Survival in cats with naturally occurring chronic kidney disease (2000-2002).

BACKGROUND: Duration of survival of cats with naturally occurring chronic kidney disease (CKD) is poorly characterized. HYPOTHESIS: Stage of kidney disease based on serum creatinine concentration (SCr) at the time of diagnosis and after correction of prerenal azotemia is strongly associated with duration of survival in cats. ANIMALS: Two hundred and eleven client-owned cats with naturally occurring CKD evaluated between April 2000 and January 2002. METHODS: Retrospective case review of 733 cats with SCr > 2.3 mg/dL. Examination of the medical records identified 211 cats that met all other inclusion and exclusion criteria for this study. Clinical characteristics, clinicopathologic data, and survival times were extracted from the medical record. Owners and referring veterinarians were contacted by phone to obtain follow-up if it was not documented in the record. Kaplan-Meier survival curves were performed to determine survival times for International Renal Interest Society (IRIS) stage both at diagnosis and at baseline (ie, after correction of prerenal azotemia). RESULTS: Median survival for cats in IRIS stage IIb at the time of diagnosis was 1,151 days (range 2-3,107), and was longer than survival in stage III (median 778, range 22-2,100) or stage IV (median 103, range 1-1,920) (P-value< .0001). P-value for effect of stage at diagnosis was < .0001. CONCLUSIONS AND CLINICAL IMPORTANCE: IRIS stage of CKD based on serum creatinine at the time of diagnosis is strongly predictive of survival in cats with naturally occurring CKD.

Identification of Listeria innocua surrogates for Listeria monocytogenes in hamburger patties.

Listeria innocua M1 has been used by many researchers as a nonpathogenic thermal processing surrogate for Listeria monocytogenes. However, L. innocua M1 has been criticized because its thermal survivability characteristics are not as closely parallel to L. monocytogenes as some would like in a variety of foods and processing conditions. The present study was conducted to compare multiple L. innocua and L. monocytogenes strains to validate L. innocua M1 as the ideal surrogate under high-temperature thermal processing conditions for L. monocytogenes. The D- and z-values of L. innocua M1, L. innocua strain SLCC 5639 serotype (6a), SLCC 5640 (6b), SLCC 2745 (4ab), and L. monocytogenes F4243 (4b) were calculated for raw hamburger patties. Hamburger patties were inoculated with 10(7-8) CFU/g of L. monocytogenes or L. innocua. Samples were heat treated at 4 temperatures (62.5 to 70 degrees C). At each temperature, the decimal reduction time (D-value) was obtained by linear regression of survival curves. The D- and z-values were determined for each bacterium. The D-values of L. innocua and L. monocytogenes serotypes ranged from 3.17 to 0.13 min at 62.5 to 70 degrees C, and the z-values of L. innocua and L. monocytogenes were 7.44 to 7.73 degrees C. Two of the 4 L. innocua serotypes used in this experiment have the potential for use as surrogates in hamburger meat with varying margins of safety. L. innocua M1 should serve as the primary nonpathogenic surrogate with the greatest margin of safety in verifying a new thermal process to destroy L. monocytogenes.

An innovative absorbable coating for the polybutester suture.

The polybutester (PBE) suture has been coated with an absorbable polytribolate polymer that is composed of glycolide (9%), epsilon-caprolactone (51%), and poloxamer 188 (40%) to reduce its drag forces. It is the purpose of this study to document the influence of this coating on the biomechanical performance of both PBE sutures and polypropylene (PP) sutures. The performance parameters evaluated were breaking strength, elongation, stiffness, knot security, knot run down, and tissue drag. The breaking strength of PP sutures was remarkably similar to that of coated and uncoated PBE sutures. In size 5/0 PP sutures, the sutures exhibited considerably greater elongation at knot break than did comparably sized PBE sutures. The PBE suture elongated under low loads, but returned to its original length when the load was removed. In contrast, the PP suture elongated irreversibly at high loads, exhibiting creep. Coated and uncoated PBE sutures exhibited less stiffness than PP sutures and exhibited limited memory after removal from the suture package. Coating the PBE suture markedly reduced its drag forces in musculoaponeurotic, colonic, and vascular tissue. Knot security with the coated PBE suture was achieved with only one more throw than with comparably sized uncoated PBE sutures. On the basis of the results of this study, coating the PBE suture represents another major advance in suture performance.

