Thyroid diseases and Thyroid diseases and anaesthesiaanaesthesia

Presented by Dr. Bindu L. ShahPresented by Dr. Bindu L. ShahM.D. II yr anaesthesiaM.D. II yr anaesthesia

Moderator: Prof B.D. JhaModerator: Prof B.D. Jha064/11/2064/11/2

AnatomyAnatomy

15 -25 grams in weight;; 15 -25 grams in weight;; 2 lateral lobes 2 lateral lobes connected by an isthmus, lie at the level C4-connected by an isthmus, lie at the level C4-C7 C7

Closely attached to thyroid cartilage & to Closely attached to thyroid cartilage & to upper end of trachea – thus moves on upper end of trachea – thus moves on swallowingswallowing

Close relationship with rec. laryngeal Close relationship with rec. laryngeal nervenerve

Blood flow very high at 5 ml/min/gm Blood flow very high at 5 ml/min/gm (2x kidney!)(2x kidney!)

Supply: from superior (1st branch of Supply: from superior (1st branch of External Carotid) and inferior thyroid External Carotid) and inferior thyroid arteries ,thyroidea ima arteryarteries ,thyroidea ima artery

Drainage: Sup. mid. and inf. veinsDrainage: Sup. mid. and inf. veins

PhysiologyPhysiology

Functions of the thyroid gland:Functions of the thyroid gland:

1.1. Hormone secretions- T3, T4Hormone secretions- T3, T4

2.2. Synthesis of thyroglobulinSynthesis of thyroglobulin

Iodine: raw materialIodine: raw material

Daily requirement: 300-1000 ug/dayDaily requirement: 300-1000 ug/day

Euthyroidism: 150ug/dayEuthyroidism: 150ug/day

For prevention of goitre:75 ug/dayFor prevention of goitre:75 ug/day

Pregnany: 200ug/day.Pregnany: 200ug/day.

Neonatal: 40 ug/dayNeonatal: 40 ug/day

Biosynthesis and release of Biosynthesis and release of thyroid hormonesthyroid hormones

1.1. Iodide uptakeIodide uptake::2.2. OxidationOxidation: In thyroid, Iodide is converted : In thyroid, Iodide is converted

to iodine with the help of thyroid to iodine with the help of thyroid perooxidaseperooxidase

3.3. Iodination of tyrosineIodination of tyrosine residue that are residue that are part of thyroglobulin molecule & part of thyroglobulin molecule & formation of MIT,DITformation of MIT,DIT

4.4. CouplingCoupling / condensation: DIT+DIT=T4, / condensation: DIT+DIT=T4, DIT+MIT=T3DIT+MIT=T3

5.5. ReleaseRelease : endosytosis T3=4ug/day, : endosytosis T3=4ug/day, T4=80ug/day T4=80ug/day

Contd.Contd.

1/3 of T4 is converted to T3 peripheral 1/3 of T4 is converted to T3 peripheral tissuetissue

T3 : 13% (thyroid), 87% (T4)T3 : 13% (thyroid), 87% (T4)

T4 - 99.95% bind to plasma proteinT4 - 99.95% bind to plasma proteinT3 – 99.50% bind to plasma protein, T3 – 99.50% bind to plasma protein,

lower affinity to plasma protein lower affinity to plasma protein contributes to greater biological contributes to greater biological activity.activity.

contdcontd

T3 acts rapidly ,3-5 times more T3 acts rapidly ,3-5 times more potent than T4 because T3 is loosly potent than T4 because T3 is loosly bound to plasma protein & binds bound to plasma protein & binds more avidly to thyroid hormone more avidly to thyroid hormone receptorsreceptors

PHYSIOLOGY OF PHYSIOLOGY OF HYPOTHALAMIC-PITUITARY-HYPOTHALAMIC-PITUITARY-

THYROID AXISTHYROID AXIS1.1. hypothalamus : TRH released hypothalamus : TRH released

2.2. pituitary :TRH stimulates pituitary for pituitary :TRH stimulates pituitary for TSH release TSH release

3.3. Thyroid :TSH stimulates ,TSH receptor in Thyroid :TSH stimulates ,TSH receptor in the thyroid, to the thyroid, to synthesis both T4, T3 synthesis both T4, T3 increased plasma levels of T4 & T3increased plasma levels of T4 & T3

