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. 2026 Aug 10;17:1876072. doi: 10.3389/fphar.2026.1876072

FIGURE 2.

Two labeled photographs compare a blood collection syringe with an exposed needle and blue protective cap on the left (A) and the same syringe on the right (B) with a transparent safety cap covering the needle, separated by a right-pointing arrow indicating a procedure step or transition.

Macroscopic changes in arterial blood color before and after treatment. (A) Arterial blood sample obtained before treatment showing a characteristic chocolate-brown discoloration, consistent with elevated methemoglobin levels. (B) Arterial blood sample obtained after methylene blue administration demonstrating restoration of normal bright red color, indicating improvement in hemoglobin oxygen-carrying capacity.