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To Clamp or Not to Clamp

This is a question we have had concerning all access that comes with a clamp - peripheral IV, Power PICCs, Central Lines.   We do use MaxPlus Positive Displacement Connectors on all central lines.

The worry isn't about backflow - we know the caps prevent that.   We've also been told that using the clamp actually deactivates the cap.   Not sure if that's true.   However, the worry is that IF a cap is left off accidentally, the clamp will prevent backflow.

Looking for some advice on this.   Thanks, Kelly

Gwen Irwin
My opinion is that clamping

My opinion is that clamping is a safety issue to prevent air embolization and possible exsanguination (depending on the patient's position if the cap is removed).   We teach that if you clamp to do it after flushing.   I emphasize that clamping is a patient safety issue and not related to creating positive pressure like we did for years.   The technology takes care of all of those old steps to create positive pressure.

If you clamp before removing the tubing/syringe, then the action of the cap could be deactivated.   That is what needs to stressed.   Clamp after removing tubing/syringe.

 Hope this helps.

Gwen Irwin

Austin, Texas

Also... if you are using the
Also... if you are using the CLC2000 connectors, you can detect if it has been clamped prior to removal of the syringe (and thereby without activating the positive displacement mechanism) as the white core will be depressed.   Unclamping will pop it out and the positive displacement will then occur. Might be a good time to flush again.
Kathy Hartman

I have to agree with Gwen. Clamping is completely a safety issue. One of the major complications of infusion therapy is air embolism.

Human error can cause caps not be be secured as tight as they should be, which will place the patient at risk for a life threatening condition.

Clamps should not be eliminated from any centrally placed line.

Kathleen Hartman, RN BSN

KPater, There was/is concern


There was/is concern with clamping the line with some positive pressure caps. Infact some manufactures use the language of "deactivation" or "breakage" of the internal mechanism of the cap may take place if the line is clamped. There are newer design poitive pressure caps on the market that will not be deactivated by clamping the line. One of these caps has been brought to my attention by Nancy Burton, Baxter IV Therapy Representative. The Baxter FLOLINK Positive pressure displacement device is luer lock device that can be clamped without fear of  breaking or deactivating the device per Nancy at Baxter. We are actively looking to rplace our current device with device as it has no increase in cost for us (per Nancy).

Not clamping is certainly a patient safety concern.

Julie May, RN, BSN, CRNI

Scott Gilbert
to clamp or not to clamp

here are a few comments from   quite a while ago that I have saved on "Clamping" ---


Clamping the CLC 2000

If you clamp the catheter or extension set PRIOR to disconnecting your flush syringe from the CLC2000 it has the same effect as stepping on a garden hose. It does not allow the positive displacement fluid to exit the catheter.

If you clamp AFTER disconnecting your flush syringe from the CLC2000 you have allowed the positive displacement fluid to exit the catheter and everything should be fine.



Alison Brummett

Marketing Operations Manager

ICU Medical, Inc.

[email protected]

949-366-2183 ext.4314


Clamping the PASV Valves by Boston Scientific:



In PASV catheters or catheters with a PASV Protector added, clamping

interferes with the valve function. This valve works by pressure. If

you clamp any portion of the catheter between the patient and the

valve, it acts in the same manner as when you pinch a fluid-filled

straw. Fluid drips on the end and when you release the compression,

the fluid level rises leaving a small air space. In the vein, this

small space is filled with blood reflux thus defeating the presence

of the valve.

>The PASV manufacturer has always stated no clamps. You may not always

>be assured that the clamp was not opened and closed in between the

>flushing procedure. Clamps are not necessary because of the valve

>inside the catheter hub. To my knowledge there have been no reports

>of valve failure ending in air emboli or exsanguination. So I would

>follow manufacturer's recommendations.

>Positive pressure is a phrase applied by many to the new devices, but

>they really do not exert an increase in pressure inside the lumen.

>They send a small squirt of fluid to the catheter tip when the tubing

>or syringe is disconnected. This causes the positive fluid

>displacement but it really is not positive pressure

Lynn Hadaway, M.Ed., RNC, CRNI

Lynn Hadaway Associates, Inc.

