Handbook of Clinical Anesthesia
Anesthesia for Thoracic Surgery
The increased incidence of lung cancer has led to an increase in the amount of noncardiac thoracic surgery that is performed in the United States (Neustein SM, Eisenkraft JB, Cohen E: Anesthesia for thoracic surgery. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 1032–1072).
- Preoperative Evaluation
- The preoperative evaluation should focus on the extent and severity of pulmonary disease and cardiovascular involvement. Patients undergoing thoracic surgery who are known to be at high risk for postoperative complications include elderly individuals and people with poor general health or chronic obstructive pulmonary disease (COPD).
- History(Table 40-1)
- Physical Examination(Table 40-2)
- Laboratory Studies(Table 40-3)
- A vital capacity at least three times the tidal volume is necessary for an effective cough. A vital capacity below 50% of predicted or below 2 L is an indicator of increased risk.
- Thoracoscopic surgery and improved postoperative pain management have made it possible for patients with even smaller lung volumes to successfully undergo surgery.
- The ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) is useful in differentiating restrictive (normal ratio as both are decreased) from obstructive (low ratio as FEV1is decreased) disease.
Table 40-1 Patient Medical History That Should be Obtained Before Thoracic Surgery
Table 40-2 Physical Examination That Should be Done Before Thoracic Surgery
Table 40-3 Laboratory Studies That Should be Done Before Thoracic Surgery
Table 40-4 Factors That Predispose Patients to Complications After Thoracic Surgery
- A 15% improvement in pulmonary function tests after bronchodilator therapy is an indication for continued preoperative therapy.
- A mass that is seen on computed tomography is more likely to be malignant if it also demonstrates enhanced glucose uptake on the positron emission tomography scan.
- Preoperative Preparation
- Several conditions predispose patients to postoperative complications, and their preoperative treatment is associated with decreases in morbidity and mortality (Table 40-4).
- Patients scheduled for lung resection may benefit from tests to determine the extent of resection that will be tolerated as well as cardiopulmonary function testing in the presence of unilateral pulmonary artery occlusion (Fig. 40-1).
III. Intraoperative Monitoring
- Invasive monitoring and pulse oximetry have improved patient care (Table 40-5).
- An arterial catheter is essential to provide continuous recordings of blood pressure because surgical manipulations or intravascular volume shifts may cause sudden changes in blood pressure.
- Pulse oximetry is the standard of care for noninvasive assessment of blood oxygenation (especially during one-lung ventilation).
- Serial arterial blood gas determinations are necessary to confirm the adequacy of ventilation and
oxygenation as suggested by capnography and pulse oximetry.
Figure 40-1. The order of tests to determine the cardiopulmonary function status of the patient and the extent of resection that will be tolerated by the patient.
- During thoracotomy, a radial artery catheter is often placed in the dependent arm to aid in stabilizing the catheter. This catheter can also be used to monitor for possible axillary artery compression to avoid compression of the artery and brachial plexus with placement of a chest roll (misnomer, “axillary roll”) under dependent hemothorax.
- Physiology of One-Lung Ventilation
- Physiology of the Lateral Decubitus Position
- In an open-chested, anesthetized, and paralyzed patient, the dependent lung is overperfused (gravity-dependent blood flow) and underventilated.
Table 40-5 Invasive Monitoring for Thoracic Surgery
- Underventilation reflects minimal pressure of abdominal contents pressing against the upper diaphragm, making it easier for positive pressure ventilation to distend the nondependent lung.
- One-Lung Ventilation
- Indications for one-lung ventilation may be categorized as absolute and relative (Table 40-6).
- Double-Lumen Endobronchial Tubes
- These tubes are the most widely used means of achieving lung separation and one-lung ventilation.
The design of double-lumen tubes (there are many different types, but the design is similar for all) is characterized by two catheters bonded together with one lumen long enough to reach a mainstem bronchus while the other shorter catheter portion remains in the trachea above the carina.
