Obstruction In Dogs Research Articles

Effect of Intravenous Mannitol upon the Resistive Index in Complete Unilateral Renal Obstruction in Dogs

Effect of Intravenous Mannitol upon the Resistive Index in Complete Unilateral Renal Obstruction in Dogs

Diuretic Doppler ultrasonography in chronic unilateral partial ureteric obstruction in dogs.

To compare the effects of diuresis induced by a loop diuretic (frusemide), an osmotic diuretic (mannitol) and a high-osmolar radio-contrast medium (sodium iothalamate) on the intrarenal resistive index (RI) in dogs with chronic unilateral partial ureteric obstruction (UPUO). The split renal clearance and intrarenal RI were estimated in 11 dogs with chronic UPUO. Doppler ultrasonography measurements of the interlobar arteries were obtained before and 10 min after the intravenous infusion of 1 mg/kg frusemide, 1 g/kg mannitol or 20 mL 60% sodium iothalamate. The same experimental protocol was repeated with another drug at 1-week intervals. There was a significant difference between the intrarenal RI of obstructed and unobstructed kidneys in the chronic phase of UPUO. While mannitol and sodium iothalamate significantly increased the RI in both kidneys, differences in RI between the kidneys decreased after infusing the two drugs. However, while frusemide insignificantly increased the RI in the obstructed kidney, it decreased the RI in unobstructed one. Consequently, the difference in RI between the kidneys increased significantly after administering frusemide. There were no significant differences in urinary volume after administering each of the drugs. As there were no significant differences in the diuretic effects of the drugs, frusemide may have additional effects on the RI of unobstructed kidneys other than diuresis. Frusemide increased the difference between the intrarenal RI of the kidneys and therefore may improve the detection of unilateral urinary obstruction in humans.

The effects of alpha-adrenergic agonists on hyperpnea-induced airway obstruction in dogs.

Two alpha-adrenergic agonists that inhibit hyperpnea-induced airway obstruction (HIAO) in asthmatic subjects were used to examine the role of bronchial blood flow in the development of HIAO in canine periphery airways. A bronchoscope was used to record peripheral airway resistance (Rp) in anesthetized dogs before and after hyperpnea with dry air. Hyperpnea increased Rp 64 +/- 8% (mean +/- SE) above baseline. Treatment with norepinephrine (NOR) either before or at various times after hyperpnea inhibited HIAO (p < 0.01). We also found that NOR inhibited acetylcholine-induced bronchoconstriction. However, beta-adrenergic blockade with propranolol completely eliminated these effects. Thus, NOR inhibited HIAO in canine peripheral airways via the stimulation of beta-adrenergic receptors and the attenuation of airway smooth muscle contractility. In contrast, pretreatment with methoxamine (MX) decreased HIAO by approximately 25% when compared with the vehicle control, and this effect was completely eliminated by alpha-adrenergic blockade with phentolamine. Relative to NOR, MX provides weak protection against HIAO via the direct stimulation of alpha-adrenergic receptors and their subsequent effect on either mucus secretion or bronchovascular tone. We conclude that bronchial blood flow plays at best a minor role in the development of HIAO.

Placement of a permanent cystostomy catheter to relieve urine outflow obstruction in dogs with transitional cell carcinoma

Placement of a permanent cystostomy catheter to relieve urine outflow obstruction in dogs with transitional cell carcinoma

Factors determining lobar emptying during maximal and partial forced deflations in nonhomogeneous airway obstruction in dogs.

The partial expiratory flow-volume (PEFV) maneuver has been proposed as a sensitive test to detect nonuniform airway disease. We tested this hypothesis in seven dogs in an open-chest preparation in which the right upper lobe (RUL) bronchus was partially obstructed. Alveolar capsules were placed on the obstructed RUL and nonobstructed right lower lobe (RLL) to measure respective alveolar pressures (Palv) during PEFV and maximal expiratory flow-volume (MEFV) maneuvers. PEFV curves were initiated at about 75% of the whole-lung vital capacity (VC). A Pitot static tube was placed into the airway to identify sites of flow limitation (choke-points [CP]), frictional pressure losses to CP (Pfr), CP area (A*), and compliance (K*). Results were analyzed at 45% VC, where a central tracheal CP was identified, and at 29% VC, where lobar CP were identified. At both lung volumes, the results showed that during PEFV, Palv and flows of the obstructed RUL decreased, whereas Palv and flows of the RLL increased compared with values obtained during MEFV. However, total maximal expiratory flow (Vmax) did not change between maneuvers. At 45% VC, although Pfr decreased during PEFV, this decrease was not large enough to result in an increase in A* and hence total Vmax because CP were identified in the noncompliant trachea. At 29% VC, offsetting changes in lobar A* and flow occurred between maneuvers: during PEFV, RLL A* and flow relatively increased while RUL A* and flow decreased. This study describes the mechanisms that explain why the PEFV maneuver is not useful in the detection of nonhomogeneous airway obstruction.