Imaging pitfalls of interbody spinal implants.

STUDY DESIGN: A variety of interbody implants were imaged by computed tomography and plain radiography within cadaveric spines to evaluate their basic imaging characteristics. OBJECTIVES: Sources of interpretation error by both computed tomography and plain radiography of interbody implants were investigated. SUMMARY OF BACKGROUND DATA: Lucencies have been reported around bone dowel implants in the postoperative period, which have been shown to resolve. The diagnosis of fusion through metallic implants has been difficult with both false-positive and false-negative results. The literature of imaging these implants is very sparse. METHODS: Four interbody constructs were placed in cadaveric spines under different conditions and imaged using both computed tomography and plain film radiography. RESULTS: Plain radiographs could not predict the presence of intraimplant bone whereas computed tomography was accurate. Metallic implants had a 1-3-mm computed tomography artifact limiting peri-implant interpretation. Lucencies could be seen on computed tomography but not on plain radiographs. However, the opposite was also seen. Lucencies around nonmetallic implants were more visible by a 4:1 ratio. CONCLUSIONS: Potential errors in interpretation were identified including assessment for bridging bone, assessment for lucency, and obscuration of peri-implant detail from metallic artifact. Lucencies were more visible with nonmetallic implants than with metallic constructs. Plain radiograph analysis of metallic implants tended to underestimate lucencies, whereas analysis of nonmetallic implants tended to overestimate lucencies.

Magnitude and time course of extracellular potassium inhomogeneities during acute ischemia in pigs. Effect of verapamil.

Prior studies have demonstrated the presence of inhomogeneities in myocardial [K+]e after serial 10-minute occlusions of the left anterior descending coronary artery in the pig, even within restricted locations of an ischemic zone. These inhomogeneities are thought to underlie the electrophysiological abnormalities responsible for lethal ventricular arrhythmias through reentrant and nonreentrant pathways, but a clear association has not been demonstrated. As a prerequisite to establishing this association, these studies were performed to establish measurement standards for [K+]e inhomogeneity, to quantify the magnitude and time course of these inhomogeneities, to determine whether the inhomogeneities are greater in the ischemic border where lethal ventricular arrhythmias are known to originate, and to assess the effect of a known antifibrillatory drug on [K+]e inhomogeneities. [K+]e (expressed as the change in potassium equilibrium potential, dEK [mV]) was measured in 15 preparations using an average of 17 closely spaced, critically calibrated K(+)-sensitive electrodes having stable response characteristics. A series of four 10-minute occlusions each separated by a 50-minute reperfusion period were performed in each study. In half of the studies, intravenous verapamil (0.2 mg/kg bolus followed by 0.0065 mg/kg/hr) was administered before the fourth occlusion. In nine studies (five control and four verapamil), electrodes were placed in the marginal ischemic zone (from 2 mm outside to 5 mm inside the visible cyanotic border). In six other studies (three control and three verapamil), electrodes were placed in the central ischemic zone (10-20 mm within the ischemic region). We determined that the standard deviation is the best measure of inhomogeneity and that 12 equivalent measurement sites are required to estimate it with a satisfactory degree of statistical confidence. We found that after 10 minutes of ischemia, mean dEK was 1.6 times greater in the central than in the marginal ischemic zone, whereas mean standard deviation at the same time was 1.5 times greater in the marginal than in the central ischemic zone. Verapamil reduced mean dEK and mean standard deviation in both ischemic zones for most of the occlusion by delaying the rise in [K+]e and the inhomogeneity of that rise by 3-5 minutes. Comparisons of mean dEK with mean standard deviation revealed a steep linear relation in the marginal zone and a curvilinear relation in the central zone where higher mean dEK values were not accompanied by higher values for mean standard deviation. Furthermore, we determined that these relations were not altered by verapamil.(ABSTRACT TRUNCATED AT 400 WORDS)

An investigation of skin deformation around percutaneous devices.

