Indian Journal of Vascular and Endovascular Surgery

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 7  |  Issue : 1  |  Page : 18--21

”Geometry-based cannulation technique” for cannulation of great saphenous vein during radiofrequency ablation of varicose veins at a university hospital of Nepal


Robin Man Karmacharya 
 Department of Surgery (Cardio Thoracic and Vascular), Dhulikhel Hospital, Kathmandu University Hospital, Dhulikhel, Nepal

Correspondence Address:
Dr. Robin Man Karmacharya
Department of Surgery (Cardio Thoracic and Vascular), Dhulikhel Hospital, Kathmandu University Hospital, Dhulikhel
Nepal

Abstract

Background: Radiofrequency ablation is an established minimal invasive treatment modality of varicose veins. This technique involves accessing the great saphenous vein (GSV) through which radiofrequency ablation catheter is inserted. Some established puncture techniques like in-plane and out-plane techniques are also not devoid of limitations. Aims and Objectives: To know the applicability of “Geometry based cannulation technique” in terms of mean cannulation attempts and percentage of successful cannulation. Materials and Methods: We are doing “Geometry based cannulation technique” for the cannulation of GSV. For cannulation 18G needle of length 3 cm attached with 10 ml syringe (cannulating needle) partly filled with normal saline is used. Doppler ultrasonography is done with Siemen's Acuson P300 machine with linear probe of frequency 7.5–12 MHz. The depth from the skin to the upper part of vein is measured in cm and is termed as distance “A.” The tip of the cannulating needle is positioned on the middle of the probe and gently pressed down the skin to form the shadow in the Doppler. The needle is readjusted such that the shadow corresponds to the GSV. Then, the needle is moved distally to A distance. Then the needle is made rotated 45° and skin is punctured to the length (distance B) calculated from the Pythagoras theorem as square root of 2A2. Then the angle is decreased to about 30° and further 2–3 mm advancement of the cannulating needle is done such that it lies inside the target GSV. Results: From 459 cannulations in the time frame of August 2013–December 2018, we found that mean cannulation attempts were 1.4 (standard deviation 0.72, 1–3 attempts). In 429 GSVs (95.5%), there were successful cannulations, whereas in 20 GSVs (4.5%), there was failure in cannulation. The cannulation of GSV has higher success if the diameter of GSV is more than 5 mm and the depth is less than 10mm. Conclusion: “Geometry based cannulation technique” for cannulation of GSV is a novel technique and can be used with high success.



How to cite this article:
Karmacharya RM. ”Geometry-based cannulation technique” for cannulation of great saphenous vein during radiofrequency ablation of varicose veins at a university hospital of Nepal.Indian J Vasc Endovasc Surg 2020;7:18-21


How to cite this URL:
Karmacharya RM. ”Geometry-based cannulation technique” for cannulation of great saphenous vein during radiofrequency ablation of varicose veins at a university hospital of Nepal. Indian J Vasc Endovasc Surg [serial online] 2020 [cited 2020 Jun 6 ];7:18-21
Available from: http://www.indjvascsurg.org/text.asp?2020/7/1/18/280669


Full Text



 Introduction



Radiofrequency ablation is a very popular minimally invasive treatment modality of varicose veins. This technique was started at Dhulikhel Hospital, Kathmandu University Hospital since August 2013.[1] This technique has advantages compared to conventional open surgeries in terms of less pain, earlier return to work, less hospital stay.[2],[3],[4] This technique involves accessing the great saphenous vein (GSV) usually around the femoral condyle region or in the calf region through which radiofrequency ablation catheter is inserted by the Seldinger technique. For GSV access, most surgeons prefer puncture technique under ultrasound guidance while some still prefer small incision to expose GSV. Some of the established puncture techniques are in-plane and out-plane techniques during ultrasound guidance. These techniques are not devoid of limitations as they are not made specifically for GSV cannulation. Our vascular surgical team has been doing a novel technique of “Geometry-based cannulation technique” for cannulation of GSV.

On literature review, we have not found a description of similar cannulation technique. This study is aimed to evaluate success percentage of this cannulation technique and also to note the difficulties in the process.

