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AS - N935 Advanced Patho II > Endocrine - Thyroid/Parathyroid > Flashcards

Endocrine - Thyroid/Parathyroid Flashcards

1
Q

T3

A 
Triiodothryonine
10% synthesized & released by the thyroid gland
Also formed in liver & kidneys
3-4x more active than T4
Half-life 1-3 days
99.7% albumin bound
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2
Q

T4

A

Thyroxine
90% synthesized & released by the thyroid gland
Half-life 6-7 days
99.9% bound to thyroid binding globulin

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3
Q

Hypothalamus

A

Controls thyrotropin-releasing hormone TRH

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4
Q

Pituitary Gland

A

TRH stimulates thyroid-stimulating hormone to release from the anterior pituitary
TSH controls thyroid hormone production

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5
Q

Thyroid Gland

A

TSH action site

Synthesis & secretion T3 & T4

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6
Q

What’s active thyroid hormone form?

A

Free form

Drives patient metabolic state

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7
Q

Thyroid Function Tests

A

TSH
Serum T3/T4
Radioactive iodine uptake

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8
Q

TSH

A

Normal 0.4-5 milliunits/L

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9
Q

Subclinical Hyperthyroidism

A

TSH 0.1-0.4 milliunits/L

Normal levels free T3 & T4

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10
Q

Over Hyperthyroidism

A

TSH level <0.03 milliunits/L

↑T3 & T4

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11
Q

Subclinical Hypothyroidism

A

Myxedema
TSH level 5-10 milliunits/L
Normal levels T3 & T4

20% women over 60yo

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12
Q

Overt Hypothyroidism

A

Myxedema
TSH level >20 milliunits/L
↓T3 & T4

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13
Q

Pituitary Dysfunction

A

Admin exogenous TRH
Collect serum TSH concentration
Normal response ↑TSH
Hypothyroidism d/t pituitary disease (2° hypothyroid) TRH admin does NOT produce ↑TSH

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14
Q

Hyperthyroidism

A

TSH level <0.03 milliunits/L
↑free T3 & T4
Thyroid hormones not shutting off w/ low TSH

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15
Q

Hyperthyroidism Causes

A 
Graves disease - autoimmune disease caused by thyroid-stimulating antibodies that bind to TSH receptors in the thyroid → stimulating thyroid growth, vascularity, & hypersecretion
Toxic multinodular goiter
Autonomously functioning thyroid nodule
Thyroiditis - inflammation/infection
Exogenous thyroid hormone ingestion
Iodine-induced
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16
Q

Hyperthyroidism S/S

A

Anxious, restless, hyperkinetic
Flushed, diaphoretic, & heat intolerance
Protruding eyes (exophthalmos or proptosis)
Weakness, fatigue, insomnia
Tremors, weight loss, frequent bowel movements
↑MVO2, tachycardia, dysrhythmias, palpitations

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17
Q

Hyperthyroidism Treatment

A

Anti-thyroid medications
- Thionamides (Propylthiouracil) interfere w/ thyroid hormone synthesis, prevents T4 → T3 conversion, admin weeks to months, monitor thyroid function tests
Radioactive iodine (recurrent or persistent hyperthyroidism)
Thyroidectomy - only after euthyroid state achieved w/ medication

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18
Q

Thyroid Storm

A

Acute life-threatening hyperthyroidism
Mortality >20%
S/S include fever w/ diaphoresis, tachycardia (Afib or Vtach), cerebral dysfunction (confusion, psychosis, seizures), GI disorders (N/V or obstruction)
Causes - surgery, infection, IV contrast dyes, DKA, trauma, or thyroid palpation
Most often occurs postop d/t inadequately treated hyperthyroid patients

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19
Q

Thyroid Storm Treatment

A

Propylthiouracil (PTU) ↓production, conversion, & secretion thyroid hormone
Corticosteroids block T4 → T3 conversion
Ice packs & cooling
Correct acid-base abnormalities - oxygenation & ventilation
Hydration consider glucose containing fluids
Oxygen
β blockers ↓MVO2
Avoid SNS activation
Determine underlying cause

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20
Q

Hyperthyroidism Anesthetic Considerations

A

Pre-medications to block SNS
Avoid anticholinergics
Invasive monitoring (A-line)
Differentiate b/w MH & thyroid storm
Adequate anesthesia depth to avoid exaggerated SNS response
Avoid Ketamine, Ephedrine, Epi, or Dopamine
Treat hypotension w/ fluids & direct-acting vasopressor
Eye protection
Continue β blocker postop

