Ropivacaine or 2% mepivacaine for lower limb peripheral nerve blocks. Study Group on Orthopedic Anesthesia of the Italian Society of Anesthesia, Analgesia, and Intensive Care.
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BACKGROUND: Intra- and postoperative clinical properties of sciatic-femoral nerve block performed with either ropivacaine at different concentrations or mepivacaine have been evaluated in a multicenter, randomized, blinded study. METHODS: Adult patients scheduled for foot and ankle surgery were randomized to receive combined sciatic-femoral nerve block with 225 mg of either 0.5% (n = 83), 0.75% (n = 87), or 1% (n = 86) ropivacaine, or with 500 mg of 2% mepivacaine (n = 84). A thigh tourniquet was used in all patients. Onset time, adequacy of surgical anesthesia, time to offset of nerve block, and time until first postoperative requirement for pain medication were evaluated by a blinded observer. RESULTS: The adequacy of nerve block was similar in the four treatment groups (the ratios between adequate:inadequate: failed blocks were 74:9:0 with 0.5% ropivacaine, 74:13:0 with 0.75% ropivacaine, 78:8:0 with 1% ropivacaine, and 72:12:0 with 2% mepivacaine). The onset of the block was slower with 0.5% ropivacaine than with other anesthetic solutions (P < 0.001). Regardless of the concentration, ropivacaine produced a longer motor blockade (10.5+/-3.8 h, 10.3+/-4.3 h, and 10.2+/-5.1 h with 0.5%, 0.75%, and 1% ropivacaine, respectively) than with mepivacaine (4.3+/-2.6 h; P < 0.001). The duration of postoperative analgesia was shorter after mepivacaine (5.1+/-2.7 h) than after ropivacaine (12.2+/-4.1 h, 14.3+/-5 h, and 14.5+/-3.4 h, with 0.5%, 0.75%, or 1% ropivacaine, respectively; P < 0.001). Pain relief after 0.5% ropivacaine was 14% shorter than 0.75% or 1% ropivacaine (P < 0.05). During the first 24 h after surgery, 30-37% of patients receiving ropivacaine required no analgesics compared with 10% of those receiving mepivacaine (P < 0.001). CONCLUSIONS: This study suggests that 0.75% ropivacaine is the most suitable choice of local anesthetic for combined sciatic-femoral nerve block, providing an onset similar to mepivacaine and prolonged postoperative analgesia. (+info)
The relationship between pH and concentrations of antioxidants and vasoconstrictors in local anesthetic solutions.
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pH affects the efficacy of local anesthetics by determining the percentage of the lipid-soluble base form of the anesthetic available for diffusion and penetration of the nerve sheath. The purpose of this study was to determine the relationship between pH and the concentrations of antioxidant and vasoconstrictor in dental local anesthetic solutions over real-time and after accelerated aging. Several batches of lidocaine and mepivacaine with vasoconstrictors were tested. Results showed that, immediately upon receipt from the manufacturers, three batches were below the USP pH limit (pH 3.3), and two batches contained less than the minimum limit of vasoconstrictors (90%). Real-time tests on batches that were within normal limits revealed that solutions were stable past 4 yr. Accelerated aging tests revealed a strong correlation between a decrease in pH and loss of antioxidants and vasoconstrictors. In conclusion, a quality batch of local anesthetic should remain efficacious long past the manufacturer's stated shelf life; a batch that is less than optimal, or one that is exposed to environmental stresses, will degrade rapidly, and efficacy may be affected by decreases in pH and loss of vasoconstrictor. pH may be an inexpensive, readily available screening test for efficacy of local anesthetics. (+info)
Dental anesthetic management of a patient with ventricular arrhythmias.
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During routine deep sedation for endodontic therapy, a dentist-anesthesiologist observed premature ventricular contractions (PVCs) on a 62-yr-old woman's electrocardiogram (EKG) tracing. The dentist was able to complete the root canal procedure under intravenous (i.v.) sedation without any problems. The dentist-anesthesiologist referred the patient for medical evaluation. She was found to be free from ischemic cardiac disease with normal ventricular function. The patient was cleared to continue her dental treatment with deep sedation. She subsequently continued to undergo dental treatment with deep intravenous sedation without incident, although her EKG exhibited frequent PVCs, up to 20 per minute, including couplets and episodes of trigeminy. This article will review indications for medical intervention, antiarrhythmic medications, and anesthetic interventions for perioperative PVCs. (+info)
No enhancement of sensory and motor blockade by neostigmine added to mepivacaine axillary plexus block.