Pulmonary edema associated with upper airway obstruction in dogs.

In order to evaluate the effect of acute upper airway obstruction upon pulmonary edema (PE) formation, we studied seven dogs that were subjected to inspiratory obstruction for three hours. Hypoxia was avoided by the administration of supplemental oxygen during the study period. Six dogs developed pulmonary vascular congestion, and four developed histologic findings of PE. Inspiratory intrapleural pressure decreased to -28 +/- 4 mmHg in dogs that developed PE and to -23 +/- 2 mmHg in dogs that did not. Transmural pulmonary artery pressure and pulmonary artery wedge pressure did not increase significantly. Central venous pressure during inspiration (CVPi) increased in all dogs, and CVP at end expiration (CVPe) was significantly higher in dogs with PE. Dogs that developed PE experienced a decrease in cardiac output and an increase in systemic vascular resistance. Furthermore, alveolar ventilation declined in dogs with PE, ultimately resulting in ventilatory failure. Pulmonary edema formation was not preceded by an increase in pulmonary vascular pressures but was associated with higher CVP, pulmonary vascular congestion, and hypercarbia.

Abstracts

Use of hepatobiliary scintigraphy in the diagnosis of extrahepatic biliary obstruction in dogs and catsEvaluation of rhinoscopy and rhinoscopy‐assisted mucosal biopsy in diagnosis of nasal disease in dogs

DIAGNOSIS OF URINARY TRACT OBSTRUCTION IN DOGS USING DUPLEX DOPPLER ULTRASONOGRAPHY

The ability of duplex Doppler ultrasonography to assist with the diagnosis of urinary tract obstruction was investigated in a study of 5 dogs with surgically induced, unilateral ureteral obstruction. The resistive index (RI) of obstructed kidneys was compared to that of controls and to the contralateral unobstructed kidneys. The RI was also evaluated following relief of obstruction. On the basis of an RI measurement ≥0.70 indicating obstruction, a sensitivity of 73% and a specificity of 77% was determined for the diagnosis of obstruction with Doppler ultrasonography. Although mean RI was elevated in obstructed kidneys compared to controls, it was concluded that a high false‐negative rate (27%) limits the clinical usefulness of Doppler ultrasonography for the detection of urinary obstruction in dogs. The RI difference between obstructed and nonobstructed kidneys was also evaluated within individual animals, but the magnitude of difference between kidneys did not significantly improve the detection rate for obstruction.

Neurostimulation for Obstructive Sleep Apnea: Investigations

Neurostimulation of the upper airway muscles (accessory muscles of respiration) was accomplished in anesthetized dogs and sleeping humans by electrical stimulation of the hypoglossal nerves. Such stimulations relieved partial airway obstructions in dogs. They also aborted (shortened) obstructive sleep apnea events in humans who suffer with obstructive sleep apnea syndrome. In one subject, stimulations delivered in advance of apneic events (by automatic cycling) prevented apneas. Neurostimulation for obstructive sleep apnea may be an important concept for future research and development.

Use of hepatobiliary scintigraphy in the diagnosis of extrahepatic biliary obstruction in dogs and cats: 25 cases (1982-1989)

Summary Twenty-five animals (21 dogs and 4 cats) in which hepatobiliary scintigraphy (hbs) was performed between 1982 and 1989 were included in a retrospective study to determine the utility of hbs for diagnosis of extrahepatic biliary obstruction. Final diagnoses, which were based on liver biopsy results and surgical findings in all animals, were hepatocellular disease alone (n = 17), hepatocellular disease and extrahepatic biliary obstruction (n = 7), and normal liver (n = 1). Hepatobiliary scintigraphy was performed by use of 99mTc-diisopropyl iminodiacetic acid in all cases. All 7 cases of extrahepatic biliary obstruction were confirmed at surgery. In animals with biliary obstruction, hbs failed to demonstrate radiolabel within either the gallbladder or intestine at any time. Using nonvisualization of the intestine by 180 minutes as the scintigraphic criterion for diagnosis of biliary obstruction, sensitivity was 83% and specificity was 94% in this series. Hepatobiliary scintigraphy was concluded to be an accurate indicator of extrahepatic biliary obstruction in this group of animals. High serum bilirubin concentration at the time hbs was performed did not appear to reduce the diagnostic usefulness of the scintigraphic findings.

