Cutting it Close: One Decision, Two Lives

Hematological & Hemodynamic Changes:

1) Plasma volume expands 40% to 50% above normal range by 30 to 34 weeks gestation. The average plasma volume in a normal 70 kg adult is approximately 3.5 liters.[1-4]

2) Red blood cell production also increases during pregnancy (though to a lesser extent than plasma volume expansion), reaching a maximum of a 25% increase by 34 weeks gestation. Given that the plasma volume expansion is greater than the total increase in red blood cell volume, there is a dilutional anemia that occurs, known as "physiologic anemia of pregnancy."[5] 

3) Cardiac output increases from 5 to 7 L/min during pregnancy and peaks during the late second trimester, before remaining relatively constant until delivery.[1-3,6-8] This is due to three major changes. The first is increased preload from the increase in blood volume, as mentioned above. The second is reduced afterload from loss of systemic vascular resistance. This is attributed to the high-flow, low-resistance circuit in the uteroplacental circulation and vasodilatation from decreased vascular responsiveness to the effects of angiotensin II and norepinephrine.[9-12] The third is increased heart rate: median of 91/min at 34 weeks gestation with the upper limit of normal being 115/min at rest.[13]

Consequences of Change:

1) The reduction in blood viscosity reduces resistance to flow, facilitates placental perfusion, and lowers myocardial O2 demand. Additionally, the increased cardiac output ensures appropriate uteroplacental flow for fetal growth, while the large increase in total intravascular volume provides reserve against normal blood loss during delivery.

2) The emergency physician must be vigilant in the setting of trauma as the state of hypervolemia and resulting hemodilution can mask significant underlying blood loss. Clinical signs of maternal shock only manifest after 40% loss of blood volume. Therefore, aggressive volume resuscitation is encouraged regardless of blood pressure. Furthermore, in late pregnancy, there is the added insult of inferior vena cava compression by the enlarged uterus that reduces preload.[14-15]

Figure 1: Aortocaval compression due to the gravid uterus in supine than lateral positions.[16]

1) If intubation is necessary, use an endotracheal tube one size smaller as there is physiologic narrowing of the airway during pregnancy.[16]

2) Always provide supplemental oxygen regardless of pulse oximetry readings as pregnant patients are predisposed to precipitous falls in PaO2 during apnea (during RSI or cardiac arrest).[16] This is due to reduced functional residual capacity secondary to an enlarged uterus elevating the diaphragm.[17] Additionally, increased metabolic demand from the growing fetus increases oxygen consumption. Therefore, desaturation events occur more rapidly. Pre-oxygenation provides an added margin of safety if efforts at establishing an airway become prolonged. Also, remember that pre-oxygenation can also be thought of as denitrogenation – highlighting the fact that it is the nitrogen within the lungs that is being displaced by a high inspired oxygen concentration.[17]

3) Always perform uterine displacement by manually moving the uterus to the patient’s left to relieve IVC compression. This improves preload and can increase cardiac output by 25%.[18]

Figure 2: Lateral displacement of the uterus.[16]

1) The primary goal of PCS is improvement in maternal outcomes, not fetal outcomes. PCS decreases uterine compression on the IVC, increasing venous return and diastolic filling pressure. After PCS, there is also improved oxygenation and ventilation, as the diaphragm expands downward into the abdomen.[19-21]

2) The traditional teaching (and American College of Obstetrics and Gynecology recommendation) is that PCS be performed within the first four minutes of cardiac arrest if the fetus is > 24 weeks gestation and the fetus delivered by five minutes. The fetus is generally viable at 24 weeks gestation and there are worse fetal neurologic outcomes and survival rates after four minutes of maternal arrest.[19-21] 

3) Twenty-four weeks gestation is not a hard and fast rule, however. In the absence of definitive knowledge of the gestational age, which will often be the case in the ED, it is reasonable to consider viability at 20 weeks gestation. Therefore, a good rule of thumb is if you note a uterus at or above the umbilicus, it is reasonable to consider PCS to improve maternal hemodynamics [18]. Of note, PCS can still be performed after the 5-minute mark to improve maternal hemodynamics.[19-21]

