Popliteal artery cannulation as a saviour during prone positioning
- Narayan Bala ,
- Vinay Pathak ,
- Shilpa Goyal and
- Nikhil Kothari
- Department of Anaesthesiology & Critical Care, All India Institute of Medical Sciences, Jodhpur, Rajasthan, India
- Correspondence to Dr Nikhil Kothari; drnikhilkothari@gmail.com
Abstract
The cannulation of the peripheral artery is a prerequisite for invasive blood pressure monitoring and repeated arterial blood gas sampling. Radial artery is commonly used site for inserting an arterial cannula. Many times, either during the change of posture or during prone ventilation, the arterial cannula gets displaced, and it is challenging to reinsert the arterial cannula in the lateral or prone position. In such circumstances, an alternative site of arterial cannulation needs to be looked into; we report a case in which the popliteal artery was used for arterial cannulation while the patient was in a prone position.
Background
Arterial cannulation is a prerequisite for invasive blood pressure monitoring. If the patient is in a prone position, it is challenging to access the arterial line. In such cases, alternative places should be preferred, like the popliteal artery.
Case presentation
The cannulation of an artery is commonly performed in acute and critical care settings as well as during mechanical ventilation for blood pressure monitoring. It serves as an invasive means to accurately measure the mean arterial pressure. There are different sites for arterial cannulation such as a radial artery, femoral artery, dorsalis pedis artery and posterior tibial artery.1 Radial artery being the preferred site in most cases, due to easy accessibility of this site.2
Studies have shown that prone positioning during mechanical ventilation has a mortality benefit in patients with severe acute respiratory distress syndrome (ARDS).3 While turning the patients prone during mechanical ventilation, dislodgement of the endotracheal tube, pulling out of drains or invasive lines are common complications. Reinsertion of invasive lines in the prone position is a nightmare for intensivists. We report a case of popliteal artery cannulation for invasive blood pressure monitoring in a patient with ARDS, whose radial arterial line got displaced while turning the patient for the prone position.
A 59-year-old male patient, postoperative case of robot-assisted radical cystectomy with ileal conduit formation for carcinoma bladder, was shifted to intensive care unit (ICU) for elective ventilation. The patient aspirated in the anaesthesia care recovery unit, following which his lung compliance worsened, and chest radiograph showed bilateral symmetrical opacity, indicating the possibility of ARDS after aspiration. Over the next 2 days, the positive end-expiratory pressure requirement went up to 12 cm of water, and the fractional oxygen requirement (FiO2) was 0.8. The Arterial Blood Gas (ABG) showed partial pressure to FiO2 (PaO2/FiO2) ratio of <100; thus, the diagnosis of severe ARDS was made, and the patient was planned for prone ventilation. After positioning the patient prone, it was found that the right radial arterial line was damped with no backflow. Attempts to secure the arterial line in the radial, dorsalis pedis and posterior tibial artery failed due to the prone position of the patient. Therefore, another alternative site to secure an arterial line was searched. During the process of screening using a high-frequency ultrasound probe, the popliteal artery was found pulsating brightly just 3 cm below the skin. Thus, ultrasound-guided popliteal artery cannulation was planned. After obtaining informed written consent from the patient attendants, pre-procedure ultrasonography was done to assess the anatomy of the popliteal artery in the region of the popliteal fossa. Under all aseptic precaution, with ultrasound assistance, an 18-gauge needle was inserted in the left popliteal artery using the in-plane approach, and the guidewire was inserted through the needle (Seldinger technique). The position of guidewire inside the left popliteal artery was confirmed by ultrasonography, and a 20-gauge arterial cannula (Vygon) was threaded over the guidewire. After removing the guidewire, the backflow through the catheter was confirmed by the pulsatile backflow of blood through the catheter and by the arterial waveform on the monitor. The arterial catheter was then secured using silk sutures (figure 1).
Fixation of popliteal artery catheter using silk sutures.
Outcome and follow-up
After 2 days, ARDS was resolved, and the popliteal artery catheter was removed.
Discussion
Invasive arterial line helps in continuous haemodynamic monitoring and for arterial blood gas analysis in the ICU. Intra-arterial blood pressure monitoring permits beat to beat tracking and rapid recognition of blood pressure changes those are vital for patients while on continuous infusion of vasoactive drugs.4 5 Invasive monitoring also displays arterial pressure waveforms, which can be used for better analysis of clinical scenarios and fluid shifts. However, invasive monitoring has its own limitations. It requires technical expertise and can lead to severe complications when compared with non-invasive techniques. These complications can vary from pseudoaneurysm formation, vasospasm of arteries, ischaemia of digits to inadvertent intra-arterial drug injection.
The most common site for arterial cannulation in the lower limb is the femoral artery. The average vascular diameter of the proximal femoral artery is 1.02 cm, and the rate of blood flow is 353 mL/min.6 7 As we move down the limb, the diameter of the artery is reduced, and it becomes narrow. The diameter of the posterior tibial artery is 0.38 cm, and that of dorsalis pedis artery is 0.30 cm, both of these arteries are used regularly as an alternate site for cannulation in the lower limb. On the contrary, the popliteal artery having a diameter of 0.69 cm and with a blood flow of 61.9 mL/min; though commonly used for non-invasive blood pressure monitoring, but is never being explored for arterial cannulation, probably due to its anatomical location on the posterior aspect of the knee joint.8 9 As per the available literature, the popliteal artery is used mainly for percutaneous endovascular procedures.10
The prone ventilation has now become one of the established treatment modality in cases of severe ARDS, and it is being practised widely all over the world. In certain inevitable situations where there is limited access to other arteries, and there is a need for continuous haemodynamic monitoring while the patient is in the prone position, the popliteal artery can be considered as an alternative site for arterial cannulation. The most specific complication of retrograde popliteal artery catheterisation is arteriovenous fistula, due to posterior location of the popliteal vein relative to the artery and an arterial puncture with the patient in the prone position having the risk of traversing the vein. This can be avoided with an appropriate imaging tool like ultrasonography for cannulation.
Another important possible complication of popliteal artery cannulation is the ischaemia of distal limb due to embolism. So the distal pulse checks, blackish discoloration of foot, capillary refill time should be assessed frequently. This can be managed by either intra-arterial thrombolysis or aspiration and balloon dilation followed by oral anticoagulation.10
Conclusion
The ultrasound-assisted popliteal artery cannulation can serve as an efficient alternative for arterial cannulation in a prone position where access to other arteries for cannulation is difficult and tedious.
Learning points
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The cannulation of the peripheral artery is a prerequisite for invasive blood pressure monitoring and repeated arterial blood gas sampling.
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The ultrasound-assisted popliteal artery cannulation can serve as an efficient alternative for arterial cannulation in a prone position where access to other arteries for cannulation is difficult and tedious.
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The possible compilation of popliteal artery cannulation is arteriovenous fistula which can be decreased by sonography-guided insertion.
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Distal pulse, any discoloration of foot, capillary refill time should be assessed frequently as distal limb ischaemia is one of the complications.
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Written informed consent should be taken from the patient or patient’s relatives by explaining the possible risks and benefits of the procedure.
Footnotes
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Contributors NB has written the manuscript; has taken the photograph during the procedure and took the consent from the patient. VP has helped NB in writing the manuscript. SG has independently reviewed the manuscript, evaluated the scientific content, did grammatical corrections and edited the text. NK is the corresponding author. He gave the idea of cannulating the popliteal artery and he performed the arterial cannulation. He has also edited the manuscript from 2000 words to 1164 word and reviewed the manuscript.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Competing interests None declared.
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Patient consent for publication Next of kin consent obtained.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.
References
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