Intensity Of Motor Block Research Articles

Lidocaine vs. mepivacaine for peribulbar anaesthesia in cataract surgery

Lidocaine vs. mepivacaine for peribulbar anaesthesia in cataract surgery

Continuous Epidural Block Versus Continuous Popliteal Nerve Block for Postoperative Pain Relief After Major Podiatric Surgery in Children: A Prospective, Comparative Randomized Study

Foot and ankle surgery in children is very painful postoperatively. Adverse effects from opioids and continuous epidural block (CEB) limit their use in children. Continuous popliteal nerve blocks (CPNB) have not been studied for this indication in children. In this prospective, randomized study we evaluated the effectiveness and adverse events of CPNB or CEB in children after podiatric surgery. Fifty-two children scheduled for foot surgery were separated into four groups by age and analgesia technique. After general anesthesia, 0.5 to 1 mL/kg of an equal-volume mixture of 0.25% bupivacaine and 1% lidocaine with 1:200000 epinephrine was injected via epidural or popliteal catheters. In the postoperative period, 0.1 mL x kg(-1) x h(-1) (group CPNB) or 0.2 mL x kg(-1) x h(-1) (group CEB) of 0.2% ropivacaine was administered for 48 h. Niflumic acid was routinely used. Adverse events were noted in each treatment group. Postoperative pain during motion was evaluated at 1, 6, 12, 18, 24, 36, and 48 h. Requirement for rescue analgesia (first-line propacetamol 30 mg/kg 4 times daily or second-line 0.2 mg/kg IV nalbuphine), and motor blockade were recorded. Parental satisfaction was noted at 48 h. Twenty-seven patients were included in the CEB groups and 25 in CPNB groups. There were 32 children 1 to 6 yr of age (CPNB = 15; CEB = 17) and 20 children 7 to 12 yr of age (CPNB = 10; CEB = 10). The demographic data were comparable among groups. Postoperative analgesia was excellent for the two continuous block techniques and in the two age groups. Motor block intensity was equal between techniques. Adverse events (postoperative nausea or vomiting, urinary retention, and premature discontinuation of local anesthetic infusion in the 1- to 6-yr-old group) were significantly more frequent in the CEB group (P < 0.05). Eighty-six percent of the parents in the CEB groups and 100% in the CPNB groups were satisfied. We conclude that although both CEB and CPNB resulted in excellent postoperative analgesia in this study, CPNB was associated with less urinary retention and nausea and vomiting. Therefore, we recommend CPNB as the ideal form of postoperative analgesia after major podiatric surgery in 1- to 12-yr-old children.

Estudo comparativo entre soluções a 0,5% de levobupivacaína, bupivacaína em excesso enantiomérico de 50% e bupivacaína racêmica em anestesia peridural para cirurgia de abdômen inferior

With the purpose of finding a local anesthetic agent safer than racemic bupivacaine, several animal studies have been performed with its isomers. This study aimed at evaluating, for one hour after injection, the efficacy of 50% enantiomeric excess bupivacaine as compared to levobupivacaine and racemic bupivacaine for epidural anesthesia in patients submitted to lower abdominal procedures. After the Research Ethics Committee approval, 87 patients aged 18 to 65 years, physical status ASA I and II, undergoing lower abdominal procedures were included in this randomized double-blind study. Patients were distributed in three groups which received 27 mL (including test dose) of local anesthetics with epinephrine (1:200,000) and fentanyl (100 microg) solutions. Group I was given 0.5% levobupivacaine, group II received 50% enantiomeric excess 0.5% bupivacaine, and group III received 0.5% bupivacaine. Monitoring consisted of pulse oximetry, cardioscopy and noninvasive blood pressure. Motor and sensory block profiles were evaluated, in addition to the incidence of side effects. Unidentified local anesthetic vials were numbered, and the randomized distribution list was opened only at the end of the experiment. There were no significant differences regarding height and physical status between groups. There was a significant age difference in group I. Hemodynamic parameters were similar between groups. Motor block intensity was significantly lower in group I as compared to groups II and III. All groups presented adequate motor and sensory block for surgery, with few side effects, suggesting that these solutions are effective for epidural anesthesia for lower abdominal procedures. Levobupivacaine produced less motor block as compared to the other compounds.