770-358-7861 office

770-358-6793 fax


Clamping the POSIFLOW by B-D


Subject: C.lamp or No-Clamp

To: [email protected]

From: [email protected]

Date: Fri, 15 Nov 2002 10:05:00 -0700Scott,

I am in agreement with your opinion that "...clamping AFTER syringe removal

is a safe-practice". Rest assured that clamping after syringe removal does

not have any negative affect on the function of the BD Posiflow device.

If you have any further questions feel free to contact me directly.

Bryan Davis

BD Posiflow Product Manager

BD Medical Systems



Clamping the Alaris SmartSite Valve


Date: Fri, 15 Nov 2002 20:23:23 -0800 (PST)

From: Ted Mosler <[email protected]>

Subject: RE: Clamp or No-Clamp

To: [email protected]

Sender: [email protected]

Alice is absolutely right. Alaris Medical Systems

directions for use instruct the clinician to clamp

AFTER disconnection from the SmartSite Plus

Needle-free Valve with Positive Displacement. I would

suspect that all manufacturers of positive

displacement valves would support this.

Ted Mosler

Alaris Medical Systems

Sr. Design Engineer


To: 'Scott Gilbert' <[email protected]>

Subject: RE: C.lamp or No-Clamp

Date: Fri, 15 Nov 2002 09:46:23 -0600

Hello Scott- God I wish I was in Hawaii,

My understanding of the positive displacement caps like Posiflow, CLC 2000, etc. is once the valve activates upon removal of the syringe- there is a flush of fluid to the tip of the catheter which prevents blood reflux, period. Therefore, there is no harm in clamping the catheter after removal of the syringe once you have allowed the valve to activate.

(notice I used the words "displacement" not positive pressure- learned this from Lynn Hadaway's posts :-)

The confusion comes in (I believe) in that we normally teach nurses to do a positive pressure flush and clamp the catheter as the plunger on the syringe is pushed. Since the new caps do this little extra flush for us, the correct use of the new caps involves a change in practice. I discussed the clamp or not to clamp issue awhile back with our Abbott clinical rep (who market ICU Medical's CLC 2000), and she said it did not matter if you clamped after you have allowed the cap to work.

A couple of years ago, I worked for a home infusion company that used Posiflow caps on their midlines. In the beginning of trialing the cap, we taught the patients not to clamp. I believe this is because we were under the impression that the caps maintain a pressure wtihin the catheter that prevents backflow. There were some problems with catheters clotting and blood reflux that probably would not have occured if we knew it was ok to clamp the catheters. Since then I have had discussions with BD reps they have also stated that it is ok to clamp the catheters after you allow the Posiflow to activate after removal of the syringe.

I believe the confusion comes in as to when to clamp, and to get nurses to change their practice a little.

My two cents, hope it helps. Alice Cennamo, RN, CRNI IV & Phlebotomy Coordinator Organization Development and Education Dept. Bridgeport Hospital




Here at our facility we used the Posi flow cap. We found we had frequent

valve sticking with bleeding back whether we clamped or not. We had such a problem with it we

kept all caps and returned them to the company. (This happened over a period

of 6 months or more) When we would complain the company told us

no one else was having the problem. So we collected the caps and finally

our hospital agreed to break our contract with BD and we switched to CLC2000. We have had really good success with the CLC 2000. We occasionally

get a stuck valve (maybe one a month) but not the bleeding back.

We also teach to flush and not clamp but if they are more comfortable

clamping then to do it after they have removed

The syringe or they will negate the positive displacement action.

The reason I did not put this on the listserver is the company's monitor the

list server. When I posted this info before

BD was most unhappy with me.

Margy Galloway, RN

Kansas City


Subject: PosiFlow IV Access System

As a medical device design engineer, I concur with much of the selection

criteria recently posted in this e-mail community regarding valved injection

site technologies.

Should any of you have questions relating to the performance

characteristics of the PosiFlow IV Access System, please e-mail me at the

following address. Should you have questions relating to the clinical or

economic features of this system, e-mail me as well and I'd be more than

happy to route your questions to appropriate individuals who can provide you

with an e-mail response.

I'm very excited about the value this device can add to your clinical

environment and want to ensure that you receive answers to questions you may

have directly from Becton Dickinson.

The PosiFlow IV Access System flows at a rate of 4 liters per hour. From

your response below it seems to be more than enough to meet your needs.

