Epinephrine Deteriorates Pulmonary Gas Exchange in a Rat Model of Bupivacaine-Induced Cardiotoxicity: A Threshold Dose of Epinephrine.

BACKGROUND AND OBJECTIVE: The study goal was to compare the effect of epinephrine in different doses on pulmonary gas exchange in a rat model of bupivacaine-induced cardiac depression. METHODS: Twenty-four adult male Sprague-Dawley rats were divided into 4 groups (n = 6), and each group received a bupivacaine infusion (2.5 mg/kg per minute, 6 minutes) via the left femoral vein to induce cardiac depression. At the end of the bupivacaine infusion, each group was immediately given either isotonic sodium chloride solution (normal saline; NS group), 5-µg/kg epinephrine (Epi5 group), 10-µg/kg epinephrine (Epi10 group), or 20 µg/kg epinephrine (Epi20 group). Left atrial pressures were monitored for 20 minutes after epinephrine was administered (as was the NS group). Arterial blood gas analyses were performed before bupivacaine infusion and at the end of the 20-minute monitoring period. RESULTS: The Epi10 and Epi20 groups had lower pH (P = 0.02 and P < 0.001, respectively) and PaO2 (P = 0.049 and P < 0.001, respectively), and a higher PaCO2 (P < 0.001 and P < 0.001, respectively) compared with the NS group. There were no statistical differences between the Epi5 and NS groups in pH, PaCO2, or PaO2. Left atrial systolic pressure was higher in the Epi10 group (P = 0.002) and the Epi20 group (P < 0.001) within 2 minutes of epinephrine administration. There was no statistical difference between the Epi5 and NS groups in left atrial systolic pressure. CONCLUSION: A single injection of 10 µg/kg epinephrine or greater was associated with deterioration of pulmonary gas exchange in our rat model of bupivacaine induced cardiac depression.

[Evaluation of safety and anesthetic effect for ultrasound-guided cervical plexus block].

OBJECTIVE: To observe the influences upon the degree of diaphragmatic excursion during deep cervical plexus block at the third cervical vertebra (C3) and compare the safety and anesthetic effect of modified cervical plexus block by ultrasonic guidance and blocking of cervical plexus at one point. METHODS: Part I: 30 patients of ASA (American society of anesthesiologists) I-II scheduled for thyroid surgery were selected for bilateral cervical plexus block at C3 and bilateral skin nerve branches via ultrasonic guidance. Diaphragmatic excursion was recorded. Part II: 80 patients of ASAI-II scheduled for thyroid surgery were randomly divided into 2 groups: experimental group (Group U) and control group (Group C). In Group U, modified cervical plexus block was used to fix both sides of C3 and skin nerve branches. The anesthetic mixture with 2% lidocaine and 0.75% ropivacaine was injected. And anesthetic effects and complications were detected. In control group, traditional one-point method for blocking cervical plexus was employed. RESULTS: High-frequency Doppler sonography could clearly visualize important neck structures and precisely guide the injection of mixture to the transverse process of C3. Diaphragmatic excursion decreased significantly at 15 and 30 min post-blocking (P < 0.05). And no paralysis of diaphragmatic muscle occurred. Hoverer 3 cases had partial diaphragmatic paralysis. Both blood pressure and heart rate increased significantly post-blocking in both groups (P < 0.05 or 0.01). In comparison with Group C, the range of blood pressure was notably lower at 10 and 20 min in Group U. And heart rate was notably lower at 5, 10, 20 and 30 min (P < 0.05 or 0.01). Furthermore the onset time of skin nerve branches was significantly shorter in Group U (P < 0.01). And the anesthetic effect score was better than that in Group C (P < 0.01). The incidence of complications, such as hoarseness, was significantly lower in Group U (12 cases in Group C but none in Group U, P < 0.01) and Horner's syndrome (2 cases in Group C). The number of cases requiring hypotensor and heart rate control drug was significantly smaller in Group U than that in Group C (P < 0.01). CONCLUSION: The improving effect of ultrasound-guided cervical plexus block upon the degree of diaphragmatic movement is within the compensatory range of body. In comparison with the traditional one-point blocking of cervical plexus, the modified cervical plexus block with ultrasonic guidance offers better anesthetic effects, fewer complications and convenient anesthetic localization. Thus it may be clinically applicable.

[Effects of lipid emulsion on hemodynamics and pharmacokinetics of mongrel dogs with bupivacaine-induced cardiac depression].