Table 40-6 Indications for One-Lung Ventilation
- Lung separation is achieved by inflation of the tracheal and bronchial cuff. The bronchial cuff on a right-sided tube is slotted to allow ventilation of the right upper lobe because the right mainstem bronchus is too short to accommodate both the right lumen tip and cuff.
- Robershaw tubesare available as left- or right-sided clear plastic disposable tubes without a carinal hook. Lumina are of sufficient size to facilitate suctioning and offer low resistance to gas flow. The blue endobronchial cuff is easily recognized when fiberoptic bronchoscopy is used to confirm its position.
- A rubber silicone left double-lumen tube (Silbonco) is especially useful if the left mainstem bronchus is angled at 90 degrees from the trachea, making it almost impossible to position a conventional double-lumen tube.
- A left-sided double-lumen tube is preferred for both right- and left-sided procedures. (The left mainstem bronchus is longer than the right mainstem bronchus.)
- Typically, most women need a 37-Fr double-lumen tube, and most men are adequately managed with a 39-Fr double-lumen tube.
- The depth required for insertion of the double-lumen tube correlates with the patient's height (29 cm for people who are 170 to 180 cm tall, and for every 10-cm increase or decrease in height, the double-lumen tube is advanced or withdrawn 1 cm).
- Placement of Double-Lumen (Robershaw) Tubes
- Initial insertion of the tube is performed with the distal concave curvature facing anteriorly. After the tip of the tube is past the vocal cords, the stylet is removed, and the tube is rotated 90 degrees to direct the bronchial lumen appropriately toward the desired mainstem bronchus. Advancement of the tube is ended when moderate resistance to further passage is encountered (~29 cm in most adults), indicating that the tube tip has been firmly seated in the mainstem bronchus (Fig. 40-2).
Figure 40-2. Schematic depiction of the proper placement of a right or left endobronchial tube.
- After the tube is judged to be in the proper position, a sequence of steps is performed to check the tube's location (Table 40-7).
- Confirmation of placement using a fiberoptic bronchoscope is recommended (Table 40-8 and Figs. 40-3 and 40-4).
- Lung separation in a patient with a tracheostomymay be achieved with a separately inserted bronchial blocker. (Standard double-lumen tubes are usually too stiff to negotiate the curve required for insertion through a tracheal stoma.)
Table 40-7 Steps to Verify Proper Position of a Double-Lumen Tube
Table 40-8 Use of a Fiberoptic Bronchoscope to Verify Proper Placement of a Double-Lumen Tube
- Lung separation in a patient with a difficult airwaymay include use of a flexible fiberoptic endoscope, a double-lumen or Univent tube using a tube exchanger plus laryngoscopy, or a tube exchanger and bronchial blocker.
- Management of One-Lung Ventilation
- A goal of one-lung ventilation is to optimize arterial oxygenation (Table 40-9).
Figure 40-3. Use of a fiberscope to verify position of a double-lumen tube.
Figure 40-4. Examples of double-lumen tube malpositions.
- Clinical Approach to the Management of One-Lung Ventilation
- The position of the double-lumen tube should be rechecked after the patient has been placed in the lateral decubitus position. Two-lung ventilation is maintained as long as possible.
- During One-Lung Ventilation.After initiation of one-lung ventilation, PaO2 can continue to decrease for up to 45 minutes. (Pulse oximetry is a vital monitor.)
Table 40-9 Methods for Optimizing Oxygenation During One-Lung Ventilation
- If arterial hypoxemia occurs during one-lung ventilation, it is important to verify proper positioning of the tube using a fiberscope.
- If arterial hypoxemia persists after verification of tube position, addition of continuous positive airway pressure or positive end-expiratory pressure should be considered.
- Airway pressure should be monitored because a sudden increase may reflect tube dislocation.
