What limits the use of capillary refill time (CRT) as an assessment tool in most rodents?

Using capillary refill time (CRT) as an assessment tool in rodents is limited primarily due to their small size. In smaller animals, like many rodents, it can be challenging to accurately assess CRT because the capillaries are very close to the surface, and small fluctuations in blood flow can cause significant variations in refill time. The small surface area means that it is more difficult to capture the accurate timing of capillary refill, making the results less reliable.

While other factors such as high heart rate, low blood pressure, and rapid breathing can affect blood circulation and potentially influence CRT, the primary concern with using this technique in rodents relates to the difficulties posed by their overall small size. This makes it less effective compared to larger animals, where the assessment is more straightforward and accurate.