Year : 2020 | Volume
: 8 | Issue : 2 | Page : 71--72
Indocyanine green video angiography in vascular neurosurgery
Jaspreet Singh Dil
Editor-in-chief, Journal of Cerebrovascular Sciences National Neurosciences Mission, Adarsha Super-specialty Hospital, Manipal-Udupi, Karnataka, India
Dr. Jaspreet Singh Dil
National Neurosciences Mission, Adarsha Super-specialty Hospital, Manipal-Udupi - 576 101, Karnataka
|How to cite this article:|
Dil JS. Indocyanine green video angiography in vascular neurosurgery.J Cerebrovasc Sci 2020;8:71-72
|How to cite this URL:|
Dil JS. Indocyanine green video angiography in vascular neurosurgery. J Cerebrovasc Sci [serial online] 2020 [cited 2021 Apr 21 ];8:71-72
Available from: http://www.jcvs.com/text.asp?2020/8/2/71/308623
Of the several ground-breaking revolutions in biomedical technology that have driven surgery from the medieval to the advanced, for a vascular neurosurgeon, indocyanine green video angiography (ICG-VA) has definitely been of major importance.
The use of near-infrared ICG-VA intra-operatively was first highlighted by Raabe et al., who published the positive results, and supported the imaging quality, gained from their experience in intracranial aneurysm surgery, having drawn inspiration from its pre-existing application in the assessment of retinal vasculature in ophthalmic surgery.,,
ICG is a near-infrared fluorescent dye, which, when injected intravenously, gets bound to globulins within 1-2 seconds and remains in the vascular compartment. The dye has an absorption wavelength of approximately 805 nm and emission wavelength of approximately 835 nm. When the dye is injected as a bolus, and the operative field is illuminated by a light source which has the appropriate wavelength covering the absorption band of the dye, according to the ICG mode usually pre-set on operating microscopes, the fluorescence of the dye is picked up and transmitted to what is seen on the screen. It takes about 8 seconds from the time of the injection until the arteries begin to fill, and later the veins, and the intensity remains within visible wavelength for about 1–2 min. Other endogenous circulating substances do not fall within the same absorption wavelength and hence are subtracted, allowing the viewer to visualise only the vasculature.
The recommended dosage is 0.2–0.5 mg/kg body weight, maximum not exceeding 5 mg/kg. The recommended bolus dose is 25 mg diluted in 5 ml of distilled water, either as a single dose or as two divided doses. ICG is not metabolised in the body and gets completely eliminated, having a half-life of just 3 min, ensuring minimal toxic effects in the subject.,
With specific relation to intra-cranial aneurysm surgery, what ICG-VA grants the surgeon as well as the patient in those few minutes when it lights up on the screen, is additional certainty. This applies to both during as well as after the procedure.
Without ICG, the surgeon approaches the aneurysm based on what is visualised from a pre-operative digital subtraction angiography and his or her knowledge of the anatomy, and from past operating experiences. Although these are in no way unreliable, as aneurysms were treated surgically even before the advent of ICG-VA, in this era or evidence-based medicine, the availability of real-time intra-operative images provides for excellent navigation and allows one to confirm several things. It has made it possible to properly identify the aneurysm neck and dome, study the direction of flow and visualise the parent feeding vessel and surrounding perforating vessels, factors that are all crucial before the clip is applied to the aneurysm.
Once the clip has been applied, ICG-VA provides the advantage of immediate re-evaluation and allows one to rule out the inclusion of the parent vessel or other vessels in the clip, which if occurs, may lead to disasters post-operatively. Hence, if a clip is to be re-adjusted, it may be done with more accuracy, although literature indicates that the use of ICG-VA has reduced the rate of clip adjustment in aneurysm surgery, except in few instances. All of the above points to decreased complications such as aneurysm rupture and suboptimal or incorrect occlusion of aneurysms, which cause the most serious and potentially avoidable complications from aneurysm surgery.,
Several surgeons have published positive and encouraging results from their use of ICG-VA.
Dashti et al. reported that following the use of ICG-VA in 239 patients, unexpected neck residuals and unexpected branch occlusions occurred only in 15% each, and there were no instances of incomplete occlusions.
Li et al., reported good results from their experience with 120 patients, with no ICG related complications in any case. ICG aided in clip adjustment and the alteration of the post-operative condition of ten patients who could have otherwise had malpositioned clips. Similarly, Roessler et al., in their series with 295 aneurysms, reported that ICG-VA allowed for significant clip modification.
Catapano et al. have also described in great detail, the use of endoscope integrated ICG which has several advantages of the microscope-integrated ICG, and its applications not only in vascular surgery but also in endonasal, ventricular and tumor surgery.
On other occasions, ICG-VA is also a very helpful tool of rescue for the surgeon in situations when one requires a quick decision in the face of an unexpected scenario when operating on arteriovenous malformations and other vascular lesions.
As with all things that exist, ICG has certain limitations, such as, restriction of the area that can be visualised at a single point of time, and difficulty in visualising very small aneurysms. However, its reliability has been widely supported despite these few shortcomings.,,,,,,,
It is safe to say that every neurosurgeon should familiarise themselves with the technique of ICG-VA, not only for safe practice and good outcome but also to enjoy the exemplary developments in this field.
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