Antimicrobial regional limb perfusion in horses

Plasma and Tissue Amikacin Concentrations Following Regional Limb Perfusion of Chickens (Gallus gallus domesticus)

Intravenous regional limb perfusion (IVRLP) has been used in the treatment of pododermatitis and distal limb infections, which are significant causes of morbidity in avian species. This intravenous drug administration technique is designed to achieve high drug tissue concentrations while minimizing systemic toxic effects. Amikacin is commonly used for IVRLP in veterinary medicine, but dosing guidelines have not been established for its use in birds. The current study aimed to determine the tissue concentration of amikacin after a single IVRLP administration in healthy, euhydrated leghorn hen chickens (Gallus gallus domesticus). Chickens received a single IVRLP dose of 10 mg/kg amikacin and were euthanatized posttreatment at 1 hour (n = 6), 12 hours (n = 6), and 24 hours (n = 6) to assess tissue and synovial fluid concentrations of amikacin in the injected leg. Mean tissue concentrations were highest 1 hour post-IVRLP (synovial fluid = 153.0 µg/mL, metatarsal pad tissue = 26.05 µg/mL) before declining at the 12- and 24-hour time points. This indicates that administration of amikacin via IVRLP can reach minimum inhibitory concentrations of common bacterial isolates in tissues after a single treatment with 10 mg/kg amikacin. Regional limb perfusion every 24 hours is recommended, although the minimum days of treatment may be case dependent and vary based on response to therapy.

Clinical Efficacy of a Single Intravenous Regional Limb Perfusion with Marbofloxacin versus Ceftiofur Sodium to Treat Acute Interdigital Phlegmon in Dairy Cows

The objective of the study was to compare the clinical efficacy of a single antimicrobial intravenous regional limb perfusion (IVRLP) with marbofloxacin versus ceftiofur sodium to treat naturally occurring interdigital phlegmon (IP) in dairy cows. The study had a randomized parallel-group design. Forty lactating Friesian cows clinically diagnosed with acute IP were enrolled, assigned to one of two treatment groups, and received a single IVRLP with the antimicrobial drug selected (M: 0.67 mg/kg of marbofloxacin; C: 500 mg/animal of ceftiofur sodium). Clinical data for the severity of lameness, digital swelling and local lesion appearance were assessed at diagnosis and at 5, 10 and 15 days post-IVRLP. Clinical resolution was defined as digital swelling disappearance, locomotion score reduction of at least 2/5 points, healed or healing local lesion and no relapse at 15 days after IVRLP. The total daily milk yield of each cow on the day before the clinical detection, on the day of diagnosis and on the day of the clinical follow-up post-IVRLP were registered. Lameness, digital swelling and local lesion severity were not significantly different between groups at any time-point. In both groups, on the fifteenth day after treatment, 17/20 (85%) cows showed a positive outcome, with no significant difference (p > 0.05). The daily milk production of all cows was adversely affected by the clinical onset of IP and gradually returned to a normal level after IVRLP in both groups. These preliminary results support the hypothesis that a single antimicrobial IVRLP procedure, irrespective of the antimicrobial selected (ceftiofur vs. marbofloxacin), has a high success rate and restores milk yield in cases of dairy cattle with acute IP lameness.

Standing Surgical Management of Splint Bone Fractures in 13 Horses: A Comparison to Management Under General Anaesthesia

OBJECTIVE

 The aim of this article was to describe the technique and outcomes of standing surgical management of splint bone fractures and to compare outcome variables and hospitalization cost to a group with similar fractures treated under general anaesthesia.

STUDY DESIGN

 It is a single-institution retrospective study. Surgical technique, surgical time, hospitalization cost and complications were retrieved from the medical records of horses treated surgically for splint bone fractures (2008-2020). Owner telephone follow-up provided data about athletic outcome, client satisfaction and cosmetic appearance.

RESULTS

 Forty-nine horses (13 standing, 36 under general anaesthesia) with 57 fractures (18 contaminated and 39 non-contaminated) were included. Seven fractures were in the proximal third (4 standing, 3 under general anaesthesia), 18 in the middle third (5 standing, 13 under general anaesthesia) and 30 were distal (4 standing, 26 under general anaesthesia). No significant difference between groups in surgical time was found (p= 0.8). Average total cost was 522 CAN$ lower for the standing group for non-contaminated fractures (p= 0.02). Three horses of the general anaesthesia group demonstrated postoperative colic signs and one case of the standing group was re-operated due to sequestration. Based on follow-up information (range: 3.8-151.2 months), no significant differences in cosmetic and athletic outcomes were found between groups.

CONCLUSION

 Surgical management of splint bone fractures in the standing horse is a valuable alternative for horses selected based on behaviour. When compared to general anaesthesia, standing management of splint bone fractures did not alter the surgical time or outcome variables and avoided general anaesthesia-associated risks.

Regional antibiotic perfusion through the lateral saphenous vein in two horses with septic calcaneal osteitis

In this case report, two horses with chronic refractory infections in the tuber calcanei were successfully managed via intravenous antibiotic regional limb perfusion through the lateral saphenous vein after failure of conventional treatment approaches, including surgery and intravenous regional limb perfusion using the cranial branch of the medial saphenous vein. Surgical delay in these cases may have allowed the development of chronic infection, which prevented the conventional regional perfusion from working effectively. The spatial difference of the vessels relative to the tuber calcanei possibly contributed to the treatment outcome in these horses. This report describes a novel approach for regional antimicrobial perfusion to the equine plantar hock region using the lateral saphenous vein.

