Effects of thiopentone halothane-nitrous oxide anaesthesia compared to ketamine-xylazine anaesthesia on the DC recorded dog electroretinogram

Eleven ophthal-moscopically healthy dark adapted dogs were examined by DC ERG technique with single flash full field illumination starting with near b-wave threshold blue (tests 1-3) and white (tests 4-6) stimuli of different intensity and ending with 30 Hz photopic flicker smuli (test 7) after light adaptation. All animals were anaesthetized using 2 different anaesthetic methods: Anaesthesia I (A I): Induction with thiopentone sodium, continued with halothane and nitrous oxide in oxygen. Anaesthesia II (A II): Praemedication with xylazine hydrochloride followed by anaesthesia with ketamine hydrochloride. A minimum interval of 1 week was kept between all anaesthesias.The a- and b-wave amplitudes and latencies were determined. Statistical analysis of results indicated that the a- and b-waves were elicited by weaker intensities in A II. In Tests 3-6 the a-wave was highly significantly (P < 0.001), higher in amplitude in AII than in A I. Differencies in b-wave amplitudes were not statistically significant (except Test 1). The b-wave latencies were longer in AI in Test 2 (using low intensity blue light). The a-wave latencies were slightly shorter in AII in Test 6 (using high intensity white light).In additional experiments the selective action of the different agents (except N₂O) used in AI and AII was studied. Thiopentone alone given to 3 dogs seemed to depress the a-wave selectively.Halothane given separately to 3 dogs lowered both the a- and b-wave amplitudes. Ketamine given with a neuromuscular blocking agent to three dogs resulted in responses almost identical to those in AII.Xylazine with vecuronium given to 4 dogs resulted in responses with slighly depressed a- and b-waves in comparison to ketamine with vecuronium.The results indicate that when developing an animal model for the electrophysiologic study of human retinal dystropies, the actions of different anaesthetics upon the ERG components are of great importante.     

The effects of physostigmine on the electroretinogram in the beagle dog

The purpose of the study was to correlate electroretinogram (ERG) parameters with increasing levels of plasma, erythrocyte and ocular tissue cholinesterase inhibition using the beagle dog as a model for human neurovisual toxicity. The anticholinesterase compound physostigmine was administered at various steady-state intravenous infusion rates based on pharmacokinetic estimates of plasma and red blood cell cholinesterase inhibition. The most sensitive parameter was the b-wave amplitude of the rod response, which was significantly depressed compared to pretreatment at all levels of acute cholinesterase depression. The overall maximal ERG response demonstrated a trend of declining a-and b-wave amplitudes, which corresponded with the increased levels of cholinesterase depression, but these differences were not significant. The depression of the electroretinogram rod and cone amplitudes appeared to parallel plasma cholinesterase inhibition more closely than erythrocyte cholinesterase activity. Ocular tissue cholinesterase activity was significantly depressed in the retina (70%), cornea (60%) and dorsal rectus extraocular muscle (46%). Electroretinography may be a useful physiological tool for evaluating the ocular toxicity of certain chemicals or pharmaceuticals associated with cholinesterase biomarker activity.Abbreviations AChE acetylcholinesterase - Amp amplitude - BuChE butyrylcholinesterase - C _p plasma level - C _ss steady-state plasma concentration - D _L loading dose - e ^–kt the rate of elimination over time (t) - ERG electroretinogram - k elimination rate constant - Lat latency - MBW metabolic body weight - O₁–O₅ consecutive oscillatory potential wavelets - PreTx pretreatment - R rate of infusion - R _Inf rate of infusion - V _d volume of distribution     

Idiopathic dyserythropoiesis in a dog

Idiopathic dyserythropoiesis in a dog was characterized by chronic nonregenerative normocytic normochromic anemia, cellular marrow and abnormal morphology of erythroid precursors. Serum concentrations of Vitamin B(12), folate and iron were inconsistent with secondary causes of dyserythropoiesis. The disorder appeared to be distinct from myelodysplastic syndromes described previously.     

A comparison of ketamine-midazolam and ketamine-medetomidine combinations for induction of anaesthesia in rabbits.