According to the literature one of the primary failure models of percutaneous devices (PDs) in soft tissue implantation sites is that of mechanically induced trauma along the implant/tissue interface. In order to avoid such avulsion, subcutaneous flanges have been incorporated into PD designs to provide a better distribution of stresses along the implant/tissue interface. Tissue necrosis and inflammation were then observed to be most pronounced around the rim of the subcutaneous flange. It was the goal of this study to develop and test PDs with subcutaneous flanges of varying stiffnesses in order to allow the flange to distribute stresses into the surrounding tissues more evenly, thereby reducing the likelihood of failure due to avulsion. PDs were tested with flanges of constant thickness or varying linearly, reducing toward the flange rim. They were evaluated using an in-vitro testing method which was designed to simulate the situation of an implanted PD subjected to external loading. The results indicated that the stiffness characteristics of the subcutaneous flange had a substantial effect on the behavior of the devices under loading. A PD having a radial stiffness decrease would improve the likelihood of implant survival in the clinical situation due to the reduction of mechanically induced trauma along the implant/tissue interface.

Effects of calcium entry blockers on coronary constriction and myocardial ischemia due to leukotriene D4.

Recent studies show that leukotrienes (LTs) produce profound coronary artery constriction. Although calcium entry blockers are commonly used to remedy coronary vasospasm, their capacity to interfere with LT-mediated coronary constriction is unknown. Therefore, we compared effects of intracoronary LTD4 before and during treatment with calcium entry blockers in the in situ, blood-perfused hearts of domestic pigs. Intravenous administration of verapamil (0.1-1.6 mg/kg), nifedipine (10 or 100 micrograms/kg) or diltiazem (0.6-2.0 mg/kg) sufficient to increase base-line coronary blood flow (CBF) and decrease mean arterial pressure did not change decrement in CBF after LTD4. Infusion of verapamil (0.01-0.04 mg/min) into the left anterior descending coronary artery raised pre-LTD4 CBF almost 2-fold without alteration in mean arterial pressure, heart rate or left ventricular end-diastolic pressure. Intracoronary boluses of LTD4 (0.3, 1.0 and 3.0 micrograms) during verapamil infusion into the same vessel caused dose-dependent decreases in CBF identical to those observed when LTD4 was injected during control infusion. ECGs showed myocardial ischemia during severe flow reduction after high dose intracoronary LTD4 (3.0 or 10.0 micrograms). When the same LTD4 doses were injected during intracoronary verapamil, electrocardiographic changes did not occur despite similar decreases in CBF. The capacity of verapamil to prevent LTD4-induced ischemia may be caused by higher residual CBF after LTD4 even though the magnitude of LTD4-induced CBF decrement was unaltered. LTD4-induced coronary constriction seems to be mediated by a mechanism unrelated to calcium entry channels blocked by verapamil, nifedipine or diltiazem.

Effect of platelet-activating factor on coronary circulation of the domestic pig.

The platelet-activating factor released by white blood cells and platelets has been shown to be 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC). To fully understand the cardiovascular actions of this substance, we examined the effects of AGEPC on coronary blood flow (CBF) and other hemodynamic parameters in anesthetized open-chest domestic pigs. Mean arterial blood pressure (MBP), electrocardiogram, heart rate (HR), left ventricular pressure, and CBF were continuously recorded. AGEPC was injected (bolus, 0.1 ml) into the left anterior descending coronary artery at increasing doses of 0.03-10 nmol. Intracoronary AGEPC produced biphasic changes in CBF: a dose-dependent increase in CBF (up to 50%) followed by a decrease (up to 92%) in CBF. The changes in CBF were not directly related to any systemic effect, although MBP was reduced consistently after a dose higher than 1 nmol of AGEPC. The increase in CBF produced by AGEPC was not affected by pretreatment with indomethacin (6 mg/kg) or FPL 55712 (1 or 3 mg), an inhibitor of slow-reacting substance of anaphylaxis (SRS-A). The decrease in CBF produced by AGEPC was attenuated by FPL 55712 and blocked by indomethacin. These data suggest that AGEPC release from aggregating platelets might play a major role in modulating CBF and cardiac function in states involving platelet-coronary interaction.