Effect of perfusate volume on amikacin concentrations after saphenous intravenous regional limb perfusion in standing, sedated horses

OBJECTIVE

To determine the influence of perfusate volume on synovial fluid amikacin concentrations in the joints of the hind limb after standing saphenous intravenous regional limb perfusion (IVRLP).

STUDY DESIGN

Randomized crossover design.

ANIMALS

Six adult horses.

METHODS

Saphenous IVRLP was performed in 6 standing horses with 1 g of amikacin diluted with 0.9% NaCl to volumes of 10 ml, 60 ml, and 120 ml. Samples of synovial fluid from the tarsocrural, metatarsophalangeal, and hind limb distal interphalangeal joints were collected at 15 and 30 min after perfusate administration. Concentrations of 40 μg/ml and 160 μg/ml were considered therapeutic for susceptible and resistant pathogens, respectively.

RESULTS

No difference in synovial fluid amikacin concentrations was detected between volumes in any joint (P = .4). All synovial fluid amikacin concentrations were higher at 30 min compared to 15 min (P = .003). All median synovial fluid amikacin concentrations at 30 min were > 40 μg/ml using the 60 ml and 120 ml volumes. Synovial fluid amikacin concentrations >40 μg/ml were only reached in the hind limb distal interphalangeal joint when the 10 ml volume was used. All median synovial fluid amikacin concentrations observed were < 160 μg/ml.

CONCLUSIONS

Target concentrations for pathogens that were considered susceptible were consistently reached with perfusate volumes of 60 ml and 120 ml. However, median synovial fluid amikacin concentrations did not reach target levels for resistant pathogens.

CLINICAL SIGNIFICANCE

Perfusate volumes of 60 ml or 120 ml are recommended to treat infections due to susceptible pathogens in the joints of the distal hind limb. These results justify investigation of saphenous IVRLP with different perfusate volumes using higher doses of amikacin.

Adjunctive Use of Intravenous Antibiotic Regional Limb Perfusion in Three Cranes with Distal Limb Infections

Pododermatitis and wing lesions are commonly reported issues in captive crane species. Regional limb perfusion has been used as a treatment for distal limb infections in several avian species, as systemic antibiotic therapy is often prolonged and unrewarding. A black-necked crane (Grus nigricollis), Siberian crane (Leucogeranus leucogeranus), and wattled crane (Bugeranus carunculatus) were treated with amikacin (5-10 mg/kg IV infusion) regional limb perfusion for cellulitis and osteomyelitis of hind limb digits and alular osteomyelitis and septic arthritis of the carpus, respectively, with a range of 1-3 treatments per case. Clinical signs of infection resolved within 10-40 days following regional limb perfusion combined with oral or parental antibiotic therapy. No side effects were observed following regional limb perfusion. This is the first report of regional limb perfusion in cranes and the first report of intravenous regional limb perfusion in a wing of an avian species.

Synovial Concentration of Trimethoprim-Sulphadiazine Following Regional Limb Perfusion in Standing Horses

Simple Summary

Trimethoprim-sulphadiazine is a first line antimicrobial drug recommended for use in equine orthopedic infections such as deep wounds, ulcerative lymphangitis and septic arthritis. The pharmacokinetics of trimethoprim-sulphadiazine, when delivered through intravenous regional limb perfusion, has not been previously described. This study aimed at describing the pharmacokinetics and safety of the administration of trimethoprim-sulphadiazine through a single cephalic vein injection. Several horses in the study suffered from severe vasculitis, and the resulting synovial fluid concentration of trimethoprim-sulphadiazine over time was low. In light of these findings, the administration of trimethoprim-sulphadiazine to horses using regional limb perfusion via cephalic appears unwarranted.

Abstract

The aim of this study was to investigate the safety and pharmacokinetics of trimethoprim-sulphadiazine administered via intravenous regional limb perfusion (IVRLP) into the cephalic vein. According to the hypothesis, the drug could be administered without adverse effects and the synovial concentrations would remain above the minimum inhibitory concentration (MIC) for trimethoprim-sulphadiazine (0.5 and 9.5 µg/mL) for 24 h. Ten (n = 10) horses underwent cephalic vein IVRLP with an Esmarch tourniquet applied for 30 min. Four grams (4 g) of trimethoprim-sulphadiazine (TMP-SDZ) were diluted at 0.9% NaCl for a total volume of 100 mL. Synovial fluid and blood samples were obtained immediately before IVRLP and at 0.25, 0.5, 2, 6, 12 and 24 h after the initiation of IVRLP. Trimethoprim and sulphadiazine concentrations were determined using a method based on liquid chromatography/tandem mass spectrometry. The C_max (peak drug concentration) values were 36 ± 31.1 and 275.3 ± 214.4 µg/mL (TMP and SDZ). The respective t_max (time to reach C_max) values were 20 ± 7.8 and 26.4 ± 7.2 min. The initial synovial fluid concentrations were high but decreased quickly. No horse had synovial concentrations of trimethoprim-sulphadiazine above the MIC at 12 h. Severe vasculitis and pain shortly after IVRLP, lasting up to one week post-injection, occurred in five out of 10 horses. In conclusion, IVRLP with trimethoprim-sulphadiazine cannot be recommended due to the low concentrations of synovial fluid over time and the frequent severe adverse effects causing pain and discomfort in treated horses. Thus, in cases of septic synovitis with bacteria sensitive to trimethoprim-sulphadiazine, other routes of administration should be considered.