Sistemas de liberação controlada com bupivacaína racêmica (S50-R50) e mistura enantiomérica de bupivacaína (S75-R25): efeitos da complexação com ciclodextrinas no bloqueio do nervo ciático em camundongos

Bupivacaine-induced side effects have led to the search for new local anesthetics (LA) with similar potency and lower toxicity, such as bupivacaine enantiomeric mixture (S75-R25). Drug-delivery systems for LA in carriers, such as cyclodextrins (CD), have been developed to improve anesthetic potency and therapeutic index of those drugs. This study aimed at preparing, characterizing and evaluating the anesthetic efficacy of inclusion complexes of bupivacaine enantiomeric mixture (S75-R25) and racemic bupivacaine (S50-R50) with hydroxypropylb- cyclodextrin (HPb-CD) comparing them to clinically available preparations.Inclusion complexes were obtained by mixing appropriate volumes of HPb-CD and S50-R50 or S75-R25 to final 1:1 or 1:2 molar ratios and were characterized by phase solubility experiments. Affinity constants (K) were determined between HPb-CD and each LA. Motor and sensory blocks induced by plain or complexed LA formulations were evaluated in mice by sciatic nerve block. Three LA concentrations were used during the experiment: 0.125, 0.25 and 0.5%.Solubility experiments results were indicative of S50-R50:HPb-CD and S75-R25:HPb-CD complexation, with similar affinity constant (K) values: 14.7 M-1 and 14,3 M-1, respectively. In vivo experiments have shown that complexation has enhanced differential nerve blockade induced by LA: i) motor blockade duration induced by S75-R25 was similar, to the induced by but less intense S50-R50 ( p < 0.001). S50-R50HPb-CD and S75-R25HPb-CD complexes have decreased onset (p < 0.01 and p < 0.05, respectively), without changing motor block intensity (Emax) as compared to plain drugs; ii) sensory block evaluation has revealed higher analgesic intensity with S50-R50HPb-CD (2-fold, p < 0.001) and S75-R25HPb-CD (1.5-1.8-fold, p < 0.01 and p < 0.001, respectively) with both molar ratios (1:1 and 1:2, LA:CD), in addition to prolonging analgesic effect as compared to S50-R50 and S75-R25.More pronounced analgesic effects obtained by complexation with HPb-CD have shown that both formulations, S50-R50HPb-CD and S75-R25HPb-CD, are very useful for postoperative pain relief, requiring lower LA concentrations. Nevertheless, it is worth noticing that S75-R25 - being less toxic than racemic bupivacaine - is an interesting alternative for the development of more effective and safe drug-delivery systems as compared to racemic bupivacaine (S50-R50).

Patient-controlled thoracic epidural infusion with ropivacaine 0.375% provides comparable pain relief as bupivacaine 0.125% plus sufentanil after major abdominal gynecologic tumor surgery

Background and Objectives: We tested the hypothesis that an opioid-free local anesthetic alone is able to provide comparable analgesia to the opioid supplemented epidural application of local anesthetics using thoracic epidural catheters after major abdominal surgery. Methods: In a prospective, randomized, and double-blind study, we have compared the analgesic efficacy and side effects of ropivacaine 0.375% (group R) versus bupivacaine 0.125% in combination with sufentanil 0.5 μg/mL−1 (group B/S) via a thoracic epidural catheter for a duration of 96 hours after major abdominal surgery in 30 gynecologic tumor patients. Piritramide was given for breakthrough pain. Assessments were performed every 12 hours after start of the epidural infusion using continuous (first 24 hours) and patient-controlled epidural analgesia (PCEA) (24 to 96 hours). Results: No differences were seen in demographic and perioperative data. Dynamic pain scores (visual analog scale [VAS] values) were comparable between groups during mobilization (group R v group B/S: 24 hours: 40 ± 30 v 36 ± 14, P = .9; 48 hours: 46 ± 33 v 42 ± 25, P = .93; 72 hours: 42 ± 24 v 48 ± 26, P = .78; 96 hours: 42 ± 25 v 29 ± 28, P = .49) and on coughing during the whole study period. Hemodynamics, intensity of motor block (Bromage scale), and side effects like nausea, vomiting, pruritus, and bladder disfunction also did not differ between groups. Conclusion: The present study shows that thoracic epidural infusion of ropivacaine 0.375% provides comparable pain relief and incidence of side effects after major abdominal gynecologic surgery as bupivacaine 0.125% in combination with 0.5 μg/mL−1 sufentanil and may therefore represent an alternative in epidural pain management. Reg Anesth Pain Med 2002;27:367-373.

