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.