Remember that Not All Blue-Colored Compounds are the Same
Remember that Not All Blue-Colored Compounds are the Same
Chauncey T. Jones MD
There are many blue dye compounds, and each is used for a variety of purposes. Their uses include food coloring, dye for materials, antiseptics, tissue stains, chemical reaction indicators, and to treat diseased aquarium life. Blue dyes are also used in humans for both diagnostic and therapeutic purposes. These dyes include methylene blue, patent blue, isosulfan blue, and indigo carmine. While these substances are all blue in color, they are distinct compounds and have widely varying properties, uses, and adverse effects (Table 56.1).
Methylene blue has been used in many clinical situations in humans. It is used primarily as an antidote for both chronic methemoglobinemia (e.g., occurring with dapsone therapy) and acute methemoglobinemia. At low concentrations it promotes the reduction of methemoglobin (the ferric form of hemoglobin) to hemoglobin by acting as a cofactor for the enzyme NADPH-methemoglobin reductase. The recommended dose is 1 to 2 mg/kg administered intravenously (IV). The dose may be repeated after 1 hour if symptoms persist.
Methylene blue has been used as a sentinel lymph node tracer for breast cancer and may be as efficacious and have fewer side effects than other blue dyes more traditionally used for this purpose. It has also been used as a genitourinary antiseptic and for topical virus therapy. The antimicrobial effect is presumed to be secondary to its oxidative/reduction properties.
TABLE 56.1 BLUE DYE COMPOUNDS
BLUE COMPOUND
COMMON USES
ADVERSE EFFECTS
Methylene blue
▪ Antidote for metHgb
▪ Sentinel lymph node tracing
▪ Genitourinary antiseptic
▪ Septic shock
▪ Cyanide toxicity
▪ Hypertension
▪ Chest pain
▪ Anemia
▪ Bladder irritation
▪ Transient, false SpO2 decrease
▪ Headaches, diaphoresis, abdominal pain
Patent blue
▪ Sentinel lymph node tracing
Breast cancer
Melanoma
Endometrial cancer
Colon cancer
▪ Severe anaphylaxis
▪ Prolonged, false SpO2 decrease
Isosulphan blue
▪ Tumor marking
▪ Lymphangiography
▪ Urticarial reactions
▪ Anaphylaxis
▪ Transient, false SpO2 decrease
Indigo carmine
▪ Urology
Locate ureteral orifices during cystoscopy
Test anastomoses
Identify transected ureters intraoperatively
▪ Mild elevation of blood pressure
▪ Relatively low side-effect profile
▪ Transient, false SpO2 decrease
Indocyanine green
▪ Ophthalmology
Macular surgery
Cataract surgery
▪ Blood volume, cardiac output determinations
▪ Infrared therapy for colon cancer
▪ Can be toxic to eye unless thoroughly washed out
▪ Transient, false SpO2 decrease
Blue #1
FDA black box warning against use in enteral feeds for detecting aspiration
▪ Refractory hypotension
▪ Metabolic acidosis (acts as a mitochondrial toxin)
▪ Worse in patient with increased gastrointestinal permeability
▪ Death
Although it is not the treatment of first choice, at high concentrations methylene blue can be used to treat cyanide toxicity by converting ferrous hemoglobin to ferric methemoglobin. Methemoglobin combines with cyanide to form cyanmethemoglobin. This serves as an alternative pathway for cyanide and prevents it from combining with cytochrome oxidase, which results in cyanide toxicity.
Possible side effects of methylene blue include hypertension; chest pain; headache; confusion; dizziness; diaphoresis; anemia; discoloration of skin, urine, and feces; nausea; vomiting; abdominal pain; and bladder irritation. The increase in blood pressure caused by methylene blue is so pronounced that it was historically used as a treatment for septic shock, before the era of modern-day vasopressors.
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