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[The equipotency of ropivacaine, bupivacaine and etidocaine].

Ropivacaine, congenerate to bupivacaine and mepivacaine has been widely studied in laboratory animals, but there have been few investigations of its efficacy in human epidural anesthesia and peripheral nerve blocks. The aim of this study was to compare the three long-acting local anesthetics (bupivacaine 0.75%, ropivacaine 1% and etidocaine 1%) and to try, with reference to previous studies, to make some statement about the equipotency of ropivacaine relative to bupivacaine and etidocaine. METHODS. In a double blind randomized study, epidural anesthesia was carried out with 20 ml bupivacaine 0.75% (n = 24) and ropivacaine 1% (n = 21). Following this study epidural anesthesia was carried out with 20 ml etidocaine 1% (n = 20) in an open study. Patients with ASA I or II were enrolled in the study. All patients were scheduled for varicose vein stripping. Male and female patients aged 18-70 years and weighing 50-100 kg were included in the study. Patients were all placed in a sitting position, after which the epidural space was identified by the "loss of resistance" technique and a midline approach, at the L-3/4 interspace. Injections of 3 ml of the local anesthetic were given, followed by the remainder of the local anesthetic at 10 ml/min 1 min later. Following injection patients were immediately positioned supine. Analgesia was determined by the pin-prick method and motor blockade was assessed according to the Bromage scale. Heart rate and blood pressure were monitored until 3 h after injection. RESULTS. The latency of analgesia for the first blocked segment (T 12 for bupivacaine and ropivacaine and L-1 for etidocaine) was 6.0 min for bupivacaine 0.75, 5.5 min for ropivacaine 1%, and 5.2 min for etidocaine 1%, and the highest thoracic dermatome (T 5 for bupivacaine, T 4 for ropivacaine and T 7 for etidocaine) was reached after 24 +/- 10, 26 +/- 9, and 30 +/- 18 min for bupivacaine, ropivacaine, and etidocaine, respectively. The duration of sensory anesthesia at the T 10 dermatomal level was 257 +/- 102, 278 +/- 67, and 191 +/- 86 min for bupivacaine, ropivacaine, and etidocaine, respectively. The two-segment regression time was 199 +/- 80 min for bupivacaine, 201 +/- 52 min for ropivacaine, and 174 +/- 81 min for etidocaine. The total duration of sensory block was 340 +/- 103 min for bupivacaine, 428 +/- 65 min for ropivacaine and 223 +/- 62 min for etidocaine, respectively. In the ropivacaine and bupivacaine groups sensory anesthesia was considered adequate for surgery in all cases but one in each group; in the etidocaine group, however 60% of the patients showed inadequate analgesia and all these patients (12/20) required additional analgesics. Bupivacaine achieved an average of motor block 2.1, ropivacaine 2.3, and etidocaine 2.4. CONCLUSION. The results of this study indicate that ropivacaine is an effective local anesthetic agent. Its potency is about equal to that of bupivacaine and much higher than that of etidocaine...

Acetanilides↗

Effects of extradural block: comparison of the properties, circulatory effects and pharmacokinetics of etidocaine and bupivacaine.

Five healthy, unmedicated male volunteers, aged 19-25 yr, participated in a double-blind, crossover study. Each subject received, on separate occasions and via a catheter placed at L2, 1.5% etiodocaine HCl20 ml with adrenaline 5 mug/ml, or 0.75% bupivacaine HCl 20 ml with adrenaline 5 mug/ml for extradural analgesia. In addition, in order to calculate the absorption rate of the local anaesthetic agent, each subject received on two further occasions etidocaine HCl 75 mg and bupivacaine HCl 75 mg respectively by i.v. infusion, over a period of 10 min. Spread of sensory analgesia to four segments above and below the site of injection was faster with etidocaine (13 +/- 3 min) (mean +/- SD) than with bupivacaine (22 +/- 8 min). Two-segment regression occurred later for bupivacaine (260 +/- 57 min) than for etidocaine (180 +/- 96 min). Caudal spread of analgesia was more extensive with etidocaine than with bupivacaine. The onset of motor blockade tended to be faster with etidocaine (5.8 +/- 3.0 min), than with bupivacaine (10.0 +/- 3.5 min); regression of motor blockade by one unit was longer with etidocaine (306 +/- 103 min) than bupivacaine (238 +/- 75 min). Sudomotor block occurred earlier with etidocaine (4.0 +/- 2.1 min) than bupivacaine (13.7 +/- 4.8 min). Significant changes in cardiac stroke work and stroke volume occurred. For etidocaine these measurements remained below control values for 120-210 min after injection. The mean maximum arterial plasma concentration of etidocaine was 1.52 +/- 0.64 mug/ml, at 14 +/- 2 min and of bupivacaine was 1.35 +/- 0.63 mug/ml, achieved at 20 +/- 4 min. The systemic absorption of both drugs occurred in a biphasic pattern with a fast and slow half-life of 0.3 and approximately 8 h respectively.

