Endocrine Flashcards
describe the causes of adrenal insufficiency
can be broken into primary and secondary.
Primary-
Autoimmune (polyglandular autoimmune syndrome type 1 and 2)
Infections (Tb, CMV, HIV, cryptococcus, toxoplasmosis)
Fibrosis
Infarction
Adrenal Hemorrhage
Metastatic disease (lung, gastric, breast)
Drugs- decreased steroid synthesis (Ketoconazole, metryapone)
Drugs- increased steroid metabolism (Rifampin, dilantin)
Genetic- familial glucocorticoid deficiency/Adrenoleukodystrophy)
Iatrogenic- bilateral surgical removal/embolization.
Secondary-
exogenous steroid administration (can be referred as tertiary)
pituitary/hypothalmic disease
isolated ACTH deficiency
pituitary surgery
how much cortisol is usually secreted vs in times of stress.
Although normal adults secrete about 5 to 10 mg/m 2 of cortisol (or hydrocortisone) each day, during periods of acute stress the adrenal cortex can secrete as much as 100 mg/m 2 per 24 hours.
what are the signs and symptoms of adrenal insufficiency?
Signs and Symptoms Prevalence (%)
Weakness and fatigue 74–100
Weight loss 56–100
Hyperpigmentation 92–96
Hypertension 59–88
Hyponatremia 88–96
Hyperkalemia 52–64
Gastrointestinal symptoms 56
Postural dizziness 12
Adrenal calcification 9–33
Hypercalcemia 6–41
Muscle and joint pain 6
Vitiligo 4
For steroid use, how long of a course and at what dose is associated with adrenal insufficiency?
The HPA axis can be suppressed by a relatively modest dose of exogenous steroids administered for as short a period as 7 to 10 days. Except for low-dose prednisone (less than 5 mg/day) and alternate-day regimens, chronic administration of corticosteroids suppresses the HPA axis, and recovery of its function can take up to 12 months. Normalization of pituitary function comes first; adrenocortical function returns more gradually.
what is a thyrotoxic crisis?
Thyrotoxic crisis or thyroid storm is a life-threatening complication of hyperthyroidism characterized by a severe, sudden exacerbation of thyrotoxicosis. Patients with uncontrolled hyperthyroidism presenting for surgical or trauma care are at considerable risk of developing thyrotoxicosis. Therefore it is critical that anesthesiologists carefully assess patients who may be at risk of thyroid storm before proceeding with anesthesia and surgery.
Thyrotoxicosis factitia refers to thyrotoxicosis without true hyperthyroidism (e.g., intentional ingestion of synthetic thyroid hormone, ectopic thyroid hormone production) and is associated with decreased endogenous synthesis of thyroid hormone.
what are the components of the diagnostic criteria for a thyrotoxic crisis.
1) thermoregulatory dysregulation- increasing temperature
2) GI/hepatic dysfunction- abdominal symtpoms and jaundice
3) cardiovascular- tachycardia
4) CNS disturbance- agitation, delerium/psychosis, seizures.
5) Atrial fibrillation
6) congestive heart failure.
What are the management principles of thyrotoxic strom?
1) General Supportive Measures
- Intravenous (IV) fluids to restore intravascular volume
- Acetaminophen for hyperthermia (avoid aspirin, because it displaces T 4 from thyroid-binding globulin, thereby increasing free T 4 )
- Cooling blankets and cool environment
- Magnesium salts to reduce the severity and incidence of cardiac arrhythmias
- Correction of all electrolyte derangements
2) Inhibition of Thyroid Hormone Synthesis
- Propylthiouracil (PTU)—up to 1000 mg initially as a loading dose, then 250 mg orally or via nasogastric tube every 4 hours. It may take 6 to 8 weeks to achieve a full euthyroid state; PTU also inhibits peripheral conversion of T 4 to T 3 .
- Methimazole—this is the preferred agent today. Twenty to 30 mg orally or via nasogastric tube every 4 to 6 hours. Achieves a euthyroid state more quickly than PTU and has a lower incidence of agranulocytosis, hepatitis, and vasculitis.
3) Iodide Therapy
-Iodide inhibits thyroid hormone synthesis (called the Wolff-Chaikoff effect). However, one should delay iodide therapy for at least 4 hours after beginning PTU or methimazole therapy.
- Sodium iodide—1 g intravenously every 8 hours.
4) Inhibition of Peripheral Β-Adrenergic Activity
- β-Blockers, which also block peripheral conversion of T 4 to T 3 :
- Propranolol—0.5 to 1.0 mg/min intravenously, up to a total dose of 2 to 10 mg; repeat every 3 to 4 hours. After initial control with IV drug, treat with 20 to 40 mg orally every 6 hours; occasionally, a patient may require up to 2 g/day orally owing to the variability of hepatic metabolism in thyrotoxic individuals.
- Esmolol—IV bolus with 0.5 to 0.75 mg/kg, followed by IV infusion with 50 μg/kg per minute. If effect is inadequate after 5 minutes, repeat IV bolus and increase IV infusion to 100 μg/kg per minute; it may even be necessary to increase the infusion to 300 μg/kg per minute.
- Titrate β-blockade to achieve a heart rate of 80 to 90 beats per minute.
- If the patient has a history of reactive airway disease, use caution and a short-acting cardioselective agent such as esmolol, atenolol, or metoprolol.
- If β-blockers are contraindicated, other sympatholytic drugs (e.g., reserpine, a depleter of catecholamines, or guanethidine, an inhibitor of catecholamine release) may be useful as second-line agents.
5) Inhibition of Peripheral Conversion of T 4 to T 3
- PTU or methimazole (see dosages given earlier)
- Hydrocortisone 300 mg load, then 100 mg intravenously every 8 hours, or dexamethasone 2 mg intravenously or orally every 6 hours
What are the considerations for anaesthesia in hypothyroidism
1) CVS myxoedema crisis can cause hypotension and bradycardia, as well as pericardial effusions in extreme cases.
2) resp- pulmonary oedema, pleural effusions. Some reports of airway oedema resulting in a difficult airway. Depending on the aeitiology if there is a neck mass this can also make for a difficult intubation.
Ascities can also increase the intraabdominal pressure if present which effects ventilatory pressures.
3) emergence- The main observed issue in anaesthesia is delayed emergence and prolonged neuro-muscular block.
4) temp- more likely to have intraoperative hypothermia
