Intubating a pregnant woman is intimidating because you have two patients to consider. Physiologic changes in pregnancy can affect intubation so it is important to plan ahead.
Both ventilation and acid-base status change during pregnancy. As progesterone rises, there is an increase in tidal volume, which results in maternal respiratory alkalosis. This creates a gas gradient to allow for the transfer of CO2 from the fetus to the mom. This maternal hypocarbia causes uteroplacental vasoconstriction, which can cause fetal hypoperfusion and hypoxia. This creates a very delicate acid-base balance that is exacerbated by increased fetal oxygen consumption and CO2 production in the third trimester. In addition, the diaphragm is pushed up by the gravid uterus reducing the mother's functional residual capacity by 10-25%. As a result of these factors, pregnant patients have a shorter safe apnea time and can desaturate quickly.
Progesterone also decreases the tone of the lower esophageal sphincter. Combined with increased intraabdominal pressure from the gravid uterus, pregnant patients are at higher risk for aspiration. For these reasons, you should be careful with bagging and consider intubating in a semi-upright position. This position also has the benefit of taking some pressure off of the patient's chest and IVC.
Anticipate a difficult airway in pregnant patients. Failed intubation is 8x more likely than in the general population. Human placental growth hormone secreted in pregnancy increases blood flow to the upper airways. This results in edema and hyperemia of the airway, causing it to be smaller and more friable. For this reason, you should prepare a smaller caliber ETT. Rocuronium and succinylcholine have been studied with similar efficacy. Induction agents therefore depend on patient specific factors.
TLDR: 1. preoxygenate well due to shorter safe apnea time. 2. Consider a smaller ETT for a narrower and more friable airway. 3. Limit aspiration risks by decreasing bagging if possible 4. consider intubating patients in a semi-upright position.
Thanks for reading!
Ariella
References:
https://rebelem.com/respiratory-failure-and-airway-management-in-the-pregnant-patient/
https://www.nuemblog.com/blog/intubating-the-pregnant-patient
https://www.uptodate.com/contents/airway-management-for-the-pregnant-patient