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CASE DESCRIPTION A 20-year-old female south-central black rhinoceros (Diceros bicornis minor) was evaluated because of an acute onset of CNS deficits. CLINICAL FINDINGS The rhinoceros had no history of illness. Clinical signs included acute lethargy, ataxia, and decreased appetite. Hematologic abnormalities included leukocytosis with neutrophilia and a profound left shift. Results of serum biochemical analysis revealed hypophosphatemia but no other abnormalities. Results of a quantitative PCR assay for West Nile virus and an assay for anti-Neosporum caninum antibodies in serum were negative; the patient was seropositive for multiple Leptospira serovars. TREATMENT AND OUTCOME Antimicrobials and anti-inflammatory agents were administered, but the condition of the rhinoceros worsened overnight; despite treatment with additional anti-inflammatory and antimicrobial agents, IV fluids, and thiamine, it became obtunded and died of respiratory arrest ≤ 24 hours later. Necropsy revealed severe, diffuse, suppurative, and histiocytic meningo-encephalomyelitis involving the cerebrum, cerebellum, and spinal cord. Amebic trophozoites were observed on histologic examination of affected tissue. Infection with Naegleria fowleri was confirmed by results of immuno-histochemical analysis and a multiplex real-time PCR assay. CLINICAL RELEVANCE Findings suggested that south-central black rhinoceros are susceptible to the free-living ameba N fowleri. Ameba-induced meningoencephalomyelitis should be considered as a differential diagnosis for rhinoceros that have an acute onset of neurologic signs. Diagnosis of N fowleri infection in an animal has a profound public health impact because of potential human exposure from the environment and the high fatality rate in people with N fowleri infection.
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Amoeba , Encefalomielitis/veterinaria , Naegleria fowleri , Animales , Femenino , Humanos , PerisodáctilosRESUMEN
BACKGROUND: In order to advance beyond basic statistical limb salvage to improved functional or quality limb salvage, a better understanding of the ischemic threshold of the limb is required. To date, models of extremity ischemia and reperfusion involve small animals and few include survival with physiologic measures of nerve and muscle recovery. In addition, the effect of hemorrhagic shock on the ischemic threshold of the extremity is unknown. This study characterized the effect of class III hemorrhagic shock on the ischemic threshold of the extremity in a large-animal model of neuromuscular recovery. METHODS: Yorkshire/Landrace-cross swine (weight, 70-90 kg) were randomized to iliac artery repair either immediately or at 1, 3, or 6 hours after vessel loop occlusion and arteriotomy. A fifth group underwent excision of the arterial segment without repair to represent ligation. Class III shock was created by removing 35% of total blood volume using a variable rate model. Animals were monitored for 14 days to serially collect markers of functional recovery. RESULTS: Animals with ≤1 hour ischemia (control) had clinically normal limb function by the end of the 2-week observation period, with minimal muscle and nerve changes on histology. Separate analysis of contralateral, nonexperimental limbs revealed normal histology and function. After 3 hours of ischemia, functional recovery was impaired, with moderate-to-severe degeneration of nerve and muscle noted on histology. Animals undergoing 6 hours of ischemia or ligation had minimal electromyelography response and severe systemic inflammation, which correlated with severe muscle and nerve degeneration. Concurrent class III hemorrhagic shock was associated with a decrement in neuromuscular recovery across all groups but was greatest in groups undergoing ≥3 hours of extremity ischemia (P < .01). CONCLUSIONS: This study demonstrates the feasibility of combined hemorrhagic shock and extremity ischemia-reperfusion in a large-animal survival model. The presence of hemorrhagic shock compounds the effect of extremity ischemia, reducing the ischemic threshold of the limb to <3 hours. Strategies to improve functional salvage after extremity vascular injury in the setting of shock should include attempts at restoration of flow ≤60 minutes.
