Duration Of Motor Blockade Research Articles

Comparison of Motor Block of 1.0% Ropivacaine and 0.5% Bupivacaine in Epidural Anesthesia for Hip Arthroplasty Surgery

Background: The purpose of this study was to compare the onset time, degree and duration of motor block, and the satisfaction of surgeons of given single epidural injections of 1.0% ropivacaine and 0.5% bupivacaine in patients undergoing hip arthroplasty surgery. Methods: In a double-blind randomized study involving 20 patients, patients randomly received 12 ml of 1.0% ropivacaine or 0.5% bupivacaine at the L2-3 or L3-4 interspace. Parameters measured were the onset time, duration and degree of motor block, and the satisfaction of the surgeons. Results: Mean onset time of Bromage scale 2 was significantly slower with 1% ropivacaine (14.6 1.3 min) than with 0.5% bupivacaine (15.7 . 2.0 min). However, each frequency of motor blockade (Bromage scale 1, 2 and 3) with 1.0% ropivacaine (10, 8 and 7) was greater than that seen with 0.5% bupivacaine (7, 6 and 1). For scales 1 and 2, 1.0% ropivacaine had a significantly longer duration than 0.5% bupivacaine and the overall duration of motor blockade with 1.0% ropivacaine was longer than 0.5% bupivacaine. Motor block was in 80% achieved satisfactorily of the ropivacaine group and 60% of the bupivacaine group by the surgeons. Conclusions: In conclusion this study demonstrated that 1.0% ropivacaine provides a more rapid onset time, greater degree and longer duration of motor block without unacceptable side effects than 0.5% bupivacaine for hip arthroplasty surgery. From these results, it may suggest that 1.0% ropivacaine may be useful for lower extremity orthopedic surgery requiring good muscle relaxation.

Intrathecal Anesthesia: Ropivacaine Versus Bupivacaine

We compared intrathecal ropivacaine to bupivacaine in patients scheduled for transurethral resection of bladder or prostate. Doses of ropivacaine and bupivacaine were chosen according to a 3:2 ratio found to be equipotent in orthopedic surgery. One hundred patients were randomly assigned to blindly receive either 10 mg of isobaric bupivacaine (0.2%, n = 50) or 15 mg of isobaric ropivacaine (0.3%, n = 50) over 30 s through a 27-gauge Quincke needle at the L2-3 level in the sitting position. Onset and offset times for sensory and motor blockades and mean arterial blood pressure were recorded. Pain at surgical site requiring supplemental analgesics was recorded. Cephalad spread of sensory blocks was higher with bupivacaine (median level, cold T(4) and pinprick T(7)) than with ropivacaine (cold T(6) and pinprick T(9)) (P<0.001). Eight patients in Group Ropivacaine received IV alfentanil (P<0.01). Onset time (mean +/- SD) to T(10) anesthesia and offset time at L2 were not different (bupivacaine = 13 +/-8 min, 127+/-41 min; ropivacaine = 11+/-7 min, 105+/-29 min). Complete motor blockade occurred in 43 patients with bupivacaine and in 41 patients with ropivacaine (not significant). Total duration of motor blockade was not different. No difference in hemodynamic effects was detected between groups. No patient reported back pain. We conclude that 15 mg of intrathecal ropivacaine provided similar motor and hemodynamic effects but less potent anesthesia than 10 mg of bupivacaine for endoscopic urological surgery.

