Isosulfan Blue (lymphatic mapping)
Lymphazurin 1%
Triarylmethane lymphatic-mapping dye
Selectively absorbed into lymphatic capillaries after subdermal/peritumoral injection. Tracks to first-station lymph node → blue staining identifies the sentinel node for biopsy in breast, melanoma, and gynecologic cancers.
Indications
- •Sentinel lymph node mapping in breast cancer, melanoma, vulvar cancer
- •Lymphatic mapping for gastric, colorectal, head-neck cancer (variable use)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Breast / melanoma SLN | 3–5 mL of 1% solution subdermally around the tumor or biopsy site, 5–10 min before incision | — |
Pharmacokinetics
Lymphatic uptake within 5 min; transit to sentinel node within 15 min. Eliminated in bile and urine.
Hemodynamic effects
Anaphylactoid reactions can cause severe hypotension — see pearls.
Respiratory effects
Bronchospasm in anaphylactoid reactions.
Side effects
- !ANAPHYLACTOID REACTION (~1–2% incidence) — most clinically dangerous of the lymphatic dyes. Can present as profound hypotension within 5–30 min of injection.
- !BLUE SKIN DISCOLORATION at injection site (transient days to weeks)
- !FALSELY LOW PULSE OXIMETRY for 4–24 h (dye absorbs at 660 nm, fooling the SpO2 algorithm — co-oximetry from ABG gives true SaO2)
- !URINE / STOOL DISCOLORATION (blue/green for 24–48 h — counsel patient)
Contraindications
- ×Triphenylmethane dye allergy
Clinical pearls
- ★PULSE OX TRAP: SpO2 drops to ~85–88% within minutes of injection — but PaO2 on ABG is normal. Co-oximetry confirms true saturation. Do NOT increase FiO2 chasing the false reading.
- ★ANAPHYLAXIS RISK: highest of lymphatic dyes. Have epinephrine, IV access, fluids ready BEFORE injection. Onset can be 5–30 min after injection. Methylene blue is the alternative when anaphylaxis history exists.
- ★DOSE LIMIT: 5 mL is the typical max. More dye = more interference with intra-operative imaging without better mapping.
- ★ICG ALTERNATIVE: indocyanine green with near-infrared imaging is replacing isosulfan blue at many centers — equivalent mapping with no anaphylactoid risk and no SpO2 interference.
Other drugs in Blue Dyes
- Methylene Blue
Inhibits guanylate cyclase + nitric oxide synthase → reverses NO-mediated vasodilation. At low dose, reduces methemoglobin (Fe³⁺) → hemoglobin (Fe²⁺) via NADPH-methemoglobin reductase pathway.
- Indocyanine Green (ICG)
After IV or interstitial injection, ICG binds plasma proteins (mostly albumin) and fluoresces at 805–835 nm under near-infrared (NIR) imaging. Used for real-time vascular and lymphatic visualization, hepatic function testing, and tissue perfusion assessment.
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