Mechanisms of action of Mechanisms of action of thyroid hormonesthyroid hormones

Thyroid hormones enters cells & Thyroid hormones enters cells & bind to thyroid receptors in nuclei bind to thyroid receptors in nuclei that binds to DNA, & increase or that binds to DNA, & increase or decrease the expression of genes decrease the expression of genes that regulate cell functionthat regulate cell function

Effects of thyroid hormonesEffects of thyroid hormones

1.1. Influence the growth and maturation of Influence the growth and maturation of tissues.tissues.

2.2. Calorigenic action: increase o2 Calorigenic action: increase o2 consumption, increase BMRconsumption, increase BMR

3.3. CVS: increase heat production, increase CVS: increase heat production, increase body temp. cutaneous vasodilatation, body temp. cutaneous vasodilatation, decrease peripheral resistance, leading decrease peripheral resistance, leading Na. & water retention ----increase blood Na. & water retention ----increase blood vol. CO, rate & pulse pressure increased.vol. CO, rate & pulse pressure increased.

Contd.Contd.

Nervous systemNervous system::

1)1) low-slow mentation; reflexes time low-slow mentation; reflexes time prolomgedprolomged

2)2) high-rapid mentation, irritability, high-rapid mentation, irritability, restless, restless,

reflexes time shortened.reflexes time shortened.

Skeletal muscleSkeletal muscle : weakness, myopathy. : weakness, myopathy.

contdcontd

Relation to catecholamineRelation to catecholamine : : intimately related, however plasma intimately related, however plasma level of catecholamine is normal in level of catecholamine is normal in hyperthyroidism symptoms are hyperthyroidism symptoms are relieved with B blockers.relieved with B blockers.

Carbohydrate metabolism-Carbohydrate metabolism-1.1. physiological- glycogenesisphysiological- glycogenesis2.2. Pharmacological: hyperglycemiaPharmacological: hyperglycemia

Protein metabolismProtein metabolism::

1.1. Physiological- AnabolicPhysiological- Anabolic

2.2. Excess- catabolicExcess- catabolic

Fat metabolismFat metabolism: lipolytic: lipolytic

Vitamin metabolismVitamin metabolism: thyroid hormone : thyroid hormone converts carotene to vit. Aconverts carotene to vit. A

Normal function of thyroid gland – Normal function of thyroid gland – directed to secretion of T3 & T4directed to secretion of T3 & T4

Insufficient hormone secretion – Insufficient hormone secretion – hypothyroidism /myxedemahypothyroidism /myxedema

Excessive secretion – Excessive secretion – hyperthyroidismhyperthyroidism

HYPERTHYROIDISMHYPERTHYROIDISM

Causes:Causes:

1.1. Grave’s diseaseGrave’s disease

2.2. toxic multinodular goitre, toxic multinodular goitre,

3.3. thyroiditis, thyroiditis,

4.4. pituitary tumour ( excess TSH secretion)pituitary tumour ( excess TSH secretion)

5.5. overdosage of thyroid replacement hormoneoverdosage of thyroid replacement hormone

6.6. Carcinoma of thyroid Carcinoma of thyroid

Pathogenesis of graves Pathogenesis of graves diseasedisease

TSH receptor abs( thyroid TSH receptor abs( thyroid stimulating immunoglobulins) reacts stimulating immunoglobulins) reacts with the TSH receptor to stimulate with the TSH receptor to stimulate both function & growth of thyroid both function & growth of thyroid gland.gland.

Clinical manifestationClinical manifestation

CVS is the most important organ CVS is the most important organ involvement. involvement.

