Glucose meter

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Permalink Reply by ES on November 3, 2009 at 4:54am

Regarding Question 1 - I think that the JEMS Magazine had an article (or notice) about this a while back.

If the Glucometer that you use is calibrated for Capillary blood then you will likely get a higher reading from Venous blood.

See the following for a study:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B75DG-...

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Permalink Reply by Chance Gearheart on November 3, 2009 at 11:45am

Uri, according to our hospital protocols, unless the monitor is calibrated or ment for use with both venous glucose and capillary glucose, like the Accucheck-PDA Styled Ones, then you have to take a capillary BGL sample. The reason is that glucose readings from venous sticks can vary as much as 10 - 20 mg/dl depending on the time since the stick, presence of wet alcohol on the skin, etc. Also, if you give Dxx in one arm, check in the other arm or with an alternate site stick within five minutes. The reason is, the glucose in that arm will give a false reading.

Most ambulances use off the shelf capillary BGL monitors. They were never ment to take an arterial or venous BGL. On these, it's always best practice to get a capillary sample.

The best exception to this rule you can have is to have an iSTAT.

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Permalink Reply by James Ownbey on November 3, 2009 at 11:47am

I would go with the opposite arm. The BG in that arm will better represent BG in the going to the brain.

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Permalink Reply by blair4630 on November 3, 2009 at 9:54pm

In answer to questions one, unless you know for sure that your glucometer can take venous blood, don't use it that way. People often say "it saves the pt. a stick". the stick from a glucometer is minimal pain, and better than missing an important finding.

As far as questions 2, everyone here is saying check the opposite arm in 5 minutes after administration of D50. I have no idea why. You put the glucose into the venous circulaiton, which moves the glucose away from those tissues, in a closed circuit (vein), to the heart, then circulated back to the entire body evenly. There is no physiological reason a blood glucose from a capillary stick would be any different in either hand/finger. Unless of course you infiltrated that vein and kept pushing D50, in which case you have way, way, way, way bigger problems on your hand.

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Permalink Reply by TheCannulator on November 4, 2009 at 4:27am

There shouldn't be difference between a venous and capillary measurement in glucometers. When inserting IVs during my nursing ED shifts we often take the sample from a drop of blood onto the dressing pack sheet.

You don't need an iStat.

If you are giving D50W for the effect of hypoglycaemia, the effect is elimination of symptoms of hypoglycemia

If there is any issue of their ability to self care then you just trasnport and a venous sample can be done in th ED.

Post dextrose BSL's are inaccurate decision making tools shortly after administration. partilcularly when once conscious a complex carb meal is indicated anyway.

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Permalink Reply by Jonathan Gilliam on November 4, 2009 at 7:27am

I wanted to wait a bit before commenting, and I'm glad I did. The thing that I thought was going to pop up did, which is that the glucose would remain in the arm, so check the other arm. Blair nailed it when he said that you are putting it in to the venous circulation. The glucose would move up and out, and not down, so there'd be no more glucose in one arm than the other. Fortunately our veins have an automatic feature to keep blood from flowing backwards in the form of valves. Glucose readings will vary between sticks no matter if they're from the same puncture site, or from different ones. This may explain what you interpret as higher findings. One suggestion though, like Cannulator said, let them eat once they become conscious, then check it. I'd say that'd be about 15 minutes after the D50 administration. This allows the body to consume some of the glucose and start to come back down from the spike of D50. It's also a perfect opportunity for the patient to eat, or drink and to interview and assess the patient. Of course, if the patient doesn't improve, or if the usual LOC is decreased, transport and reassess the glucose enroute.

On the sample issue, I think it's rather unanimous that you should obtain a capillary sample. And I also have a saying. If you didn't learn a practice in paramedic school, but rather through the habits of other medics, don't do it. There will be a difference in the glucose level of venous blood because it has already had some of the glucose from it used by the cells as it passed through the capillary bed. The difference may be negligible, but I just don't leave it to chance. The main difference between arterial and venous blood is in the blood gases and the nutrients. An off the shelf version will read a venous sample just fine, but the value will most likely be lower. Get the capillary sample, and you'll be sure you have the most accurate result.