Acetanilides↗

Block of fast axonal transport in vitro by the local anesthetics dibucaine and etidocaine.

Other investigators have shown that procaine, lidocaine and tetracaine block fast axonal transport in vitro. The present study shows that dibucaine and etidocaine also exhibit this effect. The biological material used consists of the 8th and 9th dorsal root ganglia and spinal nerves of the bullfrog; in vitro fast transport of [3H]leucine-labeled proteins is quantitated by liquid scintillation counting. Exposure of spinal nerves to dibucaine reduces the quantity of 3H-proteins which is transported to a ligature by 72% at 0.5 mM and by greater than 90% at a 1 mM concentration; since 1 mM tetracaine reduces it by 64%, dibucaine is approximately twice as potent as tetracaine at inhibiting transport. Etidocaine is less potent than tetracaine at blocking transport since 2 mM etidocaine reduces the quantity 3H-proteins at a ligature by less than 10% and 2 mM tetracaine reduces it by greater than 90%. Etidocaine is, however, more potent than lidocaine since 10 mM etidocaine reduces the quantity of 3H-proteins present at a ligature by 64% and 10 mM lidocaine reduces it by less than 10%; when tested at the same pH (6.2) as the 10 mM etidocaine solution, 2 mM tetracaine reduces radioactivity at the ligature by 49%. The ratio of concentration required to block transport (by greater than 90%) to minimum anesthetic concentration is approximately 3 for tetracaine; but this ratio is much higher for etidocaine, since etidocaine is as potent as tetracaine as a local anesthetic but approximately 5 times less potent at inhibiting fast axonal transport.

Acetanilides↗

Epidural anaesthesia with mixtures of bupivacaine-lidocaine and etidocaine-lidocaine.

The mixtures of 0.5% bupivacaine- 1% lidocaine and 1% etidocaine- 1% lidocaine were used in a double-blind manner for lumbar epidural anaesthesia in 48 patients undergoing prostatectomy in order to study whether these mixtures speed up the onset of analgesia, shorten the long motor block, motor block, or improve the quality of analgesia caused by bupivacaine or etidocaine alone. The mixture of bupivacaine-lidocaine caused an analgesia with a somewhat faster onset, similar duration and markedly shorter motor block than bupivacaine alone. The sensory block produced by the mixture of etidocaine-lidocaine tended to begin more slowly and had a distinctly shorter duration, as was the motor block, as compared to the block caused by etidocaine alone. The analgesia was complete in all 12 patients who received bupivacaine and in 11/12 patients who received the mixture of bupivacaine-lidocaine, but 6/12 patients anaesthetized with etidocaine and 5/12 patients with the mixture of etidocaine-lidocaine experienced considerable visceral pain during the operation. The results suggest that the mixture of bupivacaine-lidocaine produces a block with somewhat better properties than bupivacaine alone, but the mixture of etidocaine-lidocaine does not offer any advantages as compared to etidocaine alone, except the shorter motor block.

Acetanilides↗

Bupivacaine compared with etidocaine for vaginal delivery.

