2. THYROID ANATOMY
LOCATION: Lower part of the
front and side of the neck
opposite to the c5,c6,c7 and
T1 vertebrae, clasping the
upper part of the trachea
Boundaries
Superiorly: thyroid cartilage
Inferiorly: 4th or 5th tracheal ring
Anteriorly: Inferior hyoid
Ligaments
Posteriorly: cricoid and tracheal
cartilage
3. BLOOD AND NERVOUS SUPPLY
Blood Supply: Superior and Inferior thyroid artery.
Sympathetic: Superior cervical ganglion and cervicothoracic
ganglion.
Parasympathetic: Superior and recurrent laryngeal nerve
4. PHYSIOLOGY- THYROID HORMONE
SYNTHESIS
1. IODINE TRAP:
Dietary iodine is reduced to iodide in the Gastro Intestinal tract
It is absorbed into the thyroid gland against the concentration
gradient of 1:5
In thyrotoxicosis, the concentration gradient can be as high as 1:20
2. OXIDATION AND ORGANIFICATION:
Iodine is oxidized to iodide and is bound to tyrosine to form
monoiodo and di iodo tyrosines by thyroid peroxidase
5. 3. COUPLING:
Mono iodo tyrosine and di iodo tyrosine coupled enzymatically by
thyroid peroxidase to form either T3 or T4
4. STORAGE:
T3 and T4 are stored after attaching to thyroglobulin protein as colloid
in the gland
5. RELEASE AND RECYCLING:
The release of T3 and T4 through proteolysis from thyroglobulin and
diffusion into the circulation.
The remaining mono iodo and di iodo tyrosines are recycled for
formation of T3 and T4.
6.
7.
8. THYROID HORMONES
T4: Daily T4 released: 80 to 100mcg/kg
Half life: 7 days
Highly protein bound
T3: 20% secreted by thyroid gland and 80% by extra thyroidal conversion from T4
biologically active
Half life: 24 to 30 hours
• Control of T3 &T4Secretion
• Low blood levels ofhormones stimulate hypothalamus ->TRH
• It stimulates pituitary torelease TSH
• TSH stimulates gland toraise blood levels
• T3 and T4 regulatethemselves through a negative feedback loop
9. System Effects
Cardiovascular Increases heart rate
Increases the force of cardiac contractions
Increases cardiac output as a result of the previous two effects
Promotes peripheral vasodilation
Central nervous Essential for normal brain development,such as cerebellar growth and nerve myelination
Necessary for normal intellectual development in infants
Necessary for emotional stability in adults
Gastrointestinal Increases appetite
Increases secretion of 'digestive juices'
Increases gastric mouity
Hematopoietic Influences erythropoiesis
10. System Effects
Metabolic Profoundly affects oxidative metabolism
Increases oxygen consumption in all tissues except the brain,gonads,and spleen
Promotes heat production
Influences synthesis and degradation of carbohydrate,fat,and protein
Respiratory Influences lung development
Necessary for surfactant production
ncreases rate and depth of respirations
Skeletal Indirectly promotes growth formation by actions on the pituitary gland
Acts synergistically with growth hormone and other growth factors that promote bone
formation
Directly affects skeletal maturation
Necessary for progression of tooth development and eruption
Skin Necessary for growth and maturation of the epidermis and hair follicles
11.
12. HYPERTHYROIDISM
• Hyper functioning of the thyroid gland with excessive secretion of active
thyroid hormones
• Thyrotoxicosis is its clinical manifestation when the body tissue is
excessively stimulated by increased Thyroid hormones
14. PATHOPHYSIOLOGY
• Increase GI motility, O2 consumption, BMR and heat production.
• Increased metabolism leads to :-
- Negative nitrogen balance.
- Lipid depletion.
- Nutritional deficiency.
- Increased O2 consumption
• Increase bone and protein turnover, glycogenolysis, hepatic
gluconeogenesis, intestinal glucose absorption, cholesterol synthesis
and degradation
15. • Thyroid Hormones results in positive inotropic and chromotropic
effect by increasing calcium- ATPase and β-adrenergic receptors
amount and sensitivity. This results:-
- Tachycardia
- Increased Cardiac Output and stroke volume.
