A 54-year-old man with a 30-pack-year smoking history undergoes laparoscopic cholecystectomy after an episode of biliary pancreatitis. On the third postoperative day, he is found to be mildly hypoxemic at 90% on room air. His temperature is 36.7° C (98° F), blood pressure is 130/80 mm Hg, heart rate is 90/min, and respirations are 22/min. Lung auscultation shows decreased breath sounds at the bases. Arterial blood gas analysis results are as follows: Which of the following most likely explains the observed findings?

Question

A 54-year-old man with a 30-pack-year smoking history undergoes laparoscopic cholecystectomy after an episode of biliary pancreatitis.  On the third postoperative day, he is found to be mildly hypoxemic at 90% on room air.  His temperature is 36.7° C (98° F), blood pressure is 130/80 mm Hg, heart rate is 90/min, and respirations are 22/min.  Lung auscultation shows decreased breath sounds at the bases.  Arterial blood gas analysis results are as follows:  Which of the following most likely explains the observed findings?

Quizplus · Accepted Answer

Atelectasis is one of the most common postoperative pulmonary complications and is particularly common after abdominal and thoracoabdominal surgery. Following such surgeries, pain and changes in lung compliance can cause impaired cough and shallow breathing. Shallow inhalations limit recruitment of alveoli at the lung bases, and weak cough predisposes to small-airway mucus plugging. This results in hypoxia (low pO₂), which stimulates an increase in respiratory rate, causing low pCO₂. Atelectasis can be asymptomatic or manifest as increased work of breathing. It is most likely to occur after the second postoperative night to the fifth postoperative night. Radiologic findings demonstrate loss of lung volume due to the collapse of lung tissue. Adequate pain control, deep-breathing exercises, directed coughing, early mobilization, and incentive spirometry decrease the incidence of postoperative atelectasis. (Choice A) General anesthesia impairs laryngeal defenses, predisposing to aspiration of gastric contents. Residual effects of general anesthesia can also cause hypoventilation. Both the aspiration and residual anesthetic effects usually appear within the first few hours after surgery, often before the patient leaves the perioperative unit. Signs and symptoms of aspiration generally include sudden-onset dyspnea, cough, fever, and rhonchi/crackles on examination. (Choice B) Bronchospasm is common in the postoperative period, particularly in patients with underlying chronic obstructive pulmonary disease or asthma. Wheezing and dyspnea would be expected in addition to hypoxemia. (Choice C) Diaphragmatic paralysis may occur as a consequence of phrenic nerve injury from thoracic surgery, cervical manipulation, or tumor compression but is less likely during abdominal surgery. Unilateral diaphragmatic paralysis is often asymptomatic. Bilateral diaphragmatic paralysis causes hypoxemia; rapid, shallow breathing; orthopnea; and even respiratory failure. (Choice E) Ventilator-associated pneumonia may occur in patients on assisted ventilation for >48 hours and is a result of impairments in the lungs' natural defenses. Fever and hypoxia are common, and Pseudomonas infection must be considered. This patient has not been ventilated for >48 hours and is afebrile, making this diagnosis unlikely. Educational objective: Atelectasis is a common postoperative complication that results from shallow breathing and weak cough due to pain. It is most common on postoperative days 2 and 3 following abdominal or thoracoabdominal surgery. Adequate pain control, deep-breathing exercises, directed coughing, early mobilization, and incentive spirometry decrease the incidence of postoperative atelectasis. References: Atelectasis as a cause of postoperative fever: where is the clinical evidence? (http://www.ncbi.nlm.nih.gov/pubmed/21527508) Incentive spirometry: 2011. (http://www.ncbi.nlm.nih.gov/pubmed/22008401)

A 54-Year-Old Man with a 30-Pack-Year Smoking History Undergoes Laparoscopic