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]