Ropivacaine

Ropivacaine is a long-acting, enantiomerically pure (S-enantiomer) amide local anaesthetic with a high pKa and low lipid solubility which blocks nerve fibres involved in pain transmission (Adelta and C fibres) to a greater degree than those controlling motor function (Abeta fibres). The drug was less cardiotoxic than equal concentrations of racemic bupivacaine but more so than lidocaine (lignocaine) in vitro and had a significantly higher threshold for CNS toxicity than racemic bupivacaine in healthy volunteers (mean maximum tolerated unbound arterial plasma concentrations were 0.56 and 0.3 mg/L, respectively). Extensive clinical data have shown that epidural ropivacaine 0.2% is effective for the initiation and maintenance of labour analgesia, and provides pain relief after abdominal or orthopaedic surgery especially when given in conjunction with opioids (coadministration with opioids may also allow for lower concentrations of ropivacaine to be used). The drug had efficacy generally similar to that of the same dose of bupivacaine with regard to pain relief but caused less motor blockade at low concentrations. Lumbar epidural administration of 20 to 30ml ropivacaine 0.5% provided anaesthesia of a similar quality to that achieved with bupivacaine 0.5% in women undergoing caesarean section, but the duration of motor blockade was shorter with ropivacaine. For lumbar epidural anaesthesia for lower limb or genitourinary surgery, comparative data suggest that higher concentrations of ropivacaine (0.75 or 1.0%) may be needed to provide the same sensory and motor blockade as bupivacaine 0.5 and 0.75%. In patients about to undergo upper limb surgery, 30 to 40ml ropivacaine 0.5% produced brachial plexus anaesthesia broadly similar to that achieved with equivalent volumes of bupivacaine 0.5%, although the time to onset of sensory block tended to be faster and the duration of motor block shorter with ropivacaine. Ropivacaine had an adverse event profile similar to that of bupivacaine in clinical trials. Several cases of CNS toxicity have been reported after inadvertent intravascular administration of ropivacaine, but only 1 case of cardiovascular toxicity has been reported to date. The outcome of these inadvertent intravascular administrations was favourable. Ropivacaine is a well tolerated regional anaesthetic with an efficacy broadly similar to that of bupivacaine. However, it may be a preferred option because of its reduced CNS and cardiotoxic potential and its lower propensity for motor block.

Sciatic nerve blockade with lipid-protein-sugar particles containing bupivacaine.

To assess the efficacy of lipid-protein-sugar particles (LPSPs) in providing prolonged duration local anesthesia by percutaneous injection. Bupivacaine-containing LPSPs were characterized and optimized in vitro. Male Sprague-Dawley rats were given sciatic nerve blocks with bupivacaine-containing LPSPs. Sensory and motor nerve blockade were measured in the hindpaw, as were contralateral functional deficits (a measure of systemic drug distribution). Poly(lactic-co-glycolic) acid (PLGA) microspheres were used as a reference. 10% (w/w) bupivacaine LPSPs (60% dipalmitoylphosphatidylcholine) were 4.4+/-0.39 microm in diameter, with a tap density of 0.11 +/-0.04 g/ml. These LPSPs and 50% (w/w) PLGA microspheres had comparable durations of sensory blockade (468+/-210 min vs. 706+/-344 min, p = 0.08), although the LPSPs produced a much lesser duration of motor blockade (508+/-258 min vs. 1062+/-456 min, p = 0.005). Systemic toxicity was minimal in both groups. LPSPs provide sensory blockade durations comparable to those from PLGA microspheres, with a smaller amount of drug loading. Motor blockade is shorter with LPSPs than with PLGA microspheres. LPSPs appear to be suitable for extended nerve blockade. Given their size and low density, they may be useful for topical anesthesia of the airway.

Randomized double-blind study of the clinical duration and efficacy of nesacaine-mpf 2% and 3% in peribulbar anesthesia

Purpose To compare 2 commercially available concentrations of Nesacaine®-MPF (2-chloroprocaine) to determine the time to onset of adequate motor blockade, the quality of surgical anesthesia, and the duration of motor blockade in the extraocular muscles after peribulbar anesthesia for cataract surgery. Setting Tampa Eye and Specialty Surgery Center, Tampa, Florida, USA. Methods This double-blind, randomized, single-center study comprised 40 patients scheduled to receive peribulbar anesthesia before cataract surgery. Patients were given 5 mL of Nesacaine-MPF 2% or 3% before surgery. Beginning at the end of the injection, assessments of ocular and eyelid movement were made every 2 minutes until adequate motor blockade was achieved or 25 minutes elapsed. Ocular assessments were made immediately after completion of surgery, 60 minutes after the end of the initial injection, and at 15 minute intervals thereafter until full recovery. Assessments of the quality of anesthesia achieved by the patient during surgery were made by the surgeon. Results The 3% solution provided significantly faster onset of surgical anesthesia than the 2% solution (mean 3.9 minutes ± 2.2 [SD] versus 6.0 ± 3.6 minutes) ( P = .02) but also required more time for recovery from anesthesia (98.9 ± 18.7 minutes versus 84.8 ± 20.6 minutes) ( P = .02). All patients had adequate surgical anesthesia. Duration of ocular motor function was brief enough so that all patients could be sent home without an eye patch. Both concentrations were safe for use in this procedure. Conclusion Both Nesacaine-MPF 2% and 3% produced safe and effective peribulbar anesthesia in all patients; however, the 3% solution provided better duration of clinical anesthesia.

