Optimum dose of normal saline for preloading epidural space required to prevent injury to blood vessel by epidural catheter placement for caesarean section / 中华麻醉学杂志

ABSTRACT

Objective To determine the optimum dose of normal saline (NS) for preloading epidural space required to prevent the injury to blood vessel by epidural catheter placement for caesarean section.Methods Two hundred ASA Ⅰ or Ⅱ parturients with a single baby at full term in vertex presentation,aged 24-35 yr,weighing 63-78 kg,scheduled for caesarean section under continuous epidural anesthesia,were randomly divided into4 groups (n-50 each)control group (group Ⅰ),NS2 ml group (group Ⅱ),NS5 ml group (group Ⅲ)and NS 10 ml group (group Ⅳ).The epidural puncture was performed at L2-3 interspace with a Tuohy needle attached to a 5 ml syringe.Loss of resistance was used to identify the epidural space.In group C no fluid was injected into the epidural space before insertion of the catheter,while in groups Ⅱ,Ⅲ and Ⅳ NS 2,5 and 10 ml were injected into the epidural space before the catheter insertion respectively.After a test dose of 3 ml 1.5％ lidocaine,0.75％ ropivacaine 10-20 ml was administered through the epidural catheter.MAP and HR were recorded before epidural puncture (T0),at 10 and 20 min after the end of epidural administration (T1.2),and at the end of surgery (T3).The number of patients in whom blood or blood tinted fluid was withdrawn from the epidural catheter was recorded.The amount of ropivacaine consumed was recorded.The upper level of anesthesia was measured by pin-prick and the degree of motor block was assessed using modified Bromagc scale at T2.Results The hemodynamic parameters were in the normal range in the four groups.MAP was significantly lower at T2,the upper level of anesthesia was significantly higher,and the degree of motor block was significantly smaller in group Ⅳ than in groups Ⅰ,Ⅱ and Ⅲ (P ＜ 0.05).There was no significant difference in MAP among groups Ⅰ,Ⅱ and Ⅲ (P ＞ 0.05).There was no significant difference in HR and the amount of ropivacaine consumed among the four groups (P ＞ 0.05).The number of patients in whom blood or blood tinted fluid was withdrawn fiom epidural catheter was significantly smaller in groups Ⅲ and Ⅳ compared with groups Ⅰ and Ⅱ (P ＜ 0.05).Conclusion Preloading the epidural space with NS 5 ml can prevent the occurrence of injury to blood vessel induced by insertion of epidural catheter with no influence on the efficacy of anesthesia and NS 5 ml is the optimum dose.