What intravenous agents should be avoided in a hypertensive emergency?

Agents to Avoid in Hypertensive Emergency

Sodium nitroprusside should be used with extreme caution or avoided entirely due to cyanide toxicity risk, particularly with prolonged infusions or doses ≥4 mcg/kg/min for >30 minutes. 1, 2

High-Risk Agents Requiring Caution or Avoidance

Sodium Nitroprusside

• Should be avoided as first-line therapy due to significant toxicity concerns, despite its historical use 2
• Cyanide toxicity risk increases substantially with infusion rates ≥4-10 mcg/kg/min or duration >30 minutes 1
• Thiosulfate coadministration is required for higher doses or prolonged use to prevent cyanide toxicity 1
• Contraindicated in liver/kidney failure (relative contraindication) 1
• Decreases regional coronary blood flow in patients with coronary abnormalities and increases myocardial damage after acute MI 1
• Should not be used in acute coronary syndromes due to these adverse coronary effects 1

Hydralazine

• Not recommended as first-line therapy due to unpredictable antihypertensive effects and difficult blood pressure titration 3
• Associated with adverse perinatal outcomes in pregnancy, making it less preferred than labetalol or nicardipine for severe preeclampsia 1
• Slow and unpredictable onset makes controlled BP reduction difficult 2

Nitroglycerin

• Should be avoided in patients with increased intracranial pressure 4
• Significant absorption by PVC tubing (only 20-60% of dose delivered), making dosing unpredictable unless non-PVC tubing is used 5
• Requires careful attention to infusion equipment to ensure accurate dosing 5

Nifedipine (Immediate-Release Oral)

• Should not be considered first-line therapy due to significant toxicities and adverse effects 2
• Unpredictable BP reduction and inability to titrate make it unsuitable for hypertensive emergencies 3

Contraindications for Specific Beta-Blockers

Labetalol - Avoid in:

• Second or third-degree AV block 1, 6
• Systolic heart failure 1
• Asthma and reactive airways disease 1, 6
• Bradycardia 1
• Pheochromocytoma (has been associated with paradoxical acceleration of hypertension) 1
• COPD 6

Esmolol - Avoid in:

• Concurrent beta-blocker therapy 6
• Bradycardia 7
• Decompensated heart failure 6, 7
• Second or third-degree AV block without pacing 7
• Sinus node dysfunction 7

Special Clinical Scenarios

Cocaine/Amphetamine Intoxication

• Beta-blockers (including labetalol) are relatively contraindicated as they do not effectively reduce coronary vasoconstriction 1
• Beta-blockade without alpha-blockade can worsen hypertension due to unopposed alpha-mediated vasoconstriction 1
• Benzodiazepines should be initiated first, followed by phentolamine, nicardipine, or nitroprusside if needed 1

Eclampsia/Preeclampsia

• Nitroprusside is contraindicated due to risk of fetal cyanide toxicity 1
• Cumulative labetalol dose should not exceed 800 mg/24h to prevent fetal bradycardia 1

Pheochromocytoma

• Beta-blockers must only be given after alpha-blockade is established 7
• Administration of beta-blockers alone causes paradoxical BP increase from attenuation of beta-mediated skeletal muscle vasodilation 7

Common Pitfalls to Avoid

• Never use oral agents for true hypertensive emergencies with acute end-organ damage 1
• Avoid rapid BP reduction beyond 25% in first hour (except aortic dissection, severe preeclampsia, pheochromocytoma) to prevent organ hypoperfusion 1, 6
• Do not use non-selective beta-blockers in Prinzmetal's angina due to unopposed alpha-mediated coronary vasoconstriction 7
• Avoid fenoldopam in patients with increased intraocular pressure, glaucoma, or sulfite allergy 6