How is hypotension managed in pregnancy?

Management of Hypotension in Pregnancy

The immediate priority in managing hypotension during pregnancy is left lateral decubitus positioning to relieve inferior vena cava compression, followed by adequate hydration and careful assessment of the underlying cause. 1

Immediate Positional Intervention

• Left lateral decubitus positioning is the critical first-line intervention that must be implemented immediately, particularly after 20 weeks gestation when the gravid uterus compresses the inferior vena cava and impedes venous return 1, 2
• Manual left lateral uterine displacement should be performed simultaneously while pursuing other treatments—do not delay this intervention 1, 3
• Supine positioning in late pregnancy can cause severe cardiovascular collapse and has been documented as a cause of maternal and fetal death 4

Assessment of Hypotension

• Measure blood pressure after the patient sits or lies for 5 minutes, then repeat at 1 and/or 3 minutes after standing to assess for orthostatic hypotension 1
• Identify the underlying cause:
  • Physiologic vasodilation from hormonal changes in pregnancy 1
  • Position-related compression of the inferior vena cava (supine hypotensive syndrome) 1, 4
  • Orthostatic hypotension from increased blood volume 1
  • Iatrogenic causes from excessive antihypertensive therapy in women with hypertensive disorders 1

Fluid Management

• Adequate oral hydration is essential to maintain intravascular volume throughout pregnancy 1
• For acute symptomatic hypotension, administer intravenous crystalloid boluses (lactated Ringer's or balanced solutions preferred) 1, 3
• In severe cases requiring aggressive resuscitation, initial bolus of 1-2 liters administered rapidly within 60-90 minutes may be necessary 3
• Goal-directed fluid therapy using stroke volume monitoring has demonstrated improved hemodynamic stability and reduced vasopressor requirements in pregnant women, particularly those with hypertensive disorders 5

Additional Conservative Measures

• Compression stockings can improve venous return and reduce hypotension risk 1
• Avoid prolonged standing or lying supine 1
• Maintain adequate hydration throughout pregnancy as a preventive measure 1

Pharmacologic Intervention

When to Consider Vasopressors

• Vasopressors should be used with caution and only in severe cases where hypotension persists despite positioning and fluid resuscitation 1, 2
• Target mean arterial pressure (MAP) should be maintained at ≥65 mmHg 3
• Diastolic blood pressure should not fall below 80 mmHg to ensure adequate uteroplacental perfusion 3

Vasopressor Options

• Phenylephrine is commonly used during neuraxial anesthesia for cesarean delivery, though it does not appear to decrease placental perfusion sufficiently to alter neonatal Apgar scores or blood-gas status 6
• If hypotension persists after initial fluid bolus, norepinephrine may be initiated at 0.02 µg/kg/min 3

Special Considerations for Chronic Hypotension

• Historical studies suggest mineralocorticoids (11-Desoxycorticosterone) improved uteroplacental perfusion and fetal outcomes in chronically hypotensive pregnant women 7, 8, though these are older studies with limited contemporary application
• Norfenefrine hydrochloride has been studied for orthostatic dysregulation without adverse fetal effects 9, but is not widely used in current practice

Management in Women with Hypertensive Disorders

This is a critical pitfall area: Women being treated for hypertensive disorders of pregnancy can develop iatrogenic hypotension from excessive antihypertensive therapy 1

• Reduce or cease antihypertensive drugs if diastolic blood pressure falls below 80 mmHg 1
• Target diastolic blood pressure should be 85 mmHg in office settings, with systolic blood pressure maintained at 110-140 mmHg 1
• During labor and delivery, continue antihypertensive treatment to keep systolic BP <160 mmHg and diastolic BP <110 mmHg, but monitor closely for hypotension 1

Special Situations

Regional Anesthesia for Cesarean Section

• Pre-hydration with intravenous fluids before regional anesthesia helps prevent hypotension 1
• Left lateral tilt positioning during cesarean section is mandatory 1
• Hypotension induced by combined spinal-epidural anesthesia can compromise uteroplacental perfusion and cause fetal distress 5

Eclampsia with Hypotension

• Do not administer magnesium sulfate concomitantly with calcium channel blockers due to risk of severe hypotension 2
• Administer IV fluid boluses while monitoring response closely 2

Monitoring Requirements

• Regular blood pressure monitoring throughout pregnancy is essential to detect hypotension early 1
• Assess fetal growth and well-being with ultrasound if persistent hypotension is present 1
• Monitor for early maternal warning signs such as tachycardia and oliguria that may indicate worsening condition 2
• Continuous monitoring of vital signs including heart rate, respiratory rate, and oxygen saturation during acute episodes 2

Impact on Fetal Outcomes

• Untreated maternal hypotension is associated with reduced uteroplacental blood flow, which correlates with increased risk of miscarriages, premature delivery, and small-for-gestational-age infants 9, 8
• Studies demonstrate that treatment of maternal hypotension improves placental perfusion and results in higher birth weights and reduced rates of fetal dystrophy 7, 8