Bupivacaine pharmacokinetics and motor blockade following epidural administration of the bupivacaine-sulphobutylether 7-β-cyclodextrin complex in sheep

Bupivacaine pharmacokinetics and motor blockade following epidural administration of the bupivacaine-sulphobutylether 7-β-cyclodextrin complex in sheep

Quantitative assessment of motor block in labouring women receiving epidural analgesia.

The assessment of motor block associated with epidural analgesia is traditionally performed using the modified Bromage Score. However, it is a qualitative and quantitative measurement of both spread and intensity of motor block in the lower limbs, and it has been adapted from Bromage's original use as an assessment of the adequacy of epidural anaesthesia for abdominal surgery. A number of quantitative assessment methods exist but these are either laboratory based and/or impracticable in the clinical situation of labour. We therefore set out to devise a quantitative assessment method which would be easy to use and acceptable to labouring women receiving epidural analgesia. A force transducer was modified to enable power of hip adduction to be assessed quantitatively before and after epidural analgesia was established. These results were compared with the modified Bromage Scale and an extended scale which further subdivided the scores between 0 and 1. Our results show that there is a large variation in the quantitative measurement of motor block (as measured by adductor strength) that may not be detected by the sole use of the modified Bromage Score. We suggest that future studies to assess motor block in the clinical setting use an additional quantitative method of assessment.

Spinal anesthesia with hypobaric bupivacaine for knee arthroscopies: Effect of posture on motor block

Background and Objectives: The clinical impact of patient positioning on motor block during unilateral spinal anesthesia was the focus of our study. It was assumed that a 45° rotation toward the prone position would minimize blocking the ventral motor roots compared with using the conventional lateral decubitus position. Methods: Spinal anesthesia with 3.4 mL of hypobaric 0.18% bupivacaine via a 27-gauge Whitacre needle was administered to 70 patients undergoing knee arthroscopy. The patients were kept either in a lateral decubitus position (group I) or rotated approximately 45° toward the prone position (group II). No prophylactic vasopressors or infusions were used. The intensity of motor block (modified Bromage scale) was assessed for both the operative and the contralateral side. Results: The patients in group I had a slightly more pronounced motor block, but statistical significance could be shown only 20 minutes following the block. There was no statistical difference between the groups in the need of additional analgesics during the operation. None of the patients needed general anesthesia. The hemodynamics were stable and none of the patients developed postspinal headache or backache. Conclusions: The position of the patient affects the spread of the spinal anesthesia when clearly hypobaric agents are used. However, this small modification in positioning of the patient did not lead to a clinically meaningful difference in the spread of the motor block. Reg Anesth Pain Med 2001;26:30-34.

Patient-controlled epidural analgesia with fentanyl-bupivacaine: Influence of prior dural puncture

Background and Objectives: Combined spinal epidural anesthesia (CSEA) involves the epidural administration of local anesthetic and opioid solutions adjacent to the prior dural puncture, potentially increasing their diffusion into the subarachnoid space. This study was designed to evaluate the influence of dural puncture on the adequacy and extent of analgesia, and drugs requirements of patient-controlled epidural analgesia (PCEA) in the postoperative period. Methods: In this prospective double-blind study, 40 patients undergoing major abdominal surgery under general anesthesia followed with PCEA were randomly assigned to either group I (preoperative insertion of an epidural catheter) or group II (preoperative dural puncture with a 25-g Quincke needle + insertion of an epidural catheter). Postoperatively, a PCEA pump delivered an infusion of 0.1% bupivacaine + fentanyl (3 μg/mL) at 5 mL/h. Participants were allowed to self-administer 5-mL boluses of the same solution with a 15-minute lock-out interval. Hourly epidural solution requirements were recorded for 40 hours. Sensory and motor block, and pain scores were also analyzed. Results: There was no difference between groups with regard to epidural solution requirements, pain scores, spread of sensory blockade, or intensity of motor block. Conclusion: Dural puncture with a 25-gauge Quincke needle, performed as part of CSEA, does not influence the drug requirements when a combination of 0.1% bupivacaine and fentanyl (3 μg/mL) is used for PCEA after major abdominal surgery. Reg Anesth Pain Med 2000;25:254–258.

