Susan Garlinghouse at AERC Convention

["guest@endurance.net" <guest@endurance.net>]

Arthur B. King DVM arthur.king @sympatico.ca
Those of you who attended Susan Garlinghouse's session at the AERC convention may recall that during the question and answer period a rider described a situation where someone had blood tested her horse during or after a ride and said that the blood potassium level was so high thatit was a wonder that the horse did not die. the rider thought that she may have overdosed her horse with potassium. this is very unlikely. the daily ration for a horse contains several hundred times the needs of potassium for ahorse. It is very difficult to get a horse to absorb more potassium form its gut than it would require and even if the blood level does get too high the kidney will excrete the excess. 
susan's reply was basically tha the rider needed to pay attention to the balance nd amount of electrolytes that are beign administered during the ride. This is very true. however it is very unususl to get ahorse with a potential lethal level of potassium in its bloos stram by oral dosing of potassium.  
I wish that I had spoken with that rider when they asked the question but I did not. I knew at the time that there was something wrong with this story but I didn't figure it out until I spoke with Gayle Ecker.
What probably happened is that when the blood sample was taken the blood cells were not immediately spun off. The best sample for electrolyte testing is plasma. this is obtained by collecting whole blood into a tube with an anticoagulant, and then spin the sample as soon as possible to remove the blood cells. the high potassium probably resultd form the cells not being removed form either the palsma or serum quickly enough. what happens is that the potassium in the blood cells escapes into the serum or plasma sample and gives a false high reading. Any time a person sees an an unusual result on a test - any test- wheter the result seems to be too high or too low- if the reult does not fit with the clinical signs and history, one needs to look at that result carefully. Was the sample handled properly? Was the test doen properly with both a negative and positive as control? If the result is skewed retest the sample if you think there may have been a problem with the test procedure. If the sample itself is the problem then you need to resample the animal.