A 67-year-old man admitted for right lower lobe pneumonia subsequently develops hypotension and lactic acidosis. He is started on a norepinephrine intravenous drip. A few hours later, the antecubital vein being used for the infusion blanches and the tissues surrounding the IV site become cold, hard, and pale. Local injection of the affected tissues with which of the following agents is most likely to be of greatest benefit?

Question

A 67-year-old man admitted for right lower lobe pneumonia subsequently develops hypotension and lactic acidosis.  He is started on a norepinephrine intravenous drip.  A few hours later, the antecubital vein being used for the infusion blanches and the tissues surrounding the IV site become cold, hard, and pale.  Local injection of the affected tissues with which of the following agents is most likely to be of greatest benefit?

Quizplus · Accepted Answer

Development of venous blanching along with induration and pallor of the tissues surrounding the norepinephrine infusion site are signs of norepinephrine extravasation. The norepinephrine leak causes intense α₁ receptor mediated vasoconstriction which can lead to local tissue necrosis. Such necrosis can be prevented by infiltration (using a syringe with a fine hypodermic needle) throughout the affected area with phentolamine, an α receptor blocker leading to vasodilatation (thus counteracting the vasoconstrictive effects of norepinephrine). This antidote must be given within 12 hours of extravasation to be effective. (Choice A) Calcium gluconate is administered for severe hypocalcemia and for severe hyperkalemia (acts as a cardioprotective agent that prevents arrhythmias); it would not lead to the desired effect of vasodilation. (Choice C) Heparin is indicated if there is an arterial thrombosis (cold, pulseless, painful limb), but this patient does not have any risk factors for arterial thrombosis (eg, atrial fibrillation, arterial catheterization) and norepinephrine extravasation is a much more likely cause of his limb symptoms. (Choice D) Isoproterenol can mediate vasodilation via β₂ receptor activation, particularly in striated muscle, renal, and mesenteric vascular beds, leading to decreased peripheral vascular resistance with increased cardiac output. Subcutaneous tissue blood vessels have a relatively low β₂ receptor density compared to α1 receptors, thus, an alpha blocker would likely be more effective in reversing α₁ receptor mediated vasoconstriction. (Choice E) Lidocaine can relax vascular smooth muscle via blockade of Na⁺ current mediated action potentials. However, in this case, extravasation of norepinephrine is responsible for the vasoconstriction; nerve blockade would not reverse the ischemia. Educational objective: Blanching of a vein into which norepinephrine is being infused together with induration and pallor of the tissues surrounding the IV site are signs of norepinephrine extravasation and resulting vasoconstriction. Tissue necrosis is best prevented by local injection of an α receptor blocking drug, such as phentolamine.

A 67-Year-Old Man Admitted for Right Lower Lobe Pneumonia Subsequently