Why Is My Dog 's Capillary Refill Time Increased ?
Why Is My Cat 's Capillary Refill Time Increased ?
To see what normal blood and urine values are for your pet, go here
For an explanation of causes of most abnormal blood and urine tests go here
To see how tests are often grouped, go here
Ron Hines DVM PhD
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Your Pet’s Capillary Refill Time
A simple but very informative test that your veterinarian often performs is an examination of the pink portions of your pet’s gums.
The first thing looked for is color – dogs and cats that are anemic will have pale gums. That observation is often followed with a finger pressed firmly against the gum surface. When that pressure is released, the pink color will return. How long it takes to return is your pet/s capillary refill time (CRT). It should be less than two seconds (preferably less than 1.5 seconds).
How fast the gum capillaries of your dog or cat refill (CRT) after that finger pressure is removed depends on how well blood is circulating in the pet's body. It is a crude but useful test - best used only to confirm your veterinarian’s general impressions as to the seriousness of your pet’s health issue.
The longer the CRT, the more worrisome the problem could be.
During that initial assessment, your pet’s heart rate/pulse and rhythm, heard through a stethoscope and felt in the pet’s groin is usually the veterinarian’s next observation.
All three help gauge the adequacy of your pet's blood flow circulation (peripheral perfusion). All pets with extended CRT times are not delivering sufficient oxygen to their tissues (tissue hypoxia).
Long CRT times are often due to a decrease in your pet's blood volume.
The two most common causes for that are dehydration and shock (hypovolemic shock).
(Chronic, mild dehydration is most common in cats consuming dry cat foods. The signs, as in humans, can be nebulous (vague) and only significant over time [ref1 , ref2, ref3]. More severe dehydration can accompany any disease in which apathy or reduced mobility occurs.)
Dehydration could be due to things like heat stroke, prolonged fever, inability to drink fluids or excessive fluid loss as in diarrhea and vomiting.
Hypovolemic shock has many causes, some toxic, some infectious, some allergic (anaphylaxis), some traumatic as in a car accident.
In all of them, the pet’s pulse will also be weak, its respiration will be rapid and its heart rate will be increased. When dehydration is the cause, the gums of your pet tend to be dry and their skin, when pulled upward, is slow to spring back to normal.
Another common cause of increased CRT times are problems related to the heart. Those pets also have a weak pulse and a fast heart rate. It could be the slowly-progressive congestive heart failure of older pets, or sudden cardiomyopathy that occurs in midlife pets. In all forms of heart disease, the problem is the pet’s loss of its ability to maintain blood flow (decreased peripheral perfusion).
Medication overdoses can also cause abnormal slow heart rhythm (bradycardia) leading to an increased CRT. Some drugs that have that ability are beta blockers like Atenolol (Tenormin) and propranolol (Inderal), calcium channel blockers like diltiazem (Cardizem), digoxin (Lanoxin, Cardoxin ), pimobendan (Vetmedin), various narcotics as well as insecticide poisoning (organophosphate type)