#45 Obstetric Emergencies

On Critical Care Time we are no strangers to topics that make us uncomfortable. There may be no topic in the world of critical care more stress provoking than OB emergencies! Now… We didn’t say we are tackling this alone! Join us as we explore the wide world obstetrics in the ICU with Drs. Stephanie Levine and Adam Mora! Together we review the physiologic changes in pregnancy, unique considerations when it comes to general ICU management of the OB patient and then we delve into some OB cases where we tackle things like postpartum hemorrhage, cardiac arrest and more! Give us a listen and let us know what you think!

Special Guests:

Dr. Stephanie Levine – Professor of Medicine, Division of Pulmonary Diseases & Critical Care Medicine, UT Health - San Antonio. Former Program Director for the PCCM Fellowship and past President of CHEST (2019-2020).

Dr. Adam Mora – Intensivist at UT Southwestern, specializing in Obstetric and Transgender Critical Care.

Obstetrics in the ICU Infographic

Trends in Maternal Mortality

• Pregnancy is routine, however there are inherent risks.

• In the US, approximately 40,000-120,000 obstetric patients require care in the ICU each year. (This is roughly 1% of pregnancies)

  • Maternal Mortality Ratio (MMR) worldwide: 223 deaths per 100,000 pregnancies.

  • MMR in the US: 18 per 100,000, with significant disparities based on geography, race, and socioeconomic status.

    • There are significant (almost 10x) state-by-state variations in maternal mortality:

      • Mississippi (82.5 deaths per 100,000 births) and New Mexico (79.5 deaths per 100,000 births) had the highest maternal mortality rates. (2021 data)

      • Texas ranked 8th nationally at 22.9 per 100,000.

      • In contrast, California (9.7 per 100,000) and Massachusetts (17.4) had the lowest maternal mortality rates.

  • Because maternal risk increases with age and multi-parity, the lifetime risks are higher.

    • In the US the lifetime risk of dying from complications of pregnancy is 1 in 2700. This compares favorably to many developing countries; Somalia (1 in 25) or South Sudan (1 in 20), however many high income countries do far better than the US:

      • Spain 1:28,000

      • Japan 1:22,000

      • Italy 1:21,000

      • Australia 1:19,000

• Leading causes of maternal death in the US include:

  • Pulmonary Embolism

  • Hemorrhage

  • Hypertension

  • Infection

  • Cardiomyopathy

• Recently, maternal mortality has risen due to effects of the the COVID-19 pandemic and recent abortion bans on maternal outcomes.

Normal Physiologic Changes in Pregnancy

Cardiovascular System:

• Blood volume increases by 30-50%, hemoglobin also increases but to a lesser extent, leading to physiologic anemia.

• Several hemodynamic changes occur:

• Blood pressure increases (MAPs >90 mmHg) with gestational age

• HR increases steadily from 60 to 90 bpm

• SV increases until about 32 weeks then actually decreases.

• SVR decreases to <1000 dyn/cm/sec, then rapidly normalized to 1200 post-partum

• Baby is perfused by flow not pressure (hence high flow state in pregnancy, with inconsistent effect on BP)

• Supine positioning in late pregnancy can impair venous return and reduce cardiac output. This is why lateral positioning is so important. Effects of supine positioning in third trimester

  • Change in cardiac output by position (Vorys et al, Am J Obster Gyn 1961)

  • Supine trendelenberg -18%

  • Left side trendelenberg +13%

Respiratory System:

• Increased estrogen leads to increased minute ventilation, resulting to lower PaCO2 (40 → 30 mmHg).

• Functional residual capacity (FRC) and residual volume (RV) decrease by 20%.

  • Diaphragmatic Elevation: The enlarging uterus elevates the diaphragm, which can affect lung capacity and predispose to respiratory distress.

    • Specifically, this is mostly a drop in RV and FRC (20%) with VC essentially unchanged

• Because minute ventilation increases by 30-50% the PaCO2 drops 40 → 30 mmHg

  • Bicarb changes to compensate for pH

  • PaO2 increases slightly…

  • Normal ABG in pregnancy is: pH 7.42 / paO2 103/ pCO2 30 / HCO3 21 (this reflects a slight respiratory alkalosis with metabolic compensation)

  • When ventilating the pregnant woman consider slightly higher tidal volumes (remember that normal TV in pregnancy is 678 ml)

Hematologic System:

• Pregnancy is a pro-thrombotic state, increasing the risk for DVT and pulmonary embolism.

Renal & Endocrine Systems:

• Increased renal blood flow and glomerular filtration rate.

• Changes in insulin metabolism, affecting drug clearance.

• Hypercoagulability and fluid shifts impact emergency management.

