Feline thyroid storm (Proceedings)


Feline thyroid storm (Proceedings)

Apr 01, 2010

1. Acute thyrotoxicosis
      A. Precipitating event
      B. Untreated thyrotoxicosis
      C. Partially-treated thyrotoxicosis
      D. Mortality in humans: 20-50%

2. Clinical signs
      A. Accentuated clinical features of hyperthyroidism
      B. Hyperpyrexia
      C. Diaphoresis
      D. Cardiac signs
           i. Sinus tachycardia
           ii. Cardiac dysrhythmia
           iii. Tachyarrhythmias, atrial fibrillation
           iv. Congestive heart failure
      E. altered mental status; metabolic encephalopathy
           i. agitation
           ii. emotional instability
           iii. seizures
           iv. coma
      F. vomiting
      G. diarrhea
      H. dehydration
      i. hypovolemia
      J. vascular collapse
      K. abdominal pain
      L. hypertension
      M. retinal detachment; sudden blindness

3. Clinicopathologic abnormalities
      A. Abnormalities associated with hyperthyroidism
           i. Mild erythrocytosis
           ii. Macrocytosis
           iii. Mature neutrophilia
           iv. Elevated liver enzymes
      B. hyperglycemia
      C. leukocytosis with left shift
      D. elevated serum calcium
      E. elevated total bilirubin
      F. elevated creatine kinase

4. Diagnosis
      A. Clinical signs
      B. Abnormal thyroid hormone levels
      C. Precipitating event
           i. Thyroid surgery
           ii. Infection, sepsis
           iii. 131I therapy

5. Treatment
      A. Thyrotoxicosis
           i. Methimazole
                1. orally
                2. transdermally
                3. rectally
                4. prevent new hormone synthesis
           ii. iodine preparations
                1. block release of preformed hormone
                2. iopanoic acid
                3. potassium iodide
                4. give 1 hour after first dose of methimazole
                5. may delay use of 131I
      B. Block effects of hormone peripherally
           i. B-blockers
                1. propanolol
                     a. may block conversion of T4 to T3
                     b. 2.5-5 mg bid-tid
                2. atenolol – 0.25-1 mg/kg po sid-bid
                3. esmolol - Loading dose of 200-500 mcg/kg IV over 1 minute; followed by a constant rate IV infusion of 25-200 mcg/kg/minute
           ii. Anti-hypertensives
                1. amlodipine 0.625-1.25 mg/cat sid
                2. benazapril 0.25-1 mg/kg PO sid-bid
                3. hydralazine 2.5 mg PO bid
      C. supportive care
           i. cooling measures for fever
           ii. fluids
           iii. 5-10% dextrose
      D. identification of precipitating cause
           i. treat the cause

Table 1
6. VI. Other Unusual Manifestations of Feline Hyperthyroidism
      A. Neurological
           i. Profound neuromuscular weakness
           ii. Dementia
           iii. Obtundation
           iv. Seizures
      B. Cardiovascular

           i. heart failure
           ii. pleural effusion

Table 2

           iii. pulmonary edema
           iv. pulmonary hypertension
           v. severe hypertensive disease