- The practitioner should never hesitate to reinstitute two-lung ventilation until a patient can be stabilized or the cause of a patient's instability (arterial hypoxemia, hypotension, cardiac dysrhythmias) has been corrected.
VII. Choice of Anesthesia for Thoracic Surgery
- The likely presence of increased airway reactivity (cigarette smoking, chronic bronchitis, obstructive pulmonary disease) and the effect of volatile anesthetics or ketamine on bronchomotor tone should be considered.
- Propofol infusion in combination with remifentanil is useful for producing anesthesia associated with one-lung anesthesia and no effect on hypoxic pulmonary vasoconstriction.
- Lidocaine (1–2 mg/kg intravenously [IV]) has been used before airway manipulations to decrease the likelihood of reflex bronchospasm.
- An adequate depth of anesthesia before airway manipulation is the most important goal in managing patients with increased airway reactivity.
VIII. Hypoxic Pulmonary Vasoconstriction
- Hypoxic pulmonary vasoconstriction is a homeostatic mechanism that normally diverts blood flow away from hypoxic (atelectatic) regions of the lungs (local increases in pulmonary vascular resistance) and thereby optimizes oxygenation.
- Inhibition of hypoxic pulmonary vasoconstriction during one-lung ventilation may accentuate arterial hypoxemia. Nevertheless, inhaled anesthetics do not seem to interfere with hypoxic pulmonary vasoconstriction.
- Anesthesia for Diagnostic Procedures
- Bronchoscopyis most often performed with a fiberoptic bronchoscope that easily passes through a tracheal tube of 8.0 to 8.5 mm internal diameter.
- Mediastinoscopy(Table 40-10)
- Insertion of an endoscope into the thoracic cavity and pleural space is used for the diagnosis of pleural disease, effusions, and infectious diseases (especially acquired immunodeficiency syndrome) and for staging procedures and lung biopsy.
- Anesthesia can be provided using local, regional, or general anesthesia depending on the expected duration of the procedure and the physical status of the patient.
- If general anesthesia is required, either a single- or a double-lumen tube may be used. Positive pressure ventilation interferes with visualization via the endoscope, so a double-lumen tube is preferred.
- The spontaneous partial pneumothorax that occurs when the endoscope is inserted results in improved surgical visualization. The spontaneous pneumothorax is usually well tolerated even in awake patients because the skin and chest wall form a seal around the thoracoscope and limit the degree of lung collapse.
- Video-assisted thoracoscopic surgery (VATS)entails making small incisions in the chest wall, which allows the introduction of a video camera and surgical instruments into the thoracic cavity.
Table 40-10 Anesthetic Considerations During Mediastinoscopy
- Anesthesia Considerations
- As with traditional thoracotomy, the patient needs to be positioned in the lateral decubitus position for VATS, and lung collapse is needed for adequate surgical exposure.
- The need for one-lung ventilation is greater with VATS than with open thoracotomy because it is not possible to retract the lung during VATS as it is during an open thoracotomy.
- The operated lung should be deflated as soon as possible after tracheal intubation because it may take as long as 30 minutes for complete lung collapse to occur.
- Carbon dioxide insufflation into the pleural cavity is used to facilitate visualization. Insufflation pressures should be kept low (<5 mm Hg) because high pressures can cause mediastinal shift and hemodynamic compromise.
- Continuous positive airway pressure as commonly used to treat arterial hypoxemia during one-lung ventilation for an open thoracotomy is unacceptable during VATS (it would interfere with surgical procedure). During VATS, positive end-expiratory pressure to the non-operated (dependent) lung should be used.
- Postoperative Concerns
- Pain after VATS is less than after an open thoracotomy.
- Respiratory function is better preserved after VATS.
- Anesthesia for Special Situations
- High-frequency jet ventilationtechniques are often appropriate.
- Bronchopleural fistula and empyemaare more likely to occur after a pneumonectomy than after other types of lung resection. Management of anesthesia in such patients includes several considerations (Table 40-11).
