Pregnancy Induced Hypertension

Description

Pregnancy-induced hypertension (PIH) is a spectrum of hypertensive disorders of pregnancy including gestational hypertension (GH), chronic hypertension, preeclampsia, and eclampsia.
GH is defined as systolic blood pressure (SBP) >140 mm Hg or diastolic blood pressure (DBP) >90 mm Hg in a woman without preexisting hypertension or signs of preeclampsia. It manifests after 20 weeks gestation and resolves by 12 weeks postpartum.
Chronic hypertension involves either pre-pregnancy hypertension (SBP >140 mm Hg or DBP >90 mm Hg) or failure of hypertension to resolve within 12 weeks postpartum.
Preeclampsia is the onset of hypertension and proteinuria after 20 weeks gestation with remission by 6–12 weeks postpartum. Eclampsia is new onset of seizures or unexplained coma in a woman with signs and symptoms of preeclampsia.

Epidemiology

Prevalence

Hypertension complicates ~20% of pregnancies
GH is encountered in ~5% of pregnancies.
Chronic hypertension is present in 1–2% of pregnancies.
Preeclampsia–eclampsia develops in ~5% of pregnancies in the US; nearly 20% of women with chronic hypertension develop preeclampsia.

Morbidity

Sustained hypertension can result in end-organ damage such as renal failure, left ventricular hypertrophy, and/or cerebrovascular accident.
Maternal morbidity associated with preeclampsia–eclampsia includes pulmonary edema, disseminated intravascular coagulation, hepatic rupture, HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), and seizures.
Fetal morbidity is due to increased incidence of placental abruption, intrauterine growth restriction, and preterm delivery.

Mortality

PIH is the third leading cause of maternal mortality in the US behind pulmonary embolus and hemorrhage. It accounts for ~10% of all deaths, with intracranial hemorrhage as the primary cause.
Approximately 10% of neonatal deaths occur in the presence of PIH.

Etiology/Risk Factors

GH risk factors: History of GH in a previous pregnancy.
Chronic hypertension risk factors
- Essential chronic hypertension: Obesity, African American ethnicity, increased salt intake, hyperlipidemia, family history
- Secondary chronic hypertension: Oral contraceptive use, renal disease, aortic coarctation, endocrine disorders
Preeclampsia-eclampsia risk factors
- Maternal: Age >40 years, African American ethnicity, obesity, hypertension, diabetes, thrombotic vascular disease (interestingly, smoking decreases the risk)
- Pregnancy-associated: Nulliparity, multiple gestations, molar pregnancy
- Fetal: Gestational age <28 weeks
- Paternal: History of fathering a preeclamptic pregnancy with another woman

Physiology/Pathophysiology

Chronic hypertension: Adrenergic hyperactivity and altered calcium homeostasis leading to decreased peripheral vascular resistance and cardiac stimulation; increased vasoreactivity leading to elevated systemic vascular resistance; increased renal reabsorption of salt and water leading to increased circulating blood volume.
The cause of preeclampsia remains unclear.

Anesthetic GOALS/GUIDING Principles

Control hypertension (target SBP <140 mm Hg; DBP <90 mm Hg).
Assess the severity of disease and end-organ damage.
Evaluate for preeclampsia and implement seizure prophylaxis if severe.
Accelerate fetal lung maturity for gestational age <36 weeks with betamethasone if preterm delivery is anticipated.
Regional anesthesia is preferred in the absence of coagulopathy and/or thrombocytopenia. Neuraxial analgesia may facilitate management of hypertension and avoidance of general endotracheal anesthesia for an emergent procedure.
Prepare for urgent delivery if indicated. Indications for emergent delivery include non-reassuring fetal heart tones lasting >10 minutes, placental abruption, end-organ damage, and/or seizure.

Symptoms

Decreased fetal movement
Preeclampsia: Shortness of breath, abdominal pain, seizures, visual disturbances, headaches

History

Prenatal history: Nulliparity, multiple gestations, molar pregnancy
PIH risk factors
Fetal anomalies/intrauterine growth restriction
Fasting status if urgent/emergent Cesarean delivery becomes necessary.

