EFFECT OF THYROIDISM
PGR- DR.ABDULLAH KHAN
SUPERVISIOR- PROF: DR. IJAZ AHMAD
SCW, KTH, PESHAWAR.
Basic Thyroid Gland Physiology
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,
CONTRACTILITY, WATER / ELECTROLYTE BALANCE,
NORMAL FUNCTION OF CNS.
Dec CO, HR, contractility
Respiratory muscle weakness
< respiratory response to hypoxia/hypercarbia
Dec gut motility
Dec drug clearance
Dec Vit K dep clotting factors
Dec RBM mass normocytic anemia
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
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
If suspicion adrenal insufficiency & no time to test
Stress dose glucocorticoids (usual dose+ 50 mg/100mg (pre-op)
25mg/50mg TDS for 1 2days)
Infection w/o fever
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
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
Patients are more sensitive to hypotensive effects of
anesthetic agents because decreased cardiac output,
intravascular volume. Invasive monitoring on a per patient
Ketamine or Etomidate may be induction agents of choice
Succinylcholine and non-depolarizing muscle relaxants are
generally safe for use. Monitor with peripheral nerve
Controlled ventilation is recommended as patients tend to
Hypothermia occurs quickly and difficult to prevent and
Hematological (anemia, platelet, coag dysfx), electrolyte
imbalances, and hypoglycemia is common and require
close monitoring intraoperatively
Consider co-existed adrenal insufficiency in causes of
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
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
Extubation/Emergence may be delayed secondary to
hypothermia, respiratory depression, or slowed drug
Awake extubation, try to maintain normothermia
Cautiously administer opioids post-op, consider regional
techniques or Ketorolac for post-op pain control
TAKE HOME MESSAGE
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.
NARCOTICS AND SEDATIVES SHOULD BE USED CAUTIOUSLY DUE
TO INC RISK OF RESPIRATORY DEPRESSION.
MORE SENSITIVE TO HYPOTENSIVE EFFECT OF ANESTHETIC
CHOICE ANESTHESIA IS KETAMINE AND AWAKE EXTUBATION.
INC RISK OF HYPOTHERMIA, COAGULATION DYSFUCNTION,
ELECTROLYTE IMBALANCES AND HYPOGLYCEMIA.
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
It is elevated in hyperthyroidism and depressed in
Inc CO, O2 requirements, contractility, HR.
A. Fib 10-20%
Inc risk thyroid storm
No elective OR till control (3-6 weeks)
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.
No controlled study suggest advantages of particular
anesthetic drug or technique for hyperthyroid
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.
Close monitoring of cardiac function and body
temperature is required. Need for invasive
Adequate anesthetic depth should be obtained
prior to laryngoscopy or surgical stimulation to
avoid tachycardia, hypertension, ventricular
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
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
Anesthetic considerations-Thyroid Storm
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
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
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.