1.1. Sinus tachycardia,Sinus tachycardia,

2.2. AF, AF,

3.3. precipitation of IHD, precipitation of IHD,

4.4. cardiac failurecardiac failure

5.5. Increase CO & pulse pressureIncrease CO & pulse pressure

Thyroid: diffuse or nodular goitreThyroid: diffuse or nodular goitre GIT: wt. loss, increased appetite, diarrhoeaGIT: wt. loss, increased appetite, diarrhoea Nervous system: nervousness, emotional liability, Nervous system: nervousness, emotional liability,

psychosis, hyperreflexiapsychosis, hyperreflexia Muscular : fine tremors, muscle weakness, Muscular : fine tremors, muscle weakness,

myopathy.myopathy. Dermatological: increase sweating,Dermatological: increase sweating, Reproductive: menstrual disturbances, infertility, Reproductive: menstrual disturbances, infertility,

impotenceimpotence Miscellaneous: heat intolerance,fatigueMiscellaneous: heat intolerance,fatigue Eye: exophthalmos,lid lag ,lid rectractionEye: exophthalmos,lid lag ,lid rectraction

1. Medical Therapy1. Medical Therapy

a) Beta-blockade: a) Beta-blockade: most rapid method of reversing most rapid method of reversing

symptoms symptoms effective within 12 - 24 hrs effective within 12 - 24 hrs may inhibit peripheral conversion of T4 may inhibit peripheral conversion of T4

to T3 as well as blocking beta catech-to T3 as well as blocking beta catech-olamine receptors olamine receptors

usually only used to tide over while usually only used to tide over while other therapies take effect other therapies take effect

b) Methimazole/Carbimazole b) Methimazole/Carbimazole carbimazole is the prodrug of methimazole carbimazole is the prodrug of methimazole iodinated molecule blocks iodination of iodinated molecule blocks iodination of

tyrosine residues tyrosine residues effects seen after 3 - 4 weeks effects seen after 3 - 4 weeks can be used as the sole therapy for can be used as the sole therapy for

hyperthyroidism: given for a period of 12 -hyperthyroidism: given for a period of 12 -18 mths but relapse rate >50% 18 mths but relapse rate >50%

SFx - rash, arthralgia, N&V SFx - rash, arthralgia, N&V agranulocytosisagranulocytosis

c) Propylthiouracil c) Propylthiouracil mechanism of action: a) as for mechanism of action: a) as for

carbimazole and b) blocks peripheral carbimazole and b) blocks peripheral conversion of T4 to T3 conversion of T4 to T3

faster onset of action cf carbimazole (due faster onset of action cf carbimazole (due to 'b' above) to 'b' above)

SFx same as carbimazole; can convert SFx same as carbimazole; can convert from one drug to the other if SFx a from one drug to the other if SFx a problem problem

d) Ablative Therapy d) Ablative Therapy Radioactive Iodine (I131) Radioactive Iodine (I131) I131 concentrates in the thyroid and destroys I131 concentrates in the thyroid and destroys

functioning cells functioning cells takes 6 -10 weeks for clinical effect takes 6 -10 weeks for clinical effect repeat doses often necessary repeat doses often necessary hypothyoidism can occur up to years after hypothyoidism can occur up to years after

therapy therapy aside from hypothyroidism, few side effects aside from hypothyroidism, few side effects pregnancy an absolute contraindication pregnancy an absolute contraindication no evidence for inherited genetic damage in no evidence for inherited genetic damage in

babies if mother has had therapy in the past babies if mother has had therapy in the past

2. Surgery2. Surgery Due to I131, surgery for hyperthyroidism is Due to I131, surgery for hyperthyroidism is

less commonly required now than in the less commonly required now than in the past. Subtotal thyroidectomy attempts to past. Subtotal thyroidectomy attempts to preserve the correct amount of tissue to preserve the correct amount of tissue to allow euthyroid state post-op. allow euthyroid state post-op. Complications include: Complications include:

hypo- (or occasionally hyper-) thyroidism hypo- (or occasionally hyper-) thyroidism hypoparathyroidismhypoparathyroidism

ANAESTHETIC ANAESTHETIC IMPLICATIONSIMPLICATIONS

Hyperthyroidism Hyperthyroidism Except for absolute emergency surgery, all patients Except for absolute emergency surgery, all patients

should be clinically euthyroid prior to surgery. should be clinically euthyroid prior to surgery. Pharmacological stabilisation of hyperthyroid Pharmacological stabilisation of hyperthyroid

patient requires at least 6 -8 weeks. Beta-blockade patient requires at least 6 -8 weeks. Beta-blockade combined with iodide (or lithium) can achieve combined with iodide (or lithium) can achieve euthyroid state in 1 -2 weeks but cardiac effects euthyroid state in 1 -2 weeks but cardiac effects take longer to resolve. take longer to resolve.

