1 Kingston upon Thames, UK 2 Manchester, UK.
EditorI refer to the report of digital ischaemia after ulnar artery cannulation.1 As doubt has been cast on the reliability of the Allens test, it is my practice always to assess the capacity of the palmar arch to be filled from the ulnar artery before placing a radial artery catheter. This test, which I learned in the USA 20 years ago, is very simple but seems to be virtually unknown in the UK. A Doppler probe is placed over the palmar arch near the base of the thumb and a good signal obtained. The radial artery is then occluded by digital pressure. The signal diminishes but, if it disappears, I do not place a radial cannula on that side. I suggest that if this test had been done in reverse, the problem described by Mastan1 may have been averted. While no test is 100% reliable, this one is intuitively sound. I feel that it does give the patient an additional protection against ischaemia, especially to the essential thumb. Maybe it also provides a little of medicolegal protection, provided that the test is properly documented.
In addition, in the letter, unless any alternative is available should surely have read unless no alternative is available.
I. Sinton
Kingston upon Thames, UK
EditorThank you for the opportunity to reply to Dr Sinton. In essence, Dr Sinton advocates a variation on the Allens test, using Doppler ultrasonography. We thank him for sharing this with us. In our original letter, we did allude to the possible usefulness of Doppler studies prior to arterial cannulation.
We also thank Dr Sinton for correcting the typographical error in our letter.
M. Mastan
C. Van Oldenbeek
Manchester, UK
References
1 Mastan M, Van Oldenbeek C. Digital ischaemia after ulnar artery cannulation. Br J Anaesth 2003; 90: 111