DOI: 10.1097/01.aoa.0000350591.44088.e8
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Issn Print: 0275-665X
Publication Date: 2009/06/01
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Excerpt
Primary central nervous system tumors occur at a rate of 6/100,000 and are not more frequent in pregnancy. Symptoms may arise because of increased tumor growth or edema, increased vascularity during pregnancy, or pregnancy-related immunotolerance. ICH results from SAH from ruptured aneurysms (65%), bleeding from AVMs (35%), or other rare causes. ICH accounts for 7% of pregnancy-related maternal mortality, with most cases occurring antenatally. AVM does not create an increased risk of hemorrhage in pregnant women, but re-bleeding is 25% compared to a 3% risk of re-bleeding within a year in nonpregnant women. SAH is a leading cause of indirect maternal death and, during pregnancy, has a 35% and 25% risk of maternal or fetal death, respectively. Resuscitation of pregnant patients after traumatic brain injury is a priority because it will also resuscitate the fetus. Rapid sequence induction with thiopental or propofol and succinyl choline should be used for tracheal intubation. Left lateral tilting of the whole body should be performed to avoid aorto-caval compression and to avoid spinal rotation. When spinal procedures are necessary in pregnant women, the prone position may create difficulties for fetal monitoring, and emergent cesarean delivery. Increased epidural venous bleeding may also occur but placental perfusion may improve compared to the supine position.
Fetal concerns during neuroanesthesia are positional and anesthetic-related reductions in uteroplacental perfusion and/or compromise of fetal gas exchange. Direct effects of anesthetic and analgesic drugs during organogenesis also must be considered along with any exposure to radiation, the effects of which are highly dependent on dose and gestational age. Perioperative fetal heart rate monitoring is based on the individual situation and whether the patient will accept intervention if fetal compromise occurs. Although easily detected after 16 weeks' gestation, changes in fetal heart rate are predictive of neonatal compromise only after 24 weeks and may occur in a healthy fetus, making unnecessary delivery a risk.
If neurosurgery is performed at <24 weeks of gestation, fetal management is based on obstetric considerations. If the fetus is viable at the time of neurosurgery, the anesthesiologist may have to maintain the fetus in utero, perform a cesarean delivery before the neurosurgical procedure, or perform the cesarean delivery followed by later neurosurgery. A multidisciplinary approach is needed to individualize anesthetic requirements while considering the gestational age of the fetus. Anticonvulsant therapy may be needed or continued and aspiration prophylaxis should be considered, although good evidence for efficacy is lacking. The respiratory changes associated with pregnancy will increase oxygen requirements and make arterial oxygen desaturation more likely. Airway management may be more difficult. A laryngeal mask airway should not be used in pregnant neurosurgical patients other than as an emergency rescue for failed intubation.
Intraoperatively, blood pressure should be maintained as close to baseline values as possible and arterial carbon dioxide tension should be kept in the range of 25 to 30 mm Hg. Intra-arterial blood pressure monitoring is thus recommended. Severe hyperventilation may cause uterine artery vasoconstriction and leftward shift of the hemoglobin oxygen dissociation curve. The bispectral index should be used to monitor the depth of anesthesia.
