Case 27 - thyroidectomy Flashcards

1
Q

how is thyroid hormone produced?

A
  • hypothalamus –> produces thyrotropin releasing horomone –> ant pit
  • Ant Pit –> secretes TSH
  • TSH binds to receptors of thyroid to produce T3 and T4
  • T3 is active form
  • TSH levels good screening tools for thyroid function
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2
Q

what is the classic presentation of thyrotoxicosis?

A
  • thyroid hormone affect metabolic function –> facilitate biochem reactions that increase heat production and O2 consumption
  • upregulates beta receptors and enhance catecholamine effects

Thyroidtoxicosis s/sx

  • nervousness/anxiety
  • weight loss
  • tremor
  • a-fib
  • CHF
  • MI
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3
Q

How does thyroid storm differ from thyrotoxicosis?

A
  • thyroid storm is a state of decompensation from thyrotoxicosis (more severe).
  • precipitated by stress (MI, surgery, trauma, DKA)

s/sx

  • high grade fever
  • severe tachy / a fib
  • CHF
  • HTN
  • agitation / altered mental status
  • hypovolemic hypotension (fluid losses from n/v, diarrhea, profuse sweating)
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4
Q

Are there any other similar presentations to thyroid storm?

A

DDx

  • MH
  • neuroletpic malignant syndrome
  • sepsis
  • pheochromocytoma
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5
Q

What is the tx of thyroid storm?

A

Four principles: 1) block thyroid hormone production and secretion, 2) stop conversion of T4 to T3, 3) antagonize beta adrenergic effects, 4) supportive measures.

1) block thyroid hormone production and secretion:

  • propylthiouracil (PTU)
  • Methimazole
  • Iodine (blocks secretion)
    • see an inital increase in prouction and exacerbates thyroid storm

2) Block T4 to T3 conversion
* Hydrocortisone
3) Beta adrenergic effects

  • esmolol
  • propranolol
  • diltiazem

4) supportive measures

  • fluids, cooling –> hypotension
  • demerol –> shivering
  • Tylenol –> fever
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6
Q

Patient has thyroid cancer and comes for surgery. What are your pre-operative concerns?

A

1) Airway

  • examine airway
  • listen for dysphonia (vocal cord involvement)
  • imaging studies for tracheal deviation or tracheal compression

2) retrosternal goiter?

  • large size can cause SVC syndrome –> facial swelling, JVD
  • can compress nearby artery –> cerebreal hypoperfusion

3) is it a medullary carcinoma / concern for MEN
* medullary carncioma often coexist with pheochromocytoma (MEN 2a and 2b)
4) patient optimized medically? Euthyroid?

  • beta blockers
  • iodine and antithyroid meds
  • Emerget surgery –> start beta blocker and antithyroid meds intra-op (do not delay sx)
  • dehydrated from sweating, diarrhea, n/v –> give fluids and pressors
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7
Q

What are complications of thyroid surgery?

A

most severe complication is respiratory distress.

Resp distress

  • recurrent layrngeal nerve injury
    • **​b/l injury - **vocal cords 2-3 mm from midline (unopposed adduction from sup lary n)
    • unilateral -> hoarseness
  • Hypocalcemia
    • hypoparathyroidism
    • Chvostek (facial spasm); trousseau (carpal spasm)
    • assoc with larygneal muscle tetany
    • effects seen 24-72 hrs after surgery
  • Tracheal compression
    • hematoma
  • tracheomalacia
  • phrenic N injury
    • hemidiaphragmatic paralysis

Other complications: hypothyroid, thyroid storm

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8
Q

What are some anesthetic considerations for thyroid surgery?

A

1) airway
* trachea compression, hoaressness
2) HD status
* hypovolemic (fever, htn, diarrhea) –> fluids and pressors
3) acute thyoid crisis during induction

  • similar s/sx to MH = increase HR, BP, EtCO2
  • MH assoc with muscle rigidity and inc CPK (not seen in acute thyroid crisis)

4) muscle relaxants vs high dose opioids
* remifentanil gtt if intraop nerve monitoring
5) avoid HTN and tachycardia
6) careful eye protection (Grave disease pts); proptosis
7) smooth emergence
* avoid coughing/bucking due to increase risk of hematoma and resp distress
8) post-op resp monitor
* variety of resp distresscomplications assoc with surgery

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9
Q

how do you perform a cervical plexus block for thyroid sx

A

Superficial cervical plexus

  • provide sensory innervation (C1 to C4)
  • main nerves: supraclavicular N (side of neck and upper chest) & transverse cervical N (neck)
  • field block post border of SCM at mid point of muscle body. inject cephalad and caudad along post border of SCM.

Deep cervical plexus

  • provides muscle innervation (C1 to C4)
  • just above ant surface of C4 TP
  • 10 cc injected, shuould spread along paravertebral space
  • risks: phrenic nerve block, vertebral A injection, epidural or spinal, horner syndrome, recurrently laryng n injury
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10
Q
A
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