This chapter is vaguely relevant to Section G7(iii) of the 2017 CICM Primary Syllabus, which asks the exam candidate to "describe the invasive and non-invasive measurement of blood pressure, including
limitations and potential sources of error". It is also vaguely related to Section X(ii), "describe the anatomy relevant to the insertion of an arterial line into a brachial, axillary, posterior tibial, dorsalis pedis, radial or femoral artery". None of the Part I questions have so far tested the candidate's ability to wisely select a correct insertion site, perhaps recognising that there are many different ways to skin a cat. However, Question 11.1 from the first Fellowship paper of 2021 asked for advantages and disadvantages of radial brachial and femoral arterial sites.
There is no specific literature to guide decisionmaking in this area. Most of the material presented here is derived from "Chapter 3: Arterial line placement and care" from Irwin and Rippe's Intensive Care Medicine (7th Ed), by Lee-Llacer and Seneff. Site selection is guided as much by the effects we don't want as by the desired effects, and valuable reading about site-specific complications should include the excellent reviews by (Scheer et al, 2002; Frank et al,1983). . The chapter by Abide & Meissen (2021) from Interventional Critical Care is also superb.
In short:
The ideal site for arterial catheter placement would have the following characteristics:
- Large
- Proximal
- Extensive collateral circulation
- Comfortable for the patient
- Accessible for nursing care and insertion
- Unaffected by infection or trauma
- Not in the way of any other planned procedure (eg. a radial artery harvest for CABG)
- Close to the monitoring equipment (if it cannot be repositioned)
Potential sites typically used in adults include:
- Radial artery
- Femoral artery
- Axillary artery
- Dorsalis pedis artery
- Brachial artery
Less typical sites can include:
- Ulnar artery
- Axillary artery
- Superficial temporal artery
However, everyone still ends up getting a radial arterial line. This is because the balance of risk and benefit favours the radial artery as the first choice for arterial catheterisation. Each site has its advantages and disadvantages, with respect to ease of nursing access, patient comfort, the accuracy of measurement and difficulty of cannulation; and rates of serious complications are similar for all sites. In the neonatal setting, the umbilical artery is a unique access point that also needs to be mentioned. Theoretically, any peripheral artery can be accessed for arterial pressure measurement.
In summary:
Site | Radial | Brachial | Femoral |
Advantages |
|
|
|
Disadvantages |
|
|
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Complications |
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General complications for all sites
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Scheer et al (2002) were able to compute the mean incidence of serious complications associated with arterial line insertion, for the two most common sites of insertion:
Site |
Permanent ischaemic damage |
Temporary occlusion |
Sepsis |
Local infection |
Pseudoaneurysm |
Radial |
0.09% |
19.7% |
0.13% |
0.72% |
0.09% |
Femoral |
0.18% |
1.45% |
0.44% |
0.78% |
0.3% |
Thus, though the radial artery has a far higher rate of thrombotic occlusion, the risk of serious ischaemic complications is decreased because of collateral circulation. The risk of local infection is similar for both sites, but the risk of catheter-related sepsis was significantly higher for the femoral insertion site.
Risk factors for complications from arterial cannulation include the following:
Thrombotic occlusion is by far the most common complication at all sites. The radial artery and the dorsalis pedis artery as most prone to thrombotic complications. Scheer et al (2002) found that the rate of thrombosis and temporary occlusion was as high as 19.7% with radial arterial lines, as compared to 1.45% with femoral lines. Thrombosis can also occur following the removal of the line. The vessel recanalises after approximately 3 weeks. This temporary occlusion is usually without serious sequelae, owing to the generous collateral circulation at these sites; less than 1% of cases require surgical intervention. Most patients who develop clinically significant ischemia have some associated contributing cause, such as high-dose vasopressor therapy or severe peripheral vascular disease. The use of a heparinised flush solution is no longer recommended, as it does not appear to be protective against thrombosis and is associated with a risk of heparin-induced thrombocytopenia.
If clinically significant ischaemia is observed, immediate removal of the catheter will minimise the ensuing complications. If ischaemia persists following catheter removal, the following options can be explored:
Cerebral embolisation is a known complication of flushing the arterial line. Retrograde passage of small bubbles of gas into the arterial circulation is possible, considering that the pressure transducer is coupled to a bag with 300mmHg of pressure (i.e. enough to defeat systemic arterial pressure).
Risk factors for clinically significant cerebral gas embolism include the following:
Iatrogenic blood loss is a significant risk of convenient arterial access. Generally, 2-3ml of blood is discarded for each arterial blood gas sample, and daily blood sampling for biochemistry can contribute a further 20-30ml. Smoller et al (1986) found that the total blood lost to phlebotomy in non-ICU patients was approximately 175ml over the whole period of their hospital stay. However in the ICU this increased to 300ml for patients without arterial lines. When the patients had an arterial line, this blood loss rate increased to over 900 ml, with implications for their transfusion requirements.
Lee-Llacer J, Seneff, M. "Chapter 3: Arterial line placement and care." In: Irwin and Rippe's Intensive Care Medicine, 7th Edition. New York: Little, Brown (2007): 36-47.
Pauca, Alfredo L., et al. "Does radial artery pressure accurately reflect aortic pressure?." Chest 102.4 (1992): 1193-1198.
Russell, James A., et al. "Prospective evaluation of radial and femoral artery catheterization sites in critically ill adults." Critical care medicine 11.12 (1983): 936-939.
Scheer, Bernd Volker, Azriel Perel, and Ulrich J. Pfeiffer. "Clinical review: complications and risk factors of peripheral arterial catheters used for haemodynamic monitoring in anaesthesia and intensive care medicine." Critical Care 6.3 (2002): 199.
Thomas, Frank, et al. "The risk of infection related to radial vs femoral sites for arterial catheterization." Critical care medicine 11.10 (1983): 807-812.
Chang, Cherylee, et al. "Air embolism and the radial arterial line." Critical care medicine 16.2 (1988): 141-143.
Durie, M., U. Beckmann, and D. M. Gillies. "Incidents relating to arterial cannulation as identified in 7525 reports submitted to the Australian Incident Monitoring Study (AIMS--ICU)." Anaesthesia and intensive care 30.1 (2002): 60.
Gurman, Gabriel M., and Shelly Kriemerman. "Cannulation of big arteries in critically ill patients." Critical care medicine 13.4 (1985): 217-220.
Russell, James A., et al. "Prospective evaluation of radial and femoral artery catheterization sites in critically ill adults." Critical care medicine 11.12 (1983): 936-939.
Wilkins, R. G. "Radial artery cannulation and ishaemic damage: a review." Anaesthesia 40.9 (1985): 896-899.
Smoller, Bruce R., and Margot S. Kruskall. "Phlebotomy for diagnostic laboratory tests in adults." New England Journal of Medicine 314.19 (1986): 1233-1235.
Abide, Aimee M., and Heather H. Meissen. "Arterial Line Access and Monitoring." Interventional Critical Care. Springer, Cham, 2021. 97-114.