DISCUSSION:
Easy access and low complication rates have resulted in the radial artery being the most popular site for arterial cannulation. The most common reported complication is temporary arterial occlusion with a mean incidence of 19.7%(1). Serious ischaemic injury resulting from permanent occlusion is, however, rare (mean incidence 0.09%) but the potential consequences of necrosis and finger amputation are significant(1). The benefits of monitoring with arterial catheterisation are obvious but must be balanced against the associated risks and should outweigh the potential harms. It has been shown that the incidence of radial artery occlusion increases linearly with the ratio of outer diameter of the arterial catheter to vessel lumen diameter. This may explain the higher incidence in females and the preference for using narrow lumen catheters(2, 3). Other risk factors include low body mass index, advanced age, vascular disease, prolonged peri-procedural hypo- and/or hypertension, vasopressor use, catheter composition, prolonged catheter placement and excess trauma from multiple attempts at the same site(4, 5). It is possible that risk factors, such as low body mass index, advanced age, vascular disease and female gender, may have contributed to the temporary occlusion in both patients outlined above.
Radial artery occlusion (RAO) is the most frequent post-procedural complication of transradial access in cardiac catheterisation(6). This can have significant clinical implications, such as, precluding the use of the ipsilateral radial artery for future procedures and as a conduit for coronary artery bypass grafting or for arteriovenous fistula creation in patients requiring haemodialysis. Therefore, prevention is of upmost clinical importance. During radial haemostasis, complete cessation of blood flow with “occlusive” compression promotes thrombus formation and is a strong predictor of RAO (7). In the PROPHET trial , the ‘patent’ or nonocclusive haemostasis protocol, was compared with to conventional pressure application for haemostasis after transradial diagnostic coronary angiography. The patent haemostasis technique was associated with a significant decrease in early (<24hour) RAO rates from 12% to 5% and late RAO rates (30 days) from 7% to 1.8% (8). Similarly, in the RACOMAP trial, patent haemostasis was performed with a pneumatic compression device in which compression was guided by mean arterial pressure (maintaining thereby flow within the radial artery during haemostasis), demonstrating also a significant decrease in RAO rates from 12.0% to 1.1% (9). Despite being simple and inexpensive non-pharmacological method of preventing RAO, it requires significant involvement of the nursing staff due to the need for repeated oximetry-plethysmographic evaluation of radial flow and frequent adaptation of the haemostatic pressure to ensure ongoing vessel patency. As such, there is still limited adoption of the technique worldwide(10).
The consequences of RAO are generally benign when managed appropriately in a timely manner. A cold, pale hand or fingers with reduced motor function, sensory deficit or pain following radial artery cannulation should be immediately investigated. Management options include medical and/or surgical intervention. If ischaemia is suspected, the catheter should be removed immediately and the affected limb elevated and warmed. Anticoagulant, thrombolytic and vasodilator therapy may be indicated if there is a perceived risk of progressive ischaemia following these conservative measures. Some cardiology data suggests that immediate treatment with 5,000 IU intravenous heparin combined with compression of the ipsilateral ulnar artery for 1 hour or, alternatively, body-weight-adjusted therapeutic dosing of enoxaparin or fondaparinux for 4 weeks may help recanalise the radial artery(11). Some case reports have described successful recanalisation of the occluded radial artery with angioplasty (12, 13). In certain cases, thrombectomy, surgical bypass or cervical sympathetic blockage should be considered. However surgical intervention in the setting of iatrogenic radial arterial thrombosis is uncommon(14).
There is strong evidence for the use of ultrasound guidance in radial artery catheterisation in both adult and paediatric populations. Ultrasound guidance significantly increases first-attempt success rate, which subsequently results in a significant reduction in the number of attempts(15). The early use of ultrasound can be a valuable adjunct in radial arterial catheterisation and should be considered, especially in predicted difficult cases.
The Allen’s test or modified Allen’s test are bedside tests that can be performed in patients undergoing radial artery puncture. The hand is perfused by both the radial and ulnar arteries with extensive collateral flow between the two. However, some patients have incomplete palmar arches, which may diminish collateral perfusion, possibly leading to hand ischemia in the presence of RAO. Although rarely performed in practice, identifying collateral flow to the region supplied by the artery can be useful prior to puncture. While limited studies have found variable accuracy associated with such evaluations, it is believed that patients, and in particular high risk patients, undergoing radial artery puncture should have the collateral flow to the vessel evaluated(16, 17). Finger pulse plethysmography, Doppler flow measurements, and measurement of the arterial systolic pressure of the thumb have been described but are not routinely used(18).
CONCLUSION:
Radial arterial occlusion resulting in compromised circulation to the hand/fingers during the placement of an indwelling arterial catheter at the time of surgery is a rare phenomenon but has significant potential consequences. Consideration should be given to utilising a reliable test to establish patency of the palmar arch. Furthermore, all patients should be examined for radial artery patency before discharge. Novel studies and techniques are needed to improve strategies that minimise the incidence of this major complication of radial access. We describe two such cases in which timely recognition of this complication contributed to successful management, with both patients making a full recovery.