Effect of vertebral canal opening on pharmacodynamics of local anesthesia in epidural space / 中国中西医结合急救杂志

ABSTRACT

Objective To investigate the pharmacodynamic changes in local epidural anesthetic and correlated factors before and after epidural space opening during vertebral canal surgery. Methods 120 patients who underwent vertebral canal operation under epidural anesthesia from January 2008 to December 2010 in Anyang City People's Hospital in Henan Provincial were selected. A self control study method was applied to persistently monitor the patients' vital signs〔heart rate variance(HRV),mean arterial pressure(MAP),heart rate(HR),saturation of blood oxygen(SpO2)〕,and the subjective manifestations of patients,the appraisal of surgeon about the surgical local situation(the degree of skeletal muscle relaxation,neural reflex,the ooze blood and so on),the changes in movement (primarily Aαnerve fiber),feeling(primarily Aδnerve fiber),skin temperature(primarily non-myelinated nerve fiber C)within the scope of anesthesia,the dosage of local anesthetic used and the incidence of local anesthetic toxicity were record before and after epidural cavity opening. Results There were no statistical significant differences in vital signs before and after epidural cavity opening in this group of patients. After the opening of epidural space,the local use of anesthetic dosage and the incidence of local anesthetic toxicity were obviously higher than those before the opening〔lidocaine(mg/h)911.23±15.58 vs. 460.19±10.82,ropivacaine(mg/h)13.35±0.19 vs. 5.24±0.17, the incidence of local anesthetic toxicity67.5%vs. 1.2%,all P<0.01〕,the anesthesia plane(skeletal muscle laxity, feeling,skin temperature)was poorer than that before the opening of epidural space〔the anesthetic plane before the opening was(4.0±1.7),(10.7±1.5),(12.0±1.6)segments respectively,after opening was(2.0±1.8),(10.2±1.3), (12.6±1.9)segments〕,after epidural space opening,the correlations among the three planes(movement sensation disjointed)were worse than those before the epidural space opening(good). Conclusion The opening of vertebral canal can change the action of local epidural anesthetic,decrease its therapeutic effect and increase its incidence of toxicity,therefore,it is necessary to further discuss the application of epidural anesthesia in vertebral canal operation.