Anesthesia in a Patient with Reactive Airways Case File

Anesthesia in a Patient with Reactive Airways Case File

Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 24

A 22-year-old college student presents for outpatient surgery. He is scheduled for an arthroscopic repair of the anterior cruciate ligament of his left knee, which he injured during a basketball game a month ago. He reports that his only chronic medical problem is asthma. He has been diagnosed with mild, intermittent asthma and he takes fluticasone/ salmeterol inhalational powder 250/50 daily. He reports not having an asthma attack in a year, but is feeling, “a little tight today because it’s cold outside.” As he is young, healthy, and to undergo a low-risk surgical procedure, no further preoperative testing is performed.

➤ What are the key pieces of information relevant in the preoperative evaluation of a patient with asthma?

➤ What are some considerations for an asthmatic having general anesthesia?

➤ What therapies can be used perioperatively to minimize the risk of an asthmatic attack?

ANSWERS TO CASE 24:

Anesthesia in a Patient with Reactive Airways

Summary: A 22-year-old patient with mild, intermittent asthma with new sportsinduced injury for outpatient knee surgery.

➤ Preoperative evaluation of asthma: It is important to know what triggers the attacks, their frequency and severity, and medications which the patient is taking and has taken on the day of surgery.

➤ Major considerations for an asthmatic patient having anesthesia: Include whether or not the patient’s condition is optimized prior to the procedure, the type of airway device required (if any), and the avoidance of drugs which release histamine.

➤ Perioperative medications: Beta-2 agonists administered via aerosolized treatment, or the patient simply using his or her own inhaler can be used to minimize the risk of an attack in the perioperative period.

ANALYSIS

Objectives

1. Understand the preoperative evaluation of patients with symptomatic reactive airway diseases.

2. Compare general anesthesia versus other modes of anesthesia, and delineate their benefits and drawbacks for the asthmatic patient.

3. Discuss various preoperative and intraoperative treatments for bronchospasm.

Considerations

This patient has mild, persistent asthma, and is experiencing mild symptoms preoperatively. During a more detailed history, he states that cold weather is a trigger for asthma, and that he takes an inhaler as a preventative medication daily, and uses an albuterol inhaler as a “rescue” medication for bronchospasm less than twice a month. This suggests that his asthma is relatively mild and well controlled. He also reports a more severe episode last winter, requiring outpatient treatment with a course of steroids. On the morning of the operation, he did take his daily inhaler, but has not taken any inhalational albuterol. It would be prudent to have the patient use an albuterol inhaler to decrease the likelihood of bronchoconstriction intraoperatively.

The anesthesia options for this patient, given that he is having a knee surgery, include general or regional anesthesia. Regional anesthesia with or without sedation is preferable for this patient in order to avoid instrumentation of  the airway and thereby minimize risks of airway irritation and hyperreactivity. If for some reason a general anesthesia is necessary, then using a laryngeal mask airway is preferable to an endotracheal tube, since the latter acts as a foreign body in the patient’s trachea and can thus cause bronchospasm.

APPROACH TO

Anesthesia in a Patient with Reactive Airways

DEFINITION

SUPRAGLOTTIC AIRWAY DEVICES: Airway adjuncts such as a laryngeal mask airway (LMA) which are positioned in the pharynx or hypopharynx above the vocal cords.

CLINICAL APPROACH

Preoperative Evaluation

Preoperative evaluation of a patient with asthma includes a detailed asthma history, and a focused physical examination. The history should include the following: recent upper respiratory infection, allergies, possible bronchospasm “triggers” (such as smoke, pets, dust, cold, or seasonal changes), medications used for symptom prevention and treatment, and occurrence of dyspnea at night or early morning. It is also useful to know the frequency and severity of the attacks. For example, is his asthma sufficiently severe to warrant steroids, if so, when did he last need and/or take steroids? Is he dependent on steroids to control his asthma? Have any of the attacks warranted hospitalization? If so, when, and how frequently? How is he feeling today? For an elective procedure, is the patient’s condition optimized on the day of surgery?

Along with a detailed history, it is important to perform a focused preoperative physical examination. This examination should include observation for respiratory distress and accessory respiratory muscle usage, pursed lips during exhalation, signs of hypoxemia and breathlessness during speaking, and auscultation of the lung fields. Any wheezing, rhonchi, or deceased air movement should be noted.

