How to Use Point of Care Tests in the Vet ER

In this video, we will demonstrate how to use STAT Point of Care Tests in the Vet ER:

Coming soon!

STAT "Point of Care Tests: It is nice to run a couple quick, easy "point of care tests." These are some of the most useful parameters to note during an emergency, because they help you to gauge how severe the situation is. It only takes a few seconds to prepare these samples, and there is often enough blood in the IV catheter stylet to get these tests started.

You can actually collect your baseline blood samples via the IV catheter during IV catheter placement to save you time (click here to learn how). Combining the two procedures is much more efficient and helps to preserve the patient's veins. Minimally, I always like to run a baseline PCV/TP, lactate (“how sick are you?”) and blood glucose on emergency patients.

PCV/TP

PCV is code for packed cell volume or hematocrit. It is the percentage of red blood cells in the blood (red blood cell count). A PCV of 20% is considered a "transfusion trigger," so if you see a PCV approaching 20% or in that vicinity, you may need to start making arrangement for the patient to receive a blood transfusion. It is good to know this as soon possible in case you need to call in a blood donor, get blood from another hospital, or possibly arrange for the patient to be transferred to a hospital that has blood products on hand.

TP is the total protein (or total solids). In cases of acute hemorrhage, this may drop before the actual PCV, so it is very useful to have this baseline number in any trauma patient or patient presenting with clinical signs of anemia.

Blood glucose:

Measuring the blood glucose requires just one drop of blood on a handheld glucometer (I prefer the Alphatrak glucometer) and reads in less than 5 seconds.

If profound hypoglycemia is present, administering intravenous dextrose can be life-saving (50% Dextrose: 0.25-1 ml/kg slowly IV; *make sure to dilute 1:4 with sterile saline prior to administering so that the high osmolarity of the concentrated dextrose does not damage the vein*).

Determine the cause of the hypoglycemia (the most common scenarios I see in the ER include: insulin overdose in diabetics, sepsis (BIG PROBLEM! if your patient is septic the clock is ticking), and Addison's disease, while nutritional (pediatrics/neonates), hepatic disease, and insulinoma

Lactate (lactic acid levels)

One of the first parameters I look at is the lactate level. This tells me- how sick is my patient? How badly is oxygen delivery to the tissues impaired? In my experience, the degree of hyperlactatemia corresponds the degree of compromise. Any elevation in lactate indicates that swift intervention is needed.

A lactate above 5 mmol/L means the clock is ticking. A lactate level in the vicinity of 10 mmol/L is a major emergency, and immediate and appropriate intervention is required if the patient is to survive the next hour. These patients should not be put away in a kennel; they should remain in the emergency treatment area as the focus of attention until they have been stabilized.

Stable means: normal heart rate, normal blood pressure, normal oxygenation, normal lactate levels.

Handheld lactate meters are priceless bedside tools. They only require a drop of blood and it is usually less than 60 seconds to results. In emergency situations, I like to recheck the lactate every 30 minutes until it is normal.

Monitoring the lactate helps you assess your progress. If the lactate level is not improving continually with treatment, you should ask yourself what part of oxygen delivery you might be missing (low blood pressure, impaired oxygenation/ventilation, anemia or blood loss?)

This should prompt you to initiate stabilization measures (IV antibiotics, blood pressure support, etc.) while you await cytologic confirmation (identifying intracellular/extracellular bacteria on microscopic review of the abdominal effusion).

One thing I should mention, is that there are two different stereoisomers of lactate (lactic acid) in the body: D-lactate and L-lactate. D lactate is the clinically relevant form of lactate in emergency situations. D-lactate is produced in situations where the tissues are being deprived of oxygen. When the tissues are not receiving enough oxygen for aerobic metabolism and the cells must switch to anaerobic metabolism, d-lactate is generated as a product of anaerobic metabolism.

Take home points on lactate:

1. An elevated lactate level indicates tissue hypoxia. This usually results from hypoperfusion, and will trigger the need for IV fluids. Supplemental oxygen should be administered to these patients.

2. The degree of elevation of lactate reflects the sense of urgency.

3. You must identify the reason for the hypoxia (hypovolemia, hypotension, etc.) and address it as quickly as possible to optimize the chances of survival.

Other uses for glucose/lactate measurement: Septic peritonitis: There is a quick, inexpensive and highly sensitive technique for quickly identifying septic peritonitis. You can compare the lactate and glucose levels of abdominal effusion vs. peripheral blood to identify septic peritonitis. In septic peritonitis:

-The lactate of the abdominal fluid will be greater than 2 mmol/L HIGHER than the lactate of the peripheral blood. The sensitivity and specificity of this finding for diagnosing septic peritonitis has been reported at 100%.

You can also compare the glucose levels.

-The glucose of the abdominal fluid will be more than 1.11 (20 mg/dl mmol/L) lower than the blood glucose of the peripheral blood. Using a cut-off of 38 mg/dl (2.1 mmol/L) improves the specificity of this test.

Aortic Thromboembolism (ATE/ saddle thrombus): You can compare the lactate and glucose levels of the affected limbs vs. unaffected limb to confirm arterial thrombosis.

-The lactate of the affected limbs (usually hind limbs in cats) will be significantly HIGHER than the lactate of the unaffected limbs.

You can also compare the glucose levels.

-The glucose of the affected limbs will be significantly LOWER than the blood glucose of the unaffected limbs.

 

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