The Concentration of Metronidazole in the Distal Interphalangeal Joint following Intravenous Regional Limb Perfusion via the Cephalic Vein in Standing Horses

OBJECTIVE

 The aim of this study was to determine the concentration of metronidazole in the distal interphalangeal joint (DIPJ) of the thoracic limb after administering metronidazole to standing horses by intravenous regional limb perfusion (IVRLP).

METHODS

 Eleven healthy horses had a wide rubber tourniquet applied to the proximal aspect of the antebrachium for 0.5 hours and 500 mg of metronidazole diluted in physiologic saline solution to a total volume of 108 mL was administered by cephalic IVRLP. Synovial fluid samples were collected from the DIPJ before perfusion and at 0.25, 0.5, 2, 12 and 24 hours. Blood samples were obtained at the same time points for serum analysis. Concentrations of metronidazole were determined by liquid chromatography/tandem mass spectrometry.

RESULTS

 Four horses were excluded due to low synovial fluid concentrations and not completing the full tourniquet application time. The C _max in the synovial fluid was 327 ± 208 µg/mL, and the t _max was 26 ± 7 minutes. Only the concentrations of metronidazole at time points 0.25 and 0.5 hours were significantly different (p < 0.001) from synovial concentration before perfusion. The serum C _max was 1.78 ± 0.93 µg/mL, and the t _max was 76 ± 52min.

CONCLUSION

 Metronidazole administered by IVRLP reached high concentrations in the synovial fluid at 0.5 hours. However, the concentrations rapidly decreased below the minimum inhibitory concentration of potential target pathogens. Effectiveness of metronidazole administered by IVRLP as a sole therapy against anaerobic infections of synovial structures of the distal limb cannot be determined by a pharmacokinetic study. However, the present study serves as the basis for future carefully planned clinical trials.

Meropenem Administered via Intravenous Regional Limb Perfusion for Orthopedic Sepsis in Horses: A Clinical Retrospective Study

Septic synovitis is a critical orthopedic condition in horses. Early intervention is key, with antibiotic therapy typically initiated prior to culture and susceptibility reports becoming available. The pharmacokinetics of several antibiotics have been studied in horses for use in intravenous regional limb perfusion (IVRLP) for septic synovitis, including the carbapenem antibiotic, meropenem. For a variety of factors, some veterinary clinicians may select IVRLP meropenem as therapy for these cases. Meropenem is a vital antibiotic in human medicine, making veterinary use divisive. However, verifying the efficacy of meropenem contrasted to other IVRLP antibiotics is essential for appropriate antimicrobial stewardship. To investigate this, equine patient medical records at a single veterinary teaching hospital were examined. Cases treated with meropenem or gentamicin via IVRLP for septic synovitis were retrospectively analyzed for demographics, diagnostics, treatments, outcomes, and adverse effects. Twenty-three meropenem and 37 gentamicin treated horses were analyzed; demographic information was similar between groups. In the meropenem group, nine horses received meropenem only; the remainder received another antibiotic initially then changed to meropenem. Structures infected included joints (meropenem = 13, gentamicin = 17), tendon sheaths (meropenem = 5, gentamicin = 8) and navicular bursae (meropenem = 2, gentamicin = 6). Overall survival to discharge was 86% (52/60), with meropenem 91% (21/23) and gentamicin 84% (31/37), with no statistically significant differences noted between meropenem or gentamicin groups for overall survival to discharge or outcome after discharge. Twenty-four of 26 bacterial isolates obtained from culture were reported as sensitive to imipenem, a carbapenem antibiotic similar to meropenem. Reported susceptibility to other antibiotics such as ceftiofur (n = 22/26), ampicillin (n = 18/26), amikacin (n = 15/26), or gentamicin (n = 12/26) was also frequently present. In the population of this study, antimicrobial activity augmented with IVRLP using either meropenem or gentamicin both appear to be an effective treatment for septic synovial structures, therefore, less critical antimicrobials may be a viable and more judicious treatment option.

Time required to achieve maximum amikacin concentration in the synovial fluid of the tarsocrural joint following administration of the drug by intravenous regional limb perfusion in horses

OBJECTIVE

To determine the median time to maximum concentration (t_max) of amikacin in the synovial fluid of the tarsocrural joint following IV regional limb perfusion (IVRLP) of the drug in a saphenous vein of horses.

ANIMALS

7 healthy adult horses.

PROCEDURES

With each horse sedated and restrained in a standing position, a 10-cm-wide Esmarch tourniquet was applied to a randomly selected hind limb 10 cm proximal to the point of the tarsus. Amikacin sulfate (2 g diluted with saline [0.9% NaCl] solution to a volume of 60 mL) was instilled in the saphenous vein over 3 minutes with a peristaltic pump. Tarsocrural synovial fluid samples were collected at 5, 10, 15, 20, 25, and 30 minutes after completion of IVRLP. The tourniquet was removed after collection of the last sample. Amikacin concentration was quantified by a fluorescence polarization immunoassay. Median maximum amikacin concentration and t_max were determined.

RESULTS

1 horse was excluded from analysis because an insufficient volume of synovial fluid for evaluation was obtained at multiple times. The median maximum synovial fluid amikacin concentration was 450.5 μg/mL (range, 304.7 to 930.7 μg/mL), and median t_max was 25 minutes (range, 20 to 30 minutes). All horses had synovial fluid amikacin concentrations ≥ 160 μg/mL (therapeutic concentration for common equine pathogens) at 20 minutes after IVRLP.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that, in healthy horses, maintaining the tourniquet for 20 minutes after IVRLP of amikacin in a saphenous vein was sufficient to achieve therapeutic concentrations of amikacin in the tarsocrural joint.