- An alternative to tracheal intubation in awake patients is placement of a double-lumen tube under general anesthesia with the patient breathing spontaneously.
- Rapid sequence induction of anesthesia plus a muscle relaxant followed by placement of a single-lumen tracheal tube may be acceptable if the air leak is small and an empyema is not present.
Table 40-11 Anesthetic Considerations in Management of a Patient with a Bronchopleural Fistula
- For a large bronchopleural fistula, high-frequency jet ventilation may be the nonsurgical treatment of choice.
- Lung Cysts and Bullae
- These disorders usually represent end-stage emphysematous destruction of the lungs associated with severe obstructive pulmonary disease and carbon dioxide retention.
- Positive pressure ventilation or nitrous oxide may cause bullae to expand or rupture (tension pneumothorax).
- Ideally, a double-lumen tube is inserted with the patient breathing spontaneously while awake or during general anesthesia.
- Gentle positive pressure ventilation with rapid, small tidal volumes and pressures not to exceed 10 cm H2O may be used during the induction and maintenance of anesthesia, especially if the bullae have been shown to have no or only poor bronchial communication.
- Anesthesia for resection of the tracheamay be necessary to relieve stenosis that may occur after prolonged tracheal intubation or tracheotomy (Table 40-12).
- Bronchopulmonary lavageis performed under general anesthesia using a double-lumen tube, most often for the treatment of cystic fibrosis.
- Myasthenia Gravis
- Myasthenia gravis is caused by a decrease in the number of postsynaptic acetylcholine receptors (circulating
antibodies to the receptors), resulting in a decrease in the margin of safety of neuromuscular transmission (exercise-induced weakness).
Table 40-12 Anesthetic Considerations for Tracheal Resection
- Medical Therapy
- Anticholinesterase drugs are administered in an attempt to prolong the duration of action of acetylcholine. Whereas anticholinesterase overdose causes a cholinergic crisis (treat with IV atropine), underdose causes a myasthenic crisis (improves with edrophonium, 2–10 mg IV).
- Plasmapheresis decreases antibody titers, resulting in transient improvement. (It also causes a decrease in plasma cholinesterase.)
- This surgery is considered the treatment of choice in most patients with myasthenia gravis.
- The gland is removed by a median sternotomy or transcervically using a technique similar to mediastinoscopy (there is a lower incidence of postoperative ventilatory failure).
- Management of General Anesthesia(Table 40-13).
- Nondepolarizing Muscle Relaxants
- It is prudent to assume that even treated patients are sensitive to the effects of muscle relaxants, so the initial dose should be decreased. One approach is to titrate to effect using a peripheral nerve stimulator beginning with doses of muscle relaxant that are 1/10 to 1/20 the usual dose.
- Sugammadex is designed to bind rocuronium and provide rapid, complete, and long-lasting
antagonism of rocuronium-induced neuromuscular blockade.
Table 40-13 Anesthetic Considerations in Management of Thymectomy for Treatment of Myasthenia Gravis
Table 40-14 Postoperative Considerations After Thoracic Surgery
- Depolarizing Relaxants.Patients treated with anticholinesterases may be sensitive to succinylcholine, reflecting slowed metabolism of the muscle relaxant.
- Nonrelaxant Techniques.Because of concerns over the use of muscle relaxants in patients with myasthenia gravis, there have been many reports of successful use of drug combinations (propofol with nitrous oxide and fentanyl; sevoflurane with nitrous oxide and fentanyl) that do not include paralysis.
- Postoperative Care.The opioid dose should be decreased by one third because anticholinesterases may increase the analgesic effect of these drugs.
XII. Postoperative Management and Complications
Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine
Title: Handbook of Clinical Anesthesia, 6th Edition
Copyright ©2009 Lippincott Williams & Wilkins
> Table of Contents > Section VII - Anesthesia for Surgical Subspecialties > Chapter 41 - Anesthesia for Cardiac Surgery