The Analgesic Effects of Intrathecal Pregabalin in Rat Formalin Tests: Comparison between Pre- and Post-treatment / 대한마취과학회지

BACKGROUND: Pregabalin is an analog of gamma aminobutyric acid, and selectively interacts with the alpha-2-delta subunit of the voltage dependent calcium channels. The aims of this study were to investigate the analgesic effects of intrathecal pregabalin in rat formalin tests and to compare between the pre-treatment and post-treatment group. METHODS: All experimental animals were randomly divided into pre- and post-treatment groups. In pre-treatment groups, pregabalin (0.003g, 0.01g, 0.03g, 0.1g, n = 6 at each group) was administered through the intrathecal catheter 10 min prior to formalin injection. In post-treatment groups, pregabalin (0.01g, 0.03g, 0.1g, 0.3g, n = 6 at each group) was administered through the catheter 10 min after formalin injection. Formalin (50 ml, 5%) was injected in the left hind paw. We counted the number of flinching as a pain behavior for 60 min to quantify the nociceptive response. RESULTS: The withdrawal responses which were represented by flinching count, were decreased dose dependently in the phase 2, in all groups (pre-treatment and post-treatment group), while there were less analgesic effects and ceiling effects in the phase 1. There was more significant decreasing flinching number in the pre-treatment group than that in the post-treatment group. CONCLUSIONS: Intrathecal pregabalin has preemptive analgesic effect and may be useful in the management of inflammation induced hyperalgesia.

During Inhalation Anesthesia with Sevoflurane Using LMA, Spontaneous Breathing is Feasible / 대한마취과학회지

BACKGROUND: Sevoflurane is used as an anesthetic agent is now commonly. Several studies have reported on the use of sevoflurane in spontaneous breathing patients. However none of these studies focused on spontaneous breathing under sevoflurane anesthesia with a laryngeal mask airway (LMA). The purpose of the present study was to assess the feasibility of spontaneous breathing during inhalation anesthesia using sevoflurane with an LMA. METHODS: We studied 50 patients undergoing elective upper/lower extremity surgery in which muscle relaxation was not required. All patients received thiopental sodium 5.5 mg/kg after glycopyrrolate 0.004 mg/kg premedication. They were allowed to breathe spontaneously after the insertion of an LMA under sevoflurane anesthesia. Ventilation was measured before induction and ventilatory variables of 3-4% sevoflurane were measured during spontaneous ventilation. Arterial blood gas analysis was also performed in both phases. RESULTS: During spontaneous breathing under sevoflurane anesthesia with LMA, tidal volume (TV) significantly reduced and respiration rate (RR) increased versus resting ventilation (P < 0.05). But, minute volume (MV) was not significantly different. PaCO2, HCO3-, total CO2, BE were all significantly increased (P < 0.05). CONCLUSIONS: It was concluded that spontaneous breathing can be maintained during clinical depth sevoflurane inhalation anesthesia in patients without a cardiopulmonary abnormality.

Effect of Enflurane on the Baroreflex Control of Heart Rate in Decerebrate Rats

Volatile anesthetics alter the arterial baroreflex (BRX) but its mechanisms are poorly understood. This study was designed to determine the effect of 1 and 2 minimal alveolar concentrations (MAC) of enflurane on the BRX parameters in unanesthetized brain stem-intact and decerebrate rats. Under enflurane anesthesia, the femoral artery and both femoral vein were catheterized for pressor (phenylephrine) and depressor (nitroprusside) drug delivery and continuous blood pressure measurements. Decerebration was performed at midcollicular level. BRX tests were performed in 3 time periods; before enflurane (conscious brain-intact), during 1 or 2 MAC enflurane exposure 1 hour after a sham operation or a decerebration operation, and 2 hours after the termination of enflurane (zero enflurane). Mean arterial pressure (MAP) and heart rate (HR) were fitted to a sigmoid logistic equation, the Boltzman equation. The curve of best fit was obtained with a computer program. 1 MAC and 2 MAC of enflurane shifted MAP-HR baroreflex curves to the left in the all groups and significantly attenuated the baroreflex range. The slope of conscious intact period and zero enflurane period of each group did not change significantly, but during the enflurane period the slope was significantly lowered. Enflurane depressed the baroreflex sensitivity (slope) and the HR range in a similar dose-dependant manner in both brain stem-intact and decerebrate rats. Such results draw into question whether the suprapontine sites contribute to enflurane's actions on cardiovascular autonomic regulation.