6 practical loco-regional blocks you should be using
Local anesthetics were once the singular mainstay of analgesia in medicine, and the modality now finds itself newly resurgent as a valuable and often integral part of the multimodal approach to pain management. Furthermore, recent evidence reveals local anesthesia is not only antinociceptive, it also elicits a constellation of positive immunomodulating, antimicrobial and tissue-healing effects.1,2
Following are six loco-regional blocks that deserve a second look and the recommended steps for administration.
1. Topical prilocaine/lidocaine creamFamiliar to many as the commercial product EMLA (AstraZeneca Pharmaceuticals), this cream also comes in generic form with 2.5% of each local anesthetic (lidocaine and prilocaine). The prilocaine penetrates skin and makes placement of an intravenous catheter painless, resulting in numerous benefits such as faster placement and diminished frustration. Topical lidocaine/prilocaine cream also can be used to ease the experience of phlebotomy in sensitive "touch-me-not" patients and to facilitate subcutaneous injection of microchips, fluids, local anesthetics, and so on. To administer, follow these steps:
2. Topical 5% lidocaine patch
Available only as the trade product Lidoderm (Endo Pharmaceuticals), the 10-x-14-cm patch is used to relieve the pain of post-herpetic neuralgia, also referred to as after-shingles pain, in people. However, lidocaine has many potential veterinary uses as a dermal differential blockade, meaning it will prevent pain but not the sense of touch or pressure. Common uses include postoperative application around larger or potentially more painful surgical or trauma sites and on limbs at the site of osteosarcoma or other metastatic bone cancers. In people, the lidocaine patch has been used for breakthrough osteoarthritis pain.3 The lidocaine, all 700 mg of it, is embedded in the self-adhesive patch, which can be cut to the desired size and shape. Studies in both dogs and cats reveal negligible plasma concentrations, even when the entire patch is placed for several days on normal skin4,5 (concentrations may be higher on inflamed skin). Here's how best to administer this local anesthetic:
3. Line and infiltrative blocks
These blocks are sublime, but far too often overlooked, parts of a multimodal perioperative protocol. Human medical studies show that these local blocks improve pain scores and decrease the need for other analgesics such as opioids. The veterinary literature, however, is more sparse on this matter, with three studies demonstrating a positive effect6-8 and one recent study that could not detect a difference in pain scores with the use of line blocks in elective spay/neuter procedures.9 The latter study's results may have been complicated, in part, by errors in technique. More important, the pain-scoring systems used in that study may not have been sensitive enough to detect differences with the use of local anesthetics, since all of the patients also received NSAIDs and opioids. Nevertheless, line blocks and subcutaneous infiltrative blocks are simple, safe, inexpensive and widely accepted as effective means of contributing to postoperative patient comfort.