Postoperative Airway Complications
Tara Kelly
Mazen Maktabi
Although anesthesiologists are well informed on optimization for safe intubation and intraoperative ventilation, less focus has been placed on postoperative airway complications. It has been reported that postoperative airway complications are relatively common (1.3% to 19%), almost 30% of all adverse events associated with anesthesia occur at the end of anesthesia or during recovery, and further emphasis and attention on this phase of anesthesia is needed. This chapter focuses on risk factors, diagnosis, and management of airway complications occurring in the early postoperative period.
As anesthesiologists, our first interaction with the postoperative patient is actually in the operating room, around emergence and the time of extubation. As stated by Popat et al, extubation “is not simply a reversal of the process of intubation because conditions are less favourable than at the start of anesthesia.” Adequate planning for tracheal extubation involves preoperative identification of patients with difficult airways. The Difficult Airway Society has created four steps for anesthesiologists to follow in the “Basic Algorithm”: planning for extubation, preparing for extubation, performing extubation, and providing postextubation care. This airway algorithm is further divided into “Low-Risk Algorithm” and an “At-Risk Algorithm” to optimize extubation based on patient and surgical specific factors.
PATIENT-SPECIFIC FACTORS
Because of the lack of consistency of research definitions regarding postoperative airway complications, limitations in identifying patient-specific factors exist. Specific factors that have been demonstrated to increase the risk of postoperative airway complications include male sex, age >60 years, diabetes, obesity, and obstructive sleep apnea (OSA).
Obstructive Sleep Apnea and Noninvasive Ventilation
Two types of noninvasive ventilation (NIV) are commonly used in the postoperative period: noninvasive continuous positive pressure ventilation and noninvasive positive pressure ventilation. Both types of NIV support and decrease the work of breathing, improve atelectasis to allow for better gas exchange, and reduce left ventricular afterload to improve cardiac output. The use of NIV postoperatively should be strongly considered in high-risk patient populations, including the elderly, obese, patients with a history of chronic obstructive lung disease, postabdominal and thoracic surgery patients, or those who use NIV at home. In high-risk populations, postoperative NIV reduces reintubation rates after surgery, decreases postsurgical risk of pneumonia, and increases hospital survival.
Obesity
Obese (body mass index [BMI] ≥30 kg/m2) and morbidly obese (BMI ≥ 35 kg/m2) patients present many challenges to the anesthesiologist, including the risk of postoperative airway complications. Anesthesiologists must
consider the high rate of OSA in obese populations because OSA is often associated with decreased pharyngeal tone that can be sensitive to anesthetics and opioids (Popat et al., 2012). In the postanesthetic care unit (PACU), obese patients should, if possible, be placed in a head and back up position at a minimum of 25 degrees to decrease the reduction of functional residual capacity, reduce atelectasis, and improve gas exchange. Obese patients have a susceptibility to obesity hypoventilation syndrome (OHS), which is defined as the combination of obesity (BMI ≥ 30 kg/m2), daytime awake hypercapnia (partial pressure of arterial carbon dioxide ≥45 mm Hg), and hypoxemia (partial pressure of oxygen ≤70 mm Hg) (Chau et al., 2012). Patients with OHS are at an increased risk for postoperative ventilatory decline in the PACU often secondary to opioids owing to their propensity for upper airway obstruction, impaired pulmonary mechanics, and depressed central respiratory drive. Often, these patients require and improve with NIV, as described earlier.
consider the high rate of OSA in obese populations because OSA is often associated with decreased pharyngeal tone that can be sensitive to anesthetics and opioids (Popat et al., 2012). In the postanesthetic care unit (PACU), obese patients should, if possible, be placed in a head and back up position at a minimum of 25 degrees to decrease the reduction of functional residual capacity, reduce atelectasis, and improve gas exchange. Obese patients have a susceptibility to obesity hypoventilation syndrome (OHS), which is defined as the combination of obesity (BMI ≥ 30 kg/m2), daytime awake hypercapnia (partial pressure of arterial carbon dioxide ≥45 mm Hg), and hypoxemia (partial pressure of oxygen ≤70 mm Hg) (Chau et al., 2012). Patients with OHS are at an increased risk for postoperative ventilatory decline in the PACU often secondary to opioids owing to their propensity for upper airway obstruction, impaired pulmonary mechanics, and depressed central respiratory drive. Often, these patients require and improve with NIV, as described earlier.
