Anesthesia for Endocrine Surgery Flashcards
The thyroid gland is formed by two lateral lobes connected by the _________ at about the second tracheal ring
Thyroid Isthmus
Thyroid Isthmus is ANTERIOR to the trachea
What sensory nerves innervate above the vocal cords?
Internal Laryngeal Branch of Superior Laryngeal Nerve
What sensory nerves innervate below the vocal cords?
Recurrent Laryngeal Nerve
Motor innervation to most of the intrinsic muscles of the larynx is supplied by which nerve?
This nerve does not innervate which structure of the larynx?
- Recurrent Laryngeal Nerve
- Cricothyroid Muscle
What nerve supplies motor innervation to the cricothyroid muscle?
External Laryngeal Branch of Superior Laryngeal Nerve
Colloid-filled follicles store what substance?
Thyroglobulin
Parafollicular cells produce what substance?
Calcitonin
What mineral fuels the production of thyroid hormones?
Iodine
What are the peripheral effects of Thyroid Hormone?
- Heat generation
- Stimulates ATP formation
- Influences flux of ions
- Stimulates metabolic processes ( Basal metabolic rate, protein synthesis, regulation macro metabolism)
What are the cardiac effects of Thyroid Hormone?
- ↑ LV contractility
- ↑ LV EF
- Tachycardia
- ↑ SBP and ↓ DBP
- Chronic hyperthyroidism can lead to Heart Failure, AF, Dysrhythmias
Parasympathetic innervation of the thyroid comes from which nerve?
Vagus Nerve
Sympathetic innervation of the thyroid comes from which nerve?
Superior, Middle, and Inferior Ganglia of the Sympathetic Trunk
Sympathetic nerve fibers will run through the thyroid via what plexus?
- Cardiac periarterial plexus
- Superior and inferior thyroid plexus
What hormone regulates thyroid gland secretion?
Where does this hormone come from?
- TSH
- Anterior Pituitary Gland
What are the three sources of blood supply to the thyroid gland?
- Superior thyroid artery (branch of ext carotid)
- Inferior thyroid artery (branch of subclavian)
- Thyroid ima
Venous drainage location of the thyroid gland.
- Superior thyroid vein (IJ)
- Middle thyroid vein (IJ)
- Inferior thyroid vein (brachiocephalic)
What is the normal level of TSH?
0.4-5.0 milliunits/L
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Hyperthyroidism
T4:
T3:
TSH:
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Hyperthyroidism
T4: Elevated
T3: Elevated
TSH: Normal/Low
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Primary Hypothyroidism
T4:
T3:
TSH:
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Primary Hypothyroidism
T4: Decrease
T3: Decrease/Normal
TSH: Increase
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Secondary Hypothyroidism
T4:
T3:
TSH:
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Secondary Hypothyroidism
T4: Decreased
T3: Decreased
TSH: Decreased
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Pregnancy
T4:
T3:
TSH:
Give the anticipated lab values for the following thyroid disease/condition.
Dx: Pregnancy
T4: Elevated
T3: Normal
TSH: Normal
What type of cancer has the fastest rising incidence?
Thyroid cancer
What factors determine the prognosis of thyroid cancer?
- Age of patient
- Sex
- Presence of metastases
- Tumor size
- Local invasion
What is the mainstay of thyroid cancer?
Surgical Treatment
Surgical options for thyroid cancer
- Lobectomy
- Total thyroidectomy
- Total thyroidectomy plus lymph node dissection
What are the risks of thyroid surgery?
- RLN injury (biggest risk)
- Hypoparathyroidism (mostly temporary)
- Bleeding
Unilateral RLN - hoarseness, global sensation, temporary
Bilateral RLN - AIRWAY issue
A syndrome caused by excessive secretion of TH when there is an overactive thyroid gland.