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21
Q

1° Hypothyroidism

A

↓thyroid hormone production despite normal TSH
Most common causes are thyroid gland ablation d/t radioactive iodine therapy or surgery
90-95% all cases

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22
Q

2° Hypothyroidism

A

Hypothalamic or pituitary disease

5% all cases

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23
Q

Autoimmune Hypothyroidism

A

Autoantibodies block TSH receptors in the thyroid

Immune response destroys receptors rather than stimulating

24
Q

Hashimoto Thyroiditis

A

Autoimmune disorder, goiter, & hypothyroidism

Common in middle-aged women

25
Q

Hypothyroidism S/S

A

Slow, progressive
Mild - fatigues easily & weight gain despite ↓appetite

Moderate to severe - fatigue, apathy, listless, slow speech, cold intolerance, ↓sweating, constipation, menorrhagia, slow motor function, ↓GI function, dry hair & skin, large tongue, periorbital edema, cardiomyopathy, impaired baroreceptor function, bradycardia, hyponatremia, impaired ventilatory response to hypoxia & hypercarbia

26
Q

Hypothyroidism Diagnosis

A

1° (thyroid) ↓T3 & T4 levels ↑TSH
2° (pituitary) ↓T3 & T4 levels AND ↓TSH
Identify primary vs. secondary w/ TRH stim test

27
Q

Hypothyroidism Treatment

A 
L-thyroxine (Levothyroxine/Synthroid)
Synthetic T4 thyroxine
T4 → T3 
Onset 3-5 days PO (peak therapeutic effect 4-6 weeks)
IV 6-8 hours
28
Q

Hypothyroidism Anesthetic Considerations

A

Airway compromise 2° swollen oral cavity, edematous vocal cords, or goiter
↓gastric emptying ↑aspiration risk
Hypodynamic CV system ↓HR/SV/CO (phosphodiesterase inhibitors treat reduced myocardial contractility MOA not β receptor dependent)
↓ventilatory response to hypoxia & hypercarbia
Hypothermia risk
Anemia, platelet dysfunction, electrolyte imbalances, & hypoglycemia
↑sensitivity to sedatives & narcotics

29
Q

Myxedema Coma

A 
Rare, severe form hypothyroidism
Delirium or unconsciousness, hypoventilation, hypothermia, bradycardia, hypotension, & severe dilutional hyponatremia
Elderly women w/ hypothyroidism history
Mortality rate >50%
MEDICAL EMERGENCY
- IV thyroxine or triiodothyronine
- IV steroids
30
Q

Goiter

A

Thyroid gland swelling
Hyper OR hypothyroidism
Non-toxic goiters euthyroid → toxic multinodular goiter
Airway evaluation
Caution w/ respiratory depressants prior to airway airway securement

31
Q

Thyroid Surgery

Anesthetic Considerations

A

Euthyroid prior to surgery
Delay elective surgery 6-8 weeks
Airway compromise w/ goiters - nerve compression, tracheal deviation, & erosion
1-2 mos treatment w/ recent TSH & T3/T4 to evaluate treatment effectiveness
Recurrent laryngeal nerve monitor

32
Q

Thyroid Surgery Complications

A

RLN or SLN injury

Hypoparathyroidism d/t parathyroid gland blood supply damage

  • Hypocalcemia 24-48H postop
  • Stridor/laryngospasm (treatment IV calcium)

Tracheal compression d/t expanding hematoma (1st line treatment evacuation)

33
Q

RLN Injury

A

Abductor vocal cord muscle paralysis results in median/paramedian cord position
Unilateral = hoarseness
Bilateral = airway obstruction (reintubate or trach)

34
Q

SLN Injury

A

Voice weakness

Unable to create high tones “E”

35
Q

Parathyroid Glands

A

4 parathyroid glands
Produce parathyroid hormone (PTH)
Maintains normal plasma calcium concentration

36
Q

Parathyroid Hormone

A

PTH
Released into bloodstream via negative feedback
Dependent on plasma calcium concentration
Half-life 4 minutes
Average PTH level 8-51 pg/mL

37
Q

Hypocalcemia →

Hypercalcemia →

A

Releases parathyroid hormone

Suppresses PTH synthesis & release

38
Q

Calcitonin

A

Opposes PTH effects - lowers blood calcium
- Inhibits osteoclast activity in bones to promote Ca2+ storage
- Inhibits renal tubular cell Ca2+ reabsorption
- Inhibits Ca2+ absorption via intestines
Secreted by parafollicular cells in the thyroid
Stimulated by ↑serum calcium (hypercalcemia)

