anesthesia

1. ANAESTHESIA FOR HYPOTHYROID
PATIENT
MODERATOR-Dr.RAGHURAM
PROFESSOR
DEPARTMENT OF ANAESTHESIA
PRESENTOR-Dr. S.SARAH SHAHNAZ

2. INTRODUCTION

3. THYROID GLAND
• Endocrine gland in the anterior and lateral
aspects of the neck
• Bi-lobed connected by the isthmus
• Upper border of isthmus is below the
cricoid cartilage
• Weighs about 20 grams
• Highly vascular gland-with rich capillary
permeation
• Recurrent laryngeal gland , external
laryngeal nerve are in close proximity to
the gland

5. • Innervated by adrenergic and cholinergic
nervous system
• The gland is made of follicles with
proteinaceous colloid
• Colloid has thyroglobulin-iodinated
glycoprotein-substrate for thyroid hormone
synthesis
• It bears parafollicular C cells-calcitonin
• The hypothalamo-pituitary-thyroid axis
plays an important role in body
metabolism

6. BLOOD SUPPLY OF THYROID GLAND

7. LYMPHATIC DRAINAGE

8. RELATIONAL ANATOMY

9. HYPOTHALAMO-PITUITARY-
THYROID AXIS

12. THYROID DISORDERS
• Hyperthyroidism
• Hypothyroidism
• Goitre-
single nodular
multinodular
• Thyroid tumors
follicular carcinoma
papillary carcinoma
medullary
carcinoma
anaplastic
carcinoma

13. parameter Values units
Serum TSH 0.5-5 micro units/ml
total T4 50-150 nanomol/litre
Total T3 1.5-3.5 nanomol/litre
Free T4 12-28 picomol/litre
freeT3 3-9 picomol/litre
thyroglobulin <1-35 micrograms/litre

14. HYPOTHYROIDISM

15. HYPOTHYROIDISM
• Relatively common in adult population
• Could be of two types
primary hypothyroidism
secondary hypothyroidism
euthyroid sick syndrome

17. Primary hypothyroidism
• Decreased production of thyroid hormones
inspite of adequate or increased levels of
TSH
seen most commonly
• TRH administration causes exaggerated TSH
elevation
Secondary hypothyroidism
• reduced levels of freeT4,T3,T4 and reduced
TSH level
• TRH stimulation confirms pituitary as cause
which shows absent or blunted reflex

18. Euthyroid sick syndrome
abnormal thyroid function tests in critically
ill patients with significant non thyroid illness
• Low level of T3 T4 and normal TSH level
• With deterioration of the disease,T3 and T4
level decreases further
• Stress induced as a physiological response
during surgery
• No treatment is needed
• Serum TSH
> 10milliunits/L implies hypothyroidism
<5 milliunits/L implies euthyroidism

19. ETIOLOGY
• Surgery-most common cause
• Radioactive iodine ablation
• Idiopathic
• Autoimmune

22. FEATURES OF HYPOTHYROIDISM
• Apathy
• Arthralgia
• Cardiac failure
• cardiomegaly
• Carpal tunnel syndrome
• Constipation
• Decreased sweating

23. • Deep hoarse voice
• Dry skin
• Intolerance to cold
• Impaired free water clearance-hyponatremia
• Lethargy
• Menorrhagia
• Non pitting edema
• Pleural and pericardial effusion
• Periorbital edema

24. • Sleep apnea
• Slow gastric emptying
• Slow mental functions
• Slow movement
• Weight gain –coarse facial features
-large tongue

28. TREATMENT
• Levothyroxine sodium commonly used
• Response to therapy
sodium and water diuresis
reduction in TSH level
• Patient with cardiomyopathy shows
measurable improvement in myocardial
function with therapy
• Angina if already present may worsen hence
angiogram is needed before hormone
replacement