HYPERTHYROIDISM
Clinical Manifestation of Hyperthyroidism
Thyrotoxicosis
Cause of Hyperthyroidism
- Graves disease (most common)
- Thyroid adenoma
- Thyroid carcinoma
- TSH pituitary adenomas
- Iatrogenic
Symptoms of Hyperthyroidism
- Tachycardia/ Palpitations
- Nervousness
- Heat intolerance/ ↑ Sweating
- Fatigue and weakness
- ↑ Metabolism/ Weight loss
- Hyperdefication
Signs of Hyperthyroidism
- Thyroid enlargement
- Tachycardia
- Atrial fibrillation
- Systolic hypertension ( wide pulse pressure)
- Eye signs (exophthalmos)
Which gender is more prone to hyperthyroidism?
Female (age 20-40)
Possible treatments for hyperthyroidism
- Anti-thyroid Drugs
- β-blockers
- Steroid/ Glucocorticoids
- Radiation
- Surgery
Normal T4 level
60-120 nmole/L
Factors that increase T4 level
- Hyperthyroidism
- Thyroditis
- Early hepatitis
- Pregnancy
- Oestrogen therapy
- Exogenous T4
Factors that decrease T4 level
- Hypothyroidism
- Androgens
- Salicylates
- Sulphonamides
Normal T3 level
0.92-3 nmole/L
Factors that increase T3 level
Hyperthyroidism
Factors that decrease T3 level
- Hypothyroidism
- Cirrhosis
- Uremia
- Malnutrition
What condition will increase TSH level?
Primary Hypothyroidism
What condition will decrease TSH level?
Hyperthyroidism
Give examples of Anti-thyroid drugs.
MOA.
- PTU
- Methimazole
- Carbimazole
- MOA: Inhibition of synthesis of TH by blocking the action of peroxidase, also inhibits the T4 → T3 conversion
MOA of how glucocorticoids treat hyperthyroidism
- Decreases Release of hormone
- Inhibits conversion T4 → T3
MOA of how radioactive iodine treats hyperthyroidism
- Destroys follicular cells
- Remission Rate: 80% +
- 40% - 70% hypothyroid within ten years
What is the last resort for hyperthyroidism treatment?
- SURGERY
- Remission 95%
- 10% - 30% hypothyroid w/i 20 yrs
Indications for Thyroid Surgery
- Large goiter
- Compressive symptoms
- Kids
- CA pt or suspicious nodules
- Allergy to anti-thyroid drugs
- Pregnant and those with a desire to conceive soon
- Moderate to severe ophthalmopathy
- Cosmetic desire of the patient
Pre-op assessment for patients undergoing thyroid surgery
- Assessment of upper airway & tracheal deviation
- Thoracic inlet X-ray, CT scan
- Patient must be EUTHYROID
- Use anti-thyroid drugs and β-blockers
- Resting pulse rate 85-90 bpm
What drugs should you avoid during thyroid surgery?
- Atropine
- Pancuronium
- Halothane
- Ketamine
These drugs may activate the SNS
Drug of choice for induction of a hyperthyroid patient.
- Etomidate
- Propofol
- Barbituates
Choice of muscle relaxant for hyperthyroidism
- Atracurium
- Vecuronium
Cardio stability
Choice of VA for hyperthyroid patient
Isoflurane
Cardio Protective
What type of infusion will typically be started on thyroid patients to keep HR in check?
Esmolol infusion 50-150 mcg/kg/min
What is a postoperative concern for thyroid surgery patients?
Thyroid storm/ crisis
An acute exacerbation of hyperthyroidism with excessive release of thyroid hormone
When will the patient experience a thyroid storm/ crisis?
Onset can be intraoperative or 6-24 hours after surgery
Signs and Sx of Thyroid Storm
- Hyperpyrexia,
- Tachycardia or atrial fibrillation
- Hypotension
- Vomiting/ Dehydration,
- Tachypnea
- Acute abdominal pain
- Agitation/ psychosis
Need to R/O: MH, Pheochromocytoma, or Light Anesthesia