Results of renal ultrasonography performed before and during administration of saline (0.9% NaCl) solution to induce diuresis in dogs without evidence of renal disease.

OBJECTIVE: To evaluate the effect of saline (0.9% NaCl) solution administered IV to induce diuresis on 15 dimensional variables of the kidneys, size of renal pelvis, and diameter of the cranial part of the ureters. ANIMALS: 25 dogs without evidence of renal disease that were undergoing chemotherapy for various neoplasms. PROCEDURE: The kidneys, cranial aspect of the ureters, and trigone area of the urinary bladder of each dog were examined ultrasonographically before and during IV administration of saline solution (2.7 to 18.8 ml/kg of body weight/h). RESULTS: Ultrasonography revealed unilateral and bilateral pyelectasis during diuresis in 16 of 23 (70%) dogs but unilateral pyelectasis in only 1 dog before diuresis. Unilateral pyelectasis during diuresis was observed in 11 of 16 (69%) dogs. Pyelectasis during diuresis was categorized as slight in 15 of 21 (71%) kidneys. Degree of pyelectasis during diuresis was not identical in both kidneys of 13 of 16 (81 %) dogs. Diuresis did not induce ureterectasis, and it did not cause changes in 15 dimensional variables of the kidneys. CONCLUSIONS: In nonsedated, nonazotemic dogs, IV administration of saline solution to induce diuresis may cause slight pyelectasis without evidence of ureterectasis. CLINICAL RELEVANCE: When dilatation of the cranial part of the ureter is > 2 mm at the same time that ipsilateral pyelectasis is detected during ultrasonographic examination of the urinary tract system of a nonsedated, nonazotemic dog receiving IV administration of saline solution to induce diuresis, additional examinations are recommended to determine the possibility of early obstructive nephropathy or pyelonephritis.

Cardiorespiratory and anesthetic effects of propofol and thiopental in dogs.

OBJECTIVE: To compare cardiorespiratory and anesthesia effects of IV administered propofol and thiopental in dogs. ANIMALS: 6 healthy mixed-breed dogs. PROCEDURE: Each dog was anesthetized with isoflurane, then a thermistor catheter was inserted in the pulmonary artery. After a minimum of 2.5 hours of recovery, a catheter was placed in a cephalic vein for administration of lactated Ringer's solution and drugs. Propofol (8 mg/kg of body weight) or thiopental (19.4 mg/kg) was administered to each dog in a randomized crossover design study. All dogs were intubated and allowed to breathe 100% oxygen spontaneously. Heart rate and rhythm; systolic, diastolic, and mean arterial blood pressures; respiratory rate; end-tidal carbon dioxide concentration; tidal volume; and reflexes (toe web pinch, palpebral response, and jaw tone) were measured before and every 2 minutes for the first 10 minutes, then at 15, 30, and 60 minutes after drug administration. Cardiac output was determined at 0, 2, 6, 10, 15, 30, and 60 minutes, and blood samples were collected at 0, 2, 10, and 30 minutes. Time to endotracheal extubation, head lift, and ability to sit sternally and walk unaided were recorded. RESULTS: 3 of 6 dogs in each group were apneic after drug administration. Reflexes were decreased similarly for both anesthetic agents, but were not completely lost. Time to sternal position and walking unaided were significantly shorter in response to propofol. CONCLUSION: Anesthesia was rapid; however, respiratory depression and apnea were major adverse effects associated with propofol and thiopental. Propofol has the advantage of inducing rapid, coordinated anesthesia recovery.

Diagnostic imaging of the feline lower urinary tract.

Survey radiography, double contrast cystography, and antegrade urethrocystography are valuable imaging tools available to the clinician for evaluation of cats with lower urinary tract disease. However, to be cost effective during patient evaluation, diagnostic radiographic procedures should be used only when needed. An algorithm is presented that describes when radiographic imaging techniques may be most cost effective in providing useful information during the clinical workup of cats with lower urinary tract disease.

Evaluation of activity of putative superoxide dismutase mimics. Direct analysis by stopped-flow kinetics.

By stopped-flow kinetic analysis, we have directly evaluated the superoxide dismutase (SOD) activity of a number of organic nitroxides and iron- and manganese-based complexes that have been attributed with having SOD activity based upon competition experiments with cytochrome c. In 60 mM HEPES buffer, pH 8.1, or 50 mM potassium phosphate buffer, pH 7.8, Mn(II) and manganese complexes of desferal had no detectable SOD activity by stopped-flow analysis (catalytic rate constant (kcat) < 10(5.5) M-1 s-1), whereas Mn(II) and manganese complexes of desferal inhibited the reduction of cytochrome c by superoxide generated by the xanthine/xanthine oxidase system. Fe(II)-N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (FeTPEN) was eight times more active than Fe(III)-tris[N-(2-pyridylmethyl)-2-aminoethyl]amine(Fe-TPAA) in the cytochrome c assay, but only FeTPAA catalyzed the first-order decay of superoxide (kcat = 2.15 x 10(6) M-1 s-1) by stopped-flow. Fe(III)-tetrakis(4-N-methylpyridyl)porphine (FeTMPP) was active at low micromolar concentrations in both the cytochrome c and stopped-flow assays. At high micromolar concentrations, the organic nitroxides 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPOL) were inhibitory in the cytochrome c assay, but showed no detectable SOD activity by stopped-flow. None of the tested compounds inhibited xanthine oxidase activity as shown by the measurement of urate production. Under the conditions of the cytochrome c assay, FeTPEN, TEMPO, and TEMPOL oxidized reduced cytochrome c which rationalizes the false positives for these compounds in this assay. The inhibitory activities of Mn(II) and the manganese desferal complexes in the cytochrome c assay appear to be due to a stoichiometric, not catalytic, reaction with superoxide as catalytic amounts of these agents do not induce a first-order decay of superoxide as shown by stopped-flow.

Stopped-flow kinetic analysis for monitoring superoxide decay in aqueous systems.

We have utilized a commercially available, computer-driven stopped-flow spectrophotometer to rapidly measure the self-dismutation or catalyzed decay of superoxide in aqueous buffers. In the self-dismutation assay, a dimethyl sulfoxide solution of superoxide is mixed in less than 2 ms with an aqueous buffer. The decay of superoxide is monitored directly by its absorbance at 245 nm and the data is processed by computer. By careful purification of the water and the use of metal-free buffers, a decay of superoxide that fits second-order kinetics is obtained without using metal ion chelators in the buffer. The second-order rate constant for superoxide decreased with increasing pH and decreased by a factor of 3.3 by using D2O in place of H2O in the buffer. The rapid mixing time makes it possible to determine rate constants for active superoxide dismutase catalysts at a pH as low as 7. A first-order decay of superoxide is obtained when the aqueous buffer contains bovine Cu/Zn superoxide dismutase or aquo copper(II), which are known catalysts of superoxide dismutation. The rate of superoxide decay was established to be first-order in catalyst. The catalytic rate constant for bovine Cu/Zn superoxide dismutase was determined to be 2.3 x 10(9) M-1 s-1 in H2O and D2O-based buffers and was independent of pH over the range 7-9. Aquo copper(II) gave a catalytic rate constant of 1.2 x 10(8) M-1 s-1, but was ineffective in the presence of EDTA. The catalytic rate constants obtained by stopped-flow kinetics are in excellent agreement with studies carried out by the direct method of pulse radiolysis.