The overall pelvic anatomy and orientation of the pelvic organs is similar to the nongravid state (see Chapter 35 Emergency Hysterectomy) with the following exceptions:

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  Prior to the 12th week of pregnancy, the uterus is protected by the bony pelvis, but as it grows out of the pelvis, it becomes more susceptible to injury. By 20 weeks, the fundus reaches the umbilicus, and gestational age may be estimated by fundal height. The number of centimeters above the pubic symphysis corresponds to the estimated gestational age in weeks.

  
  
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  Physiologic changes in blood flow that result in diffuse engorgement of the uterine, ovarian, and salpingeal vasculature. Gravid or postpartum hysterectomies are more difficult and result in higher blood loss than when performed in the nongravid setting. Damage to this vasculature can quickly lead to exanguination.

Cardiac output increases by 30–50% due to increased stroke volume and heart rate.

After 20 weeks, the pressure of the gravid uterus on the inferior vena cava (IVC) may limit cardiac output. At term, the IVC becomes completely occluded in the supine position.

Unless contraindicated, in advanced pregnancy the patient should be positioned in left lateral decubitus to reduce pressure on the IVC and improve venous return to the heart. A wedge may also be placed under the right hip.

Blood pressure decreases due to decreased systemic vascular resistance.

Maternal oxygen reserve is decreased, rendering pregnant patients more susceptible to hypoxia, hypercapnia, and respiratory acidosis.

Blood volume increases and the maternal blood pressure may be maintained despite significant blood loss.

Be aware of both increased risk of VTE and DIC in pregnancy.

Trauma is the leading cause of nonobstetrical maternal death. Blunt trauma is commonly associated with placental abruption, while penetrating trauma is more likely to cause direct fetal injury.

On arrival, in advanced pregnancy, position the patient supine with a left lateral tilt. Supplemental oxygen should be given at 10L via face mask to increase fetal oxygenation and to keep oxygen saturations above 95%.

Aggressively replete fluids and replace volume prior to using vasopressors, as these may reduce uterine blood flow.

Assessment of gestational age (GA) is paramount to decision-making. This can be estimated via:

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  Most reliable method: calculation from patient-provided estimated due date (EDD), if available, especially if this date was confirmed by a first trimester ultrasound (ask the patient).

  
  
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  Calculation from reported LMP may be helpful to get a general sense of GA, but is often imprecise.

  
  

  
  

  

  
  

  
  

  Figure 34.2 Appropriate biparietal diameter measurement from outer to inner table of the skull.

  
  
  
  
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  Ultrasonography: Perform a quick measurement of the biparetal diameter (BPD), measured from the outer table of the bony calvarium on one side to the inner calvarium on the opposite side. The image should be taken at an axial plane at the level of the thalami and cavum septum pellucidum and is easiest to find in a third trimester patient by placing the probe just above the pubic symphysis in a transverse orientation.

  
  
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  If no ultrasound is available, a measurement of fundal height may suffice to corroborate the dating the patient has given. As a rule of thumb, if the fundus is 2–4 fingerbreadths above the umbilicus, the pregnancy is likely over 20 weeks and likely to be viable.

Maternal and fetal well-being are both at stake and must be considered.

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  In the setting of cardiopulmonary arrest, a perimortem emergent cesarean section may be performed (see section on perimortem cesarean below).

  
  
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  Maternal benefit is prioritized since fetal survival, particularly prior to viability (22–23 weeks, depending on the capabilities of proximal neonatal ICU facilities), is inextricably linked to maternal well-being.

  
  
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  If previable, fetal heart tones should be assessed via Doppler or ultrasound; if viable, a fetal heart rate monitor should be used (normal FHR 110–160 bpm). Ensure fetal and maternal heart rates are not confused.

  
  
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  In general, emergency cesarean delivery is indicated:

  
  
  
  
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    For fetal benefit due to impending maternal death or fetal heart rate tracing abnormalities, and only after the age of viability

    
    
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    For maternal benefit in the setting of cardiopulmonary arrest, not responsive to resuscitative efforts, to decompress the IVC if the uterine fundus is above the umbilicus

  
  

Rh/ Kleihauer-Betke (KB) test and alloimmunization prevention:

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  Fetomaternal bleeding occurs frequently, and can result in fetal anemia and/or maternal alloimmunization.

  
  
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  Unless maternal blood is known to be Rh+, rho gam should be given 300 mcg IM in any incidence of trauma to prevent alloimmunization.

  
  
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  The KB test can be sent to measure the percent of fetal hemoglobin in maternal blood and is used to estimate if additional rho gam is needed.

Ten blade scalpel

Monopolar electrocautery device

Curved Mayo and Metzenbaum scissors

Bandage scissors

Russian forceps

Retractors:

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  Balfour (aka bladder blade) retractor

  
  
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  Richardson retractor

  
  
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  Goulet retractors

Suture: 0-vicryl or 0-chromic suture for hysterotomy closure

Clamps:

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  Ring forceps

  
  
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  Kocher clamps

  
  
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  Pean clamp for umbilical cord