risk of thyroid storm provoked intraop or, more risk of thyroid storm provoked intraop or, more frequently, postop frequently, postop

other risks of hyperthyroidism: other risks of hyperthyroidism: cardiac failure cardiac failure increased sensitivity to catecholamine-induced increased sensitivity to catecholamine-induced

arrhythmias arrhythmias

Emergency Surgery in Emergency Surgery in hyperthyroid patienthyperthyroid patient

commence anti-thyroid Rx as soon as commence anti-thyroid Rx as soon as diagnosis made (in conjunction with diagnosis made (in conjunction with specialist endocrinologist) specialist endocrinologist)

preop sedation, eg with preop sedation, eg with benzodiazepinebenzodiazepine

IntraoperativelyIntraoperatively: : avoid sympathetic stimulation, eg ketamine, avoid sympathetic stimulation, eg ketamine,

pancuronium, adrenaline in LA pancuronium, adrenaline in LA continue beta-blockade titrated to heart rate continue beta-blockade titrated to heart rate consider regional technique to decreased symp. consider regional technique to decreased symp.

stimulation stimulation monitor HR, Temp, IBP, ETCO2, SpO2, ABGs monitor HR, Temp, IBP, ETCO2, SpO2, ABGs may have increased inhalational anaesthetic may have increased inhalational anaesthetic

requirement due to increased cardiac output, increased requirement due to increased cardiac output, increased temperature, ? CNS excitation temperature, ? CNS excitation

care with exopthalmic eyes care with exopthalmic eyes Postoperatively:Postoperatively:

intensive monitoring intensive monitoring

Thyroid SurgeryThyroid Surgery

Preoperative Assessment:Preoperative Assessment: 1. Gland Function - is the patient clinically euthyroid?1. Gland Function - is the patient clinically euthyroid? most important indicator of adequacy of medical preparation most important indicator of adequacy of medical preparation

is resolution of symptoms, weight gain & normal heart rate is resolution of symptoms, weight gain & normal heart rate assess cardiac status assess cardiac status history & examination history & examination investigations: CXR, ECG,ischaemia as indicated investigations: CXR, ECG,ischaemia as indicated review investigations, esp. recent TFTs review investigations, esp. recent TFTs keep in mind possible associated conditions; myaesthenia keep in mind possible associated conditions; myaesthenia

gravis & rheumatoid arthritis with Graves's disease and gravis & rheumatoid arthritis with Graves's disease and phaechromocytoma with medullary Ca of the thyroid phaechromocytoma with medullary Ca of the thyroid

- Airway:Airway:- Determine ease of intubationDetermine ease of intubation- Compression Symtoms:- hoarseness of voice, Compression Symtoms:- hoarseness of voice,

stridor, dysphagiastridor, dysphagia- Cervical x-ray – tracheal deviationCervical x-ray – tracheal deviation / /

compressionrcompressionr- Retrosternal spread (SVC obstruction)Retrosternal spread (SVC obstruction)

Preparation of the patientPreparation of the patient

Current medication: Current medication: continue medication & serve on morning of continue medication & serve on morning of

surgery surgery Indirect laryngoscopyIndirect laryngoscopy- ENT review on vocal cord function as a ENT review on vocal cord function as a

baseline findingbaseline findingPremedicationPremedication1.1. reassurancereassurance2.2. no premedication in pt with airway obstructionno premedication in pt with airway obstruction3.3. Pt adequately sedated to prevent anxiety & Pt adequately sedated to prevent anxiety &

apprehension ( BDZ / narcotic premedication )apprehension ( BDZ / narcotic premedication )

Monitoring:Monitoring:

Detection of disconnection or cyanosis Detection of disconnection or cyanosis essential and difficult as patient is essential and difficult as patient is completely covered in drapes. completely covered in drapes. Ventilator Ventilator alarm, precordialalarm, precordial stethoscope,stethoscope, ETCO2ETCO2, , oximetry,oximetry, etc should be considered. etc should be considered.

