Feasibility Of Continuous Infusion Of 1.5% Lidocaine By Target Controlled Equipment For High Epidural Anesthesia

Objective: To evaluate the feasibility of continuous infusion of 1.5% lidocaine by target controlled equipment for high epidural anesthesia in patients undergoing modified radical mastectomy and provide a reference for further study in the administration way of epidural anesthesia.Methods: ASAâ… orâ…¡female Patients, aged 30-64 yr, weighing 45-80 kg, with the height of 150-175 cm, scheduled for elective modified radical mastectomy, were enrolled in this study. The patients had no liver and renal dysfunction, no history of circulatory or respiratory system disease and could finish the measurement of respiratory muscle function. The patients were randomly divided into 2 groups (n=24 each): routine administration group (group R) and continuous infusion by target controlled equipment group (group A). The upper and lower spread of sensory block was determined bilaterally by the pinprick method. The sensory block was determined 20 min after 1.5% lidocaine was given, and the patients whose sensory block scope could satisfy the operation were included in the study. The day before surgery, the patients were told how to use the RMS-â… , and then the baseline value were measured. The pressure-time curve was drawn. All patients were unpremedicated, and after arriving at the operation room, a cannula was inserted into a peripheral vein. Epidural anesthesia was performed at either T2-T3 or T3-T4 interspace with the patient in the right lateral position. The needle was successfully inserted into the epidural space if the resistance was lost, the negative pressure occurred. The catheter was inserted 3-4 cm beyond the tip of the needle in a cephalad direction, and then taped to the skin to avoid kinking or slipping. If no blood and cerebral spinal fluid were drawn out through the catheter, and normal saline 2 ml was then injected into the catheter to identify whether it was unobstructed or not. In group R, a test dose of 1.5% lidocaine 5ml was injected into the epidural space, 5 min later, 1.5% lidocaine 9 ml was administered, 1.5% lidocaine 5 ml was added at 20 min of the infusion and 1.5% lidocaine 5 ml was then given every 30 min. In group A, after the catheter was connected to the Base primea (Fresenius kabi,Germany), epidural anesthesia was induced and maintained with 1.5% lidocaine administrated by target controlled equipment (remifentanil, minto mode). Parameters were modulated according to the anesthesia effect. If heart rate (HR)<50 bpm, atropine 0.5 mg was injected i.v. If systolic blood pressure (SBP)<80 mm Hg or was below 30% of baseline, ephedrine 10 mg was injected i.v. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), electrocardiograph (ECG), and pulse oxygen saturation (SpO₂) was monitored throughout the operation, and SBP, DBP, MAP, HR and SpO₂ was recorded before administration (T_0min), and at 5 min (T_{5 min}), 10 min (T_{10 min}), 15 min (T_{15 min}), 20 min (T_{20 min}), 25 min (T_{25 min}), 30 min (T_{30 min}), 35 min (T_{35 min}), 40 min (T_{40 min}), 45 min (T_{45 min}), 50 min (T_{50 min}), 55 min (T_{55 min}), 60 min (T_{60 min}), 65 min (T_{65 min}), 70 min (T_{70 min}), 75 min (T_{75 min}) after administration. Maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), maximum sustained inspiratory pressure (SIPmax), duration of inspiration (T_i), and duration of expiration (T_e) were measured at T_0min, T_{5 min}, T_{10 min}, T_{15 min}, T_{20 min}, T_{25 min}, T_{30 min}, T_{35 min}, T_{45 min}, T_{55 min}, T_{65 min}, T75 min, and Ti /( Ti + Te)% were also calculated. The number of patients who had bradycardia, hypotention, and dyspnea were recorded.Results:1 There were no significant differences between the two groups with respect to age, body weight, height, the duration of operation and the total dose of 1.5% lidocaine used (P>0.05).2 Hemodynamic indexes: HR was decreased by 4.0±0.5%, 10.0±1.3%, 14.6±1.6%, 10.0±1.4% and 16.2±0.6%, 16.2±1.2%, 18.9±3.1%, 17.5±2.3% in group A and R respectively at T_{20 min}, T_{25 min}, T_{30 min}, and T_{35 min}. The decreasing degree of HR were significantly lower in group A than in group R at T_{20 min}, T_{25 min}, T_{30 min}, T_{35 min} (P<0.05), but HR was significantly higher in group R than in group A at T_{50 min} (P<0.05). SBP was decreased by 13.5±2.0%, 17.6±1.9%, 20.1±1.4%, 19.3±1.2% and 20.1±2.3%, 22.6±2.0%, 24.3±1.3%, 23.3±1.3% in group A and R respectively at T_{20 min}, T_{25 min}, T_{30 min}, and T_{35 min} compared with the baseline value, and the decreasing degree of SBP were significantly lower in group A than in group R at T_{20 min}, T_{25 min}, T_{30 min}, T_{35 min} (P<0.05).3 Respiratory mechanics indexes: MIP was decreased by 37±6%, 43±5%, 31±4% and 53±7%, 61±5%, 45±5% in group A and R respectively at T_{30 min}, T_{35 min}, and T45 min compared with the baseline value. The decreasing degree of MIP at T_{30 min}, T_{35 min}, T45 min, and T_{65 min} were significantly lower in group A than in group R (P<0.05). MEP at T_{25 min}, T_{30 min}, T_{35 min}, and T45 min was decreased by 50±4%, 57±4%, 59±3%, 56±3% and 64.2±5%, 70±5%, 70±4%, 68±4% in group A and R respectively compared with the baseline value. The decreasing degree of MEP at T_{25 min}, T_{30 min}, T_{35 min}, and T45 min were significantly lower in group A than in group R (P<0.05). SIPmax at T_{30 min}, T_{35 min}, and T_{65 min} was decreased by 43±3%, 48±3%, 26±5% and 62±4%, 64±4%, 43±5% in group A and R respectively compared with the baseline value. The decreasing degree of SIPmax at T_{30 min}, T_{35 min}, and T_{65 min} were significantly lower in group A than in group R (P<0.05). The Ti /( Ti + Te)% at T_{35 min}, T45 min, T55 min, and T_{65 min} were significantly smaller in group A than in group R (P<0.05).4 There were no significant differences between the two groups with respect to dyspnea. The incidence of bradycardia and hypotention were significantly lower in group A than in group R(P<0.05). Conclusions: High epidural anesthesia can be achieved by modulating some parameters of the target controlled equipment, and this way of administration has a small influence on hemodynamic and respiratory mechanics, and provides a more stable anesthesia process. This study provides a new thought of the study in administration way of epidural anesthesia.