CASE DISCUSSION

1. CASE DISCUSSION THYROID SURGERY www.anaesthesia.co.inanaesthesia.co.in@gmail.com

2. CASE HISTORY • SHWETA PRAKASH 32/F • HOUSE WIFE • RESIDENCE – PINJORE • PRESENTING COMPLAINTS • SWELLING IN FRONT OF NECK – 6 yrs

3. HOPI • Noticed small swelling in front of neck on right side, • Gradual increase in size from pea nut to present size • After second pregnancy ( 4 yrs ago) she noticed significant increase in size • No h/o pain, discharge • No h/o fever • No h/o diarrhoea/constipation • No h/o weight gain/ loss

4. HOPI • No h/o headache, palpitation, Sweating • No h/o heat or cold intolerance • No h/o weakness/ easy fatiguability • No h/o change in voice • No h/o breathlessness/ difficulty in swallowing • No h/o menstrual disturbance • No other co-morbid illness

5. Treatment – from local doctor • Past history : no h/o TB , ASTHMA, HT , DM • Menstrual history - • Family history : no similar complaints in family • Personal : • Diet – mixed • Appetite – N • Bowel/ bladder -N

6. General physical examination • Pallor – ( -) Icterus – ( -) • Edema - ( -) Clubbing - ( -) • lymphadenopathy - ( -) • Weight – 68 kg height – 162 cm • Pulse – 82/min ,regular, good volume, all peripheral pulses felt, no radio- radial/radio-femoral delay • Blood pressure – 126/74 mmHg RUL/ supine

7. Airway examination • Mouth opening – 3 FB • Dentition – N • Modified MMP Grade – III • Mento thyroid distance – 4 FB • Neck extension – N

8. Examination of swelling Inspection : • Midline swelling ,extending from upper border of thyroid cartilage to suprasternal notch and between the two SCM • Measurement – 10 X 7 cm • Surface is smooth • Moves with deglutition • Skin over the swelling – N • No visible pulsation/dilated veins

9. palpation • Inspectory findings are confirmed • Local temperature – not raised • All the borders except lower border are palpable • Getting below the swelling not possible • Trachea not palpable • Pemberton’s sign - negative • Auscultation – no bruit

10. Systemic examination • Respiratory system – normal vesicular breath sounds, no added sound • CVS – S1 S2 heard, no murmur • CNS – NAD • PA - NAD

11. Preoperative investigations Complete hemogram - Hb, TLC & DLC, platelets serum electrolytes including calcium Thyroid function tests Chest X-ray, X-ray soft tissue neck AP & lateral views Indirect laryngoscopy : Recurrent laryngeal nerve involvement CT/MRI– retosternal goiter Pulmonary function tests – selected cases Pregnancy test

12. ANATOMY • Bilobed, anterior to trachea between cricoid cartilage and suprasternal notch • Weight – 12 -20 gm Blood supply • Sup thyroid A –branch of external carotid • Inf thyroid A – branch of thyrocervical trunk • Thyroidema ima - 1-4%

13. Nerves Recurrent laryngeal nerve • Lateral border of thyroid • Unilateral injury – ipsilateral vocal cord palsy • Normal but weak voice • Ineffective coughing • Bilateral - airway obstruction and loss of voice Superior laryngeal nerve • Sensory to supraglottic larynx • Injury ↑ risk of aspiration

15. EXAMINATION General Physical examination • Face • mask like face –hypothyroidism • Exopthalmos • Skin – moist hand in thyrotoxicosis Dry skin in myxoedema • Anaemia – malignancy, thyrotoxicosis • Sleeping pulse rate – thyrotoxicosis severity

16. EXAMINATION • Inspection • Normal thyroid – not visible • Pizzillo’s method – hand clasped behind occiput • Moves upwards on deglutition • Retrosternal goiter • Dilated veins over upper thorax • Lower border of thyroid not seen

17. EXAMINATION- Palpation • Slight flexion of neck • Palpated from front and behind • Thumbs behind neck and other fingers on each lobe • Lahey’s method • Palpation of each lobe • Gland pushed to the side of examination by opposite hand • Consistency and mobility

18. EXAMINATION- Palpation • To get below the swelling – retrosternal goiter • Pemberton’s sign • Kocher’s test – slight push on lateral lobe produces stridor • Tracheal position should be confirmed

19. EXAMINATION • Percussion over manubrium sterni –retosternal goiter • Ascultation • Bruit in thyrotoxicosis

20. Assessment of airway in a thyroid patient • Indirect laryngoscopy to see for vocal cord movement • Chest X-ray • X-ray lateral view of neck • CT neck • Pulmonary function testing: non- invasive method • Flow volume loop analysis: extent and location of airway obstruction