NIBP, ECG essential. Consider arterial line NIBP, ECG essential. Consider arterial line if poorly controlled. if poorly controlled.

Temperature monitoring and provision for Temperature monitoring and provision for cooling .cooling .

InductionInduction

A- A- No difficulty anticipated:No difficulty anticipated: - usual iv induction & intubation (fentanyl, STP, non-depolarizing - usual iv induction & intubation (fentanyl, STP, non-depolarizing muscle relaxantmuscle relaxantB- possible difficulty in intubationB- possible difficulty in intubation:: - iv induction, test ventilation when pt is unconscious, intubation - iv induction, test ventilation when pt is unconscious, intubation +- suxamethonium+- suxamethoniumC- definite intubation problem / evidence of airway obstructionC- definite intubation problem / evidence of airway obstruction - awake fibreoptic intubation- awake fibreoptic intubation - inhalational induction- inhalational induction- choice of ETT- armoured ETT (< risk of kinking)- choice of ETT- armoured ETT (< risk of kinking)

Intraop.Intraop.

Control over cardiovascular refexes at Control over cardiovascular refexes at all times - adequate depth of all times - adequate depth of anaesthesia required.anaesthesia required.

Airway : secure it Airway : secure it

Posture:Posture:

Head-down slightly, protect eyes and Head-down slightly, protect eyes and nerves, extend neck. nerves, extend neck.

Intra op.Intra op.

Choice of anaesthetic agents:Choice of anaesthetic agents:

- induction agent – thiopentone- induction agent – thiopentone

- muscle relaxant – atracurium, - muscle relaxant – atracurium, vecuroniumvecuronium

- volatile agent – isoflurane - volatile agent – isoflurane

- narcotic analgesics – fentanyl, morphine- narcotic analgesics – fentanyl, morphine

- anaesthetic technique – balanced - anaesthetic technique – balanced anaesthesia with N2O-O2-isoflurane-muscle anaesthesia with N2O-O2-isoflurane-muscle relaxant-narcotic analgesics --- IPPVrelaxant-narcotic analgesics --- IPPV

Extubation: uncomplicate reverse Extubation: uncomplicate reverse & extubate as usual& extubate as usual

Check vocal cord movements .Check vocal cord movements .

precautionsprecautions

- avoid ketamine, pancuronium, indirect-acting adrenergic avoid ketamine, pancuronium, indirect-acting adrenergic agonists & other drugs that stimulate the sympathetic nervous agonists & other drugs that stimulate the sympathetic nervous systemsystem

- Prone to exaggerated hypotensive response on inductionProne to exaggerated hypotensive response on induction- Achieve adequate anaesthetic depth before laryngoscopy / any Achieve adequate anaesthetic depth before laryngoscopy / any

surgical stimulation surgical stimulation - Administer neuromuscular blocking agent cautiously Administer neuromuscular blocking agent cautiously

( thyrotoxicosis a/w ( thyrotoxicosis a/w incidence of MG & myopathies )incidence of MG & myopathies )- Hyperthyroidism does not Hyperthyroidism does not anaesthetic requirements anaesthetic requirements

Post op. mg.Post op. mg.

Monitoring aggresively.Monitoring aggresively.

Complication: post.opComplication: post.op

1)Airway obstruction1)Airway obstruction

Possible causes:Possible causes:

- neck haematoma with tracheal - neck haematoma with tracheal

compressioncompression

- recurrent laryngeal nerve palsy- recurrent laryngeal nerve palsy

- tracheomalacia- tracheomalacia

- incomplete reversal- incomplete reversal

Complication, contd.Complication, contd.

2)Thyroid crisis / storm2)Thyroid crisis / storm

Life-threatingLife-threating- Decompensated hyperthyroidism with Decompensated hyperthyroidism with

excessive release of thyroid hormoneexcessive release of thyroid hormone

- May mimic :malignant hyperthermia, May mimic :malignant hyperthermia, pheochromocytoma pheochromocytoma

Complication,contdComplication,contd

Symptoms/signSymptoms/sign

Onset – intraoperative / 6-24 hours after surgery.Onset – intraoperative / 6-24 hours after surgery.

hyperpyrexia,sweating,hyperventilationhyperpyrexia,sweating,hyperventilation

CVS: tachycardia atrial fibrillation,CCF,shokCVS: tachycardia atrial fibrillation,CCF,shok

GIT: vomiting, acute abdominal pain GIT: vomiting, acute abdominal pain simulation. simulation.

