronchiectasis.
Among the different modalities available (e.g., cough and deep breathing, incentive spirometry, PEEP, continuous positive airway pressure [CPAP]), there is no clearly proven superior method.
All COPD patients should receive maximal bronchodilator therapy as guided by their symptoms. Only 20% to 25% of COPD patients will respond to corticosteroids. In a patient who is poorly controlled on sympathomimetic and anticholinergic bronchodilators, a trial of corticosteroids may be beneficial.
Smoking
Pulmonary complications are decreased in thoracic surgical patients who cease smoking for more than 4 weeks before surgery. Carboxyhemoglobin concentrations decrease if smoking is stopped more than 12 hours.It is extremely important for patients to avoid smoking postoperatively. Smoking leads to a prolonged period of tissue hypoxemia. Wound tissue oxygen tension correlates with wound healing and resistance to infection.
Assessment of Respiratory Function
The best assessment of respiratory function comes from a detailed history of the patient's quality of life. All pulmonary resection patients should have baseline simple spirometry preoperatively.Objective measures of pulmonary function are required to guide anesthetic management .
Respiratory Mechanics
Many tests of respiratory mechanics and volumes show correlation with post-thoracotomy outcome: forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), maximal voluntary ventilation (MVV), residual volume/total lung capacity ratio (RV/TLC), and . It is useful to express these as a percent of predicted volumes corrected for age, sex, and height (e.g., FEV1%). Of these the most valid single test for post-thoracotomy respiratory complications is the predicted postoperative FEV1 (ppoFEV1%),which is calculated as follow
ppo FEV1%= preoperative FEV1%mutiplied with [1-%functional tissue removed/100]
Patients with a ppoFEV1 greater than 40% are at low risk for postresection respiratory complications.
Lung Parenchymal Function
Lung parenchymal function indicates the ability of the lung to exchange oxygen and carbon dioxide between the pulmonary vascular bed and the alveoli. Traditionally, arterial blood gas data such as Pao2 less than 60 mm Hg or Paco2 greater than 45 mm Hg have been used as cutoff values for pulmonary resection.
The most useful test of the gas exchange capacity of the lung is the diffusing capacity for carbon monoxide (DLco). The DLco correlates with the total functioning surface area of the alveolar-capillary interface. This simple noninvasive test, which is included with spirometry and plethysmography by most pulmonary function laboratories, is a useful predictor of perioperative mortality but not long-term survival.The corrected DLco can be used to calculate a postresection (ppo) value using the same calculation as for the FEV1 . A ppoDLco less than 40% predicted correlates with both increased respiratory and cardiac complications.
Cardiopulmonary Interaction
The final and perhaps most important assessment of respiratory function is an assessment of the cardiopulmonary interaction. Formal laboratory exercise testing is currently the “gold standard” for assessment of cardiopulmonary function,and the maximal oxygen consumption (Vo2max) is the most useful predictor of post-thoracotomy outcome. The risk of morbidity and mortality is unacceptably high if the preoperative Vo2max is less than 15 mL/kg/min.Few patients with a Vo2max greater than 20 mL/kg/min have respiratory complications (for comparison, the highest Vo2max recorded is 85 mL/kg/min.
Stair climbing is done at the patient's own pace but without stopping and is usually documented as a certain number of flights. There is no exact definition for a “flight,” but 20 steps at 6 in/step is a frequent value. The ability to climb five flights correlates with a Vo2max greater than 20 mL/kg/min, and climbing two flights corresponds to a Vo2max of 12 mL/kg/min. A patient unable to climb two flights is at extremely high risk.
A 6MWT distance of less than 2000 ft (610 m) correlates to a Vo2max less than 15 mL/kg/min and also correlates with a fall in oximetry (Spo2) during exercise. Patients with a decrease of Spo2 greater than 4% during exercise predicts an increased morbidity and mortality.
Ventilation-Perfusion Scintigraphy
Prediction of postresection pulmonary function can be further refined by assessment of the preoperative contribution of the lung or lobe to be resected using ventilation-perfusion lung scanning. If the lung region to be resected is nonfunctioning or minimally functioning, the prediction of postoperative function can be modified accordingly. This is particularly useful in pneumonectomy patients,and scanning should be considered for any pneumonectomy patient who has a preoperative FEV1 and/or DLco less lthan 80%
lung mechanics, parenchymal function, and cardiopulmonary interaction—should be made for each patient. These three aspects of pulmonary function form the “three-legged stool” that is the foundation of prethoracotomy respiratory assessment
Post operative complications
Cardiac complications represent the second most common cause of perioperative morbidity and mortality in the thoracic surgical population.
Arrhythmia
Dysrhythmias are a common complication of pulmonary resection surgery, and the incidence is 30% to 50% of patients in the first week postoperatively when Holter monitoring is used. of these arrhythmias, 60% to 70% are atrial fibrillation. Several factors correlate with an increased incidence of arrhythmias: extent of lung resection (pneumonectomy, 60%, versus lobectomy, 40%, versus nonresection thoracotomy, 30%) intrapericardial dissection, intraoperative blood loss, and age of the patient
Ischemia
Because the majority of pulmonary resection patients have a smoking history, they already have one risk factor for coronary artery disease. Elective pulmonary resection surgery is regarded as an “intermediate risk” procedure in terms of perioperative cardiac ischemia.The overall documented incidence of post-thoracotomy ischemia is 5% and peaks on days 2 to 3 postoperatively.
Renal Dysfunction
Renal dysfunction after pulmonary resection surgery is seen in patients who developed a significant elevation of serum creatinine concentration in the post-thoracotomy period, compared with 0% (0/99) in those who did not show any renal dysfunction. The factors, which were associated with an increased risk of renal impairment, were history of previous renal impairment, diuretic therapy, pneumonectomy, postoperative infection, and blood transfusion. Nonsteroidal anti-inflammatory drugs (NSAIDs) were not associated with renal impairment
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