Injecting Some Sense Into The Dogma On Aspiration And Nerve Blocks

Paldog Rinpoche must have bonded with me in my short time during my visit to his palace a few weeks ago in Tibet as I received a scroll from him on my doorstep this morning. The Paldog does not send texts or emails. He sends Tibetan scrolls.

Now this was some cool deal as I had never received a scroll before. The excitement of not only receiving something with this type of rarity but anticipating what sage advice it contained lit up my nucleus accumbens like an August forest fire in the high and dry Sonoran desert.

Fully unfurled, the beautiful parchment epistle said only one word in the most intriguing and artisan calligraphy: Aspiration. The Paldog was a great mind game player and he was now tickling my cortex like a maid brigade with a battalion of feather dusters. I thought, “What the hell could he be referring to with this one word advice?”

It took me a while and then I figured it out, but how did he know about the dogma of aspiration during posterior tibial nerve blocks? He loves busting up dogma (or at least challenging it) more than I do. We had discussed why dogma stays with us so long when the science dispels any notion of most of these long held but misguided beliefs. I remember him telling me, “Humans love to hang on to dogma because it has been their belief for so long they can’t give it up. We do not like change and we do not like mental change even more.”

But that is what made him so cool. Few men like him have reached an intellectual level of such erudition but also of an equal calmness and humbleness that is so scarce, it is almost unrecognizable in the general population of those pretend sages. Aspiration? What in the hell was he guiding me to?

After my six of usually eight daily cups of Joe (0.8 of my needed caffeine titer), I started thinking back to an encounter I had just a couple of days ago while teaching a Heel Pain Boot Camp. We were discussing the techniques of posterior tibial nerve blockade and how we all learned to aspirate after needle placement to avoid infiltration into the vascular tree with the local anesthetic.

So I asked the class how many of them used a 30-gauge needle? Half the hands went up. Then how many of them used a 27-gauge needle? All but one hand went up.

“What gauge do you use?” I asked the last remaining holdout. “A 25 gauge,” she quickly replied.

“How many of you inject bupivacaine in your blocks?” I asked them. All hands rose. “Why do you aspirate?” Aside from the three or four who said, “that was the way we were taught,” there were a couple of additional responses.

“To prevent local anesthetic toxicity,” one very astute respondent simply stated. “Bupivacaine can cause an irreversible cardiotoxicity and I can prevent that with aspiration.” This was one of the “30-gaugers” by the way.

“Oh,” I said. Now I was circling him like a hawk over a wounded rabbit. “Are you aware of the literature about needle aspiration during the administration of local anesthetics?”

They looked up at me with quizzical looks on their faces. “What do you mean?” they blurted out in unison.

“Let me tell you. It is relatively easy to kill someone with a local anesthetic, especially if you are injecting bupivacaine. Get it into the pipe and you could have an irreversible cardiac event.”¹

I paused for effect. “Now there are a lot of articles which allude to the fact that there may be a false sense of security from aspiration techniques during the administration of a local anesthetic dealing with different gauges of needles. Fact is, you can’t really rely on the fact that when you pull back the syringe and there is no blood visible, that you are not within the vascular tree — especially with small gauge needles like the 30s that I so dearly love.”²

One of the attendees raised his hand. “Isn’t there a way to reverse the cardiotoxicity of bupivacaine?”

“Yes there is,” I said, “but it is sketchy at best. You can use a 2% lipid emulsion treatment and good support, but chances are you have got a serious problem.”³

“So what are we supposed to do?” he fired back.

“First of all, don’t use bupivacaine in a posterior tibial block. Use lidocaine. You can inject lidocaine right into the vein and chances are patients get a metallic taste at worst. Interestingly, there are some recent articles espousing the efficacy of IV administration of lidocaine for the treatment of sepsis in multiple organ system failure by its immunologic and anti-inflammatory effects.”⁴

“So yeah, you can inject it into the venae comitantes and not kill them. Not the case with bupi,” as my Spanish colleagues call it. “Next thing you might want to do is guide your injections with real time ultrasonography. Less chance of getting it into their circulation.”⁵

I circled the darkened room and remembered one other pearl. “Use your ultrasound to locate the nerve and sometimes come in with an approach just posterior to the medial malleolus in real time. Oh by the way, you are doing better medicine and, believe it or not, they will recompense you for the effort you make.”

Finally, if you want to make fewer kids cry and inflict less pain, use 30-gauge needles.⁶ Just be careful and stick with the innocuous juice.

References

1.      Dudley MH, Fleming SW, Garg U, Edwards JM. Fatality involving complications of bupivacaine toxicity and hypersensitivity reaction. J Forensic Sci. 2011; 56(5):1376-1379.

2.      Cooley RL, Robison SF. Comparative evaluation of the 30-gauge dental needle. Oral Surg Oral Med Oral Pathol. 1979; 48(5):400-404.

3.      Chen H, Xia Y, Zhu B, Hu X, Xu S, Chen L, Papadimos TJ, Wang W, Wang Q, Xu X. Measurement of the efficacy of 2% lipid in reversing bupivacaine- induced asystole in isolated rat hearts. BMC Anesthesiol. 2014; 14:60.

4.      Berger C, Rossaint J, Van Aken H, Westphal M, Hahnenkamp K, Zarbock A. Lidocaine reduces neutrophil recruitment by abolishing chemokine-induced arrest and transendothelial migration in septic patients. J Immunol. 2014; 192(1):367-376.

5.      Choi S, McCartney CJ. Evidence base for the use of ultrasound for upper extremity blocks: 2014 update. Regional Anest Pain Med. 2014; epub Nov. 5.

6.      Ram D, Hermida BL, Amir E. Reaction of children to dental injection with 27- or 30-gauge needles. Int J Paediatr Dent. 2007; 17(5):383-387.