Renal Effects of Medetomidine in Isoflurane-Anesthetized Dogs with Special Reference to Its Diuretic Action

Abstract

ABSTRACT. Renal effects of the selective α 2 -adrenoceptor agonist, medetomidine, were investigated in anesthetized dogs. Animals were administered medetomidine 20 and 40 µg/kg intravenously (IV) and 80 µg/kg intramuscularly (IM) or 1 ml of saline IV. Urine and blood samples were collected before and at 30, 60, 90 and 120 min following medetomidine injection. Mean arterial blood pressure (MABP), renal blood flow (RBF), glomerular filtration rate (GFR), urine volume (U v ), urine osmolality (U osm ), free water clearance (C H2O ), fractional clearance of sodium (F Na ), plasma osmolality (P osm ), plasma glucose levels and plasma antidiuretic hormone (ADH) concentrations were measured. The results showed that IV administration of medetomidine initially increased MABP 5-15 min followed by long-lasting decrease. The initial hypertension was not observed after IM administration, which was accompanied by a more profound hypotensive effects. RBF, GFR, U v , C H2O increased after IV injection and decreased after IM. Medetomidine increased FNa and Posm and decreased U osm . Plasma glucose levels initially increased and subsequently decreased. Plasma ADH concentration was decreased by IV injection but increased by IM administration. Our data imply that: 1) IV administration of medetomidine at dose rates of 20 and 40 µg/kg results in profound diuresis up to 2 hr; 2) Suppression of ADH release from the CNS is one of the mechanisms of medetomidine-induced diuresis although it may not be the principal one. KEY WORDS: anesthesia, canine, isoflurane, medetomidine and renal function.

Comparison of pancreatic and renal blood flow in a canine tachycardia-induced cardiomyopathy model

“…To maintain the blood PAH concentration, continuous intravenous infusion of PAH diluted in lactated Ringer's solution was carried out during the experiment at a rate of 3 ml/kg/min (PAH administration rate, 0.4 mg/kg/min). After a PAH equilibration time of 30 min, all of the urine in the bladder was collected via a previously placed 6 Fr urinary balloon catheter to set the baseline condition[36]. Urine samples were subsequently collected three times at 15-min intervals.…”

Antagonistic Effects of Atipamezole, Yohimbine and Prazosin on Medetomidine-Induced Diuresis in Healthy Cats

“…Medetomidine has been shown to induce diuresis in rats [18] and dogs [3, 19, 24, 26]. Recently, our study showed that both medetomidine and xylazine induced profound diuresis in cats by decreasing water reabsorption in the kidneys [16].…”

Effects of Tepoxalin and Medetomidine on Glomerular Filtration Rate in Dogs

“…The alpha 2 -adrenoceptor agonist, medetomidine, can cause profound peripheral vasoconstriction via activation of alpha 2B adrenergic receptors [23,26]. In the kidney, alpha 2 -adrenoceptor agonist-mediated vasoconstriction occurs preferentially on efferent arterioles and may result in increases in GFR [35], although the effect is dependant upon administration route and dose [32]. Administration of medetomidine 50 µg/kg, IV decreases renal uptake of technetium 99m-labeled diethylenetriamine pentaacetic acid ( 99m Tc-DTPA) for 15 min after administration in dogs [12] and 10 µg/kg, IV of dexmedetomidine decreased renal blood flow by 30% in dogs anesthetized with chloralose and urethane or fentanyl and halothane [23].…”

“…In human thoracotomy patients, administration of a dexmedetomidine infusion was shown to enhance renal function, including indices of glomerular filtration as well as urine flow rate [10]. The varied effects on renal blood flow and GRF exhibited by the alpha 2 -adrenoceptor agonists may be due to the biphasic cardiovascular effects of these drugs that are often reported in several species [23,26,31,32]. An initial hypertension is observed immediately following IV bolus administration of alpha 2 -adrenoceptor agonists and is thought to be due to activation of peripheral alpha 2B adrenergic receptors [23].…”