Spirometry is a simple and acceptable means of assessing airway obstruction preoperatively. A decrease of 15% or more in FEV1 is considered clinically significant. Similarly, and particularly in the older patient with COPD, the magnitude of any response to bronchodilators (if present) is helpful to determine the preoperative course. A chest x-ray is not necessary, as it will not provide diagnostic information. If a patient is having significant respiratory distress and signs of hypoxemia, the procedure should be delayed, and an arterial blood gas analysis and pulmonologist consult should be ordered.

Preoperative management may include beta-2 adrenergic agonists and/or corticosteroids. Both have been shown to improve preoperative lung function and to decrease wheezing. For patients receiving general anesthesia, preoperative medications decrease the rate and severity of bronchospasm during intubation and other airway manipulations in both symptomatic and asymptomatic asthmatics. Studies have found that the preoperative administration of methyl prednisolone and salbutamol minimizes bronchoconstriction resulting from intubation. Bronchoconstriction occurs most often with general anesthesia, and especially with intubation and at emergence. The choice of a neuraxial or peripheral nerve block instead of general anesthesia could avoid many of the anesthesia-associated triggers of asthma.

Intraoperative Course

It is unlikely that regional or monitored anesthesia care (MAC) will cause an exacerbation of bronchospasm intraoperatively. However, if the patient declines regional anesthesia, or if the regional anesthetic is inadequate or inappropriate for the surgical procedure, then general anesthesia may be necessary. Bronchospasm generally occurs at the induction of general anesthesia and manipulation of the airway. The choice of induction drugs and airway device can impact airway reactivity. Propofol is an excellent choice for induction, in that it blunts the airway reflexes and relaxes airway musculature. Ketamine is also an option, because it causes bronchodilation. However, ketamine increases airway secretions and causes tachycardia, which can make it less favorable. If ketamine is used, excessive secretions can be blocked with an antisialagogue, such as glycopyrrolate, prior to induction.

Most opioids are desirable adjuvants to induction. Indeed, pretreatment with a large dose of opioids can blunt the foreign body response to intubation. Similarly spraying lidocaine into the trachea also blunts the foreign body response, as does intravenous lidocaine in a dose of 2 mg/kg.

Drugs which cause histamine release may also exacerbate bronchoconstriction. Morphine is a well-known member of this category, so opioids that do not cause histamine release, such as fentanyl, are preferred. Similarly, the selection of a neuromuscular relaxant that does not cause histamine release is necessary for asthmatic patients. Succinylcholine can cause histamine release, but given that it provides the most rapid neuromuscular relaxation, there are times its benefits outweigh its risks, such as for a patient with mild asthma and a full stomach, or an anticipated difficult airway.

The type of devices used to secure the patient’s airway can significantly affect airway hyperreactivity. Endotracheal intubation causes more severe bronchospasm than placement of supraglottic devices such as a laryngeal mask airway (LMA) that do not enter the trachea, and thus do not exert a foreign body response. Use of an LMA or mask ventilation is desirable if appropriate for the surgical procedure, since these techniques cause less airway irritation than intubation.

All volatile anesthetics cause bronchodilation. However, they are also pungent, and can irritate the airway. Sevoflurane and halothane are the least pungent volatile anesthetics, and therefore the best choices for maintenance of anesthesia in patients with reactive airway disease. Desflurane is the most irritating, and can cause coughing and airway irritation, especially at high doses in a patient who is not deeply anesthetized prior to its inhalation.

Even after meticulous selection of induction drugs, airway management, and maintenance anesthesia, bronchospasm can still occur intraoperatively. Severe, refractive bronchospasm is one of the most frightening scenarios that an anesthesiologist faces. Prompt recognition and an immediate treatment for bronchospasm is imperative when caring for an asthmatic patient. If an intubated patient experiences bronchospasm, ventilation becomes more difficult. Higher peak inspiratory pressures are needed to deliver the same tidal volume. The end-tidal capnograph may show a tracing with a steep slope (see Figure 24–1), reflecting the obstruction, and prolongation of exhalation during bronchospasm. If bronchospasm is so severe that adequate tidal volumes for gas exchange cannot be delivered, the patient will become hypoxemic. Auscultation of the patient’s lung fields may yield wheezing and/or decreased air movement.

