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| Frequently Asked Questions |
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| Category #1 - Regional Anesthetics Pharmacology |
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| Buprenorphine addition |
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In your DVD, Orthopaedic Anesthesia, there is mention of adding buprenorphine to either ropivacaine or bupivacaine to enhance the block duration in single shot applications. I have searched for a reference in literature but cannot find one. Please advise on dosage and any articles in this regard.
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Please refer to the following literature:
The work of the Chicago based group indicated that by adding 0.3 mg of buprenorphine to the local anesthetic agent would increase the duration of the block three-fold. (Candido KD, Franco CD, Khan MA, et al. Buprenorphine added to local anesthetic for brachial plexus block to provide postoperative analgesia in outpatients. Reg Anesth Pain Med 2001; 26: 352 - 6). This is an excellent study and refers to other previous studies with buprenorphine. This is certainly also our experience. In principle, however, I am strongly opposed to long-acting blocks since not only will the block be long acting but you will also inherit long-acting side effects. A good example of this is DepoDur. This drug is well researched and its long-lasting side effects include: severe respiratory depression, hypoxia, pruritus, nausea and vomiting. It is no problem blocking the phrenic nerve, for instance, of a patient for six hours, but it becomes a huge problem if you block the phrenic nerve of that same patient for six days. Similarly, short-term respiratory depression with hypoxia is simple to manage, but it becomes another story if this lasts for 72 hours. I cannot caution enough against using these drugs.
In principle, if a long acting block is required, I would urge you to place a catheter rather than to resort to long acting medication. The infusion through a catheter can be manipulated. The volume and concentration of infusion can be adjusted up or down or even turned off if you have any unwanted adverse effects while this is not possible with long lasting single injection block. This is not dissimilar of the situation with intrathecal (subarachnoid or spinal) block versus epidural. If your aim is to have a bad day at the office, start using spinals (and its adverse effects) that last up to 3 - 5 days.
I trust that this answer is satisfactory. Please feel free to contact me personally or to place any further questions you may have on the website and address these questions to any of the excellent panel of experts that is available.
Sincerely,
André Boezaart
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| Do you use epinephrine in your local anesthetic?
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As a result of the work of Selander et al. (Acta Anaesthesiol Scand 1979 Apr, 23(2): 127-136), we believe that epinephrine is a risk factor for peripheral nerve damage due to ischemia, and avoid it in our infusions. We do, however, use epinephrine as a vascular marker when necessary. Epinephrine causes nerve ischemia, and because of that shortens the onset time of nerve blocks and causes blocks to be more dens. This ischemia may also be responsible for nerve damage if combined with other factors such as nerves in confined spaces, hematoma formation, large volume local anesthetics, etc, that may add to nerve ischemia.
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| What are your thoughts on coagulation and peripheral nerve blocks?
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Historically, the development of peripheral nerve blockade was motivated by the
continued need to provide adequate analgesia to patients in an era of increased
use of post-operative anti-coagulation by surgeons. Some people have suggested
that the guidelines we follow for neuraxial blockade in anti-coagulated patients
should be carried over to peripheral blocks. To begin with, the current guidelines
are based on a paucity of scientific data. Secondly, to make the assessment that
the risk of an extremely rare but potentially catastrophic event like an epidural
hematoma is equivalent to a much more common and likely benign event like a
subcutaneous hematoma is not based in fact. Likewise, everyday physicians around
the world place invasive monitors and do surgical procedures on patients with
coagulopathies. Therefore, it is our practice to be cognizant about coagulopathic
patients, and choose the least invasive techniques possible; however, we feel
peripheral nerve blockade, both single injection and continuous PERIPHERAL blocs,
can be safely utilized in the anti-coagulated patient. If we have to err, we err
on the side of safety, however.
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Do you mix your local anesthetics?
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It is our practice to determine which local anesthetic has the most desirable
profile for each particular indication, and to use that drug. If we are interested
in providing long-term analgesia, we place a catheter and we tend to keep the drugs simple.
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I have just finished watching the cervical paravertebral workshop movie on the
RASCI CD. (I believe it is the second edition CD.) During the narration, lidocaine
with epinephrine is discussed as one drug that may be used with this brachial
plexus catheter technique. I thought you taught us not to use epinephrine ever
when placing a peripheral nerve catheter. Please clarify this for me.
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| Answer: |
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I have just finished watching the cervical paravertebral workshop movie on the
RASCI CD. (I believe it is the second edition CD.) During the narration, lidocaine
with epinephrine is discussed as one drug that may be used with this brachial plexus
catheter technique. I thought you taught us not to use epinephrine ever when placing
a peripheral nerve catheter. Please clarify this for me. |
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