1. Many of the symptoms associated with preeclampsia may result from an imbalance between the placental production of prostacyclin and thromboxane.
2. The HELLP syndrome is a form of severe preeclampsia characterized by hemolysis, elevated liver enzymes, and low platelet count. In contrast to preeclampsia, elevations in blood pressure and proteinuria may be mild.
3. General Management (Table 40-9)
4. Anesthetic Management
a. Epidural anesthesia or combined spinal–epidural analgesia for labor and delivery is acceptable provided no clotting abnormality or plasma volume deficit is present. In volume-repleted parturients positioned with left uterine displacement, the institution of epidural anesthesia does not typically cause an unacceptable decrease in blood pressure and may result in significant improvements in placental blood flow.
TABLE 40-7 ANESTHETIC COMPLICATIONS IN OBSTETRIC PATIENTS
Maternal Mortality
Most often related to arterial hypoxemia during airway management difficulties
Pregnancy-induced anatomic changes: Decreased functional residual capacity, increased oxygen consumption, or oropharyngeal edema may expose the parturient to an increased risk of arterial oxygen desaturation during periods of apnea and hypoventilation
Pulmonary Aspiration
Hypotension
Regional anesthesia: Related to the degree and rapidity of local anesthetic-induced sympatholysis
Prehydration: 1,000–1,500 mL of crystalloid solution before initiation of regional anesthesia and avoidance of aortocaval compression may decrease the incidence of hypotension
Treatment is left uterine displacement, rapid IV fluid infusion, and vasopressor administration (phenylephrine 100–150 μg results in less fetal acidosis than ephedrine)
Total Spinal Anesthesia
Local Anesthetic Systemic Toxicity
Maintain hemodynamics, ventilation and oxygenation
Consideration of early administration of 20% lipid emulsion (1.5 mg/kg over 1 minute followed by 0.25 mL/kg for at least 10 minutes after attainment of hemodynamic stability)
Treatment is with IV administration of thiopental (50–100 mg) or diazepam (5–10 mg)
Postdural Puncture Headache
The incidence is lower with pencil-point needles (Whitacre or Sprotte) compared with diamond-shaped (Quincke) cutting needles
Treatment of a severe headache is with a blood patch (10–15 mL of the patient’s blood is injected into the epidural space close to the site of dural puncture)
Nerve Injury
The possible role of compression of the maternal lumbosacral trunk by the fetus should be considered
IV = intravenous.
b. Spinal anesthesia may produce severe alterations in cardiovascular dynamics resulting from sudden sympathetic nervous system blockade.
TABLE 40-8 SYMPTOMS OF SEVERE PREECLAMPSIA
Systolic blood pressure >160 mm Hg
Diastolic blood pressure >110 mm Hg
Proteinuria >5 g/24 hours
Evidence of end-organ damage
• Oliguria (<400 mL/24 hours)
• Cerebral or visual disturbances
• Pulmonary edema
• Epigastric pain
• Intrauterine growth retardation
Thrombocytopenia (steroids may prevent)
c. General anesthesia is often chosen for acute emergencies, but the practitioner should keep in mind the probable exaggerated blood pressure responses to induction of anesthesia and intubation of the trachea and possible interactions of muscle relaxants with magnesium sulfate therapy.
d. Decreased doses of ephedrine are recommended to treat patients with hypotension because parturients with preeclampsia or eclampsia may exhibit increased sensitivity to vasopressors.
B. Obstetric hemorrhage is the leading cause of maternal mortality, causing 25% of peripartum deaths.
1. Placenta previa (painless bright red bleeding after the seventh month of pregnancy) is the most common cause of postpartum hemorrhage.
2. Abruptio placentae typically manifests as uterine hypertonia and tenderness with dark red vaginal bleeding. Maternal and fetal mortality rates are increased.