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Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/inervación , Enfermedades Musculares/etiología , Degeneración Nerviosa/etiología , Daño por Reperfusión/complicaciones , Choque Hemorrágico/complicaciones , Lesiones del Sistema Vascular/complicaciones , Animales , Biomarcadores/sangre , Modelos Animales de Enfermedad , Electromiografía , Femenino , Marcha , Miembro Posterior , Músculo Esquelético/patología , Enfermedades Musculares/sangre , Enfermedades Musculares/patología , Enfermedades Musculares/fisiopatología , Degeneración Nerviosa/sangre , Degeneración Nerviosa/patología , Degeneración Nerviosa/fisiopatología , Conducción Nerviosa , Examen Neurológico , Postura , Recuperación de la Función , Flujo Sanguíneo Regional , Daño por Reperfusión/sangre , Daño por Reperfusión/patología , Daño por Reperfusión/fisiopatología , Choque Hemorrágico/sangre , Choque Hemorrágico/patología , Choque Hemorrágico/fisiopatología , Sus scrofa , Factores de Tiempo , Lesiones del Sistema Vascular/sangre , Lesiones del Sistema Vascular/patología , Lesiones del Sistema Vascular/fisiopatologíaRESUMEN
BACKGROUND: Despite advances in revascularization following extremity vascular injury, the relationship between time to restoration of flow and functional limb salvage is unknown. The objectives of this study are to describe a large animal survival model of hind limb ischemia/reperfusion and define neuromuscular recovery following increasing ischemic periods. METHODS: Sus scrofa swine (N = 38; weight, 87 ± 6.2 kg) were randomized to iliac artery occlusion for 0 (Control), 1 (1HR), 3 (3HR), or 6 (6HR) hours, followed by vessel repair and 14 days of recovery. Additionally, one group underwent iliac artery division with no restoration of flow (Ligation), and one group underwent iliac artery exposure only without intervention (Sham). A composite physiologic measure of recovery (PMR) was generated to assess group differences over 14 days of survival. PMR included limb function (Tarlov score) and electrophysiologic measures (compound muscle action potential amplitude, sensory nerve action potential amplitude, and nerve conduction velocity). Using the PMR and extrapolating the point at which recovery following ligation crosses the slope connecting recovery after 3 and 6 hours of ischemia, an estimate of the ischemic threshold for the hind limb is made. These results were correlated with peroneus muscle and peroneal nerve histology. RESULTS: Baseline physiologic characteristics were similar between groups. Neuromuscular recovery in groups with early restoration of flow (Control, 1HR, 3HR) was similar and nearly complete (92%, 98%, and 88%, respectively; P > .45). While recovery was diminished in both 6HR and Ligation, Ligation, rather than repair, exhibited greater recovery (68% vs 53%; P < .05). These relationships correlated with the pathologic grade of degeneration, necrosis, and fibrosis (P < .05). The PMR model predicts minimal and similar persistent loss of function in groups undergoing early surgical restoration of flow (Control 8%, 1HR 1%, 3HR 12%; P > .45). In contrast, the Ligation group exhibited the greatest degree of injury early in the reperfusion period, followed by more complete recovery and at a faster rate than 6HR. Extrapolating from the PMR the point at which Ligation (68% recovery) crosses the slope connecting 3 hours (84% recovery) and 6 hours (53% recovery) of ischemia estimates the ischemic threshold to be 4.7 hours. Restoration of flow at ischemic intervals exceeding this are associated with less physiologic recovery than ligation. CONCLUSION: In this model, surgical and therapeutic adjuncts to restore extremity perfusion early (1-3 hours) after extremity vascular injury are most likely to provide outcomes benefit compared with delayed restoration of flow or ligation. Furthermore, the ischemic threshold of the extremity after which neuromuscular recovery is significantly diminished is less than 5 hours. Additional studies are necessary to determine the effect of other factors such as shock or therapeutic measures on this ischemic threshold.
