1. Warm anaesthesia greetings
Dr. S. Parthasarathy
MD., DA., DNB,
MD (Acu), Dip. Diab.
Dip. Software statistics
PhD ( physiology), IDRA , FICA

2. THYROID AND ANAESTHESIA
Why should we know??
Patients can come to us with thyroid diseases for thyroid surgery and
Non thyroid surgery

3. THYROID AND ANAESTHESIA
Second most common endocrine disease.
Discuss under
Some physiology.
Hypothyroid for anaesthesia
Thyrotoxicosis for anaesthesia
For thyroidectomy

4. Physiology

5. Synthesis Iodide trapping Organification
tyrosine + iodine = MIT or DIT
Coupling
MIT + DIT = T3
DIT + DIT = T4
No coupling then -
Deiodinase to revert iodine back to the gland

6. Actions
So varied in all systems as visitors of marina beach

7. hypothyroidism
Neonatal hypothyroidism -> cretinism with physical and mental retardation

8. Adult manifestations weight gain, cold intolerance,
muscle fatigue, lethargy, constipation,
hypoactive reflexes, dull facial expression, depression,
decreased heart rate, contractility, stoke volume, cardiac output,

9. cool, mottled extremities (peripheral vasoconstriction),
pleural, pericardial, abdominal effusions
Almost all systems

10. Hypothyroid patients low free T4,
TSH elevated in primary hypothyroidism
Treatment
thyroid hormone administration
several days for physiologic effect
4- 6 weeks until definite clinical improvement

11. Anaesthetic Considerations Preoperative
Make euthyroid before any elective case.
Continue usual thyroid hormone
Points to note.
Slow gastric emptying
Prone to drug-induced respiratory depression

12. Susceptible to induction hypotension
If refractory hypotension, consider additional adrenal insufficiency
Ketamine may be good induction agent
prone for sedatives

13. Hypothyroid - tips
Inhalation induction faster with decreased cardiac output
No significant effect on MAC
Large tongue and problems
Associated obesity

14. Hypothyroid Other potential problems hypoglycemia anemia hyponatremia
hypothermia
Delayed emergence/recovery
respiratory depression,slowed drug biotransformation

15. Hypothyroid send lak Go for regional / local always. Less sedatives
Less narcotics.
Expect excess bleed.
Difficult airway.
Acid aspiration prophylaxis.
Ketamine better.

16. Thyrotoxicosis weight loss, heat intolerance, diarrhea,
hyperactive reflexes, nervousness, fine tremor, exophthalmos or goiter,
tachycardia, atrial fibrillation, congestive heart failure
 Muscle weakness, proximal myopathy
 Lid retraction or lag
Irregular menstrual bleed

17. elevated serum total thyroxine, triiodothyronine and/or free thyroxine
Decreased TSH

18. Medical Treatment
Inhibit hormone synthesis (propylthiouracil, methimazole)
Prevent hormone release (potassium, sodium iodine)
Mask signs of adrenergic overactivity (propranolol)
Destroy thyroid cell function (radioactive iodine)

19. Anaesthetic Considerations Preoperative
Postpone elective surgery until patient euthyroid-- Normal thyroid function studies
A low TSH value should not be a contraindication to surgery
Resting heart rate < 85
Continue antithyroid medications and beta-blockers through day of surgery

20. Intraoperative Plan local or regional Closely monitor
Cardiovascular function
Temperature
Eyes (exophthalmos of Graves' disease)
prevent sympathetic stimulation
increased inhalational anaesthetic requirement due to increased cardiac output, increased temperature
Induce and recover smooth

21. Emergency in thyrotoxic pt.
Emergency case
the use of an intravenous β-blocker, ipodate, cortisol, or dexamethasone and PTU is usually necessary control
Go for regional
Be ready for thyrotoxic crisis

22. Patients for thyroidectomy -Preoperative
History
Identify abnomality of thyroid function,
Make patients euthyroid
Associated endocrine disorders
concurrent cardiorespiratory disease.

