Pregnancy

Period of time during which a child develops inside a woman. Pregnancy is:

• Normally 37-42 weeks
• Divided into trimesters
  • First trimester
    0-12 weeks. The first trimester:
    • Has the highest rate of miscarriage
  • Second trimester
    13-28 weeks. The second trimester:
    • Foetal movement begins
  • Third trimester
    29-40 weeks.

Physiology of Pregnancy

Physiological changes and their implications can be classified by system:

• Respiratory
  • MV
    ↑; ↑ Uptake of volatile agents.
  • FRC
    ↓; ↓ Safe apnoea time.
  • RV
    ↓; ↑ Atelectasis and shunt.
  • VO₂
    ↑; ↓ Safe apnoea time.
• CVS
  • Cardiac output
    ↑ Up to 40%; ↓ physiological reserve.
  • Heart rate
    ↑ by 15-20 bpm; ↓ reserve and coronary perfusion time.
  • SVR
    ↓.
  • BP
    ↓.
  • Volume
    ↑ Circulating volume.
  • Other
    Aortocaval compression by uterus reduces CO in supine position; can be reduced by placing tilt under right hip.
• Endocrine
  
  • Insulin
    ↑ Production and resistance; gestational diabetes.
  • Thyroid hormones
    ↑; Incidence of hyperthyroidism.
• Renal
  • Renal blood flow
    ↑; Natriuresis.
  • Bladder emptying
    ↓; ↑ UTI.
• GIT
  • Bowel
    Displaced into upper abdomen; ↑ reflux risk.
• Hepatic
  
  • Plasma cholinesterase
    ↓; ↑ Duration of suxamethonium.
  • Albumin
    ↓; Altered pharmacokinetics via change in protein binding, ↑ peripheral oedema.
  • Biliary
    ↓ Gallbladder contractility; biliary stasis.
• Haematological
  • Haemoglobin
    ↓ Due to dilution; may be confused with haemorrhage.
  • White Cell Count
    ↑; May mimic infection.
  • Coagulation factors
    ↑; ↑ Thrombosis risk.
• Immunological
  • Cell mediated immunity
    ↓; ↑ Viral infections.

Management

Principles of managing the pregnant patient in critical care.

Resuscitation:

• Modifications of ALS are relevant after ~20 weeks
  • Relieve aortocaval compression
    • Wedge
    • Manual uterine displacement
      Results in easier CPR as the patient is not tilted.
  • Chest compressions slightly above the centre of the sternum
  • Notably, no change to defibrillation or drug doses
  • Resuscitative hysterotomy (perimortem caesarian section) should be initiated at 4 minutes
    Completed within 1 minute of commencing.

Specific Therapy:

• Early obstetric opinion
  • Examination
  • CTG
  • Timing of delivery
• Physical
  • Breast nursing care
    ↓ Risk of mastitis.

Supportive care:

• H
  • Thromboprophylaxis

---

References

1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.