effect of thyroidism on surgery
TRANSCRIPT
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