- Increased adrenergic responsiveness.
- Increased peripheral vasodilation and blood flow.
• High BMR → raises body Temperature→ peripheral vessel dilatation
→ forces the CO to increase → may lead to high output failure.
16. CLINICAL FEATURES:
• Symptoms: hyperactivity, weight loss and tremor, palpitation,
anxiety/nervousness, diarrhea, intolerance to heat, large muscle group
weakness, menstrual abnormalities.
• Signs: tachycardia ( ↑ sleeping PR), warm moist skin, irregularly
irregular pulse, fine brittle hair, ↑ Cardiac Output, Ischemic Heart
Disease, Heart Failure .
• Eye signs: 1. Eyelid retraction.
2. Lid lag sign.
3. Joffroy sign-absence of wrinkling.
4. Mobius sign-difficulty in convergence.
5. Stellwag’s sign-absence of blinking(staring).
17. TREATMENT
• Antithyroid drugs: methimazole or proylthiouracil ( PTU) interfere with thyroid
hormone synthesis. PTU also inhibits the peripheral conversion of T4 to T3.
Carbimazole: 15-40mg daily till euthyroid & then 5-15mg
PTU:200-400mg daily till euthyroid & then 50-150mg
Methimazole:15-60mg divided every 12hrs.
Although blockage of hormones synthesis is rapid, clinical improvement occurs
after few weeks or months ,because a large pool of stored hormone continues to
be released from thyroid.
S/E: agranulocytosis, hepatotoxicity, vasculitis, teratogenicity.
• Iodide: Inhibit hormone release. Effects occur immediately but short –lived.
Reserved for hyperthyroid patients for surgery, thyroid storm.
Potassium iodide- 3 drops PO every 8 hrly for 10-14 days.
18. • beta adrenergic antagonists: relieve signs and symptoms of
increased adrenergic activity. Propanolol has the added feature-inhibit
conversion of T4 to T3.
Propranolol 40mg BID or nadolol 160mg once daily; higher dose
may be needed
Nadolol and atenolol have a longer duration than propranolol.
In emergency, pts. can be prepared for surgery in less than 1 hour by
IV administration of esmolol. resting heart rate should be <85-90bpm.
• radioactive iodine and subtotal thyroidectomy: other alternative to
medical therapy.
19. ANESTHESIA MANAGEMENT
Preoperative Assessment
• History (hyper/hypo/euthyroidism features, adverse respiratory and CVS effect due to
compression and hormone)
• Examination(size, type, retrosternal extension of mass/positive Pemberton's sign and
systemic effect of thyroid hormone)
• Investigations including:
Complete Blood Counts
Thyroid Function Tests
Antroposterior or lateral CXR to see retrosternal extension
lateral neck x-ray to see tracheal compression
CT scan
Respiratory function tests
2D ECHO
20. PREOPERATIVE PREPARATION
• If elective, patient needs to be rendered euthyroid with drugs
• β-blocking drugs- to abolish the clinical manifestation of the toxic state.
• It has very rapid control , operation is possible within a week or two weeks.
• Glucocorticoids –reduce TH release and peripheral conversion of T4→T3
• Iodides started 10-14 days before surgery and proceed until the day
• Lugol’s iodine (for 10 days, 3-5 drops BID) to decrease the vascularity of the
gland.
• Benzodiazepine the night before the day of surgery.
• Continue antithyroid and B-blockers until the morning of surgery.
21. INTRAOPERATIVE MANAGEMENT
• Allow safe induction and awakening with adequate pain management.
• Maintain adequate levels of anaesthesia ( avoid exaggerated
sympathetic response to surgical stimulus).
• Barbiturates have antithyroid activity at high doses and is best for
induction
• For treatment of hypotension decreased doses of direct-acting
vasopressors such as phenylephrine may be a better choice than
ephedrine, which acts in part by provoking the release of
catecholamine.
• Avoid:
- Atropine
- Pancuronium
- Halothane
22. • If hyperthyroid patient with clinically apparent disease requires
emergency surgery :
- Propranolol 0.5mg IV is given ( may be increased ).
