Increasing tourniquet number has no effect on amikacin concentration within the radiocarpal joint in horses undergoing intravenous regional limb perfusion.

OBJECTIVE: To determine whether IV regional limb perfusion (IVRLP) performed in the cephalic vein with a wide rubber tourniquet (WRT) applied proximal and distal to the carpus results in a higher peak concentration (Cmax) of amikacin in the radiocarpal joint (RCJ), compared with the Cmax for IVRLP using a single WRT proximal to the carpus. ANIMALS: 7 healthy adult horses. PROCEDURES: Horses underwent IVRLP using standing sedation with 2 g of amikacin sulfate diluted to 60 mL by use of saline (0.9% NaCl) solution in the cephalic vein with 2 different tourniquet techniques; proximal WRT (P) and proximal and distal WRT (PD). Synovial fluid was collected from the RCJ at 5, 10, 15, 20, 25, and 30 minutes after IVRLP. Tourniquets were removed after the 30-minute sample was collected. Blood samples from the jugular vein were collected at 5, 10, 15, 20, 25, 29, and 31 minutes after IVRLP. Amikacin concentration was quantified by a fluorescence polarization immunoassay. Median peak concentration (Cmax) of amikacin and time to maximum drug concentration (Tmax) within the RCJ were determined. RESULTS: Median peak concentration in the RCJ was 1331.4 µg/mL with technique P and 683.1 µg/mL with technique PD. Median Tmax occurred at 30 minutes with technique P and 25 minutes with technique PD. No significant (Cmax, P = 0.18; Tmax, P = 0.6) difference in amikacin Cmax or Tmax between techniques was detected. CLINICAL RELEVANCE: Placement of 2 WRTs offers no advantage to a single proximal WRT when performing IVRLP to deliver maximal amikacin concentrations to the RCJ using IVRLP.

Hemorrhage control-Proper application of direct pressure, pressure dressings, and tourniquets for controlling acute life-threatening hemorrhage.

BACKGROUND: Timely application of hemorrhage control interventions is lifesaving. Any amount of blood loss may be detrimental and, therefore, trauma-induced hemorrhage must be addressed immediately and aggressively. Early and prompt hemorrhage control is one of the main priorities of treating hemorrhagic shock. Trauma-induced hemorrhage remains a leading cause of preventable death. A vast majority of bleeding wounds encountered are not initially life-threatening but become life-threatening with delay in appropriate hemorrhage control. DESCRIPTION: Appropriate immediate hemorrhage control interventions for the exsanguinating small animal include direct pressure, wound packing, hemostatic dressings, pressure bandage, and, possibly, tourniquet application. Although tourniquet application is a lifesaving intervention in people experiencing extremity hemorrhage, it has not been shown to be a necessary intervention for small animals. SUMMARY: The aim of this companion article is to briefly describe the basic methods for achieving immediate hemorrhage control in small animals in a prehospital or life-threatening situation. KEY POINTS: Common sources of trauma-induced massive hemorrhage include injury to a major artery or other large vessel (eg, external jugular), a highly vascular organ(s) (liver and spleen), or from a combination thereof. Blood loss from a major arterial source (ie, femoral or carotid artery) may rapidly lead to exsanguination and death in as little as 3-5 min. Placing a circumferential compressive bandage that is too tight or restrictive around the neck, thorax, or abdomen may occlude the patient's airway, restrict chest expansion, or prevent adequate respiration. Noncircumferential bandages often do not generate sufficient enough pressure to abate arterial hemorrhage, particularly when systolic arterial blood pressure is restored postfluid resuscitation. Definitive hemostasis for massive internal hemorrhage is best achieved through early surgical intervention. Direct pressure remains the most effective "medical" intervention for initial hemorrhage control. When feasible, elevate and splint (immobilize) any bleeding extremity or body part as an adjunctive aid for hemorrhage control when used in conjunction with other methods of control, especially direct pressure.