 Methods



All the patients subjected for radiofrequency ablation of varicose veins involving great saphenous system without exclusion criteria from August 2013 to December 2018 at Dhulikhel Hospital, Kathmandu University Hospital are included in the study. Exclusion criteria were recurrent varicose veins (even when short segment radiofrequency ablation [RFA] was done), preexisting skin disease with fibrotic changes in the cannulation area. If RFA was performed in bilateral lower limb, they were included as two patients. This is a single-center and single-surgeon study. Furthermore, the first 10 cases of the operating surgeon were excluded so that the patients during learning curve were excluded. All the patients were kept in supine position with the knee about 15° flexed and hips externally rotated (frog legged position). Before cannulation, Doppler ultrasonography of GSV was done performed a better word? Ideal site of cannulation was chosen following the rule of 5 (at least 5 mm in diameter, <5 mm from skin, 5 cm straight segment and without tributaries) as much as possible. If the GSV segment distal to the distal insufficiency point (DIP) follows the above rule, that site is chosen; otherwise, the GSV segment above DIP is chosen. As far as possible most distal part of GSV is chosen for cannulation which fulfills the above rule.

For cannulation 18G needle of length, 3 cm attached with 10 ml syringe (cannulating needle) partly filled with normal saline is used. Doppler ultrasonography is done with Siemen's Acuson P300 machine with linear probe of frequency 7.5–12 MHz. Appropriate gain and zoom are adjusted to have a reasonable resolution of the tissues. The operating surgeon stands on the right side of the patient for both right and left side RFA with Doppler ultrasonography machine on the right side of the patient [Figure 1].{Figure 1}

For “Geometry-based cannulation technique” the linear probe is held perpendicular to the skin and GSV [Figure 2] such that the target GSV segment is seen with typical Egyptian eye appearance in the middle of the screen.{Figure 2}

The depth from the skin to the upper part of vein is measured in cm and is termed as distance “A” [Figure 3].{Figure 3}

The tip of the cannulating needle is positioned on the middle of the probe and gently pressed down the skin to form the shadow in the Doppler. The needle is readjusted such that the shadow corresponds to the GSV [Figure 4].{Figure 4}

Then the needle is moved distally to A distance. Then the needle is tilted to make 45° angle with the skin and skin is punctured to the length (distance B) calculated from the Pythagoras theorem as square root of 2A 2 which is equal to √2 X A. It will be helpful if that distance is marked in the cannulating needle beforehand. Usually, after this, the tip of the needle is seen just touching the target GSV. Then, the angle is decreased to about 30° and further 2–3 mm advancement of the cannulating needle is done such that it lies inside the target GSV [Figure 5].{Figure 5}

If, in this step, the needle has double punctured the target GSV, gentle pulling of the cannulating needle is done till the back wall just drops down (we term as “curtain lowering” sign). In this position, the needle is usually inside GSV. Further steps of cannulation are done with the insertion of guidewire, then exchanged with dilator inside the sheath, and finally removing the dilator.

In our experience, our method is slightly more complex than conventional techniques to understand and be familiar, but once you are familiar on the calculation and technical details of the procedure we are doing, it will be easier.

Operating definition of success of cannulation

If the tip of the cannulating needle is inside the GSV and on the aspiration of the syringe, there is blood flow without resistance along with the adequate insertion of guidewire.

Operating definition of failure of cannulation

Failure of cannulation is termed if even by multiple attempts at cannulation by the above technique, successful insertion of guidewire cannot be done for which incision and exposure of vein followed by the insertion of RFA catheter by open technique is required.

Operating definition of attempts of cannulation

Attempts of cannulation are defined as the number of times the skin is pricked to have successful cannulation. Here, the needle should be completely out of the skin after one failed attempt to be called as next attempt.

 Results



There were 449 limb eligible for the study. Mean GSV diameter was 7.41 mm (standard deviation [SD] 3.14, 3–15 mm) There were 84 GSV (18.7%) of size smaller than 5 mm, 261 GSV (58.1%) of size between 5 mm to 10 mm and 104 GSV (23.2%) of size more than 10 mm. The mean distance of GSV from skin was 4.8 mm (SD 2.3 mm, 1–15 mm). There were 144 GSV with distance <3 mm from skin, 145 GSV with distance between 3 mm and 5 mm and 139 GSV with distance 5–10 mm and 21 GSV with distance more than 10 mm.

Mean cannulation attempts were 1.4 (SD 0.72, 1–3 attempts). In 429 GSVs (95.5%), there were successful cannulations whereas in 20 GSVs (4.5%), there was failure in cannulation.