22. Thyroid hormone synthesis propylthiouracil Iodine ,β blocker iodides

23. Hypothalamo pituitarythyroid axis

24. What is the effect of thyroid hormone on Cardiovascular system ? ↑ sympathetic activity ↑ heart rate ↑ stroke volume ↑ contractility ↑ cardiac output vasodilatation and  tissue blood flow ↑ oxygen consumption ↓ SVR ↑PVR ↑ automaticity & excitability ↑ SBP with wide pulse pressure

25. What is the effect of thyroid hormone on Respiratory system ?  oxygen consumption & hypercarbia ↓ compensatory  minute volume weak respiratory muscles decreased compliance ↓ decreased vital capacity

26. Gastrointestinal system increased gastrointestinal motility increased appetite and food intake increased rate of secretion of digestive juices decreased GIT transit time

27. Metabolic effects Carbohydrate :-  glucose absorption  glycogenolysis  gluconeogenesis  insulin secretion  cellular uptake of glucose  cellular utility of glucose Fat :-  lipid mobilisation from adipocytes  Free fatty acids ↓ cholesterol, phospholipids, triglycerides

28. Reference Ranges for Serum Thyroid Hormones Hormone SI units Metric units • T4 60-140 nmol / L 4-11 µg/dL • T3 1.1-2.7nmol/L 75-175 ng / dL • TSH 1-18 pmol/L 0.3-5.0 mU/L

30. Goiter • Any enlargement of thyroid gland irrespective of its pathology • Non-toxic –colloid, MNG, • Toxic - graves disease • Neoplastic - benign or malignant • thyroiditis – autoimmune, infectious

31. RETROSTERNAL GOITRE • May be asymptomatic or compression of mediastinal structure • Dyspnoea, dysphagia, • Cerebral hypoperfusion – thyrocervical steal • RLN, phrenic nerve palsy • Majority can be removed by cervical approach • During surgical manipulation – tracheal compression may be worsened

32. Hypothyroidism • Incidence – 0.5 – 0.8% • Etiology • Iatrogenic Iodine deficiency or excess • Autoimmune (Hashimoto’s thyroiditis) • Drugs (e.g., lithium, amiodarone) • After radioactive iodine • Thyroid hormone resistance • Surgical resection Thyroid agenesis • Secondary (pituitary or hypothalamic)

33. Mild to moderate hypothyroidism Lethargy Cold intolerance Weight gain Constipation Voice hoarseness Periorbital and pretibial edema (myxedema) Cardiovascular (↓ HR, ↓ CO, ↑ SVR, ↓ volume, ↓ pulse pressure) Severe hypothyroidism/myxedema Impaired mentation/coma Hypoventilation Signs of CHF Hypothermia Hyponatremia secondary to SIADH, CHF Symptoms and Signs of Hypothyroidism

34. treatment • start with full replacement dose of thyroxine 1.6 µg/kg/d in patients with no significant comorbid illness • in elderly patients or those who have underlying coronary artery disease, start at a dose of 25 to 50 µg once daily • once-daily dosing results in a steady state being reached in about 6 weeks • Serum TSH levels measured 4 to 6 weeks after commencing treatment and every 4 to 6 weeks thereafter until a normal TSH is reached.

35. Hypothyroidism - Anesthetic considerations • Preoperative • avoid elective surgery in symptomatic patients • premedication with H2 blocker & metoclopramide [↓gastric empting ] • Sedative premedication administered in OT • Usual dose of thyroid medication on the morning of surgery • B. Intraoperative • Difficult intubation – large tongue • Susceptible to hypotension -↓CO, blunted baroreceptor reflex, ↓ intravascular volume • Refractory hypotension – coexistent adrenal insufficiency or CHF • Hypoglycemia, anemia, hyponatremia, hypothermia

36. Hypothyroidism - Anesthetic considerations • Treat hypotension with ephedrine 5 mg [direct acting agents ↑SVR ] • C. Postoperative • Delayed recovery from GA • Susceptible to respiratory depression • remain intubated until awake and normothermic • nonopioid such as ketorolac for analgesia

37. Myxoedema coma • Severe form of hypothyroidism with 60% mortality • Myxedema coma is manifested by depressed mental status, delirium or coma, hypothermia, bradycardia, and hypopnoea. • Hypovolemia, low cardiac output, pericardial effusion/tamponade • precipitated by hypothermia, trauma, infections, cerebrovascular accidents, anesthetics, sedatives and analgesics, amiodarone, and lithium

