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Difficulty: Very hardPreoperative and Postoperative Care

A 48-year-old woman is evaluated in the post-anesthesia care unit two hours after an elective laparoscopic cholecystectomy for symptomatic cholelithiasis. Her medical history is significant for major depressive disorder and Graves disease. Her home medications include sertraline 100 mg daily and methimazole 5 mg daily, though she admits to missing several doses of methimazole over the past month. Anesthesia was induced with propofol and succinylcholine, and maintained with sevoflurane. Fentanyl and ondansetron were administered during the procedure.

The patient is now severely agitated and disoriented. Her temperature is 39.4°C (102.9°F), heart rate is 148/min, blood pressure is 172/95 mmHg, and respiratory rate is 24/min. Physical examination reveals a profusely diaphoretic and flushed woman. Her pupils are dilated. Neurological examination demonstrates spontaneous ocular clonus. Deep tendon reflexes are 4+ in both the upper and lower extremities, with sustained ankle clonus present bilaterally. Her abdomen is soft with hyperactive bowel sounds. No muscle rigidity is noted.

Which of the following are the most appropriate immediate steps in the management of this patient? (Select 2)

  1. Administration of intravenous lorazepamAnswer
  2. Administration of oral cyproheptadineAnswer
  3. C
    Administration of intravenous propranolol and propylthiouracil
  4. D
    Administration of intravenous dantrolene
  5. E
    Administration of intravenous haloperidol

Answer

The most appropriate immediate steps are the administration of intravenous lorazepam and the administration of oral cyproheptadine.
This patient is exhibiting classic signs of Serotonin Syndrome, precipitated by the combination of her home SSRI (sertraline) and intraoperative serotonergic medications (fentanyl and ondansetron). The triad of Serotonin Syndrome includes autonomic instability (hyperthermia, tachycardia, diaphoresis), altered mental status (agitation, delirium), and distinct neuromuscular hyperactivity (spontaneous clonus, ocular clonus, hyperreflexia). The initial management of moderate to severe Serotonin Syndrome centers on discontinuing all serotonergic agents, providing supportive care, and administering intravenous benzodiazepines (e.g., lorazepam) to control agitation, lower heart rate, and reduce muscle hypertonicity. If symptoms are severe or refractory to benzodiazepines, oral cyproheptadine, a 5-HT2A receptor antagonist, is the specific antidote indicated to reverse the toxicity.

Step-by-Step Solution

1
Analyze the patient's preoperative medications and intraoperative exposures.
The patient takes sertraline (an SSRI) and received fentanyl and ondansetron intraoperatively, all of which are highly serotonergic agents.
Identifying overlapping drug mechanisms is critical in diagnosing postoperative neurotoxic syndromes.
2
Correlate the physical exam findings with the postoperative hyperthermic toxidromes.
The presence of hyperreflexia, spontaneous ankle clonus, ocular clonus, and hyperactive bowel sounds perfectly matches Serotonin Syndrome. It rules out Malignant Hyperthermia (which presents with rigidity and hyporeflexia) and Thyroid Storm (which lacks clonus).
Specific neuromuscular findings are the key differentiators between otherwise similar postoperative hypermetabolic states.
3
Select the targeted pharmacological interventions for the identified toxidrome.
Lorazepam is selected for immediate control of agitation and sympathetic hyperactivity, while cyproheptadine is selected as the specific pharmacological antidote for serotonin toxicity.
Proper management requires both supportive/symptomatic control and direct reversal of the underlying receptor overstimulation.

Key Concept

Postoperative Serotonin Syndrome is triggered by the combination of chronic SSRI therapy with serotonergic intraoperative medications (like fentanyl and ondansetron). It is differentiated from Malignant Hyperthermia and Thyroid Storm primarily by the presence of hyperreflexia, clonus, and hyperactive bowel sounds.
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Preoperative and Postoperative Care

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