As shown in [Table 1], in group with GSV <5 mm, mean cannulation attempts were 2.5 while that in group with GSV size between 5 and 10 mm was 1.2 and that in group with size more than 10 mm, it was 1 (P < 0.01 ANOVA test). P < 0.01 while comparing between all the groups.{Table 1}

As shown in [Table 2], on analysis of cannulation attempts in relation to depth of GSV, it was 1.1 in-depth <3 mm, 1.1 in-depth 3–5 mm, 1.6 in-depth 5–10 mm and 3.0 in-depth more than 10 mm (P < 0.01 ANOVA test). On post hoc test, P value was significant between all four groups except between <3 mm and 3–5 mm group.{Table 2}

On analysis of the success of cannulation with diameter of GSV, all the cannulation was successful in diameter more than 10 mm group. In diameter between 5 and 10 mm group there were 10 unsuccessful cannulation (3.8%, n = 261) while in diameter <5 mm, there were 10 unsuccessful cannulation (11.9%, n = 84). P = 0.01 in comparison of all the groups.

On analysis of success of cannulation with depth of GSV, all the cannulation was successful in depths <3 mm and 3–5 mm. However, in depth of GSV 5 mm to 10 mm, there were 10 unsuccessful cannulation (7.19%, n = 139). In depth of GSV more than 10 mm, there were 10 unsuccessful cannulation (47.61%, n = 21). P = 0.01 in comparison of all the groups.

 Discussion



Radiofrequency ablation is an established minimal invasive treatment modality of varicose veins of GSV. This involves the insertion of RFA catheter in the desired segment of GSV by Seldinger technique. The cannulation of GSV in the desired region is a technical skill that all involved surgeons should know properly. There is a lack of appropriate studies on technical details of cannulation of GSV.

Ultrasound-guided puncture of veins has been found to increase the safety, know the anatomy and patency of vessels and is indispensable in regions where there is the variability of vessel locations or if the vessel location is deep.[5] A unique cannulation technique has been discussed in our article. In ultrasound-guided access to any deep structure, two common approaches are popular notably in-plane and out-plane techniques.

In in-plane approach, the ultrasound probe is positioned parallel to the vessel, and the needle enters from the side of the probe. The whole entered shaft of the needle is visualized, and the target can be punctured. However, in case of GSV cannulation, the artifact of the needle blocks the view of GSV, and puncturing small GSV can be difficult. Furthrmore, in case of some tortuosity of vessel, it might be difficult to position probe exactly parallel to vessel.

In out-of-the-plane approach, the needle is inserted away from the probe and is aimed at the plane of ultrasound. In this technique, only the tip of the needle is visualized. Out of the plane, technique is quite similar to our “Geometry-based cannulation technique.” However, some notable differences in our technique are that the angle of puncture and distance the needle is inserted is mentioned. As vascular access requires pinpoint precision such that the needle tip is inside the vessel and not just touching the vessels, the details on the angle and the distance the needle is inserted are very important.

In vascular access, out-of-the-plane technique is more popular. In studies comparing the two techniques for cannulation of axillary vein, out-of-the-plane technique has been found to have significantly more successful first attempt cannulation, less needle redirection, and shorter duration of the procedures.[6]

In out-of-the-plane technique, different angles of puncture have been proposed and can be classified as steep angle and shallow angle.[7] Both has its own advantage and disadvantages. In steep angle, there is an earlier visualization of the needle, but there is more chance of posterior wall puncture.[7] In swallow angle, there is late visualization of the needle, but there is less chance of posterior wall puncture.[7] There is a lack of description of how far the needle should be positioned and at what angle the needle should be directed and to what distance it should be directed. These all descriptions form our “Geometry based cannulation technique.”

In our series, GSV diameter more than 5 mm and depth <5 mm has the best results with 100% cannulation rate and almost only single cannulation attempt. As the diameter decreases, the cannulation attempt increases and can also have some failure in cannulation. Similarly, as the depth from the skin increases, the cannulation attempt increases and has some failure in cannulation. In the subgroup with the depth is more than 1 cm, the cannulation attempt is highest, and the failure of cannulation is also the highest. These suggest in some selected cases, open cannulation is also indicated as multiple failed cannulation might result in venous spasm, local hematoma further making cannulation difficult, and prolonging the procedure.

A similar study with randomization of cannulation technique to our technique, in-plane and out-plane technique will help to ascertain more details on the merits and demerits of the different techniques.

 Conclusion



This novel technique of ultrasound-guided cannulation of GSV has high successful cannulation, especially if the diameter of GSV is more than 5 mm, and the depth is <10 mm. This geometrical approach can be used during RFA of varicose vein with high success rate.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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