Systemic and local effects of lidocaine or mepivacaine when used for intravenous regional anaesthesia of the distal limb in standing sedated horses.

BACKGROUND: Local anaesthetics are being combined clinically with amikacin in intravenous regional limb perfusion (IVRLP), with limited knowledge on the analgesia provided and its onset and duration of action after tourniquet application and release. OBJECTIVE: To evaluate the systemic clinical effect, limb withdrawal to nociceptive stimulation, and plasma and synovial fluid concentrations after IVRLP with lidocaine or mepivacaine in standing sedated horses. STUDY DESIGN: Prospective, controlled, randomised, cross-over study. METHODS: Six healthy adult horses were sedated and received IVRLP with lidocaine, mepivacaine or saline (negative control), or perineural anaesthesia of the medial and lateral palmar and palmar metacarpal nerves (positive control) in one forelimb with a 3-week washout period between trials. Electrical and mechanical stimuli were used to test nociceptive threshold of the limb before and after IVRLP/perineural anaesthesia. For lidocaine and mepivacaine trials, blood was collected from the jugular vein and synovial fluid from the radiocarpal joint before, during and out to 24 hours after IVRLP. Drug concentrations were measured using high-performance liquid chromatography. RESULTS: Nociceptive thresholds for lidocaine, mepivacaine and perineural anaesthesia trials were significantly increased compared with saline and baseline values at 10, 20 and 30 minutes, with no differences between anaesthetic trials. During this time, horses had lower heart rates than IVRLP with saline. After tourniquet release at 30 minutes, nociceptive thresholds for lidocaine and mepivacaine trials gradually returned to baselines, whereas perineural anaesthesia trial remained unchanged out to an hour. Plasma lidocaine and mepivacaine concentrations were ≤50 ng/mL while the tourniquet was in place, significantly increasing 10 minutes after tourniquet release. Maximal lidocaine and mepivacaine concentrations in synovial fluid were reached 25 minutes after IVRLP injection. MAIN LIMITATIONS: Amikacin was not included in the perfusate. CONCLUSION: Similar to perineural anaesthesia, IVRLP with lidocaine or mepivacaine provides anti-nociception to the distal limb in standing sedated horses while a tourniquet is applied with concentrations remaining below toxic levels in plasma and synovial fluid.

Prevalence of dog erythrocyte antigens in retired racing Greyhounds.

BACKGROUND: Blood groups in dogs are designated as dog erythrocyte antigen (DEA) 1.1, 1.2, 3, 4, 5, 7, and Dal. There is limited information about the frequency of different antigens in Greyhound dogs, despite their frequent use as blood donors. OBJECTIVES: The aims of this study were to determine the frequencies of DEA 1.1, 1.2, 3, 4, 5, and 7 in Greyhounds, to compare the frequencies with those of non-Greyhound dogs, and to evaluate the presence of naturally occurring anti-DEA antibodies. METHODS: Blood was collected from 206 Greyhound and 66 non-Greyhound dogs being screened as potential blood donors. Blood-typing was performed at Animal Blood Resources International by tube agglutination utilizing polyclonal anti-DEA antibodies. RESULTS: Of the Greyhound dogs, 27/206 (13.1%) were positive for DEA 1.1, and this frequency was significantly lower (P<.0001) than for non-Greyhound dogs of which 40/66 (60.6%) were DEA 1.1-positive. The frequency of positivity for both DEA 1.1 and 1.2 was also lower in Greyhounds (P<.0001). There were no significant differences between Greyhounds and non-Greyhounds for DEA 1.2, 3, 4, 5, or 7. All 137 dogs (113 Greyhounds and 24 non-Greyhounds) that were evaluated for naturally occurring anti-DEA antibodies in serum were negative. A higher percentage of Greyhound dogs (57.3%, 118/206) were considered "universal donors" (negative for all DEAs except DEA 4) compared with non-Greyhound dogs (28%, 13/46). CONCLUSION: The frequency of positivity for DEA 1.1 in our population of Greyhounds was significantly lower than previously reported for dogs. Furthermore, a large majority of Greyhounds met the criteria for universal donors.