This Month in Anesthesiology

This Month in Anesthesiology

Lumbosacral cerebrospinal fluid volume is the primary determinant of sensory block extent and duration during spinal anesthesia.

BACKGROUND. Injection of local anesthetic into cerebrospinal fluid (CSF) produces anesthesia of unpredictable extent and duration. Although many factors have been identified that affect the extent of spinal anesthesia, correlations are relatively poor and the extent of spread remains unpredictable. This study was designed to determine whether variability in the volume of lumbosacral CSF among individuals is a contributing factor in the variability of spinal anesthesia. Spinal anesthesia was administered to 10 healthy volunteers with 50 mg lidocaine in 7.5% dextrose. The technique was standardized to minimize variability in factors known to affect the distribution of spinal anesthesia. The extent of sensory anesthesia was assessed by pin-prick and by transcutaneous electrical stimulation. Motor blockade was assessed in the quadriceps and gastrocnemius muscles by force dynamometry. Duration of anesthesia was assessed by pinprick, transcutaneous electrical stimulation, and duration of motor blockade. Lumbosacral CSF volumes were calculated from low thoracic, lumbar, and sacral axial magnetic resonance images obtained at 8-mm increments. Volumes of CSF were correlated with measures of extent and duration of spinal anesthesia using the Kendall rank correlation test. Lumbosacral CSF volumes ranged from 42.7 to 81.1 ml. Volumes of CSF correlated with pin-prick assessments of peak sensory block height (P = 0.02) and duration of surgical anesthesia (as assessed by the duration of tolerance to transcutaneous electrical stimulation at the ankle (P < 0.05). Variability in lumbosacral CSF volume is the most important factor identified to date that contributes to the variability in the spread of spinal sensory anesthesia.

Inclusion complexation of amide-typed local anesthetics with β-cyclodextrin and its derivatives. III. Biopharmaceutics of bupivacaine-SBE7- βCD complex following percutaneous sciatic nerve administration in rabbits

The effect of a new modified β-cyclodextrin derivative, sulfobutylether7- β-cyclodextrin (SBE7- βCD) on the biopharmaceutics of local anesthetic bupivacaine (BVC) was studied in a rabbit sciatic model. Phase-solubility study revealed the formation of a 1:1 complex of the Al type between BVC and SBE7- βCD, with an apparent stability constant of 149±7 M −1. Then, BVC hydrochloride (BVC-HCl) and BVC complexed with SBE7- βCD (BVC-SBE7- βCD) were administered around the sciatic nerve both as solutions, in a randomized cross-over design in six New Zealand rabbits. The plasma concentrations of BVC, the onset and duration of motor blockade were evaluated. For the dose of BVC injected (5 mg in 2.5 ml), complexation with SBE7- βCD led to a decrease in the maximum plasma concentration ( C max) of BVC, while the time to reach C max ( T max) was increased. Complexation also delayed the onset of motor block and did not modify its duration. This decrease in absorption rate of BVC following complex administration was confirmed by Loo-Riegleman absorption analysis. The effect of SBE7- βCD concerned mainly the faster absorption phase, responsible for side effects, but had also an impact on the slower phase, even if not stastistically significant, shown by a flip-flop in the elimination constant. Complexation may be useful to improve the therapeutic index of local anesthetics, allowing greater amounts of drug to be injected in order to prolong nerve blockade.