TABLE 40-9 CONSIDERATIONS IN THE MANAGEMENT OF PARTURIENTS WITH PREECLAMPSIA OR ECLAMPSIA
Prevent or control seizures with magnesium sulfate: Neuroprotective for the fetus and may reduce the risk of cerebral palsy
Restore intravascular fluid volume (central venous or pulmonary capillary wedge pressure, 5–10 mm Hg; urine output, 0.5–1 mL/kg/hr)
Normalize blood pressure (hydralazine, nitroprusside)
Correct coagulation abnormalities
TABLE 40-10 CONGENITAL HEART DISEASE AND THE PARTURIENT
Prior successful surgical repair (asymptomatic)
Uncorrected or partially corrected: May experience cardiac decompensation with pregnancy
Eisenmenger’s syndrome: Pulmonary hypertension reverses flow to a right-to-left shunt; general anesthesia is often selected
3. General anesthesia (often with ketamine [0.75 mg/kg IV] induction of anesthesia) is used in view of the increased risk of hemorrhage and clotting disorders.
C. Heart Disease. Cardiac decompensation and death occur most commonly at the time of maximum hemodynamic stress. For example, cardiac output increases during labor, with the greatest increase immediately after delivery of the placenta. These changes in cardiac output are blunted by regional anesthesia.
1. Congenital Heart Disease (Table 40-10)
2. Valvular Heart Disease (Table 40-11)
3. Primary pulmonary hypertension is seen predominantly in young parturients, and pain during labor and delivery may further increase pulmonary vascular resistance. (Neuraxial analgesia is useful.)
TABLE 40-11 HEMODYNAMIC GOALS WITH VALVULAR LESIONS
HR = heart rate; SVR = systemic vascular resistance.
4. Cardiomyopathy of pregnancy is left ventricular failure in late pregnancy or in the first 6 weeks postpartum (occurs approximately one in 3,000 births and is associated with a maternal mortality of 25% to 50%). It is a diagnosis of exclusion and thought to be related to myocarditis or an abnormal immune response.
5. Coronary artery disease and myocardial infarction are rare but are associated with high maternal and infant mortality rates.
6. Sudden Arrhythmic Death Syndrome (SADS) is a sudden cardiac death in which all other causes have been eliminated (normal heart, no stimulant drugs).
D. Diabetes Mellitus. Gestational diabetes mellitus or glucose intolerance is first diagnosed during pregnancy. (There is an increasing incidence with obesity.)
E. Obesity is associated with antenatal comorbidities (hypertension, diabetes, preeclampsia) and an increasing need for cesarean delivery. Despite technical challenges, continuous neuraxial analgesia provides excellent pain relief during labor and delivery.
F. Advanced maternal age (older than 35 years of age) is associated with poorer outcomes and a higher incidence of maternal morbidities (gestational diabetes, preeclampsia, placental abruption, cesarean delivery) and chronic medical conditions.
VII. PRETERM DELIVERY. Preterm labor and delivery is defined as birth before the 37th week or term weight of an infant as more than 2 standard deviations below the mean (small for gestational age). Such infants account for 8% to 10% of all births and nearly 80% of early neonatal deaths in the United States.
A. Several problems are likely to develop in preterm infants (Table 40-12).
B. β2-Agonists (ritodrine, terbutaline) used to inhibit labor may interact with anesthetic drugs or produce undesirable changes before induction of anesthesia (Table 40-13).
1. Delay of anesthesia for at least 3 hours after the cessation of tocolysis allows β-mimetic effects of β2-agonists to dissipate; potassium supplementation is not necessary.
2. Preterm infants are more sensitive to the depressant effects of anesthetic drugs. Regardless of the technique or drugs selected, the most important goal is prevention of asphyxia of the fetus.
TABLE 40-12 PROBLEMS ASSOCIATED WITH PREMATURITY
Respiratory distress syndrome: Glucocorticoids administered to the mother for 24–48 hours may enhance fetal lung maturity
Intracranial hemorrhage
Hypoglycemia
Hypocalcemia
Hyperbilirubinemia
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