A 62-year-old man is hospitalized for an elective coronary artery bypass graft surgery. The patient has been having exertional chest pain and was found to have a left main coronary artery disease. Other medical issues include hypertension, hyperlipidemia, and stage 3 chronic kidney disease. The patient is a retired financial advisor with a 50-pack-year smoking history. He undergoes the surgery without operative complications and is successfully extubated the next day. Postoperative medications include atorvastatin, metoprolol, and morphine. On the third postoperative day, the patient is found to be progressively drowsy, lethargic, and difficult to rouse. Temperature is 36.1 C (97 F), blood pressure is 110/68 mm Hg, pulse is 112/min and irregular, and respirations are 9/min and shallow. Examination shows flat neck veins and mild bibasilar lung crackles. Pupils are 1 mm and equal. The patient withdraws all extremities equally to pain. ECG shows atrial fibrillation with rapid ventricular response. Fingerstick glucose level is 125 mg/dL. Laboratory results are as follows: The laboratory findings are not significantly changed compared to preadmission values. Which of the following is the most appropriate next step in management of this patient's altered mental status?

Question

A 62-year-old man is hospitalized for an elective coronary artery bypass graft surgery.  The patient has been having exertional chest pain and was found to have a left main coronary artery disease.  Other medical issues include hypertension, hyperlipidemia, and stage 3 chronic kidney disease.  The patient is a retired financial advisor with a 50-pack-year smoking history.  He undergoes the surgery without operative complications and is successfully extubated the next day.  Postoperative medications include atorvastatin, metoprolol, and morphine.  On the third postoperative day, the patient is found to be progressively drowsy, lethargic, and difficult to rouse.  Temperature is 36.1 C (97 F), blood pressure is 110/68 mm Hg, pulse is 112/min and irregular, and respirations are 9/min and shallow.  Examination shows flat neck veins and mild bibasilar lung crackles.  Pupils are 1 mm and equal.  The patient withdraws all extremities equally to pain.  ECG shows atrial fibrillation with rapid ventricular response.  Fingerstick glucose level is 125 mg/dL.  Laboratory results are as follows:  The laboratory findings are not significantly changed compared to preadmission values.  Which of the following is the most appropriate next step in management of this patient's altered mental status?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfdf_d36c_8f63_9358cc7f9e70_MD0005_00 This patient has the triad of depressed respiratory rate with shallow breaths, small pupils, and depressed mental status, consistent with acute opioid intoxication. Reduced bowel sounds are also common. The best predictor of acute toxicity is a respiratory rate <12/min as opioids act directly on brainstem respiratory centers to produce respiratory depression, resulting in decreased depth and frequency of breaths (leading to respiratory acidosis). Opioids also decrease both the hypercapnic and hypoxic respiratory drive through interaction with central and peripheral chemoreceptors. In the setting of kidney disease, morphine carries a particularly high risk of opioid toxicity compared to many other opioids. Morphine undergoes a 2-step metabolic process to form the metabolites morphine-3-glucuronide and morphine-6-glucuronide (which is a more potent opioid receptor agonist than morphine); these metabolites are then eliminated by the kidney. Renal dysfunction allows morphine-6-glucuronide to accumulate and can potentially lead to acute toxicity; patients in the postoperative period are at particular risk for this clinical scenario. Immediate management of opioid toxicity involves the administration of intravenous naloxone, an opioid receptor antagonist, as well as ventilatory support in patients with apnea or extremely low respiratory rates. (Choice B) Atrial fibrillation (AF) is common after cardiac surgery, and AF with rapid ventricular response (eg, pulse >100/min) may result in hemodynamic instability and cerebral hypoperfusion. However, this patient's heart rate is only slightly above the acceptable range and significant hypotension is not present; in addition, although AF in general can be treated with diltiazem, calcium channel blockers may be ineffective in AF after cardiac surgery. (Choice C) Noncontrast head CT scan or other neuroimaging is an important consideration for patients with acute mental status changes, but in a patient with multiple signs and symptoms of opioid intoxication it should not delay the administration of naloxone. (Choice D) Coronary angiography will detect bypass graft closure, which can occur within 30 days after surgery and presents with postoperative ischemia and possible hemodynamic instability. ECG would be expected to show ventricular arrhythmia or evidence of ischemia. (Choice E) Symptomatic uremia can manifest with nausea, vomiting, neuropathy, pericarditis, lethargy, seizures, and coma, and is an indication for urgent hemodialysis. However, it usually occurs in the setting of end-stage renal disease or acute renal failure and is less likely in this patient with stable chronic kidney disease. Educational objective: Opioid intoxication presents with the triad of respiratory depression, miosis, and depressed mental status. Renal dysfunction can increase the risk of opioid toxicity, especially with morphine. Immediate management involves the administration of intravenous naloxone as well as ventilatory support when needed. References: What do we know about opioids and the kidney? (http://www.ncbi.nlm.nih.gov/pubmed/28117754)

A 62-Year-Old Man Is Hospitalized for an Elective Coronary Artery