Effects of posture and accumulated airway secretions on tracheal mucociliary transport in the horse

Tracheal mucociliary clearance was determined in horses by measuring the rostrad transport of the radiopharmaceutical ^99mtechnetium-sulphur colloid following deposition on the tracheal epithelium by intratracheal injection. The effects of head position (head elevated to normal standing position vs head lowered) and of accumulated purulent secretions on tracheal mucociliary clearance were evaluated for the first time in the horse. In normal horses tracheal mucociliary clearance was greatly accelerated by lowering the head so that the cranial trachea was lower than the caudal trachea. Horses confined with their heads elevated for 24 hours developed an accumulation of purulent airway secretions (and associated increased numbers of bacteria) in the lower respiratory tract and showed a decrease in tracheal mucociliary clearance when compared with their previously measured rate when the lower airway contained only normal secretions. These findings have implications for management practices where horses are prevented from lowering their heads, such as transportation and cross-tying, which may therefore contribute to lower respiratory tract disease in horses.     

Pharmacokinetic studies of theophylline in cats

The pharmacokinetics of theophylline were determined in adult cats and the data were fitted to a two-compartment model. Single intravenous and multiple oral doses of aminophylline were used. The mean plasma theophylline half-life ( t _1/2) following the single intravenous dose was 7.8 h and the mean apparent specific volume of distribution ( V '_d(area)) was 0.46 l/kg. The absorption half-life ( t _{1/2 ab} ) was 0.5 h and the bioavailability was 96% following oral administration. There was excellent agreement between the predicted and observed plasma theophylline concentrations following multiple oral doses.     

Effects of saffan on cardiopulmonary function in healthy cats.

The effects of saffan on cardiopulmonary function were evaluated in eight healthy adult cats. Measured values were cardiac output by thermodilution, heart rate by electrocardiogram, arterial blood gases, respiratory rate and systolic, diastolic and mean arterial blood pressures by arterial catheterization. Calculated values included cardiac index, stroke volume and systemic vascular resistance. Statistical analysis employed paired t-tests comparing pre saffan anesthetic induction and post saffan anesthetic parameters over a 120 minute time sequence. Thirty min after saffan induction, significant depression in cardiac output was evident while stroke volume was significantly depressed at 45 and 60 min, systolic blood pressure at 15 min and respiratory rate at 5, 10 and 15 min. No significant changes occurred in cardiac index, heart rate, arterial blood gases, diastolic and mean arterial blood pressure or systemic vascular resistance. It was concluded that saffan causes significant depression of cardiopulmonary function in normal adult cats.     

Effects of increasing infusion rates of dopamine, dobutamine, epinephrine, and phenylephrine in healthy anesthetized cats

OBJECTIVE: To determine the cardiopulmonary effects of increasing doses of dopamine, dobutamine, epinephrine, and phenylephrine and measure plasma concentrations of norepinephrine, epinephrine, and dopamine in cats anesthetized with isoflurane. ANIMALS: 6 healthy adult cats. PROCEDURES: Each cat was anesthetized with isoflurane (1.5 X minimum alveolar concentration) on 4 occasions. Cardiopulmonary measurements were obtained after a 30-minute stabilization period; 20 minutes after the start of each infusion dose; and 30, 60, and 90 minutes after the infusion was discontinued. Cats received 5 progressively increasing infusions of epinephrine or phenylephrine (0.125, 0.25, 0.5, 1, and 2 microg/kg/min) or dobutamine or dopamine (2.5, 5, 10, 15, and 20 microg/kg/min). The order of treatment was randomly allocated. Results-All 4 treatments increased oxygen delivery. Heart rate (HR) increased during administration of all drugs except phenylephrine, and mean arterial pressure increased during administration of all drugs except dobutamine. A progressive metabolic acidosis was detected, but whole-blood lactate concentration only increased during administration of epinephrine and dobutamine. Systemic vascular resistance index increased during administration of phenylephrine, decreased during administration of dobutamine, and remained unchanged during administration of dopamine and epinephrine. A positive inotropic effect was detected with all treatments. CONCLUSIONS AND CLINICAL RELEVANCE: During anesthesia in cats, administration of dopamine, dobutamine, and epinephrine may be useful for increasing cardiac output, with dopamine having the most useful effects. Administration of phenylephrine increased cardiac and systemic vascular resistance indexes with minimal effect on HR and may be useful for increasing mean arterial pressure without increasing HR.     

