ABSTRACT. The cardiovascular effects of continuous epidural administration (CEA) of lidocaine were investigated in anesthetized dogs. Loading epidural injections of 2, 4, or 6 mg/kg of lidocaine were followed by CEA with 1, 2, or 3 mg/kg/hr lidocaine, respectively, for 2 hr under 2.0% isoflurane anesthesia. Heart rate, direct blood pressure, cardiac index, and stroke volume decreased dose-dependently during CEA, whereas systemic vascular resistance did not significantly differ with dose, and no characteristic changes were observed in any groups. Plasma lidocaine concentration reached a steady state during CEA and increased in a dose-dependent manner. Circulatory suppression caused by lidocaine CEA was not attributable to peripheral vasodilation, but rather to the direct cardiac action of systemic lidocaine absorption from the peridural space.KEY WORDS: canine, continuous epidural administration, lidocaine.J. Vet. Med. Sci. 73(3): 393-398, 2011 Perioperative pain is often managed using local anesthetics, the main side effects of which depend on blood concentrations and occur through cardiovascular and central nervous system toxicities [14]. Blood concentrations of local anesthetics in vivo are influenced by absorption and elimination rates, as well as by dose [18]. Therefore, the absorption characteristics of drugs at administration sites should be considered when investigating the safety of local anesthetics.Local epidural anesthesia induces peripheral vasodilation due to sympathetic block of the spinal cord segments, and it reduces cardiac output and blood pressure due to a decrease in cardiac perfusion [2,13]. Local anesthetics are absorbed after epidural administration via the venous plexus or lymphatic system into the systemic circulation, and they reduce conduction velocity and contractile force via direct cardiac toxicity [8,13]. Therefore, cardiovascular safety after epidural administration of local anesthetics should be investigated from the viewpoint of changes in peripheral circulation in addition to direct cardiac toxicity, depending on blood levels.Veterinarians frequently induce epidural analgesia using lidocaine [9]. However, repeated or continuous administration is required to sustain analgesia, because lidocaine is short acting. A safe dosage regimen for continuous epidural administration (CEA) of lidocaine in humans has been established [5,17]. However, little is understood about the safety of continuous epidural lidocaine administration in dogs.The present study investigated the cardiovascular effects of various lidocaine dosages in dogs anesthetized with isoflurane. Plasma concentrations during lidocaine CEA were simultaneously measured in order to estimate its impact on the central nervous system. The Institutional Animal Care and Use Committee of Kitasato University approved all protocols in the present study, which were repeated in 7 clinically healthy beagles (4 males and 3 females; body weight, 9.0-12.0 kg) at intervals of at least 7 days. All animals were deprived of food and water fo...

A parametric magnetic reproducing head consists of a reproducing head and a timevariable capacitor connected in parallel. It is a flux response-type head. The amplitude of the output voltage is dependent of the signal frequency and proportional to the signal field. In this paper, mpgnetic tape recotdet configuration and chpracteristics for low-frequency signals with this head are described. It is also reported that this recorder is suitable for long-time recording and short-time reproduction. It is clear that it has excellent characteristics at a low-frequency range and is very useful for the application of long-time recording and short-time reproduction of an ultralow-frequency signal.

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