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

6. 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

7. 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

….

8. 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

9. 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



10. 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

11. 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

12. 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

13. 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


14. 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


15. 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

16. 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.

18. 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.)

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

20. 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)

21. 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.

22. 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.

23. 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

24. 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

25. 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

26. 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%

27. 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.

28. 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.