Intravenous Regional Limb Perfusion in Standing and Recumbent Horses: A Comparative Radiographic Study

Although pharmacokinetic studies of drugs administered by intravenous regional limb perfusion (IRLP) to treat equine orthopedic infections suggest efficient drug distribution in the limbs, it remains unclear whether drug perfusion is affected by the position of the horse during the procedure. This study compared the perfusion of a radiopaque contrast into tissues of the extremities of horses maintained in standing and recumbent positions during an IRLP. Radiopaque contrast was administered through IRLP into the cephalic vein of 10 healthy adult horses under general anesthesia and right lateral recumbency (RG) or under sedation and standing (SG). The same animals were used in both groups, respecting a two-week washout period. Sequential radiographic images were performed immediately at the beginning of contrast administration (T0) and after 10, 20, 30, 40, and 50 minutes. Tourniquets were removed after 30 minutes. The time required for the contrast to reach the hooves was compared between groups. Contrast reached the hooves faster in SG (114 ± 15 seconds) compared with RG (236 ± 29 seconds) (P < 0.5). SG showed more uniform perfusion of the limb vessels, whereas RG showed more deposition of the contrast in the lateral digital vein, with smaller amounts reaching the hooves. From T10 onward, soft tissue radiopacity increased, albeit more markedly in standing than in recumbent animals, remaining until T50. Contrast radiography evidenced that IRLP performed in standing position leads to a quicker and more uniform perfusion of the vasculature and a more noticeable diffusion to the tissues than in recumbent horses.

Mesenchymal Stromal Cells as Potential Antimicrobial for Veterinary Use-A Comprehensive Review

The emergence of “superbugs” resistant to antimicrobial medications threatens populations both veterinary and human. The current crisis has come about from the widespread use of the limited number of antimicrobials available in the treatment of livestock, companion animal, and human patients. A different approach must be sought to find alternatives to or enhancements of present conventional antimicrobials. Mesenchymal stromal cells (MSC) have antimicrobial properties that may help solve this problem. In the first part of the review, we explore the various mechanisms at work across species that help explain how MSCs influence microbial survival. We then discuss the findings of recent equine, canine, and bovine studies examining MSC antimicrobial properties in which MSCs are found to have significant effects on a variety of bacterial species either alone or in combination with antibiotics. Finally, information on the influence that various antimicrobials may have on MSC function is reviewed. MSCs exert their effect directly through the secretion of various bioactive factors or indirectly through the recruitment and activation of host immune cells. MSCs may soon become a valuable tool for veterinarians treating antimicrobial resistant infections. However, a great deal of work remains for the development of optimal MSC production conditions and testing for efficacy on different indications and species.

In vitro Elution of Penicillin, Ampicillin, Tetracycline, Tulathromycin, and Florfenicol From Plaster of Paris Beads

The objectives of this study were to report a recipe for making antibiotic impregnated Plaster of Paris (AI-PoP) beads using penicillin, ampicillin, tetracycline, tulathromycin, and florfenicol and to determine the in vitro elution rates of those antibiotics in the beads. The AI-PoP beads were made using Plaster of Paris powder, antibiotic, and water, cured for 24 h, sterilized by ethylene oxide, and stored up to 5 months before testing. For each antibiotic, 20 beads were combined with bovine serum in sterile tubes and incubated at 37°C on a rocker. Serum was replaced at intervals over the 14 days study period, and antibiotic concentrations were determined by high pressure liquid chromatography with mass spectrometry. Separately, in a proof-of-concept study, the growth of E. coli and T. pyogenes in eluent from 10 beads for each antibiotic was quantified by flow cytometry. Antibiotic was detected in AI-PoP bead eluent for 14 days for all but the ampicillin beads, for which antibiotic was detected for 8 days. The concentration of antibiotic in eluent was greater than the minimum inhibitory concentration (MIC) of tested bacteria for the entire study period for penicillin, tetracycline, tulathromycin, and florfenicol. The concentration of ampicillin remained greater than the MIC of E. coli for 4 days and T. pyogenes for 6 days. The colony forming units (CFU)/ml of live E. coli and T. pyogenes was reduced over a 72-h period by 1-3 log10 CFU, with the exception of tetracycline, which reduced CFU/ml of T. pyogenes by Collapse

Key Words

• Plaster of Paris
• antibiotics
• cattle
• elution
• wound infection

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Affiliation(s)

Paul Merkatoris Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
Jennifer Schleining Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, United States
Adam Krull Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
David Borts Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, United States
Virginia Fajt Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX, United States

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Comparison of plasma and intra-articular gentamicin levels after intravenous administration in healthy horses

Septic arthritis is considered one of the most severe disorders that affect horses’ joints. Therapy is intended to eliminate the microorganisms that cause this infection. The intravenous administration of antibiotics is an easily performed technique, but there is no guarantee that the antibiotics will reach the joint milieu at high concentrations and remain elevated for a certain period of time. This study aimed to determine and compare the levels of gentamicin in the plasma and synovial fluid of healthy horses after intravenous administration for seven days. Five horses received 6.6 mg/kg intravenous gentamicin every 24 h for seven consecutive days. Blood and synovial fluid samples were collected from the right metacarpal-phalangeal joint before the start of the treatment (T0) and after 6 h (T6), 12 h (T12), and every 24 h during antibiotic therapy for seven days (D1 to D7). The levels of gentamicin in serum and synovial fluid were quantified by Enzyme-Linked Immunosorbent Assay (ELISA). The intravenous administration of 6.6 mg/kg of gentamicin, in horses, after a period of 24 h, promotes synovial fluid concentrations below the MIC of the drug, in spite of reaching high plasma concentrations of gentamicin, daily mean serum concentration which was 29-fold higher than the minimum inhibitory concentration (MIC) of the drug. The intravenous administration every 24 h during seven consecutive days did not cause systemic side effects, such as hepatic or renal injury.