38. Management of Myxedema • Tracheal intubation and controlled ventilation as needed • Levothyroxine, 200–300 μg IV over 5–10 min initially, and 100 μg IV q24h • Hydrocortisone, 100 mg IV, then 25 mg IV q6h • Fluid and electrolyte therapy as indicated by serum electrolytes • Cover to conserve body heat; no warming blankets

39. Thyrotoxicosis and thyroid storm Thyrotoxicosis refers to all disorders of raised thyroid hormone concentration. The clinical spectrum ranges from asymptomatic biochemical abnormalities to life threatening crises with multisystem dysfunction. Thyroid storm exists when a patients metabolic, thermoregulatory and cardiovascular compensatory mechanisms fails.

40. INTRINSIC THYROID DISEASE Hyperfunctioning thyroid adenoma Toxic multinodular goiter ABNORMAL TSH STIMULATOR Graves' disease Trophoblastic tumour DISORDERS OF HORMONE STORAGE Thyroiditis EXCESS PRODUCTION OF TSH Pituitary thyrotropin (rare) Extrathyroidal source of hormone Struma ovarii Functioning follicular carcinoma EXOGENOUS THYROID Iatrogenic Iodine induced TSH, thyroid-stimulating hormone Causes of Hyperthyroidism

41. Symptoms • Hyperactivity, irritability, • dysphoria • Heat intolerance and sweating • Palpitations • Fatigue and weakness • Weight loss with increased appetite • Diarrhoea • Polyuria • Oligomenorrhea, loss of libido

42. Cardiovascular Increased cardiac output Increased chronotropism, inotropism Left ventricular hypertrophy Cardiomyopathy Increased likelihood of angina pectoris Atrial fibrillation Congestive heart failure Thromboembolic events Pulmonary Respiratory dysfunction Myopathy Musculoskeletal General weakness (myopathy) Endocrine Increased production/utilization of cortisol Adrenal hyperplasia Systemic Effects of Hyperthyroidism That Increase Surgical Risk

43. Hematological Anemia Neutropenia Thrombocytopenia Increased factor VIII Decreased vitamin K-dependent coagulation factors Gastrointestinal Hyperdefecation Impaired drug absorption Metabolic Hypercalcemia Increased rate of drug clearance Impaired glucose tolerance Up-regulation of receptors Hypoalbuminemia Systemic Effects of Hyperthyroidism That Increase Surgical Risk

44. Medical treatment • Antithyroid drugs • Inhibit thyroid hormone synthesis by inhibiting thyroid peroxidase • β blockers • Ameliorate action of T3 and T4 • Preparation for surgery and thyrotoxic crisis • Iodine preparations • Lithium inhibit hormone release

45. Beta blocker therapy Benefits :- ↓ HR ↓ C. output ↓ C. irritability Blocks conversion of T4 to T3 Propranolol, labetalol, esmolol Side effects : Hypotension, sedation, depression, bronchospasm

46. Preoperative preparation Emergency surgery • Esmolol 100 – 300 µ/kg/min IV Elective surgery Blocking the production of hormone • Propylthiouracil / methimazole. • Effective in 6 - 8 weeks Blocking the release of T3,T4 • 8 - 10 days preoperatively to reduce vascularity • Lugols iodine – 10 drops tds • SSKI – 5drops qid • Na iodide – 0.5 -1 gm every 12 hrs Decreasing the adrenergic effect Propranolol - 20 to 40 mg

47. Thyroid storm Manifestations:- Fever, tachycardia (SVT) CNS- delirium , seizures , coma GIT- vomiting , diarrhoea No specific lab test can diagnose it High index of suspicion required for diagnosis

48. Precipitating factors of thyroid storm Thyroid causes Thyroid surgery Withdrawal of anti-thyroid drugs Radioiodine Iodinated contrast dyes Vigorous thyroid manipulation Non-thyroid causes Non thyroid surgery Infection, Diabetic ketoacidosis CVA, CHF, Pulmonary embolism Pregnancy, Parturition Trauma Drugs e.g. amiodarone

49. D/D of intaoperative tachycardia & hyperthermia Thyroid storm • Malignant hyperthermia • Pheochromocytoma • Carcinoid crisis

50. Goals of intervention in thyroid storm • Diagnosis and treatment of inciting event • Supportive measures :- • Replace fluids/ glucose/electrolytes • Decrease temperature with acetaminophen, cold lavage, cooling blanket, ice packs • Decrease ambient temperature • Don’t give aspirin as it increases T3, T4 levels • Inotropes, diuretics and O2 for acute cardiac dysfunction.