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BACKGROUND: Intrathecal neostigmine induces analgesia but also several side effects. Recently, 500 microg neostigmine administered intraarticularly was shown to produce postoperative analgesia without side effects. The authors' goal was to determine whether 500 microg neostigmine added to mepivacaine in axillary plexus block prolongs postoperative analgesia. In addition, they wanted to determine the incidence of side effects in patients undergoing hand surgery. METHODS: Sixty-nine outpatients scheduled for carpal tunnel syndrome repair with axillary plexus block were randomly assigned to one of three groups that received saline solution in the axillary plexus and subcutaneously (group 1), 500 microg neostigmine in the axillary plexus and saline solution subcutaneously (group 2), or saline solution in the axillary plexus and 500 microg neostigmine subcutaneously (group 3). Sensory and motor block in the four hand nerve distributions were assessed every 5 min for 30 min The duration of the sensory and motor blocks were assessed after operation. Side effects were also recorded. RESULTS: Neostigmine had no effect on sensory and motor block in any of the four nerve distributions, nor did it increase the median duration of sensory block (215 min; range, 120-330 min) compared with group 1 (247 min; range, 190-287 min) or group 3 (236 min; range, 160-280 min). Motor block was slightly shorter (P = 0.045) in group 3 (190 min; range, 135-285 min) compared with group 1 (218 min; range, 145257 min) and group 2 (215 min; range, 105-343 min). Gastrointestinal side effects occurred in 30% of patients in both neostigmine groups but not in group 1 (P < 0.05). CONCLUSIONS: This study suggests that 500 microg neostigmine added to mepivacaine in axillary plexus block does not prolong postoperative sensory block, but it does cause a relatively high incidence of side effects. These two findings raise doubts about the use of neostigmine associated with local anesthetics for plexus neural block. (+info)
A new anterior approach to the sciatic nerve block.
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BACKGROUND: Although several anterior approaches to sciatic nerve block have been described, they are used infrequently. The authors describe a new anterior approach that allows access to the sciatic nerve with the patient in the supine position. METHOD: Sciatic nerve blocks were performed in 22 patients. A line was drawn between the inferior border of the anterosuperior iliac spine and the superior angle of the pubic symphysis tubercle. Next, a perpendicular line bisecting the initial line was drawn and extended 8 cm caudad. The needle was inserted perpendicularly to the skin, and the sciatic nerve was identified at a depth of 10.5 cm (9.5-13.5 cm; median and range) using a nerve stimulator and a 15-cm b-beveled insulated needle. After appropriate localization, either 30 ml mepivacaine, 1.5% (group 1 = knee arthroscopy; n = 16), or 15 ml mepivacaine, 1.5%, plus 15 ml ropivacaine, 0.75%, (group 2 = other procedures; n = 6) was injected. RESULTS: Appropriate landmarks were determined within 1.3 min (0.5-2.0 min). The sciatic nerve was identified in all patients within 2.5 min (1.2-5 min), starting from the beginning of the appropriate landmark determination to the stimulation of its common peroneal nerve component in 13 cases and its tibial nerve component in 9 cases. A complete sensory block in the distribution of both the common peroneal nerve component and the tibial nerve component was obtained within 15 min (5-30 min). A shorter onset was observed in patients who received mepivacaine alone compared with those who received a mixture of mepivacaine plus ropivacaine (10 min [5-25 min] vs. 20 min [10-30 min]; P < 0.05). Recovery time was 4.6 h (2.5-5.5 h) after mepivacaine administration. The addition of ropivacaine produced a block of a much longer duration 13.8 h (5.2-23.6 h); P < 0.05. No complications were observed. CONCLUSIONS: This approach represents an easy and reliable anterior technique for performing sciatic nerve blocks. (+info)
Effects of unilateral stellate ganglion block on the spectral characteristics of heart rate variability.