Prior to administering medications to treat bronchospasm, the anesthesiologist needs to search for a definable trigger for the bronchospasm, and if a trigger is identified, eliminate it immediately. However, in the case of intubation- triggered bronchospasm, it may or not be appropriate for the endotracheal tube to be removed. The second issue is whether depth of anesthesia is appropriate. Bronchospasm can reflect an inadequate depth of anesthesia. If this is the case, then additional anesthetics should be administered immediately. Both intravenous and inhalation agents can be utilized to rapidly deepen the level of anesthesia in order to halt the bronchospasm.

The use of beta-2 agonists, such as albuterol, to increase bronchodilation is appropriate. However, when using an inhaled beta-2 agonist intraoperatively, 

Figure 24–1. Effect of airway obstruction on the capnograph. (Reprinted from: Morgan GE Jr,Mikhail MS, Murray MJ, eds. Clinical Anesthesiology, 4th ed.New York, NY: McGraw-Hill, 2006:575.)

very little actually reaches the airways during positive pressure ventilation, so more than the usual dosage will be needed. Beta-2 agonist delivery can be improved if the drug is administered into the inspiratory limb of the breathing circuit near the endotracheal tube. In addition, the action of the beta-2 agonists may be greater if the ventilator’s inspiratory to expiratory time (I:E) ratio is altered to lengthen the expiratory time. If inhalational beta-2 agonists do not attenuate the bronchospasm, then epinephrine should be considered. An intravenous bolus of 25 to 50 μg of epinephrine will reduce or eliminate bronchospasm in most patients. If bronchospasm persists despite increased depth of anesthesia and appropriate treatment, the patient may be suffering from status asthmaticus. Status asthmaticus necessitates even more aggressive intervention, cessation of the most operations, and treatment in the intensive care unit. While corticosteroids can be effective in preventing intraoperative bronchospasm if given prior to the operation, they are not effective in treating acute bronchospasm.

Postoperative Care

The symptoms of asthma can still occur after extubation and prior to discharge from the post-anesthesia care unit (PACU). While it is less likely to happen at this time than intraoperatively, the patient should still be observed for dyspnea, wheezing, and oxygen desaturations in the postoperative period. Should symptoms occur, the treatment involves the elimination of triggers and administration of beta-2 agonists via aerosolized respiratory treatment, such as nebulized albuterol and ipratropium. Once this is completed and the patient has recovered from anesthesia, his risk of bronchospasm returns to baseline.

Comprehension Questions

24.1. Which of the following is an aspect of a comprehensive perioperative evaluation of the asthmatic patient?

A. History of wheezing and treatments for asthma

B. Chest x-ray

C. An ECG

D. Computerized tomography of the lungs

24.2. At which of the following times during a general anesthetic is bronchospasm most likely?

A. Induction

B. Intubation

C. LMA insertion

D. Extubation

24.3. Which of the following is the first treatment for an anesthetized patient experiencing bronchospasm?

A. Administer inhalational beta-2 agonists

B. Administer additional anesthetic(s)

C. Administer neuromuscular blocking agent

D. Administer intravenous epinephrine

ANSWERS

24.1. A. A focused history and physical examination are absolutely necessary. Should the history and physical examination yield information that would require further evaluation, bedside spirometry and/or arterial blood gas analysis can also give important information as to the state of the patient’s asthma. Answer B, a chest x-ray, will not give information regarding the asthmatic state of a patient nor will it show bronchospasm. Chest tomography is unlikely to be helpful in the preoperative evaluation of the asthmatic patient.

24.2. B. Although bronchospasm can occur at all the times posed in this question, initial manipulation or instrumentation of the airway is the most likely time for bronchospasm to occur. During general anesthesia, intubation is more likely to cause bronchospasm than other methods of airway management, such as the laryngeal mask airway.

24.3. B. Administer additional anesthetic(s) to deepen the level of anesthesia, is the first treatment for bronchospasm because it is quick to administer. Inhalational beta-2 agonists, volatile anesthetics, and intravenous drugs with beta-adrenergic activity (epinephrine) can all attenuate bronchospasm. C, neuromuscular blocking agents, have no effect on bronchospasm. In fact, some neuromuscular blocking agents can precipitate a bronchospasm if they cause histamine release.

Clinical Pearls

➤ Information obtained during the preoperative examination, pretreatment with beta-2 agonists, and/or steroids can help predict the risk and prevent or reduce the incidence of bronchospasm during the perioperative period.

➤ Airway manipulation, especially endotracheal intubation, is the most likely time that bronchospasm will occur.

➤ The treatment of intraoperative bronchospasm includes eliminating any triggers, increasing depth of anesthesia, and administering drugs with beta-2-adrenergic activity.

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