Physiological changes during pregnancy - NYSORA

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Physiological changes during pregnancy

Learning objectives

  • Describe the major physiological changes during pregnancy
  • Describe the anesthetic implications of the physiological changes during pregnancy


  • Every major organ system is affected by substantial physiological changes during pregnancy
  • Many of these changes significantly affect the pharmacokinetic and pharmacodynamic properties of different therapeutic agents, including anesthetics
  • Understanding these changes and their effects is essential to optimize therapy and anesthesia in obstetric patients

Physiological changes

physiological changes during pregnancy, fetus, hormonal, placenta, uterus, blood cells, clotting factors, fibrolytic, iron, anemia, tachycardia, cardiac output, heart rate, stroke volume, diaphragm, functional reserve capacity, apnea, dyspnea, hyperventilation, nausea, reflux, cdf pressure, epidural veins, mac, la volume, mv, tv, rr, paco2, pao2, frc, co, cv, hr, svr, left ventricular hypertrophy, regurgitant murmurs, gfr, urea, creatinine, uti, bone loss, lordosis

CSF, cerebrospinal fluid; MAC, minimum alveolar concentration; LA, local anesthetic; MV, minute ventilation; TV, tidal volume; RR, respiratory rate; PaCO2, partial pressure of carbon dioxide; PaO2, partial pressure of oxygen; FRC, functional residual capacity; CO, cardiac output; SV, stroke volume; HR, heart rate; SVR, systemic vascular resistance; GFR, glomerular filtration rate; UTI, urinary tract infection

Anesthetic implications

CardiovascularUterine perfusion not autoregulated
Hypotension common under regional and general anesthesia
Supine hypotensive syndrome requires left lateral tilt
RespiratoryPotential hypoxemia in the supine and Trendelenburg positions
Breathing more diaphragmatic than thoracic
Difficult laryngoscopy and intubation; bleeding during attempts
Central nervous systemMore extensive local anesthetic spread
HematologicalDilutional anemia
Thromboembolic complications
Edema, decreased protein binding of drugs
GastrointestinalIncreased aspiration risk
Antacid prophylaxis, RSI after 18 weeks gestation
RenalNormal urea and creatinine may mask impaired renal function
Glycosuria and proteinuria

Suggested reading

  • Costantine M. Physiologic and pharmacokinetic changes in pregnancy. Frontiers in Pharmacology. 2014;5.
  • Nejdlova M, Johnson T. Anaesthesia for non-obstetric procedures during pregnancy. Continuing Education in Anaesthesia Critical Care & Pain. 2012;12(4):203-6.

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