29. HYPOTHYROIDISM AND
ANESTHESIA

30. HYPOTHYROIDISM AND ANAESTHSIA
• Mild to moderate thyroid dysfunction has
minimal impact peri-operatively
• Features expressed in hypothyroid state
directs the precautions to be taken peri-
operatively and intra-operatively
• Hypothyroidism reduces anaesthetic
requirement slightly
• Determination of medical treatment is
important

31. • Changes in thyroid function have been
documented in uncomplicated acute
myocardial infarction, congestive heart
failure, cardiopulmonary bypass.
• Significant T3 depression occurs which
may not get corrected with T3
administration
• Patient taking amiodarone are at risk of
hypothyroidism and needs a thyroid
function test before surgery

32. PREOPERATIVE PERIOD
• Euthyroid state is ideal for surgical
procedures
• For chronic thyroid disorder a preoperative
thyroid function test is needed
• Reliable report - if it is less than 6 months
• Thyroid stimulating hormone (TSH) is the
best to evaluate hypothyroidism
• Surgical stress may precipitate myxedema
or thyroid storm in untreated or severe
cases

33. • Elective surgeries must be postponed until
the patient is euthyroid
• Emergency surgeries must be done after
consultation with endocrinologist
• Chest x-ray or CT is used to rule out
tracheal or mediastinal involvement
• Continuation of drug on the day of surgery
is important

34. • In patients with no history of prior thyroid
dysfunction but with present history its
symptoms-TSH alone could be done
• Full replacement dose of levothyroxine-
1.6micrograms/kg/day
-elderly or those with coronary artery
disease the initial dose -25 µg daily
-increase every 2 to 6 weeks until
euthyroid state
• Half life of the drug is 7 days

35. INTRA-OPERATIVE PERIOD
• Increased risk when hypothyroid patient
goes through general or regional
anaesthesia
• Difficult intubation-Swollen oral cavity
-edematous vocal cords
-goitrous enlargement
• Aspiration risk and regurgitation risk-
decreased gastric emptying

36. Cardiovascular changes
• hypodynamic circulation
• Decreased cardiac output
• Decreased stroke volume
• Decreased heart rate
• Decreased baroreceptor reflexes
Respiratory changes
• Enhanced suppression of ventilatory
response to hypoxia and hypercarbia

37. Hematologic abnormalities
• Anemia 25%-50% of patients
• Platelet dysfunction and coagulation factor
abnormalities (factor viii)
• electrolyte imbalances-hyponatremia
Metabolic demands
• Hypoglycemia is common
• Hypothermia has quicker onset which is
difficult to treat
• decreased neuromuscular excitability

38. PRECAUTIONS
• Extremely sensitive to narcotics and
sedatives
-cautious pre operative sedation is needed
• Hypothyroidism effects on Minimum
Alveolar concentration is negligible
• Due to decreased hepatic metabolism and
renal excretion of drugs- induction agents
and neuromuscular blockers must be used
with caution

39. • Due to cardiovascular instability the
patient may need invasive monitoring and
transesophageal echocardiography
• In noncardiac surgery-intraoperative
hypotension occurs
• In cardiac surgery,heart failure was more
prevalent

40. GENERAL ANESTHESIA
• given through oral endotracheal tube
• Rapid sequence induction or awake
intubation done in case of difficult airway
• Inhalational agents may aggravate
myocardial depression
• Pancuronium is the ideal neuromuscular
blocker from cardiovascular standpoint but
careful dosing is needed due to reduced
skeletal muscle activity and reduced
hepatic metabolism

41. • Controlled ventilation needed as
spontaneous breathing may lead to
hypoventilation
• Intraoperative hypotension is managed by
pharmacological agents like
ephedrine,dopamine,epinephrine if
unresponsive may need supplemental
steroid administration
• Dextrose in normal saline is preferred to
avoid hypoglycemia and hyponatremia

42. POST OPERATIVE PERIOD
• Myxedema coma common in emergency
cases
• Intravenous thyroid replacement therapy
should be started
• intravenous L thyroxine takes 10 to12days
to yield peak basal metabolic rate
• Intravenous tri-iodothyronine effective in 6
hours with peak metabolic rate seen in 36
hours to 72 hours