  • Understanding fluid shifts in pregnancy

    • Q = k(deltaP) - r(deltaPi)

    • Higher pressure has more driving force and due to volume expansion during pregnancy, the colloid osmotic pressure falls (dilution)

    • Interstitial fluid contains more protein as well (from shift).

Drug metabolism in pregnancy

• Volume of distribution increases → potential need to adjust AED dose

• Change in insulin requirements → potential DKA risk

  • Risk for Euglycemia DKA

• GERD and reflux → Tums use. Hypercalcemia due to overuse

• Metabolsim changes

  • CYP3A is increased, hence more of certain drugs is needed (midazolam)

  • CYP2D6 is highly variable, so the dose of metoprolol can be highly variable

Case 1: Pregnancy & ARDS

• ARDS is rare in pregnancy. Most cases can be managed with non-invasive ventilation, however specialized care at an experienced center is important.

• Increased risk for airway edema and failed intubation (8x higher in pregnancy).

• How is pregnant ARDS different?

  → expect higher plateau pressure

  → consider measuring pressures after intubation (e.g. esophageal balloon monitoring)

  → not the typical oxygenation goals (SpO2 > 95%, and monitoring fetal heart rate)

  → can do prone positioning, neuromuscular blockade, ECMO

  → remember the eucapnea of pregnancy as opposed to the typical ABG

  → check ABGs more frequently in this population

  → slightly liberal fluid status; a post partum diuresis (3-5 liters) is normal

• Vaginal delivery preferable in pregnancy

• ECMO in ARDS due to late pregnancy

  → well described in H1N1 and COVID

  → potential need to convert from VV-ECMO to VA-ECMO (for example peri-partum cardiomyopathy)

Case 2: Postpartum Hemorrhage (PPH)

• Common causes: Uterine atony, retained placenta, lacerations.

• Initial management: Uterine massage, fluids, uterotonics.

• Criteria for blood transfusion and escalation of care. Monitor for development of DIC.

• Importance of team-based resuscitation.

Case 3: Amniotic Fluid Embolism (AFE)

• Amniotic Fluid Embolism (AFE) is rare (3 per 100,000) and catastrophic life-threatening emergency that is unique to pregnancy.

  • Mortality used to be over 85%. Mortality has improved with interventions like ECMO, however it remains high (~60%)

• Hallmarks of AFE: Acute respiratory failure, cardiovascular collapse, coagulopathy, often with altered mental status.

  • Differentiators include RAPID onset, the presence of altered mental status, and coagulopathy.

• Differential: PE, high spinal epidural, sepsis.

  • PE in pregnancy is different; often in the deep pelvic veins often released during contractions or delivery.

• Immediate interventions:

  • Activate MTP, manage airway, place large volume access, and prepare for ECMO (likely VA ECMO)

  • Prepare for massive transfusion protocol

  • Consider pulmonary vasodilators

  • These patients are at risk for devastating neurological injury and ARDS

Case 4: HELLP Syndrome

• Hemolysis, Elevated Liver Enzymes, Low Platelets (HELLP) is a Microangiopathic hemolytic anemia

• Differentials: Acute hepatitis, Acute fatty liver of pregnancy, TTP, severe preeclampsia.

• Management:

  • Best management is immediate delivery → depending on stage and viability

  • Blood pressure control (and seizure prevention) with magnesium and other agents

  • Lab abnormalities should recover quickly

  • 20-25% of case can develop in the post-partum period

Case 5: Cardiac Arrest in Pregnancy

• There are several modifications to the standard ACLS algorithm: Chest compressions moved up, left lateral tilt, no IV access below waist.

  • Airway modifications

  • Chest compressions moved up in the chest

  • Turn 15 degrees to the left side

  • No IV access below the waist

  • Defib is unchanged (but remove fetal or uterine monitors)

  • Can reverse excess magnesium with calcium

• Emergency perimortem cesarean section if no ROSC within 5 minutes.

  • Fetal survivability is about 70% if under 5 minutes

• ECMO as a consideration for cardiac support.

• Three-team approach: Code team, surgical team, NICU team.

• This is a high acuity low occurence (HALO) event. Simulation can be very helpful in preparing.

  • 3 teams - code team, surgical team --> ECMO team, NICU team

  • Managing family

  • Dynamic situation

  • Resuscitation c-section manikin

ACLS algorithm in pregnacy. Source: AHA

Final Takeaways & Expert Insights:

• Not only are you caring for 2 (or more) patients, but you need to coordinate between multiple teams. Effective communication between OB, MFM, and intensivists is critical.

• Recognizing and acting on early warning signs of decompensation in pregnant patients.

• Multidisciplinary teamwork and simulation-based training improve outcomes in OB-CCM.

• Clinical Trials Discussed

• Related Episodes