ORIGINAL ARTICLE Lidocaine containing high concentrations of a vasoconstrictor: is it safe for infiltration anesthesia? Nasser Vesal & Alireza Raayat Jahromi & Ahmad Oryan Received: 1 August 2011 /Accepted: 12 October 2011 /Published online: 9 November 2011 # Springer-Verlag London Limited 2011 Abstract For economical and practical reasons, flank laparotomy performed on cattle is done while the animal is standing. To prolong the duration of surgical anesthesia with local anesthetic drugs, vasoconstrictors are commonly added to delay absorption and reduce the systemic toxicity. The purpose of this study was to examine the effects of lidocaine containing either 80 μg ml -1 norepinephrine or 12.5 μg ml -1 epinephrine on tissue integrity following flank inverted L infiltration anesthesia in sheep. Results of histologic examination of the skin and subcuta- neous tissue sections by light microscopy showed significant pathologic changes (inflammatory changes and necrosis) of the epidermis and dermis in sheep receiving lidocaine containing 80 μg ml -1 norepinephrine. Because of the potential for skin and muscle necrosis and injection site inflammation, lido- caine with a high concentration of a vasoconstrictor is not recommended for infiltration anesthesia. Keywords Lidocaine . Epinephrine . Local anesthesia . Inverted L . Sheep Introduction In ruminants, surgical procedures are commonly performed under local or regional anesthesia. In cattle, in particular, surgeries of the digestive tract (abomasopexy, omentopexy, rumenotomy and intestinal obstruction, and volvulus), and cesarean sections are often performed on the standing animal without sedation (Ivany and Muir 2005). Thoraco- lumbar paravertebral block, as a regional analgesic tech- nique, is routinely used for flank laparotomy and is generally considered preferable to infiltration anesthesia such as a line block or inverted L block. However, some practitioners may prefer to use the inverted block to provide anesthesia of the flank region in the field because of the ease of performing the technique (Skarda and Tranquilli 2007b). Lidocaine HCl, the first aminoamide-type drug, is the most commonly used local anesthetic in veterinary clinical practice. It has a rapid onset and moderate duration of action and causes vasodilation. Its vasodilatory effect results in faster removal of local anesthetics from the site of injection. Although both 1% and 2% solutions of lidocaine are recommended for infiltration anesthesia in cattle (Ivany and Muir 2005), a 2% solution is commonly used by practitioners in the field situation to provide faster and more prolonged anesthesia. Vasoconstrictors, usually epinephrine, have been used for decades as a useful additive to local anesthetic solutions. Because of its vasoconstrictive properties, epi- nephrine delays systemic absorption of local anesthetics and therefore improves the duration of anesthesia and decreases the risk of systemic toxicity (Skarda and Tranquilli 2007a; Berde and Strichartz 2010). Epinephrine in a concentration of 1:200,000 (5 μg ml -1 ) to 1:50,000 (20 μg ml -1 ) has been used to improve the local anesthetic effect of lidocaine (Ivany and Muir 2005; Greene 2003). There have been several reports from general practi- tioners that a brand of lidocaine solution containing 80 μg ml -1 norepinephrine has caused tissue necrosis when injected for inverted L block before flank laparotomy in N. Vesal (*) : A. Raayat Jahromi Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Shiraz University, 71345-1731, Shiraz, Iran e-mail: nv1340@shirazu.ac.ir A. Oryan Department of Pathobiology, School of Veterinary Medicine, Shiraz University, 71345-1731, Shiraz, Iran Comp Clin Pathol (2012) 21:1703–1706 DOI 10.1007/s00580-011-1352-y