Comparative local anesthetic efficacy and pharmacokinetics of epidurally administered ropivacaine and bupivacaine in the sheep

Ropivacaine is the S(-) propyl homolog of bupivacaine and mepivacaine. Studies in humans have confirmed the results of studies in laboratory animals that ropivacaine is a long-acting local anesthetic with an anesthetic profile similar to bupivacaine. Acute, intravenous systemic toxicity studies have been conducted in sheep and dogs. Local anesthetic efficacy has been studied after epidural administration in the dog. This study was initiated to determine the local anesthetic efficacy and pharmacokinetics of ropivacaine and bupivacaine after epidural administration in an experimental sheep model and to evaluate the sheep model as a model of experimental epidural anesthesia. Twelve adult nonpregnant ewes were prepared with chronically implanted lumbar epidural catheters and arterial lines. Each sheep received injections of 5.0 mL ropivacaine and bupivacaine (0.5% and 0.75%) in a blinded, random, cross-over fashion. Onset and duration of sensory and motor blockade were evaluated. Arterial blood samples were drawn for serum drug concentration determinations and pharmacokinetic analysis. Onset and duration of motor blockade were similar for comparable concentrations of both drugs. Both concentrations of ropivacaine and bupivacaine 0.5% demonstrated differential neural blockade. The peak serum concentrations generally occurred within 8 minutes after administration. The terminal elimination half-life in serum was about 3.5-4.0 hours and 6 hours for ropivacaine and bupivacaine, respectively. No signs of systemic toxicity were observed. Results of sensory and motor blockade were consistent with previous studies in laboratory animals and humans. Ropivacaine produces sensory and motor blockade which is similar to that produced by equal concentrations of bupivacaine after epidural administration in the sheep. Peak serum concentrations produced no signs of systemic toxicity. The results of this study are consistent with previously published data from studies in laboratory animals and humans. The sheep model of experimental epidural anesthesia appears to be a clinically relevant method to evaluate experimental local anesthetics.

Extradural bupivacaine‐loaded microspheres and spinal cord bloodflow in the chronically instrumented rabbit

The local anaesthetic agent bupivacaine decreases spinal cord blood flow. This study documents the effect of bupivacaine-loaded polylactic acid microspheres, a formulation allowing sustained release, in the awake rabbit. Animals received at random extradural injection (1 ml) of either 5 mg of plain bupivacaine (n = 6) or 5 mg of bupivacaine-loaded microspheres (n = 6). Arterial blood pressure, cardiac output and spinal cord blood flow, using radioactive microspheres, and arterial blood gas tensions were measured before (T0) and 30 (T30) and 120 (T120) min after the extradural injection. Motor blockade was assessed on a four-point scale every 5 min until complete recovery. All rabbits experienced paralysis of hindlimbs. Those receiving bupivacaine recovered completely before T120, and the block duration was 86 +/- 23 min (mean +/- SD), whereas the block duration was 210 +/- 60 min (P < 0.05) in those receiving the microsphere formulation. Left renal blood flow baseline was 470 +/- 179 (mean +/- SD) and right renal blood flow was 464 +/- 177 ml min(-1) 100g(-1) and did not vary significantly throughout the experiment. Lumbar spinal cord blood flow decreased in both groups, at T30 with bupivacaine (-16 +/- 7%) and at T120 with microspheres (-12 +/- 8%). Arterial blood pressure decreased more rapidly with bupivacaine (-20 +/- 14% within 15 min) than with microspheres (-19 +/- 11% within 30 min) and returned to baseline at T120 in both groups. Cardiac output and arterial blood gas tensions did not change significantly. We conclude that polylactic acid microspheres can prolong motor blockade from bupivacaine. Whatever its formulation, and independently of systemic haemodynamic and blood gas variables, bupivacaine leads to a decrease in spinal cord blood flow, which persists for the duration of motor blockade. This suggests that motor block must be avoided in clinical practice when extradural bupivacaine is used for pain relief.

