Suspected thyroid storm in a cat anaesthetised for bilateral thyroidectomy

Abstract

A 14-year-old female neutered domestic short hair cat was referred for assessment of uncontrolled hyperthyroidism. The owners were advised that a bilateral thyroidectomy was required due to the presence of comorbidities that rendered radioiodine therapy inappropriate. During the procedure the cat exhibited unexpected extreme tachycardia, hypertension, hypercapnia, severe respiratory and metabolic acidosis and ventricular arrhythmias, which all resolved after removal of the thyroid glands. Recovery was complicated by the development of congestive heart failure and hypertension which were successfully managed and the cat was discharged five weeks after presentation. Thyroid storm was considered a possible explanation for the events that occurred during anaesthesia as well as the subsequent congestive heart failure and hypertension. Thyroid storm during anaesthesia has not been reported in animals. The similarities between the reported case and thyroid storm events in humans are discussed.

Long‐term survival in a dog with probable thyroid storm

“…There are only two published case reports of probable thyroid storm in veterinary patients. The cat described by Potter et al developed unexpected severe tachycardia, hypertension, hypercapnia, severe respiratory and metabolic acidosis, and ventricular arrhythmias while under anesthesia for thyroidectomy, all of which resolved upon removal of the thyroid gland 6 . The patient developed congestive heart failure and hypertension in recovery, which was also attributed to thyrotoxicosis and thyroid storm.…”

“…Thyroid storm is the most severe clinical manifestation of thyrotoxicosis 1 . However, this syndrome is poorly defined and only recently reported in veterinary medicine 4,6 . In humans, it is well‐described and associated with significant mortality in human emergency and intensive care units 10 .…”

“…8 Clinical signs of thyrotoxicosis are similar in dogs, cats, and humans and include agitation, diarrhea, hyperthermia, tachycardia, tachypnea, tremors, and weight loss. 4,6,9,12 Thyroid storm is the most severe clinical manifestation of thyrotoxicosis. 1 However, this syndrome is poorly defined and only recently reported in veterinary medicine.…”

“…It can occur secondary to excess thyroid hormone production in the thyroid follicles, release of preformed hormone, or ingested thyroid hormone 8 . Clinical signs of thyrotoxicosis are similar in dogs, cats, and humans and include agitation, diarrhea, hyperthermia, tachycardia, tachypnea, tremors, and weight loss 4,6,9,12 …”

“…In humans, thyroid storm is a well‐described clinical diagnosis based on the presence of thyrotoxicosis complicated by thermoregulatory, cardiovascular, central nervous system, and gastrointestinal or hepatic system decompensation 1 . The mortality rate in humans treated aggressively is 8%–25% and approaches 80%–100% in untreated patients 3–5 There are only two cases in the veterinary literature of probable thyroid storm: one cat who survived and one dog who did not 4,6 . This report describes the successful emergency management and long‐term survival of a dog with probable thyroid storm.…”