Postoperative care of the thoracic surgery patient requires an active rehabilitative approach. Both the type of surgical procedure and the underlying disease can present a significant challenge to postoperative management. An illustration of this approach is early ambulation after surgery. Early postoperative ambulation confers multiple systemic benefits in any surgical setting but is uniquely valuable to the recovering thoracic surgery patient (Table 8-1). Ambulation promotes airway clearance and decreases the risk of pneumonia. These benefits are amplified in patients who have surgically related or underlying lung dysfunction. Thus the nature and extent of surgical resection in thoracic patients require a well-trained staff and specialized equipment for monitoring patient status, which together can have a significant impact on morbidity and mortality.
Although many principles of postoperative care in the thoracic surgery population are common to other areas of surgery, there are some important differences. For example, fluid management in thoracic patients differs significantly from strategies used in nonthoracic patients. Lung edema and its effect on pulmonary compliance are closely linked to extracellular fluid volume. Many maneuvers made during thoracic surgery result in an increase in lung water. To compensate, it may be appropriate to restrict fluid administration postoperatively. In general, minimizing total body water improves pulmonary compliance and overall lung function.
Mediastinal dissection, whether for mediastinal tumor or esophageal surgery, can be associated with idiopathic pleural and pericardial effusions. Similarly, esophageal surgery, whether for motility disorder, reflux disease, or tumor, is associated with an increased risk for aspiration pneumonia. An additional consequence of esophagectomy is that it entails a complete vagotomy. In the acute setting, the complete vagotomy may result in prolonged dysmotility, enhancing the risk of malnutrition and even aspiration.
The range of issues that affect the recovery period include extubation, pain, air leak/chest tube management, fluid management, aspiration, ventilation, and the prevention of atrial fibrillation or pulmonary embolism. Specific complications related to a particular thoracic procedure may involve thoracic duct injury, vocal cord paralysis, pulmonary edema after lobectomy, esophageal anastomotic leak, and bronchopleural fistula.
Early extubation is the overriding goal of thoracic anesthesia and should be performed immediately after the surgical procedure. Immediate extubation not only improves patient mobilization but also promotes airway clearance. In rare circumstances, it may be beneficial to ventilate the postoperative patient overnight. Indications for postoperative ventilation include (1) bleeding that requires large-volume resuscitation, (2) inadequate pain control requiring high-dose parenteral narcotics, (3) decortication or visceral pleurectomy, and (4) a high-risk airway.
Postoperative pain control is essential for recovery, particularly in patients undergoing thoracotomy or sternotomy. For patients with severely impaired lung function, a preoperative epidural catheter is often indicated, even for thoracoscopic procedures. Chest wall pain can result in a restrictive chest wall and low lung volumes. Diminished forced vital capacity (FVC) and functional residual capacity (FRC) lead to fatigue and eventual hypoxemia. To prevent this consequence of chest wall pain in high-risk lung surgery patients, epidural catheters or, in selected patients, a paraspinal blockade should be used preemptively. Intravenous analgesics are not an acceptable substitute for epidural analgesia. Intravenous narcotics, whether patient-controlled or controlled by nursing, result in inevitable sedation and potential hypercarbia.
Chest drains are used to evacuate fluid that accumulates in the pleural space after surgery. Blood that collects in the pleural space needs to be evacuated because it may compromise lung function. Similarly, air in the pleural space indicates that the lung is inadequately filling the hemithorax, causing a proportionate impairment in lung function.
The amount of suction applied to the chest tube should be the minimum required to obtain full expansion of the lung. Too much suction may exclude the chest tube if locally compliant tissue occludes the holes of the tube. The chest tube also may be excluded if it is poorly positioned, such as in a fissure or in the lateral pleural space. Owing to the geometry of the thorax and lung, at least one chest tube should be placed in the apical thorax to facilitate optimal cephalad expansion of the lung and maintain control of the apical space. Often a basilar tube is also used to complement the apical tube and prevent the accumulation of subpulmonic air or fluid.
Pleural suction, usually applied using a pleural drainage unit, should also be minimized to limit airflow through the pleural space. Depending on the location of the pleural drain relative to the air leak, increasing the suction simply may increase the leak volume. A large ongoing air leak eventually will result in bacterial contamination as oral flora are entrained through the lung and deposited in the pleural space.
Proper chest tube management requires the recognition of several typical clinical situations:
Large swings in the water seal chamber. Tidal ventilation results in big swings in the chest tube water seal when there is a large residual pleural space. The chest contains relatively compliant structures. Therefore, the larger the space, the bigger is the swing. A large swing in the water seal chamber may reflect significant atelectasis or volume loss in the remaining lung.
Chest tube not draining a pneumothorax. The presence of a “paradoxical” pneumothorax implies one of two easily distinguishable clinical scenarios: (1) the unrecognized loss of pleural suction or (2) an air leak sufficiently large to overwhelm the suction provided by the pleural drainage unit. When there is a sudden loss of suction, it is commonly due to compression of the tube by either the patient or the wheel of the bed. An uncontrolled air leak of approximately 50 L/min usually indicates a systemic disconnection or, more ominously, a central airway communication.
Accumulation of pleural air with decreasing vacuum. When weaning the patient off chest tube suction, one should routinely check for the accumulation of pleural air. This “functional test” occasionally involves increasing the amount of applied vacuum. A rush of air through the drainage system at a higher suction setting implies that the previous setting was inadequate; that is, air was inappropriately accumulating at the lower setting. This test is far more sensitive than chest x-ray to determine the appropriateness of discontinuing suction (so-called water seal).
