Effects on Tissue
The effects of local anesthetics on wound healing have been investigated in many in vitro and in vivo models. While there is some evidence that these drugs alter the cellular events of early tissue healing, there does not appear to be a clinically significant impact on wound healing or mechanical wound strength in animals or humans.14 In addition, the clinical use of local anesthetics has not been associated with increased risk of surgical site infection.15 Local anesthetics as a class have been shown to have antimicrobial properties in vitro. Several studies have found that concentrations of bupivacaine HCl between 0.125% and 0.75% are able to inhibit the growth of pathogenic bacteria and fungi, including Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, Candida albicans, and others.16, 17
However, bupivacaine and other local anesthetics have demonstrated chondrotoxicity, particularly when delivered in high concentration or with extended duration of exposure to compromised cartilage. The implication of a single intra-articular injection of a local anesthetic, as may be performed at the time of orthopedic surgery, is currently unclear. Therefore, high doses of intra-articular local anesthetics should be avoided.17
Incisional block, either preoperatively or at the time of wound closure, has been advocated as a means of enhancing multimodal perioperative pain management.18 This technique may use lidocaine, bupivacaine, or a combination of both, although the clinical benefits for combination remain unclear. Bupivacaine can be instilled through a needle into the subcutaneous tissue along the incisional line and is expected to provide several hours of analgesia post-operatively. If extended duration of analgesia is desired, a wound soaker catheter may be placed. Repeated administration of a local anesthetic through this catheter can provide extended analgesia throughout the hospitalization or pain management period. However, soaker catheters can pose their own challenges as they are at risk for accidental, premature removal and/or may contribute to increased surgical-site infection rate.
Challenges in the Early Post-Operative Period
Local anesthetics are also used for regional nerve blocks, and these techniques have demonstrated a significant enhancement of post-operative analgesia in pets. However, the duration of analgesia using these techniques is limited due to the duration of action of current formulations, and the transient motor dysfunction that some animals experience may provide additional challenges in the early post-operative period.
While local anesthetics have demonstrated a beneficial role in companion animal pain management in the immediate post-operative period, these drugs do not provide effective prolonged analgesia in their traditional single-dose administration formulation for patients discharged from the hospital soon after surgery or for patients requiring extended hospitalization.
14. Abrao J, Fernandes CR, White PF, et al. Effect of local anaesthetic infiltration with bupivacaine and ropivacaine on wound healing: a placebo-controlled study. Int Wound J. 2014;11(4):379-385.
15. Liu SS, Richman JM, Thirlby RC, Wu CL. Efficacy of continuous wound catheters delivering local anesthetic for postoperative analgesia: a quantitative and qualitative systematic review of randomized controlled trials. J Am Coll Surg. 2006;203(6):914-932.
16. Johnson SM, Saint John BE, Dine AP. Local anesthetics as antimicrobial agents: A review. Surg Infect (Larchmt). 2008;9(2):205-213.
17. Piper SL, Kramer JD, Kim HT, Feeley BT. Effects of local anesthetics on articular cartilage. Am J Sports Med. 2011;39(10):2245-2253.
18. Savvas I, Papazoglou LG, Kazakos G, Anagnostou T, Tsioli V, Raptopoulos D. Incisional block with bupivacaine for analgesia after celiotomy in dogs. J Am Anim Hosp Assoc. 2008;44(2):60-66.