Usage
Indocyanine Green (ICG) is a diagnostic aid used for:
- Determining cardiac output: Used in indicator-dilution studies during cardiac catheterization.
- Assessing hepatic function: Evaluates liver function by measuring the rate of ICG clearance from the bloodstream.
- Ophthalmic angiography: Visualizes the choroidal and retinal vasculature.
- Intraoperative imaging: Assesses blood flow and tissue perfusion in various surgical procedures, including vascular, gastrointestinal, organ transplant, plastic, micro, and reconstructive surgeries. It can also be used to visualize extrahepatic biliary ducts, and for lymphatic mapping in cervical and uterine cancer.
Pharmacological Classification: Diagnostic agent, specifically a tricarbocyanine dye.
Mechanism of Action: ICG is administered intravenously and remains within the vascular compartment due to its binding to plasma proteins. It is not metabolized and is eliminated exclusively by the liver through biliary excretion. ICG fluoresces in near-infrared light, enabling visualization of blood vessels and blood flow.
Alternate Names
- IC-Green
- Cardio Green
- Spy Agent Green
- VERDYE
How It Works
Pharmacodynamics: ICG’s primary effect is fluorescence upon excitation with near-infrared light, allowing visualization of blood vessels, blood flow, and tissue perfusion. It does not have significant pharmacological activity beyond its diagnostic properties.
Pharmacokinetics:
- Absorption: Administered intravenously and binds rapidly (98%) to plasma proteins, predominantly albumin.
- Distribution: Remains primarily within the intravascular compartment. Negligible distribution to renal, peripheral, lung, or cerebrospinal fluid.
- Metabolism: Not metabolized.
- Elimination: Excreted unchanged in the bile. Hepatic clearance is the primary route of elimination. No enterohepatic circulation occurs.
Mode of Action: ICG’s fluorescence properties are due to its tricarbocyanine structure. It absorbs light at specific wavelengths and emits light at slightly longer wavelengths, making it useful for imaging. It does not bind to specific receptors, inhibit enzymes, or modulate neurotransmitters.
Elimination Pathways: Hepatic excretion via the bile is the sole elimination pathway. No significant renal excretion.
Dosage
Standard Dosage
Adults:
- Cardiac Output: 5 mg IV bolus, followed by a saline flush. Multiple doses may be given. Maximum 2 mg/kg.
- Hepatic Function: 0.5 mg/kg IV bolus.
- Ophthalmic Angiography: Up to 40 mg IV bolus, followed by a saline flush.
- Intraoperative Imaging (Vessels, Blood Flow, Tissue Perfusion): 1.25 mg to 5 mg IV. Maximum 2 mg/kg.
- Intraoperative Imaging (Extremities Perfusion): 3.75 to 10 mg IV. Maximum 2 mg/kg.
- Visualization of Extrahepatic Biliary Ducts: 2.5 mg IV at least 45 minutes before surgery. Additional doses may be given. Maximum 2 mg/kg.
- Lymphatic Mapping: 5 mg (1.25 mg/mL solution) interstitial injection into the cervix (four 1 mL injections).
Children:
- Cardiac Output: Infants: 1.25 mg IV. Children: 2.5 mg IV. Maximum 2 mg/kg.
- Hepatic Function: Same as adult dose (0.5 mg/kg).
- Intraoperative Imaging (Vessels, Blood Flow, Tissue Perfusion): 1.25 to 5 mg IV. Lower doses may be given in younger patients and those with lower body weight. Maximum 2 mg/kg.
Special Cases:
- Elderly Patients: Exercise caution due to potential age-related organ dysfunction. Adjust dose as needed.
- Patients with Renal Impairment: No specific dosage adjustments are typically necessary due to hepatic elimination.
- Patients with Hepatic Dysfunction: Use with caution. Reduced ICG clearance may occur. Dosage adjustments may be necessary.
- Patients with Comorbid Conditions: Consider individual patient factors and adjust dosage accordingly.
