Question:

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.

Answer:

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 also our experience. In principle, however, I am 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 five or 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. That way you remain in charge of the situation:  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

Question:

Do you use epinephrine in your local anesthetic?

Answer:

As a result of the work of Selander et al. (Acta Anaesthesiol Scand 1979 Apr, 23(2): 127-136) and others, 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 blocks that are 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.

Question:

What are your thoughts on coagulation and peripheral nerve blocks?

Answer:

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.  The very reason for the development of continuous peripheral nerve block was the popularity of enoxaparin and its implications during epidural analgesia.   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 blocks, can be safely utilized in the anti-coagulated patient. If we have to err, we err on the side of safety, however.

For practical purposes we regard paraneuraxial epidural blocks (all paravertebral blocks – cervical, thoracic, lumbar and sacral) similar to neuraxial epidural blocks in all regards.  That is equipment used (yes, 10-gauge epidural Tuohy needles for single shot paravertebral blocks!!) test dosing, etc, and even including anticoagulation rules.  Jaqcues Chelly and his colleagues from Pittsborough have, however, shown that this is probably not necessary and we are starting, in selected cases, to follow his lead.

Question:

Do you mix your local anesthetics?

Answer:

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.  Like mixing drinks, mixing your drugs can be painfull.  I advise you not to do that.   If you need a short onset time, use ropivacaine and place the needle (or catheter) in the same fascial compartment as the nerve.  If you need a long duraion, use a catheter (they are (much) less prone to problems than single shot blocks!).  If you need to test for intravascular injection test for it with a separate injection.

On a lighter note, apart from the pain of mixing drinks, mixing your local anesthetic drugs (or any drug for that matter) is such a “surgeon” thing to do.  It is so based on the fatasy that you get a short onset and long duration of action.  But think of it, if you mix 10 mL of bupivacaine 0.5% with 10 mL lidicaine 2% what do you get?  Big deal, you get 20 mL 0.25% bupivacaine and 20 mL 1% lidicaine.  The only positive is you don’t get 40 mL but 20 + 20 = 20 in this case.