CNS: coma, agitation, psychosis, restless,CNS: coma, agitation, psychosis, restless,

PrecipitantsPrecipitants

- InfectionInfection- surgerysurgery- poorly prepared thyroid surgerypoorly prepared thyroid surgery- diabetic ketosisdiabetic ketosis- radioiodine therapy in a poorly prepared ptradioiodine therapy in a poorly prepared pt- MIMI

Investigate for precipitants – FBC, blood glucose, FT4, Investigate for precipitants – FBC, blood glucose, FT4, FT3FT3

ManagementManagement

medical emergency; cannot wait for laboratory confirmation medical emergency; cannot wait for laboratory confirmation 02, active cooling (not aspirin as it displaces T4 from TBG) 02, active cooling (not aspirin as it displaces T4 from TBG) Beta-blockade: I.V. Propanolol 1-5 mg slowly 4-6hrly, Beta-blockade: I.V. Propanolol 1-5 mg slowly 4-6hrly,

promptly treats fever, tachycardia, tremor; does not reduce promptly treats fever, tachycardia, tremor; does not reduce O2 consumption O2 consumption

Care with Beta-blockers if heart failure (could try esmolol) Care with Beta-blockers if heart failure (could try esmolol) steroids Rx often recommended due to possible steroids Rx often recommended due to possible

"adrenocortical exhaustion" "adrenocortical exhaustion" iv dexamethasone 2mg 6hrly inhibits iv dexamethasone 2mg 6hrly inhibits thyroid hormone releasethyroid hormone release & peripheral conversion, & peripheral conversion,

Iodide IV (as KI 60mg bd or NaI 1.0 - 2.5 g) rapidly controls Iodide IV (as KI 60mg bd or NaI 1.0 - 2.5 g) rapidly controls thyrotoxicosis thyrotoxicosis

Can use lithium if allergic to iodideCan use lithium if allergic to iodide Oral antithyroid drugs commenced as soon as possible Oral antithyroid drugs commenced as soon as possible

complicationcomplication

3)Tetany3)Tetany - Hypocalcemia develops 24-72 hrs postop.Hypocalcemia develops 24-72 hrs postop.- clinical manifestations: circumoral tingling, clinical manifestations: circumoral tingling,

paraesthesia, laryngeal spasm, paraesthesia, laryngeal spasm, - (+)ve Chvostek & Trousseau signs(+)ve Chvostek & Trousseau signs- May result from respiratory alkalosisMay result from respiratory alkalosis - over-ventilation in immediate - over-ventilation in immediate postoperative periodpostoperative period - hypocalcemia from - hypocalcemia from hypoparathyroidismhypoparathyroidism

Management.Management.

- Calcium estimationCalcium estimation- Slow injection of 10% calcium Slow injection of 10% calcium

gluconate 10 mls IVgluconate 10 mls IV

HYPOTHYROIDISMHYPOTHYROIDISM

CausesCauses- autoimmune disease, thyroidectomy, radioactive autoimmune disease, thyroidectomy, radioactive

iodine, antithyroid medications, iodine deficiency, iodine, antithyroid medications, iodine deficiency, failure of hypothalamic-pituitary axisfailure of hypothalamic-pituitary axis

Clinical manifestations:Clinical manifestations:- weight gain, cold intolerance, muscle fatigue, weight gain, cold intolerance, muscle fatigue,

lethargy, constipation, hypoactive reflexes, lethargy, constipation, hypoactive reflexes, depression, dull facial expression, depression, dull facial expression,

HR, stroke volume, COHR, stroke volume, CO- Pleural, abdominal, pericardial effusionPleural, abdominal, pericardial effusionDx:Dx: low free T4 level low free T4 level