Subtourniquet pressures generated by application of wide-rubber tourniquets in standing, sedated horses.

OBJECTIVE: To determine the influence of location and movement on subtourniquet pressure (STP) generated by application of a wide-rubber tourniquet (WRT) on equine limbs. STUDY DESIGN: Randomized experimental cross-over design. ANIMALS: Six standing, sedated horses. METHODS: Horses were sedated with detomidine hydrochloride (0.2 µg/kg IV), and 4 investigators applied WRTs to the antebrachium (AB), gaskin (GK), and midmetacarpus (MC) of each horse in a predetermined, randomized order. Subtourniquet pressure was consequently measured at 10-minute intervals (T0, T10, T20, T30) for 30 minutes. Indirect systolic blood pressure (SBP) was measured presedation, postsedation, and throughout the tourniquet application period. Target STP was established as SBP + 100 mm Hg. Limb movements at each location were classified as none, low, moderate, or high, on the basis of counts and magnitude. RESULTS: Mean STP did not change with time (P = .93) and exceeded SBP by 163 mm Hg (95% CI 122-205), 185 mm Hg (95% CI 156-214), and 402 mm Hg (95% CI 351-454) at the AB, GK, and MC, respectively. Mean STP at each location exceeded the target STP in 59 of 70 (81%) of the trials. Limb movements affected STP generated by tourniquets at the AB (P = .04) and MC (P < .0001) but not at the GK (P = .67). CONCLUSION: Wide-rubber tourniquets applied at the AB, GK, and MC generated STP >100 mm Hg above SBP for 30 minutes in standing, sedated horses. CLINICAL SIGNIFICANCE: Wide-rubber tourniquets as applied in this study can achieve and maintain the current recommended STP (SBP + 100 mm Hg) for equine IV regional limb perfusion. Number and magnitude of limb movement can decrease STP over time, potentially reducing the efficacy of a WRT.

Time required to achieve maximum concentration of amikacin in synovial fluid of the distal interphalangeal joint after intravenous regional limb perfusion in horses.

OBJECTIVE To determine the maximum concentration (Cmax) of amikacin and time to Cmax (Tmax) in the distal interphalangeal (DIP) joint in horses after IV regional limb perfusion (IVRLP) by use of the cephalic vein. ANIMALS 9 adult horses. PROCEDURES Horses were sedated and restrained in a standing position and then subjected to IVRLP (2 g of amikacin sulfate diluted to 60 mL with saline [0.9% NaCl] solution) by use of the cephalic vein. A pneumatic tourniquet was placed 10 cm proximal to the accessory carpal bone. Perfusate was instilled with a peristaltic pump over a 3-minute period. Synovial fluid was collected from the DIP joint 5, 10, 15, 20, 25, and 30 minutes after IVRLP; the tourniquet was removed after the 20-minute sample was collected. Blood samples were collected from the jugular vein 5, 10, 15, 19, 21, 25, and 30 minutes after IVRLP. Amikacin was quantified with a fluorescence polarization immunoassay. Median Cmax of amikacin and Tmax in the DIP joint were determined. RESULTS 2 horses were excluded because an insufficient volume of synovial fluid was collected. Median Cmax for the DIP joint was 600 µg/mL (range, 37 to 2,420 µg/mL). Median Tmax for the DIP joint was 15 minutes. CONCLUSIONS AND CLINICAL RELEVANCE Tmax of amikacin was 15 minutes after IVRLP in horses and Cmax did not increase > 15 minutes after IVRLP despite maintenance of the tourniquet. Application of a tourniquet for 15 minutes should be sufficient for completion of IVRLP when attempting to achieve an adequate concentration of amikacin in the synovial fluid of the DIP joint.

Effects of tourniquet number and exsanguination on amikacin concentrations in the radiocarpal and distal interphalangeal joints after low volume intravenous regional limb perfusion in horses.