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The effect of unilateral stellate ganglion block on cardiovascular regulation remains controversial, so the present study used power spectral analysis of heart rate variability to investigate its effect on the autonomic neural control of the heart. In 20 young healthy volunteers (mean age: 25 years), heart rate variability was determined before and after unilateral stellate ganglion block (right side 11, left side 9) using 8 ml of 1% mepivacaine during supine rest. Using autoregressive spectrum analysis, power spectra were quantified by measuring the area in 3 frequency bands: high-frequency power (lnHF, parasympathetic influence) from 0.15 to 0.40 Hz, low-frequency power (lnLF, predominantly sympathetic influence) from 0.04 to 0.15 Hz, and total-frequency power (lnTF) less than 0.40 Hz. Right stellate ganglion block decreased not only the lnLF component from 6.55+/-0.84 to 5.77+/-0.47 but also the lnHF component from 4.40+/-0.95 to 3.42+/-1.12 (p<0.05). In contrast, left stellate ganglion block changed neither the lnLF nor the lnHF component. The lnTF component was also decreased significantly by right stellate ganglion block from 7.80+/-0.95 to 7.01+/-0.36 (p<0.05), but was unchanged following left stellate ganglion block. Neither right nor left stellate ganglion block induced any significant change in both the RR and corrected QT intervals. However, changes in the RR interval induced by right stellate ganglion block showed significant positive correlation with changes in lnHF (p<0.005) and lnTF (p<0.05). These results suggest that (1) autonomic innervation to the sinus node is mainly through the right-sided stellate ganglion, (2) pharmacological right-sided stellate ganglion block may attenuate not only sympathetic but also parasympathetic activity and (3) following right stellate ganglion block the decrease in both the sympathetic and parasympathetic influence on the sinus node may inconsistently counterbalance and change the RR interval. (+info)
Acute pain induces an instant increase in natural killer cell cytotoxicity in humans and this response is abolished by local anaesthesia.
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We have investigated the effect of pain without tissue injury on natural killer (NK) cell activity in peripheral blood in humans and the effect of local anaesthesia on the response. Ten subjects were investigated during two sessions. First, self-controlled painful electric stimulation was applied to abdominal skin for 30 min to an intensity of 8 on a visual analogue scale (0-10). Next, the electric intensity profile was reproduced during local anaesthesia (mepivacaine 10 mg ml-1 s.c. to a total dose of 2.5 mg kg-1). NK cell cytotoxicity was measured using a 4-h 51Cr-release assay against K562 target cells. NK cell activity increased from mean 22 (SEM 4)% (baseline) to 35 (6)% and 36 (5)% after 15 and 30 min of painful stimulation, respectively (P < 0.02). A simultaneous increase in the number of CD56+ cells in peripheral blood during pain was found. Stimulation after local anaesthesia did not change either NK cell activity or number. Parallel and significant increases in concentrations of plasma epinephrine and serum cortisol were observed. These changes were abolished by local anaesthesia. We conclude that acute severe pain without tissue injury markedly increased NK cell cytotoxicity. Local anaesthesia completely abolished this immunological and hormonal response. (+info)
Pain relief with intracameral mepivacaine during phacoemulsification.
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AIM: To assess the efficacy and safety of an intraoperative intracameral injection of mepivacaine, administered when patients experienced pain during the course of cataract surgery under topical anaesthesia. METHODS: This is a prospective placebo controlled double masked randomised clinical trial. 50 eyes were included; 25 receiving the active compound and 25 receiving placebo. Mepivacaine (2%, 0.4 ml) or placebo was administered intraoperatively under the iris of the patients who experienced pain during the course of phacoemulsification in spite of previous topical anaesthesia. Efficacy was evaluated by the patients themselves using a five point subjective pain rating scale, the Keele verbal pain chart. Safety was measured by assessing intraocular inflammation (clinical evaluation and laser flare meter), intraocular pressure, and endothelial cell count. RESULTS: The pain rating score significantly diminished after intracameral injection in the mepivacaine group (mean 3.0 (95% CI 2.6-3.4) v 0.8 (0.3-1.3), p<10(-4))) while remaining unchanged in the placebo group (2.9 (2.6-3.2) v 2.9 (2.5-3. 3)), the mean reduction in pain score being significantly different between the two groups (p<10(-4)). There was no indication of increased postoperative ocular inflammation, intraocular pressure change, or endothelial cell loss. CONCLUSIONS: These results suggest that it may not be necessary to systematically add intracameral anaesthesia with topical anaesthesia for cataract surgery. An intraoperative intracameral injection, performed only in patients who happen to suffer during surgery, is safe and effective. (+info)