What are the preoperative anaesthetic considerations for patients with gestational hypertension?

Preoperative Anaesthetic Considerations in Gestational Hypertension

The preoperative anaesthetic management of patients with gestational hypertension requires specialized multidisciplinary care with careful attention to blood pressure control, assessment of end-organ damage, and optimization of maternal and fetal outcomes.

Definition and Classification

• Gestational hypertension is defined as systolic blood pressure (SBP) ≥140 mmHg and/or diastolic blood pressure (DBP) ≥90 mmHg that develops after 20 weeks of gestation in a previously normotensive woman 1, 2
• It can be classified as mild (SBP 140-149 and DBP 90-99 mmHg), moderate (SBP 150-159 and DBP 100-109 mmHg), or severe (SBP ≥160 and DBP ≥110 mmHg) 2

Preoperative Assessment

Blood Pressure Measurement and Control

• Accurate blood pressure measurement is essential using appropriate technique and equipment 1
• For severe hypertension (SBP ≥160 mmHg or DBP ≥110 mmHg), expeditious treatment should be initiated within 30-60 minutes to reduce the risk of maternal stroke 3
• First-line medications for acute severe hypertension include intravenous labetalol, hydralazine, or immediate-release oral nifedipine 3
• For non-severe hypertension, antihypertensive medications should be continued throughout the perioperative period 1

End-Organ Assessment

• A comprehensive evaluation for end-organ damage should include 1:
  • Fundoscopic examination to assess severity and chronicity of hypertension
  • Laboratory tests to rule out secondary causes of hypertension
  • Assessment for proteinuria to identify preeclampsia
• Evaluate for signs of HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), which requires special preparation for potential coagulation abnormalities 4

Airway Assessment

• Antenatal airway assessment is critical as physiological changes of pregnancy can complicate airway management if general anesthesia becomes necessary 4
• Pregnancy-related airway edema may be exacerbated in hypertensive patients, requiring careful planning for potential difficult airway 4

Preoperative Optimization

Hemodynamic Monitoring

• For patients with severe gestational hypertension, invasive hemodynamic monitoring should be considered 4:
  • Arterial line for continuous blood pressure monitoring
  • Central venous pressure monitoring to assess intravascular volume status
  • Continuous ECG and oxygen saturation monitoring

Fluid Management

• Cautious fluid management is critical as both hypovolemia and fluid overload can be detrimental 4
• Intravascular volume should be optimized prior to neuraxial anesthesia to prevent hypotension 4

Laboratory Investigations

• Preoperative laboratory tests should include 1, 4:
  • Complete blood count (to assess platelet count)
  • Coagulation profile
  • Liver function tests
  • Renal function tests
  • Urinalysis for proteinuria

Medication Management

• Continue antihypertensive medications throughout the perioperative period 1
• Special consideration for specific medications 2, 5:
  • Methyldopa is considered the drug of choice in pregnancy
  • Beta-blockers (except atenolol) appear to be safe in late pregnancy
  • Labetalol has efficacy comparable to methyldopa
  • ACE inhibitors and angiotensin II antagonists are contraindicated due to fetotoxicity

Anesthetic Planning

Choice of Anesthetic Technique

• Regional anesthesia (spinal or epidural) is generally preferred for cesarean section when there are no contraindications 1, 4
• When general anesthesia is required, careful attention must be paid to attenuating the hypertensive response to intubation 4
• Consider using fentanyl (5 μg/kg IV) to blunt the hypertensive response during rapid sequence induction 4

Intraoperative Management

• Maintain intraoperative mean arterial pressure (MAP) ≥60-65 mmHg or SBP ≥90 mmHg to reduce the risk of myocardial injury 1
• For patients with severe hypertension, vaginal delivery with epidural analgesia and elective instrumental delivery should be considered 1
• Caesarean delivery should be considered for obstetric indications or for patients with severe heart failure 1

Special Considerations

• Magnesium sulfate should be used during labor and for at least 24 hours postpartum to prevent seizures in women with severe preeclampsia 6
• The immediate postpartum period is particularly dangerous due to marked volume shifts from decompression of the vena cava and return of uterine blood to systemic circulation 4
• High-dependency monitoring for at least 24 hours postoperatively is recommended for patients with gestational hypertension 4

Common Pitfalls to Avoid

• Failure to recognize progression from gestational hypertension to preeclampsia 4, 7
• Underestimating the need for invasive monitoring in severe cases 4
• Inadequate preparation for potential coagulation abnormalities in HELLP syndrome 4
• Abrupt withdrawal of antihypertensive medications, particularly beta-blockers and clonidine, which can cause rebound hypertension 1