Small or intermittent air leak. The presence of a very small or intermittent air leak can be difficult to detect. One approach is to reconnect the suction device while the water seal chamber is observed carefully. A rush of air suggests that air was accumulating in the pleural space. A related approach is to clamp the chest tube for a period of time, place the tube back on suction, and then release the clamp while observing the water seal chamber.
A CT scan of the chest may be needed to determine the amount of air in the thoracic cavity and assess the relative advantage of placing additional chest drains (Fig. 8-1).
Intraoperative fluid management is critical to maintaining lung compliance. Injudicious fluid administration combined with surgical trauma may lead to a loss of pulmonary compliance and impaired postoperative ventilation. Patients with impaired lung function may require ventilatory support, but ventilation should be avoided whenever possible, because mechanical ventilation can cause a separate set of complications.
Postoperative lung edema and pulmonary compliance are closely related to extracellular fluid volume. This is particularly so in patients recovering from pulmonary resection, where lung tissues have been insulted from the surgical procedure itself. Fluid volumes must be monitored closely. Generally speaking, anything that can be done to minimize total body water in the recovery period will improve pulmonary compliance and overall lung function. Fluid management also plays a role in the surgical resection of mediastinal tumors because mediastinal dissection can be associated with idiopathic pleural or pericardial effusion.
The risk for aspiration pneumonia is particularly high in individuals undergoing esophageal surgery, whether for a motility disorder, reflux disease, or esophageal tumor. Complete vagotomy performed in conjunction with esophagectomy in the acute setting may result in prolonged dysmotility, which enhances the risk of malnutrition and aspiration.
Aspiration causes the tracheobronchial tree to be contaminated with material from the upper digestive tract. The two primary sources of aspirated substances are the oropharynx and the stomach. Oropharyngeal aspiration commonly results in bacterial contamination by anaerobic organisms, alone or in combination with aerobic and/or microaerophilic organisms. In most intensive care settings, the pathogens are hospital-acquired flora that disseminate via oropharyngeal colonization (e.g., enteric gram-negative bacteria and staphylococci).
The aspiration of gastric contents can result in chemical pneumonitis. The degree of pulmonary parenchymal injury depends on the chemical composition and volume of the aspirated material. Even small volumes of aspirated fluid with a pH less than 2.5 have been associated with severe chemical pneumonitis (Mendelson syndrome).1
Oropharyngeal and small-volume gastric aspiration is a common event in healthy individuals. The aspirated material is cleared by airflow (e.g., cough), mucociliary action, and pulmonary phagocytes. A major contributor to airway clearance is sustained airflow. Effective airflow depends on unobstructed airways and adequate lung volumes. Endotracheal tubes or mucus impaction are common reasons for inadequate airflow. Ventilator-associated pneumonias are a well-established and dangerous consequence of prolonged intubation.2 The risk of pneumonia is likely due to both the relative obstruction of mucociliary clearance and the presence of artificial surfaces in the airway. (Bacterial adherence, the so-called biofilm, is a characteristic of many species of bacteria, including Pseudomonas aeruginosa and Staphylococcus aureus.) Inadequate lung volumes result from recumbent posture and immobilization.
The treatment for oropharyngeal and small-volume gastric aspiration is mobilization and ambulation. Ambulation recruits lung volumes and improves airflow. Patients can be ambulated while requiring some ventilatory support, but extubation has the additional benefit of improving airway clearance and removing artificial surfaces within the trachea.
Because large-volume gastric aspiration typically is associated with acute respiratory failure, treatment requires long periods of intubation, ventilatory support, and emergent bronchoscopy. Broad-spectrum antibiotic coverage is usually begun at the time of aspiration, because the pulmonary injury is often associated with subsequent superinfection.
All patients benefit from reverse Trendelenburg positioning, which tilts the entire plane of the bed such that the head is elevated with respect to the legs (Fig. 8-2). Merely raising the head end of the bed by 30 degrees is inadequate because it is difficult to maintain the patient in this position and can even increase intraabdominal pressure. Patients who have had a left pneumonectomy are at particular risk for aspiration. The elevated left hemidiaphragm compromises hiatal antireflux mechanisms, and the single remaining lung makes any aspiration life threatening. Other patients at high risk for aspiration are esophagectomy patients. These patients may have prolonged gastrointestinal dysmotility because of acute thoracic vagotomy. To improve drainage of the gastric interposition graft, a pyloroplasty usually is performed,3 and some type of tube compression is often required for up to a week after surgery.
In rare circumstances, it may be beneficial or necessary to ventilate the postoperative patient overnight. Indications for postoperative ventilation include (1) a high-risk airway, (2) bleeding requiring large-volume replacement, (3) inadequate pain control requiring high-dose parenteral narcotics, and (4) decortication or visceral pleurectomy.
Postoperative ventilation can be beneficial to patients undergoing decortication or visceral pleurectomy. Both procedures result in a loss of lung compliance secondary to surgical trauma to the parenchyma. In addition, these procedures are often associated with a bloody pleural space and several days of air leak. Overnight ventilation helps to facilitate pleural apposition and minimize the accumulation of blood or air in the pleural space.
Cardiac myocytes undergo transient depolarization and repolarization that is triggered by external (e.g., nerve depolarization) or intracellular stimulation. The cardiac action potential is distinct from those found in nerve or muscle cells. The cardiac action potential is several hundred times longer (200–400 ms), and calcium plays a role in depolarization (Fig. 8-3).
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