OBJECTIVE: To determine the influence of a dual tourniquet technique and limb exsanguination on amikacin concentrations in the synovial fluid of the radiocarpal joint (RCJ) and distal interphalangeal joint (DIPJ) after low volume, cephalic intravenous regional limb perfusion (IVRLP). STUDY DESIGN: Randomized cross-over design. ANIMALS: Six healthy adult horses. METHODS: One gram of amikacin in 6 mL of 0.9% NaCl was infused via cephalic IVRLP in 6 standing, sedated horses using 4 techniques: proximal pneumatic tourniquet (P), proximal pneumatic tourniquet with exsanguination (PE), proximal pneumatic and distal Esmarch tourniquet (PD), and proximal pneumatic with distal Esmarch tourniquet and exsanguination (PDE). Amikacin concentrations were measured in RCJ and DIPJ synovial fluid samples, collected just before perfusion (time 0), and at 15 and 30 minutes (before tourniquet release) after perfusion. RESULTS: Synovial fluid amikacin concentrations achieved in the RCJ were higher with techniques PD and PDE than those achieved with techniques P and PE 15 and 30 minutes after perfusion (P < .0001). Synovial fluid amikacin concentrations in the DIPJ were higher with techniques P and PE than those achieved with techniques PD and PDE at 15 minutes (P = .0002) and were higher than technique PDE at 30 minutes after perfusion (P < .0001). CONCLUSION: Low volume (10 mL) cephalic IVRLP should be combined with the placement of 2 tourniquets (proximal and distal to the carpus) to achieve therapeutic amikacin concentrations in the RCJ. Exsanguination prior to low volume IVRLP does not alter synovial fluid amikacin concentrations.

The Effects of Mepivacaine Hydrochloride on Antimicrobial Activity and Mechanical Nociceptive Threshold During Amikacin Sulfate Regional Limb Perfusion in the Horse.

OBJECTIVE: To determine the effect of intravenous regional limb perfusion (IVRLP) with a combination of mepivacaine hydrochloride and amikacin sulfate on synovial fluid amikacin sulfate concentration, antimicrobial activity, and mechanical nociceptive threshold (MNT). STUDY DESIGN: Experimental study. ANIMALS: Healthy adult horses (n=9). METHODS: One IVRLP treatment was randomly administered by cephalic vein of each limb: amikacin alone (1 g amikacin in 60 mL saline) or amikacin with mepivacaine (1 g amikacin and 500 mg mepivacaine in 60 mL saline). Opposite treatments were repeated after a 24 hour wash-out period. Amikacin concentration and antimicrobial activity were determined for synovial fluid from middle carpal joints at tourniquet removal and 30 minutes following. Zone of inhibition was determined for Staphylococcus aureus and Escherichia coli. MNT was determined at 3 dorsal metacarpal locations prior to and after sedation, after Esmarch tourniquet application, and 30 minutes after IVRLP prior to and after tourniquet removal. RESULTS: Two limbs from each treatment group were removed because of undetectable amikacin concentrations for a total of 14 data sets analyzed. Synovial fluid amikacin concentrations and zone of inhibition were not significantly different between treatments at any time point. MNT were significantly increased 30 minutes after IVRLP prior to and following tourniquet removal using amikacin and mepivacaine (median, range; 40.0 µg/mL, 38.7-40.0 and 40.0, 25.8-40.0, respectively) compared to amikacin alone (19.5 µg/mL, 18.7-25.6 and 15.3, 13.2-20.5, respectively). CONCLUSION: Addition of mepivacaine to amikacin for IVRLP in the horse as a means of providing analgesia without decreasing antimicrobial activity.

Evaluation of 10-minute versus 30-minute tourniquet time for intravenous regional limb perfusion with amikacin sulfate in standing sedated horses.

