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Asst.professor in Anaesthesiology , Kanyakumari govt. medical college, Nagercoil . HYPOTHYROIDISM AND OBSTETRIC ANAESTHESIA . DR A. Vasukinathan MD DA. Hypothyroidism is a clinical condition resulting from inadequate circulating levels of thyroid hormones.

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asst professor in anaesthesiology kanyakumari govt medical college nagercoil
Asst.professorin Anaesthesiology,

Kanyakumarigovt. medical college,

Nagercoil.

HYPOTHYROIDISM AND OBSTETRIC ANAESTHESIA

DR A. Vasukinathan MD DA

slide2

Hypothyroidism is a clinical condition resulting from inadequate circulating levels of thyroid hormones.

  • The prevalance in pregnancy is 0.3%.
obstetric complications
OBSTETRIC COMPLICATIONS
  • Anaemia
  • Pre-eclampsia
  • IUGR
  • Placental abruption
  • PPH
  • Fetal Distress during labour
causes
Causes
  • Primary
  • Auto immune hypothyroidism (Hashimoto’s Thyroiditis)
  • Iatrogenic
  • - 131I treatment
  • - Thyroidectomy
  • - Irradiation therapy of neck for lymphomas
  • Iodine deficiency
slide5

Transient

  • Withdrawal of thyroxine treatment in patients with intact thyroid
  • Sub acute thyroiditis
  • Secondary
  • Hypopituitarism
  • Isolated TSH deficiency
  • Hypothalamic disease
diagnosis
DIAGNOSIS
  • Normal T4 in Pregnancy-8-16mg/dl(<2.8)
  • Normal TSH in Pregnancy<10mIU/dl(>88)
  • Primary Hypothyroidism has a low T3 , T4 and a raised TSH level.
  • Secondary Hypothyroidism has a low T3 , T4 and TSH levels
treatment
TREATMENT
  • Levothyroxine - 1.5µg/kg (100-150 µg/day) orally similar to non pregnant woman –no adverse effects on fetus.
  • TSH measurements are done 2 months after initiation of treatment.
importance to the anaesthetist
IMPORTANCE TO THE ANAESTHETIST
  • General– Weight gain ,obesity and its complications
slide9

Cardiovascular –

  • Earliest clinical manifestations
  • Hypodynamic cardiovascular system
  • Reduced – Heart Rate

Stroke Volume

Cardiac Output

Myocardial contractility

  • Increased – PVR , BP
  • Angina, Cardiac failure, Pericardial effusion, Conduction abnormalities.
  • Unresponsive Baroreceptor reflexes.
slide10

Pulmonary – reduced surfactant production.

  • Ventilatory drive in response to hypoxia and hypercarbia is reduced.
  • MBC and diffusion capacity are reduced.
  • Pleural effusion.
slide11

Blood – Secondary Anemia

  • Plasma volume is reduced and circulation rate is slow.
  • Coagulation abnormalities-Platelet dysfunction-reduced clotting factors
  • Adrenal Cortex – Atrophy with reduced Cortisol production.
  • Inappropriate ADH secretion- water retention and hyponatremia.
  • CNS – Lethargy, delayed tendon reflexes.
  • GIT – Delayed gastric emptying, constipation, Ileus and ascites.
  • Temperature regulation – increased susceptibility to cold.
  • Metabolism– Decrease in BMR.
  • Musculoskeletal System- abnormal response to peripheral nerve stimulator.
complications
COMPLICATIONS
  • Increased sensitivity to anaesthetic drugs
  • Secondary to reduced cardiac output,
  • Decreased blood volume,
  • Abnormal baroreceptor function
  • Decreased hepatic metabolism
  • Decreased renal excretion.
complication related to the airway
Complication related to the airway
  • Airway compromise
  • Secondary to myxedematous swelling of the upper airway
  • Macroglossia
  • Edematous vocal cords
  • Goiter
  • The risk of regurgitation and aspiration
  • Delayed gastric emptying time
symptoms
SYMPTOMS
  • Tiredness Weakness
  • Dry Skin Feeling cold
  • Hair loss Poor memory
  • Constipation Dyspnea
  • Hoarseness of voice Menorrhagia
  • Paresthesia
  • Weight gain with poor appetite
  • Difficulty in concentration
signs
SIGNS
  • Dry coarse skin
  • Cold peripheral extremities
  • Puffy face and feet
  • Macroglossia
  • Bradycardia
  • Hypertension
  • Delayed Tendon Reflexes.
management of anaesthesia
MANAGEMENT OF ANAESTHESIA
  • Sensitivity to depressant drugs.
  • Hypodynamic cardiovascular system characterized by decreased cardiac output due to reduction in Heart rate and Stroke Volume.
  • Slowed metabolism of drugs particularly opioids.
  • Unresponsive baroreceptor reflexes.
  • Decreased intravascular fluid volume
slide17

Impaired Ventilatory response to arterial hypoxemia and / or hypoxia.

