Which BGL is the right BGL?

[AKmedik8or]

Is there a difference in BGL levels?

A patient presented with an episode of near syncope after standing. Patients B/P 140/90, cardiac monitor sinus without ectopy, no orthostatic changes, 12 lead without ST changes. The patient was conscious and lucid throughout contact, warm and dry skin really in no apparent distress. The Pt did have an extensive heart history and as a new onset diabetic, who by his own admission is very non-compliant.

Our treatment was oral glucose and juice, the patient went on to explain episode of fever and diarrhea increased stress from work and so on. It was our advice for the patient to seek medical evaluation, he agreed, follow up evaluation of BGL at the start of IV after 10 minutes or so which showed an expected increase in BGL at 96. On arrival at the ED Pt BGL 108 without further change.

The statement from the ER doc was that there is a 10 to 20% difference between capillary blood and venous blood, further, that all pre-hospital accu-check type BGL testing devices are calibrated to test capillary blood only. I was caught off guard by his statement;

I have not been able to find any information that supports his claim as to a difference between the two in testing with a finger stick v/s IV catheter return.

Anyone have the answer?

[Ridryder 911]

There has been several reports stating what he has described. Attempt searching lab journals. we are not allowed to obtain BGL in ER from IV/VP. we do in the field, because we are primarily treating according to clinical signs, not an exact number.

R/r 911

[AZCEP]

A couple of things

First, the brand/type of blood glucose monitor that you use can alter the validity of the test result. How often is it calibrated, and by who? By calibrated, I don't mean the quality control checks. I mean the actually taking the device out of service, and going through it to make sure that it's programming has not lost accuracy.

Second, depending on the manufacturer of your monitor, what type of test strips are you using? Some devices are capable of testing capillary, mixed venous, or both. It should be indicated on the bottle of your test strips. For the Accu-check brand that we use, the capillary blood strips are in a red bottle, and the mixed venous are in a blue one. Check into this.

Also, regardless of the above, there is a pretty wide variability in how reliable each finger stick/blood sample will be. The conditions under which the sample is gathered can cause changes to the value. How clean was the site? Was there any contaminant on the strip? Was there a full moon? All fairly small alterations, but enough to alter the accuracy.

A finger stick glucose level is only a ball-park number anyway. Don't allow your treatment to suffer because of one number. If your patient looks hypoglycemic, they probably are. The worst thing you can do to a symptomatic patient is withhold some sugar because you got a normal reading on your monitor.

[rocket]

I've heard of this phenomenon from one of our local medics.

Here is a link that describes a possible reason for the differences. In essence, the authors state that capillary blood is closer in profile to arterial blood than venous (and there is evidently a difference in glucose levels between the two types):

http://www.medicine.uiowa.edu/cme/clia/modules.asp?testID=1

-Trevor

[PCPinMB]

Just a question regarding protocols with the point brought up saying 'if the patient looks and is acting hypoglycemic, don't withhold treatment because of what the device said' (or something along those lines). Our protocols for hypoglycemia (whether we're giving oral glucose, glucagon or D50) state that the patient must have a blood glucose lower than 4.0 (we use a different scale in Canada, i'm not too sure what it translates to for the American scale).

So what happens if your pt is looking and 'acting' hypoglycemic and you get that reading (multiple times)? Do you treat or do you follow protocol? Just wondering, I'm still a student so I'm not too sure how things would work then. Call medical direction after you have already explored the other reasons the pt could be altered (what I am assuming the pt would be)? Or just make the call on your own?

[ERDoc]

Not to get off the topic, but what about this patient made you think he was hypoglycemic?

[TTLWHKR]

What was his BGL before you loaded him with glucose and juice..?

As a diabetic myself, having chronic hypoglycemia since I had an unknown strain of the flu twenty years ago... This patients vitals & s/s do not clue me into any acute level of Hypoglycemia. What was it before 96, b/c that is certainly not a level that requires any emergency intervention. I'd be concerned around 55, and worried a little around 45, but I wouldn't panic unless I could no longer function w/ in reason.

[AKmedik8or]

colleagues;

I apologize for the absence of the pre-treatment BGL it was 42. Again the patient presented lucid warm and dry and in not in acute distress none the less hypoglycemic.

Also to address the concerns of monitor testing v/s calibration. A bench calibration is done with the high and low solution each monday of the week.

[kevkei]

The statement from the ER doc was that there is a 10 to 20% difference between capillary blood and venous blood, further, that all pre-hospital accu-check type BGL testing devices are calibrated to test capillary blood only. I was caught off guard by his statement;

I doubt that they are 'calibrated' to differentiate between venous VS. capillary blood. Blood is blood, all it is looking for is a glucose level. Just as pulse oximetry lacks sensitivity and specificity for what is bound to hemoglobin.

Now, stating there is a 10-20% variance between the two, which in his opinion is lower of them?

[Arachne]

I would guess that venous blood, such as one would draw when starting an IV, could have a lower BG than capillary blood because some of the glucose in the blood has been extracted by the cells surrounding the capillary beds.

Disclaimer: That's just a guess, I didn't research it.