Neonatal outcome and mode of delivery after epidural analgesia for labour with ropivacaine and bupivacaine: a prospective meta-analysis

In this prospective meta-analysis, we have evaluated the effect of epidural analgesia with ropivacaine for pain in labour on neonatal outcome and mode of delivery compared with bupivacaine. In six randomized, double-blind studies, 403 labouring women, primigravidae and multiparae, received epidural analgesia with ropivacaine or bupivacaine 2.5 mg ml-1. The drugs were administered as intermittent boluses in four studies and by continuous infusion in two. Apgar scores, neurological and adaptive capacity scores (NACS), degree of motor block and mode of delivery were recorded. The studies were designed prospectively to fit meta-analysis of the pooled results. Results showed similar pain relief and consumption of the two drugs. In the vaginally delivered neonates, NACS scores were approximately equal for both groups at 2 h, but at 24 h there were fewer infants with NACS less than 35 in the ropivacaine compared with the bupivacaine group (2.8% vs 7.6%; P < 0.05). Spontaneous vaginal deliveries occurred more frequently overall with ropivacaine than with bupivacaine (58% vs 49%; P < 0.05) and instrumental deliveries (forceps and vacuum extraction) less frequently (27% vs 40%; P < 0.01), while the frequency of Caesarean section was similar between groups. The intensity of motor block was lower with ropivacaine. There were no significant differences in adverse events.

Effects of Concentration and Volume of 2-Chloroprocaine on Epidural Anesthesia in Volunteers

Background: Effect of local anesthetic concentration and volume on the spread and density of epidural anesthesia is unclear. This study was performed to delineate effects of a threefold difference in concentration and volume of 2-chloroprocaine on epidural anesthesia. Methods: Twelve healthy volunteers underwent lumbar epidural anesthesia with 300 mg of 2-chloroprocaine as a 3% (10 ml) and a 1% (30 ml) solution in a randomized, double-blind, balanced, crossover fashion. Sensory block was assessed with pinprick, touch (calibrated plastic filament), cold, and electrical stimulation. Motor block was assessed at the quadriceps and gastrocnemius muscles with isometric force dynamometry. Differences between solutions were assessed with repeated measures analysis of variance followed by post hoc testing. Results: The number of dermatomes blocked to pinprick, touch, and cold was significantly greater with the 1% concentration (2 dermatomes greater than the 3% concentration on average, P < 0.05). Similar intensity of sensory block to electrical stimulation developed at the hip and knee and was unaffected by concentration of 2-chloroprocaine. Similar intensity of motor block developed at the quadriceps with both concentrations. Conclusions: intensity of sensory and motor block from epidural anesthesia with 2-chloroprocaine appears to depend primarily on total milligram dose.

Extradural S(-)-bupivacaine: comparison with racemic RS-bupivacaine

Bupivacaine has a chiral centre and is currently available as a racemic mixture of its two enantiomers: R(+)-bupivacaine and S(-)-bupivacaine. Preclinical studies have demonstrated that there is enantiomer selectivity of action with the bulk of central nervous system and cardiovascular toxicity residing with the R(+) isomer. The aim of this study was to compare the clinical efficacy and safety of S(-)-bupivacaine with racemic RS-bupivacaine for extradural anaesthesia. We studied 88 patients undergoing elective lower limb surgery under lumbar extradural anaesthesia who received 15 ml of 0.5% or 0.75% S(-)-bupivacaine, or 0.5% RS-bupivacaine in a randomized, double-blind study. There was no difference in onset time, maximum spread of sensory block or intensity of motor block between the three groups. Duration of sensory block was significantly longer for 0.75% S(-)-bupivacaine. We conclude that S(-)-bupivacaine has similar local anaesthetic characteristics to RS-bupivacaine when used for extradural anaesthesia.

Spinal Bupivacaine in Ambulatory Surgery

The safety of lidocaine spinal anesthesia has recently been called into question by reports of both permanent and transient neurologic toxicity.This study explored the possibility of adapting the longer acting spinal bupivacaine to ambulatory surgery. Sixty patients presenting for ambulatory arthroscopy were randomized to four groups receiving the following spinal anesthetics: Group I (15 mg bupivacaine), 3 mL of 0.5% spinal bupivacaine in 8% dextrose; Group II (10 mg bupivacaine), 2 mL of the 0.5% spinal bupivacaine + 1 mL saline; Group III (7.5 mg bupivacaine), 1.5 mL of the 0.5% spinal bupivacaine + 1.5 mL saline; Group IV (5 mg bupivacaine), 1 mL of the 0.5% spinal bupivacaine + 2 mL saline. Maximum block height was T-5 in Group I versus T-8 in the other groups. Onset times to peak block were similar in all groups and averaged 14 min. Time to two-segment regression, complete regression, micturition, and discharge were significantly reduced from Group I to Group II and from Group II to Group III. Reductions in times between Groups III and IV did not achieve statistical significance. Times from placement of the spinal block until discharge were 471 +/- 35, 260 +/- 15, 202 +/- 14, and 181 +/- 8 min, respectively, for the four groups. The intensity of motor block decreased significantly from group to group, such that 13 of the 15 patients in Group IV failed to achieve Bromage level 2 or 3. The intensity of sensory block also decreased from group to group with four patients in Group IV having pain intraoperatively that required further treatment. Therefore, Group III provided the optimum combination of adequate depth of anesthesia and rapid recovery. The results of this study indicate that spinal anesthesia with 7.5 mg of 0.5% bupivacaine in 8% dextrose diluted with an equal volume of saline provides an acceptable spinal anesthetic for ambulatory arthroscopy with a recovery profile appropriate to the ambulatory setting. (Anesth Analg 1996;83:716-20)

