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Hypothyroidism
Hypothyroidism
Clinical causes
Clinical manifestations
Diagnosis
Treatment
Preoperative management
Intraoperative management
Postoperative management
Clinical causes:
-Hashimotos thyroiditis
-iodine deficiency
-radioactive iodine
-antithyroid medications
-thyroidectomy
-secondary hypothyroidism
Clinical manifestations
-weight gain
-cold intolerance
-muscle fatigue
-lethargy
-constipation
-reflex decreased (hyporeflexia)
-depression
Primary hypothyroidism:
-decreased T3
-decreased T4
-increased TSH
Secondary hypothyroidism:
-decreased T3
-decreased T4
-decreased TSH
Oral replacement:
-physiological effect within few days
-clinical improvement within several weeks
Myxedema/emergency:
-loading dose: levothyroxine 300 - 500mg
-maintenence doses: ex. levothyroxine 50 mg q day
Elective surgery:
-thyroid hormone level should be therapeutic
Emergency surgery:
give thyroid hormone prior to procedure in patients with:
-uncorrected severe hypothyroidism T4< 1mg/dL
-myxedema coma
Premedication:
-may not be required due to the sedative nature of the disease (lethargy, depression)
-may be more prone to opiod induced respiratory depression
Intraoperative management:
induction: ketamine may be considered induction agent of choice
Airway: may be difficult intubation due to large tongue
CNS:
same MAC requirements
CVS:
senstive to cardiodepressant effects of volatile anesthetics due to:
-decreased intravascular volume therefore decreased preload
-blunted baroreceptor response theferefore decreased HR
-overall decreased cardiac output
Other possible intraoperative complications:
-hypoglycemia
-hyponatremia
-hypothermia
-large tongue for difficult ventilation/intubation
May have delayed emergence/recovery from GA due to:
-hypothermia
-respiratory depression
-delayed/slowed drug biotransformation
*therefore may require prolonged mechanical ventilation
*ketorolac may be preferred to opiod analgesia due to less risk of drug induced respiratory depression