วันเสาร์ที่ 14 กรกฎาคม พ.ศ. 2555

Thyroid emergency

Myxedema coma

• Hypothyroid habitus (generalized non-pitting edema, periorbital swelling) + multi-organ decompensation (bradycardia, hypotension, hypothermia, hypoventilation, altered mental status)

Ix: T3, FT4, TSH, cortisol level, metabolic panels, ABG, H/C, CXR, EKG, +/- CT, LP, cardiac enzyme

Treatment

Supportive care: ABC (oxygen, IV access, EKG monitor)

       o IV therapy: dextrose for hypoglycemia; water restriction for hyponatremia

       o Vasopressors

       o Hypothermia: passive rewarming using blanket

       o Steroids: hydrocortisone 100 mg IV q 8 hr

       o Empirical ATB (after H/C)

Thyroid replacement therapy (T4: slower, safer; T3: rapid onset, more arrthymia consider in severe myxedema coma)

       o T4 (levothyroxine) 4 g/kg IV then 100 g IV next 24 hr then 50 g IV (switch to 50–200 g/d PO when ambulate)

       o T3 (liothyronine or triiodothyronine) 20 g IV then 10 g IV q 8 hr until the patient is conscious (start < 10 g IV for the elderly or ACS)

Identify and treat precipitating factors

      o Infections

      o Sedatives

      o Anesthetic agents (e.g., etomidate)

      o Cold exposure

      o Trauma

      o Myocardial infarction or congestive heart failure

      o Cerebrovascular accident

      o GI hemorrhage

      o Contributing metabolic conditions include hypoxia, hypercapnia, hyponatremia, and hypoglycemia

Thyrotoxicosis

Dx: Preexisting hyperthyroidism +

         o Thermoregulatory: T > 37.7 c

         o CNS: agitation, confusion, seizure

         o GI-hepatic: N/V, diarrhea, abdominal pain, jaundice

         o CVS: CHF, AF

Ix: T3, FT4, TSH, cortisol level, metabolic panels, H/C, CXR, EKG, +/- thyroid antibody (grave disease), thyroid US with doppler flow (decrease flow in thyroiditis, exogenous thyroid)

Treatment

Supportive care: ABC (oxygen, IV access, EKG monitor)

         o Fever: external cooling; acetaminophen (ASA is contraindicated)

         o Dehydration: IV fluids, IV 5DW if hypoglycemic

         o Nutrition: glucose, MTV, thiamine, folate

         o Cardiac decompensation (AF, CHF): rate control and inotropic agent, diuretics, sympatholytics as required

         o Cholestyramine: decrease enterohepatic reabsorption

Inhibition of thyroid hormone release: (prefer PTU: block peripheral conversion of T4 to T3)

        o PTU load 600-1000 mg NG/PR then 200-250 mg q 4 h (total daily dose 1200-1500 mg/d) or

        o Methimazole load 40 mg PO then 25 mg q 4 h (total daily dose 120 mg/d). If given PR, 40 mg should be crushed in aqueous solution

Inhibition of new thyroid hormone production (> 1 h after PTU/methimazole): "Wolff-Chaikoff" effect

        o Lugol solution 8–10 drops PO q 6–8 h or Potassium iodide (SSKI) 5 drops PO q 6 h or Iopanoic acid (Telepaque®) 1 gm IV q 8 h x 24 h, then 500 mg bid or Ipodate (Oragrafin®), 0.5–3 gm/d PO (esp. thyroiditis/thyroid hormone overdose)

        o Lithium carbonate (if allergic to iodine, iodine overload–induced hyperthyroidism, amiodarone-induced thyrotoxicosis, agranulocytosis occurs with thionamides) 300 mg PO q 6 h (1200 mg/d) maintain serum lithium at 0.6-1 mEq/L (monitor serum lithium OD)

β-adrenergic receptor blockade (avoid amiodarone)

         o Propranolol 1-2 mg IV then q 10-15 min or 20-120 mg PO (160-320 mg/d). Treat CHF before starting propranolol (e.g., starting dobutamine)

         o Alternative tx if contraindication to β-blocker(inhibit catecholamine): reserpine, guanethidine

Preventing peripheral conversion of T4 to T3

        o Hydrocortisone 100 mg IV q 8 h until stable or dexamethasone 2 mg IV q 6 h

Treat precipitating event: (infection, AMI, DKA, etc.): H/C, EKG, Imaging(CXR, noncontrast CT)

Definitive therapy: Radioactive iodine ablation therapy or surgery

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