EFFECT OF THYROIDISM ON SURGERY

PGR- DR.ABDULLAH KHAN

SUPERVISIOR- PROF: DR. IJAZ AHMAD

SCW, KTH, PESHAWAR.

Basic Thyroid Gland Physiology•HORMONES TRIIODOTHYRONINE (T3) AND THYROXINE (T4) ARE BOUND TO PROTEINS AND STORED IN THE THYROID GLAND. •T3 IS MORE POTENT AND LESS PROTEIN BOUND, MOST T3 IS MADE IN PERIPHERAL TISSUES FROM THE DE-IODINATION OF T4•BOTH HORMONES INCREASE CARBOHYDRATE AND FAT METABOLISM, INCREASING METABOLIC RATE, MINUTE VENTILATION, HEART RATE AND CONTRACTILITY, WATER / ELECTROLYTE BALANCE, NORMAL FUNCTION OF CNS.

Hypothyroidism

low free thyroxine levels and elevated TSH (if primary)

Clinical Manifestation

Hypometabolism Dec CO, HR, contractility

Hypoventilation

Respiratory muscle weakness

< respiratory response to hypoxia/hypercarbia

Dec gut motility

Hyponatremia

Dec drug clearance

Dec Vit K dep clotting factors

Dec RBM mass normocytic anemia

WHAT TO DO?

Mild-Moderate Hypothyroidism

ok if urgent/emergent If elective, delay

L-thyroxine outpatient dosing 1.6mcg/kg if young, healthy25mcg/d if old/CV diseaseiv if can’t take po x 5-7days iv dose 80% of po dose

Severe Hypothyroidism

No good data of what to do Only emergency surgery since high risk i.v L-T4 200-300mcg 50mcg od for 24-48hrs i.v L-T3 5-20mcg 2.5-10mcg q8h x 2 days or till alert

….

Cont:

If suspicion adrenal insufficiency & no time to test Stress dose glucocorticoids (usual dose+ 50 mg/100mg (pre-op)

25mg/50mg TDS for 1 2days) Monitor

Hemodynamics Fluid/lytes Ileus Neuro-psych Infection w/o fever

HypothyroidismAnesthetic considerations-Preoperative

Patients with uncorrected severe hypothyroidism (T4<1 ug/dL) or myxedema coma should not undergo elective surgery. Potential for severe cardiovascular instability intraoperatively and myxedema coma.

If emergency surgery is necessary, in patients with overt disease or myxedema coma, IV thyroxine and steroid coverage.

Euthyroid state is ideal, however, subclinical cases of hypothyroidism has not been shown to significantly increase risk of surgery

Continue thyroid replacement meds on morning of surgery

HypothyroidismAnesthetic considerations-Preoperative

Airway eval: patients tend to be obese, large tongue, short neck, goiter, swelling of upper airway

Pre-op sedation should be administered cautiously if at all, as patients are more prone to drug included respiratory depression from sedatives and narcotics

Consider aspiration prophylaxis as many hypothyroid patients have delayed gastric emptying times

HypothyroidismAnesthetic considerations-Intraoperative

Patients are more sensitive to hypotensive effects of anesthetic agents because decreased cardiac output, blunted baroreceptor reflexes, and decreased intravascular volume. Invasive monitoring on a per patient basis

Ketamine or Etomidate may be induction agents of choice Succinylcholine and non-depolarizing muscle relaxants are

generally safe for use. Monitor with peripheral nerve stimulation.

Controlled ventilation is recommended as patients tend to hypoventilate

HypothyroidismAnesthetic considerations-Intraoperative

Hypothermia occurs quickly and difficult to prevent and treat

Hematological (anemia, platelet, coag dysfx), electrolyte imbalances, and hypoglycemia is common and require close monitoring intraoperatively

Consider co-existed adrenal insufficiency in causes of refractory hypotension

HypothyroidismAnesthetic considerations-Myxedema Coma

Rare form of decompensated Hypothyroidism characterized by stupor or coma, hypoventilation,

hypothermia, bradycardia, hypotension, and severe dilutional hyponatremia(SIADH), CHF

Medical emergency with mortality rate of 15-20% Infection, cold, CNS depressants predispose hypothyroid

patients, especially in elderly

HypothyroidismAnesthetic considerations-Myxedema Coma

Treatment IV thyroxine is indicated (L-thyroxine loading dose 300-

500ug, followed by 50ug/day for 24-48hrs) IV hydration with dextrose containing crystalloid,

correction of electrolyte abnormalities Support cardiovascular and pulmonary systems as

necessary

HypothyroidismAnesthetic considerations-Postoperative

Extubation/Emergence may be delayed secondary to hypothermia, respiratory depression, or slowed drug metabolism

Awake extubation, try to maintain normothermia Cautiously administer opioids post-op, consider regional

techniques or Ketorolac for post-op pain control

TAKE HOME MESSAGE

1. DELAY SURGERY IN ELECTIVE CONDITIONS WHILE CAN GO FOR EMERGENT SITUATION WITH HIGH RISK CONSENT AND COVERING THE PATIENT WITH I.V THYROXIN AND STEROIDS.