A comparison of 0.5 percent etidocaine with 0.25 and 0.5 percent bupivacaine, using continuous (intermittent) caudal block in 60 vaginal deliveries, showed the latter two solutions to be the agents of choice. All solutions contained a final concentration of 1:2000,000 epihephrine. In 40 parturients given either 0.25 or 0.5 percent bupivacaine, all had pain relief after the initial dose, while 5 of 20 given etidocaine required a refill dose within 30 to 50 minutes for complete pain relief. The duration of action of the initial dose with both concentrations of bupivacaine was longer than that of etidocaine. The degree of motor blockade with 0.5 percent etidocaine was greater than with 0.5 percent bupivacaine, and with 0.5 percent concentrations of either etidocaine or bupivacaine was greater than with 0.25 percent bupivacaine. The duration of motor blockade of 0.5 percent etidocaine and bupivacaine was comparable. The duration of motor blockade of the 0.25 percent concentration of bupivacaine was shorter than with the 0.5 percent concentration of both etidocaine and bupivacaine; and with both bupivacaine concentrations the duration of sensory anesthesia in the extremities was longer than motor blockade; with etidocaine, the opposite occurred.

Acetanilides↗

Effects of peridural block: V. Properties, circulatory effects, and blood levels of etidocaine and lidocaine.

Ten healthy, unpremedicated, male volunteers, aged 21-33 years, were given 20 ml 1 per cent etidocaine with 5 mug/ml epinephrine for peridural analgesia via a catheter placed L2. On a different occasion they were given 20 ml 2 per cent lidocaine with 5 mug/ml epinephrine in the same manner. Initial onset of sensory analgesia to pin prick was faster for etidocaine (7 min) than for lidocaine (9 min). Analgesia lasted significantly longer after etidocaine with respect to both two-segment regression (177 plus or minus SE min vs. 114 plus or minus 8 min) and total duration (379 plus or minus 22 min vs. 190 plus or minus 8 min). Onset of maximal motor blockade was significantly faster with etidocaine (15.4 plus or minus 2.5 min) than with lidocaine (31.7 plus or minus 3.3 min); blockade lasted longer with etidocaine (331 plus or minus 25 min vs. 167 plus or minus 13 min). Changes in mean arterial pressure cardiac output, central venous pressure, limb blood flows, total peripheral resistance, and stroke volume were similar with the two drugs, although those after etidocaine were more prolonged as a result of the longer blockade. Mean maximum arterial concentrations of etidocaine were 0.96 plus or minus 0.05 SE mug/ml (plasma) and 0.55 plus or minus 0.03 mug/ml (whold blood), achieved at 17 plus or minus 2 min. Mean maximum arterial concentrations of lidocaine were 2.22 plus or minus 0.09 mug/ml (plasma) and 1.85 plus or minus mug/ml (whold blood), achieved at 24 plus or minus 2 min. No sign of central toxicity was observed with either drug, although subjects receiving lidocaine tended to sleep, which was not the case with etidocaine. Hematologic screening, blood chemistries, and urinalyses performed 24 hours before and after each study showed no abnormality.

Acetanilides↗

Plasma protein binding of etidocaine during pregnancy and labour.

Preliminary studies of the ultrafiltration method for measuring the extent of plasma protein binding of etidocaine showed that etidocaine binding was both pH and concentration dependent. Etidocaine (1 microgram/ml) was found to bind avidly to a physiological concentration (74 mg/dl) of alpha 1-acid glycoprotein (alpha 1-AGP) (7.23 +/- 0.64%, mean +/- SD, unbound). In vitro investigation of etidocaine binding in plasma obtained from blood bank donors and from 19 pregnant women prior to induction of labour, during early labour, mid-labour and delivery showed no difference in etidocaine binding (10.3 +/- 3.3%, 7.06 +/- 2.66%, 8.15 +/- 2.57%, 7.84 +/- 3.74% and 9.28 +/- 6.06% unbound respectively). There was a significant increase in the mean plasma total free fatty acid (FFA) concentration from pre-labour (0.535 +/- 0.240 mM) to delivery (0.948 +/- 0.28 mM), while plasma albumin and beta-lipoprotein concentrations remained constant. Alpha 1-Acid glycoprotein concentration tended to increase slightly from pre-labour to early labour (p less than 0.1) but was still within the normal physiological range. There was no correlation between etidocaine binding ratio and the concentrations of FFA or plasma proteins except for a poor correlation with the alpha 1-AGP concentration (r = 0.361, p less than 0.05). Storage of plasma and inadequate control of plasma pH during ultrafiltration appeared to give spurious binding values. These studies with the extensively bound basic drug etidocaine suggest that unlike many acidic drugs which are bound predominantly to serum albumin, the binding of alpha 1-AGP - bound basic drugs may be unaffected by pregnancy and labour.

