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The Highs and Lows Thyroid Problems in the ICU

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1 The Highs and Lows Thyroid Problems in the ICU
Daniel Orr

2 Thyroid - Hypothyroidism
Definition Defect within the hypothalamic-pituitary-thyroid axis, with the net result of inadequate thyroid hormone production Majority are primary - affecting thyroid gland itself Causes include Hashimoto’s thyroiditis Thyroidectomy Radioiodine & Deficiency/excess Drugs Intentional - carbimazole/propylthiouracil Side effect - lithium, amiodarone

3 Thyroid - Myxoedema Coma
Definition Misnomer Severe Hypothyroidism with Altered mental state Hypothermia Other organ failure Typically triggered by underlying illness or event

4 Thyroid - Myxoedema Coma
Incidence Rare F>M (80%) Elderly, > 60 years 90% cases during winter months Mortality ~ 30%

5 Thyroid - Myxoedema Coma
Clinical Findings Preexisting hypothyroid symptoms (collateral from relatives) General Fatigue, weight gain, cold intolerance, constipation Anaemia Specific Myxoedema, skin, hair, face, tongue, hoarseness Eye signs

6 Thyroid - Myxoedema Coma
Clinical Findings - All organ systems affected CNS Altered state of consciousness typical Lethargy, obtunded Seizures possible Thermoregulation Depression of hypothalamic function Patients typically cool, temperatures 24oC reported! Normothermia/hypothermia may represent sepsis

7 Thyroid - Myxoedema Coma
CVS Overall reduction in metabolic requirements, therefore reduction in cardiac output Bradycardia, decreased myocardial contractility Reduced pulse pressure with diastolic hypertension, or hypotension Cardiac failure rarely seen owing to reduced cardiac demands

8 Thyroid - Myxoedema Coma
Resp Hypoventilation typical Results in respiratory acidosis and hypoxaemia Owing to central depression of respiratory drive, and responsiveness to O2 and CO2 Pump failure Sleep apnoea

9 Thyroid - Myxoedema Coma
Metabolic & Renal Hyponatraemia Secondary to decreased renal perfusion (increased creatinine) and impaired free water clearance (SIADH) May be significant enough to contribute to alteration in mental state Other electrolyte disturbance may occur by similar mechanisms Hypoglycaemia Occurs concomitantly with hypothyroidism, even in the absence of adrenal insufficiency or hypo-pituitary disease

10 Thyroid - Myxoedema Coma
Pathogenesis Overall decrease in oxygen and substrate usage by all organ systems CVS Myocardium Alteration in gene expression Both systolic and diastolic function depressed Failure of contraction, compliance and filling Rhythm disturbance PVCs Torsade

11 Thyroid - Myxoedema Coma
Pathogenesis CVS Vasculature Decreased release of nitric oxide, promoting increased vascular resistance Perfusion Overall reduction, but tissue oxygenation reduced also, so A-V O2 difference preserved

12 Thyroid - Myxoedema Coma
Pathogenesis Trigger Intercurrent illness LRTI, UTI AMI, GIH, CVA Should be investigated for and excluded

13 Thyroid - Myxoedema Coma
Diagnosis Based initially on history, examination and exclusion of other forms of coma High TSH and low T4 useful in confirming diagnosis, but clouded somewhat in secondary hypothyroidism (Low TSH and T4) Other findings include Anaemia (normochromic, normocytic) Normal WCC Raised CK (skeletal muscle source)

14 Thyroid - Myxoedema Coma
Management Specific Replacement of thyroxine mainstay of treatment Exact means of replacement controversial Bolus dose of T3/T4 to commence followed by ‘intermediate’ dosing Both high and low doses associated with increased mortality

15 Thyroid - Myxoedema Coma
Management Considerations Availability of intravenous preparations (owing to ileus) T3 v T4 v Combination Precipitation of AMI, arrhythmia Corticosteroids Use of corticosteroids recommended until coexisting adrenal insufficiency is excluded

16 Thyroid - Myxoedema Coma
Management Supportive Intubation & Ventilation Often required for decreased conscious state and correction of respiratory acidosis and hypoxia Ongoing hypoxia may persist secondary to intrapulmonary shunting Vascular tone Vasopressors often required in early stages