An experimental study of gastrointestinal motility during chronic large bowel obstruction

Gastrointestinal motility and plasma PYY levels were investigated under chronic progressive large bowel obstruction in dogs. The obstruction device was applied around the descending colon at a laparotomy and gastrointestinal motility was recorded with strain gauge force transducers in the conscious state. Complete obstruction occurred at 26 days (21-33 days). The duration of postprandial interruption of motor complex (DIMC) in the antrum and duodenum were prolonged progressively, at partial obstruction (17.7 +/- 2.7 hr; p less than 0.05) and complete obstruction (23.0 +/- 4.0 hr; p less than 0.01) vs in control (13.7 +/- 1.9 hr), while DIMC in the small bowel showed no significant changes. Progressive obstruction caused hypermotility in the proximal colon to the obstruction and hypomotility in the distal colon. These dysmotility were improved after resection of the obstructed segment and anastomosis. Plasma PYY levels in the fasting state showed no significant increase at complete obstruction (42.6 +/- 14.5 pmol/l) vs in control (32.9 +/- 10.2 pmol/l).

Renal Arterial Duplex Doppler Ultrasound in Dogs with Urinary Obstruction

Recent clinical studies using duplex Doppler sonography identified an alteration in renal arterial blood flow in obstructed hydronephrotic kidneys that reportedly can be used to distinguish obstructive from nonobstructive collecting system dilatation. We attempted to verify these clinical findings and establish the temporal relationship of the alteration in the Doppler spectrum to the onset of urinary obstruction by evaluating surgically induced urinary obstruction in dogs. We performed laparotomies on 11 dogs, with the left ureter isolated and ligated in five dogs, and left intact in six dogs (control group). Duplex Doppler examination of the left renal arteries performed nine times during the first postoperative month identified a statistically significant difference (ρ less than .05) in the Doppler resistive index calculation between the two groups on days 1, 2, 4, and week 4. A resistive index discriminatory threshold of 0.7 (greater than 0.7, obstructed; less than 0.7, nonobstructed) produced a test sensitivity of 74% and specificity of 77%. We conclude from our study that renal arterial duplex Doppler sonography can detect a change in renal perfusion as a result of urinary obstruction and that this change can be detected as early as 24 hours after obstruction. However, high false-positive and false-negative rates may limit the ability of this modality to reliably distinguish obstructive from nonobstructive collecting system dilatation.

Stimulation of rapidly adapting pulmonary stretch receptors by pulmonary lymphatic obstruction in dogs.

The effects of pulmonary lymphatic obstruction and pulmonary venous congestion on the activities of slowly adapting receptors (SAR) and rapidly adapting receptors (RAR) of the airways were examined in anaesthetized, artificially ventilated dogs. In 11 out of 12 RAR (12 dogs) examined, pulmonary lymphatic obstruction for a period of 20 min produced a sustained significant increase in activity without a significant change in peak airway pressure and dynamic compliance. The activity remained significantly elevated even after the pulmonary lymphatic obstruction was released. This stimulus was without effect on the SAR (n = 5 dogs). Pulmonary venous congestion alone increased the RAR activity (n = 7 dogs) significantly without producing significant changes in airway mechanics. Lymphatic obstruction, when superimposed upon congestion, did not produce a further significant increase in activity. In four dogs the effect of pulmonary venous congestion (left atrial pressure increased from 7.6 +/- 1.7 to 16.3 +/- 2.7 mmHg) (1 mmHg = 133.3 Pa) on pulmonary lymphatic flow was examined. The procedure caused a significant increase in lymph flow. These results suggest that in the dog, the RAR activity is influenced by changes in the pulmonary extravascular space.

Regulation of increase in anastomotic blood flow following pulmonary arterial occlusion.