SURGICAL FACTORS
Surgical procedures lasting more than 4 hours and those performed on an emergent basis appear to increase the risk for postoperative airway complications. Patients undergoing surgical procedures of the tonsils, adenoids, vocal cords, and trachea are at increased risk of postoperative airway events. In addition, surgical procedures that are in the prone position increase the risk of postoperative airway events, given the increased edema of the airway during the procedure. Similarly, thoracic procedures and abdominal procedures that involve the diaphragm also increase the risk of postoperative airway and pulmonary complications.
Thyroid Surgery
Greater than 90,000 thyroid surgeries are performed per year in the United States. Thyroid surgery presents a number of causes for postoperative airway compromises. Transient and permanent recurrent laryngeal nerve (RLN) paralysis, hypocalcemia, tracheomalacia, and postoperative hematoma are potential life-threatening complications of the airways because they impact airway patency postoperatively.
Hematoma
The incidence of postoperative hematoma has been reported to range from 0.19% to 4%, with the greatest risk during the first 6 hours following thyroid surgery; however, this serious risk can persist throughout the first postoperative 24 hours. The concern of airway obstruction following hematoma formation is the rationale for postoperative hospitalization following central neck surgery. Risk is attributed to surgical technique, patient predisposition, and thyroid pathology. It has been found that patients who develop postthyroid surgery hematoma are 3 times more likely to die than patients who did not experience postoperative hematoma. Patient discharge within 24 hours is safe and recommended in specific patient groups. A “thyroid kit” should always be kept at the bedside of postoperative thyroid surgery patients. It should contain sterile basic surgical equipment (blades, scissors, surgical clamps, and gauzes) that facilitates opening and decompressing a postoperative thyroid hematoma. A high index of suspicion for a threatening hematoma should exist when patients complain of new onset of difficulty in breathing or developing hoarseness in the PACU. Management of acute hematoma causing respiratory compromise involves promptly alerting the surgical and PACU teams and, if needed, removing sutures and opening the wound to relieve airway compression. Emergent surgical exploration may then be indicated. It should be emphasized that early intervention in cases of developing postoperative thyroid hematoma is important because delay in management of airway compression will lead to impairment of lymphatic
and venous drainage with consequent increasing edema and swelling of the airway, in which case evacuation of the hematoma may not resolve airway compression. In such situations, a surgical airway can be lifesaving (Table 16.1).
and venous drainage with consequent increasing edema and swelling of the airway, in which case evacuation of the hematoma may not resolve airway compression. In such situations, a surgical airway can be lifesaving (Table 16.1).
TABLE 16.1 Clinical Findings Associated with Postoperative Wound Hematoma | ||||||||||||||||||||||||||||
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Hypocalcemia
Up to 83% of postthyroidectomy patients experience some degree of hypocalcemia postoperatively; however, a smaller subgroup requires treatment for symptomatic hypocalcemia. Patient populations with a higher rate of symptomatic hypocalcemia include patients with advanced thyroid cancers, Graves’ disease, or symptomatic hyperparathyroidism prior to surgery. Of note, although autotransplantation of at least one parathyroid gland during surgery minimizes the risk of permanent hypoparathyroidism, it is associated with an increased rate of acute hypocalcemia in the postoperative period. Airway compromise from hypocalcemia generally manifests 12 to 48 hours postprocedure as stridor and poor air movement, and may be associated with tingling in the lips.
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