A Stormy Postoperative Course

From Medscape Critical Care > Case Challenges in Critical Care
A Stormy Postoperative Course
Jessica L. Bunin, MD; Christopher J. Lettieri, MD


Posted: 05/25/2011

Clinical Presentation
A 45-year-old Hispanic man has been admitted to the postanesthesia care unit. Following surgery to excise an abdominal mass, he was extubated in the operating room. He was stable upon admission to the postanesthesia care unit but rapidly developed a fever and tachycardia. His vital signs at that time were significant for a heart rate of 150 beats per minute, a blood pressure of 150/90 mm Hg, a respiratory rate of 30 breaths per minute, an oxygen saturation of 92% on 4 L/min oxygen via nasal cannula, and a temperature of 103°F. He was given acetaminophen, intravenous fluids, and dantrolene. He was started on a non-rebreather mask, packed in ice bags, and transferred to the surgical intensive care unit.

History and Physical Examination
Prior to surgery, the patient presented to his primary care physician with abdominal pain, weight loss, and loss of appetite lasting several months. A CT scan of his abdomen revealed a 13-cm x 8-cm x 11-cm right lower quadrant mass. With a history of an undescended testicle, excision was scheduled with the urology service. The surgical procedure, which lasted 5.5 hours, consisted of mass excision, nodal dissection, and placement of bilateral ureteral stents. The patients received 3 mg midazolam, 250 µg fentanyl, 600 mg propofol, 26 mg vecuronium, and sevoflurane throughout the case. There were no immediate complications.

The patient's history and physical examination revealed the following.

History
Medical history: hemorrhoids; undescended testicle
Habits: smokes 0.5 pack per day; social alcohol consumption
Medications: none, no over-the-counter supplements
Ill contacts: none known
Physical Examination
General: mildly sedated but alert and oriented
Vital signs: blood pressure, 132/68 mm Hg; pulse, 112 beats per minute; core temperature, 104.2°F; respirations, 25 breaths per minute with an oxygen saturation of 94% on 100% non-rebreather mask
Neurologic: nonfocal exam, cranial nerves intact, 5/5 strength throughout, normal reflexes, no rigidity, no spasticity, no tremor
Cardiovascular: tachycardia; otherwise normal exam
Respiratory: basilar crackles with good air movement
Abdomen: dressed wound, appropriately tender, no bowel sounds
Extremities: no edema
Lab Values and Imaging
WBC: 6.2 x 103/mm3
Hemoglobin: 9.4 g/dL; platelets 185,000/mm3
Electrolytes: within normal limits
Renal function: normal
Bicarbonate: 24 mEq/L
Arterial blood gas: pH 7.37/pCO2 41/pO2 101/98% on 100% non-rebreather mask
Creatinine kinase: 239%
Liver-associated enzymes within normal limits
Chest x-ray: pulmonary vascular congestion


What is the most likely diagnosis at this time?

Neuroleptic malignant syndrome
Thyroid storm
Serotonin syndrome
Malignant hyperthermia (MH)
Pheochromocytoma


Discussion: Case Diagnosis
Although all of the given choices are possible, the patient's findings are most consistent with thyrotoxicosis.

In neuroleptic malignant syndrome, one would expect to see fever and tachycardia as in this case, but the additional expected findings of rigidity on physical exam, elevated creatine kinase, transaminitis, hyperkalemia, and metabolic acidosis were absent. Additionally, this patient had not received any antipsychotic medications.

In serotonin syndrome, patients generally exhibit tremor, hyperreflexia, and clonus on exam. This patient did not have any of these signs, nor did he take any medications that are classically associated with this reaction.

MH is concerning, considering the perioperative presentation and the degree of elevation of the patient's fever. MH, however, typically occurs within an hour of induction of anesthesia. Given the delay of development of symptoms, lack of hypercarbia, absence of muscle rigidity, and normal acid-base status, MH is unlikely.

Pheochromocytoma, particularly immediately after excision, can present with hypertension and tachycardia. Although this patient did not present with the classic triad of headache, sweating, and tachycardia, this does not rule out the diagnosis. The patient had no symptoms associated with pheochromocytoma prior to the surgery, which makes the diagnosis less likely. Moreover, a severe fever is less likely in pheochromocytoma than in thyroid storm.

Thyroid studies. The patient's thyroid studies revealed an undetectable level of thyroid-stimulating hormone. His free T3 was 9.87 pg/mL (2.0-4.4 pg/mL); his free T4 was 3.19 ng/dL (1.01-1.79 ng/dL); and his thyroglobulin antibody and thyroid peroxidase antibody were positive. All of these findings are consistent with thyroid storm. Upon more specific questioning, the patient and his wife reported that for months prior to the surgery, the patient had heat intolerance, increased appetite, and anxiety. Many stressors can precipitate thyroid storm: surgery, trauma, infection, myocardial infarction, pulmonary embolism, discontinuation of antithyroid medications, parturition, excessive salicylates, and excessive iodine -- among others.[1] The physiologic stress of surgery precipitated this patient's acute decompensation.

Treatment
First-line treatment for thyrotoxicosis includes the thionamide class of medications, 2 of which are methimazole and propylthiouracil (PTU). These drugs inhibit thyroid follicular cell growth and function, reduce iodine organification, and inhibit iodotyrosine residue coupling.[1] In addition, PTU impairs the conversion of T4 to T3, which has the greater biologic activity. The most significant difference between these 2 agents is the half-life. The half-lives for PTU and methimazole are, respectively, 2 and 6 hours.[1] Given the additional benefit of reduced conversion to T3, PTU is often administered as the initial treatment, but methimazole allows for more reasonable dosing regimens when the patient has stabilized.

Iodine preparations such as Lugol's solution, saturated solution of potassium iodine, and intravenous potassium iodine are also given to prevent release of thyroid hormone. The administration of iodine agents must be delayed until at least an hour after administration of thionamides. This reduces the risk that the iodine will be used for production of new thyroid hormone as opposed to preventing release of thyroid hormone.[2]

Preventing the conversion of T4 to T3 reduces the effects of thyroid hormone. PTU can accomplish this goal, as can glucocorticoids and propranolol. Propranolol, like all beta-blockers, has the additional benefit of blocking the peripheral effects of thyroid hormone.[2] This dual effect makes it the beta-blocker of choice in thyroid storm.

In summary, treatment of thyroid storm requires several agents. Thionamides control production of thyroid hormone. Iodine controls release of thyroid hormone. PTU, glucocorticoids, or propranolol reduce conversion of T4 to T3, and beta-blockers control the peripheral effects of the hormone. Supportive care including cardiorespiratory support, cooling, hydration, and avoidance of perpetuating agents or stressors completes the mission.

Patient's Outcome
To return to the case, the patient was actively cooled. Within 2-3 hours, his temperature returned to normal, and the active cooling was discontinued without a subsequent rise in his temperature. With resolution of his fever, the remainder of his vital signs stabilized. He was started on PTU and propranolol with a plan to initiate glucocorticoids if he did not improve. All of his symptoms resolved rapidly. He was monitored overnight and transferred to the ward the next morning with endocrinology follow-up. Pathology of his abdominal mass revealed a seminoma.

[ CLOSE WINDOW ]
References
Nayak B, Burman K. Thyrotoxicosis and thyroid storm. Endocrinol Metab Clin North Am. 2006;35:663-686.
Ringel MD. Management of hypothyroidism and hyperthyroidism in the intensive care unit. Crit Care Clin. 2001;17:59-74.
Medscape Critical Care © 2011 WebMD, LLC