The objective of the article is to determine the synovial fluid concentrations of amikacin sulfate (AS) after performing an intravenous regional limb perfusion (IVRLP) with the tourniquet in place for 10 minutes and compare this with 30 minutes. This is a randomised crossover experimental design. Animals were seven healthy adult horses. Horses underwent two IVRLP procedures in a randomised, crossover design. The horses received IVRLP with 2 g AS diluted to 60 ml using 0.9% saline in the cephalic vein of alternate limbs with the tourniquet in place for either 10 or 30 minutes, with a washout period between procedures. Movement of the horses was recorded. Synovial fluid was collected from the radiocarpal and metacarpophalangeal joints at five minutes and 24 hours after IVRLP, and amikacin concentration was compared between groups. Amikacin was quantified by a fluorescence polarisation immunoassay. There was no significant difference between the synovial amikacin concentrations noted between 10 minute and 30 minute IVRLP. Horses in the 30 minute tourniquet application group demonstrated more movement than the 10 minute tourniquet group. There was a significant difference between groups with regard to the systemic venous blood concentration of amikacin one minute after tourniquet release with mean systemic venous blood concentrations of AS being higher (P=0.001) in the 10 minute group. Ten minute application of a wide elastic tourniquet may be sufficient when performing IVRLP in standing sedated horses.

Comparison of two tourniquet application times for regional intravenous limb perfusions with amikacin in sedated or anesthetized horses.

Regional limb perfusion (RLP) in horses has proven to be a simple and effective technique for the treatment of synovial and musculoskeletal infections in the distal portion of the limbs. The ideal tourniquet time needed to achieve therapeutic synovial concentrations remains unknown. The pharmacokinetic effects of general anesthesia (GA) versus standing sedation (SS) RLP on synovial amikacin concentrations are not completely understood. This study investigated the pharmacokinetic effects of RLP under general anesthesia (GA) versus standing sedation (SS) on synovial amikacin concentration following 20 or 30 min tourniquet time. Using 1 g of amikacin RLP was performed in two groups of six horses (GA and SS). A pneumatic tourniquet was applied proximal to the carpus and maintained for 20 or 30 min. Two weeks later, the opposite treatment (20 or 30 min) was randomly performed in the opposite limb of horses in each group (GA and SS). Synovial fluid samples were collected from the metacarpophalangeal (MCP) and radiocarpal (RC) joints. Amikacin was quantified by a fluorescence polarization immunoassay. Regardless of the group, no significant difference in the synovial amikacin concentrations was noted between 20 and 30 min RLP. Mean synovial concentrations of amikacin in the standing sedated horses were significantly higher in the MCP joint at 30 min (P = 0.003) compared to horses under general anesthesia. No significant difference was noted for the RC joint.

Microdialysis measurements of equine lamellar perfusion and energy metabolism in response to physical and pharmacological manipulations of blood flow.

REASONS FOR PERFORMING STUDY: A suitable method for evaluating lamellar perfusion changes and their metabolic consequences is currently lacking. OBJECTIVES: To examine perfusion changes in lamellar tissue using serial microdialysis measurements of urea clearance and energy metabolites. STUDY DESIGN: Randomised, controlled (within subject) experimental trial. METHODS: Nine Standardbred horses were instrumented with microdialysis probes in the foot lamellar tissue and skin (over the tail base). Urea (20 mmol/l) was added to the perfusate and its clearance was used to estimate local perfusion. Samples were collected every 15 min for a 1 h control period, then during application of a distal limb tourniquet, during periods when norepinephrine or potassium chloride (KCl) were included in both skin and lamellar perfusates, and after systemic (intravenous) acetylpromazine. Dialysate concentrations of glucose, lactate, pyruvate and urea were measured and lactate:glucose (L:G) and lactate:pyruvate (L:P) ratios calculated. Values were compared with pre-intervention baseline and also between simultaneous skin and lamellar samples using nonparametric statistical methods. RESULTS: Lamellar glucose decreased and lactate, urea, L:G and L:P increased significantly with tourniquet application, without significant changes in skin dialysate values. Lamellar and skin glucose decreased and L:G increased significantly during norepinephrine infusion, but mild increases in urea were not significant at either site. KCl caused significant decreases in lamellar and skin L:G, and an increase in skin glucose, but did not affect urea clearance. Acetylpromazine caused profound decreases in lamellar glucose and L:P, with increased L:G and pyruvate, but did not affect urea clearance or any skin dialysate values. CONCLUSIONS: Significant changes in microdialysis urea clearance only occurred with severe lamellar hypoperfusion. However, changes in dialysate metabolite concentrations reflected less profound fluctuations in perfusion. This method may be useful for examining lamellar perfusion and energy balance during laminitis development and for the evaluation of vasoactive therapeutics.

