ABSTRACT. The aim of this study was to examine renal hemodynamics at the hypovolemic and recovery phases in two different hypovolemic shock models using Doppler ultrasonography, and to compare this with systemic hemodynamics. In experiment 1, the hypovolemic phase was induced in 6 mongrel dogs by removing arterial blood at 30 ml/kg for 60 min. In the recovery phase, this blood was reinfused at 30 ml/kg over 60 min. In experiment 2, hypovolemia was induced in 12 beagle dogs by rapid blood removal until blood pressure decreased to 40 mmHg and was maintained at this pressure for 30 min. Six of the dogs were then infused with 20 ml/kg hydroxyethyl starch over 5 min, and the other 6 were infused with 60 ml/kg lactated Ringer's solution also over 5 min. Parameters for systemic and renal hemodynamics were measured by using a polygraph and the Doppler method, respectively. The decrease of diastolic blood flow, resulted in an increase of vessel resistance, and was detected in the hypovolemic kidney by the Doppler method. The rapid and large volume infusion of resuscitation fluids was effective for the recovery of both systemic circulation and renal blood flow, however this induced an increase of kidney vessel resistance, a result of the autoregulation mechanism of the kidney. The changes in these parameters at the main renal artery and interlobar artery were similar. MATERIALS AND METHODSExperimental animals: Six adult mongrel dogs (4 males and 2 females; 2-9 years old), weighing 9-13 kg were used in experiment 1. Twelve adult beagles (7 males and 5 females; 2-7 years old), weighing 7-12 kg were used in experiment 2. These dogs were evaluated as clinically normal.Anesthesia: After induction of the general anesthesia with atropine sulfate (0.03 mg/kg, i.m.), flunitrazepam (0.03 mg/ kg, i.v.) and thiamylal sodium (approximately 15 mg/kg, i.v.), the dogs were endotracheally intubated, and anesthesia was maintained with isoflurane. The breathing movements were arrested using vecronium bromide (0.05 mg/kg, i.v., every 30 min), and were changed to mechanical ventilation with a ventilator (KV-2N, Kimura Ikakiki Co., Tokyo, Japan) at an inspired oxygen concentration (FIO 2 ) of 1.0 and a frequency of 16 breaths/min to achieve an arterial carbon dioxide tension (PaCO 2 ) of 35-45 mmHg. Heparin (500 U/kg, i.v.) was given every 30 min.Hemorrhagic shock model: Experiment 1: Hypovolemia was induced in 6 mongrel dogs during a 60 min period by removing arterial blood at 30 ml/kg/hr into a CPD blood transfusion bag (SC-207, TERUMO Co., Tokyo, Japan). The dogs were then observed over a 60-min period in the hypovolemic state. After that, blood was reinfused from the sterile bags at 30 ml/kg/hr for 60 min. Following reinfusion these dogs were again observed for 60 min.Experiment 2: Hypovolemia was induced in 12 beagles by removing blood until the mean arterial pressure (MAP)The primary causes of acute renal failure can be categorized as ischemic or nephrotoxic [4]. Prerenal azotemia is relatively common, particularly in dogs that have und...

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