Effects of a standardized anesthetic protocol on hematologic variables in healthy cats

This study evaluated the effects of an anesthetic protocol using intravenous ketamine and midazolam, and intramuscular buprenorphine on hematologic variables in cats. Twelve healthy adult cats had blood collected for a complete blood count before and after the induction of anesthesia. There were significant decreases in red blood cell counts, hemoglobin concentrations and hematocrits after the induction of anesthesia. On average, red blood cell counts and hematocrits decreased by 25%, and hemoglobin concentrations decreased by 24%. Based on hematocrit, 3/12 samples (25%) taken while the cats were anesthetized would have been interpreted as belonging to anemic patients while none of the cats would have been considered anemic before anesthesia. This study suggests that a complete blood count performed on blood taken under anesthesia with this anesthetic protocol should be interpreted cautiously in order to not make a false diagnosis of anemia.     

Use of scintigraphy for the determination of mucociliary clearance rates in normal, sedated, diseased and exercised horses.

Mucociliary clearance rates from the trachea were determined in normal, sedated, diseased and exercised horses from scintigraphs obtained after an injection of technetium-99m sulphide colloid into the tracheal lumen. The group mean tracheal clearance rate of eight clinically normal horses during 42 trials was 2.06 +/- 0.38 cm/min. Significant between horse differences were found (p less than 0.05). When six and seven of these horses were given xylazine and detomidine hydrochloride, respectively, mean group tracheal clearance rates dropped significantly (p less than 0.05). The decreases from each normal horse's mean tracheal clearance rate ranged from 18 to 54%. There did not appear to be a difference between the tracheal clearance rates (TCRs) of the normal horses and those with chronic respiratory disease. Postexercise evaluations were not significantly different from the pre-exercise TCRs in three clinically normal horses and three horses with chronic obstructive pulmonary disease (p greater than 0.05). This minimally invasive scintigraphic technique for determining TCRs has proved to be useful and reliable.     

Intrathoracic tracheal avulsion in three cats

The surgical repair of complete intrathoracic tracheal avulsion in three cats is described. The initial presenting signs included dyspnoea, exercise intolerance and exertional cyanosis. Diagnosis was based upon the clinical signs, survey radiography and tracheal endoscopy. The ruptures were repaired via a right lateral thoracotomy made at the third or fourth intercostal interspace. Abnormal trachea was resected and a standard tracheal anastomosis was performed. Surgical results were considered excellent in all cases.     

Pharmacokinetics of an extended-release theophylline product in cats

OBJECTIVE: To evaluate the pharmacokinetics of a brand of extended-release theophylline tablets and capsules in healthy cats. DESIGN: Randomized 3-way crossover study. ANIMALS: 6 healthy cats. PROCEDURES: A single dose of aminophylline (10 mg/kg [4.5 mg/lb], IV), a 100-mg extended-release theophylline tablet, or a 125-mg extended-release theophylline capsule was administered to all cats. Plasma samples were collected via preplaced central catheters throughout a 36-hour period. Plasma samples were frozen until analyzed by use of a fluorescence polarization monoclonal immunoassay. RESULTS: All cats tolerated drug administration and plasma collection with no adverse effects. Peak concentrations were reached for both orally administered products between 8 and 12 hours after administration. Bioavailability was excellent. Plasma concentrations were within the human therapeutic concentration of 5 to 20 microg/mL. CONCLUSIONS AND CLINICAL RELEVANCE: Daily administration of the brand of theophylline tablets and capsules used in this study at 15 mg/kg (6.8 mg/lb) and 19 mg/kg (8.6 mg/lb), respectively, maintained plasma concentrations within the desired therapeutic range in healthy cats.     