Intravenous and intraosseous regional limb perfusion of ceftiofur sodium in an avian model

OBJECTIVE

To assess whether IV regional limb perfusion (IVRLP) and intraosseous regional limb perfusion (IORLP) of ceftiofur sodium resulted in clinically relevant drug concentrations in the synovial fluid of the tibiotarsal-tarsometatarsal joint of chickens (ie, an avian model) and to determine whether one of those techniques was superior to the other.

ANIMALS

12 healthy adult hens.

PROCEDURES

Birds were randomly assigned to receive ceftiofur sodium (2 mg/kg) by the IVRLP (n = 4), IORLP (4), or IM (control; 4) route once daily for 6 consecutive days. Blood and tibiotarsal-tarsometatarsal synovial fluid samples were collected 15 minutes after ceftiofur administration on predetermined days for quantification of ceftiofur concentration. Plasma and synovial fluid ceftiofur concentrations were compared among the 3 groups.

RESULTS

All 4 birds in the IVRLP group developed mild to moderate bruising around the injection site, but this bruising did not prohibit completion of the prescribed treatment regimen. No adverse effects were observed in any of the other birds. The mean plasma and synovial fluid ceftiofur concentrations exceeded the therapeutic threshold for most common bacterial pathogens (> 1.0 μg/mL) at all sample acquisition times for all 3 groups. The mean synovial fluid ceftiofur concentration for the IVRLP group was significantly greater than that for the IORLP and control groups at all sample acquisition times.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that IVRLP may be a safe and effective technique for antimicrobial administration to birds with joint infections, contaminated wounds, pododermatitis, and other musculoskeletal infections of the distal aspect of a limb.

Surgical intervention for vertebral osteomyelitis in a calf

OBJECTIVE

To report the surgical treatment and outcome of a non-ambulatory calf with cervical vertebral ostoeomyelitis.

STUDY DESIGN

Clinical report.

SAMPLE POPULATION

One 3.5-month-old female mixed-breed calf with tetraparesis of 3 months duration.

METHODS

After computed tomography-guided bone biopsy, a bacterial osteolytic lesion within the body of the fourth cervical vertebrae (C4) and resultant pathologic compression fracture clinically resulting in full tetraparesis was diagnosed in the calf. Culture results from the lesion within C4 confirmed a diagnosis of Trueperella pyogenes.

RESULTS

Poor response to medical management justified surgical debridment of the lesion in C4 and subsequent stabilization of the cervical vertebral column. A three-part procedure was performed including (1) debridement of the C4, (2) bilateral ventral vertebral stabilization from C3 to C5, and (3) placement of ampicillin-impregnated plaster of Paris beads within the body of C4. With postoperative physical rehabilitation, the calf regained full ambulatory function. At 1-month follow-up, the calf remained ambulatory with mild proprioceptive ataxia and no evidence of implant failure. At annual recheck, the calf had gained 208 kg and remained fully ambulatory with no residual neurologic deficits.

CONCLUSION

Surgical intervention and use of antibiotic-impregnated implants offered a viable alternative to long-term medical management of vertebral osteomyelitis in the calf reported here.

CLINICAL SIGNIFICANCE

This case identifies surgical intervention as a potential means for improving outcomes in a historically fatal condition of production animals.

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.

Borreliosis in Sport Horse Practice

Given the variable clinical signs attributed to Borrelia burgdorferi, including infectious arthritis, neurologic disease, and behavioral changes, B burgdorferi is an important differential for decreased performance in sport horses. The primary vectors (Ixodes tick species) are expanding their range and thus Borrelia species are located in a wider area, making exposure more likely. Due to regionally high seroprevalence and vague clinical signs, diagnosis of Lyme disease in the horse is believed overestimated. Antibiotics are first-line treatment of confirmed Lyme disease. A single positive serologic test, by itself, is not conformation of Lyme disease but is evidence of current or past infection.

Comparison of conventional radiography and computed tomography as aids in the diagnosis of osteomyelitis in 11 foals

BACKGROUND

Conventional radiography is currently the most common imaging modality used by veterinarians investigating foals with suspected osteomyelitis. Emerging evidence in adult horses and humans suggests computed tomography (CT) is a superior modality for evaluation of osseous changes in general. This study aimed to evaluate the potential benefits of CT versus conventional radiography in cases of osteomyelitis in foals.

METHODS

Cases of osteomyelitis in foals under 6 months of age admitted over a 6-year period at a single referral hospital that had both CT and conventional radiography images were retrieved. Case details and measurements of the largest area of bone lysis identified in two planes (lateromedial/sagittal and dorsopalmar/dorsal) were evaluated by three veterinarians with a range of experience.

RESULTS

A significant difference regarding lesion size was seen on the lateromedial (LM) radiographic projections compared with the equivalent sagittal plane CT image. The LM radiographic evaluation resulted in a 37% underestimation of the area of the lesion. Additionally, use of the LM radiographic projections were 2.5-fold more variable in the measurement area compared with CT. In general, regardless of projection, CT produced more information regarding lesion area and, in some cases, detected osseous changes that were not evident on the radiographs.

CLINICAL RELEVANCE

LM radiographic projections are less reliable and commonly result in an under-appreciation of lesion size and extent. CT detected lesions that were difficult or impossible to identify on radiographs and may allow improved treatment planning.