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Miembro Posterior/irrigación sanguínea , Arteria Ilíaca/lesiones , Isquemia/fisiopatología , Modelos Animales , Potenciales de Acción , Animales , Miembro Posterior/inervación , Arteria Ilíaca/fisiopatología , Arteria Ilíaca/cirugía , Ligadura , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/inervación , Conducción Nerviosa , Nervio Peroneo/fisiopatología , Recuperación de la Función/fisiología , Reperfusión , Sus scrofa , Degeneración WallerianaRESUMEN
BACKGROUND: Extremity ischemia/reperfusion has been studied mostly in small-animal models with limited characterization of neuromuscular or functional outcome. The objective of this experiment was to report a large-animal survival model of extremity ischemia/reperfusion using circulating, electromyographic (EMG), gate, and histologic measures of injury and limb recovery. METHODS: Sus scrofa swine (n = 6; mean, 83 kg) were randomized to iliac artery occlusion for 0 (control), 1 (1 HR), 3 (3 HR), or 6 (6 HR) hours. Restoration of flow after a standard large-vessel reconstructive technique (thrombectomy, heparin irrigation, and patch angioplasty) was performed in each of the control, 1HR, 3HR, and 6HR animals, whereas one animal had iliac artery segment excision with no restoration (NR) of axial flow. One animal had operative exposure but no intervention on the iliac artery (sham). Animals were recovered and closely monitored for 2 weeks. Indicators of ischemia/reperfusion and functional recovery, including circulating markers, EMG measures (complex motor action potential), and Tarlov gate scoring (0-4; 0, insensate/paralyzed to 4, normal posture and no gait abnormality) were measured at 24 hours and 72 hours and 7 days and 14 days. Muscle (peroneus) and nerve (peroneal) were collected during necropsy at 14 days to assess gross and histologic changes. Duplex ultrasound was performed serially during the recovery period to confirm patency of vascular reconstruction. RESULTS: There were no deaths or failures of vascular reconstruction. Control had a Tarlov score of 4 and normal EMG measures at each point during recovery (same as sham). Tarlov scores at 1, 3, and 14 days recovery in each of the animals were as follows: 1HR: 3, 3, and 4; 3HR: 1, 2, and 4; 6HR: 1, 2, and 3; and NR: 1, 2, and 4. Complex motor action potential as a percentage of baseline at 1, 2, and 14 days recovery was as follows: 1HR: 56%, 55%, and 84%; 3HR: 9%, 8%, and 57%; 6HR: 5%, 5%, and 16%; and NR: 22%, 28%, and 33%. Muscle and nerve histology was the same in sham, control, and 1HR animals. Moderate degeneration and necrosis was observed in peroneus muscle of the 3HR animals. The peroneal nerve in 3HR demonstrated minimal Wallerian degeneration. Severe necrosis was present, as was minimal regeneration, and peroneal nerve demonstrated moderate Wallerian degeneration in 6HR. CONCLUSION: This study reports a new large-animal survival model of extremity ischemia/reperfusion using circulating, functional, and histologic markers of neuromuscular recovery. Findings provide insight into an extremity ischemic threshold after which functional neuromuscular recovery is lost. Additional study is necessary to define this threshold and factors that may move it to a more or less favorable position in the setting of extremity injury.
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Extremidad Inferior/irrigación sanguínea , Extremidad Inferior/inervación , Nervio Peroneo/fisiopatología , Neuropatías Peroneas/etiología , Daño por Reperfusión/mortalidad , Animales , Modelos Animales de Enfermedad , Electromiografía , Potenciales Evocados Motores , Femenino , Estudios de Seguimiento , Contracción Muscular/fisiología , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/inervación , Músculo Esquelético/fisiopatología , Nervio Peroneo/patología , Neuropatías Peroneas/diagnóstico , Neuropatías Peroneas/fisiopatología , Proyectos Piloto , Recuperación de la Función , Daño por Reperfusión/complicaciones , Daño por Reperfusión/fisiopatología , Sus scrofa , Ultrasonografía Doppler Dúplex , Vasoconstricción/fisiologíaRESUMEN
An in vitro efficacy study using newly developed artificial wound eschar (AWE) substrate was conducted for assessing enzyme dose response. The AWE substrate is prepared by the enzymatic conversion of fibrinogen to fibrin in the presence of collagen, fibrin, and elastin to form an insoluble planar matrix. AWE substrate was placed on Franz Diffusion Cells for continuously monitoring the debridement progress. A parallel in vivo study was performed using pig thermal-burn wounds. Papain at concentrations of 200, 400, 800, and 1,600 U/mg was used as the model debriding enzyme for both studies. The data from the first 5 hours of the in vitro testing showed that debriding activity increased as the enzyme concentration increased. The histological results of the in vivo biopsy samples showed that enzyme doses above 800 and 1,600 U/mg successfully achieved debridement on day 8, while lower treatment groups still contained eschar tissue. Using the histological measurement results (wound depth score) a dose response that correlated to the in vitro assessment was found. Granulation tissue maturity and reepithelialization displayed correlation with the enzyme dose. Results indicate that AWE substrate can be used to predict debridement efficacy in vitro when correlation to the in vivo assessment is achieved.