Epidural Clonidine after Cesarean Section Appropriate Dose and Effect of Prior Local Anesthetic

Epidurally administered clonidine represents a new approach to postcesarean section pain therapy, yet the appropriate bolus dose and infusion to provide effective pain relief have not been defined. In addition, whether 2-chloroprocaine, a commonly used local anesthetic for intraoperative anesthesia, interferes with clonidine's analgesia, as it does with that of opioids, has not been examined. In this study, using a randomized, blinded design, 63 women received either bupivacaine or 2-chloroprocaine for epidural anesthesia for cesarean section and then received, upon request for analgesia in the recovery room, epidural clonidine 400 micrograms or 800 micrograms bolus, each followed by a 24-h infusion of 40 micrograms/h, or an equivalent volume bolus and infusion of saline. In the bupivacaine group, both clonidine doses produced equivalent analgesia, as determined by pain scores and time to first supplemental intravenous morphine request, and sustained analgesia was produced by clonidine infusion, as measured by need for supplemental morphine. In contrast, 2-chloroprocaine diminished analgesia from 800 micrograms by 21% and abolished analgesia from 400 micrograms clonidine. After 2-chloroprocaine, sustained analgesia from continuous clonidine infusion was present only in the group who had received 800 micrograms clonidine. Clonidine did not alter resolution of residual local anesthetic sensory blockade, as measured by 2- or 4-segment regression following either local anesthetic, but did prolong duration of motor blockade in women receiving bupivacaine. Clonidine produced small decreases in heart rate and blood pressure. One patient received iv fluids for hypotension; one had asymptomatic bradycardia resolving without therapy; and one had mild hypoxemia with snoring during clonidine-induced sedation, responding to supplemental oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensory and Motor Blockade During Epidural Analgesia With 1%, 0.75%, and 0.5% Ropivacaine???A Double-Blind Study

Levels of sensory (pinprick) and somatic motor blockade were measured in a double-blind study of 30 volunteers given single epidural injections of 1%, 0.75%, and 0.5% ropivacaine. Onset of analgesia was rapid with all concentrations (7-10 min). Maximal levels of analgesia were established 60 min after injection, with no significant differences in the maximal median cephalad spread. Duration of analgesia at the T-12 level and total duration were significantly longer with 1% and 0.75% than with 0.5% ropivacaine. Motor blockade was assessed by a quantitative method (measurements of isometric muscle force) and a qualitative method (modified Bromage scale). Onset of motor blockade measured by the quantitative method was significantly slower with 0.5% ropivacaine than with the higher concentrations. Maximal muscle weakness occurred 1-1.5 h after injection with all three concentrations. With increase in ropivacaine dose from 100 to 200 mg, the intensity and duration of motor blockade increased. Muscles involved in knee extension were blocked most, those of plantar flexion least. Recovery of motor function, assessed by the above-mentioned quantitative method, occurred simultaneously with the recovery of pinprick perception. Motor blockade registered by Bromage scale showed a slower onset for 0.5% ropivacaine than for the higher concentrations. Mean durations of grade 1 and 2 block were longest for the 1% solution. Motor blockade described by the Bromage scale showed only the first part of the regression phase. Full recovery of muscle strength (Bromage scale = 0) was attained 1.5-2.5 h earlier than assessed by the quantitative method. No adverse effects were registered.

Effects of oral clonidine premedication on concentrations of Cortisol and monoamine neurotransmitters and their metabolites in cerebrospinal fluid and plasma