- Esmolol (alternative) as a continuous infusion 50-500mic/kg/min.
- Maintain heart rate below 90bpm.
• Use dexametasone 8mg/ hydrocortisone 100 mg to reduce incidence of
airway edema.
23. • Regional anesthesia(SA,EA) may be technique of choice in
hyperthyroid case for non thyroid surgery without presence of CHF.
• Continuous epidural may be preferable to spinal because of the
slower onset of sympathetic nervous system blockade
• Epinephrine should not be added to local anesthetics, as systemic
absorption of this catecholamine could produce exaggerated
circulatory responses
• Monitor ECG and patient’s body temperature (for thyroid storm)
24. COMPLICATIONS
1. Thyroid Storm :
Acute life threatening exacerbation of
hyperthyroidism. Happens intaoperatively or
postoperatively with in 24hr
Manifestations:
• Hyperthermia (>40oC)
• Tachycardia
• CHF
• Agitation
• Confusion
• Dysrhythmias, AF or VT
• Severe hypertension
Differential Diagnosis : -
Malignant hyperthermia
Pheochromcytoma
Light anesthesia
25. Treatment of thyroid storm
• PTU 200-400mg PO or via NGT Q6hr.
• paracetamal and cold blanket
• IV fluids
• B-blocker; propranolol 10-40mg PO Q4-6hr /esmolol infusion until
HR<100bpm.
• Steroids- hydrocortisone =50-100mg IV -Q6hr
• Digoxin for uncontrolled atrial fibrillation and heart failure
• Iodide therapy-decrease iodine uptake and thyroid hormone secretion
250mg PO Or IV Q6hr.
• O2 and hemodynamic support
26. 2. Recurrent Laryngeal Nerve (RLN) injury :
-Manifestations of RLN injury:
Unilateral
• Asymptomatic unless laryngoscopy done
Bilateral
• Usually manifests immediately after extubation.
• Laryngeal stridor, acute respiratory distress, vocal cord palsy/adduction,
phonation lost.
Treatment:
• Could be temporary or permanent
• Re-intubation, paralyzed.
• Hydrocortisone 100mg tid.
• Wound re-exploration for reversible cause.
• If Can not maintain airway do tracheostomy
27. 3. airway obstruction
• Vocal cords can collapse together, producing total airway obstruction
during inspiration due to RLN paralysis
• If occurs soon after tracheal extubation, despite normal vocal cord
function, suggests tracheomalacia
• This reflects a weakening of tracheal rings by chronic pressure of a
goiter
• Airway obstruction postoperatively may be due to tracheal
compression by a hematoma
• Treatment will be reintubation. If not possible maintain AirWay with
tracheostomy.
28. 4. Hypothyroidism:
Management: TFT on regular bases.
• -Thyroxine- 50-200μgm|d.
• -10% Cagluconate PO| IV
5 .Hypoparathyroidism & hypocalcaemia:
May be due to:
• Trauma to the parathyroid gland,
• Devascularization of parathyroid or removal of the gland.
• If damage to parathyroid does occur, hypocalcaemia typically
develops 24 to 72 hours postop, but may manifest as early as 1-3
hours postop
• Laryngeal muscles are sensitive to hypocalcaemia. may go from
inspiratory stridor progressing to laryngospasm. Prompt IV calcium till
29. Diagnosis:
• Initially asymptomatic
• Carpopedal spasm (spasmodic contraction of the muscles of
the hands and feet)
• Trousseau’s (carpopedal spasm precipitated by cuff inflation)
• Chvostek’s sign (spasm of the facial muscles by tapping the facial
nerve just below the zygomatic bone)
• Circumoral paresthesia
• Mental status changes
• Seizure
• QT prolongation or cardiac arrest.
• TX:- IV calcium
30. HYPOTHYROIDISM
• Hypothyroidism is a condition when the body tissues are exposed to decreased
circulating concentration of thyroid hormones .