2. NARCOTICS AND SEDATIVES SHOULD BE USED CAUTIOUSLY DUE TO INC RISK OF RESPIRATORY DEPRESSION.

3. MORE SENSITIVE TO HYPOTENSIVE EFFECT OF ANESTHETIC AGENT.

4. CHOICE ANESTHESIA IS KETAMINE AND AWAKE EXTUBATION.

5. INC RISK OF HYPOTHERMIA, COAGULATION DYSFUCNTION, ELECTROLYTE IMBALANCES AND HYPOGLYCEMIA.

HYPERTHYROIDISM

Elevated total and free T4, T3, low TSH, elevated free thyroxine index (The FTI is obtained by multiplying the (Total T4) times (T3 Uptake) to obtain an index.

The FTI is considered a more reliable indicator of thyroid status in the presence of abnormalities in plasma protein binding.

It is elevated in hyperthyroidism and depressed in hypothyroidism.)

Hyperthyroidism

Causes

Graves Disease-most common toxic multinodular goiter TSH hormone secreting pituitary tumors functioning thyroid adenomas overdose of thyroid replacement medication

CLINICLA MANIFESTATION

Inc CO, O2 requirements, contractility, HR. A. Fib 10-20% Inc SOB Dec weight/malnutrition Inc risk thyroid storm No elective OR till control (3-6 weeks)

HyperthyroidismPreoperative

Elective surgery is post-poned for 3-6weeks to achieve eu-thyroid status with ATDs, and beta-blockers.

With emergent surgery, there is insufficient time to allow ATDs to achieve euthyroid state. Therefore, a combination of beta-blockers, iodine and high-dose steroids is given to rapidly facilitate safe surgery.

Hyperthyroidismanesthetic consideration-Intraoperative

No controlled study suggest advantages of particular anesthetic drug or technique for hyperthyroid patients, however:

Drugs that stimulate sympathetic nervous system should be avoided because of the possibility of large increases in blood pressure and heart rate. Ex. Ketamine. Pancuronium, atropine, ephedrine, epi

Thiopental may be induction agent of choice as it possess antithyroid activity at high doses.

Hyperthyroidismanesthetic consideration-Intraoperative

Close monitoring of cardiac function and body temperature is required. Need for invasive monitoring?

Adequate anesthetic depth should be obtained prior to laryngoscopy or surgical stimulation to avoid tachycardia, hypertension, ventricular dysrhythmias

Eye protection

Hyperthyroidismanesthetic consideration-Intraoperative

Anticipate exaggerated hypotensive response during induction as patient may be hypovolemic

Muscle relaxants can be given safely. Note patients with autoimmune thyrotoxicosis are associated with an increase risk of myopathies and myasthenia gravis. Reversal with glycopyrrolate instead of atropine

volatile agents can be used safely

HyperthyroidismAnesthetic considerations-Postoperative

Thyroid storm is most serious post-op problem Characterized by: hyperpyrexia, tachycardia, altered

consciousness, and hypertension Precipitating factors: infection, Incidence is 10% in patients hospitalized for thyrotoxicosis Onset is usually 6-24 hours after surgery, but can happen

intraoperatively mimicking malignant hyperthermia(MH) Unlike MH, not associated with muscle rigidity, elevated

CPK, or marked degree or lactic or respiratory acidosis

HyperthyroidismAnesthetic considerations-Thyroid Storm

Treatment: ABC’s

IV Hydration, cool patient IV propanolol (.5mg increments)/esmolol to control heart rate

until less than 100. Propylthiouracil 250mg Q6 hours orally or by NG tube Sodium Iodide 1 gram over 12 hours correction of any precipitating events (infection) Cortisol is recommended if there is any coexisting adrenal gland

suppression Mortality rate is approximately 20%

Surgical Outcomes & Tx

No good studies are available to compare the difference between the different parameters e.g. wound healing, chances of infection, pain etc of hyperthyroid to normal patients having surgery.

TAKE HOME MESSAGE

POST PONED ELECTIVE SURGERY FOR 3-6 WEEKS TO OBATIAN A EUTHYROID SATUTS AND PERFORM EMERGENCY SURGERY UNDER THE COVER OF IV BETA BLOKERS,IODINE AND HIGH-DOSE STEROIDS.

KETAMINE, PANCURONIUM, ATROPINE, EPHEDRINE AND EPINEPHRINE SHOULD BE AVOIDED.

THIPENTOL IS THE INDUCTION AGENT OF CHOICE. CLOSED MOINTERING OF B.P AND TEMP. ADEQUATE SEDATION BEFORE LARYNGOSCOPY. PROMPT DIAGNOSIS OF THYORID STROM AND ITS TREATMENT.

THANKS