Phlebotomy Question

[18G]

I have a question regarding phlebotomy.

The standard phlebotomy practice is to NOT leave a tourniquet in place for longer then one minute prior to drawing blood. Once a vein is found if taking longer than one minute, the tourniquet is supposed to be removed, site cleansed, and then reapplied after waiting two minutes. The basis for this is hemoconcentration which can skew lab results.

My question surrounds tourniquet placement time when starting an IV and drawing blood off the IV catheter. Most of the time the tourniquet is left in place 2-4mins before the IV is started especially in a difficult stick. Granted, the tourniquet is released immediately after the IV start but you dont have time to wait two minutes before using a syringe or placing blood tubes.

So, how does this effect hemoconcentration and blood draws??? Is it an issue of concern? How does everyone do their blood draws?

 

[jwk]

I have a question regarding phlebotomy.

The standard phlebotomy practice is to NOT leave a tourniquet in place for longer then one minute prior to drawing blood. Once a vein is found if taking longer than one minute, the tourniquet is supposed to be removed, site cleansed, and then reapplied after waiting two minutes. The basis for this is hemoconcentration which can skew lab results.

My question surrounds tourniquet placement time when starting an IV and drawing blood off the IV catheter. Most of the time the tourniquet is left in place 2-4mins before the IV is started especially in a difficult stick. Granted, the tourniquet is released immediately after the IV start but you dont have time to wait two minutes before using a syringe or placing blood tubes.

So, how does this effect hemoconcentration and blood draws??? Is it an issue of concern? How does everyone do their blood draws?

It might be a theoretical concern, but it simply is not a practical concern. Hemoconcentration from tourniquets? Hmmm, I doubt it, and doubt any clinical significance - although I'm sure someone will find an article saying that it occurs.

 

[18G]

I appreciate your reply. I was thinking the same thing as you regarding mostly a theoretical concern but wanted to investigate it more since I am putting together an in-service for our Paramedics.

 

[mycrofft]

Get on the Google! Or call your local lab and ask.

Unless there is clotting or the serum is mysteriously going third-space, a TK shouldn't cause haemoconcentration or anything else. Unless its anoxic, but that takes time. It will increase bruising, and a site needs to be antiseptic for a stick, you can't just go poking around like a sewing machine if the first try misses, you need to reclean the site. Chaning site is just a good idea.

Now, as for fingerstick glucometry, "milking" a finger too hard will result in a skewed result, sometimes up, sometimes down. Holding a finger tightly at the base like a tourniquet for a second or two will usually make it congest and furnish a nice blood droplet, whereas SQUEEEEEZING will produce more serum versus cells.

 

[18G]

Google is my best friend and I haven't had time to call the lab at my employer yet.

All sources online regarding phlebotomy state the one minute rule due to hemoconcentration. I'm gonna search for any studies evaluating this today.

 

[9D4]

Typically, one of the most common tests for most labs is a CBC. This is (from my understanding) pretty much the only test upset by hemoconcentration (I.e. It won't affect your results when you draw a SST, nor a PST). Even then, lavender tubes are pretty far down the order of draw and if you need several tubes, a minute isn't going to cut it, so that whole minute thing is a bit like the golden hour, imo, a heavily emphasized guideline that you will occasionally go over. I always remove my TK halfway through the filling of the last tube.
I've never taken an IV class and only have started one, so im speaking on an one sided basis, but like I said, one minute is on the low side and occasionally you'll go over.
As far as finger sticks, like Mycrofft said, those results will be skewed by interstitial fluid if you aggressively milk it. I would say very rarely would a normal vacutainer draw be skewed by going over a minute. That being said I can see how the results would be skewed if you drew right under where you place the TK, but we draw 4-6 inches below the TK exactly for that reason.

 

[18G]

How do most providers draw their labs in the field?

Do you use a 10-20mL syringe connected directly to the IV catheter hub?

Do you attach a vacutainer to a dry saline lock?

Do you attach the vacutainer with luer lock directly to the IV catheter hub and then insert your blood tubes?

 

[Christopher]

Will it affect the routine stuff? No. But it does affect "hemorheological measurements" and the possibility of hemolysis.

Cengiz M, et al. Influence of tourniquet application on venous blood sampling for serum chemistry, hematological parameters, leukocyte activation and erythrocyte mechanical properties. Clin Chem Lab Med. 2009;47(6):769-76. (PubMed)

CONCLUSIONS: Our blood sampling technique which mimicked the application and release of a tourniquet indicated unaltered values for routine blood gases, hematological testing and serum electrolyte levels. Conversely, hemorheological measurements can be affected. Therefore, it is strongly recommended that tourniquet application should be avoided during blood sampling or, if this is not possible, the procedure should be well standardized and details of the sampling method should be reported.

Saleem S, et al. A prospective study of causes of haemolysis during venepuncture: tourniquet time should be kept to a minimum. Ann Clin Biochem. 2009 May;46(Pt 3):244-6. (PubMed)

CONCLUSIONS: Tourniquet time of more than a minute is associated with a significant increase in risk of haemolysis. Advice on tourniquet time is included in phlebotomy training within the hospital; hence a campaign of appropriately channelled continuing education on this issue may be successful in reducing the haemolysis rate.

