Why ICG is not retaining in Artery for More than 2 minutes?
| Discussion in 'All Categories' started by Sadhana - Jun 21st, 2025 6:50 am. | |
Sadhana
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I want to know that when I want to see uterine artery during TLH Why ICG is not retaining in Artery for More than 2 minutes? |
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re: Why ICG is not retaining in Artery for More than 2 minutes?
by Dr B S Bhalla -
Nov 19th, 2025
11:53 am
#1
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Dr B S Bhalla
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Why ICG Does Not Stay in the Uterine Artery for More Than 2 Minutes 1️⃣ ICG Is Not an Intravascular Contrast Like CT Dye ICG is not designed to stay inside an artery for long. It binds rapidly to plasma proteins (especially albumin) and immediately flows with blood into: • Arterioles • Capillaries • Venules • Systemic circulation Because of this, the bright fluorescence in a specific artery lasts only during the arterial phase, which is 30–60 seconds, fading by 90–120 seconds. ⸻ 2️⃣ High Uterine Blood Flow Washes ICG Very Quickly The uterine artery has one of the highest flow rates among pelvic vessels. During surgery: • Blood flow is continuous • ICG bolus gets washed out in seconds • New blood (without ICG) replaces the dye rapidly This washout effect is the main reason fluorescence disappears. ⸻ 3️⃣ ICG Half-Life Is Extremely Short ICG has a plasma half-life of 2.5 to 3 minutes. This means: • Intensity peaks quickly • Then rapidly drops • Tissue fluorescence (myometrium, cervix) may continue, but arterial fluorescence fades So the artery itself will not retain dye. ⸻ 4️⃣ Near-Infrared Imaging Shows Only “Transit,” Not Storage The NIR camera (Firefly / NIR mode) doesn’t show dye stored in the artery; it only highlights the moment ICG passes through the vessel. This is why you see: • Bright flash during arrival • Fading during capillary phase • Almost no signal after 2 minutes It’s normal physiology. ⸻ 5️⃣ ICG Goes Immediately Into the Capillary Bed Once ICG reaches the uterus: • It diffuses into the dense capillary network • Signal spreads into surrounding tissue • Arterial-specific fluorescence disappears Since uterine capillary density is very high, washout is rapid. ⸻ 6️⃣ The Dye Is Cleared Quickly by the Liver ICG is removed exclusively by the liver within minutes. No recirculation occurs, so the artery cannot re-light. ⸻ Practical Surgical Insight (TLH assistant style) ???? When you want to see the uterine artery again: You often need: Another small bolus of ICG (1–2 mL). Because: • The fluorescence is momentary • It is meant for identification, not continuous mapping Most surgeons prefer repeated small boluses at critical steps: • Skeletonization of uterine artery • Confirmation of ureteric safety • Checking perfusion after hysterectomy ⸻ Final Summary ICG does not stay in the uterine artery for more than 2 minutes because: • It is rapidly washed out by high uterine blood flow • It diffuses into capillaries immediately • It has a very short plasma half-life • NIR imaging shows only the dye transit, not retention • It is cleared by the liver quickly This is normal ICG physiology — not a technical failure. |