Signs/Physical Exam

Airway: Pharyngolaryngeal edema
Pulmonary: Pulmonary edema, hypoxemia.
Cardiovascular: Hypertension, LV hypertrophy, and/or decreased CVP.
Hematologic: Anemia, thrombocytopenia, and/or disseminated intravascular coagulation (DIC).
Renal: Decreased GFR, increased proteinuria, increased uric acid, increased urine protein:creatinine ratio, and/or oliguria.
Hepatic: Increased serum transaminases, hepatic edema, hepatic hematoma, periportal hepatic necrosis, rupture of Glisson's capsule with hepatic hemorrhage
Neurologic: Cerebral edema, cerebral hemorrhage.
Placental: Intrauterine growth restriction, non-reassuring fetal heart tracing, and/or placental abruption.

Medications

GH or chronic hypertension: Methyldopa 250 mg PO BID, maximum dose 3g/day; Labetalol 100 mg PO BID or TID, maximum dose 1,200 mg/day; Nifedipine 30–90 mg PO/day, maximum dose 120 mg/day.
Preeclampsia–eclampsia. antihypertensives: Hydralazine 5–10 mg IV q15 minutes; Labetalol 20 mg IV every 10 minutes, maximum dose of 300 mg. Seizure prophylaxis: Magnesium sulfate 4–6 g IV bolus over 15 minutes, followed by 1–2 g/hr.
Ergot alkaloids (e.g., Methergine) should be avoided due to risk of causing hypertensive crisis.
Betamethasone to stimulate fetal lung maturity in the setting of preterm delivery.

Diagnostic Tests & Interpretation

Labs/Studies

Labs: Urinalysis for proteinuria, CBC (especially platelets and Hct), CMP (magnesium), coagulation studies, type and cross.
Imaging studies (if indicated): Chest x-ray (pulmonary edema), head CT (useful in identifying cerebral edema, loss of cortical sulci, and/or cerebral hemorrhage), abdominal ultrasound, CT, or MRI (if hepatic infarction, hematoma or rupture suspected), echocardiogram (if cardiac dysfunction is suspected).

Circumstances to delay/Conditions

In cases of severe PIH prior to fetal lung maturity (24–34 weeks gestational age), consider delaying delivery for 48 hours after the administration of systemic steroids.
BP control is necessary prior to induction of general anesthesia, even in emergent deliveries.

Classifications

GH: Elevated BPs after 20 weeks gestation that resolves by 12 weeks postpartum.
Chronic hypertension: Pregnancy hypertension or hypertension in pregnancy that fails to resolve following delivery.
Preeclampsia–eclampsia: The new onset of hypertension and proteinuria after 20 weeks gestation.
Chronic hypertension with superimposed preeclampsia: The development of preeclampsia in a parturient with chronic hypertension.

PREOPERATIVE PREPARATION

Premedications

Aspiration prophylaxis in the setting of GETA (nonparticulate antacids, metoclopramide, H₂ blockers)
BP control
Seizure prophylaxis for preeclampsia–eclampsia.

INTRAOPERATIVE CARE

Choice of Anesthesia

Neuraxial anesthesia (spinal or epidural) preferred. Contraindications for neuraxial anesthesia include patient refusal, elevated intracranial pressure (ICP), inability to cooperate, evidence of coagulopathy, signs of local infection.
General anesthesia may be necessary in emergent deliveries (fetal distress, placental abruption, hepatic rupture, severe pulmonary edema, seizure, and/or end-organ dysfunction).
- Associated with increased risk of aspiration, transient neonatal depression, severe hypertension, and cerebral hemorrhage.
- Maternal mortality is 7-fold greater with GETA compared with neuraxial anesthesia. Failed intubations are 10 times more likely in obstetric patients compared with general population.

Monitors

Pulse oximetry: Decrease in SpO₂ in the setting of pulmonary edema, respiratory depression, and/or pulmonary aspiration.
BP monitoring: Consider invasive BP monitoring in the setting of refractory hypertension (BP >180/120) or for frequent blood sampling.
Central venous pressure: May be useful in determining volume status and for infusion of vasodilators.
Pulmonary arterial catheter rarely indicated but may be useful in the setting of severe cardiac disease and/or pulmonary hypertension.
Urinary output: Useful in evaluation of volume resuscitation and renal function.
Fetal heart tracing

Induction/Airway Management

Limit use of benzodiazepines and opioids prior to delivery; use is associated with neonatal depression.
General anesthesia for emergent deliveries.
- Rapid sequence intubation with cricoid pressure to minimized risk of aspiration.
- Avoid hypertensive response to laryngoscopy with deepening of anesthetic, remifentanil, and/or esmolol.