Scintigraphic tracking of mesenchymal stem cells after intravenous regional limb perfusion and subcutaneous administration in the standing horse.

OBJECTIVE: To assess distribution, uptake, and persistence of radiolabeled mesenchymal stem cells (MSC) using scintigraphy after intravenous regional limb perfusion (RLP) and subcutaneous injections in standing, sedated horses. STUDY DESIGN: Experimental study. ANIMALS: Horses (n = 12). METHODS: Six horses had RLP performed through the cephalic vein on 1 limb and subcutaneous injection in the metacarpal area in the opposite limb. The other 6 horses had RLP performed through the lateral palmar digital vein and subcutaneous injection in the coronary band. A pneumatic tourniquet was used for the RLP. MSC were labeled with technetium-HMPAO. Scintigraphic images were obtained at the time of injection, 1, 6, and 24 hours later. Results of RLP were compared with results from previous studies where similar injections were performed in anesthetized horses. RESULTS: Both RLP techniques led to greater variability, lower uptake, lower persistence, and poorer distribution when compared to results previously reported for horses under general anesthesia. The subcutaneous injections in the metacarpal area and coronary band resulted in MSC loss to the general circulation but no evidence of local migration. CONCLUSION: Due to partial or complete failure of the tourniquet, RLP performed in the standing horse as described is less efficient than performed under general anesthesia. Further work is needed to optimize the use of tourniquets to perform RLP for MSC administration in standing patients. The subcutaneous injections did not result in local migration in these normal horses.

Comparison of flow-mediated vasodilation in femoral and brachial arteries in healthy dogs.

OBJECTIVE: To compare flow-mediated vasodilation (FMD) measurements in brachial and femoral arteries of healthy dogs habituated to the assessment method, evaluate repeatability of these measurements, and investigate effects of blood pressure cuff inflation time on femoral artery FMD measurements. ANIMALS: 11 healthy adult Miniature Schnauzers. PROCEDURES: Arterial luminal diameter and blood flow velocity integral (FVI) were measured before and after cuff inflation of 5 minutes' (brachial and femoral arteries) or 3 minutes' duration (femoral artery) in separate experiments. A blood pressure cuff was inflated to > 200 mm Hg distal to each imaging site to increase local blood flow to induce reactive hyperemia. Changes in FVI after cuff deflation, FMD, and between-dog and within-dog coefficients of variation (CVs) were determined. RESULTS: After cuff inflation of 5 minutes' duration, greater changes were detected in median change in FVI and FMD of brachial arteries (174.0% and 8.0%, respectively), compared with values determined for femoral arteries (32.0% and 2.1%, respectively). Between-dog CV for brachial artery FMD was 34.0%, compared with 89.6% for femoral arteries, and within-dog CV was 32.5% for brachial arteries versus 51.6% for femoral arteries after cuff inflation of 5 minutes' duration. CONCLUSIONS AND CLINICAL RELEVANCE: In healthy Miniature Schnauzers, FMD was greater and more repeatable in brachial arteries than in femoral arteries. Reactive hyperemia was inconsistently induced in femoral arteries following 3- or 5-minute cuff inflation times. Brachial, but not femoral, artery FMD measurement is a potentially useful research technique for measurement of endothelial function in dogs.

