RESUMEN
OBJECTIVE: To compare the quality of surgical anaesthesia and cardiorespiratory effects of three intramuscular (IM) anaesthetic combinations in rabbits. STUDY DESIGN: Prospective randomized cross-over experimental study. ANIMALS: Nineteen adult female chinchilla mixed-bred rabbits weighing 3.9 +/- 0.8 kg. METHODS: Rabbits were given one of three IM anaesthetic combinations: 0.25 mg kg(-1) medetomidine and 35.0 mg kg(-1) ketamine (M-K), 0.20 mg kg(-1) medetomidine and 0.02 mg kg(-1) fentanyl and 1.0 mg kg(-1) midazolam (M-F-Mz) and 4.0 mg kg(-1) xylazine and 50 mg kg(-1) ketamine (X-K). The effects of anaesthesia on nociceptive reflexes, circulatory and respiratory function were recorded. Statistical analyses involved repeated measures anova with paired Student's t-test applied post hoc. P-values <0.05 were considered as significant. RESULTS: Reflex loss was most rapid and complete in M-K recipients, whereas animals receiving M-F-Mz showed the longest tolerance of endotracheal intubation (78.1 +/- 36.5 minutes). Loss of righting reflex was significantly most rapid (p < 0.05) in the X-K group (114.7 +/- 24.0 minutes). Surgical anaesthesia was achieved in 16 of 19 animals receiving M-K, in 14 animals receiving M-F-Mz, and in seven animals with X-K, but only for a short period (7.1 +/- 11.6 minutes). This was significantly (p < 0.001) shorter than with M-K (38.7 +/- 30.0 minutes) and M-F-Mz (31.6 +/- 26.6 minutes). Heart rates were greatest in X-K recipients; lowest HR were seen in animals receiving M-F-Mz. Mean arterial blood pressure was significantly higher (about 88 mmHg) during the first hour in the M-K group. During recovery, the greatest hypotension was encountered in the X-K group; minimum values were 53 +/- 12 mmHg. Six of 19 animals in the M-F-Mz group showed a short period of apnoea (30 seconds) immediately after endotracheal intubation. Respiratory frequency was significantly lower in this group (p < 0.001). Highest values for arterial carbon dioxide partial pressures (PaCO(2)) (6.90 +/- 0.87 kPa; 52.5 +/- 6.5 mmHg) occurred after induction of anaesthesia in group M-F-Mz animals. There was a marked decrease in PaO(2) in all three groups (the minimum value 5.28 +/- 0.65 kPa [39.7 +/- 4.9 mmHg] was observed with M-K immediately after injection). Arterial PO(2) was between 26.0 and 43.0 kPa (196 and 324 mmHg) in all groups during O(2) delivery and decreased - but not <7.98 kPa - on its withdrawal. Immediately after drug injection, pH(a) values fell in all groups, with lowest values after 30 minutes (7.23 +/- 0.03 with M-K, 7.28 +/- 0.05 with M-F-Mz, and 7.36 +/- 0.04 with X-K). The X-K animals showed significantly (p < 0.001) higher pH values than medetomidine recipients. During 1 hour of anaesthesia pH values in the medetomidine groups remained below those of the X-K group. CONCLUSIONS: Surgical anaesthesia was induced in most animals receiving medetomidine-based combinations. Arterial blood pressure was maintained at baseline values for about 1 hour after M-K. Transient apnoea occurred with M-F-Mz and mandates respiratory function monitoring. Oxygen enrichment of inspired gases is necessary with all three combinations. Endotracheal intubation is essential in rabbits receiving M-F-Mz. CLINICAL RELEVANCE: The quality of surgical anaesthesia was greatest with M-K. All combinations allowed recoveries of similar duration. It is theoretically possible to antagonize each component of the M-F-Mz combination.
Asunto(s)
Anestesia/veterinaria , Anestésicos Combinados/administración & dosificación , Animales de Laboratorio/fisiología , Conejos/fisiología , Animales , Estudios Cruzados , Femenino , Fentanilo/administración & dosificación , Hemodinámica , Inyecciones Intramusculares/veterinaria , Ketamina/administración & dosificación , Medetomidina/administración & dosificación , Estudios Prospectivos , Resultado del Tratamiento , Xilazina/administración & dosificaciónRESUMEN
BACKGROUND AND PURPOSE: We investigated the use of 2-poly-hydroxyethyl-methacrylate (2-P-HEMA) as an embolic agent in swine arteriovenous malformations (AVMs). METHODS: In seven mini swine, experimental AVMs were created surgically. The aim of treatment was complete embolization of the nidus compartment filled by the feeding artery, without brain embolization. Six animals received pure liquid 2-P-HEMA, and one, 50% 2-P-HEMA. For radiopacity, liquid 2-P-HEMA was mixed with tungsten powder. Six animals underwent angiographic follow-up within 5-8 mo (mean, 6.5 mo). Evaluation criteria were controllability, procedural reproducibility, and duration of the nidus occlusion. To detect complications, brain MR imaging and CT were performed. Histopathologic studies were performed to prove occlusion and assess histopathologic responses. RESULTS: 2-P-HEMA was easily injected through microcatheters, with a reproducible technique. Because of the radiopacity of the mixture, deep nidus penetration was controlled with fluoroscopy and confirmed with CT and histopathologic examination. In five AVMs embolized with pure 2-P-HEMA, feeder obliteration was long term. One animal had vasospasm during embolization, and complete obliteration of the main feeder was maintained for 3 mo, but partial recanalization developed 2 mo later. One animal receiving pure 2-P-HEMA had an infarction. In the animal embolized with 50% 2-P-HEMA, angiography and CT revealed embolic material in the circle of Willis; the animal died after embolization. No marked inflammatory reaction in the vessel wall or perivascular tissue was observed in the embolized AVMs. CONCLUSION: Experimental AVM embolization with pure 2-P-HEMA, made radiopaque with tungsten, is technically feasible in swine. Because of its properties, 2-P-HEMA has great potential as a therapeutic embolic agent.