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greg c
06-01-2004, 12:40
Called in last night to assist with a difficult intubation in which medicine and surgery teams were unable to secure an airway. There was a reluctance to trach given a current medication list including heparin and a IIb/IIIa inhibitor. A retrograde intubation kit was our saving grace and otherwise it is not an eventful story. A learning point did come out of it for the housestaff however, and it might be a learning point to some of you guys as well...

Prior to my arrival, a resident placed the endotracheal tube and pronounced it in place given condensation in the tube as well as a positive CO2 detection device color change. However, the patient's abdomen soon became distended, and sats continued to fall.

So.....

What can cause a false postive color change?
What can cause a false negative?

Sacamuelas
06-01-2004, 14:04
Disclaimer :I am out on a limb here... so take this for what it is worth (nothing). I had to do some refreshment reading since I am definitely not current on details and nuances of specialized ET confirmation procedures. Here goes....


False negative:
Measurement can sometimes be difficult in the cardiac arrest patient because poor systemic perfusion delivers little CO2 to the lungs for exchange. Therefore, false negatives only occur during a low perfusion state, particularly in cardiac arrest patients or those with severe pulmonary edema.

False positive:
Could result in those with a large amount of air in the esophagus. My guess for what occured in your example last night.


Another thing I came across is the possibility that the tube once confirmed by CO2 detection device in the field, could be inadvertently moved, and the CO2 detection devices do not provide a continuous detection of correct placement.


Will sit tight and wait for you trauma guru's to post.... :munchin

Doc T
06-01-2004, 23:04
Originally posted by greg c


So.....

What can cause a false postive color change?
What can cause a false negative?

as said before, false positive from esophageal air...usually seen after prolonged bagging and forcing of CO2 rich air being exhaled from the trachea back into the esophagus.... why you follow 4-5 breaths of the change to say you have a good airway.

false negatives... also as said before, full arrest with poor perfusion...lots of studies using this method to assess CPR, severe bronchospasm with poor exhalation can cause a poor return of CO2, other than these haven't seen a false negative.

glad things turned out well for the patient.... had he/she been stented? Haven't seen too much use for the inhibitors in my practice....

doc t.

greg c
06-02-2004, 05:04
You guys/gals are too good. The other classic false positive scenario is the guy who has had a soda/beer whatever, with the CO2 bubbles giving a vigorous colour change.

Re: stent- pt was being temporized until an AM cath in a hospital without an aggressive cardiologist. I'll let you generate your own opinion on that. I'm sure you know mine.

DoctorDoom
06-03-2004, 06:25
x

greg c
06-03-2004, 12:36
NSTEMI- that's why he was going for an AM cath.

DoctorDoom
06-03-2004, 17:21
x

ccrn
06-12-2004, 10:55
QUOTE]Originally posted by greg c
NSTEMI- that's why he was going for an AM cath. [/QUOTE]

Its been a couple of years since I worked in ED so my memory is a little vague, but if I remember right we dont do Q wave or non-Q wave diagnosis anymore but ST elevation or non-ST elevation dx for intervention or thrombolitics (which arent in favor as much any more) for ACS.

A pt should be in cath lab within 90 minutes of hitting the door or 12 hours onset of symptoms.

Im not clear what IIb/IIIa therapy has to do with hx of previous stenting unless it has somehow failed and are trying to prevent further damage? In any case this pt would go right to cath lab too unless being transported from rural environment.

Ive seen a lot of integrillin used but mostly for cath pts and sometimes AMI.

In any rate someone will probably get their butt sued for letting their pt sit for AM cath...

I always rely on chest rise and auscultation to comfirm ETT (or other) placement. CO2 det are very nice but not gold standard. CXR is even better but of course not available prehospital-

ccrn

Doc T
06-12-2004, 13:30
Originally posted by ccrn
QUOTE]Originally posted by greg c
NSTEMI- that's why he was going for an AM cath.

I always rely on chest rise and auscultation to comfirm ETT (or other) placement. CO2 det are very nice but not gold standard. CXR is even better but of course not available prehospital-

ccrn [/QUOTE]

The gold standard in 2004 IS CO2 detectors or capnography. End tidal CO2 detection comes close to 100% sensitivity and specificity in the patient with spontaneous circulation. Obviously all bets are off in a patient in circulatory arrest as very little CO2 is around to be detected. This is the method recommended by both the American Society of Anesthesiologists and National Association of EMS Physicians.

Esophageal detection devices are easily used but have a higher false negative and false positive rate to make the questionable for use in my opinion.

As for classic physical exam findings... in studies with dogs about 85% of dogs with esophageal intubations had fogging of the tube (don't think they'd let you purposefully do this in humans) and in other randomized prospective studies done in the OR (ie. controlled environment) there was a 15% -25% ERROR rate on auscultating bilaterally in asleep patients where anesthesiologists "heard" bilateral breath sounds in patients with esophageal intubations... all picked up by capnography.

Again...the gold standard is CO2 detection NOT auscultation or fogging.

doc t.

ccrn
06-13-2004, 01:37
Again...the gold standard is CO2 detection NOT auscultation or fogging.

doc t.


Ive never considered fogging to be gold standard ever, but visualization of vocal cords, chest rise accompanied with breathsounds, and co2 detection. On the floor all of this is confirmed with CXR.

I was going to disagree with you as in practice I have seen co2 detectors give false negatives. Of course when ever we use colormetric (every intubation) its always nice to see yellow/purple.

My info comes from my last ACLS which was 02 and still what my current employer is teaching. I did a search (http://www.acep.org/1%2C4924%2C0.html) which agrees with you.

I stand corrected-

ccrn

greg c
06-13-2004, 02:17
Originally posted by ccrn
QUOTE]Originally posted by greg c
NSTEMI- that's why he was going for an AM cath.

Its been a couple of years since I worked in ED so my memory is a little vague, but if I remember right we dont do Q wave or non-Q wave diagnosis anymore but ST elevation or non-ST elevation dx for intervention or thrombolitics (which arent in favor as much any more) for ACS.
ccrn [/QUOTE]

NSTEMI = Non-ST-Elevation-MI...I'm not sure what you're getting at with this paragraph...

ccrn
06-13-2004, 11:43
Originally posted by greg c
NSTEMI = Non-ST-Elevation-MI...I'm not sure what you're getting at with this paragraph...

Just thinking out loud, when I worked in a rural hospital it was part of the algorhithm that helped decide if we shipped to higher level of care (ie cath, CABG) or not and tx with thrombolitics (ie tnK).

You yourself seemed to question the validity of letting what I assume your cardiologist determined to be a "stable"NSTEMI pt sit until morning...

The algorithm has been updated, however as of 2003 AHA guidlines for primary and secondary intubation confirmation have not and co2 detectors were (are?) still secondary (www.americanheart.org).

I personaly could never trust one device to confirm placement 100% and not use assesment skills.

Our unit has many anesthesiology residents rotate through, some good some not so good. I'll talk to the head of their dept. If we (RN's) are outdated then we at least need to have our published info straight-

ccrn