What is a good diastolic blood pressure (DBP) parameter for holding hydralazine?

Diastolic Blood Pressure Parameters for Holding Hydralazine

The recommended diastolic blood pressure (DBP) parameter for holding hydralazine is 60 mmHg, particularly in patients with diabetes mellitus, those over 60 years of age, or those with coronary artery disease and heart failure with evidence of myocardial ischemia. 1

Understanding Hydralazine's Hemodynamic Effects

• Hydralazine is a direct vasodilator that can cause significant and unpredictable blood pressure reductions with a prolonged duration of action (2-4 hours) 2
• It is typically administered 2-3 times daily (100-200 mg/day total) for chronic hypertension management rather than as a single dose 2
• Hydralazine is associated with sodium and water retention and reflex tachycardia, making it less desirable as a first-line agent for acute hypertension treatment 2, 3

Specific DBP Parameters for Different Clinical Scenarios

General Population

• For most hypertensive patients, the target DBP is <80 mmHg 1
• When systolic BP is at or below target (120-129 mmHg) but diastolic BP is not at target (≥80 mmHg), intensifying treatment to achieve a diastolic BP of 70-79 mmHg may be considered 1

High-Risk Populations

• In patients with elevated DBP who have coronary artery disease and heart failure with evidence of myocardial ischemia, caution is advised in inducing falls of DBP below 60 mmHg if the patient has diabetes mellitus or is over 60 years of age 1
• In older hypertensive individuals with wide pulse pressures, lowering systolic BP may cause very low DBP values (<60 mmHg), which requires careful assessment for signs of myocardial ischemia and worsening heart failure 1

Monitoring After Hydralazine Administration

• Blood pressure typically begins to decrease within 10-30 minutes after administration, and the effect lasts 2-4 hours 2
• If hydralazine has already been administered, wait 2-4 hours to assess full effect before giving additional doses 2
• Monitor for potential adverse effects including:
  • Hypotension (most common adverse event) 4
  • Reflex tachycardia 2, 3
  • Sodium and water retention 2

Hydralazine Use in Specific Clinical Contexts

Hypertensive Emergencies

• For hypertensive emergencies, the immediate goal is to decrease mean BP by 15-25% with the target to achieve SBP 140-150 mmHg and DBP 90-100 mmHg 1
• Alternative agents with more predictable responses and shorter half-lives (nicardipine, labetalol, clevidipine) are often preferred for hypertensive emergencies 2, 3

Pregnancy-Related Hypertension

• For severe pre-eclampsia, IV hydralazine is widely used, particularly in North America, despite being associated with adverse effects related to maternal hypotension 1
• For preeclampsia, a conservative dosing regimen of 5 mg IV bolus initially, then 10 mg every 20-30 minutes to a maximum of 25 mg is recommended 5

Conclusion

When using hydralazine for blood pressure management, hold the medication if DBP falls below 60 mmHg, especially in high-risk patients. The unpredictable response and prolonged duration of action of hydralazine necessitate careful monitoring of blood pressure after administration.