Megan Brashear, CVT VTS(ECC), explains the importance of looking at the packed cell volume and total solids results together, and how using both results helps get a better picture of your patient's status and their future needs in the hospital.
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Performing a packed cell volume (PCV) and total solids is one of the easiest tests performed in a veterinary hospital. Almost all team members can perform a PCV/TS (total solids), but how many of them are comfortable interpreting those results? A PCV/TS can give you valuable information about the patient’s status and help you think ahead to the next step in treatment.
PCV is the percentage of red blood cells in circulating blood. A decreased PCV generally means red blood cell loss from any variety of reasons like cell destruction, blood loss, and failure of bone marrow production. An increased PCV generally means dehydration or an abnormal increase in red blood cell production. TS is a measurement of plasma proteins. These proteins include albumin, globulins, and fibrinogens. A decreased TS generally means the animal is suffering from protein loss from any variety of reasons like blood loss, PLE, PLN, or malnutrition. An increased TS usually means dehydration but can be present in certain chronic diseases.
By looking at a hematocrit tube fresh out of the centrifuge, you can also get some idea for white blood cell content by examining the buffy coat. The buffy coat sits between the red cell layer and the plasma (and should not be counted as part of the PCV) and is normally 1 percent or less. A large buffy coat can signify a large increase in WBC count. The plasma layer should also be examined for hemolysis, lipemia, and icterus. These characteristics should be noted along with the PCV/TS results. Remember to look at both values together to get the entire clinical picture of your patient, and continue to monitor throughout their hospital stay.
↑PCV, ↑TS: This patient is most likely suffering from dehydration. As the water portion of blood is decreased you will see an elevation in both the PCV and TS. Both of these values should decrease as fluid therapy rehydrates the patient.
↑PCV, normal TS: This patient also may be dehydrated, but remember that the addition of fluids will bring both values down, so there is a loss of proteins occurring. Watch this patient for the development of hypoproteinemia and associated clinical signs (hypotension, peripheral edema) as fluids are administered. This patient could be suffering from polycythemia, a rare condition where the body overproduces red blood cells.
↑PCV, ↓TS : This patient could be suffering from dehydration and a profound protein loss. More commonly, you may see this with a recent trauma. This patient may be suffering from acute blood loss and splenic contraction has temporarily increased the PCV, but the low TS points you towards blood loss. In a trauma patient where you expect blood loss it is important to recheck the PCV and TS after starting treatment.
Normal PCV, ↑TS: This is a common scenario with CKD cats. This patient is most likely suffering from anemia and dehydration. The normal PCV may fool you into thinking this animal is okay, but as you rehydrate remember that both numbers will drop leaving you with an anemia to treat.
Normal PCV, normal TS: Normal is good, right? Be sure to match the results to the patient. If this patient sustained recent trauma there may be blood loss that isn’t apparent on blood work yet. If the results are different than what you expected, then recheck the PCV/TS as you begin treatment.
Normal PCV, ↓TS: This patient is most likely suffering from a protein losing disease (PLN, PLE), chronic diarrhea, or certain liver and kidney diseases. Be prepared for clinical signs of hypoproteinemia (hypotension, peripheral edema) and their treatment.
↓PCV, ↑TS: The elevated TS most often points to dehydration, and remembering that the addition of fluids will further drop the PCV, this patient is anemic and needs close monitoring of the PCV and most likely the addition of blood products.
↓PCV, normal TS: This patient is suffering from RBC destruction lack of production. In blood loss we expect to see a decrease in the TS as well. With just the red cells decreased be on the lookout for IMHA.
↓PCV, ↓TS: This patient is suffering from whole blood loss and needs to be monitored very closely. Blood products should be considered in treating this patient.
Armed with this information, you now know a great deal about your patient just by looking at the PCV/TS. By using critical thinking skills and knowledge of the treatment plan for these patients you can prepare for their future needs.
|Packed Cell Volume %||Total Solids g/dl||Rule Out|
|↑||normal||dehydration, protein loss|
|↑||↓||acute blood loss|
|↓||normal||RBC destructive disease|
|↓||↓||whole blood loss|