At the time of this writing, there are only three drugs approved by the U.S. Food and Drug Administration (FDA) for the intrathecal (“spinal”) route of administration: ziconotide, morphine, and baclofen.
Note the lack of local anesthetics on that list. Lidocaine? No. Hyperbaric bupivacaine? No. Good ‘ol tetracaine? Nope. All local anesthetics in the intrathecal space are off-label. Yet these are the very drugs that serve as the cornerstone for spinal anesthesia.
With a spinal needle and a few milliliters of local anesthetic like bupivacaine or lidocaine, we can achieve an anesthetic which enables surgeons to operate on the abdomen or lower extremities pain-free without any significant cardiopulmonary drawbacks. Sure, sympathectomies are a concern, but we’ve become extremely good at predicting and mitigating the effects of hypotension, tachy/bradycardias, etc.
For patients reading this concerned about the off-label use of local anesthetics in spinals… please keep in mind that there are MANY things we do in medicine which are off-label but well accepted practices. Spinal anesthetics are predictable, effective, and often times safer than general anesthesia. Just like everything else, we have to weigh the pros and cons and individualize our anesthetics for a patient, their operation, and their comorbidities.
Can’t say I’ve ever used lidocaine in a spinal due to risk of transient neurologic symptoms, but perhaps still being done at other institutions? Was a recent study published in one of the major anesthesia journals (anesthesiology?) that looked at the ED90 for PF morphine in spinals and found it to be 150mcg (they also looked at hydromorphone and arrived at 75mcg, I believe).
Thanks for sharing that info, Gabe! I also have never used lidocaine for spinals, but hey, lots of exam questions regarding TNS. 😉
Quite the cocktail there….I usually use 2.5 cc of standard bupi 0,5% with 25 mcg of fentanyl….. Never checked though whether the morphine we have was preservative free or not…
Never knew that…. I even use fentanyl/sufentanyl sometiles as adjuvants….. Every anesthesiologist shoud beware this fact should a lawsuit ever pop up…..
P.S: how much morphine sulphate do you usually give as adjuvant?
For a typical “C-section spinal”, I’ll use around 1.5 cc of hyperbaric 0.75% bupivacaine with the following additives: 10 mcg of fentanyl, 100 mcg of epinephrine, and 150 mcg of preservative-free morphine.