• Causes of Hypothyroidism
• Primary hypothyroidism
• Autoimmune
• Irradiation to the neck
• Previous131 I therapy
• Surgical removal
• Thyroiditis(Hashimoto disease)
• Severe iodine depletion
• Medications (iodines,propylthiouracil,methimazole)
• Hereditarydefects in biosynthesis
• Congenital defects in gland development
• Secondary or tertiary
hypothyroidism
• Pituitary
• Hypothalamic
31. SYMPTOMS
• Tiredness, weakness
• Dry skin
• Cold intolerance
• Hair loss
• Difficulty concentrating, poor memory
• Constipation
• Weight gain with poor appetite
• Dyspnea and hoarse voice
• Menorrhagia
• Impaired hearing
SIGNS
Dry coarse skin; cool peripheral
extremities
Puffy face, hands, and feet
(myxoedema)
Diffuse alopecia
Bradycardia
Carpal tunnel syndrome
Serious cavity effusions
Myocardial ischemia or dysrhythmia
Decreased function of respiratory
center.
Decreased cortisol production,
inappropriate production of ADH
Hyponatrmeia and Peripheral
edema
Elevated TSH/ less T3/ both
32. TREATMENT
• Patients with severe hypothyroidism, older patients and patients with
CVS disease may have increased sensitivity to thyroid hormones.
• Therefore, they should be given a small dose of thyroid hormone
initially-25μgm of L thyroxin which is gradually increased every 2 to 4
weeks ,to a full maintenance dose during 6-12 wks period .
• Younger patients and patients with less severe hypothyroidism
maybe started on slightly higher dose (50μgm of Lthyroxin) and
advanced to a full replacement dose more quickly
• Most pts require 75-100μgm of L_thyroxin daily.
33. MYXEDEMA
Severe form of hypothyroidism characterized by:-
• stupor, coma, hypoventilation, hypothermia, hypotension and hyponateremia.
Medical emergency with mortality rate of 25-50%.
Sepsis in elderly or exposure to cold may be an initiating event
Management
• Intubation and ventilation as needed.
• Sodium Levothyroxine: 200-300μgm IV over 10min initially and maintenance
200mg|day IV.
• Hydrocortisone -100mg IV ,then 25mg IV Q6hr.
• Fluid and electrolyte supplementation
• Avoid hypothermia
34. ANESTHESIA MANAGEMENT
Preoperative Medication:
• In uncorrected severe hypothyroidism or myxedema coma postpone
elective surgeries and should be treated with IV T3 supplementation
for emergency surgery
• Mild to moderate hypothyroidism may not be absolute contraindication
for urgent surgeries.
• Due to its depressant effect- avoid opioids
• Cortisol supplementation. and aspiration prophylaxis may be
considered
• Continue thyroid hormone therapy until morning of surgery
35. Induction of Anesthesia:
• Ketamine is preferable drug
• If no excessive CVS depression etomidate or thiopental can be used.
• During calculating dose of relaxants keep in mind that the coexisting skeletal
muscle weakness.
Maintenance of Anaesthesia:
• N2O and supplemental short acting opioids, BZD or Ketamine is best.
• Volatiles contraindicated in overtly hypothyroid situation.
• Hypothyroidism does not appear to decrease MAC but decrease in CO
speeds rate of induction by inhalational because CMRO2 is independent of
thyroid function.
• Reduce MAC if body temperature is <37oC.
36. • Pancronium is best relaxant.
• No special consideration about reversals.
• IV fluids should contain sodium.
• Delay extubation until patient respond appropriately with accepted body
temperature.
postoperatively:
• Prolonged postoperative somnolence & inability to wean earlier, so needs
mechanical support.
• Avoid postoperative hypothermia & give adequate analgesic.
If patient comes for other surgery having hypothyroidism Regional
Anesthesia is best than GA
37. THYROID SURGERY UNDER REGIONAL
ANAESTHESIA- CERVICAL PLEXUS BLOCK
DEEP CERVICAL PLEXUS
Patient in supine position, with the
head tilted slightly backward and
turned about 45 degrees to the
opposite side
A line drawn from caudal tip of
mastoid to chassaignac’s
tubercle(transverse process of C6)
along posterior border of
sternomastoid.
Transverse process of c2, 1.5 cm
caudal mastoid process and 1cm
dorsal to line drawn identified and
38. The transverse processes of C3,C4,C5
are also palpated and marked. Distance
between each of them is 1.5 cm
The aim is to block anterior branches of
cervical plexus in the groove of the
transverse process.
