CC
A 17-year-old male with a history of asthma is referred to your office for evaluation of symptomatic partially impacted third molars.
Asthma is seen in about 3% to 5% of the population and can occur in any age group; however, it is particularly common in children and young adults and is the most common chronic disease in this age group.
HPI
The patient is a high school student with a history of pain and recurrent episodes of pericoronitis of the mandibular third molars. He was referred by his general dentist for evaluation and treatment.
PMHX/PDHX/medications/allergies/SH/FH
The patient has a history of asthma, diagnosed at age 8 years. He states that his asthmatic episodes are usually exacerbated by exercise and seasonal allergies. (Other common triggers of asthma exacerbation include cold weather; irritant exposures such as tobacco smoke; recent upper respiratory infection; and certain medications, including nonsteroidal antiinflammatory drugs.) He has had two previous visits to the local emergency department (ED) secondary to acute episodes that did not readily respond to his albuterol (β 2 agonist) inhaler; he required intravenous (IV) methylprednisolone (a systemic corticosteroid), nebulized albuterol, and ipratropium (an anticholinergic bronchodilator). The episodes resolved without the need for endotracheal intubation. (ED visits and endotracheal intubation both correlate with the severity of the asthma.) The patient does not have a history of status asthmaticus (asthmatic episode poorly responsive to standard therapeutic measures). His last asthma attack was approximately 1 month ago. (The frequency of attacks is an indicator of the control of this patient’s asthma.)
His current medications include an albuterol metered-dose inhaler (MDI), used as needed, and montelukast (a leukotriene receptor antagonist) 10 mg/day. He routinely monitors his status with a peak flow meter. (Patients use this device to monitor changes in the forced expiratory volume in 1 second [FEV 1 ]; Fig. 106.1 .)
The patient states that he smokes occasionally. (Cigarette smoke is an airway irritant that may precipitate bronchospasm.) He also has a history of allergic rhinitis (hay fever) and eczema. There is a positive history of asthma in several of his family members. (In patients with an allergic component to their asthma, there frequently is a strong family history of asthma or other allergies. Genetic factors may play a role in the pathogenesis of asthma. However, it is important to mention that not all patients with asthma have allergies and that the association between asthma and allergies is not entirely clear.)
Examination
General. The patient is a well-developed, well-nourished male in no apparent distress.
Vital signs. Stable with normotensive blood pressure.
Oral and maxillofacial. Partially erupted, impacted third molars are noted. The tongue is normal in size. The patient has a class I skeletal and dental relationship. The maximal interincisal opening is 45 mm. The uvula and soft and hard palates are easily visualized; bilateral tonsils are within normal limits in size and recessed within the tonsillar crypts (Mallampati class I). The thyromental distance is greater than four finger widths. (Evaluation of the airway is important, especially in patients who may require advanced airway interventions.)
Cardiovascular. Regular rate and rhythm with no murmurs, gallops (S3 or S4), or rubs. (Patients with asthma can have other comorbidities, such as chronic obstructive pulmonary disease, which may produce “splitting” of the second heart sound with an accentuated pulmonic component.)
Chest. Bilaterally clear on auscultation. (The major symptoms during an acute asthmatic attack are cough, dyspnea, expiratory wheezing, and chest tightness. Wheezing is not pathognomonic for asthma and reflects airflow obstruction through a narrow airway).
Labs
No labs are indicated in the routine care of a patient with well-controlled asthma. However, patients whose asthma is poorly controlled are often referred for pulmonary function testing. The most objective and relevant tests for measuring the degree of airway obstruction in patients with asthma are the FEV 1 and the peak expiratory flow. In patients with well-controlled asthma, the FEV 1 should be 80% of the forced vital capacity (FVC). (Comparison of obstructive with restrictive pulmonary diseases reveals that the vital capacity and FEV 1 are decreased in both; however, in obstructive diseases, both the functional residual capacity [FRC] and the residual volume [RV] are increased, whereas in restrictive lung diseases, both the FRC and RV are decreased.)
Imaging
In the current patient, the panoramic radiograph is significant for partial bony impacted third molars.
Chest radiographs are not indicated in asymptomatic patients with a history of asthma and are not particularly helpful except for ruling out other diseases. During acute asthmatic exacerbations, the chest radiograph may reveal hyperinflation of the lung fields (flattened diaphragm) and decreased vascular markings.
Assessment
American Society of Anesthesiologists (ASA) class II patient with four impacted third molars, planned for extraction under IV sedation anesthesia.
The ASA classification ASA II is defined as a patient with a mild systemic disease that is well-controlled and poses no limitations for daily activities.
Treatment
After reviewing the risks, benefits, and alternatives, the patient elected to have his third molars removed under IV general anesthesia the next day. The patient was instructed to record his peak flow the morning of the surgery and to bring his albuterol MDI with spacer to the office. (Spacers are devices used to increase the effectiveness of medication delivery.)
The day of surgery, the patient’s lungs were clear on auscultation bilaterally. (Because of the episodic nature of asthma, pulmonary auscultation should be conducted routinely before surgery.) After the patient had been prepared for surgery, he self-administered three puffs of albuterol (90 μg per puff) using his spacer. IV general anesthesia was achieved with midazolam 5 mg, fentanyl 50 μg, and propofol titrated to effect. (Propofol is the preferred general anesthetic for patients with asthma because it has shown to attenuate the bronchospastic response to intubation in both patients with and without asthma, whereas IV methohexital [Brevital] is more often associated with bronchoconstriction in response to endotracheal intubation during induction compared with propofol.)
