Single Epidural Injection Research Articles

F Response and H Reflex for Monitoring Nerve Block During Epidural Analgesia with Ropivacaine

The effect of a single epidural injection of ropivacaine on the motor and sensory function controlled from the L5/S1 level was investigated in 28 male volunteers. Concentrations of 1%, 0.75%, or 0.5% ropivacaine, 20 mL, administered at the L2/3 level were studied. Motor function was assessed quantitatively (measurement of muscle force by mechano-transducers), and sensory function by the pinprick method. In addition, F response and H reflex, tests which measure the conduction velocity in the central parts of peripheral nerves, were used. Epidural ropivacaine caused dose-dependent prolongation of the latencies of both these variables. F response latency recovered significantly later than motor function measured by mechano-transducers in the two lower concentration groups. H reflex latency recovered significantly later than sensory function assessed by the pinprick method in all three concentration groups. The time needed for recovery of F and H latencies was not significantly longer than the time from epidural injection to mobilization. At the time when the subjects could go through the mobilization procedure, 12 of 28 subjects were not completely recovered. In 5 of these 12 subjects, the H reflex latency was persistently prolonged at the end of the investigation, long after the subjects felt "normal" again. On follow-up recordings 5 mo later, the baseline latency had been regained in all five subjects. We conclude that F response and H reflex latencies are good indicators of the inhibition of nerve impulse conduction induced by epidural analgesia.

Pharmacokinetics and pharmacodynamics of medullar agents: a. Local anaesthetics

In considering the pharmacokinetics of local anaesthetics, both the systemic absorption and systemic disposition are of importance. Systemic absorption of local anaesthetics limits the duration of nerve block and is of concern in view of systemic toxicity. Initial absorption rates are higher after epidural than after subarachnoid injection, whereas the slower, secondary absorption rates are similar. Amide-type local anaesthetics undergo extensive tissue distribution. Volumes of distribution vary from approximately 60 to nearly 200 litres. Elimination occurs almost exclusively by biotransformation. Amide-type agents are predominantly metabolized in the liver. Total body clearances vary from 0.6 to 2.4 litres/min. Ester-type agents are hydrolysed in the liver and in blood, ensuring very fast elimination. Blood or plasma concentrations after single epidural injections vary with the local anaesthetic and the dose. Addition of adrenaline to local anaesthetic solutions reduces the peak plasma concentrations. Long-term continuous epidural infusions for postoperative pain relief may result in significant accumulation, reflecting increases in plasma protein binding. Plasma concentrations after subarachnoid administration are very low, so the risk of systemic toxicity is very small. The main factors determining the onset, quality and duration of epidural neural blockade are the local anaesthetic employed and its physicochemical properties. Onset in the caudad segments is usually faster, and spread of analgesia is higher in older patients. Addition of adrenaline prolongs the duration. Ongoing clinical studies show that ropivacaine is an effective long-acting local anaesthetic when given epidurally. Bupivacaine has frequently been used, either as a glucose-free or hyperbaric solution, for spinal anaesthesia. Glucose-free bupivacaine solutions provide long-lasting motor blockade, but appear to provide an unpredictable spread of analgesia. Advancing age has been shown to be associated with a prolonged duration of analgesia with glucose-free bupivacaine solutions and a greater spread of analgesia with hyperbaric bupivacaine solutions.

Maternal and umbilical cord concentrations of fentanyl after epidural analgesia for cesarean section