Intraluminal tracheal stenting for treatment of tracheal narrowing in three cats

OBJECTIVE: To describe the use of intraluminal tracheal stenting in 3 cats with either benign or malignant tracheal obstruction. STUDY DESIGN: Retrospective clinical study. ANIMALS: Three client-owned cats. METHODS: Medical records were reviewed and information regarding signalment, clinical signs, physical examination findings, diagnostic tests performed, treatment, outcome and follow-up were retrieved. Intraluminal tracheal stent placement was performed as previously described in the literature. RESULTS: Three cats received intraluminal tracheal stents for the treatment of tracheal obstruction due to 3 different underlying causes: stricture secondary to traumatic endotracheal intubation, stricture secondary to a previous tracheotomy, and neoplasia. Self-expanding metallic stents of varying sizes were placed, and all cats recovered uneventfully from the procedures. The cat with tracheal neoplasia was euthanized because of pulmonary metastatic disease 6 weeks post-stent placement. The two cats with tracheal obstructions secondary to benign strictures are currently 39 months and 32 weeks post-stent placement, respectively. No complications were noted during the post-stent period in any of the 3 cats. CONCLUSIONS: Intraluminal tracheal stenting was easily, safely, and rapidly performed without complications and resulted in immediate improvement in clinical signs in all three cases. None of the cats in this study developed significant stent-associated complications during the study period. CLINICAL RELEVANCE: Intraluminal tracheal stenting has the potential to be a viable option for the treatment of tracheal obstruction in cats and perhaps for similar disease processes in other veterinary patients.     

Effects of lithium carbonate administration to healthy cats.

Lithium carbonate administration to healthy cats was evaluated in 2 controlled studies (a dose-response study and a bone marrow evaluation study) to determine the effectiveness of lithium as a bone marrow stimulant. Lithium carbonate was administrated at dosage ranging from 300 to 1,050 mg/m2 of body surface/d. Complete blood count, serum lithium concentration determination, serum biochemical analysis, urinalysis, and bone marrow aspiration and biopsy were periodically performed. Serum lithium concentration greater than 2 mEq/L was associated with significant decrease in numbers of circulating segmented neutrophils (less than 1,200 cells/microliter; P less than 0.01) and lymphocytes (less than 1,300 cells/microliter; P less than 0.0001), as well as significant (P less than 0.05) decrease in urine specific gravity. Bone marrow evaluation revealed apparent maturation arrest of the neutrophil cell line. Coincident with the changes in laboratory values, the lithium-treated cats became ill. Changes in behavior and vocalization were seen, followed by anorexia, vomiting, and diarrhea. In later stages of intoxication, cats became hyperexcitable and manifested coarse muscular tremors. It was concluded that lithium carbonate does not have potential value as a bone marrow stimulant and is toxic to cats at serum concentration greater than 2 mEq/L.     

Pulmonary particle deposition and airway mucociliary clearance in cold-exposed calves.

Effect of cold-induced changes in respiratory pattern on pulmonary particle deposition was investigated in 10 male Holstein calves between the ages of 1 and 3 months. Deposition of intranasally instilled fluorescence-enhanced Pasteurella haemolytica was significantly higher (P less than 0.05) for cold-exposed calves and appears to be caused by the cold-induced respiratory pattern change. Deposition was greater in apical and mediastinal lung lobes, but the reason for this preferential deposition is uncertain. Nasal mucus velocity was measured in 4 nonanesthetized calves at ambient temperature of 2 to 4 C and 16 to 18 C, using tantalum-paraffin oil droplets and serial radiography. Nasal mucus velocity was 24% lower during cold exposure. In addition, the effect of mucosal temperature on tracheal mucus velocity was determined in excised tracheas from 7 calves. A direct relationship existed between mucosal temperature and tracheal mucus velocity within the mucosal temperature range studied (35.0 to 39.5 C). Tracheal air temperature measurements in calves at ambient temperatures of -10.4 C (n = 4) and 18.5 C (n = 5) indicated that conditioning of inspired air is not complete at the tracheal level during extreme cold exposure. Therefore, cold air may directly influence tracheal mucociliary clearance. It is speculated that cold exposure increases pulmonary deposition of pathogens, while simultaneously decreasing mucociliary clearance of the upper airways, thus predisposing cold-exposed calves to respiratory tract infection.     