This helps validate what we have tested with our customers.

The PosiFlow valve was designed to optimize clinical flow rate needs,

positive fluid displacement performance, and cost.

Michael Kirklen

Becton Dickinson

Todd Schwendiman

Senior Engineer

Becton Dickinson

[email protected]


I think the most important part of both the clc and ultrasite is to use them correctly by not clamping the line until after the syringe is removed.

Holli Wiseman RN,MS, CRNI VNA Denver Colorado


When using a positive pressure needle-free valve, you can clamp - but only

after you remove the syringe from the valve, post flushing. If you attempt

to clamp while the syringe is still attached, you will likely get some

leaking or squirting of fluid as the fluid path of the flush solution will be

obstructed by the closed clamp.

Judy Stanek, RN, BA, CRNI



Subject: groshong and positive pressure caps.

Author: [email protected] (Galloway; Margy)

Date: 8/7/01 12:21 PM


Sheila, Paul, and all,

I find the "clotting" off of groshongs an interesting topic. So I went back

to look at my PICC data from 1989 and on. I look at what was documented

about the clotting off of the lines. Here RNs place groshong and when

radiology started backing us up in 1996 they placed Cook PICCs.

Here is what I found. Prior to our use of the Clave, we used the screw on

caps and pushed a needle through the top of the cap when we wanted access.

These caps are still available but with the push to go needless we switched

to the Clave at the end of 1997 or the beginning of 1998. Then in 1999 we

went to the CLC 2000 on catheters who we felt had a higher possibility of

clotting off and Claves on all others.

So our problems with catheter clotting and our use of urokinase during prior

to 1996 was about 18% of in house catheters. Then when radiology joined us

in 1996 we saw groshong at about 18% and cooks at 19%. No significant

difference. This pattern continued until 1999. Now realize - we have NO IV Team here.

We also did not do any education for prevention of line clotting.

In March 1999 we started our PICC program and with the increase of line

placement we were able to do more one on one education regarding flushing.

The CLC 2000 was discovered and we started using them. In 1999 or rate fell

to 12% groshong and 14% cooks. For 2000 it fell to 7% groshong and 9% for


Now in 2001 we have switched to B-D Posiflow caps on all IVs and thePICC data for clotting is on the rise. I am seeing 9% for groshong and 10%

for cooks. Why the difference? Probably a learning curve.

I looked at this as I do not feel that the Clave placed on any PICC "causes"

the blood to back up into the end of the catheter causing it to clot off.

There are too many factors to say what the cause is.

I think patients make a difference. Patients who are on ventilators have

higher chest pressures causing blood back up the end of catheters, patients

with lots of vomiting causes blood back up, etc.

I believe fibrin can and does build up on any catheter opening and

contributes to the clotting off. When looking at your clotting rate or incidence can you say it is going up and along with it, is the number you are placing alsogoing up?

What does all that mean? The reason I used percent of incident is because of the growth of our PICC program.

I feel education of the person using the PICC also plays a big role. It is

not unusual for me to find the reason a line is clotted is because a RN went

in to draw blood but did not bring a flush with her and by the time she

returned, it had clotted off.There are many more reasons I'm sure we could all discuss for line clotting.

Just more than my 2 cents worth.

Margy Galloway, RN

Kansas City, MO

Scott Gilbert RN, VA-BC, MPH


Clamping all depends on the
Clamping all depends on the type of cap in use and unfortunatly many hospitals still use several different types of injection caps.
The pre-pierced synthetic rubber diaphragm caps and the early valve type caps such as Clave cause negative pressure as the flush syringe is disconnected. This results in blood reflux unless the clamp is closed PRIOR to disconnection.
If a postive pressure caps such as the CLC2000 is used, the IV can only be clamped AFTER disconnecting the syringe - or the injection cap will malfunction. Also, if someone attaches a "dead end" cap to a positive pressure cap when the IV is not in use, connection TO the positive pressure caps results in blood reflux into the catheter. (Some nurses do this to "keep the cap clean", not understanding that blood reflux will result.)
The InVision Plus is currently the only truly neutral cap - does not cause blood reflux either on connection to or disconnection from the cap and is   not impacted by clamping.  
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