Clinical Use Cases (Dosages provided above in Standard Dosages and Special Cases sections).
Dosage Adjustments
Dosage adjustments may be necessary based on age, weight, liver function, and specific clinical application. Always adhere to the maximum dose of 2 mg/kg.
Side Effects
Common Side Effects:
- Nausea
- Vomiting
- Headache
- Itching
- Sweating
- Green discoloration of feces and urine (transient)
- Discomfort or unease in the stomach
- Injection site reactions (pain, swelling, redness)
Rare but Serious Side Effects:
- Allergic reactions (urticaria, pruritus, rash, angioedema)
- Anaphylaxis (rare, but potentially fatal)
- Hypotension
- Tachycardia or arrhythmia
- Cardiac arrest (rare)
Long-Term Effects:
No specific long-term side effects are known.
Adverse Drug Reactions (ADR):
Anaphylaxis is a rare but serious ADR requiring immediate intervention. Treat with epinephrine, antihistamines, and corticosteroids.
Contraindications
- Known hypersensitivity to indocyanine green, iodine, or iodides.
Drug Interactions
- Heparin containing sodium bisulfite: Reduces the absorption peak of ICG. Avoid concomitant use.
- Medications that affect liver function: May alter ICG clearance and require dosage adjustment. Consult drug interaction resources for specific interactions.
- Refer to sections on “How it Works” and “Dosage” sections of the drug information for interactions with phenobarbital, nitrofurantoin, haloperidol, primidone and propranolol.
- Numerous other drug interactions have been reported: Consult a comprehensive drug interaction resource before administering ICG.
Pregnancy and Breastfeeding
- Pregnancy: Limited data suggest no adverse fetal effects. Use with caution and only if clearly indicated.
- Breastfeeding: Low subcutaneous doses are not detectable in breastmilk. Limited data suggest no adverse effects in infants. Use with caution, especially in newborns or preterm infants.
Drug Profile Summary (Provided in detail in the above sections.)
Popular Combinations
ICG is typically used alone.
Precautions (Provided in detail in the above sections.)
FAQs (Frequently Asked Questions)
(Several FAQs and their answers are provided throughout the document in their corresponding sections. Below are eight additional example questions and answers.)
Q1: How should ICG be prepared for administration?
A: Reconstitute the lyophilized powder with Sterile Water for Injection under sterile conditions. The reconstituted solution should be used within 6 hours.
Q2: Can ICG be administered to patients with shellfish allergies?
A: While ICG contains iodine, it’s different from the allergens in shellfish. However, use caution in patients with any iodine or iodide allergy due to the potential for cross-reactivity.
Q3: What are the signs and symptoms of an ICG allergic reaction?
A: Allergic reactions can range from mild (itching, hives) to severe (anaphylaxis). Signs and symptoms may include skin rash, itching, swelling (especially of the face, lips, or tongue), difficulty breathing, wheezing, dizziness, and loss of consciousness.
Q4: How is ICG clearance affected by liver disease?
A: ICG clearance is reduced in patients with liver dysfunction. Dosage adjustments may be necessary.
Q5: Can ICG be used in children?
A: Yes, ICG can be used in pediatric patients, including infants. Dosage adjustments based on weight and age are required.
Q6: What is the maximum recommended dose of ICG?
A: The maximum total dose is 2 mg/kg.
Q7: What should I do if a patient experiences an anaphylactic reaction to ICG?
A: Immediately discontinue ICG administration and provide supportive care, including airway management, oxygen, intravenous fluids, and appropriate pharmacological interventions such as epinephrine, antihistamines, and corticosteroids.
Q8: Are there any specific monitoring parameters required during ICG administration?
A: Monitor patients closely for allergic reactions, particularly during and immediately after administration. Observe vital signs and maintain readily available resuscitation equipment. For specific clinical applications, monitor the relevant physiological parameters (e.g., cardiac output during indicator-dilution studies).