Forty-two healthy male patients (aged 19-40 years), undergoing orthopaedic surgery under spinal anaesthesia (3 ml isobaric 0.5% bupivacaine), were given clonidine 4.5 micrograms kg-1 orally either 2 (Group I, n = 10) or 4 (Group II, n = 10) hours before the operation, diazepam 0.15 mg kg-1 orally (Group III, n = 10) or a placebo tablet (Group IV, n = 12) 2 h before the operation. Plasma concentrations of cortisol, noradrenaline (NA), adrenaline (A), 3,4-dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) were assayed from venous blood samples just before premedication and just before the spinal block. Cerebrospinal fluid (CSF) concentrations of cortisol, tryptophan, 5-hydroxyindoleacetic acid and catecholamine metabolites were assayed from a sample taken before the spinal block. The plasma NA concentrations of the patients in the groups receiving clonidine decreased clearly compared with the other groups (P less than 0.05). The NA metabolite DHPG was also lower in Groups I and II than in Group III (P less than 0.05) after premedication. Plasma A concentrations were lower in Groups I and III than in Group IV (P less than 0.05). The CSF concentrations of the different substances were similar in all groups. In Group I the sensory blockade lasted significantly longer than in Group III (P less than 0.05) and the mean duration of motor blockade was longer in Group I than in Groups III and IV (P less than 0.05). Two patients in both clonidine groups developed bradycardia (heart rate less than 45 min-1) requiring atropine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative Motor-Blocking Effects of Bupivacaine and Ropivacaine, A New Amino Amide Local Anesthetic, in the Rat and Dog

Ropivacaine (S-(-)-1-propyl-2',6'-pipecoloxylidide) is a new local anesthetic that is structurally related to mepivacaine and bupivacaine. The comparative effects of ropivacaine and bupivacaine on motor function were assessed in the laboratory rat and dog. (It was not possible to accurately evaluate sensory blockade in these models.) Several concentrations of both agents were injected in the region of the sciatic nerve of the rat and into the lumbar epidural or subarachoid space in the dog. Epidural blockade was also performed utilizing solutions of ropivacaine and bupivacaine which contained epinephrine (1:200,000). The rat sciatic block studies indicate that at concentrations of 0.5 and 0.75%, ropivacaine had a slightly shorter time of onset and duration of motor blockade than did bupivacaine. In the epidural and spinal studies in the dog, ropivacaine was less potent and had a shorter duration of motor blockade than did bupivacaine at equal drug concentrations. A 1.0% solution of ropivacaine produced epidural motor blockade similar in onset and duration to that achieved with a 0.75% solution of bupivacaine. Epinephrine did not significantly prolong the duration of motor blockade of either agent after epidural administration.

Comparative Motor-Blocking Effects of Bupivacaine and Ropivacaine, A New Amino Amide Local Anesthetic, in the Rat and Dog

FELDMAN HS, COVINO BG. Comparative motor-blocking effects of bupivacaine and ropivacaine, a new amino amide local anesthetic, in the rat and dog. Anesth Analg 1988;67:1047-52. Ropivacaine (S-(-)-1-propyl-2',6'-pipecoloxylidide) is a new local anesthetic that is structurally related to mepivacaine and bupivacaine. The comparative effects of ropivacaine and bupivacaine on motor function were assessed in the laboratory rat and dog. (It was not possible to accurately evaluate sensory blockade in these models.) Several concentrations of both agents were injected in the region of the sciatic nerve of the rat and into the lumbar epidural or subarachoid space in the dog. Epidural blockade was also performed utilizing solutions of ropivacaine and bupivacaine which contained epinephrine (1:200,000). The rat sciatic block studies indicate that at concentrations of 0.5 and 0.75%, ropivacaine had a slightly shorter time of onset and duration of motor blockade than did bupivacaine. In the epidural and spinal studies in the dog, ropivacaine was less potent and had a shorter duration of motor blockade than did bupivacaine at equal drug concentrations. A 1.0% solution of ropivacaine produced epidural motor blockade similar in onset and duration to that achieved with a 0.75% solution of bupivacaine. Epinephrine did not significantly prolong the duration of motor blockade of either agent after epidural administration.

Clinical Pharmacokinetics of Carbonated Local Anesthetics. I. Subclavian Perivascular Brachial Block Model

Fifty healthy adult patients undergoing upper extremity surgery under brachial plexus anesthesia provided by the subclavian perivascular technique were divided into two groups, so that anesthesia provided by 1% lidocaine hydrochloride in one group could be compared with that provided by 1.1% lidocaine carbonate in the other group. Epinephrine, 1:200,000, was added to both solutions just before injection. Carbonated lidocaine reduced the latency of anesthesia by 45% as compared with the hydrochloride salt and produced complete motor block in almost twice as many patients (54 vs 31%). The duration of anesthesia provided by the two agents was virtually identical, as was duration of motor blockade.