17 Thyroid - Myxoedema Coma
Management Supportive Fluid management Balance Volume resuscitation required, but risk of precipitating cardiac failure Appropriate fluids considered to allow for slow correction of Sodium (fluid restriction often advocated), consideration of HTS Thermoregulation Passive warming only, as active warming will precipitate shock as a result of vasodilitation

18 Thyroid - Myxoedema Coma
Management Supportive Empiric broad spectrum antibiotics Take cultures first

19 Thyroid - Myxoedema Coma
Complications Hypoglycaemia iv glucose may be required Arrhythmia Cardiac monitoring required Ileus/Megacolon LRTI Hyponatraemia Intubation May be difficult as a consequence of myxomatous change

20 Thyroid - Myxoedema Coma
Considerations Drug clearance Other endocrine disorders

21 Thyroid - Hyperthyroidism
Definition Excessive levels of circulating thyroid hormone Results in generalised acceleration of metabolic processes Aetiology Graves Toxic Adenoma/MNG Iodine induced TSH mediated Germ cell tumours Surgical Cause has implications for treatment

22 Thyroid - Hyperthyroidism
Incidence/Prevalence/Prognosis F>M 5:1 Prevalence 1.3% Clinical Features CNS Anxiety, emotional lability Weakness Tremor

23 Thyroid - Hyperthyroidism
Clinical Features Eyes/Skin Lid Lag Exophthalmos Sweating CVS Tachycardia, palpitations and AF Increased cardiac output, increased contractility Widening pulse pressure, decreased SVR Heart failure SOB

24 Thyroid - Hyperthyroidism
Clinical Features Resp Dyspnoea Increased O2 consumption and CO2 production Potential hypoxaemia and hypercapnia GIT Increased motility with diarrhoea and malabsorption

25 Thyroid - Hyperthyroidism
Pathogenesis T3 binds nuclear receptors upregulating genes responsible for calcium cycling in the cardiac myocyte Myocardium Increased heart rate, contractility, cardiac output, and myocardial oxygen consumption, AF a precipitant for heart failure Vasculature Reduction in SVR and diastolic pressure Pulmonary hypertension

26 Thyroid - Storm Life threatening thyrotoxicosis, often with a precipitant history Mortality > 10% Burch and Wartofsky scoring system designed to clarify the diagnosis

27 Thyroid - Storm CVS Thermoregulation CNS Tachycardia, rate related
Shock worst case scenario Heart failure, oedema, bibasal creps, pulmonary oedema Thermoregulation >40 degrees common CNS Agitation, delirium, or degree obtundation considered essential to diagnosis

28 Thyroid - Storm GIT Pathogenesis NVD, hepatic failure with jaundice
Typically a trigger Acute infection/Stress response - AMI/Trauma Both Thyroidal and non-thryoidal surgery Radioiodine treatment Occurs on a background (usually) of those with know hyperthyroidism

29 Thyroid - Storm Genesis thought to be related to
Decreased levels of thyroid binding globulin in above conditions, rather than raised total level of thyroid hormones, resulting in increased unbound fraction of T3 & 4 Increased number of adrenergic binding sites, resulting in increased sensitivity to catecholamines

30 Thyroid - Storm Diagnosis
Raised T4 (& 3) and TSH depending upon disorder Radioiodine uptake scan to differentiate

31 Thyroid - Storm Management Specific
Management of Thyroid storm is the same as for uncomplicated hyperthyroidism, but the patient should be managed in an intensive care environment Specific Beta Blockade Multiple forms Consideration of verapamil, if contraindicated Thionamide therapy Propylthiouracil, dual effect

32 Thyroid - Storm Iodine solutions Corticosteroids
Sodium ipodate Potassium iodide Lugol’s solution Corticosteroids Plasmapheresis/PD may be effective in removing excess thyroid hormone

33 Thyroid - Storm Supportive Active cooling, paracetamol Antiarrhythmics
Avoid aspirin due to PPB Antiarrhythmics Volume resuscitation/Diuresis Antibiotics Sedation/Intubation/Ventilation

34 Thyroid - Storm Complications Considerations
Airway complications as a result of goitre Considerations Anticoagulation for AF


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