Which statement correctly describes the risk associated with intra-arterial injection of thiopental?

Which statement correctly describes the risk associated with intra-arterial injection of thiopental?

• A. It is highly acidic causing venous irritation
• B. It is highly basic, causing vasospasm and pain
• C. It has neutral pH and causes no vascular reaction
• D. It is lipophilic causing rapid diffusion away from the artery

Answer: (B)

Thiopental solutions are highly alkaline, with a pH around 10–11. When such a solution is accidentally injected into an artery, the alkaline irritant directly contacts the arterial endothelium, triggering marked vasospasm and intense pain. This spasm reduces distal blood flow and can lead to ischemia or tissue necrosis if not recognized and treated promptly. So the key risk is the alkaline, irritating nature of the preparation causing arterial spasm and pain, rather than acidity, neutrality, or diffusion concerns.

Thiopental solutions are highly alkaline, with a pH around 10–11. When such a solution is accidentally injected into an artery, the alkaline irritant directly contacts the arterial endothelium, triggering marked vasospasm and intense pain. This spasm reduces distal blood flow and can lead to ischemia or tissue necrosis if not recognized and treated promptly. So the key risk is the alkaline, irritating nature of the preparation causing arterial spasm and pain, rather than acidity, neutrality, or diffusion concerns.