OBJECTIVE: To compare ketamine-midazolam (KMZ) and ketamine-medetomidine (KMT) anaesthesia in rabbits using anaesthetic induction, maintenance and recovery data. STUDY DESIGN: Randomized, prospective, blinded clinical trial. ANIMALS: Fifty rabbits (25 male, 25 female) of different breeds undergoing ovariohysterectomy or castration. Rabbits were 12.7 +/- 9.8 months old with body mass 2.24 +/- 0.61 kg. STUDY DESIGN: Randomized, prospective, blinded clinical trial. METHODS: Ketamine (15 mg kg(-1)) and midazolam (3 mg kg(-1)) or medetomidine (0.25 mg kg(-1)) were administered by intramuscular (IM) injection. Ten minutes after IM injection, blind intubation of the trachea was attempted. The time taken, the number of attempts and a subjective score of the ease of intubation were recorded. Isoflurane (range 0-3.6%) in 100% oxygen was delivered via a Jackson Rees modification of an Ayre's T-piece non-rebreathing system. Carprofen (3 mg kg(-1)) and dextrose saline (5 mL kg(-1) hour(-1)) were administered intravenously (IV). During surgery heart rate (HR), respiratory rate (RR) and arterial oxygen saturation of haemoglobin (SpO(2)) were monitored. Times to extubation and first head lift were recorded. Group KMT received atipamezole (0.5 mg kg(-1)) IM 30 minutes after discontinuation of isoflurane. Activity was scored at 30, 60 and 120 minutes after volatile agent discontinuation. Mean time to loss of righting reflex (LRR), body mass, RR and vaporizer setting were compared using a two-tailed t-test. Median values for all other data were compared using a Mann-Whitney test. RESULTS: Mean time to LRR (+/-SD) was significantly shorter with KMT (1.64 +/- 0.55 minutes) compared with KMZ (2.28 +/- 0.66 minutes). Intubation was not possible in seven rabbits (three with KMT, four with KMZ) and three with KMT developed laryngospasm. Mean HR, SpO(2) and vaporizer settings were all significantly lower in group KMT. CONCLUSION AND CLINICAL RELEVANCE: KMT has a faster onset of action and a greater isoflurane-sparing effect when compared with KMZ. Rabbits with KMT were more prone to laryngospasm and had significantly lower HR.     

Synovial fluid eosinophilia: a case report in a dog and review of the literature

The first known report of synovial fluid eosinophilia in a dog is described here. The occurrence of eosinophils in joint fluid is rare. Sporadic cases have been recorded in humans and most can be related to immunemediated reactions, both parasitic and non- parasitic. The dog in this case report had 20-52% eosinophils in multiple joints, as well as hemarthrosis and marked mononuclear cell reactivity. An intense peripheral eosinophilia was demonstrated one week later. The associated lameness resolved with non-steroidal anti-inflammatory therapy. Lack of remarkable history or other clinical symptoms led to a diagnosis of idiopathic, eosinophilic, polyarthritis, likely immune-mediated.     

Prevalence of laryngeal paresis in dogs undergoing general anaesthesia

OBJECTIVE: To estimate the prevalence of laryngeal paresis within a selected population of dogs and identify some of the distinguishing characteristics of affected dogs. DESIGN: A prospective study involving laryngoscopic examination of 250 dogs. PROCEDURE: The laryngeal movements of 250 dogs undergoing general anaesthesia were observed. The severity of laryngeal paresis in these dogs was graded (0 = normal laryngeal movements, 4 = bilateral laryngeal paralysis). The following information was also recorded for each dog: age, sex, weight, breed, condition score, anaesthetic protocol, clinical suspicion of disease and observer. RESULTS: Twenty five percent of the dogs examined had some degree of laryngeal paresis. Affected dogs were significantly older than unaffected dogs (P < 0.001). There was a trend for the severity of laryngeal paresis to increase with age. There was no difference between the sexes. Dogs with laryngeal paresis were significantly heavier than normal animals (P < 0.02). Overweight animals had a significantly higher laryngeal grade than those with a normal condition score (P < 0.05). Labrador Retrievers and Rottweilers had a significantly higher risk of having laryngeal paresis (P < 0.05). Clinical suspicion was found to have high diagnostic value. An intra-class correlation coefficient for inter-rater reliability between the two observers was 0.95. CONCLUSIONS: Laryngeal paresis had a high prevalence in the animals surveyed and was strongly associated with age and breed. The results of this study are consistent with the concept of a progressive degenerative disease with a breed susceptibility. Clinical suspicion for the presence of the disease was a reliable indicator. The grading system used had a high degree of inter-observer agreement.     