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Permalink Reply by Mike Rubin on November 4, 2009 at 9:40am

See the 4Q'04 and 3Q'01 issues of Prehospital Emergency Care for research on this subject. Bottom line: capillary blood glucose samples probably will differ from venous ones, sometimes significantly.

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Permalink Reply by Joshua Todd on November 7, 2009 at 3:23am

Unless I am mistaken it has nothing to do with the calibration. The blood glucose levels of venous blood differ from capillary blood for the same reason that an axillary temperature differs from a rectal one. Its not that the thermometer is calibrated differently its merely that the values are in fact different. Now I have never been educated on the appropriate blood glucose levels for either venous or arterial blood so I always do a fingerstick for blood from the capillaries as I know for sure what the appropriate levels are from that source. Perhaps you could find the appropriate ranges for a venous sample and continue to use that as a source for your BGL however I would encourage you to document this as you would a temperature reading with the site that the reading was taken to ensure that the hospital and other care givers reviewing your paperwork have an appropriate idea of the pt's condition.

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Permalink Reply by Chance Gearheart on November 7, 2009 at 3:36am

Joshua, the reason is that a purely venous blood sugar differes significantly, often by up to plus or minus 20mg/dl. In addition, unless you actualy perform the blood sugar from blood seeping out of the catheter hub, you're not getting an accurate picture of the actual nutrient reaching the capillary beds, giving you a good idea of the actual status of end-stage perfusionary areas. Even on a finger-stick, most protocols now say to be sure the stick site is dry, and to discard or wipe off the first drop of blood that appears to prevent the antiseptic from influencing the reading. That blood that sets in the needle flash hub is not the same as a fresh capillary or preserved venous sample being used, either.

Most monitors are not designed to test whole venous blood in the first place.


Joshua Todd said:

Unless I am mistaken it has nothing to do with the calibration. The blood glucose levels of venous blood differ from capillary blood for the same reason that an axillary temperature differs from a rectal one. Its not that the thermometer is calibrated differently its merely that the values are in fact different. Now I have never been educated on the appropriate blood glucose levels for either venous or arterial blood so I always do a fingerstick for blood from the capillaries as I know for sure what the appropriate levels are from that source. Perhaps you could find the appropriate ranges for a venous sample and continue to use that as a source for your BGL however I would encourage you to document this as you would a temperature reading with the site that the reading was taken to ensure that the hospital and other care givers reviewing your paperwork have an appropriate idea of the pt's condition.

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Permalink Reply by blair4630 on November 7, 2009 at 12:32pm

Chance Gearheart said:
Even on a finger-stick, most protocols now say to be sure the stick site is dry, and to discard or wipe off the first drop of blood that appears to prevent the antiseptic from influencing the reading.

Unless the finger is visibly dirty, I don't wipe it with alcohol for just that reason. I'm not too concerned about a lancet as a real threat for infection pathway.

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Permalink Reply by dr-exmedic on November 8, 2009 at 10:02am

blair4630 said:

Unless the finger is visibly dirty, I don't wipe it with alcohol for just that reason. I'm not too concerned about a lancet as a real threat for infection pathway.

It should tell you something when diabetics who stick themselves multiple times a day often don't use an alcohol pad either, at most they'll wash their hands with good ol' soap & water...yet if they have infection issues in an extremity, it usually isn't the upper ones.

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Permalink Reply by blair4630 on November 8, 2009 at 2:46pm

Yeah, I still use an alcohol swab, but for them to pinch between finger and thumb after I get my sample. To me the infection risk just doesn't present enough that I want to chance the reading.

It should tell you something when diabetics who stick themselves multiple times a dayoften don't use an alcohol pad either, at most they'll wash their hands with good ol' soap & water.

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