Magnetic resonance imaging following regional limb perfusion of gadolinium contrast medium in 26 horses

BACKGROUND

Systemic administration of gadolinium contrast medium is common in small animals to increase lesion conspicuity and determine vascularisation of lesions identified with magnetic resonance imaging (MRI); however, the large volume required for systemic administration limits its use in horses.

OBJECTIVES

The purpose of this study was to assess the feasibility of administering a low dose of contrast medium via venous regional limb perfusion.

STUDY DESIGN

Prospective clinical study.

METHODS

Distal limbs of 26 horses (one limb per horse) were imaged with MRI before and after administration of 5 mL of gadopentetate dimeglumine (Magnevist^® ) diluted with 5 mL of physiological saline via a palmar/plantar digital vein with a tourniquet in place at the level of the mid aspect of the third metacarpal/metatarsal bone. Commonly assessed structures of the equine distal limb were examined for normal and abnormal contrast enhancement.

RESULTS

Twenty-five of 26 horses had adequate contrast enhancement of their distal limb. The lack of adequate contrast enhancement in one limb was likely associated with failure of the tourniquet. No adverse reactions were identified in any horse. One hundred thirty-two lesions were detected, of which, 69 contrast enhanced. Twelve lesions were detected exclusively following contrast enhancement.

MAIN LIMITATIONS

Case numbers and lesion variability yielded insufficient data to perform statistical analyses. Histopathology was not performed on sound horses to determine if the imaged structures were normal.

CONCLUSIONS

Regional limb perfusion is a feasible method to administer gadolinium contrast material to the equine distal limb for MRI. The enhancement pattern of the equine distal limb in sound horses is described. Contrast enhanced MRI of the distal equine limb helps to further characterise lesions identified with precontrast images, including adhesions and deep digital flexor tendinopathy. Contrast enhanced MRI also aids in identification of additional lesions, such as neovascularisation.

Pharmacokinetics of marbofloxacin administered via intravenous regional limb perfusion in dairy cows: evaluation of two different tourniquets

Objectives

This study evaluated synovial and systemic plasma pharmacokinetic variables of marbofloxacin after a single intravenous regional limb perfusion (IVRLP) performed using two different tourniquets in clinically healthy, standing, non-sedated dairy cows. The authors hypothesised that the type of tourniquet used for IVRLP would influence the synovial fluid concentration of marbofloxacin in the perfused distal limb.

Design

The study had a randomised parallel-group design.

Methods

Ten adult dairy cows were included. Unilateral hindlimb IVRLP through the dorsal common digital III vein was performed in two groups of five cows (group 1: wide rubber tourniquet; group 2: manual pneumatic tourniquet) using 0.67 mg/kg of marbofloxacin. The tourniquet was applied proximal to the tarsus and maintained for 30 minutes. Samples of jugular blood and synovial fluid from the tibiotarsal joints of the perfused limb were obtained before and at intervals after IVRLP. All samples were analysed for drug concentrations using liquid chromatography tandem mass spectrometry. Pharmacokinetic parameters were determined to establish the influence of tourniquet types. Differences were considered significant at P≤0.05.

Results

No adverse effects from the procedure or marbofloxacin were observed in any animal. Significant differences in synovial concentrations and pharmacokinetic parameters were measured. The mean ± sd areas under the concentration versus time curve from time 0 to 24 hours were 178.98±58.08 µg hour/ml for group 2 and 21.11±9.93 µg hour/ml for group 1. The mean ± sd maximum marbofloxacin concentrations were 75.50±10.19 µg/ml for group 2 and 6.35±1.47 µg/ml for group 1.

Conclusions

Performing IVRLP using the dorsal common digital III vein and a manual pneumatic tourniquet set at 300 mmHg above the tarsus in standing cows resulted in significantly higher marbofloxacin concentrations in the tibiotarsal joint compared with those with the wide rubber tourniquet.

Trial registration

Local ethical committee (number 41/2012/CEISA).

SUCCESSFUL TREATMENT OF DIGITAL OSTEITIS BY INTRAVENOUS REGIONAL PERFUSION OF CEFTIOFUR IN AN AFRICAN ELEPHANT (LOXODONTA AFRICANA)

A 41-yr-old African elephant ( Loxodonta africana ) presented with a swollen third digit of the left forelimb and a 2-cm hole in the pad. Corrective trimming, topical treatments, and an oral antibiotic resulted in apparent resolution; however, it reoccurred after 4 mo. Radiographs suggested bone lysis in the third phalanx, with the primary differential diagnosis being septic osteitis. Flushing with metronidazole solution and intravenous regional perfusion (IVRP) of the foot were commenced. A tourniquet was applied just above the carpus, an interdigital vein was identified by ultrasound, and into this vein 2 g (20 ml) of ceftiofur sodium solution, followed by 60 ml of heparinized saline, was administered. The foot was kept raised for 25 min and then the tourniquet was removed. IVRP was repeated every other day for 70 treatments over 6 mo. Healing occurred, which was confirmed radiographically. IVRP offers an excellent treatment modality in a well-trained elephant.

Isolated limb perfusion electrochemotherapy for the treatment of an advanced squamous cell carcinoma of the hoof in a mare

A twenty-year-old female saddle horse was referred for evaluation of a seven month, non-healing erosive lesion of the right hind hoof with proliferation and bleeding of the underlying soft tissues. This lesion had been twice surgically treated as a canker but rapidly recurred. Histological examination of the second excision revealed a well-differentiated squamous cell carcinoma. At presentation, the horse was mildly depressed, lame and partially non-weight-bearing on the right hind leg, which exhibited a 10 x 10 cm erosive and proliferative lesion remodeling the hoof. After completing staging procedures, the lesion was approached with surgery and intraoperative electrochemotherapy (ECT) administration of bleomycin in isolated limb perfusion. A second session of surgery and ECT was performed one month later, followed by three additional monthly sessions of ECT. During periodic recheck, the mare showed continuous improvement. One year after presentation, the mare was in complete remission and her gait markedly improved. ECT was well-tolerated and resulted in improved local control of a tumor in a challenging anatomical district.