The needle is advanced perpendicular
to the skin, medially and slightly
caudally.
After clear bone contact, minimal
withdrawal of the needle, careful
aspiration is done before delivering drug
39. SUPERFICIAL CERVICAL
PLEXUS:
The subcutaneous tissues is
infiltrated in a fan like fashion in
the line of the posterior border
of sternocleidomastoid muscle
in and around its midpoint.
41. NERVE SUPPLY OF LARYNX
SENSORY SUPPLY:
• Above vocal cords: Internal Laryngeal branch of superior laryngeal nerve
• Below vocal cords: Recurrent laryngeal nerve
MOTOR SUPPLY:
• All intrinsic muscles of larynx except cricothyroid muscle are supplied by
recurrent laryngeal nerve
• Cricothyroid is supplied by external laryngeal branch of superior laryngeal
nerve.
42.
43. VOCAL CORD POSITIONS
During respiration, cords are in adduction
During Phonation, cords are in median position
44. CLASSIFICATION OF LARYNGEAL
PARALYSIS
• May be unilateral or bilateral and may involve
1. Recurrent laryngeal nerve
2. Superior laryngeal nerve
3. Both recurrent and superior laryngeal nerve( combined or complete
paralysis)
45. UNILATERAL RECURRENT LARYNGEAL NERVE
PARALYSIS
Ipsilateral paralysis of
all intrinsic muscles of
larynx except
cricothyroid
Vocol cord assumes a
median or paramedian
position and does not
move laterally on deep
inspiration
CLINICAL FEATURES:
Asymptomatic
change in voice which
gradually improves by
compensation from the other
side cord
TREATMENT:
No treatment require
46. BILATERAL RECURRENT
LARYNGEAL NERVE
PARALYSIS
• All intrinsic muscles of larynx
are paralysed
• Vocal cords lie in median or
paramedian position due to
unopposed action of
cricothyroid muscles
• CLINICAL FEATURES:
Dysnoea
Stridor
TREATMENT:
In acute stridor, Tracheostomy
is required
Usually 6 months is an
adequate time to wait for any
spontaneous recovery
lateralization of vocal cords
can be done
Type 2 thyroplasty
48. UNILATERAL SUPERIOR LARYNGEAL NERVE
PARALYSIS
• Paralysis of cricothyroid muscle and ipsilateral anesthesia of larynx
above vocal cord
• Loss of tension of vocal cord and shortening of vocal cord
• CLINICAL FEATURES:
Weak voice with decreased pitch
Occassional aspiration
TREATMENT:
Medialization laryngoplasty
Modified typr 4 thyroplasty
49. BILATERAL SUPERIOR LARYNGEAL NERVE
PARALYSIS
• Both the cricothyroid muscles are paralysed along with anaesthesia of
upper larynx
• CLINICAL FEATURES:
cough
choking fits
weak and husky voice
• TREATMENT:
Tracheostomy with a cuffed tube
Epiglottopexy to close laryngeal inlet to protect lung from repeated
aspirations
50. COMPLETE UNILATERAL VOCAL CORD
PARALYSIS
• Paralysis of all muscles of larynx on one side except interarytenoid
which also receives innervation from opposite side. Cadaveric position
of vocal cord.
• CLINICAL FEATURES:
Vocal cord lies in cadaveric position
hoarseness of voice
Aspiration
• TREATMENT:
Speech therapy
Medialisation of vocal cord: Thyroplasty type 1, injection of teflon
paste
51. BILATERAL COMPLETE VOCAL CORD
PARALYSIS
• Both cords lie in cadaveric position
• Total anesthesia of larynx
CLINICAL FEATURES:
• Aphonia
• Aspiration, Inability to cough and Bronchopneumonia
TREATMENT:
• Tracheostomy
• Epiglottopexy
• Total laryngectomy
52. TRACHEOMALACIA
Increased incidence in large longstanding Goitre
Diagnosis: Air leak around deflated cuff
Management:
Reintubation; Tracheostomy;Ceremic ring support
