Blood Glucose Measurement: Arterial vs Fingertip

[Catticus11]

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I was wondering, is there a significant difference between blood sugar measurements at the finger tip vs sampling from an arterial (or even venous) blood source? If so, which is more reliable and which one should is preferred to base an intervention on? (ex. insulin drip)

[firemedic12, BSN, RN, EMT-P]

In my experience, the hierarchy for most hospitals is arterial > central line > finger stick. They say that an arterial draw is the most accurate. Pts on an insulin gtt get q1 sugars and I personally would rather not have my finger stuck every hour. I only stick if the patient doesn't have an A-line or central line.

[Catticus11]

Thank you! :)

[russianbear]

Thank you! :)

Sup Sam, how you doing?

[PresG33]

CBG = CAPILLARY blood glucose, so the machines are calibrated to capillary blood. That is the "JAHCO" answer. That being said, the studies that look at this found a variability within about 10 mg/dL which is close enough for clinical use.

Caveats: if a patient is on high dose/multiple pressors or in sever shock, finger sticks are inaccurate because of poor perfusion and arterial/venous blood should be used. Also, the machines are calibrated to a "normal" hemoglobin and there can be some variation with low Hgb.

If a pt has an Aline I use it for all my sugars an did I get an abnormal value I would confirm at a different site before treating.

[EllaBella1, BSN]

Our glucometers ask us to select which sample type we will be applying prior to touching it to the blood source. Chances are if yours doesn't ask it's probably calibrated to capillary blood, and that would be most accurate. Unless of course the patient is on pressors or has poor perfusion for some reason.

[Veldtor, BSN, MSN]

Arterial is consider most accurate, most glucometers, as previously mentions are calibrated to capillary blood. I find capillary readings vary on how warm or cold the fingers are and how well they are perfused. At our hospital, if someone is hypoglycemic, we are required to immediately do another FS for accuracy.

[marienm, RN, CCRN]

My hospital says we can use a line draw (either arterial or venous) or a fingertip, but not an earlobe or toe. I can't remember what brand of glucometer we have, but that's what our policy says. When the provider orders glucose checks, they have to click a couple of boxes "Does the pt have impaired perfusion to hands?" "Does the pt require vasopressor support?" and if "Yes", the order is supposed to be written for percutaneous blood (venous either by a line or by a blood draw, or arterial) and not a capillary sample at all.

If my pt has an A-line WITH a cell-saver device, I will definitely use this for my Q1 hour checks with an insulin gtt (which sometimes are Q15 minute checks if they get too low and have to get dextrose). However, if the line doesn't have a cell-saver (our regular transducer tubing doesn't have them) I try not to use the arterial samples unless I have to do a blood draw at that time anyway (or unless their fingertips are unusable...I take care of burn patients so this does happen!). I feel like it wastes too much blood to clear the saline from the line--probably 3-5mL for each hourly check adds up! What do you all think? Would it be better to use a sterile, empty 10mL syringe to withdraw the waste blood, do the check, and then return the blood to the pt? That's effectively what the cell-saver does, but the blood never leaves the closed system of the tubing so I feel like that's safer than taking the blood out with a syringe. There isn't any anti-coagulant added to the blood in either case (our flushes do not have heparin added), so the risk of a clot forming in the "static" blood is the same.