39
Q

Vitamin D

A

Fat-soluble
↑intestinal absorption Ca2+, magnesium, & phosphate
D2 (cholecalciferol) synthesis dependent on sun exposure
D3 (ergocalciferol)
Ca2+ homeostasis & metabolism
Receptors located intestines, kidneys, bone, & parathyroid gland

40
Q

Calcium

A

Total (bound & free) serum Ca2+ 9.5-10.5mg/dL
iCal 4.75-5.7mg/dL
50% bound to albumin, 40% ionized, 10% bound to chelating agents (phosphate, citrate, sulfate)

99% bone
1% coagulation factors, nerve & muscle excitability, & metabolic regulation (hormones & enzyme regulation)

41
Q

pH & Ca2+

A

Acidosis ↑serum Ca2+
↓pH ↓protein binding (more available ionized fraction)
Each 0.1 ↓pH ↑iCal by 0.05mmol/L

Alkalosis ↓serum Ca2+

42
Q

PTH Disorders

A 
↓PTH 
- DiGeorge syndrome
- CATCH 22
- Autoimmune
Parathyroid gland adenomas
43
Q

Hyperparathyroidism

A

Excessive PTH production

Most common cause of hypercalcemia >10.4mg/dL

44
Q

1° Hyperparathyroidism

A 
Parathyroid gland destruction
Excessive PTH secretion 
- Benign adenoma
- Hyperplasia
- Carcinoma
50% patients asymptomatic
45
Q

2° Hyperparathyroidism

A

Appropriate response to hypocalcemia (CKD)

46
Q

Hyperparathyroidism S/S

A

Symptomatic when Ca2+ 11.5-12mg/dL
Skeletal muscle weakness
Polyuria & polydipsia
↓GFR or kidney stones
Anemia
Prolonged PR interval, shortened QT, systemic HTN
Abdominal pain, vomiting, peptic ulcer, pancreatitis
Skeletal demineralization & pathologic fractures
Somnolence, ↓pain sensation, psychosis

47
Q

Hyperparathyroidism Diagnosis

A 
PTH assay
Vitamin D & Ca2+ levels
Renal function
CT scans
Previous thyroid surgery
48
Q

Hyperthyroidism Treatment

A

Medical management to treat mild, asymptomatic disease
- Mild hypercalcemia 12mg/dL (hydration)
- Moderate to severe hypercalcemia 13-15mg/dL (IV saline hydration & Furosemide to promote Na+/Ca2+ diuresis)
Surgical removal = definitive treatment
- Intraop PTH assay before & after adenoma removal
- Multiple gland hyperplasia need to identify all parathyroid glands

49
Q

Hypoparathyroidism

A

Absence or PTH secretion deficiency
Peripheral tissues resistant to hormone effects
Iatrogenic - surgical removal (thyroidectomy)
Results in hypocalcemia

50
Q

Hypocalcemia S/S

A 
Neuronal irritability
Fatigue
Mental status changes
Skeletal muscle spasms
Tetany
Seizures
Prolonged QT interval
CHF (chronic)
Hypotension (acute)

Acute hypocalcemia - stridor, laryngospasm, & apnea

51
Q

Hypocalcemia Treatment

A

Electrolyte replacement
Ca2+ & vitamin D
PO or IV magnesium replacement

Severe symptomatic 10% Ca2+ gluconate 10-20mL (peripheral) or 10% Ca2+ chloride 3-5mL (central) followed by continuous infusion 1-2mg/kg/hr

52
Q

Hypocalcemia Anesthetic Considerations

A 
Treat hypoglycemia prior to surgery
Anesthetic risks include ↓cardiac contractility & dysrhythmias
Tetany
Altered response to muscle relaxants
Laryngospasm risk
53
Q

Parathyroidectomy Surgical Considerations

A

Monitor cardiac dysrhythmias 2° hypercalcemia (↓refractory period ↑ventricular excitability)
NIMs ETT to monitor RLN
Neuromuscular blocking agents unpredictable consider qualitative monitoring
Careful positioning d/t fractures risk
Postop complications similar to thyroid surgery
Acute hypocalcemia

54
Q

Parathyroid Surgery

A 
Supine w/ arms tucked
Ether screen 
Neck extension 
Video to place NIMs ETT
2 PIVs
PTH sampling (saphenous vein)
NIBP cuff above sample IV to act as tourniquet
Consider A-line
Antiemetics ↓pressure
Inhalational agent
Remifentanil infusion
Consider TIVA (risk PONV)
No muscle relaxant
55
Q

PTH Sampling

A

Baseline PTH
Time 0 when parathyroid removed
Time 5/10/15 min post parathyroid removal

AS - N935 Advanced Patho II (20 decks)

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