Effects of 0.005% latanoprost solution on intraocular pressure in healthy dogs and cats

OBJECTIVE: To evaluate effects of daily topical ocular administration of latanoprost solution on intraocular pressure (IOP) in healthy cats and dogs. ANIMALS: 9 domestic shorthair cats and 14 dogs. PROCEDURE: Latanoprost solution (0.005%) was administered topically to 1 eye (treated) and vehicle to the other eye (control) of all animals once daily in the morning for 8 days. Intraocular pressure was measured twice daily for the 5 days preceding treatment, and IOP, pupillary diameter, conjunctival hyperemia, and blepharospasm were measured 0, 1, 6, and 12 hours after the first 4 treatments and 0 and 12 hours after the final 4 treatments. Measurements continued twice a day for 5 days after treatment was discontinued. Aqueous flare was measured once daily during and for 5 days after the treatment period. RESULTS: Intraocular pressure and pupillary diameter were significantly decreased in the treated eye of dogs, compared with the control eye. Mild conjunctival hyperemia was also detected, but severity did not differ significantly between eyes. Blepharospasm and aqueous flare were not detected in either eye. Intraocular pressure in cats was not significantly affected by treatment with latanoprost. However, pupillary diameter was significantly decreased in the treated eye, compared with the control eye. Conjunctival hyperemia, aqueous flare, and blepharospasm were not detected in either eye. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily topical ocular administration of latanoprost solution (0.005%) reduced IOP in healthy dogs without inducing adverse effects but did not affect IOP in healthy cats. Latanoprost may be useful for treating glaucoma in dogs.     

Renal ultrasonography in healthy cats

Serial ultrasonographic examinations were performed on the kidneys of 10 healthy cats during normal hydration and after administration of contrast medium. Differences in the appearance of anatomic structures or in the echo intensity were not detected between kidneys during normal hydration and after contrast medium administration. The appearance of scanning images was influenced by mode, frequency, and focal range of the transducer, topography and mobility of the kidneys, and adequate sound conduction.     

Pharmacokinetics of cetirizine in healthy cats

OBJECTIVE: To develop a high-performance liquid chromatography (HPLC) assay for cetirizine in feline plasma and determine the pharmacokinetics of cetirizine in healthy cats after oral administration of a single dose (5 mg) of cetirizine dihydrochloride. ANIMALS: 9 healthy cats. PROCEDURES: Heparinized blood samples were collected prior to and 0.5, 1, 2, 4, 6, 8, 10, and 24 hours after oral administration of 5 mg of cetirizine dihydrochloride to each cat (dosage range, 0.6 to 1.4 mg/kg). Plasma was harvested and analyzed by reverse-phase HPLC. Plasma concentrations of cetirizine were analyzed with a compartmental pharmacokinetic model. Protein binding was measured by ultrafiltration with a microcentrifugation system. RESULTS: No adverse effects were detected after drug administration in the cats. Mean +/- SD terminal half-life was 10.06 +/- 4.05 hours, and mean peak plasma concentration was 3.30 +/- 1.55 microg/mL. Mean volume of distribution and clearance (per fraction absorbed) were 0.24 +/- 0.09 L/kg and 0.30 +/- 0.09 mL/kg/min, respectively. Mean plasma concentrations were approximately 2.0 microg/mL or higher for 10 hours and were maintained at > 0.72 microg/mL for 24 hours. Protein binding was approximately 88%. CONCLUSIONS AND CLINICAL RELEVANCE: A single dose of cetirizine dihydrochloride (approx 1 mg/kg, which corresponded to approximately 0.87 mg of cetirizine base/kg) was administered orally to cats. It was tolerated well and maintained plasma concentrations higher than those considered effective in humans for 24 hours after dosing. The half-life of cetirizine in cats is compatible with once-daily dosing, and the extent of protein binding is high.     