Effects of FPL-55712 or indomethacin on leukotriene-induced coronary constriction in the intact pig heart.

Intracoronary leukotriene D4, 0.1-3.0 micrograms (0.2-6.0 nmol), produced dose-dependent decreases in coronary flow of anesthetized pigs. Pretreatment with intracoronary FPL-55712 (0.1, 0.3 and 1.0 mg) reduced coronary constriction due to 1.0 micrograms leukotriene D4 by up to 77%. FPL-55712 did not produce sustained alterations in coronary flow, left ventricular end-diastolic pressure, systemic arterial pressure, or heart rate. Indomethacin pretreatment (6 mg/kg i.v.) had no effect on leukotriene-induced coronary constriction. Inhibition produced by FPL-55712 may be useful in disease states involving leukotriene-mediated coronary constriction.

Coronary constriction by leukotriene C4, D4, and E4 in the intact pig heart.

Leukotrienes are naturally occurring vasoactive metabolites of arachidonic acid that increase during inflammatory reactions and anaphylaxis. Coronary constriction and reduced myocardial contractility after leukotriene C4 and D4 administration were demonstrated in the isolated guinea pig heart. To explore the effects of leukotrienes in the in situ, blood-perfused heart, we administered leukotrienes C4, D4, and E4 into the coronary artery of the domestic pig. Increasing doses (0.1, 0.3, 1.0, and 3.0 micrograms) of leukotrienes C4, D4, and E4 were injected into the left anterior descending coronary artery of 8 open-chest domestic pigs. Significant dose-related reduction in coronary blood flow was observed after each leukotriene administration. Three micrograms of each leukotriene produced the following maximal decreases (mean +/- standard error); C4 = 80 +/- 9%, p less than 0.001; D4 = 81 +/- 3%, p less than 0.001; E4 = 64 +/- 12%, p less than 0.005. In several instances, surface electrograms recorded from the myocardial region exposed to leukotrienes showed signs of focal myocardial ischemia, sometimes accompanied by ventricular arrhythmia. Significant elevation of left ventricular end-diastolic pressure was observed after large doses (1 or 3 micrograms) of leukotrienes C4 and D4. Minimal (5 to 10%) decreases in mean arterial pressure and no change in heart rate were observed after leukotriene injection. We conclude that leukotrienes C4, D4, and E4 are extremely potent coronary constrictors in the in situ heart. The intensity of response and associated electrocardiographic signs of ischemia suggest that constriction is mainly due to a primary effect on vascular smooth muscle. However, coronary flow reduction may also reflect consequences of a primary negative inotropic action. Leukotrienes may play a significant role in the pathogenesis of a variety of cardiac disorders, particularly those associated with extensive inflammatory changes.

Effect of adenosine on transmural myocardial blood flow distribution in the awake dog.

Studies were conducted to determine the effects of adenosine on transmural myocardial blood flow distribution. Both maximal and submaximal vasodilatory doses of adenosine were infused into awake resting dogs chronically instrumented with coronary flow probes and aortic and left atrial pressure catheters. Radioactive microspheres (8-10 micron) were used to determine regional coronary blood flow. Four experimental protocols were evaluated: 1) the effects of maximal (1.00 mg . kg-1 . min-1) as well as submaximal (0.45 mg . kg-1 . min-1) vasodilatory levels of adenosine, 2) the dose-response characteristics of adenosine, 3) the dose-response characteristics of dipyridamole, and 4) the effects of adenosine in the presence of an increased arterial PO2. The data indicate that maximal vasodilatory doses of adenosine have little effect on the endocardial-to-epicardial blood flow ratio, whereas submaximal doses result in a marked preferential endocardial perfusion. This relative increase in endocardial perfusion was not altered by hyperoxia. Dipyridamole, in submaximal doses, produced a similar preferential flow to the endocardial layer. These data demonstrate that the vasodilator reactivity to adenosine infusion is greater in the endocardial layer,