Cerebrospinal fluid catecholamine levels and duration of spinal anaesthesia.

The effects of catecholamines added to dibucaine on the duration of spinal anaesthesia and cerebrospinal fluid catecholamine levels were studied. Free norepinephrine levels increased from 0.107 ng.ml-1 before anaesthesia to 5.8 ng.ml-1 and 1,238 ng.ml-1 after 1.0 microgram or 100 micrograms norepinephrine had been added to the local anaesthetic. The effects of 2.5 micrograms of either norepinephrine or epinephrine added to dibucaine on the duration of motor blockade and sensory regression time were compared. The duration of both were significantly prolonged by added norepinephrine from 96 +/- 17 min to 193 +/- 20 min (sensory blockade) and from 116 +/- 14 min to 204 +/- 34 min (motor blockade), but were not changed by addition of epinephrine. These data suggest that a 2.5 micrograms dose of norepinephrine is sufficient to prolong the duration of spinal anaesthesia and more effective than the same dose of epinephrine.

Spinal Anesthesia with Glucose-Free Bupivacaine

Effects of age on spinal anesthesia using glucose-free 0.5% bupivacaine without epinephrine were studied in two groups of patients, one between 20 and 55 yr old, the other older than 55 yr. All patients received 15 mg bupivacaine. The time to onset of analgesia in caudad segments and the time to maximal motor blockade decreased with age. The upper level of analgesia did not change significantly with increasing age. The times to recovery from analgesia at T12 and for the total disappearance of analgesia were longer in the older patient group. Effects of age on duration of motor blockade could not be demonstrated. Peak plasma concentrations of bupivacaine were significantly greater and the total plasma clearance significantly decreased in older patients. Age had no effect on time to peak concentration or the terminal half-life.

Comparison of Epidural and Spinal Blockade with 0.5% Bupivacaine for Transurethral Surgery

The suitability of spinal versus epidural blockade for transurethral resection of the prostate was studied in 60 patients randomly allocated to spinal and epidural anaesthesia groups. 0.5% bupivacaine (Marcain, Astra, Sweden) was injected at the L3-L4 interspace, the dose being 3 ml in the spinal group and 19 (16-25) ml in the epidural group. The blood pressure decreased similarly after both epidural and spinal injections, but the heart rate was not significantly altered. No statistically significant differences were found between the groups in any of the variables measured, including blood pressure, heart rate, intraoperative blood loss and per- and post-operative complications. However, altogether eight patients in the epidural group, but none in the spinal group, had to be treated because of hypotension (P less than 0.001). The main advantage of the spinal blockade was a faster and more reliable blockade of the lowest sacral segments, and the main advantage of the epidural blockade was a less pronounced and shorter duration of motor blockade.

SPINAL ANAESTHESIA WITH 0.75% BUPIVACAINE AND 0.5% AMETHOCAINE IN 5% GLUCOSE

Three millititre of 0.75% plain bupivacaine and 0.5% amethocaine 3 ml in 5% glucose were used for spinal anaesthesia and compared in a double-blind study of 20 patients undergoing urological surgery. The onset time to maximum cephalad spread of sensory analgesia was approximately 45 min for bupivacaine and approximately 30 min in the amethocaine group (ns). The mean maximum spread of sensory analgesia was similar for both agents: T6-7 180 min after injection, although the cephalad spread of sensory analgesia with bupivacaine persisted for longer at a significantly higher level than that of amethocaine. Duration of sensory analgesia was significantly longer in the bupivacaine group from S3 to S5 and from T12 to L2 levels. Onset time to complete motor blockade of the lower limbs was similar for both agents. Nine of 10 bupivacaine patients and seven of the 10 patients receiving amethocaine had complete motor blockade of the lower limbs. Duration of motor blockade was significantly longer for all degrees in the bupivacaine group.