23. Preop history
specifically enquire about dysphagia or respiratory difficulties associated with a change in posture which may indicate tracheal compression
ENT opinion
(possible ease of larynx vision) (medicolegal)

24. Clinical
Assess the airway, observe pharyngeal structures and neck mobility
Look for signs of SVC obstruction which may indicate retrosternal goitre
Spontaneous breathing – obstruction ??
Look for euthyroid status.
Sleeping pulse rate ≤ 85/min.

25. Investigations
Thyroid function tests, full blood count, sugar urea & electrolytes, serum calcium,Bl.grouping
CXR-look for evidence of tracheal compression or deviation, indirect laryngoscopy- if unsuccessful will indicate difficult intubation.
CT or MRI can be used to assess degree of retrosternal goitre.
Pulmonary function tests may demonstrate upper airway obstruction in flow-volume loops.

26. FV loop normal

27. Variable extrathoracic obstruction sitting or supine !!

28. Rt. Shift of trachea

29. ECG,Echo if necessary. sinus tachycardia prolonged PR interval ST depressions, and AF

30. premed Continue beta blockers and antithyroid drugs Sedatives adequate
Atropine , Glyco?
Fentanyl,(see HR)
Difficult airway ?? Then PPI s
Antibiotics.

31. Induction GA with controlled ventilation – ideal
Thiopentone – mild hypothyroid effects
Suxa if emergency or difficult airway.
Vec + inh. Agent
Avoid sympathetic stimulation
Pass armoured tube crossing obstruction.
nasal RAE also works well
Awake fibreoptic – rare cases.

32. monitoring Pulse, SPO2 BP, ECG, ETCo2 Temperature, NMJ monitoring
Blood loss.

33. Position supine, padding behind shoulders to extend the neck
10 to 15 * head up - some surgeons ask for.
Beware ET tube under the drapes.
Supplement with ansa cervicalis block.
Look for intraop BRADY.
Eye protection

34. Intraop hiccups?? IV access ?? Blood leakage??
Tuck in hands proper to protect.
Tight bag after intubation – is it intrathoracic thyroid

35. Recovery Smooth. Add “Just before end ” narcotics.
Possibly look for cord movements.

36. Postoperative Management: 1. Airway problems
Haematoma
lymphatic obstruction
give O2 and/or CPAP
* remove sutures & open the wound
* If intubation required for obstruction do reintubate

37. Recurrent laryngeal nerve palsy
Unilateral neuropraxia not uncommon results in voice change and slight stridor
Bilateral palsy rare:
* 1/30,000
* flaccid cords are drawn together by the Bernouli effect during inspiration
* causes complete obstruction requiring reintubation and tracheostomy

38. Tracheomalacia
the tracheal rings can become weakened by the effects of prolonged pressure due to large goitre
postoperative collapse of the trachea can cause complete obstruction
rare except in areas of endemic goitre with late presentation
Prolonged ventilation will help.

39. Tetany hypocalcaemia typically develops 24 -72 hrs postop
hypoparathyroidism can present as laryngospasm
monitor serum Ca++ & Mg++
Chvostoek's sign: facial muscle spasm on tapping of the facial nerve

40. Tetany
Trousseau's sign: carpopedal spasm within 4 mins of inflating a blood pressure cuff to >systolic BP
Mg++ promotes PTH release
Ca++ given immediately if clinically detectable hypocalcaemia

41. Post op
Removal of the thyrotoxic gland does not mean immediate resolution of thyrotoxicosis. The T1/2 of T4 is 7 to 8 days; therefore, β-blocker therapy may need to be continued in the postoperative period

42. thyroid storm intraop, but usually 6-24 hours postop hyperpyrexia,
tachycardia, hypotension
agitation,
delirium, coma,

43. Treatment A,B,C,D Antithyroid drugs,Antibiotics Beta-blockade
propylthioruacil 250 mg Q6H PO or NG followed by sodium iodide 1 Gm IV over 12 hours
Beta-blockade
esmolol infusion or propranolol 0.5 mg increments until heart rate < 100
Cooling and Cortisol mg Q8H (possible coexisting adrenal gland suppression)
Drip

44. Other options Cervical epidural
C7 -C8 space catheter 6 ml of 0.5% bupi
Superficial and deep cervical plexus block.
Local and acupuncture

45. message Make euthyroid. Smooth induction and recovery.
Plan and precisely give drugs.
Use monitors.
Beware of postop complications.