Pharmacologic identification of putative D1 dopamine receptors in feline kidneys

The pharmacokinetics of intravenous fenoldopam in healthy, awake cats

Fenoldopam is a selective dopamine-1 receptor agonist that improves diuresis by increasing renal blood flow and perfusion and causing peripheral vasodilation. Fenoldopam has been shown to induce diuresis and be well-tolerated in healthy cats. It is used clinically in cats with oliguric kidney injury at doses extrapolated from human medicine and canine studies. The pharmacokinetics in healthy beagle dogs has been reported; however, pharmacokinetic data in cats are lacking. The goal of this study was to determine pharmacokinetic data for healthy, awake cats receiving an infusion of fenoldopam. Six healthy, awake, client-owned cats aged 2-6 years old received a 120-min constant rate infusion of fenoldopam at 0.8 μg/kg/min followed by a 20-min washout period. Ascorbate stabilized plasma samples were collected during and after the infusion for the measurement of fenoldopam concentration by HPLC with mass spectrometry detection. This study showed that the geometric mean of the volume of distribution, clearance, and half-life (198 mL/kg, 46 mL/kg/min, and 3.0 mins) is similar to pharmacokinetic parameters for humans. No adverse events were noted. Fenoldopam at a constant rate infusion of 0.8 μg/kg per min was well tolerated in healthy cats. Based on the results, further evaluation of fenoldopam in cats with kidney disease is recommended.

Administration of fenoldopam in critically ill small animal patients with acute kidney injury: 28 dogs and 34 cats (2008-2012)

OBJECTIVE

To describe the clinical features and outcomes of critically ill dogs and cats with acute kidney injury (AKI) receiving fenoldopam infusions compared to patients with AKI that did not receive fenoldopam.

DESIGN

Retrospective clinical study from May 1, 2008 until June 1, 2012.

SETTING

Private emergency and specialty referral hospital.

ANIMALS

Client-owned dogs (28) and cats (34) with AKI that received fenoldopam compared with similar patients with AKI (30 dogs and 30 cats) that did not.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The medical records of 62 critically ill dogs and cats with AKI that received fenoldopam were reviewed. Presenting clinical signs, physical examination findings, and primary and secondary disease processes were identified in all patients. The mean number of days on fenoldopam was 1.5 days (range 0.3-4.0 days) for dogs and 1.9 days (range 1.0-4.0 days) for cats. Eleven of 28 (39%) dogs survived to discharge and 13 of 34 (38%) of the cats survived to discharge. Of the animals in the group receiving fenoldopam that died, the majority (84%) were euthanized. Potential adverse reactions were evaluated, with hypotension being the most commonly encountered adverse effect (7% of fenoldopam group [FG] dogs and 23% of FG cats). When compared with patients with AKI that did not receive fenoldopam, no significant differences were found between the groups with regards to survival, length of hospital stay, adverse effects, or changes in creatinine, BUN, or sodium concentrations except that patients receiving fenoldopam were significantly more likely to have received other renally active medications.

CONCLUSIONS

In this study of patients with AKI, fenoldopam administration at 0.8 μg/kg/min in dogs and 0.5 μg/kg/min in cats appeared relatively safe but was not associated with improvement in survival to discharge, length of hospital stay, or improvement in renal biochemical parameters when compared to patients with AKI not receiving fenoldopam.

Feline acute kidney injury: 2. Approach to diagnosis, treatment and prognosis

PRACTICAL RELEVANCE

Feline acute kidney injury (AKI) is a commonly recognized problem in small animal practice that requires prompt diagnosis and directed therapy. There are many treatment methods with which practitioners should be familiar, including medical options, surgical interventions and renal replacement therapy (dialysis). It is important to know which option is most appropriate for each cause and stage of AKI to deliver the most effective therapy.

CLINICAL CHALLENGES

AKI can cause vague clinical signs, but a vast array of life-threatening sequelae. Rapid recognition of potential complications and knowledge of treatment options is imperative for successful management. Feline patients also require an understanding of their unique physiology as it relates to the therapeutic plan.

AUDIENCE

This two-part review article is directed at small animal practitioners as well as specialists. Part 2 discusses the diagnosis of AKI in cats using physical examination findings, clinicopathologic results and imaging modalities. The treatment of AKI and its sequelae is also reviewed, with information on recent advances in this area.

EVIDENCE BASE

While there is very limited data comparing the outcomes of various treatment options, there is literature addressing the use of several medications, as well as renal replacement therapy, in cats.

Acute kidney injury in dogs and cats

The term acute kidney injury (AKI) has replaced the historical term acute renal failure for renal damage occurring over a short period of time (hours to days) because it is thought to better describe the pathophysiologic changes and duration of the different phases of injury. There are many potential causes of AKI in dogs and cats, and the prognosis has been shown to vary with the cause as well as with therapy. This article reviews current concepts of the pathophysiology, causes, clinical presentation, approach to diagnosis, and medical management of AKI in dogs and cats.

Effects of administration of fluids and diuretics on glomerular filtration rate, renal blood flow, and urine output in healthy awake cats

OBJECTIVES

To determine effects of commonly used diuretic treatments on glomerular filtration rate (GFR), renal blood flow (RBF), and urine output (UO) and compare 2 methods of GFR measurement in healthy awake cats.

ANIMALS

8 healthy cats.

PROCEDURE

In a randomized crossover design, cats were randomly allocated to 4 groups: control; IV administration of fluids; IV administration of fluids and mannitol; and IV administration of fluids, dopamine, and furosemide. Inulin and para-aminohippuric acid were used for determination of plasma clearance for GFR and RBF, respectively. Plasma clearance of technetium-Tc-99m-diethylenetriaminepentacetic acid (99mTc-DTPA) was also used for GFR determination.

RESULTS

Furosemide-dopamine induced the largest UO, compared with other groups. Both mannitol and fluid therapy increased RBF, compared with the control group. Mannitol, and not fluid therapy, increased RBF, compared with furosemide-dopamine. There were significant differences in GFR values calculated from 99mTc-DTPA and inulin clearances between the 2 groups. In all groups, use of 99mTc-DTPA caused underestimation of GFR, compared with use of inulin.

CONCLUSIONS AND CLINICAL RELEVANCE

In healthy awake cats, administration of furosemide-dopamine did not increase GFR or RBF despite increased UO. Fluid therapy and fluid therapy plus mannitol improved RBF. Determination of GFR by use of 99mTc-DTPA cannot always be substituted for inulin clearance when accurate measurement is required.

Urinary tract emergencies

A review of common emergencies of the urinary system is presented, with a focus on initial stabilization and treatment. Urethral obstruction, uroperitoneum, and acute renal failure are discussed.