Comparison of two tourniquets and determination of amikacin sulfate concentrations after metacarpophalangeal joint lavage performed simultaneously with intravenous regional limb perfusion in horses.

OBJECTIVE: To determine whether joint lavage performed simultaneously with IV regional limb perfusion (IVRLP) reduces the effectiveness of IVRLP and to compare 2 types of tourniquets used for this procedure in horses. ANIMALS: 11 adult horses. PROCEDURES: 2 groups of 6 horses were tested by use of a pneumatic or an Esmarch tourniquet (1 horse was tested twice [once in each group]). Standing IVRLP with amikacin (500 mg) was performed for 30 minutes. Simultaneously, the metacarpophalangeal joint was lavaged with 2 L of lactated Ringer's solution and the egress fluids were collected. Samples of the distal interphalangeal joint synovial fluid and blood from the digital and jugular veins were collected at set time intervals. Amikacin concentrations in all fluids were determined via fluorescence polarization immunoassay. RESULTS: Less amikacin was measured in the systemic circulation with the Esmarch tourniquet than with the pneumatic tourniquet. Amikacin concentrations in the synovial fluid from the distal interphalangeal joints of the Esmarch tourniquet group ranged from 45.1 to 1,968 µg/mL and in the pneumatic tourniquet group ranged from 1.7 to 92.3 µg/mL after 30 minutes of IVRLP. Total loss of amikacin in the egress fluids from the joint lavage ranged from < 1.36 to 7.72 mg for the Esmarch tourniquet group and from < 1.20 to 1.75 mg for the pneumatic tourniquet group. CONCLUSIONS AND CLINICAL RELEVANCE: On standing horses, IVRLP performed simultaneously with joint lavage resulted in negligible loss of amikacin in the egress lavage fluids. The Esmarch tourniquet was more effective in preventing loss of amikacin from the distal portion of the limb, easier to use, and less expensive than the pneumatic tourniquet.

Efficacy of three tourniquet types for intravenous antimicrobial regional limb perfusion in standing horses.

OBJECTIVE: To determine (1) if clinically useful concentrations of amikacin sulfate can be obtained in synovial fluid during regional limb perfusion (RLP) performed above the carpus in standing sedated horses and (2) to determine the efficacy of 3 tourniquet types (narrow rubber [NR], wide rubber [WR], pneumatic [PN]). ANIMALS: Horses (n=9). METHODS: Bilateral forelimb RLP with amikacin sulfate (2.5 g) were administered through the cephalic vein in standing sedated horses. Limbs were randomly assigned to the 3 tourniquet types (NR, WR, PN) applied above the carpus. Metacarpophalangeal synovial fluid was obtained 0.5 hour after perfusion. Amikacin concentration in the synovial fluid was detected using fluorescence polarization immunoassay. RESULTS: Mean synovial concentrations of amikacin in the PN (mean 236 µg/mL; range 23-913 µg/mL) and WR (mean 64.2 µg/mL; range 7-315 µg/mL) were significantly higher (P=.000 and .032, respectively) than the NR tourniquet (mean 2.1 µg/mL; range 0.9-3.3 µg/mL). CONCLUSIONS: The PN tourniquet resulted in the highest synovial fluid amikacin concentrations in all horses, although administration with PN and WR tourniquets achieved adequate amikacin concentrations. NR tourniquet is ineffective and should not be used for RLP above the carpus in the standing horse.

Development of intraosseous infusion of the distal phalanx to access the foot lamellar circulation in the standing, conscious horse.