  • Delayed gastric emptying.
  • Impaired clearance of free water resulting in hyponatremia.
  • Hypothermia.
  • Anemia.
  • Hypoglycemia.
  • Primary adrenal insufficiency.
pre operative assessment
PRE-OPERATIVE ASSESSMENT
  • Clinical assessment of the patient
  • Airway assessment
  • Hematological – as they are usually anemic
  • Coagulation Profile
  • Cardiovascular and pulmonary – Cardiomegaly and pleural effusion
  • ECG – low voltage complexes, ST , T wave abnormalities
  • Echo – for LV function and pericardial effusion
  • Lipid Profile
  • Thyroid Profile
premedication
Premedication
  • Judicious use of opioids - Ventilatory depression
  • Thyroxine, the morning dose can be given on the day of surgery.
  • Cortisol supplement is optional.
  • Perioperative Thyroid hormones in IHD or Valvular Heart Disease- Controversy.
anaesthesia regional or general
ANAESTHESIA - REGIONAL OR GENERAL
  • Regional anaesthesia is preferred if the location of the surgery permits
regional anaesthesia
Regional anaesthesia
  • Doses of local anaesthetic drugs may be reduced.
  • Metabolism of amide local anaesthetics is slow leads to development of systemic toxicity.
  • Land marks difficult to identify.
  • Hemodynamic side effects are exaggerated
general anaesthesia
General anaesthesia
  • Induction of anaesthesia-
  • Ketamine is the ideal induction agent theoretically
  • Recovery is inconsistent.
  • Barbiturates or benzodiazepines may produce sudden fall in BP.
  • Rapid sequence induction is preferred because of delayed gastric emptying.
  • Succinyl Choline is the preferred drug for intubation.
maintenance of anaesthesia
Maintenance of anaesthesia
  • Nitrous oxide with small doses of a short acting opioids and a non depolarizing muscle relaxant may be used.
  • Pancuronium is the relaxant of choice because of its mild sympathomimetic effects.
  • Volatile anaesthetics are not recommended because of
  • 1.Extreme sensitivity.
  • 2.Vasodilatation may cause a sudden fall in BP.
monitoring
Monitoring
  • Early recognition of hypotension, bradycardia, and hypothermia.
  • 1. Pulse oximetry
  • 2. ECG
  • 3. NIBP
  • 4. CVP
  • 5. Temperature
slide25

Hypotension can be treated with vasopressor (ephedrine 2.5-5mg).

  • Acute primary adrenal insufficiency
  • Hypotension persists despite treatment with intravenous fluids and sympathomimetic drugs.
  • Maintenance of body temperature
  • Increasing the temperature of operating room
  • Warming inhaled gases
  • Passing intravenous fluids through a blood warmer.
recovery
Recovery
  • Reversal of muscle relaxants
  • Acetyl cholinesterase inhibitor and an anti cholinergic agent.
  • Removal of ET tube-should be considered only
  • When the patient is awake
  • Maintaining airway
  • Normothermic
  • Adequate lung volumes
delayed recovery
DELAYED RECOVERY
  • Prolonged effects of anaesthetic drugs
  • Extreme sensitivity to the Ventilatory depressant effects of opioids.
postoperative period
Postoperative period
  • Prolonged post-operative observation is necessary
  • Continuous monitoring of temperature pulse, BP, CVP, and oxygen saturation is mandatory.
  • Maintaining the airway is also important.
myxedematous coma
Myxedematous Coma
  • Decompensated hypothyroidism-rare
  • Coma
  • Hypoventilation
  • Hypothermia
  • Bradycardia
  • Hypotension
  • Severe dilutional hyponatremia.
slide30

Predisposing Factors:

  • Infection, trauma, cold, CNS depressant drugs, and Surgery.
  • Treatment:
  • Medical emergency with a mortality rate of 15- 20 %
  • Immediate aggressive treatment.
  • Specific Measures:
  • L-Thyroxine (T4) 300-500µg bolus IV followed by a maintenance dose of 50µg / day.
  • T3 40µg bolus (slow infusion) followed by a maintenance dose of 10-20µg / day.
slide31

Supportive measures

  • Intravenous hydration with a glucose containing saline solution.
  • Maintenance of Temperature
  • Electrolyte imbalance correction.
  • Stabilization of the cardiac and pulmonary system.
  • Aggressive external warming is not recommended peripheral vasodilatation, hypotension and cardio vascular collapse
  • Hemodynamic status and hypothermia usually improve within 24 hrs.
  • I.V. hydrocortisone 100-300 mg / day is prescribed to treat possible adrenal insufficiency.
emergency surgery in severe hypothyroidism
EMERGENCY SURGERY IN SEVERE HYPOTHYROIDISM
  • Possibility of developing severe CVS instability intraoperatively and myxedematous coma in the post-operative period is high.
  • I.V. tri-iodothyronine 25-50µg bolus plus a continuous infusion is effective within 6 hours with a peak rise of BMR in 36-72 hrs.
  • Amrinone, an Inovasodilator may improve myocardial contractility since its mechanism of action does not depend on beta receptors.
  • Corticosteroid coverage.
conclusion
Conclusion
  • Well-controlled hypothyroidism do not present much difficulty
  • Sub clinical or untreated hypothyroidism presenting as an emergency, are at considerable risk.
  • Do proper preoperative assessment of the patients
  • Appropriate treatment to avoid complications in the perioperative phase.
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