Myxedema ComaMyxedema Coma

- Results from extreme hypothyroidismResults from extreme hypothyroidism- Precipitated by – infection, surgery, traumaPrecipitated by – infection, surgery, trauma- C/f: - most pts are female, elderlyC/f: - most pts are female, elderly - impaired mentation- impaired mentation - hypoventilation- hypoventilation - hypothermia- hypothermia - hypotension- hypotension - bradycardia- bradycardia - comatose- comatose - hyporeflexia- hyporeflexia - hyponatremia - hyponatremia

ManagementManagement

I)T3, T4, TSH, FBC, I)T3, T4, TSH, FBC, ii) Should start on clinical groundsii) Should start on clinical groundsiii) Thyroid hormone replacementiii) Thyroid hormone replacement - T4:- iv 200 mcg bolus, daily dose- T4:- iv 200 mcg bolus, daily dose 100mcg till pt can take orally100mcg till pt can take orally - T3:- iv/oral 10-20mcg bd till T4 - T3:- iv/oral 10-20mcg bd till T4 can be given orallycan be given orallyiv)steroids:- iv hydrocortisone 100mg stat, iv)steroids:- iv hydrocortisone 100mg stat,

50-100mg50-100mg

ventilation: assisted ventilation if RFventilation: assisted ventilation if RF

vi) hypothermia: vi) hypothermia: - do not warm rapidly (>1C/hr)– CVS collapsedo not warm rapidly (>1C/hr)– CVS collapse- Blankets & close temperature monitoring Blankets & close temperature monitoring

vii) Hypotensionvii) Hypotension

viii) Hyponatremia viii) Hyponatremia - caused by dilution & redistributioncaused by dilution & redistribution- Fluid restrictionFluid restriction

ix) Tx of precipitating factorsix) Tx of precipitating factors

* Full recovery – replacement * Full recovery – replacement thyroxine dose titrated once / 2-3 thyroxine dose titrated once / 2-3 weeks to maintain euthyroid state.weeks to maintain euthyroid state.

PREOPERATIVEPREOPERATIVE

Severe hypothyroidism ( T4 <1mg/dL):Severe hypothyroidism ( T4 <1mg/dL): Elective case – to correct firstElective case – to correct first Emergency case – to treat with Emergency case – to treat with

thyroid hormone prior to surgerythyroid hormone prior to surgery

Mild – moderate:- no absolute C/IMild – moderate:- no absolute C/I

AirwayAirwayii- CVSii- CVSIii- endocrine statusIii- endocrine status - coarse dry skin, slow mentation, cold - coarse dry skin, slow mentation, cold intolerance, intolerance, - - CO, hyporeflexia, hypoglycaemiaCO, hyporeflexia, hypoglycaemia Increased sensitivity towards anaesthetic agents Increased sensitivity towards anaesthetic agents

& central depressants& central depressants Hypotension & cardiac arrest following inductionHypotension & cardiac arrest following induction Delayed recovery from GADelayed recovery from GA

PremedicationPremedication

Do not require much, prone to drug-Do not require much, prone to drug-induced respiratory depressioninduced respiratory depression

Histamine H2 antagonists & Histamine H2 antagonists & metoclopramide – slowed gastric metoclopramide – slowed gastric emptying timesemptying times

INTRAOPERATIVEINTRAOPERATIVE

susceptible to hypotensive effect of anaesthetic agentssusceptible to hypotensive effect of anaesthetic agents - - CO CO - blunted baroreceptor reflexes- blunted baroreceptor reflexes - - intravascular volume intravascular volume - induction agent of choice – ketamineinduction agent of choice – ketamine- does not - does not MAC MAC- Potential problemsPotential problems - hypoglycemia, anemia, hypoNa+- hypoglycemia, anemia, hypoNa+ - difficult intubation d/t large tongue- difficult intubation d/t large tongue - hypothermia d/t low BMR- hypothermia d/t low BMR

POSTOPERATIVEPOSTOPERATIVE

- delayed recovery – hypothermia, delayed recovery – hypothermia, respiratory depression, slowed drug respiratory depression, slowed drug biotransformationbiotransformation

- Should remain intubated till awake & Should remain intubated till awake & close to normothermicclose to normothermic

- Postoperative pain relief – nonopiod Postoperative pain relief – nonopiod (ketorolac(ketorolac

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