Intraosseous (i.o.) infusion of the distal phalanx (IOIDP) as a delivery route targeting hoof lamellar tissue of standing, conscious horses was evaluated. Following sedation and regional nerve blockade in six Standardbred horses, a microdialysis (MD) probe was implanted into the hoof lamellar tissue of one forelimb. A purpose designed cannulated bone screw was introduced into the body of the distal phalanx, approximately 6 cm from the MD probe. Gentamicin solution (25 mg/mL) was infused at 20 microL/min through the bone screw for 2 h without the application of a tourniquet. MD and blood samples were collected at regular intervals and analysed for gentamicin concentrations. Gentamicin was present in lamellar tissue at much higher concentrations than peripheral serum. The mean concentration of gentamicin was 24.4, 20.5 and 4.4 microg/mL in extracellular fluid (ECF) and 0.28, 0.5 and 0.32 microg/mL in serum samples collected 60, 120 and 150 min after IOIDP was started, respectively. A clinically safe and efficacious i.o. drug delivery to the hoof lamellar tissue of standing, conscious horse was developed.

Comparison of two indirect techniques for local delivery of a high dose of an antimicrobial in the distal portion of forelimbs of horses.

OBJECTIVE: To compare isolated limb retrograde venous injection (ILRVI) and isolated limb infusion (ILI) for delivery of amikacin to the synovial fluid of the distal interphalangeal and metacarpophalangeal joints and to evaluate the efficacy of use of an Esmarch tourniquet in standing horses. ANIMALS: 6 healthy adult horses. PROCEDURES: Horses were randomly assigned in a crossover design. In ILRVI, the injection consisted of 1 g of amikacin diluted to a total volume of 60 mL administered during a 3-minute period. In ILI, the infusion consisted of 1 g of amikacin diluted to 40 mL administered during a 3-minute period followed by administration of boluses of diluent (82 mL total) to maintain vascular pressure. During ILI, the infusate and blood were circulated from the venous to the arterial circulation in 5-mL aliquots. Synovial fluid and serum samples were obtained to determine maximum amikacin concentrations and tourniquet leakage, respectively. RESULTS: Both techniques yielded synovial concentrations of amikacin > 10 times the minimum inhibitory concentration (MIC) for 90% of isolates (80 microg/mL) and > 10 times the MIC breakpoint (160 microg/mL) of amikacin-susceptible bacteria reported to cause septic arthritis in horses. These values were attained for both joints for both techniques. Esmarch tourniquets prevented detectable loss of amikacin to the systemic circulation for both techniques. CONCLUSIONS AND CLINICAL RELEVANCE: Both techniques reliably achieved synovial fluid concentrations of amikacin consistent with concentration-dependent killing for bacteria commonly encountered in horses with septic arthritis. Esmarch tourniquets were effective for both delivery techniques in standing horses.

Enhanced lipid peroxidation in tourniquet-release mice.

BACKGROUND: The pathogenesis of ischemia-reperfusion involves generation of reactive oxygen and resulting lipid peroxidation. However, investigation that ischemia-reperfusion following tourniquet release enhances lipid peroxidation is insufficient. METHODS: Tourniquet was applied to a unilateral hind limb of mice for 3h followed by 5-, 15-, 30- and 60-min release. To examine superoxide production immunohistochemically in ischemia-reperfusion muscles, a primary antibody directed to 4-hydroxy-nonenal (HNE) was used. Furthermore, we analyzed 7alpha- and 7beta-hydroperoxycholest-5-en-3beta-ol, 7alpha- and 7beta-hydroxycholesterol, and 7-ketocholesterol by HPLC in the gastrocnemius muscles, kidneys, liver, heart and lungs of mice after 1-h reperfusion. RESULTS: Increased HNE immunoreactivitiy was observed in the tourniquet-applied side of gastrocnemius muscles of hind limb particularly after 5-min reperfusion. All the oxysterols were significantly higher in the gastrocnemius muscles of the tourniquet-applied side than of the contralateral muscles. Oxysterols were elevated in the kidneys and the liver. Together with the presence of high blood urea nitrogen, these data indicate that the kidney is vulnerable to ischemia-reperfusion. CONCLUSIONS: The enhanced oxidative stress due to ischemia-reperfusion appears to increase HNE in muscle and oxysterols by peroxidation not only in the gastrocnemius muscles but also in the kidneys and liver.