Connes P, et al. Sampling time after tourniquet removal affects erythrocyte deformability and aggregation measurements. Clin Hemorheol Microcirc. 2009;41(1):9-15. (PubMed)

In conclusion, this study revealed that RBC deformability and aggregation might be significantly altered in the samples obtained after the application and removal of a tourniquet, as a part of the blood sampling procedure. Recommendation "remove the tourniquet at least 5 s prior to the start of blood sampling" may need to be revised.

Berns SD, Matchett JL. Effect of phlebotomy technique on serum bicarbonate values. Acad Emerg Med. 1998 Jan;5(1):40-4. (PubMed)

CONCLUSIONS: Small needle size does not affect serum bicarbonate values. Prolonged tourniquet time results in a statistically significant elevation of serum bicarbonate, although this elevation may not be clinically meaningful. Underfilling of Vacutainer tubes significantly influences the accuracy of serum bicarbonate values.

 

[18G]

Thanks, Christopher!

 

[18G]

I wonder if drawing a discard tube would be beneficial when drawing labs with an IV start in the field?

 

[mycrofft]

Discard tube? Any blood my be useful, even if only for a toxscreen. Label and submit everything.

Thanks Christopher! The passages seem confusing, will need to read the study. The last bit about "significant" but "not clinically useful" was funny...e.g., don't worry about it in patient care (regarding that one value at least).

I guess the rise in intravenous pressure due to the TK could rupture some cells, leading to low crit/elevated K+/possible glucose changes, and hanging around without going past the lungs starts changing pH etc.

 

[Christopher]

Discard tube? Any blood my be useful, even if only for a toxscreen. Label and submit everything.

Thanks Christopher! The passages seem confusing, will need to read the study. The last bit about "significant" but "not clinically useful" was funny...e.g., don't worry about it in patient care (regarding that one value at least).

I guess the rise in intravenous pressure due to the TK could rupture some cells, leading to low crit/elevated K+/possible glucose changes, and hanging around without going past the lungs starts changing pH etc.

Statistical significance and clinical significance are two different beasts.

Given two tests which produce two results, studies on a sample population using both tests may give a statistically different result. But let's say their sample means differ by 2 Fictional Units. If your clinical decision making is based on a scale of 100s of Fictional Units, the fact that your two tests produce statistically different results is not clinically significant to your patients.

 

[mycrofft]

Right on!

 

[18G]

Some policies require a discard tube especially if drawing as a last resort in an arm with a running IV, from a flushed saline lock, etc. I've also seen some requiring a discard tube for coagulation studies.

I've been reading a lot of conflicting information. Some say its perfectly ok to draw off an IV catheter, some swear its not ok. One ED study found EMS blood draws to be less hemolyzed then the ED draws. The ED re-draw rate was actually higher surprisingly.

Lacking clarity

 

[mycrofft]

Some policies require a discard tube especially if drawing as a last resort in an arm with a running IV, from a flushed saline lock, etc. I've also seen some requiring a discard tube for coagulation studies.

I've been reading a lot of conflicting information. Some say its perfectly ok to draw off an IV catheter, some swear its not ok. One ED study found EMS blood draws to be less hemolyzed then the ED draws. The ED re-draw rate was actually higher surprisingly.

Lacking clarity

That's because....the paramedics used up all the good veins?:unsure:

 

[18G]

That's because....the paramedics used up all the good veins?:unsure:

No, it has nothing to do with vein availability. A discard tube is meant to evacuate any blood potentially contaminated with IV fluid or medication and also to discard bad specimen blood that may have been involved with venous stasis.

That's my understanding.

 

[Engineered]

How do most providers draw their labs in the field?

Do you use a 10-20mL syringe connected directly to the IV catheter hub?

Do you attach a vacutainer to a dry saline lock?

Do you attach the vacutainer with luer lock directly to the IV catheter hub and then insert your blood tubes?

With the exception of blood draws for PD, we go straight off the cath before hooking up the drip set or extension. For PD blood draws we do either butterflies or straight needles on the vacutainer.

 

[18G]

With the exception of blood draws for PD, we go straight off the cath before hooking up the drip set or extension. For PD blood draws we do either butterflies or straight needles on the vacutainer.

Syringe or vacutainer when going off IV?

 

[Tigger]

How do most providers draw their labs in the field?

Do you use a 10-20mL syringe connected directly to the IV catheter hub?

Do you attach a vacutainer to a dry saline lock?

Do you attach the vacutainer with luer lock directly to the IV catheter hub and then insert your blood tubes?

The third option is pretty standard around here. Not sure what we do with PD blood draws, haven't been trained on that yet.

 

[Engineered]

Syringe or vacutainer when going off IV?

Straight to vacutainer. Its SOP for a full rainbow set on each stick (one per pt)