We have previously shown that there is an acute increase in anastomotic bronchial blood flow (Qbr) after pulmonary arterial obstruction in dogs. We examined the role of arachidonic acid metabolites in mediating this increase. The left lower lobe (LLL) was isolated and perfused (zone 2) with autologous blood in open-chested anesthetized dogs (n = 19). Qbr was measured from the amount of blood that overflowed from the closed vascular circuit of the suspended LLL and changes in its weight. In the control animals, there was a prompt and significant increase in Qbr following pulmonary arterial obstruction. Pretreatment with indomethacin (n = 6) or sodium salicylate (n = 4) almost completely blocked this rise in Qbr. Following pulmonary arterial occlusion, there was a rise in both thromboxane and a prostacyclin metabolite (6-keto-PGF1 alpha) in the blood of the pulmonary circulation of the LLL, although the 6-keto-PGF1 alpha rose relatively more. Pretreatment with indomethacin caused a fall in both thromboxane and prostacyclin levels (n = 3), which no longer rose after pulmonary arterial occlusion. These findings suggested that the balance of the vasodilator (prostacyclin) and vasoconstrictor (thromboxane) prostaglandins may play an important role in mediating the rise in Qbr that follows pulmonary arterial obstruction.

Effect of imidazole on the recovery from bilateral ureteral obstruction in dogs.

The effects of indomethacin (INDO) and imidazole (IMID) on postobstructed kidney functions were evaluated in dogs after 24 h of bilateral ureteral obstruction (BUO). In vehicle-treated dogs 1 h after release of BUO, clearances of inulin and PAH (Cin and Cpah) were 37 and 26%, respectively, of the preobstruction values. Fractional sodium excretion (FEna) increased from 0.5 +/- 0.1 to 2.9 +/- 0.6. Urine osmolality (Uosmol) increased by 55 +/- 9 mosmol/kg H2O in response to 50 mU of aqueous vasopressin. In INDO-treated dogs, Cin and Cpah were 39 and 21%, respectively, of the preobstruction values. FEna increased from 0.7 +/- 0.2 to 4.0 +/- 0.9. Uosmol increased by 91 +/- 19 mosmol/kg H2O in response to vasopressin. This lack of beneficial effects of INDO may reflect its cancelling effect on prostaglandins' and thromboxanes' (TX) effects on the renal hemodynamics of the postobstructed kidney. To further assess the roles of TX in the postobstructed kidney, IMID, and inhibitor of TX synthesis, was given before the release of obstruction. In this group of dogs, the Cin of the postobstructed kidney did not differ from the preobstruction value. CC pah was 45% of the preobstruction value, a level significantly higher than in either vehicle- or INDO-treated dogs. FEna wa 1.5 +/- 0.2 before and 3.5 +/- 2.3 after obstruction. Uosmol increased by 187 +/- 51 mosmol/kg H2O after vasopressin, a level significantly higher than in vehicle-treated dogs. The present study suggests that IMID improves Cin, Cpah, FEna, and concentrating ability of the postobstructed kidney. TX may be responsible for the persistent reductions of Cin and Cpah in the postobstructed kidney.

Value of so called cholestasis markers in the dog: an experimental study

In experimental bile obstruction in dogs, the most sensitive change in blood plasma composition is the increase in alkaline phosphatase activity which occurs after eight hours. Maximum alkaline phosphatase activities (approximately 100 times normal values) occur between the fifth and the 14th day. The increase in activity is accompanied by smaller increases in gamma-glutamyl transferase activity, and total bilirubin concentration also increases to a smaller extent and less regularly. Cholestasis also induces an intense cytolysis which is demonstrated mainly by increases in glutamate dehydrogenase and alanine amino transferase activities which are more intense and lasting than those induced by 0.5 ml/kg carbon tetrachloride.

Coronary steal in four models of single or multiple vessel obstruction in dogs

Two types of coronary steal (subendocardial to subepicardial; collateral dependent to noncollateral dependent) were examined in four models of single or multiple vessel obstruction In 32 anesthetized dogs with controlled heart rate and aortic blood pressure. Different degrees of vasodilation were produced by use of the selective coronary arteriolar dilator, chromonar. Subendocardial to subepicardial steal was studied in two models of stenosis, mild (50 percent decrease in reactive hyperemia) and severe (93 percent decrease In reactive hyperemia). During mild left circumflex arterial stenosis, chromonar produced an Increase In poststenotic blood flow primarily In the subeptoardtum with only minimal increases in the subendocardium. The Ischemic endocardial epicardial flow ratio decreased significantly. During severe left circumflex stenosis, chromonar produced an increase in poststenotic subepicardial flow whereas subendocardial flow decreased. The ischemic endocardial epicardial flow ratio also decreased significantly. Changes In endocardial epicardial flow ratio correlated closely with distal diastolic perfusion pressure in both models of stenosis ( r = 0.84, p <0.001). Collateral-dependent to noncollateral-dependent steal was studied in two models of total left anterior descending coronary arterial occlusion. During distal occlusion of this artery, collateral blood flow decreased significantly only during chromonar-lnduced maximal vasodilation, whereas mild vasodilation produced a significant decrease in collateral flow when a proximal left circumflex stenosis was present in addition to occlusion of the left anterior descending artery. These results demonstrate that mild to maximal coronary vasodilation produces coronary steal in different models of single or multiple vessel disease In the absence of changes in aortic pressure and heart rate. Decreases in perfusion pressure distal to a stenosis or at the origin of collateral vessels are responsible for the two types of coronary steal.

