What’s wrong with this ABG attempt?
Thread. On one of the most common pitfalls when doing vascular punctures and other bedside medicine procedures.
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Thread. On one of the most common pitfalls when doing vascular punctures and other bedside medicine procedures.
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Most inpatient medicine procedures involve putting a needle into a place where there’s fluid. Venipuncture, ABG, para, thora, LP, CVC, all same.
For each, you choose a spot on a skin to go through, and a direction in which to advance the needle to get to that place.
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For each, you choose a spot on a skin to go through, and a direction in which to advance the needle to get to that place.
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Knowing how deep below the skin the place is, and thus how deep your needle should be before you reach it, is critical.
In the case of a radial ABG, you should know that the artery is only a couple millimeters below the skin. Look, you can see it pulsating!
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In the case of a radial ABG, you should know that the artery is only a couple millimeters below the skin. Look, you can see it pulsating!
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Here it is on ultrasound. Less than 2mm deep.
BTW note the two radial veins on either side of the artery. They explain a lot of your unexpected P”a”O2s of 30.
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BTW note the two radial veins on either side of the artery. They explain a lot of your unexpected P”a”O2s of 30.
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So. You should expect to get a flash when your needle looks like this: all but a couple mm of it outside the skin.
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But if you’re here (same photo from intro) and haven’t gotten a flash, you missed the target >1 cm ago, and should not have advanced this much.
Either entry point was wrong, direction was wrong, or both.
Withdraw (entirely or almost), reorient, redirect, reattempt.
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Either entry point was wrong, direction was wrong, or both.
Withdraw (entirely or almost), reorient, redirect, reattempt.
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Realizing you missed is important, because it helps you avoid unnecessary trauma to deeper structures and get back on the right track sooner.
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Now, an ABG is easier because the target is superficial and the needle angle can be very acute. With deeper structures that require smaller approach angle (for threading a catheter), the needle path can be significantly longer than the target’s depth below the skin.
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But the principle is the same. Estimate the length of that diagonal path, and keep it in mind while advancing the needle.
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This pear biopsy redemonstrates the mental process of having a sense of how long your needle was, how much of it is visible, and thus how much of it is buried.
“I’m 7mm in.”
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“I’m 7mm in.”
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Summary:
- how deep is my target / how long is my expected needle path?
- how deep am I now?
- if I’m deeper than I expected I’ve probably missed, and should withdraw/redirect instead of advancing
Would love your input, #medtwitter
- how deep is my target / how long is my expected needle path?
- how deep am I now?
- if I’m deeper than I expected I’ve probably missed, and should withdraw/redirect instead of advancing
Would love your input, #medtwitter