INTRAVENOUS REGIONAL ANTIBIOTIC PERFUSION THERAPY AS AN ADJUNCTIVE TREATMENT FOR DIGITAL LESIONS IN SEABIRDS

Foot infections are a common problem among seabirds in wildlife rehabilitation. Pododermatitis and digital infections are often challenging to treat because of the presence of suboptimal substrates, abnormal weight-bearing due to injuries, and suboptimal nutritional or health status. Seabirds represent the majority of animals requiring rehabilitation after oil spills, and foot problems are a common reason for euthanasia among these birds. Antibiotic intravenous regional perfusion therapy is frequently used in humans and other species to treat infections of the distal extremities, but it has not been evaluated in seabirds. During the 2015 Refugio oil spill response, four birds with foot lesions (pododermatitis, osteomyelitis, or both) were treated with ampicillin/sulbactam administered intravenously to the affected limb(s) in addition to systemic antibiotics and anti-inflammatories. Three of the birds, all brown pelicans ( Pelecanus occidentalis ) recovered rapidly and were released. Two of these birds had acute pododermatitis and were treated once with intravenous regional perfusion. They were released approximately 3 wk after the perfusion therapy. The third pelican had osteomyelitis of a digit. It was treated twice with intravenous regional perfusion and was released about 1 mo after the initial perfusion therapy. The fourth bird, a Pacific loon ( Gavia pacifica ), was treated once with perfusion therapy but did not respond to treatment and was euthanatized. No serious adverse effects were observed. This technique should be explored further in avian species.

Therapeutic Use of Regional Limb Perfusion in a Chicken

A 2-year-old, 3.8-kg male Rhode Island red rooster was examined for lameness and progressive swelling of the right foot of several month's duration. Radiographs of the right foot demonstrated soft tissue swelling and a smoothly marginated periosteal reaction evident of inflammation affecting the bones. Results of a complete blood count showed a moderate leukocytosis and an elevated total protein concentration. Systemic antibiotic and anti-inflammatory therapy was started, but the bird had not improved at recheck examination. After intravenous catheterization of the medial metatarsal vein and placing a tourniquet at the femoral-tibiotarsal joint of the right leg, regional limb perfusion with amikacin and flunixin meglumine was performed. Dimensions of both feet were measured with digital calipers, and surface temperatures of the feet were measured with an infrared thermometer. The rooster had improved activity level with decrease in lameness and measurable decrease in swelling of the right foot. Regional limb perfusion with intravenous antibiotics and nonsteroidal anti-inflammatory drugs is a viable treatment modality in avian species for suspected distal limb infection and cellulitis. This technique has potential valuable implications for a variety of avian species. Fluid support should be provided if using nephrotoxic drugs.

Evaluation of the pharmacokinetics of imipenem following regional limb perfusion using the saphenous and the cephalic veins in standing horses

This prospective experimental study goal was to determine the pharmacokinetics of imipenem after intravenous regional limb perfusion (IV-RLP) in standing horses. Nine horses participated in the study; that was approved by the University Animal Care and Use Committee. One thoracic limb or one pelvic limb of each horse was randomly selected. After the veins were catheterized, an Esmarch bandage tourniquet was applied and the catheter was injected with a solution containing 500mg of imipenem. Synovial fluid samples were collected from the fetlock joint and blood samples were collected from the jugular vein. All samples were analyzed for imipenem concentration using liquid chromatography mass spectrometry. Cmax of imipenem in the fetlock joint using the cephalic and the saphenous vein was 87 and 60μg⁄mL, respectively. The results indicate that by performing IV-RLP using the cephalic/saphenous, one can achieve imipenem concentrations in the fetlock joint that are well above the MIC of most susceptible pathogens including resistant bacteria such as Methicillin Resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. Thus, with selective; judicious use, RLP with imipenem can markedly increase treatment efficacy of severe distal limb infections in horses.

Effects of regional limb perfusion volume on concentrations of amikacin sulfate in synovial and interstitial fluid samples from anesthetized horses

OBJECTIVE To evaluate the effect of volume of IV regional limb perfusion (IVRLP) on amikacin concentrations in synovial and interstitial fluid of horses. ANIMALS 8 healthy adult horses. PROCEDURES Each forelimb was randomly assigned to receive IVRLP with 4 mL of amikacin sulfate solution (250 mg/mL) plus 56 mL (total volume, 60 mL) or 6 mL (total volume, 10 mL) of lactated Ringer solution. Horses were anesthetized, and baseline synovial and interstitial fluid samples were collected. A tourniquet was placed, and the assigned treatment was administered via the lateral palmar digital vein. Venous blood pressure in the distal portion of the limb was recorded. Additional synovial fluid samples were collected 30 minutes (just before tourniquet removal) and 24 hours after IVRLP began; additional interstitial fluid samples were collected 6 and 24 hours after IVRLP began. RESULTS 30 minutes after IVRLP began, mean amikacin concentration in synovial fluid was significantly greater for the large-volume (459 μg/mL) versus small-volume (70 μg/mL) treatment. Six hours after IVRLP, mean concentration in interstitial fluid was greater for the large-volume (723 μg/mL) versus small-volume (21 μg/mL) treatment. Peak venous blood pressure after large-volume IVRLP was significantly higher than after small-volume IVRLP, with no difference between treatments in time required for pressure to return to baseline. CONCLUSIONS AND CLINICAL RELEVANCE Study findings suggested that large-volume IVRLP would deliver more amikacin to metacarpophalangeal joints of horses than would small-volume IVRLP, without a clinically relevant effect on local venous blood pressure, potentially increasing treatment efficacy.

