Physiological Considerations of Pregnancy

 

Anesthetic Considerations 

  • Airway 

    • Potentially more difficult laryngoscopy & intubation due to increased tissue edema & friability

    • ↑ Risk reflux & aspiration, especially after 20 weeks GA & even more during labor 

  • Respiratory 

    • ↑ minute ventilation (50%), ↑ oxygen consumption (20%)

    • ↓ functional residual capacity (20%), at risk of rapid desaturation 

    • PaCO2 ~30 

  • Cardiovascular 

    • Supine hypotension can occur due to aorto-caval compression 

    • ↑ Cardiac output, reaching a 40–50% ↑ by the third trimester. The largest increase occurs immediately after delivery.  HR ↑ by 15-25% 

    • ↓ Blood pressure due to ↑ in SVR 

  • Hematological 

    • Physiologic anemia of pregnancy due to  disproportionate ↑ in plasma volume (45% at term) compared with erythrocyte volume (20% at term)

    • Platelets usually normal unless gestational thrombocytopenia or other platelet disorders 

 

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