The ABCs of the Pregnant Trauma Patient.

“Life is tough enough without having someone kick you from the inside.”—Rita Rudner

Thankfully, these teeny kicks don’t cause trauma!!

Critical illness, including trauma, actually affects less than 1% of all pregnancies in the US.  However, this patient population can be exceedingly complicated due to the plethora of physiologic alterations in pregnancy.  It is important to know these changes and recognized their related clinical implications.

Let’s discuss the basic ABCs of ATLS, written in a stems/no flowers method of information delivery for all my attention-deficit EM pals and me!

A- AIRWAY

Changes in pregnancy.

-Estrogen has a direct effect on nasal and upper airway mucosa, causing hyperemia and friability of these tissues.

-The airways are considerably narrow due to edema and swelling of the aretynoids.

-Of note, fortunately, airway resistance doesn’t change significantly during pregnancy.

Clinical implications.

All of the above make intubations in pregnant patients difficult!

-RSI medications are category B/C, no changes in doses from nonpregnant patients are recommended.

-Preoxygnation is very hard to achieve due to increased oxygen consumption and decreased functional residual capacity. Apnea time is much less forgiving in pregnancy—pregnant females desaturate faster than nonpregnant cohorts.  Preoxygenation with 100% oxygen is recommended as long as possible before intubation, so if you are even thinking about intubation, start 100% oxygenation right away.

-Smaller size endotracheal tubes required because of the swelling of the aretynoid region of the vocal cords (tubes of 0.5-1.0 size smaller than would be used, with smaller tubes as back up are reocommended).  Remember that there is increased mucosal edema and friability—repeat attempts are not ideal.  The most experienced person in the room should intubate and the glidescope should be readily accessible.

B- BREATHING

Changes in pregnancy.

-Minute ventilation increases in pregnancy.  Remember that minute ventilation is respiratory rate x tidal volume.  The respiratory rate doesn’t change much in pregnancy, however, the tidal volume increases by 40-50%.  This is to compensate for increased metabolism—increased oxygen consumption and increased carbon dioxide production.   This causes a chronic, partially compensated respiratory alkalosis (partially compensated because the kidney actually increases bicarbonate excretion during this time).

-The diaphragm is displaced upwards into thorax, causing reduced lung volumes. Total lung capacity is reduced by 5%. Functional residual capacity (air in lungs at the end of resting expiration) is reduced by 20%. Of note, compliance of the lung and exchange of gas across alveoli remain unchanged.

-Oxygenation is positional in 2^nd and 3^rd trimesters, pO2 has shown to drop to 90 in supine pregnant patients, increases to 103-106 in the upright position.

Clinical implications.

-Chest tubes should be placed 1-2 intercostal spaces higher due to diaphragmatic displacement.  Remember that a 4-5cm upward displacement of the diaphragm actually happens early in pregnancy and is not due to the uterus pushing it upward!

-There is an increased risk of aspiration due to progesterone-induced lower esophageal sphincter relaxation, delayed gastric emptying and uterine pressure on intestinal and stomach contents.

-Chest X-Ray readings: there is mild heart enlargement, but otherwise comparable to interpret as in nonpregnant patients.

-There is not a lot of information on recommended ventilator settings.  Titration of vent settings to ideal oxygenation is necessary on a case-by-case basis.  Generally PEEP should be as low as possible in pregnant patients because increased intrathoracic pressures can further decrease venous return.  Keep in mind the ABG differences in a pregnant patient due to chronic respiratory alkalosis; normal ABG values in a pregnant patient: pH 7.4-7.47, pCO2 27-34 mmHg, bicarbonate level 15-20 mEq/L.

C- CIRCULATION

Changes in pregnancy.

-The fetus relies on mother’s circulation for oxygenation and nutrition. By the third semester, 20-25% of cardiac output is to fetus.  This is physiologically a shunt that is created, and to compensate, maternal cardiac output (stroke volume x heart rate) increases to more than 50% of prepregnancy values.  Stroke volume increases due to improved cardiac contractility and dilation of all 4 chambers thereby increasing ventricular filling.  Heart rate increases by 10-20 beats per minute above baseline, sometimes causing a resting tachycardia that is considered “normal” in pregnancy.

-There is a direct progesterone-mediated decrease in blood pressure—both systolic and diastolic—by 10-15 mmHg during second trimester.

-Due to increased plasma volume, there is a relative anemia in pregnancy.

Clinical implications.

– Due to increased cardiac output, pregnant patients can hemorrhage quite rapidly.  It’s important to remember early placement of intravenous access and activation of blood products for transfusion.

-To ensure uterine perfusion, keep systolic >100 or more than 80% of patient’s baseline.

-Position is SO important! Pregnant patients should be positioned (whenever possible) in complete left lateral decubitus position to allow for optimal blood return to the heart and reverse compression of abdominal vasculature by the uterus. If this is not possible, place a wedge of sheets underneath the right hip creating 15-30 degrees tilt or manually displace uterus to the patient’s left side (this has proven to be superior to the right hip wedge approach in noncritical caesarian patients).

-Central lines should be placed above the level of the diaphragm, as compression of femoral and pelvic veins may prevent medications and fluids from entering the arterial circulation.  Also, one should avoid femoral catheters due to an increased risk of DVTs.  Pregnancy induces a hypercoagulable state due to higher fibrinogen levels.

And…badeep, badeep, that’s all folks.

References:

Gei, AF. Suarez, VR. Respiratory Emergencies During Pregnancy.  www.mhprofessional.com. Accessed May 1, 2013.

Mallemat, H.  Supportive Management of Critical Illness in the Pregnant Patient.  EM Critical Care. 2012(2):3. 1-16.

Smith, KA.  Bryce S.  Trauma in the Pregnant Patient:  An Evidenced- Based Approach to Management. Emergency Medicine Practice.  2013(14):4. 1-20.

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