43. • Levo thyroxine 300 to 500 mcg I.V or Levo tri-
iodothyronine 25 to 50 mcg I.V is the initial
dose
• Hypothyroidism may be associated with
decreased adrenal cortical function,steroid
coverage with hydrocortisone or
dexamethazone could be given
• Milrinone phosphodiesterase inhibitor may be
effective in the treatment of intraoperative
myocardial depression

44. • Post operatively ,if still no ability to administer
the drug enterally after 5 days, intravenous
(IV) levo thyroxine should be administered as
60% to 80% of the oral dose
• the hypothyroid group has a higher rate of
gastrointestinal and neuropsychiatric
complications post surgically

45. MYXEDEMA COMA
• Is a rare severe form of decompensated
hypothyroidism
• Mostly seen in elderly women with chronic
hypothyroidism
• Infection, trauma,cold and central nervous
system depressant predispose
hypothyroidism to myxedema coma
• Patient is not comatose but often needs
mechanical ventilation

46. • Hypothermia of less than 27 degree
centigrade is a cardinal feature with
impaired thermoregulation by
hypothyroidism
• Treatment of choice
Intravenous L-thyroxine or L-triiodothyronine
• Intravenous fluid-glucose containing saline
solution
• Thermoregulation
• Electrolyte imbalance correction

47. • Stabilization of cardiac and pulmonary
function
• Vitals-heart rate ,blood
pressure,temprature improve 24 hours
• Relative euthyroid is achieved in 3 to 5
days
• Hydrocortisone 100-300mcg/day is given
for adrenal insuffiency

48. • management in the intensive care unit
where proper ventilatory, electrolyte, and
hemodynamic support can be given.
• Passive rewarming, broad spectrum
antibiotic coverage and corticosteroids
may be needed.
• The definitive treatment is thyroid hormone
replacement administered as IV T4, 200 to
500 mcg as an initial bolus followed by 50-
100 mcg daily

49. • Few suggest addition of IV T3, 10-25 mcg
every 8 hours if available.
• Rapid thyroid hormone replacement may
precipitate myocardial infarction, hence
caution should be exercised in those with
underlying ischemic heart disease.
• Treatment of the precipitating cause like
an infection is critical for rapid recovery.

51. PREGNANCY AND HYPOTHYROIDISM

52. • Pregnancy is a state of excessive thyroid
stimulation
• increase in thyroid size by 10% in iodide
sufficient areas and 20-40% in iodide deficient
regions
• Due to physiological and hormonal changes
caused by pregnancy and human chorionic
gonadotropin (HCG) the production of
thyroxin (T4) and triiodothyronine (T3)
increase up to 50%

53. • 50% increase in daily iodide need, while
Thyroid-stimulating hormone (TSH) levels
are decreased in first trimester
• In an iodide sufficient area ,thyroid
adaptations during pregnancy are
tolerated, as stored inner iodide is
sufficient
• in iodide deficient areas, due to
physiological adaptations there are
significant changes during pregnancy

54. FEATURES
OVERT HYPOTHYROIDISM
• Abortion
• Anemia
• pregnancy-induced hypertension
• Preeclampsia
• premature birth
• low birth weight
• intrauterine fetal death

55. • increased neonatal respiratory distress
and
• infant neuro-developmental dysfunction
• placental abruption
• postpartum hemorrhage
SUBCLINICAL HYPOTHYROIDISM
• higher chance of placental abruption
• preterm birth
• miscarriage
• gestational hypertension
• fetal distress

56. • severe preeclampsia
• neonatal distress
• diabetes in pregnant women
• thyroid autoimmunity has effects similar to
that of subclinical hypothyroidism
• Subclinical hypothyroidism is the most
common thyroid dysfunction during
pregnancy

57. • hypothyroidism is very common during
pregnancy
• 2-3% of pregnant women suffer from
hypothyroidism
• 0.3-0.5% overt hypothyroidism and 2-2.5%
subclinical hypothyroidism
• main etiology for hypothyroidism in
pregnancy is iodide insufficiency
• in iodide sufficient areas, its main cause is
autoimmune thyroiditis

