Bupivacaine (Marcaine)
Recommendations for Use in Perioperative Analgesia
Bupivacaine is a local anesthetic which blocks the generation and conduction of nerve impulses. It is commonly used
for analgesia by infiltration of surgical incisions. Preemptive use of analgesics (including local anesthetics used to
control post-operative pain) i.e. before tissue injury, is recommended to block central sensitization, thus preventing pain
or making pain easier to control.
Bupivacaine has a longer duration of action than lidocaine, to which it is chemically related - approx. 6-8 hours as
opposed to 1-2 hours for lidocaine. Duration of action is affected by the concentration of bupivacaine used and the
volume injected. Concentration affects the time for local anesthesia to occur and the density of the block. Volume
determines the area that is infiltrated and therefore anesthetized.
Total dose in mg/kg is important in local anesthetic toxicity. Signs of toxicity include central nervous system signs
(seizures), and cardiac dysrhythmias progressing to asystole. Bupivacaine toxicity is dose dependent, there is variation
between species and age of animals. Rats appear to be more tolerant than larger species (e.g. dogs, sheep, humans),
while rabbits are thought to be more sensitive.
Bupivacaine is a prescription drug, but it is not a controlled substance. It is available in concentrations of 0.25%, 0.5%
and 0.75%, either plain or combined with epinephrine (1:200,000). Epinephrine reduces cutaneous blood flow and
therefore prolongs the local anesthetic effects. Maximum concentration of bupivacaine recommended for subcutaneous
use is 0.25%. Higher concentrations are used mostly for caudal and epidural blocks in human medicine.
Bupivacaine injectable (0.25%), with or without epinephrine, in single dose vials of 10mls and 30mls, or multi-dose
vials of 50mls, is available from most veterinary supply houses.
Approximate cost is less than 50c/ml.
Vendors: NLS (A.J. Buck) – www.ajbuck.com, (800) 638-8674
Henry Schein – www.henryschein.com, (800) 552-8387
Bupivacaine Use
Dose rates from several sources recommend an upper limit of 2-3mg/kg for dogs and rats, 2mg/kg for rabbits.
However, if using undiluted bupivacaine 0.25% (2.5mg/ml) it may not be possible to inject a large enough volume to
have adequate local anesthetic effects without approaching toxic levels, especially in rodents and rabbits.
Therefore, LAS recommends the following:
Use a 0.125% solution (you can buy 0.25% Marcaine and dilute it 50/50 with saline) and a maximum dose of 2 mg/kg
body weight.
Before making the surgical incision, inject very small volumes (use a 25 gauge needle) at equidistant places
approximately 0.5-1.0 cm apart, in an ellipse around the incision site. Wait 3-5 minutes before starting the incision.
Continued analgesia can be maintained by repeating injections of bupivacaine (as described above) around the incision
at 6-8 hourly intervals.
For rodent surgical procedures such as ovariectomies or stereotaxic cranial surgery, a single injection of bupivacaine
prior to making the first surgical incision may be sufficient analgesia. As always, each animal should be monitored
for evidence of post-operative pain and additional pain relief provided when needed.
References
Boogaerts J; Declercq A; Lafont N; Benameur H; Akodad EM; Dupont JC; Legros FJ. Toxicity of bupivacaine
encapsulated into liposomes and injected intravenously: comparison with plain solutions. Anesthesia and Analgesia,
1993 Mar, 76(3):553-5.
Shafford, H.I. et al.: Preemptive analgesia: Managing pain before it begins. Veterinary Medicine June, 2001. (Copies
available fro LAS)
Wong, P.; Young, S. COMPMED archives, 1999.
|