Spontaneous resolution of hypothermia-induced atrial fibrillation in a dog

Objective: To report a case of spontaneous resolution of atrial fibrillation secondary to hypothermia in a dog without detectable heart disease. Case summary: An 8‐year‐old female spayed mixed breed dog presented with a history of prolonged exposure to below freezing environmental temperatures. The dog presented hypothermic (<32°C or <90°F) and minimally responsive to stimuli. The heart rate was 80 beats per minute (bpm) and irregular. Atrial fibrillation was diagnosed. The dog had pale mucous membranes, absent femoral pulses, and no obtainable blood pressure via indirect Doppler technique. Resuscitation fluids were administered and active external warming was instituted. Peripheral edema was observed during the rewarming phase and the irregular heart rate was noted to increase. The atrial fibrillation spontaneously resolved with no specific anti‐arrhythmic therapy. No underlying myocardial disease was found. The recovery of this dog was complete with a subsequent repeat of the echocardiogram and electrocardiogram (ECG) 8‐months later found to be within normal limits.     

Primary ocular osteosarcoma in a dog

An adult male Rottweiler presented to the veterinary medical teaching hospital at Purdue University with a 1-month history of hyphema. On physical examination conjunctivitis, episcleral hyperemia, corneal edema, hyphema, mild glaucoma and loss of vision were observed in the left eye. No other abnormalities were found. The left globe was surgically removed because of the high likelihood of neoplasia and it was fixed in 10% buffered formalin and submitted for pathology. A histologic diagnosis of primary osteosarcoma of the eye was made. Radiographic evaluation did not reveal any evidence of other tumors or pulmonary metastasis. This is the fourth canine case of primary intraocular osteosarcoma to be documented.     

Orbital neurofibrosarcoma in a dog

A young dog was presented with rapidly progressive, unilateral, exophthalmos. Ultrasound-guided fine-needle aspiration of the retrobulbar mass resulted in a diagnosis of fibrosarcoma. Magnetic resonance imagery revealed tumor invasion into the brain, and palliative therapy was elected. The dog was euthanized 4 weeks following diagnosis due to progressive neurological signs. The final diagnosis was neurofibrosarcoma involving the pons, brainstem, left orbit and left trigeminal nerve.     

Pathologic sideroblasts and siderocytes associated with chloramphenicol therapy in a dog

Siderotic granules were recognized in blood erythrocytes from a male Boxer dog with suppurative prostatitis, cystitis and pyelonephritis that was being given high dosage chloramphenicol therapy. Siderotic inclusions were recognized in the cytoplasm of 96% of the rubricytes and metarubricytes in a bone marrow aspirate. Siderotic inclusions were numerous and in some cases formed a ring around the nucleus. This perinuclear location suggested that pathologic mitochondrial iron accumulation had occurred, resulting in the formation of "ringed" sideroblasts. The occurrence of pathologic sideroblasts was confirmed by electron microscopy. Blood siderocytes and bone marrow sideroblasts disappeared after cessation of chloramphenicol therapy.     

Nasal infection with Scedosporium apiospermum in a dog

CASE HISTORY: A 2-year-old female Siberian Husky was presented with a 6-month history of sneezing and mucous discharge from the right nostril.

CLINICAL FINDINGS: Reduced airflow through the right nostril was evident. Radiographs showed subtle loss of detail of turbinates within the right nasal chamber. Rhinoscopy revealed swollen and erythematous turbinates and a white mass within the caudal aspect of the right nasal cavity. Histopathologically, there was a heavy mixed inflammatory infiltrate in the submus- cosa of the right turbinate, and the presence of fungal hyphae and spores in the white mass. A heavy growth of Scedosporium apiospermum was cultured from the mass.

DIAGNOSIS: Chronic rhinitis of the right nasal cavity and infection with S. apiospermum.

CLINICAL RELEVANCE: This is the first reported case of S. apiospermum isolated from the nasal cavity of a dog in New Zealand. Fungal culture is necessary to differentiate this fungus from Aspergillus spp.     

Hemolysis as a factor in clinical chemistry and hematology of the dog

Serum biochemical, hemostatic, and hematologic analytes were determined by four laboratories on dog serum or plasmas containing increasing amounts of hemolysate. From the results of testing, interferographs were prepared to aid in decision making and to enhance visualization of the effects of hemolysis on the determination of the analytes. Heniktsus consistently interfered with the analysis of creatinine phosphokinase, lactic dehydrogenase, aspartate aminotransferase, lipase, and albumin, all of which appeared to increase with increasing hemolysis. The results for the remainder of the biochemical, hemostatic, and hematologic analytes varied greatly among analyzers or methods, rarely in a predictable manner, indicating that each laboratory should evaluate the effects of hemolysis on each analyzer and for each method used, in order to make informed decisions on the use of hemolyzed but irreplaceable samples.     

