Plasma Concentration and Cardiovascular Effects of Lidocaine during Continuous Epidural Administration in Dogs Anesthetized with Isoflurane

Abstract

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...

Effects of thoracolumbar epidural anesthesia with lidocaine on the systemic hemodynamics and hepatic blood flow in propofol anesthetized dogs

“…However, it appeared that the liver gradually degraded the lidocaine and maintained its blood concentration at a constant level. Further, the serum lidocaine concentration in this experiment was lower than that in the previous experiments with dogs administered with 2% lidocaine in the epidural space (2.4 μg/ml at 30 min) [27]. Propofol used in TIVA is degraded by hepatic cytochrome P450 (CYP) 3A4 [12] and lidocaine by CYP 3A4 or 1A2 [22], but propofol is not known to inhibit the lidocaine metabolism [20].…”

Comparison of the effects of lidocaine and fentanyl in epidural anesthesia in dogs

“…Naganobu et al (14) reported that epidural administration of morphine and fentanyl in dogs anesthetized with sevofl urane induced statistically signifi cant decreases in diastolic and mean arterial blood pressure values. A study conducted by Sakonju (15) investigated the effects of continuous epidural administration of lidocaine (3 mg/kg) in dogs anesthetized with isofl urane and they found that HR and MAP signifi cantly decreased immediately after epidural administration of lidocaine. Vnuk et al (16) showed that epidural administration of lidocaine (4 mg/kg) in dogs under isofl urane anesthesia had no signifi cant changes on HR and MAP.…”

Período de latência, progressão e duração do bloqueio da anestesia epidural com lidocaína, bupivacaína ou sua associação em cães

“…Essa diminuição, embora clinicamente insignificante (Tab. 1), pode ser creditada à lidocaína, fato esse também observado porSakonju et al (2011), que, após a administração de lidocaína 2% no volume de 0,2mL/kg pela via epidural, verificaram diminuição da PA em cães.…”