OBJECTIVE: To investigate the effects of Intralipid injection on hemodynamics and pharmacodynamics of mongrel dogs with bupivacaine-induced cardiac depression. METHODS: Fourteen dogs were randomly divided into Intralipid injection group (the experiment group) and normal saline group (the control group). 0.5% bupivacaine was administrated at a constant rate until the mean arterial pressure (MAP) decreased to 60% of the basic value. Intralipid injection was administered in the experiment group. The hemodynamic parameters were recorded and blood samples were taken from femoral artery at 0, 5, 10, 15, 20, 30, 45, 60, 90, 120, 180, 240 min after stopping bupivacaine infusion for determination of plasma concentration by HPLC. The pharmacokinetic parameters were calculated by Drug and Statistics soft version 2.0. RESULTS: After the treatment of Intralipid injection, MAP, CO, HR increased significantly, compared to those of the control group (P < 0.05). The AUC(o-t) was (192 +/- 34)mg x L(-1) x min(-1) versus (271 +/- 81) mg x L(-1) x min(-1) and the AUC(0-infinity) was (231 +/- 62) mg x L(-1) x min(-1) versus (368 +/- 140) mg x L(-1) x min(-1) in the experiment group and the control group respectively. Vz (4.5 +/- 1.1 L/kg versus 3.3 +/- 0.9 L/kg) of bupivacaine in the experiment group was significantly higher than that in the control group (P < 0.05). CONCLUSION: Intravenous infusion of Intralipid have beneficial effects on the hemodynamics of mongrel dogs with bupivacaine-induced cardiac depression. One of the mechanism of the beneficial effects was probably that Intralipid injection increases the apparent volume of bupivacaine distribution and that decreases blood concentration. [Key words]

[Optimal dose of local anesthetic mixture in ultrasound-guided infraclavicular brachial plexus block via coracoid approach: analysis of 160 cases].

OBJECTIVE: To investigate the optimal dose of local anesthetic mixture in ultrasound-guided infraclavicular brachial plexus block via coracoid approach. METHODS: 160 patients scheduled for surgery of the hand or forearm were randomly divided into 4 equal groups (Groups A, B, C, and D). To receive 8, 7, 6, or 5 ml of anesthetic mixture of 0.75% ropivacaine and 2% lidocaine for radial nerve, axillary nerve, median nerve, ulnar nerve, median cutaneous nerve of arm, median antebrachial cutaneous nerve, and lateral antebrachial cutaneous nerve respectively ultrasound-guided infraclavicular brachial plexus block via coracoid approach. The time for anesthesia taking effect, anesthesia maintenance time, and quality of sensory block were observed. RESULTS: Anesthesia took effect about 4 minutes after injection in these 4 groups without significant differences among then (all P > 0.05). The good analgesic effect rates of Groups A, B, and C were all 100%, all significantly higher than that of Group D (87.5%, P = 0.027). The block maintenance times of Groups A, B, and C were (377 +/- 111) min, (369 +/- 135) min, and (351 +/- 112) min respectively, all significantly longer than that of Group D [(296 +/- 101) min, P = 0.024]. No anesthesia-related complication was found in these 4 groups. CONCLUSION: Ultrasound-guided infraclavicular brachial plexus block via coracoid approach can reduce the volume of local anesthetic mixture. The dose of 6 ml local anesthetic mixture for each nerve fascicle, totally 18 ml, provides good analgesic effect and does not seem to affect the time for anesthesia taking effect.

[Comparison of lumbar plexus block and epidural block for elderly patients undergoing intertrochanteric femoral fracture surgery].

OBJECTIVE: To compare the anesthesia efficacy, hemodynamics, recovery of passage of gas by anus and bladder function in elderly patients with operation of intertrochanteric femoral fracture with epidural or lumbar plexus block. METHODS: Sixty patients with intertrochanteric femoral fracture, aged 65-97, were randomly divided into 3 equal groups: lumbar plexus group (Group A, undergoing posterior lumbar plexus block) and epidural group (Group B, undergoing epidural block at L(1-2) interspace). The block onset time, anesthesia efficacy, transfusion amount during operation, blood pressure and heart rate change 1 h after anesthesia, and recovery after anesthesia were observed. RESULTS: The block onset time on femoral nerve, lateral cutaneous nerve of thigh, obturator nerve, and saphenous nerve of Group A were (2.7 +/- 2.0) min, (3.1 +/- 3.4) min, (3.5 +/- 3.3) min, and (3.7 +/- 3.1) min respectively, all significantly shorter than those of Group B [(13.5 +/- 2.1) min, (13.5 +/- 2.1) min, (13.5 +/- 2.1) min, and (13.5 +/- 2.1) min respectively, all P < 0.01]. The duration of postoperative analgesia of Group A was (420 +/- 152) min, significantly longer than that of Group B [(204 +/- 44) min, P < 0.05]. There were no significant differences in the change of blood pressure and heart rate between these 2 groups. The blood pressure decreased significantly 10 - 60 min after anesthesia in Group B, and remained stable in Group A. The transfusion amount of Group A was (773 +/- 353) ml, significantly fewer than that in Group B [(1483 +/- 444) ml, P < 0.01]. Passage of gas by anus started (1.1 +/- 0.6) h after operation in Group A, a time significantly shorter than that in Group B (5.9 +/- 1.2) h, P < 0.01). Urinary retention was seen in 8 patients of Group B, however, no patient in Group A showed incidence of urinary retention (P < 0.01). Forty-eight patients, 20 in Group A and 28 in Group B got excellent anesthesia effect, and 12 of them, 10 in Group A and 2 in Group B, got relatively good anesthesia (P < 0.05). CONCLUSION: Both lumbar plexus block and epidural block provide satisfactory anesthetic efficacy for operation of intertrochanteric femoral fracture in elderly patients. Epidural block provide better efficacy, and lumbar plexus block shows faster recovery of digestive system and urinary system after operation.

