Capillary refill time has been accepted as a method to manually assess a patient's peripheral blood perfusion. Recently, temperature has been reported to affect capillary refill time and therefore temperature may interfere with accurate bedside peripheral blood perfusion evaluation. We applied a new method of analysis that uses standard hospital pulse oximetry equipment and measured blood refill time in order to test whether lowered fingertip temperature alters peripheral blood perfusion. Thirty adult healthy volunteers of differing races (skin colors) and age (young: 18-49 years and old: ≥ 50 years) groups were recruited. We created a high fidelity mechanical device to compress and release the fingertip and measure changes in blood volume using infrared light (940 nm). Capillary refill times were measured at the fingertip at three different temperature settings: ROOM TEMPERATURE, COLD by 15 °C cold water, and REWARM by 38 °C warm water. The COLD group has decreased fingertip temperature (23.6 ± 3.6 °C) and increased blood refill time (4.67 s [95% CI 3.57-5.76], p < 0.001). This was significantly longer than ROOM TEMPERATURE (1.96 [1.60-2.33]) and REWARM (1.96 [1.73-2.19]). Blood refill time in older subjects tended to be longer than in younger subjects (2.28 [1.61-2.94] vs. 1.65 [1.36-1.95], p = 0.077). There was a negative correlation (r = - 0.471, p = 0.009) between age and temperature. A generalized linear mixed-effects model revealed that lower temperature (OR 0.63 [95% CI 0.61-0.65], p < 0.001) rather than age (OR 1.00 [0.99-1.01], p = 0.395) was the independent factor most associated with increased blood refill time. Lowered fingertip temperatures significantly increase blood refill time which then returns to baseline when the fingertip is rewarmed. In our limited number of population, we did not find an association with age after the adjustment for the fingertip temperature.
Keywords: Blood refill; Capillary refill time; Monitoring; Peripheral blood perfusion; Shock.