Intraoperative confirmation of ulnar collateral blood flow during radial artery harvesting using the "squirt test"

Is radial artery Doppler scanning mandatory for use as coronary bypass conduit?

BACKGROUND

Screening of the radial artery prior to harvesting as a conduit for coronary bypass may be performed clinically by the Allen test or by Doppler ultrasound. In a developing country like ours, the use of resources for Doppler studies may be questioned when Allen tests lead to a low rate of clinical sequelae. However, the rare occurrence of hand ischemia may be devastating and could justify the routine use of Doppler screening. This study aimed to address this question.

METHODS

One hundred patients undergoing elective coronary artery bypass grafting were screened by the modified Allen test and Doppler ultrasound for suitability of use of a radial artery conduit. After harvesting, proximal and distal segments of the radial artery were subjected to histopathological examination.

RESULTS

Of the 95 patients deemed suitable for radial artery grafting, 6 had mild calcification on Doppler ultrasound and 9 had calcification on histopathological examination. While Doppler showed atherosclerosis in 9 patients, only 6 had histopathological evidence of this (false-positive rate 3%). Of the 6 patients with histopathologic evidence of atherosclerosis, 2 were negative on Doppler (false-negative rate 2%).

CONCLUSION

Routine preoperative Doppler screening of the radial artery in the setting of limited resources is not justified. On the other hand, the time-tested Allen test which is easy to perform, interpret, and reproduce can be safely used as the sole screening test to harvest the radial artery.

Intraoperative Pressure Measurement in Radial Artery Harvest. A Tool with Additional Value?

Objectives:

The radial artery is widely used as a graft in coronary artery bypass surgery (CABG). Due to its location and function it should be screened prior to harvesting to avoid ischaemic complications of the hand. In acute situations the Allen test is often the only preoperative screening method available. As has been noted earlier, a negative Allen test does not mean a non-harvestable radial artery. We endeavoured to find out whether intraoperative pressure measurement could be used as a complement while screening the radial artery.

Design:

Ninety patients planned for elective CABG with radial artery as a conduit were examined preoperatively with the Allen test, handheld Doppler and pletysmography of the second and fourth digits. Radial artery pressure was measured intraoperatively. Symptom scale was recorded pre- and postoperatively.

Results:

There were ten patients with a positive Allen test. The intraoperative index of radial artery pressures was 0.868 in the Allen positive group and 0.885 in the Allen negative group with no statistically significant difference (P value .68). Tolerance of exercise and cold was significantly impaired postoperatively, P values .002 and .001 respectively. No ischaemic complications occurred.

Conclusions:

Intraoperative pressure measurement can be used when screening radial arteries are to be harvested and no metric preoperative screening methods are available.

Radial artery cannulation: a comprehensive review of recent anatomic and physiologic investigations

Consistent anatomic accessibility, ease of cannulation, and a low rate of complications have made the radial artery the preferred site for arterial cannulation. Radial artery catheterization is a relatively safe procedure with an incidence of permanent ischemic complications of 0.09%. Although its anatomy in the forearm and the hand is variable, adequate collateral flow in the event of radial artery thrombosis is present in most patients. Harvesting of the radial artery as a conduit for coronary artery bypass grafting, advances in plastic and reconstructive surgery of the hand, and its use as an entry site for cardiac catheterization has provided new insight into the collateral blood flow to the hand and the impact of radial arterial instrumentation. The Modified Allen's Test has been the most frequently used method to clinically assess adequacy of ulnar artery collateral flow despite the lack of evidence that it can predict ischemic complications in the setting of radial artery occlusion. Doppler ultrasound can be used to evaluate collateral hand perfusion in an effort to stratify risk of potential ischemic injury from cannulation. Limited research has demonstrated a beneficial effect of heparinized flush solutions on arterial catheter patency but only in patients with prolonged monitoring (>24 h). Conservative management may be equally as effective as surgical intervention in treating ischemic complications resulting from radial artery cannulation. Limited clinical experience with the ultrasound-guided arterial cannulation method suggests that this technique is associated with increased success of cannulation with fewer attempts. Whether use of the latter technique is associated with a decrease in complications has not yet been verified in prospective studies. Research is needed to assess the safety of using the ulnar artery as an alternative to radial artery cannulation because the proximity and attachments of the ulnar artery to the ulnar nerve may potentially expose it to a higher risk of injury.