Extradural anaesthesia for Caesarean section: a double-blind comparison of 0.5% ropivacaine with 0.5% bupivacaine

Seventy-three parturients for elective Caesarean section were allocated randomly to receive extradural block with 20 ml of either 0.5% ropivacaine or 0.5% bupivacaine. If the block did not reach T6 within 30 min, another 5 ml of solution was given. If needed, a further 5 ml was given 45 min after the main dose. The mean total dose of bupivacaine was 23.1 ml (n = 35) and of ropivacaine 23.7 ml (n = 37). There was no significant difference between the groups in the profile of sensory block produced. There was no significant difference in the time of onset, or intensity of motor block between the groups but the duration of motor block was significantly shorter in the ropivacaine group. There was no significant difference in neonatal outcome, as assessed by Apgar score, umbilical cord blood-gas tensions at delivery or the neurological and adaptive capacity score 2 and 24 h after delivery.

Epidural infusion of alfentanil or diamorphine with bupivacaine in labour—a dose finding study

Following induction of epidural analgesia with 0.375% bupivacaine, 120 healthy parturients were randomly assigned in a double blind fashion to one of eight infusion groups. All received 8 ml.h-1 of 0.125% bupivacaine either alone (control group), or with alfentanil at 133, 266 or 400 micrograms.h-1 (groups A1-A3) or with diamorphine at 133, 266, 400 or 533 micrograms.h-1 (groups D1-D4). Significantly longer top-up intervals were achieved with the two highest doses of both alfentanil and diamorphine when compared with bupivacaine alone (p < 0.01), making the minimum effective doses 266 micrograms.h-1 of alfentanil and 400 micrograms.h-1 of diamorphine. Perineal analgesia was better in all the opioid groups compared with the control group (p < 0.05). The intensity of motor block was greater in the control group (p < 0.05). The incidence of pruritus did not differ between groups. The highest dose of diamorphine caused significantly more nausea. No significant neonatal side-effects were demonstrated.

Epidural mepivacaine for cesarean section: Effects of a pH-adjusted solution

Study Objective: To determine the clinical effects of the alkalinization of 2% mepivacaine with epinephrine used for epidural block during cesarean section. Design: Randomized, double-blind, placebo-controlled (standard commercial preparation of 2% mepivacaine with epinephrine) study. Setting: Inpatient obstetric department at a general hospital. Patients: Seventy patients scheduled for elective: cesarean section under epidural anesthesia. Interventions: Two groups of 35 patients each, receiving either the standard commercial preparation of mepivacaine or the pH-adjusted solution (prepared with the addition of 0.1 meq/ml of sodium bicarbonate to the standard commercial solution). Measurements and Main Results: Measurements of sensory (pinprick) and motor (Bromage's criteria) block were taken at 1- to 2-minute intervals beginning after the completion of the epidural injection. Increasing the pH of the mepivacaine resulted in a significant shortening of the time of analgesia onset (9.3 minutes compared with 16.01 minutes, p < 0.01) and of peak effect (11.1 minutes compared with 21.2 minutes, p < 0.01). The alkalinization did not affect duration of the block, intensity of motor block, or mean dose of local anesthetic used. Conclusion: The alkalinization allowed the surgery to proceed more rapidly, significantly decreasing the time internal between epidural block and delivery of the infant.

SPINAL ANAESTHESIA WITH PLAIN 0.5% BUPIVACAINE AT 19 °C AND 37 °C

Forty-five men aged 50-80 yr undergoing urological surgery under spinal anaesthesia were allocated randomly to three groups. All patients received 0.5% plain bupivacaine 3 ml injected at the L2-3 interspace. The temperature of the solution in group 1 was 19 degrees C, in groups 2 and 3 37 degrees C. In groups 1 and 2 the injection was performed with the patient sitting; in group 3 the patient was in a lateral horizontal position. Spread of block, intensity of motor block and cardiovascular stability were measured. Warming the solution from 19 degrees C to 37 degrees C before spinal injection with the patient in the sitting position did not significantly affect these variables. However, the extent of analgesia was reduced significantly when the 37 degrees C solution was injected with the patient in the lateral horizontal compared with the sitting position.