Concurrent increases in resistance and transport after coronary obstruction in dogs.

We have extended earlier studies on coronary vascular permeability-surface area (PS) for [14C]sucrose to include observations of the transcoronary flow resistance before and after partial occlusion of the left anterior descending coronary artery. Multiple-tracer (MT) studies were conducted on 13 anesthetized dogs by inserting an isotope mixture (125I-albumin, 51Cr-red blood cells, [14C]sucrose, 3HOH) into a cannula connecting the carotid and the left anterior descending coronary artery. Analysis of blood sampled from the coronary sinus allowed calculation of PS, extravascular 3HOH volume (VT), and extravascular [14C]sucrose volume (VS). Flow reduction significantly reduced VT and VS and increased PS/VT relative to base line. Coronary resistance distal to the obstruction (R) decreased significantly immediately after flow reduction but then, over the low-flow period, increased significantly above this initial low-flow value. The mean R during reduced flow normalized to R immediately after flow reduction (Ri) correlated significantly with PS/VT during ischemia. Because R/Ri is not correlated with VT alone, we speculate that capillary permeability alterations may play a role in the deterioration of myocardial perfusion during ischemia.

The place of attack of beta-2 receptor stimulating bronchodilators. Fenoterol (Berotec) in allergic airway obstruction in dogs, hypersensitive to Ascaris suum

On dogs sensitive against Ascaris suum extract an increase of the airway resistance can be caused by challenge alone on the upper part or the lower part of the airways by Ascaris suum extract. Fenoterol as beta 2-receptor stimulator is capable to decrease this reaction by deposition of this drug on the upper part as on the lower part of the airways. The effect of Fenoterol on the upper part of the airways is much stronger and lasts much longer than on the lower part of the airways or by intravenous route. A direct effect of the beta 2-receptor stimulator Fenoterol on the sensoric part of the reflex way of the reflex bronchoconstriction must be considered. It will be also discussed that the local application of Fenoterol on the upper part of the airways may influence also the reaction of the bronchial muscles in the lower part of the airways without a direct resorptive-systemic effect. The relationship of these findings for the clinical situation on man has to be investigated.

FUNDAMENTAL STUDIES OF ANESTHESIA ON EXPERIMENTAL INTESTINAL OBSTRUCTION IN DOGS

Experiments were performed to make comparison between the influence of Halothane (H-I) and Ether (E-I) inhalation anesthesia on experimental intestinal obstruction (upper occlusion) in dogs, at the same time intact Halothane (H-N) and Ether (E-N) inhalation anesthesia for control anesthesia were carried out.Comparison was made of clinical findings, blood pressure, blood gases and acid-base balance, blood components and body fluid.The results were as follows:1) After 96 hours of intestinal obstruction, decrease of body fluid and plasma chloride which were caused by a vomiting, at the same time increase of pulse rate, blood concentrate, hypotonia and a mild acidemia were recognized.2) In E-I group, delay of time of the laryngo-pharyngeal reflexes were observed, and 2 heads of E-I group died without a completely awaking.3) Body temperature, pulse rate and respiratory rate resulted similar effects in all groups (H-N, E-N, H-I, E-I) .4) Arterial blood pressure depressed in intestinal obstruction groups (H-I, E-I) .5) Halothane anesthesia groups (H-N, H-I) exhibited respiratory acidosis, and Ether anesthesia groups (E-N, E-I) showed mixed acidosis. Furthermore, intestinal obstruction groups (H-I, E-I) were more aggravating than control groups (H-N, E-N), particularity, E-I group maintained after the end of anesthesia.6) Ht, Hb, plasma electrolytes and osmotic pressure did not change in all groups (H-N, E-N, H-I, E-I) .7) Body fluid volume were not difference between H-I and E-I group.From these results, it is presumed that use of Halothane inhalation anesthesia was better than Ether inhalation anesthesia on intestinal obstruction in dogs.