The association between capillary refill time and arterial flow in the pediatric upper extremity

Measurement of capillary refill time (CRT) is thought of as a fast and inexpensive tool for assessing perfusion to an extremity or digit. CRT is frequently relied upon by orthopedic surgeons, especially in the postoperative period when pulses may be inaccessible owing to casts or dressings. Yet to our knowledge, no study has attempted to correlate CRT with other indices of perfusion to the extremity. We evaluated the association between CRT and arterial flow in pediatric upper extremities. Our hypothesis was that arterial flow would be inversely proportional to CRT--that decreased perfusion would be associated with prolonged CRT. Ten children between the ages of 8 and 17 years with no systemic or upper extremity abnormalities were studied. Radial and ulnar artery flows were evaluated with Doppler ultrasound. Measurements of the radial and ulnar flow volumes were summed, to approximate total flow to the extremity. CRT was measured to the tenth of a second with the use of digital video. Three sets of the above measurements were taken for each participant--at baseline and at two levels of decreased perfusion (produced by inflating a blood pressure cuff to 25 and 75 mmHg). Linear regression was used to analyze the data. A lack of correlation was found between arterial flow and CRT (r=0.02, P=0.93). Though the study has its weaknesses, the results caution the use of CRT as a solitary measure of perfusion in children. This was a level 1 diagnostic study.