Transcript Thyroid-Problems-in-the-ICU
The Highs and Lows Thyroid Problems in the ICU
Daniel Orr
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
Thyroid - Myxoedema Coma
– Definition • Misnomer • Severe Hypothyroidism with – Altered mental state – Hypothermia – Other organ failure – Typically triggered by underlying illness or event
Thyroid - Myxoedema Coma
– Incidence • Rare – F>M (80%) – Elderly, > 60 years – 90% cases during winter months – Mortality ~ 30%
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
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 24 o C reported!
– Normothermia/hypothermia may represent sepsis
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
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
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
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
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
Thyroid - Myxoedema Coma
• Pathogenesis – Trigger • Intercurrent illness – LRTI, UTI – AMI, GIH, CVA – Should be investigated for and excluded
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)
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
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
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
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
Thyroid - Myxoedema Coma
• Management – Supportive • Empiric broad spectrum antibiotics – Take cultures first
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
Thyroid - Myxoedema Coma
• Considerations • Drug clearance • Other endocrine disorders
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
Thyroid - Hyperthyroidism
• Incidence/Prevalence/Prognosis – F>M 5:1 – Prevalence 1.3% • Clinical Features – CNS – Anxiety, emotional lability – Weakness – Tremor
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
Thyroid - Hyperthyroidism
• Clinical Features – Resp – Dyspnoea – Increased O2 consumption and CO2 production – Potential hypoxaemia and hypercapnia – GIT – Increased motility with diarrhoea and malabsorption
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
Thyroid - Storm
– Life threatening thyrotoxicosis, often with a precipitant history – Mortality > 10% – Burch and Wartofsky scoring system designed to clarify the diagnosis
Thyroid - Storm
– CVS • 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
Thyroid - Storm
– GIT • NVD, hepatic failure with jaundice – Pathogenesis • 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
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
Thyroid - Storm
• Diagnosis – Raised T4 (& 3) and TSH depending upon disorder – Radioiodine uptake scan to differentiate
Thyroid - Storm
• Management • 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
Thyroid - Storm
• Iodine solutions – Sodium ipodate – Potassium iodide – Lugol’s solution • Corticosteroids • Plasmapheresis/PD may be effective in removing excess thyroid hormone
Thyroid - Storm
– Supportive • Active cooling, paracetamol – Avoid aspirin due to PPB • Antiarrhythmics • Volume resuscitation/Diuresis • Antibiotics • Sedation/Intubation/Ventilation
Thyroid - Storm
• Complications – Airway complications as a result of goitre • Considerations – Anticoagulation for AF