Acetanilides↗

Anesthetic efficacy and heart rate effects of the intraosseous injection of 1.5% etidocaine (1:200,000 epinephrine) after an inferior alveolar nerve block.

OBJECTIVE: The purpose of this study was to determine the anesthetic efficacy and heart rate effects of an intraosseous (IO) injection of 1.5% etidocaine with 1:200,000 epinephrine after an inferior alveolar nerve block. STUDY DESIGN: In a repeated-measures designed study, 48 subjects randomly received 2 combinations of injections at 2 separate appointments. The combinations were an inferior alveolar nerve (IAN) block (with 3% mepivacaine) + IO injection with 1.8 mL of 1.5% etidocaine hydrochloride containing 1:200,000 epinephrine, and an IAN + mock IO injection. The first molar was blindly tested with a pulp tester at 2-minute cycles for 60 minutes after the injection. Anesthesia was considered successful when 2 consecutive 80 readings (no subject response) were obtained. Heart rate (pulse rate) was measured with a pulse oximeter. RESULTS: Lip numbness occurred in 100% of the subjects with both the techniques. For the first molar, anesthetic success for the IAN + mock IO and the IAN + IO etidocaine hydrochloride groups, respectively, were 81% and 100%. The differences were significant (P <.05) when the IAN + IO etidocaine hydrochloride technique was compared with the IAN + mock IO. A mean increase in heart rate of 32 beats/min occurred in 90% of the subjects with the IO injection of the etidocaine hydrochloride solution. In 89% of these subjects, the heart rate returned to within 5 beats of baseline values 4 minutes or less after solution deposition. CONCLUSIONS: The IO injection of 1.8 mL of 1.5% etidocaine hydrochloride with 1:200,000 epinephrine, when used to augment an inferior alveolar nerve block, significantly increased anesthetic success in the first molar. The majority of subjects receiving the IO injection of the etidocaine hydrochloride solution had a transient increase in heart rate.

Adult↗

Circadian phase dependent acute toxicity and pharmacokinetics of etidocaine in serum and brain of mice.

The aim of this study was to investigate the possible influence of the time of administration on etidocaine acute toxicity and kinetics in mice. Different groups of adult male NMRI mice maintained under controlled environmental conditions (lights on 06.00-18.00) were injected at one of the following times: 10.00, 16.00, 19.00, 22.00, 01.00 and 04.00 h with four doses of etidocaine at each time point to establish the acute toxicity (LD 50). To assess chronokinetics, a single 40 mg kg-1 i.p. dose of etidocaine was given to adult male NMRI mice at four fixed times: 10.00, 16.00, 22.00 and 04.00 h. Etidocaine serum levels were determined by GLC. The data showed significant 24 h variations of the Cmax only (highest value = 9.64 +/- 1.31 micrograms mL-1 at 10.00 P less than 0.05; amplitude, (maximum-minimum) mean x 100 = 84%) Vd, (amplitude = 59.7%), alpha and beta phase elimination half-lives (amplitude = 52 and 35%, respectively), clearance (amplitude = 23%) and AUC infinity 0 (amplitude = 22%) were not found to be significantly time dependent. Etidocaine kinetics in brain were determined similarly; a significant temporal variation was found for the elimination half life (amplitude, 161.9%) and AUC (amplitude, 133.2%) but not for Cmax. These data demonstrate a temporal pattern of etidocaine kinetics similar to those reported previously for other local anaesthetic agents, bupivacaine and mepivacaine. The temporal changes in etidocaine induced acute toxicity may result in part from its chronokinetic changes.

Acetanilides↗

Motor and sensory blockade after epidural injection of mepivacaine, bupivacaine, and etidocaine--a double-blind study.