Figure 3: Fundal height based on gestational age.[22]

Step 0: Prepare

1) Allocate roles: There should be two main teams. One team is 100% dedicated to continued, high-quality, CPR at all times without cessation, while the second team is in charge of the PCS procedure. Call for specialists (obstetricians and neonatologists) but do not wait for them to start the procedure.[23-25]

2) Tools: It is unlikely the ED will have a PCS kit (congrats if you do). A thoracotomy tray will do just fine. It has retractors, scissors, and clamps. These, along with a #10 blade scalpel, wall suction, and abdominal packs will be sufficient to perform a PCS. Remember to bring over neonatal resuscitation gear/bed.[23-25]  Neonatal resuscitation is beyond the scope of this article and will not be covered. Luckily though, we have you covered with this article written by one of our graduates, Dr. Zonnoor: Baby Blues: Basics of Neonatal Resuscitation

3) PPE: Gown up. It's going to be messy 

4) Breathe: Before you start, remember the Navy Seal mantra: Slow is Smooth, Smooth is fast. 

Step 1: Get into the Abdomen 

1) No time for skin prep. With a scalpel, perform a midline, vertical incision from the xiphoid process to the pubic symphysis, diverting around the umbilicus. Use scissors and hands to dissect through all the abdominal layers to reach the parietal peritoneal layer. Cut through the peritoneum vertically (ideally with scissors but can use a scalpel for the initial opening).[23-25]

2) Remember to use retractors to stretch the abdominal wall laterally as you obtain access to the abdomen.

Figure 4: Vertical midline incision of anterolateral abdominal wall.[26]

Figure 5: External to internal layers of the anterolateral abdominal wall.[27]

Step 2: Get into the Uterus

1) Once in the abdomen, you'll see the uterus. With several shallow scalpel, passes, you will make a vertical incision through the anterior uterine wall. Avoid the bladder, lateral uterine vessels, and the fetus to the best of your ability. Do not waste time catheterizing the bladder for these patients.[23-25]

2) To help make your life easier, create a large incision. This will help with step 3. If the placenta is in the way, you will have to cut through it. Remember to have suction ready (amniotic fluid coming your way).

Figure 6: Vertical Hysterotomy [28]

Step 3: Get the Neonate Out

1) Insert your hand into the uterus and attempt to find the occiput to gently deliver the head. The body should follow but can be assisted by placing a hand underneath the posterior shoulder to deliver the anterior shoulder first. You can have an assistant apply external fundal pressure.[23-25]

Step 4: Get the Placenta Out

1) Once the neonate is delivered, clamp the cord in two locations. The clamp closest to the infant should be placed at least 6-8 cm from the infant (allows for enough leftover umbilical cord if umbilical vein catheterization is required) and the second clamp should be placed 2 to 3 cm from the first. Cut between the two clamps and hand the neonate to the neonatal resuscitation team. Scoop the placenta out with one hand while applying gentle traction on the remaining cord with another. Ensure all of the placenta is removed by sweeping across the internal surface of the uterus.[23-25]

Step 5: Closure

1) The open uterus and abdomen should be packed to prevent further bleeding and oxytocin should be administered. ACLS/ATLS should be continued on the mother until ROSC is achieved or efforts are deemed futile. If ROSC is achieved, further closure should be completed in the OR.[23-25]

2) Remember that neonatal resuscitation must occur simultaneously. 

Extra: Instructional Videos and Models

1) Follow this Link: Perimortem C-Section Instructional Video for an instructional PCS video done by the University of Maryland’s Emergency Medicine Department

2) How can I practice, you ask? Here are two links on how to create simulation models:

An Inexpensive, High-Fidelity Resuscitative Hysterotomy (RH) Model

An inexpensive and novel model for perimortem cesarean section