Maintenance

General anesthesia may be maintained with a combination of volatile anesthetic and nitrous oxide. Volatile anesthetic at <0.5 MAC minimizes a decrease in the uterine tone. IV opioids and benzodiazepines can be given following clamping of the cord. Magnesium sulfate prolongs duration of non-depolarizing neuromuscular blockade.

Extubation/Emergence

Airway edema may necessitate reintubation.
Severe hypertension and cerebral hemorrhage may accompany emergence and extubation.

Bed Acuity

Hemodynamically stable patients may be monitored on regular postpartum wards.
Magnesium sulfate should be continued for 24 hours postpartum in patients with preeclampsia/eclampsia. Preeclampsia and its associated complications may present de novo after delivery.
ICU admission may be indicated if there is evidence of severe end-organ damage including renal failure, cerebral hemorrhage, hepatic rupture, and/or pulmonary edema.

Medications/Lab Studies/Consults

Continue antihypertensive therapy until the BP normalizes.
Follow platelets, INR/PT, hepatic enzymes, BUN/Cr until values normalize.
In the setting of eclampsia, continue seizure prophylaxis for 24 hours following last seizure.

Complications

GH and chronic hypertension: Development of preeclampsia–eclampsia, hemorrhagic stroke, placental abruption
Complications associated with magnesium sulfate for seizure prophylaxis: Maternal toxicity, uterine atony, postpartum hemorrhage, fetal depression

Turner JA. Diagnosis and management of preeclampsia, an update. Int J Womens Health. 2010;2:327–337.
American College of Obstetricians and Gynecologists (ACOG) Practice bulletin. Diagnosis and management of preeclampsia and eclampsia. Obstet Gynecol. 2002;99(1):159–167.
Practice guidelines for obstetric anesthesia: An updated report by the American Society of Anesthesiologists Task force on Obstetric Anesthesia. Available at: http://www.asahq.org/publicationsandServices/OBguide.pdf. Accessed on Jan 08, 2011.

www.preeclampsia.org

See Also (Topic, Algorithm, Electronic Media Element)

ICD9

642.90 Unspecified hypertension complicating pregnancy, childbirth, or the puerperium, unspecified as to episode of care or not applicable

ICD10

O13.1 Gestational htn w/o significant proteinuria, first trimester
O13.2 Gestatnl htn w/o significant proteinuria, second trimester
O13.9 Gestational htn w/o significant proteinuria, unsp trimester
O13.3 Gestational htn w/o significant proteinuria, third trimester

PIH describes a spectrum of diseases: Gestational hypertension, preeclampsia, and chronic hypertension (with or without superimposed preeclampsia).
Preeclampsia is characterized as hypertension and proteinuria diagnosed after 20 weeks gestation. Management involves aggressive BP control, seizure prophylaxis, and monitoring for end-organ damage. Delivery of the fetus and placenta is the only definitive treatment
Regional anesthesia is preferred over general anesthesia for Cesarean delivery. When GETA is necessary, anticipate and treat BP lability and be prepared for a difficult airway.

Richard C. Jensen , MD

Judith A. Turner , MD, PhD

section name header

Basics ⬇

Prevalence

Morbidity

Mortality

Diagnosis ⬆ ⬇

History

Signs/Physical Exam

Labs/Studies

Treatment ⬆ ⬇

Premedications

Choice of Anesthesia

Monitors

Induction/Airway Management

Maintenance

Extubation/Emergence

Follow-Up ⬆ ⬇

References ⬆ ⬇

Additional Reading ⬆ ⬇

Codes ⬆ ⬇

Clinical Pearls ⬆ ⬇

Author(s) ⬆

section name header

Basics ⬇

Prevalence

Morbidity

Mortality

Diagnosis ⬆ ⬇

History

Signs/Physical Exam

Labs/Studies

Treatment ⬆ ⬇

Premedications

Special Concerns for Informed Consent

Choice of Anesthesia

Monitors

Induction/Airway Management

Maintenance

Extubation/Emergence

Follow-Up ⬆ ⬇

References ⬆ ⬇

Additional Reading ⬆ ⬇

Codes ⬆ ⬇

Clinical Pearls ⬆ ⬇

Author(s) ⬆