58. LABOUR COMPLICATION
• Labor – diskinetic,longer due to the
existence of the hypomyotonia and the
simultaneous cardio-respiratory problems;
hypokinesis
• Post-partum hemorrhages occur through
uterus hypotony and through coagulation
disorders
• Post-partum depression, post-partum
thyroiditis, hypogalactia

59. • Vitiated pelvis (limit pelvis) which can be
the reason of various cephalic-pelvis
disproportions
• Thyroid function test in pregnancy includes
free T3 and T4
• The free T4 index (FT4I) is an indirect
measure of FT4 and accounts for increase
in TBG.
• FT4I= TT4 ×RT3U
• The reported reference value for FT4I is
4.5-12.5mcg/dl.

60. • The values associated with hypothyroidism
increase in TSH
low FT4
low FT4I and
• variable presence of thyroperoxidase
antibodies (TPO)
• TSH and FT4/FT3 are used to assess and
follow thyroid diseases in pregnancy.
• limit of TSH should be
0.1 mIU/L -2.5 mIU/L in 1st trimester and
0.2 mIU/L -3mIU/L in 2nd and 3rd trimesters

61. • If the serum TSH is ≥3 mIU/L, tests are
repeated along with FT4 and TPO.
• Start levothyroxine meanwhile
• If declared euthyroid stop levothyroxine
• If TSH is >3mIU/L and FT4 is normal, then
patient should be tested throughout the
pregnancy
• If TSH >3mIU/L along with low FT4, then
levothyroxin is continued and the dose is
titrated to maintain TSH level in the range
of 0.5-2.5 mIU/ L

63. MEDICAL MANAGEMENT
• pre-existing hypothyroidism, there is 30-
50% increase in requirement of
levothyroxine during the first trimester.
• due to increased T4 metabolism, elevated
TBG as well as inhibition of thyroid
hormone (TH) absorption from the gut by
prenatal iron supplements.
• Could be treated by iron supplements and
TH four hours apart.

64. • hypothyroidism during pregnancy,
levothyroxine should be started at a dose
of 1-2 mcg/kg/day
• TSH levels should be reassessed 4-6
weeks following the dose change
• Treatment goal of TSH in the range of 0.5-
2.5 mIU/L.
• overt hypothyroidism diagnosed in
pregnancy, T4 should be normalised as
rapidly as possible by using two to three
times the estimated final daily dose.

65. ANESTHETIC MANAGEMENT
• During pre operative preparation, anxiolytics
and sedatives should be avoided
• administration of antihistamines like
ranitidine and oral sodium citrate solution
along with metoclopramide are considered
safe.
• Severe hypothyroidism should be managed
with IV T3/T4

66. • Hypothermia should be prevented in the
operation room as well as in the post
operative period
• hypothyroidism is associated with
qualitative platelet dysfunction-
dysfunction-arrangement of fresh frozen
plasma or platelets is needed
• epidural hematoma is a risk and presence
of normal coagulation should be confirmed
before regional anesthesia

67. • Vasopressor response is normal for
epinephrine but, decreased for
phenylephrine.
• During surgical stress, hydrocortisone
should be given
• Regional anesthesia should be favoured
over general anesthesia
• Nerve stimulators may not be useful
clinically due to abnormal response to the
peripheral nerve stimulator, due to
depression of neuromuscular junction
activities

68. REFERENCES
• Miller’s ANESTHESIA-volume1-eighth edition
• Stoelting’s anesthesia and co-existing disease-
second south asian edition
• MAEdiCA-a journal of clinical medicine-2010-
Maternal and fetal complications of the
hypothyroidism-related pregnancy
• Iran J Reprod Med-review article-2015-Thyroid
dysfunction and pregnancy outcomes
• Schwartz’s principles of surgery-10th edition
• https://www.apicareonline.com/thyroid-
disorders-during-pregnancy-and-anesthetic-
considerations/