Considerations for Pregnant Patients
In addition to the above considerations, the physiological changes in pregnancy require another layer of awareness. Understanding and managing the risks to both mother and the unborn child are critical, even in the very early stages of the first trimester, for the prevention of harm.
Every year in the United States, about 80,000, or 1 in 50, pregnant women require non-obstetric surgery, with many surgeries taking place in an outpatient setting. According to the American Society of Anesthesiologists' statement on non-obstetric surgery in pregnancy, no currently used anesthetic agents have been linked to any teratogenic effects in humans when used at standard concentrations. However, there are other factors that must be considered to maximize patient safety.
Oxygen levels. The physiological changes of pregnancy affect more than just the reproductive system. Changes in the airways of pregnant women make adequate pre-oxygenation important, and the oxygen levels of pregnant patients require close monitoring throughout surgery.
A result of weight gain in pregnancy is that capillaries become engorged and can lead to upper airway edema and decreased internal tracheal diameter. In the third trimester particularly, a weight shift occurs that prevents the diaphragm from fully expanding, which can affect breathing. Because intubation failure rates for pregnant patients (1:280) are 8 times higher than those for non-pregnant patients (1:2,240), it is important for anesthesia to choose an appropriately sized endotracheal tube.1
Pregnant patients also have decreased functional residual capacity, which increases the risk of oxygen desaturation. In an article in Outpatient Surgery, Paloma Toleda, MD, MPH, an anesthesiologist affiliated with Northwestern University, explains the changes: “Though they consume more oxygen, their PaO2 levels stay largely unchanged. However, due to an increase in alveolar ventilation, they have an uncompensated respiratory alkalosis, with PaCO2 values ranging between 28 and 32 mm Hg. This relative hypocapnea is important to maintain during surgery, especially laparoscopic procedures, because maternal hypercapnea can result in fetal acidosis.”
Most pregnant women won't know to ask about how their oxygen levels will be monitored during the procedure, but it's an important question.
Pain management. Many outpatient surgeries require some form of pain management after the procedure. With an estimated 600,000 to 2 million patient-controlled analgesia (PCA) errors each year, pregnant women requiring PCA for post-surgical pain should be closely monitored for early respiratory depression.
Good news for patients. Obstetricians tend to be very protective of their patients, and there is an expectation that anesthesiologists or anesthesia care providers be credentialed and competent in providing anesthesia to pregnant patients. The best advice for a pregnant woman who is facing a required outpatient surgery is to ask their OB which anesthesiologists they recommend.
Duncan PG ,Pope WD,Cohen MM, Greer N. Fetal risk of anesthesia and surgery during pregnancy. Anesthesiology. 1986;64:790-794.
Radfar F. Laparoscopic surgery in pregnancy: precautions and complications. Available at: http://www.laparoscopyhospital.com/laparoscopic_surgery_in_pregnancy_precautions_and_complications.html. Accessed January 21, 2015.
Stepp K, Falcone T. Laparoscopy in the second trimester of pregnancy. Obstet Gynecol Clin North Am. 2004;31:485-496.
Toledo P. Anesthesia alert: anesthesia for the pregnant patient. Outpatient Surgery. July 2013. Available at: http://www.outpatientsurgery.net/surgical-services/general-anesthesia/anesthesia-alert-anesthesia-for-the-pregnant-patient--07-13. Accessed January 21, 2015.