The maternal and umbilical concentrations of fentanyl were measured after epidural analgesia for cesarean section, using a highly sensitive radioimmunoassay method. Sixteen parturients were anesthetized with a single epidural injection of a mixture of 85 mg bupivacaine 0.5%, 60 mg etidocaine 1%, and 100 μg fentanyl with epinephrine 1:200 000. Apparent maternal individual maximum peak concentration ( C max) of fentanyl was 0.38 ± 0.16 ng/ml (mean ± SD) (range 0.12–0.59 ng/ml) and the time to reach C max ( T max) was 24 ± 14 min (range 5–60 min). Infants were born 19 to 42 min after epidural administration of fentanyl (mean 27 min). Fentanyl concentrations in neonates was 0.13 ± 0.04 ng/ml for the umbilical vein and 0.06 ± 0.03 ng/ml for the artery. The fetus extraction ratio was 53 ± 19% (range 20–83%). The large difference between arterial and venous concentrations of fentanyl may be due to a metabolization by the fetus and/or an uptake of the drug in the fetal tissues. Thus, even if fentanyl levels reaching the fetus after cesarean section under epidural anesthesia, using local anesthetics with 100 μg of fentanyl, are within safe range values, the likehood of fentanyl uptake by fetal tissues calls for a cautious use of repeated fentanyl administration.

Effect of Lidocaine on the Meninges in an Experimental Animal Model

Arachnoiditis has been reported in patients who had received previous epidural injections of anesthetic agents. The purpose of this study was to determine if epidural injections of lidocaine are sufficient to cause arachnoiditis. Four monkeys that received a single epidural injection of lidocaine hydrochloride 1% were compared to four controls that had epidural injections of 0.9% saline. Four dogs that had multiple epidural injections of lidocaine hydrochloride 1% were compared to four controls that had multiple injections of saline. All animals were killed on the eighty-fourth day of the experiment. The dural sac, containing nerve roots and spinal cord, was removed intact from the lumbar spinal canal, fixed, sectioned, stained, and examined microscopically for evidence of arachnoid inflammation and fibrosis. No significant changes were found in the treated animals. Lidocaine hydrochloride 1% injected singly or repeatedly in the epidural space does not appear to be a cause of significant chronic meningeal reaction.

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.

Neuralgia Following Lumbar Sympathectomy

Between March and October 1986, 33 consecutive patients underwent unilateral lumbar sympathectomy in the Thoracic and Cardiovascular Surgical Unit of the Catholic University in Louvain, Belgium. Ten patients experienced postsympathectomy neuralgia. After a single epidural injection of fentanyl, 50 micrograms, and methylprednisolone 80 mg, pain disappeared completely in six patients. Neuralgia recurred in four patients requiring repeat epidural injection with relief of residual symptoms. Epidural infiltration is a reliable treatment for neuralgia after lumbar sympathectomy.

Analgésie péridurale après chirurgie thoracique : morphine versus buprénorphine

A double-blind study was carried out to assess the efficiency and possible side-effects of a single epidural injection of either morphine or buprenorphine at equipotent doses after elective thoracic surgery. The series included 24 patients aged 53.7 ± 11.4 years ; 13 underwent a lobectomy and 11 a pneumonectomy. 6 h after the last intravenous injection of fentanyl, the patients were randomly allocated to one of three equal groups. They received an epidural injection at T8–9 or T9–10 level of either 100 μg · kg −1 morphine (group M) or 6.6 μg · kg −1 buprenorphine (group B) or a subcutaneous injection of 0.1 ml · kg −1 normal saline placebo at the same level (group T). The following parameters were measured 20 and 60 min, and every 6 h up to 48 h after the injection : patient wakefulness, respiratory rate, blood gases, pain (according to a verbal scale), FVC and FEV 1, adverse effects (euphoria, hallucinations, sweating, facial pruritus, nausea) and atelectasia. The duration of surgery, the anaesthetic protocol, the age, weight and height, as well as all the parameters before injection were similar in all three groups. There was a fall in pain intensity from the 20th min to the 24th hour in group M and from the 20th min to the 36th hour in group B, significant for both groups when compared with group T. Similarly, there was a prolonged increase in FEV 1 in both groups M and B. There was no case of severe respiratory depression ; Pa co 2 was increased at the 1st hour (+ 0.3 ± 0.6 kPa) in group B and at the 6th hour (+ 0.5 ± 0.7 kPa) in group M. Fiberoptic bronchoscopy was required for 6 patients in group T, 2 in group M (p < 0.05) and 1 in group B (p < 0.01). The results showed that a single epidural injection of morphine or buprenorphine was a simple, safe and efficient method of analgesia with minimal side-effects after thoracic surgery. Buprenorphine seemed preferable, because of a longer duration of analgesia.