[Determination of median effective dose of lidocaine to control the onset time of sciatic nerve blockade using up-and-down sequential method].

OBJECTIVE: To determine the median effective dose (ED50) of 2% lidocaine to control the onset time of sciatic nerve blockade within 15 min by using 2% lidocaine and 0.75% ropivacaine 10 ml. METHODS: Fifty patients underwent sciatic nerve blockade and lumbar plexus blockade for operations of unilateral lower extremities. 2% lidocaine was allocated into 7 ranks in geometric proportion between 4.2 ml and 12.5 ml. The observed index was the blockade onset time less than 15 min of the lateral cutaneous branch of sural nerve, fibular nerve, and rami calcanei medicales nervi tibialis. The ED50 of 2% lidocaine was determined respectively in the patients in which dorsiflexion or plantarflexion was elicited by in up-and-down sequential method. RESULTS: Combined with ropivacaine, the values of ED50 of 2% lidocaine in the patients in which dorsiflexion and plantarflexion were elicited by up-and-down sequential method were 6.88 ml and 6.19 ml respectively when the onset time of blockade of sciatic nerve was within the range of 15 min. CONCLUSION: The dosage to elicit plantarflexion is similar to the dosage to elicit dorsiflexion in sciatic nerve blockade.

[Efficacy of axillary approach brachial plexus blocking by ultrasound-guided four points via one-puncture technique].

OBJECTIVE: To investigate the clinical effects and safety of the technique of axillary approach brachial plexus blocking by ultrasound-guided four points via one-puncture. METHODS: Eighty patients scheduled for elective operation were randomly divided into 2 equal groups to undergo axillary approach brachial plexus blocking by ultrasound-guided four points via one-puncture technique (Group U) or nerve stimulator-guided brachial plexus blocking (Group N). The main branches of brachial plexus (radial, median, ulnar, and musculocutaneous nerves) were localized by ultrasound-guided or nerve stimulator-guided techniques. In Group U 8 ml of mixed anesthetic solution containing isovolumetric 0.75% ropivacaine and 2% lidocaine was injected into the 4 main branches of brachial plexus, with a total volume of 32 ml. The ultrasonic manifestations of the brachial plexus and its surrounding tissues were observed. The values of diameter and depth of the 4 nerves and the distance of the musculocutaneous nerve to the midpoint of axillary artery were measured. The manipulation time, onset time, maintaining time, efficacy of blocking, and incidence of complication were recorded. RESULTS: The manipulation time of Group U was 5.2 +/- 2.1 min, significantly shorter than that of Group N (14.6 +/- 3.2 min, P = 0.000), The onset times of the median, radial, and ulnar nerves of Group U were 3.3 +/- 1.9 min, 3.0 +/- 1.7 min, and 3.4 +/- 1.9 min respectively, all significantly shorter than those of Group N (4.6 +/- 2.0 min, 7.3 +/- 7.4 min, and 6.4 +/- 6.1 min respectively, P < 0.01 or P < 0.05). The anesthetic success rate of Group U was 100%, significantly higher than that of Group N (77.5%, P = 0.005). The rate of accidental puncture to blood vessel of Group U was 0, significantly lower than that of Group N (40%, P = 0.000). CONCLUSION: With significantly higher anesthetic success rate, shorter manipulation time and onset time, and lower complication rate, the technique of axillary approach brachial plexus blocking by ultrasound-guided four points via one-puncture is a safe and reliable blocking method in comparison with the nerve stimulator-guided method.