Upon removal of the last third molar, the patient became diaphoretic, agitated, tachycardic (140 bpm), and tachypneic, with shallow breaths (25 per minute). (Tracheal tugging, use of accessory muscles of respiration, and intercostal retractions are other signs of severe asthmatic exacerbation.) The surgical sites were packed, the oropharynx was suctioned, and the tongue was retracted as the airway was repositioned and supported. The patient’s condition continued to deteriorate, with a progressive decline in oxygen saturation as measured by the pulse oximeter. Inspiratory suprasternal retractions revealed the obstructive nature of the patient’s condition. The diagnosis of an acute asthmatic attack was made. Two puffs of albuterol were given, in addition to two puffs of ipratropium bromide, while the vital signs were monitored closely. Supplemental 100% oxygen was delivered via a full face mask. Minutes later, the patient began to show worsening signs of respiratory distress, with a further decrease in the pulse oximeter reading to below 85%. Emergency medical services (EMS) was activated. Meanwhile, 0.5 mg of a 1:1000 solution of epinephrine was injected subcutaneously. An attempt to mask ventilate with 100% O 2 revealed airway resistance and chest tightness. Positive-pressure ventilation using the bag-mask technique was unsuccessful despite airway repositioning. A 10-mg dose of IV succinylcholine was given, and the patient’s anesthesia was deepened with 50 mg of IV ketamine. (Ketamine is a dissociative agent with potent bronchodilatory effects. Causes of bronchospasm often are attributed to light anesthesia; therefore, ketamine is a valuable drug to consider.) The patient’s airway soon became easier to ventilate with the bag-mask technique with 100% oxygen at a flow rate of 12 L/min. (Consideration should be given to administration of diphenhydramine 50 mg IV in cases of suspected allergic response; 20 mg of dexamethasone IV can also be used to reduce the inflammatory response.) The patient responded to these measures, showing a gradual rise in the pulse oximeter reading, diminished chest wall rigidity, and improved air exchange and compliance. His vital signs normalized, except for a persistent tachycardia (a residual side effect of repeated doses of sympathomimetics is tachycardia). Upon arrival of EMS, the patient was transported to the hospital for further observation of his acute asthmatic event.
Complications
Complications arising in patients with asthma range from mild wheezing and dyspnea to severe bronchospasm, hypoxia, and death. A positive respiratory history (upper respiratory infection in the previous 2 weeks, nocturnal dry cough, wheezing during exercise, and wheezing more than three times in the past 12 months) was associated with an increased risk of bronchospasm, perioperative cough, desaturation, or airway obstruction. Bronchospasm is a life-threatening emergency that must be treated as soon as it is recognized. In the office setting, it is important to alert EMS as soon as possible because the patient’s condition may deteriorate rapidly. The incidence of bronchospasm is low in patients with well-controlled asthma who are undergoing outpatient IV general anesthesia.
Bronchospasm is the acute manifestation of asthma. It results in increased airway resistance, which causes a decrease in the ratio of FEV 1 to FVC (see Fig. 106.1 ). Signs and symptoms of bronchospasm include dyspnea, stridor, wheezing, mucus secretion, and hypoxia. Initial treatment should include 100% oxygen and an inhaled short-acting β-2-selective adrenergic agonist (SABA). β 2 agonists relax the smooth muscle in bronchial walls and produce bronchodilation.
The clinician should also look for causes of the asthma exacerbation, such as undiagnosed latex allergies or medication allergies. Urticaria, pruritus, and facial edema are findings consistent with allergic reactions that may produce bronchospasm. If an allergic reaction is suspected, diphenhydramine and corticosteroids should be administered intravenously. Administration of epinephrine may be indicated in patients experiencing bronchospasm refractory to inhaled β 2 agonists; the most common dose and route of administration are 1 mg injected subcutaneously.
Ipratropium, a short-acting muscarinic antagonist, in conjunction with SABA used in the setting of acute asthma exacerbations has proven to decrease the likelihood of hospital admission compared with SABA alone. In addition, systemic glucocorticoid therapy is essential for the resolution of asthma exacerbations that are refractory to intensive bronchodilator therapy because the persistent airflow obstruction is likely attributable to airway inflammation and intraluminal mucus plugging. Early administration is warranted in the case of asthma exacerbation.
If bronchospasm persists and the patient is hypoxic, intubation is indicated. It is important to realize that intubation does not protect against or treat the bronchospasm. However, it facilitates ventilation of the narrowed airways and allows effective delivery of nebulized medications. If mechanical ventilation is used after intubation, it is important to be mindful that asthma is an obstructive airway disease and that overzealous high pressure or flow on inspiration can cause barotrauma, resulting in either a pneumothorax or tension pneumothorax.
Discussion
Asthma is a common chronic respiratory condition that can present with acute exacerbations. It affects both children and adults and is highly variable in severity, response to treatment, and clinical presentation. Asthma is a form of obstructive airway disease characterized by an acute and reversible increase in airway resistance. Recent evidence suggests that asthma causes changes in the respiratory epithelium. The prevalences of asthma are 8.0% in adults and 6.5% in the pediatric population. There is evidence that this is increasing in the United States, with higher prevalence in those from areas with the lowest annual household income compared with those from areas with higher household incomes.
The various types of asthma are categorized according to the underlying cause of the exacerbation. These types may include atopic or IgE-mediated, exercise-induced, occupational, infectious, or aspirin-induced asthma. Although the mediators that produce an acute asthmatic attack vary, the resulting physiologic responses are similar for all types of asthma. Because airway resistance is inversely related to the diameter of the bronchial lumen, pediatric patients are predisposed to rapid decompensation during bronchospasm ( Fig. 106.2 ).