Respiratory Depression after Single Epidural Injection of Local Anesthetic and Morphine

Un cas de bradypnee et de somnolence apres une dose unique de lidocaine avec adrenaline et morphine. Antagonisme par la naloxone

Epidural morphine for control of pain after spinal surgery

Epidural opiates have been used successfully for the control of postoperative pain after obstetrical, abdominal, and orthopedic procedures. The use of these agents for the control of pain after operation on the thoracic and lumbar spine is reported. A catheter is inserted under direct vision into the epidural space after semihemilaminectomy and disc excision, posterior decompressive lumbar laminectomy, and anterolateral thoracolumbar decompression and just before wound closure. Excellent postoperative pain relief is achieved for 8 to 20 hours after single epidural injections of between 2 and 6 mg of morphine. Catheters are left in situ for 2 to 5 days. To date, no complications requiring treatment have been encountered with this approach. (Neurosurgery 13:37-39, 1983)

Peridural analgesia with high doses of fentanyl: failure of the method for early postoperative kinesitherapy in knee surgery

Following orthopedic surgery of the lower limb, ten patients were given fentanyl 5 micrograms . kg-1 in a single epidural injection. Almost complete analgesia (P less than 0.001) was rapidly obtained. The total period of analgesia was rather short (182.3 +/- 32.1 min). The maximal analgesia period was 87 +/- 8.34 minutes. Despite this high dose of fentanyl (245 to 450 micrograms), in five patients the passive mobilization of the knee following surgery was extremely painful and, for that matter, impossible in three of them. Such high doses of fentanyl entail the risk of respiratory depression as respiratory rate is decreased (P less than 0.01) and the Pco2 is increased (P less than 0.01). Fentanyl should not be used at such high dosage and should probably not be preferred to morphine, considering that the duration of analgesia is short, that the analgesic score is identical to that obtained with lower doses or with longer lasting narcotics, that it does not prevent passive mobilization pains and that it entails a definite risk of respiratory depression.

PLACENTAL TRANSFER OF LIGNOCAINE FOLLOWING LUMBAR EPIDURAL ADMINISTRATION

The maternal plasma concentration at delivery and the umbilical venous plasma concentration of lignocaine have been determined following the use of the drug to produce epidural analgesia. Two modes of administering the drug have been examined: one in which a single epidural injection of lignocaine was given and one in which repeated injections were given to produce analgesia for a prolonged period. The results obtained show that lignocaine is rapidly transported from the epidural space to the foetal circulation and that it is present in the foetal circulation in high concentration, in relation to maternal plasma concentration, within 15 minutes after injection. The ratio of umbilical venous plasma concentration to maternal plasma concentration at delivery varied from 0.25 to 1.00. The maternal plasma concentration of lignocaine at delivery was directly related to the total dose of lignocaine given and bore no relation to the rate at which it was given.

PLACENTAL TRANSFER OF LIGNOCAINE FOLLOWING LUMBAR EPIDURAL ADMINISTRATION

The maternal plasma concentration at delivery and the umbilical venous plasma concentration of lignocaine have been determined following the use of the drug to produce epidural analgesia. Two modes of administering the drug have been examined: one in which a single epidural injection of lignocaine was given and one in which repeated injections were given to produce analgesia for a prolonged period. The results obtained show that lignocaine is rapidly transported from the epidural space to the foetal circulation and that it is present in the foetal circulation in high concentration, in relation to maternal plasma concentration, within 15 minutes after injection. The ratio of umbilical venous plasma concentration to maternal plasma concentration at delivery varied from 0.25 to 1.00. The maternal plasma concentration of lignocaine at delivery was directly related to the total dose of lignocaine given and bore no relation to the rate at which it was given.