In a double-blind study of epidural anesthesia, 30 young volunteers were given either 2% mepivacaine (400 mg), 0.5% bupivacaine (100 mg), or 1.5% etidocaine (300 mg), all solutions containing epinephrine (1:200,000). The spread of analgesia was equal in the groups, whereas the longest duration was noted in the etidocaine and bupivacaine groups. With use of a method for determining muscle force, motor blockade during anesthesia was recorded quantitatively for hip flexion, knee extension, and plantar flexion of the big toe. Onset of motor blockade was significantly more rapid with etidocaine than with bupivacaine and mepivacaine. All subjects given etidocaine developed complete motor blockade, but with the other local anesthetics 5%-33% of the initial muscle force remained. The least motor blockade was found in the L5-S2 segment (plantar flexion of the big toe). The duration of maximal motor blockade varied between 60 min (mepivacaine) and 360 min (etidocaine). With each of the three local anesthetics, motor function returned simultaneously in the three muscle groups tested. Complete restoration of muscle function occurred significantly later for etidocaine (600 min) than for bupivacaine (360 min) and mepivacaine (180 min). With etidocaine, the motor blockade outlasted the sensory blockade by 150 min. The Bromage scale corresponded to the motor blockade only during the first half of the regression phase. Not until 1-3 h after attainment of Bromage grade 0 was the muscle force of all movements restored (90% of control values).

Acetanilides↗

Pharmacokinetics and metabolism of the anilide local anaesthetics in neonates. 11 Etidocaine.

The urinary elimination of etidocaine and several of its metabolites was investigated in neonates whose mothers had received one or more doses of etidocaine during labour. The urine collection period ranged among the neonates from 21.4 to 47.0 h post-partum. The total amounts of etidocaine and its metabolites recovered in neonatal urine represented a mean of 0.12% of the maternal dose. Some differences in the pattern of urinary metabolites were observed between neonates and adults. Mean half-life of elimination of etidocaine calculated from sigma-minus plots of the neonatal urinary data was 6.42 h. This is greater than that previously reported following intravenous administration of etidocaine to adults (2.6 h). The slower rate of elimination in neonates is probably due to an increased neonatal volume of distribution since there is evidence to show that etidocaine is extensively metabolised by the neonate.

Acetanilides↗

Hyaluronidase improves regional ophthalmic anaesthesia with etidocaine.

The effect of adding hyaluronidase to regional ophthalmic anaesthesia with etidocaine 1.5% was examined. Two studies were performed in a double-blind fashion. In Study #1, 70 patients were given peribulbar anaesthesia with etidocaine either with or without hyaluronidase (7.5 IU.ml-1) using a standard intraorbital injection and separate lid injections. The block was supplemented as needed. Lower intraorbital volumes (6.4 +/- 2.2 ml vs 8.2 +/- 2.3 ml, P < 0.01) and improved scores for globe akinesia (P < 0.01), lid akinesia (P < 0.01) and analgesia (P < 0.05) were recorded in the hyaluronidase group than in the plain etidocaine group. In Study #2, 80 patients were randomized to receive etidocaine and hyaluronidase either at a concentration of 7.5 IU.ml-1 or 15 IU.ml-1 using a two-injection-site technique. No differences were noted in the volumes of local anaesthetics required or in the success rates between the two groups. It was concluded that the addition of hyaluronidase to etidocaine decreases the volume needed and improves the quality of block compared with plain etidocaine. Doubling the dose of hyaluronidase does not improve the effectiveness of block.

Aged↗

Postoperative analgesia after major shoulder surgery with interscalene brachial plexus blockade: etidocaine versus bupivacaine.