Abdominal compartment syndrome in a dog with babesiosis

Objective: To describe a case of abdominal compartment syndrome in a dog with babesiosis. Case summary: A 9‐year‐old female Bull Terrier presented with complicated babesiosis. Additional findings including respiratory distress, abdominal distension, and a decrease in urine output associated with an elevated abdominal pressure (23.5–25 cmH₂O) led to a further diagnosis of abdominal compartment syndrome. This case report describes the clinical course of both conditions through resolution. New information provided: Abdominal compartment syndrome is not well described in the veterinary literature, but clinicians should be aware of this potential complication in critically ill patients. The pathophysiology and veterinary literature of abdominal compartment syndrome are reviewed.     

Foetal development of endocrine organs in dog

The canine adenohypophysis starts to be identifiable from 25 day of pregnancy. ACTH-immunoreactive cells migrate until day 38 after which the number of ACTH-producing cells increases but their distribution does not change. The STH- and LH-producing cells first appear on day 38 of pregnancy. The primordium of the adrenal glands appears as a slender structure on day 27 and forms the definitive cortical structure on day 35. The histological pattern of the foetal adrenal cortex differs from the post-natal structure in so far as the three cortical zones (definitive zone, transitional zone and foetal zone) extend from the outside towards the inside of gland. The mass of foetal and neonatal adrenals is more than 10 times larger than the adult adrenals relative to body weight. The cortisol concentration in the amnion is slightly lower than in the allantois but the foetal serum cortisol concentration is significantly higher than in the maternal and foetal fluid compartments. The thyroxine concentrations in the allantois and amnion fluids exceed the foetal serum concentrations except in the ninth week of pregnancy, but thyroxine levels in foetal fluids and serum are below the physiological levels of adult animals. The exocrine and endocrine functions of the pancreas develop and act in parallel. Pancreatic cells are first detected at 30 days when the branched structure is clearly detectable immunohistochemically, and at that time, insulin-positive β-cells and α-cells are visible as well. The foetal serum glucose concentration exceeds the healthy adult range, but the glucose concentration in the allantois and amnion fluid remains below the physiological blood glucose concentration of mature dogs. The insulin concentration in the allantois fluid greatly exceeds the foetal serum and amnion insulin concentrations.     

Primary extracranial nasopharyngeal meningioma in a dog

An 8‐year‐old Labrador Retriever was presented for inspiratory efforts with stertor. A rhinoscopy and a magnetic resonance imaging scan were performed and revealed a naso‐pharyngeal mass. The mass was identified in the nasopharynx without meningeal extension. This mass was both T1‐ and T2‐hyperintense, compared to normal brain parenchyma without significant postcontrast enhancement. The mass was surgically removed and the histologic diagnosis was a mesenchymal tumor. Immunohistochemistry with antibodies was conducted and consistent with an extracranial meningioma. To the authors’ knowledge, this is the first case report documenting a primary extracranial nasopharyngeal meningioma in a dog.     

Diagnosis of histoplasmosis in a dog by cytologic examination of CSF

A mixed inflammatory cell pleocytosis was identified in a cytocentrifuged sample of cerebrospinal fluid (CSF) and diagnosis of histoplasmosis was made on the basis of finding Histoplasma capsulatum organisms within macrophages. This dog had disseminated histoplasmosis with multiple organ involvement including the central nervous system (CNS) and eye.     

Suspected lily-of-the-valley (Convallaria majalis) toxicosis in a dog

Objective: To describe successful treatment of third-degree atrioventricular (AV) block using temporary noninvasive transthoracic pacing and placement of a permanent transvenous pacemaker in a case of suspected lily-of-the-valley ( Convallaria majalis ) intoxication in a dog.
Case summary: A 2-year-old neutered male Beagle weighing 17.8 kg was presented to the emergency service for treatment of bradycardia, vomiting, and lethargy. An electrocardiogram revealed third-degree AV block that was nonresponsive to atropine. Ten hours after admission, the dog became obtunded. Treatment initially consisted of temporary noninvasive transthoracic pacing and eventually placement of a permanent transvenous pacemaker. The initial history did not suggest that the dog had access to any known cardiotoxins. However, C. majalis , which contains cardiac glycosides, was identified within the dog's environment and the dog's serum did contain digoxin or an immunologically cross-reactive compound.
New or unique information provided: This is the first reported successful management of C. majalis toxicosis in a dog. Temporary noninvasive transthoracic pacing was used in the management of this case as a safe and effective bridge to permanent pacemaker implantation.