A comparison of glucose‐free 2% lidocaine and hyperbaric 5% lidocaine for spinal anaesthesia

Fifty patients scheduled to undergo transurethral surgery of the bladder were allocated to receive spinal anaesthesia with either glucose-free 2% lidocaine (80 mg) or hyperbaric 5% lidocaine (80 mg). Onset time, cephalad spread of analgesia, duration of analgesia, duration and intensity of motor block, quality of analgesia, and the patients' ability to walk 5 m and to micturate postoperatively were assessed. Onset and spread of analgesia were fast and comparable in the two groups. At 60 min, the median segmental level of analgesia was T9 and T10 for the 2% and the 5% group, respectively, allowing transurethral surgery to be performed for at least 1 h. In the 2% group the motor block was more pronounced and longer lasting than in the 5% group. Two patients in the 5% group needed general anaesthesia because of pain. The time from injection of the spinal anaesthetic until the patients were able to walk 5 m and to micturate was equal in the two groups, and 89% of all the patients were able to walk and micturate within 4 h. It is concluded that spinal anaesthesia with 80 mg and 2% or 5% lidocaine provides analgesia for transurethral surgery and is characterized by fast recovery of motor and detrusor function.

QUALITY OF EPIDURAL BLOCKADE III: CARBONATED LOCAL ANAESTHETIC SOLUTIONS

SUMMARY The effects of carbon dioxide-enriched local anaesthetics injected epidurally were compared in animals and in man. Addition of carbon dioxide at tensions of ½ and 1 atmosphere shortened by 20–30 per cent the latency of onset and spread of analgesia with lignocaine hydrochloride but did not increase intensity of motor block. The quality of epidural blockade was improved when lignocaine or prilocaine base was dissolved as salts of carbonic acid at a Pco 2 of 1 atmosphere. Blockade became complete 33 per cent faster with lignocaine and 24 per cent faster with prilocaine, and the degree of motor block was increased by 42 per cent and 33 per cent, respectively, over control values. A smaller but significant increase (10–15 per cent) in spread and duration of analgesia occurred with carbon dioxide-base solutions also. A high Pco 2 increased the uptake of lignocaine in excised frog nerves but not after epidural injection of labelled lignocaine in live dogs. Analysis of uptake of 14 C-lignocaine by the neuraxis and meninges in dogs suggests that the improved quality of blockade produced by the carbon dioxide bases is due not to an absolute increase in tissue uptake but to a favourable distribution in tissue. A direct action of carbon dioxide on the axon membrane may be an additional factor. The carbon dioxide-base solutions caused no irritant effects in the subarachnoid space of dogs after intracisternal injection. Results obtained with the carbon dioxide-base solutions were superior to those of other agents used previously for epidural analgesia.

A COMPARISON OF THE HYDROCHLORIDE SALTS OF LIGNOCAINE AND PRILOCAINE FOR EPIDURAL ANALGESIA

Lumbar epidural blockade has been used in 317 subjects to compare the analgesic properties of the hydrochloride salts of lignocaine and prilocaine in 2 per cent and 3 per cent concentrations, with and without 1/200,000 adrenaline. Prilocaine has a slower onset and spread of analgesia than lignocaine. Duration of action and intensity of motor blockade is greater with plain prilocaine than with plain lignocaine in both 2 and 3 per cent concentrations. Addition of a vasoconstrictor improves the duration and quality of blockade of both prilocaine and lignocaine, but the effect on the latter is greater than on the former. The proportionate effect is such that the intensity of motor block and duration become practically the same in the 2 and 3 per cent solutions of both drugs when 1/200,000 adrenaline is present. At any given age all the test solutions, except 3 per cent plain prilocaine, produce the same degree of segmental spread. The dose-requirements of 3 per cent plain prilocaine are about 40 per cent greater than the other solutions at 20 years, but this difference decreases with age, and disappears by the ninth decade. Three per cent lignocaine with adrenaline produces the most efficient blockade of all the test solutions. However, the lower toxicity of prilocaine makes 3 per cent prilocaine with adrenaline the solution of choice in most instances.