Pharmacokinetics of ibafloxacin in healthy cats

The pharmacokinetics of ibafloxacin following single and repeated administration of an oral gel formulation and the effect of food intake were investigated in cats. Ibafloxacin is a chiral fluoroquinolone available for clinical use as a racemic mixture of the R- and S-enantiomers. Plasma concentrations of ibafloxacin and its metabolites were determined using microbiological, LC-MS-MS and enantioselective capillary zone electrophoresis assays. Ibafloxacin was absorbed rapidly [time of maximum concentration (tmax) 2-3 h], reaching a mean maximum concentration (Cmax) of approximately 2.1 and 1.6 microg/mL for R- and S-ibafloxacin, respectively, following a single oral administration of the racemate at 15 mg/kg. Once absorbed, ibafloxacin was metabolized to 7-hydroxy-ibafloxacin and mainly to 8-hydroxy-ibafloxacin. Following repeated oral administration, significant increases in Cmax and AUC of ibafloxacin and its less active metabolites (racemic or enantiomers) were observed between the first and the tenth day of treatment. This twofold exposure increase in concentrations of ibafloxacin and its metabolites may contribute additionally to the efficacy of this drug in the treatment of feline bacterial infections. Single and repeated doses of ibafloxacin were well tolerated by cats. Food promoted the absorption of ibafloxacin, doubling Cmax and increasing AUC and slightly delaying tmax. High concentrations of the metabolites, mainly 8-hydroxy- and 7-hydroxy-ibafloxacin were excreted in urine, either unchanged or as glucurono-conjugates.     

Effect of clindamycin on factor-VII activity in healthy cats

Four healthy cats were given clindamycin orally in daily doses of 25 or 50 mg/kg of body weight for 6 weeks. Significant change in Factor-VII activity was not found, compared with pretreatment values. In 2 cats tested, toxin produced by Clostridium difficile was not detected in fecal samples obtained before treatment and at 6 weeks after treatment, suggesting that intestinal overgrowth by C difficile did not develop. Results of the study seemed to indicate that orally administered clindamycin does not measurably reduce synthesis of vitamin K-dependent clotting factors in healthy cats.     

Percutaneous ultrasound-guided cholecystocentesis in healthy cats

Percutaneous ultrasound-guided cholecystocentesis (PUC) is a minimally invasive technique for bile collection that is used successfully in human patients with cholecystitis. Its use in veterinary medicine for evaluation of hepatobiliary disorders has been limited because of the perceived unacceptable risk of bile peritonitis. An experimental study was conducted to evaluate the safety and efficacy of PUC, to collect data on bile cytology and bacteriologic culture, and to attempt to isolate Helicobacter spp. from the bile of healthy cats. In fasted and sedated cats, PUC was performed with a 22-gauge 1.5-in. (3.81 cm) needle with an attached 12-mL syringe via a right-sided transhepatic approach (n = 1) or into the fundus of the gallbladder (n = 11) via a right ventral abdominal approach. An attempt was made to completely empty the gallbladder. A small amount of abdominal effusion, consistent with bile or blood, was seen ultrasonographically immediately after aspiration in the 1st cat. Ultrasonographic complications with the 2nd technique were not observed in the remaining 11 cats. Decreased appetite and evidence of mild abdominal pain were detected in 4 cats within 2 days after PUC. The mean neutrophil count increased 2 days after PUC (P < .01) but remained within the reference range. The bile was acellular in 11 of 12 cats, and aerobic, anaerobic, and Helicobacter spp. cultures yielded no growth in 12 of 12 cats. There were no remarkable gross or histologic lesions of abdominal organs at the postmortem examination (8 cats) performed 7-8 days after the procedure. PUC appears to be a safe and technically simple procedure. Further studies are warranted to determine the use and safety of PUC in cats with hepatobiliary diseases.