Postoperative pain is commonly treated with significant doses of narcotics, occasionally resulting in side effects including nausea, pruritus, and respiratory depression. One potential advantage of regional anesthesia is profound postoperative analgesia that reduces exposure to potent narcotics. To evaluate the efficacy of two long-acting local anesthetics, bupivacaine and etidocaine, in providing pain relief after major shoulder surgery, we randomized 20 patients to receive either bupivacaine or etidocaine for brachial plexus block as the primary anesthetic for shoulder surgery. Surgeons, patients, and the acute pain service were blinded as to drug selection. After the patient was sedated, an interscalene block was placed with the use of a nerve stimulator to facilitate proper needle placement. Forty milliliters of either 0.5% bupivacaine or 0.75% etidocaine containing 5 micrograms/mL epinephrine was injected into the brachial plexus sheath. An additional 8 mL of local anesthetic was administered for superficial cervical plexus blockade. Intraoperative sedation was accomplished with an intravenous infusion of methohexital as needed. After surgery, patients received a standard patient-controlled analgesia protocol providing incremental doses of morphine. The degree of postoperative analgesia resulting from residual local anesthetic effect was expressed as the time until first morphine requirement and the total dose of morphine required during the first 24 hours postoperatively. We found no statistically significant intergroup differences either in time of initial use of morphine or in the total dose of morphine required in the first 24 hours. Both etidocaine and bupivacaine provide prolonged analgesia after major shoulder surgery when injected into the brachial plexus. Bupivacaine, however, possesses significant cardiotoxicity and has a relatively delayed onset in peripheral neural blockade. Etidocaine is less cardiotoxic and also has a more rapid onset of effect. Thus etidocaine may be a preferable agent for interscalene block for major shoulder surgery.

Aged↗

[Elimination of the obturator reflex as a specific indication for dilute solutions of etidocaine. A study of the suitability of a local anesthetic for reflex elimination in the 3-in-1 block technic].

Direct stimulation of the obturator nerve by the electroresectoscope during transurethral resection of tumors in lateral bladder regions is possible under regional or general anaesthesia without muscle relaxation. The resulting obturator reflex may lead to perforation of the bladder. Two different regional techniques can be used to interrupt the obturator reflex arc: (1) separate block of the obturator nerve; or (2) the "3-in-1 block" (Winnie). In the present study elimination of the obturator reflex was carried out by "3-in-1 block" with diluted solutions of etidocaine in 55 cases. Venous plasma levels of etidocaine were measured in 9 patients after application of etidocaine 0.5% (unilateral 30 ml and bilateral 60 ml). Samples were taken 10, 20, 30, 40, 60, and 120 min after the "3-in-1 block". RESULTS. The "3-in-1 block" with diluted etidocaine produced excellent motor block of the obturator nerve. Clinical side effects did not occur. Plasma peak levels reached 2.2 micrograms/ml; the protein binding rate was 85%-95%. DISCUSSION. Elimination of the obturator reflex is the only specific motor nerve block in anesthesia. Diluted etidocaine solutions seem to be adequate: irrespective the technique used for eliminating the reflex, diluted etidocaine produces a good effect and permits a dosage reduction compared with other local anesthetics. It is possible to block the obturator nerve bilaterally by "3-in-1 block" or unilaterally by "3-in-1 block" in combination with epidural analgesia within the recommended dose limits.

Acetanilides↗

A double-blind crossover study comparing two doses of Duranest (etidocaine) 1% with a fixed dose of Sensorcaine (bupivacaine) 0.5% utilizing infiltration regional blocks of the fifth ray.

Two local anesthetics, Duranest 1% (etidocaine HCl) and Sensorcaine 0.5% (bupivacaine HCl), were tested against each other in dose-related blocks of the fifth ray. This study was conducted under double-blind cross-over conditions using 24 healthy volunteers. It was found that 4 ml. of either agent was sufficient to anesthetize the fifth ray area in all but 4.2% of the injections and 8 ml. of etidocaine always accomplished complete fifth ray anesthesia. Also, 4 ml. of etidocaine was found to have a more rapid onset and longer duration than the same volume of bupivacaine, 6.3 vs. 8.3 min. onset, and 487 vs. 449 min. duration, respectively. Pain and burning upon injection of either bupivacaine or etidocaine was encountered in 70% of the subjects tested. Residual pain was noted in some of the subjects given etidocaine after complete resolution of sensory anesthesia. Residual pain was not noted in any of the subjects given bupivacaine. Etidocaine was found to have a more rapid onset and a longer duration than bupivacaine or a lidocaine-bupivacaine mixture, and was thus found to be a superior agent in the subjects tested.

Acetanilides↗

A comparison of etidocaine and lidocaine for retrobulbar anesthesia.