Quantitative assessment of two methods of tiludronate administration for the treatment of lameness caused by navicular syndrome in horses

OBJECTIVE

To determine effects of 2 tiludronate administration protocols on measures of lameness in horses with navicular syndrome (NS).

ANIMALS

12 horses with bilateral forelimb NS.

PROCEDURES

Horses were randomly assigned to receive tiludronate (1 mg/kg), diluted in 5 L of isotonic electrolyte solution and delivered through a jugular vein catheter (systemic treatment group; n = 6), or tiludronate (0.1 mg/kg), diluted with saline (0.9% NaCl) solution to a total volume of 35 mL and delivered into the lateral digital vein of each forelimb with an IV regional limb perfusion (IVRLP) technique (IVRLP group; 6). Mean peak vertical ground reaction force (pVGRF) measured with a stationary force plate and subjective lameness scores (SLSs) were recorded before (day -1) and at predetermined time points after tiludronate administration on day 0. Mean pVGRFs (standardized as percentage body weight of force) and mean SLSs for the most lame forelimb and for both forelimbs of horses in each group were compared with day -1 values to determine treatment effect.

RESULTS

Mean pVGRF for both forelimbs and for the most lame forelimbs of systemically treated horses were significantly increased on days 120 and 200, compared with day -1 results. No significant difference in mean pVGRF was observed for IVRLP-treated horses. The SLSs were not improved at any time point following systemic treatment and were improved only on day 120 following IVRLP.

CONCLUSIONS AND CLINICAL RELEVANCE

Tiludronate (1 mg/kg, IV) as a single systemic treatment appeared to be beneficial for horses with NS, but no horses were judged as sound during the study period. Additional research on IVRLP with tiludronate is needed before this method can be recommended.

The Effect of Perfusate Volume on Amikacin Concentration in the Metacarpophalangeal Joint Following Cephalic Regional Limb Perfusion in Standing Horses

OBJECTIVE

To determine the influence of 3 perfusate volumes on amikacin concentration in the metacarpophalangeal joint following cephalic regional limb perfusion (RLP) in standing horses.

ANIMALS

Seven healthy horses.

METHODS

Three perfusate volumes (100, 60, and 30 mL), containing 2 grams of amikacin, were tested during intravenous RLP at the cephalic vein, placing the tourniquet at mid antebrachium, in standing sedated horses. Synovial fluid was collected from the metacarpophalangeal joint before perfusion and at 30 and 120 minutes after perfusion. Serum samples were taken from the jugular vein at the same time points. Samples were analyzed for amikacin concentrations and a repeated measures ANOVA, followed by least squares difference pairwise comparisons to identify differences in amikacin concentration across perfusate volumes. Differences were considered significant at P<.05.

RESULTS

The mean amikacin concentration in synovial fluid at 30 minutes after perfusion was significantly higher following perfusate volume of 100 mL (579 μg/mL), compared to volumes of 60 mL (227 μg/mL) or 30 mL (282 μg/mL) (P<.05). When a threshold of 160 μg/mL was used, more horses reached the synovial therapeutic threshold following perfusate volume of 100 mL (100%), than horses receiving 60 mL (43%) and 30 mL (57%) at 30 minutes after injection.

CONCLUSION

The use of 100 mL volume for RLP at the cephalic vein in standing horses resulted in higher concentration of amikacin in the synovial fluid and is recommended for use in clinical cases.

Magnetic resonance imaging assisted management in five cases of suspected quittor

OBJECTIVES

Assessment of the usefulness of magnetic resonance imaging (MRI) in treatment planning in suspected cases of quittor in the horse.

METHODS

Five horses with chronic discharging tracts at the level of the foot underwent MRI for treatment planning.

RESULTS

The MRI examination revealed variable involvement of soft tissue and osseous structures of the foot in addition to abnormalities of the ungular cartilages in all cases. In two cases, follow-up MRI examination was performed. Four of five horses had a successful outcome, with three of these undergoing only one surgical procedure and one being managed medically.

CLINICAL SIGNIFICANCE

We believe that the use of preoperative MRI facilitated accurate determination of the structures involved in cases of quittor, guiding the management, surgical approach and postoperative therapy.

Evaluation of intravenous regional perfusion with amphotericin B and dimethylsulfoxide to treat horses for pythiosis of a limb

BACKGROUND

Treatment for horses with pythiosis of a limb is challenging. This study aims to evaluate the effects of administering amphotericin B in a 10 % solution of dimethylsulfoxide by intravenous regional limb perfusion (IRLP) to treat horses for cutaneous pythiosis of a limb.

RESULTS

All 15 of the horses treated had complete resolutions of their lesion between 6 to 9 weeks after a single IRLP treatment. No complications were observed at the site of venipuncture for IRLP. Before initiation of treatment, there was anemia and marked leucocytosis which resolved following treatment. Serum biochemistry showed no significant changes.

CONCLUSIONS

IRLP administration of amphotericin B in a 10 % DMSO solution was easily performed, relatively inexpensive and an effective treatment for treating horses for pythiosis of a limb and resolved the infection with no complications.