Indocyanine Green (ICG)
IC-Green · Verdye
Tricarbocyanine near-infrared fluorescent dye
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.
Indications
- •Sentinel lymph node mapping (breast, gynecologic, head-neck)
- •Tissue perfusion assessment (flap viability, anastomotic perfusion in colorectal/esophageal surgery)
- •Cholangiography during cholecystectomy
- •Hepatic function testing (ICG plasma disappearance rate / ICG-PDR)
- •Coronary artery imaging during cardiac surgery
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| SLN mapping | 1.25–2.5 mg subdermal or peritumoral 5–15 min preincision | — |
| Perfusion / flap | 0.1–0.3 mg/kg IV bolus during procedure (max 5 mg/kg cumulative) | — |
| ICG-PDR liver function | 0.5 mg/kg IV; measure plasma decay rate | — |
Pharmacokinetics
Onset seconds after IV. Half-life 3–4 min. Cleared exclusively by liver into bile (unaltered).
Hemodynamic effects
Minimal at standard doses. Anaphylactoid reactions reported but rare.
Respiratory effects
None directly.
Side effects
- !Anaphylactoid reaction (~1:10,000 — much rarer than isosulfan blue)
- !Iodide allergy potential — formulation contains <5% sodium iodide
- !No SpO2 interference (the key advantage over isosulfan blue / methylene blue)
- !Transient mild discoloration at injection site
Contraindications
- ×Iodide allergy (relative — many tolerate; pretreat or use alternative if known severe)
- ×Hypersensitivity to ICG
Clinical pearls
- ★PULSE OX FRIENDLY: unlike isosulfan blue and methylene blue, ICG fluoresces in near-infrared (805 nm) and does NOT interfere with pulse oximetry (660/940 nm). Major operational advantage.
- ★PERFUSION ASSESSMENT: real-time visualization of bowel/anastomotic perfusion has reduced anastomotic leak rates in colorectal surgery (PILLAR-II registry, multiple meta-analyses 2018+). Increasingly standard in laparoscopic and robotic colorectal/esophageal cases.
- ★DOSE WINDOW MATTERS: signal peak at ~1 minute post-IV, fades by 5 minutes. Surgeon needs to be ready to image when CRNA pushes the dye.
- ★IODIDE CAVEAT: technically contains <5% sodium iodide. True iodide-allergic patients are rare; document carefully if proceeding.
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.
- Isosulfan Blue (lymphatic mapping)
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.
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