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Quemaduras/tratamiento farmacológico , Desbridamiento/métodos , Papaína/administración & dosificación , Cicatrización de Heridas/efectos de los fármacos , Administración Tópica , Animales , Modelos Animales de Enfermedad , Emulsiones/administración & dosificación , Femenino , Técnicas In Vitro , Sus scrofa , Resultado del TratamientoRESUMEN
PURPOSE: We determined the maximal renal tolerance of warm ischemia using renal cortical interstitial metabolic changes to identify a potential real-time marker of irreparable renal function. MATERIALS AND METHODS: Using a single kidney model 3 groups of 5 pigs each underwent 120, 150 and 180 minutes of warm ischemia, respectively. Microdialysis samples were collected before, during and after ischemia. Renal function assessments consisting of serum creatinine and GFR measurements were performed before ischemia and on post-ischemia days 1, 5, 9, 14 and 28. Kidneys exposed and not exposed to ischemia were collected for histological study. RESULTS: Interstitial glucose and pyruvate concentrations decreased, while lactate concentrations increased to stable levels during ischemia. Glutamate spiked at 30 minutes of ischemia and subsequently tapered, while glycerol increased throughout warm ischemia time. At post-ischemia day 28 renal function returned to pre-ischemia baseline levels in the group with 120 minutes of ischemia but did not recover to baseline in the 150 and 180-minute ischemic groups. Functional data correlated with histological findings. The 120-minute maximal renal tolerance of warm ischemia correlated with a mean +/- SD glycerol concentration of 167 +/- 24 micromol/l. CONCLUSIONS: Interstitial glycerol is a real-time, renal unit specific, minimally invasive marker of renal function deterioration. Exposure of porcine kidneys to ischemic insults resulting in renal cortical interstitial glycerol concentrations higher than 167 micromol/l is associated with irreparable functional damage in this model.
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Biomarcadores/metabolismo , Glicerol/metabolismo , Riñón/patología , Daño por Reperfusión/patología , Isquemia Tibia/efectos adversos , Análisis de Varianza , Animales , Glucemia/análisis , Modelos Animales de Enfermedad , Femenino , Tasa de Filtración Glomerular , Pruebas de Función Renal , Lactatos/análisis , Nefrectomía/métodos , Probabilidad , Piruvatos/metabolismo , Distribución Aleatoria , Sensibilidad y Especificidad , Porcinos , Isquemia Tibia/métodosRESUMEN
BACKGROUND CONTEXT: Bisphosphonates affect bone remodeling and increase bone mass through the inhibition of osteoclasts. Their effect on osteoblasts, and the balance between osteoblastic and osteoclastic activity on bone turnover and healing, is not completely understood. Specifically, the effect of bisphosphonates on spinal fusion has yet to be determined. With the increasing use of bisphosphonates in the elderly population, this effect needs to be delineated. PURPOSE: To evaluate the effect of alendronate sodium after an intertransverse process spinal fusion in a rabbit model. STUDY DESIGN/SETTING: Randomized double-blinded in vivo study of the effect of alendronate sodium in a spinal fusion model. METHODS: Fifty New Zealand white rabbits underwent a posterolateral L5-L6 intertransverse process arthrodesis with autogenous iliac crest bone graft. The rabbits were then randomly divided into two groups. Group I received 3 cc of saline placebo per oral gavage, and Group II received 200 micrograms (approximately 0.05 mg/kg/day) of alendronate sodium dissolved in 3 cc of saline per day for 8 weeks. Upon completion, the rabbits were sacrificed and the lumbar spines harvested, radiographed and graded for motion across the fusion site with manual palpation. Two independent pathologists then prepared and sectioned each left and right fusion mass. Three random x10 fields were examined and graded for both the cephalad and caudad ends of each section (516 fields). Fusion quality was graded using an established histological scoring scale (score 0 to 7 based on fibrous and bone content of the fusion mass). RESULTS: Two rabbits died on the day of operation, and 48 rabbits survived the operation. Five additional rabbits died within the first 2 postoperative weeks. Thus, 43 rabbits (21 in Group I, 22 in Group II) completed the 8-week course of treatment. Grading each side separately, 26 of 42 fusion masses (62%) in Group I and 24 of 44 fusion masses (55%) in Group II had radiographic evidence of fusion (p=.76). With gross palpation, 11 of 21 motion segments (52%) in Group I versus 13 of 22 motion segments (59%) in Group II were determined to have a solid fusion (p=.76). Histologically, Group I had a higher median score (6.0; range, 0 to 7 vs. 1.0; range, 0 to 7; p<.0001) and a higher fusion rate (76% vs. 45%; p=.004) than Group II. CONCLUSIONS: Alendronate sodium appears to inhibit or delay bone fusion in a rabbit model. Presumably, this occurs as a result of uncoupling the balanced osteoclastic and osteoblastic activity inherent to bone healing. These findings suggest that a discontinuance of alendronate sodium postoperatively during the acute fusion period may be warranted.