Effect of thyroidism on surgery

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  • 1. EFFECT OF THYROIDISM ON SURGERY PGR- DR.ABDULLAH KHAN SUPERVISIOR- PROF: DR. IJAZ AHMAD SCW, KTH, PESHAWAR.
  • 2. 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.
  • 3. Hypothyroidism  low free thyroxine levels and elevated TSH (if primary)
  • 4. 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
  • 5. Mild-Moderate Hypothyroidism ok if urgent/emergent  If elective, delay  L-thyroxine outpatient dosing  1.6mcg/kg if young, healthy 25mcg/d if old/CV disease iv if can’t take po x 5-7days  iv dose 80% of po dose
  • 6. 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  ….
  • 7. 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
  • 8. Hypothyroidism Anesthetic 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  
  • 9. Hypothyroidism Anesthetic 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
  • 10. Hypothyroidism Anesthetic 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
  • 11. Hypothyroidism Anesthetic 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
  • 12. Hypothyroidism Anesthetic 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 
  • 13. Hypothyroidism Anesthetic considerations-Myxedema Coma Treatment  IV thyroxine is indicated (L-thyroxine loading dose 300500ug, followed by 50ug/day for 24-48hrs)  IV hydration with dextrose containing crystalloid, correction of electrolyte abnormalities  Support cardiovascular and pulmonary systems as necessary 
  • 14. Hypothyroidism Anesthetic considerationsPostoperative  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
  • 15. 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.
  • 16. 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.)
  • 17. Hyperthyroidism Causes  Graves Disease-most common  toxic multinodular goiter  TSH hormone secreting pituitary tumors  functioning thyroid adenomas  overdose of thyroid replacement medication
  • 18. 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)
  • 19. Hyperthyroidism Preoperative  Elective surgery is post-poned for 3-6weeks to achieve eu-thyroid status with ATDs, and betablockers.  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.
  • 20. Hyperthyroidism anesthetic 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.
  • 21. Hyperthyroidism anesthetic 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
  • 22. Hyperthyroidism anesthetic 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
  • 23. Hyperthyroidism Anesthetic 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
  • 24. Hyperthyroidism Anesthetic 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%
  • 25. 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.
  • 26. 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.