Comparison of intraosseous and intravenous infusion of technetium Tc 99m pertechnate in the distal portion of forelimbs in standing horses by use of scintigraphic imaging.

OBJECTIVE: To describe and compare the distribution of technetium Tc 99m (99mTc) pertechnate following intraosseous or i.v. injection (with or without use of a tourniquet) in the distal portion of the forelimb in standing horses. ANIMALS: 4 horses. PROCEDURE: Each horse received 4 forelimb treatments in random sequence: intraosseous infusion with tourniquet application (IOT), intraosseous infusion without tourniquet application, i.v infusion with tourniquet application (IVT), and i.v. infusion without tourniquet application. Dynamic nuclear scintigraphic imaging of the third metacarpal bone, proximal and middle phalanges, and distal phalanx was performed from the start of each treatment until 1 hour after infusion was completed. Radionuclide activity was compared within and between treatment groups. RESULTS: Tourniquet application was necessary to maintain high levels of radionuclide activity in the distal portion of the forelimb after intraosseous or i.v. infusion with 99mTc pertechnate; IVT and IOT treatments resulted in similar radionuclide activity in the proximal and middle phalanges and distal phalanx. Of the 4 treatments, there was significantly higher radionuclide activity in the distal aspect of the third metacarpal bone after the IOT treatment. CONCLUSIONS AND CLINICAL RELEVANCE: By use of a tourniquet, radionuclide administration via the intraosseous or i.v. routes resulted in effective perfusion of the distal portion of the forelimb and similar distribution of the agent in the phalanges of horses. Further studies are required to ascertain whether these findings apply to delivery of therapeutic agents in infected tissues via IOT or IVT.

Tourniquet-induced hypertension in an ostrich.

Surgery was performed on a 3-year-old 110-kg male ostrich (Struthio camelus) to remove a sequestrum from the dorsal aspect of the left tarsometatarsal bone. A pneumatic tourniquet was positioned proximal to the surgical site and inflated to 600 mm of Hg. Systolic blood pressure increased 35% over 105 minutes while the tourniquet was inflated. Systolic blood pressure decreased 31.5% within 30 seconds after removal of the tourniquet pressure. Recovery from anesthesia and surgery was routine. The tourniquet-induced hypertension in this ostrich was similar to that reported for human beings and horses.

Effects of non-steroidal anti-inflammatory drugs on the hyperalgesia to noxious mechanical stimulation induced by the application of a tourniquet to a forelimb of sheep.

A tourniquet was used in conjunction with a mechanical threshold testing device to investigate the suitability of the technique for the investigation of analgesic drugs in sheep. The changes to the mechanical thresholds to noxious stimulation during and after the inflation of a pneumatic tourniquet on a limb were recorded, and the influence of pre-treatment with two non-steroidal anti-inflammatory drugs was studied. Fentanyl, an opioid agonist with known analgesic properties in sheep, was used as a positive control. The tourniquet significantly reduced the mechanical thresholds on the ipsi- but not the contralateral limb. Pretreatment with either flunixin meglumine or carprofen attenuated the development of mechanical hyperalgesia, and fentanyl initially caused a significant anti-nociceptive effect. The time to aversion was not significantly different between the treatments. These results suggest that hyperalgesia induced by a tourniquet may be a useful technique for the investigation of the anti-nociceptive effects of analgesic drugs in sheep.

Standing surgical procedures of the foot.

Several surgical conditions affecting the foot can be successfully managed with the horse standing. Many factors affect the clinician's choice of whether to perform surgery with the horse standing or anesthetized. Temperament or pregnancy of the horse and economics may influence the decision to perform surgery with the horse standing. This article discusses several foot conditions that can be treated successfully in the ambulatory horse.