Assessment of collateral circulation in the hand in patients undergoing major cardiovascular surgery: Modified allen test and pulse oximetry vs doppler ultrasound

Abstract

Introduction: Ischaemic injury of the hand following radial artery cannulation although rarely reported is a severe complication. One mechanism of injury is radial artery thrombosis in the absence of adequate ulnar collateral circulation. Allen test is usually performed before a radial artery cannulation. Recently, some authors have proposed the registration of a finger pulse oximetric signal after compression of the radial artery to assess the collateral circulation in the handl. The aim of our study is to compare Allen modified test (AT)* and pulse oxymetry (PO)3 to Doppler ultrasound (DU) considered as the reference method. Patients and Nethods: After approval of our Ethical Commitee, fifty consecutive ASA II-IV patients undergoing CABG or major vascular surgery (34 males / 16 females, age ranged from 26 to 76, mean = 59.2 yrs) gave their informed consent and were tested preoperatively by three investigators. Each investigator performed always the same test and was not aware of the other investigators findings. The first hand tested (right or left) was randomly assigned. A directional 8 MGHZ DU flow probe (DUH 800) was used to assess the functionality of the superficial palmar arch: the collateral circulation was classified in: good (DU+), poor or absent (DU-). Results of AT were classified according to the time of full palmar blush (FPB) after release of the ulnar compression: < 7 set, 7s FPB< 15 set, FPB 5 15 sec. Finger probe of a pulse oxymeter (Nellcor 200) was placed on the thumb and the pulse oximetric signal was registered; after compression of radial artery at the wrist the presence (PO+) or absence (PO-) of signal was recorded. Results: The superficial palmar arch was functional in 89/100 hands at the DU. When AT was compared to DU (Tab.l), AT showed a sensibility of 0.86 and a specificity of 0.54 (PPV = 0.93, NPV = 0.33) when the time accepted to observe a FPB was limited to < 7 sec. When this time increased to < 15 sec., sensibility of AT became 0.99 and specificity 0.27 (PPV = 0.91, NPV = 0.75); consequently, the risk of considering normal collateral circulation according to AT when it was absent, according to DU, increased from 0.46 to 0.73 when time of PBF was increased. When PO was compared to DU (Tab 2), PO showed a sensibility of 0.89 and a specificity of 0.45 (PPV = 0.93, NPV = 0.38). The probability to have a PO+ with a DUwas 0.55. Conclusion: AT and PO do not seem to be accurate in assessing collateral circulation in the hand in patients undergoing major cardiovascular surgery.