What are the effects of administering medications via the arterial system?

Administering Medications via the Arterial System: Risks and Considerations

Administering medications via the arterial system is potentially dangerous and should be avoided except in rare, specific emergency circumstances when no other vascular access is available, as it can lead to severe tissue injury, gangrene, and limb loss.

Risks and Complications

Intra-arterial medication administration carries significant risks:

• Severe pain and paresthesias
• Motor dysfunction
• Compartment syndrome
• Tissue necrosis and gangrene
• Limb loss
• Vascular spasm
• Thrombosis and embolism
• Extravasation with severe skin injury 1

Emergency Situations Where Arterial Administration May Be Considered

In extremely limited circumstances, certain medications may be administered through arterial access when:

1. Venous access is impossible to establish
2. Intraosseous access cannot be obtained
3. The situation is life-threatening
4. No other alternatives exist 2

Medications That Should Never Be Given Intra-arterially

• Non-lipid-soluble drugs: Sodium bicarbonate and calcium can cause direct arterial injury 3
• Diazepam: Can cause severe tissue necrosis 3
• Phenytoin/fosphenytoin: Risk of vascular damage
• Hypertonic solutions: Can cause arterial spasm and tissue damage

Medications That Have Been Used Intra-arterially in Extreme Circumstances

In rare emergency situations, the following have been administered intra-arterially when no other access was available:

• Epinephrine (in cardiac arrest)
• Atropine
• Fentanyl
• Vecuronium 2

Management of Accidental Intra-arterial Injection

If accidental intra-arterial injection occurs:

1. Stop administration immediately
2. Leave the arterial catheter in place for potential administration of vasodilators
3. Administer phentolamine: 0.1–0.2 mg/kg (up to 10 mg) diluted in 10 mL of 0.9% sodium chloride injected intradermally at extravasation site to counteract vasoconstriction 3
4. Apply nitroglycerin paste to the affected area 4
5. Consider systemic anticoagulation to prevent thrombosis
6. Provide adequate analgesia for pain management
7. Monitor for compartment syndrome and tissue ischemia

Special Considerations for Vasoactive Medications

Vasoactive medications are particularly problematic when administered intra-arterially:

• Dopamine and epinephrine can cause severe vasoconstriction when given intra-arterially
• Doses of 20μg/kg/min may cause peripheral, renal, and splanchnic vasoconstriction and ischemia 3
• Extravascular administration can result in severe skin injury requiring immediate intervention with phentolamine 3

Contrast with Intended Arterial Therapies

It's important to distinguish unintended arterial administration from therapeutic procedures that intentionally use arterial routes:

• Intra-arterial thrombolytics for stroke or limb ischemia (e.g., alteplase) are specifically formulated and dosed for arterial administration 5
• These procedures are performed under controlled conditions by specialists with appropriate monitoring

Prevention of Accidental Intra-arterial Administration

To prevent accidental intra-arterial injection:

• Verify catheter placement before administering medications
• Use ultrasound guidance when placing difficult vascular access
• Be aware of anatomical variations that may increase risk
• Exercise caution in procedurally difficult situations
• Recognize signs of arterial cannulation (pulsatile flow, bright red blood)

Alternative Routes When Vascular Access is Difficult

When vascular access is difficult, consider these alternatives before resorting to arterial administration:

1. Intraosseous (IO) access: Preferred emergency alternative to IV access 3
2. Endotracheal administration: For lipid-soluble drugs (lidocaine, epinephrine, atropine, naloxone) 3
3. Intramuscular injection: For certain medications when appropriate

Remember that the arterial route should never be considered a routine alternative to venous access due to the significant risks involved.