In this double-blind study of retrobulbar block for cataract surgery, 62 patients scheduled for cataract surgery were randomly assigned to treatment with either (1) lidocaine 2% with epinephrine 1:200,000 (21 patients); (2) etidocaine 1% plain (20 patients); or (3) etidocaine 1% with epinephrine 1:200,000 (21 patients). The time of onset of sensory and motor block after administration of the three drugs was the same. The duration of motor nerve block produced by etidocaine plain and by etidocaine with epinephrine was considerably longer than that produced by lidocaine with epinephrine, and fewer patients reported postoperative pain after either etidocaine plain or etidocaine with epinephrine than after lidocaine with epinephrine.

Acetanilides↗

Hydrophobic membrane interaction of etidocaine, bupivacaine and 2-chloroprocaine. A spin and fluorescent probe study.

It has been suggested that local anesthetics may block sodium conductance through nervous membranes also by hydrophobic interaction, e.g., by expanding the membrane. Decreased anisotropy (fluidization) and depressed phase transition temperatures have been shown by relatively high local anesthetic concentrations. We studied the dose dependence of the effect of three clinically used local anesthetics, with different lipid solubility, on lipid fluidity parameters of four different model membranes. With stearic acid spin labels in dipalmitoyl lecithin vesicles etidocaine (1-5 mM) had the clearest fluidizing effect followed by bupivacaine (5 mM); 2-chloroprocaine was without effect on lipid fluidity. In synaptic plasma membranes a fluidizing effect near the hydrophilic part of the lipid bilayer was similar with etidocaine and bupivacaine (5-10 mM); 2-chloroprocaine had no effect. Bupivacaine at 125 and 250 muM had a small ordering effect, which was not seen at a more hydrophobic site of the membrane. Etidocaine had the strongest fluidizing effect at the latter site of the synaptic plasma membranes. In erythrocyte ghost membranes, probed by stearic acid spin labels near the hydrophilic end, none of local anesthetics affected fluidity at 24 degrees C, while at 37 degrees C etidocaine (1-5 mM) and bupivacaine (5 mM) had a fluidizing effect. Dimyristoyl lecithin vesicles were probed by cis- and trans-parinaric acid. Etidocaine and bupivacaine (5-10 mM) clearly depressed the phase transition temperature evaluated from fluorescence intensity scans. The effect was most marked with bupivacaine (1-10 mM) when cis-parinaric acid was used. While isolated mammalian nerves are blocked by local anesthetic concentrations below 100 muM, this study shows that the clinically used local anesthetics increase fluidity and depress phase transition temperature only at 10-100 times higher concentrations at physiological pH. This kind of hydrophobic membrane interaction may not be important for the nerve blocking effect.

Anesthetics, Local↗

Topical bupivacaine and etidocaine analgesia following fallopian tube banding.

The purpose of this study was to compare the effectiveness and safety of etidocaine and bupivacaine for postoperative analgesia after laparoscope sterilization. The study was performed in 22 healthy patients who received either one per cent etidocaine, 2 mg.kg-1, or bupivacaine 1.5 mg.kg-1 in a double-blind, randomized fashion. The local anaesthetic was dropped onto the fallopian tubes from uterus to fimbriae before tubal occlusion. To establish safety, blood concentrations of the parent drug and its metabolites were measured before application and at 1, 3, 6, 10, 15, 30, 60 and 120 min. The mean peak concentrations were 501.8 +/- 71.3 (SEM) for etidocaine with a range of 225 to 905 ng.ml-1. For bupivacaine, the mean peak concentration was 468 +/- 73.8 SEM with a range from 191 to 1005 ng.ml-1. The mean values are one eighth of the toxic convulsive dose for humans. Etidocaine was metabolized at a faster rate than bupivacaine with a rapid appearance of 2-amino-2'-butyroxylidide (ABX). The bupivacaine metabolite 2,6-pipecoloxylidide (PPX) was detected in low concentrations in the 60-minute samples. We conclude that the topical application of either etidocaine or bupivacaine is a safe procedure in the doses and concentrations used during general anaesthesia for laparoscopic tubal banding.

Abdominal Pain↗