The etiology of cardiac arrest in pregnant patients is different from that in nonpregnant patients and includes pulmonary embolism, amniotic fluid embolism, eclampsia, drug toxicity (e.g., magnesium sulfate or epidural anesthetics), cardiomyopathy, aortic dissection, trauma, and hemorrhage. As always, one should address the potential underlying etiology as well as the cardiovascular collapse.
Cardiopulmonary arrest in a pregnant patient must be considered under two scenarios: prior to fetal viability and after fetal viability. The accepted age of fetal viability may vary among institutions, but 24 to 26 weeks is generally considered the age of viability. The uterine fundus is palpable at the umbilicus at 20 weeks. After 20 weeks, the gestational age of the fetus can be estimated by measuring the fundus from the pubic symphysis to the top of the fundus. The fundal height in centimeters corresponds roughly to the gestational age in weeks. Prior to 24 weeks' gestation, all efforts should focus on the mother, with no modifications to CPR. However, early intubation and resumption of respirations and circulation is essential in all gravid arrests for the reasons mentioned earlier. Beyond 20 weeks or if the gravid uterus can be palpated above the umbilicus, several modifications of CPR should be instituted: (1) the patient should be positioned to minimize aortocaval compression, and (2) an emergency cesarean section should be considered.
Aortocaval compression must be limited in all patients beyond the twentieth week of gestation. This can be achieved by (1) having someone manually displace the uterus to the left, (2) tilting the patient 15 to 30° on a tiltable table, or (3) placement of a roll or a Cardiff wedge, if available, under the patient's right hip and flank. The Cardiff wedge provides a tilt of 27 percent, allowing 80 pecent of perfusion compared with CPR in the supine position. 9 Even this is minimal blood flow, considering that correctly performed CPR maintains 30 percent or less of normal cardiac output in nonpregnant adults. 1011 The "human wedge" has been advocated for bystander CPR. In this technique, the patient lies across the thighs of the rescuer, who is in a kneeling position. Despite relatively clear current recommendations regarding resuscitation in pregnancy, summarized in Table... .12-2, there remains a paucity of research in this area.6
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