Anesthesia

Invasive surgery that involves the chest cavity is generally performed with general anesthesia, although diagnostic procedures such as bronchoscopy, needle biopsy, and thoracentesis are commonly performed with local (topical) anesthesia, often with small titrated amounts of intravenous sedation.¹ Epidural catheters can also be placed before surgery for use during surgery and for extended postoperative pain control after pneumonectomy or lobectomy. Because these procedures all involve the airway in addition to anesthesia, patients are given nothing by mouth before any procedure.

Topical anesthesia involves the instillation or spray of a local anesthetic, commonly 4% lidocaine hydrochloride (Xylocaine), onto the laryngeal and pharyngeal surfaces. Although uncommon, toxic reactions or bronchospasm can occur; therefore emergency equipment should be readily available. Recovery of the patient after topical anesthesia requires airway assessment, ready availability of emergency resuscitation equipment, and the administration of humidified oxygen after the procedure. The patient must be given nothing by mouth until the pharyngeal and laryngeal reflexes have returned (2 to 4 hours). Patients should be advised to rest their voices after the procedure; in fact, the surgeon may prescribe a time interval for voice rest. When the gag reflex has returned, throat lozenges and warm drinks may help to relieve the sore throat that inevitably follows bronchoscopy.

Epidural anesthesia involves placement of a catheter into the epidural space of the thoracic vertebrae with subsequent instillation of an infusion combination of an opioid and local anesthetic to achieve sensory blockade of pain without compromising motor function needed for coughing, deep breathing, and ambulating. Thoracic epidural anesthesia can be used in combination with either sedation or general anesthesia.¹ The catheter can be left in place for up to 3 days after surgery for pain control and may be regulated solely by medical personnel or controlled by the patient. Epidural anesthesia is commonly used as an adjunct to general anesthesia.

Paravertebral or intercostal blockade is a regional technique used for the thoracic surgery patient. The advantage of these blocks is neural blockade; the disadvantage is that they last only until the local anesthetic is metabolized.¹ The most commonly used anesthetics for these blocks are lidocaine, bupivacaine, and ropivacaine. Intrapleural local anesthetic instillation can be used for postoperative analgesia, but has the potential for systemic absorption and toxicity.¹ See Chapters 24 and 25 for information on local anesthetics and regional anesthesia.

General anesthesia involves the administration of some combination of inhalation anesthetics, intravenous anesthetics, benzodiazepines, opioids, muscle relaxants, and reversal agents and aims to render the patient amnestic and pain free. Somatic, autonomic, and endocrine reflexes are eliminated, and skeletal muscle relaxation is achieved. Because of the effects of general anesthesia on respiratory function and effort, in conjunction with a preexisting compromise in the respiratory system that necessitates surgery, nursing care must emphasize respiratory assessment, monitoring, and application of prompt intervention if evidence of compromise is noted after surgery.

The patient and family should receive detailed information preoperatively. When possible, taking time to improve the patient’s pulmonary, physical, and nutritional status is desirable.² Smoking cessation is an important preoperative aspect of surgery; however, the effects of smoking linger after cessation with benefits noted after a year. Smokers who have recently quit have no difference in pulmonary complications than current smokers.³ Preoperative medications should be continued with the exception of anticoagulant medications.² The perianesthesia nurse should review the diagnostic and laboratory tests preoperatively. Preoperative evaluation of the patient who will undergo thoracic surgery may include laboratory tests and pulmonary function tests listed in Table 34-1.

Table 34-1 Laboratory Studies for Assessment of Patients Undergoing Thoracic Procedures

LABORATORY STUDY	NORMAL RESULTS	SIGNIFICANCE OF ABNORMAL FINDINGS
Perfusion Studies—Arterial Blood Gases
pH	7.35-7.45	Changes indicate metabolic or respiratory acidosis.
PaCO2	35-45 mm Hg	Elevations indicate possible COPD, asthma, pneumonia, anesthetic effects, or use of opioids (respiratory acidosis). Decreased levels indicate hyperventilation/respiratory alkalosis.
HCO3−	21-28 mEq/L	Elevations indicate possible respiratory acidosis as compensation for primary metabolic alkalosis. Decreased levels indicate possible respiratory alkalosis as compensation for primary metabolic acidosis.
PaO2	80-100 mm Hg	Elevations may indicate possible excessive oxygen administration. Decreased levels indicate possible COPD, asthma, chronic bronchitis, cancer of bronchi and lungs, respiratory distress syndrome, or any other cause of hypoxia.
O2 saturation	95%-100%	Decreased levels indicate possible impaired ability of hemoglobin to release oxygen to tissues.
Complete Blood Count
RBCs	Male: 4.7-6.1 million/mm3 Female: 4.2-5.4 million/mm3

Elevated levels may be due to excessive production of erythropoietin, which occurs in response to a hypoxic stimulus, such as COPD. Decreased levels may indicate anemia, hemorrhage, or hemolysis. Hemoglobin Same as for RBCs. Hematocrit Same as for RBCs. WBCs 5000-10,000/mm³ Elevations indicate possible acute bacterial infections or inflammatory conditions (smoking). Decreased levels may indicate overwhelming infection or immunosuppression. TEST PURPOSE FVC (forced vital capacity): Records maximum amount of air that can be exhaled as quickly as possible after maximum inspiration. Provides an indication of respiratory muscle strength and ventilatory reserve. Often reduced in obstructive disease (because of air trapping) and in restrictive disease. FEV₁ (forced expiratory volume in 1 sec): Records maximum amount of air that can be exhaled in first second of respiration. Effort dependent and declines with age. Reduced in certain obstructive and restrictive disorders. FEV₁/FVC: Ratio of expiratory volume in 1 sec to FVC Provides a more sensitive indicator of obstruction to airflow. Ratio is normal or increased in restrictive disease. FEF_25%-75%: Records forced expiratory flow over 25%-75% volume (middle half) of FVC. This measure provides a more sensitive index of obstruction in smaller airways. FRC (functional residual capacity): Amount of air remaining in lungs after normal expiration. Increased FRC indicates hyperinflation or air trapping, which can result from obstructive disease. TLC (total lung capacity): Amount of air remaining in lungs at end of maximum inhalation Increased TLC indicates air trapping associated with obstructive pulmonary disease. Decreased TLC indicates restrictive disease. RV (residual volume): Amount of air remaining in lungs at end of a full, forced exhalation RV is increased in obstructive pulmonary disease, such as emphysema. DL_co (diffusion capacity of carbon monoxide): Reflects surface area of alveolocapillary membrane DL_co