Regional-Anaesthesie最新文献

The use of a nerve stimulator allows an injection cannula to be located without the cooperation of the patient. Regional anesthesia thus becomes safer because the basic condition "no paresthesia, no anesthesia" becomes irrelevant. In accordance with the basic electrophysiological conditions, a stimulator should have the following properties: (1) adjustable constant current at resistances of 0.5-10 kOhm; (2) monophasic square-wave initial impulse; (3) impulse duration selectable (0.1 ms + 1 ms, and exactly adjustable; (4) impulse amplitude (0-5 mA) exactly adjusted, unequivocal scale graduation or current indicator, in particular in the range of 0.05-1.0 mA; (5) impulse frequency 1-2 (-3) Hz; (6) alarm at high impedance and check on electrical circuit; (7) battery test (indication of battery voltage); (8) unequivocal assignment of load end; (9) high-quality connecting cable and plug; and availability of (10) instructions for use with relevant parameters (tolerated variations, steady-state characteristic curves, etc.).

The effect of spinal anesthesia with barbotage versus without barbotage on the spread of analgesia was investigated. For comparison, hyper- and isobaric bupivacaine 0.5% with adrenaline 1:200,000 was used. MATERIAL AND METHODS. Barbotage was accomplished as follows: after lumbar puncture 0.5 ml CSF was aspirated into the local anesthetic solution, followed by reinjection of 1.0 ml of the solution. This process was repeated six times. Sixty patients who were scheduled for urological or lower limb surgery under spinal anesthesia were selected for this study. Patients were each arbitrarily assigned to one of four groups (isobaric and hyperbaric, without and with barbotage). RESULTS. There was no statistically significant difference in the maximum level of sensory analgesia. The mean maximum level of sensory analgesia reached T9 (group 1), T8 (group 2), T9 (group 3) and T8 (group 4). Time to highest dermatome was significantly shorter with barbotage (groups 1-4: 19.0 min, 13.0 min, 18.7 min, 12.3 min). Times for regression of analgesia to T12 (mean maximum duration) were 142 (+/- 54.9) min, 164 (+/- 29.7) min, 130 (+/- 40.4) min and 144 (+/- 36.2) min (groups 1-4). Motor block grade 3 (Bromage) was achieved in significantly shorter times with barbotage than without. The shortest onset time was recorded with isobaric bupivacaine. The onset time of a complete motor block was 12.5 (+/- 5.5) min in group 1, 6.1 (+/- 2.9) min in group 2, 15.8 (+/- 4.7) min in group 3, and 11.7 (+/- 5.1) min in group 4. CONCLUSIONS. The results showed no significant differences between the maximum segmental sensory levels or duration of anesthesia observed with isobaric and with hyperbaric bupivacaine (with and without barbotage). Sufficient analgesia was obtained with barbotage and without barbotage. Uncontrolled cephalad spread of spinal anesthesia was not observed. Barbotage has the advantage of shortening time for spread to highest dermatome and the time to onset of complete motor block.

Electrical nerve stimulation is a useful tool in regional anesthesia; it assists in locating the nerves. This investigation deals with electrical resistances at adhesive electrodes attached to the skin. The influence of external electrical resistance on the stimulating impulse is demonstrated. A new type of nerve stimulator is described; which integrates a measuring device that indicates the electrical impulse actually flowing in the patient. With this device, relationships between stimulating impulse, intensity of muscle contraction, and distance of the puncture cannula from the nerve can be assessed. MATERIALS AND METHODS. The electrical curve I = f (R) was determined using 3 different nerve stimulators (R = 1 - 15k omega). On each of five test persons, five adhesive electrodes were attached to the skin 10 cm apart. The resistance was assessed between these electrodes and a subcutaneously inserted puncture needle. The right and left brachial plexuses of the 5 subjects were punctured, using the axillary approach. A synchronized video camera simultaneously recorded the following values: (1) electrical impulse; (2) corresponding muscle contraction; and (3) the position of the puncture cannula. A scale ranging from 0-5 was applied to define the strength of the muscle contractions. RESULTS. The external resistance as measured under clinical conditions may limit the output impulse of nerve stimulators. In this case, the exerting impulse is lower than that indicated by the appliance. This error can only be identified using an impulse-measuring device. Nerve stimulators not equipped with a measuring device increase the risk of malpuncture, potentially resulting in nerve lesions. Skin resistance at adhesive electrodes varied from patient to patient within a range of 1.1 to 8.2 K omega. Preparing the skin appropriately (wiping with sandpaper) decreased the resistance by only 6% during the first 30 min. Within a distance of 50 cm to the puncture needle, the position of the adhesive electrode did not play a significant role. Axillary puncture of the brachial plexus resulted in the following values: (1) A stimulating impulse (cross-wave) of 1 mA and 1 ms exerted at a distance of 4 mm to the nerve induced a contraction of strength 3. (2) Reducing the impulse at this site by one-half (0.55 mA) resulted in just-visible contractions (strength 1). (3) Advancing the cannula at a stimulating impulse of 0.55 mA inside the neurovascular sheath again produced contractions of strength 3. (4) Performing the puncture with a blunt needle and tracing a distinct resistance, the impulse of 0.6 mA elicited contractions of strength 2. The needle tip was still outside the vascular nerve sheath. If this resistance was overcome and the needle tip lay inside the neurovascular sheath, the impulse could be reduced by one-half (0.32 mA) to produce contractions of strength 2.

The authors were interested to find whether the course of sensory and motor blockade in isobaric spinal anesthesia was determined by the dose or the volume of the anesthetic agent. In a randomized double-blind study in 60 patients, each underwent isobaric spinal anesthesia with 17.5 mg bupivacaine. In three groups of 20 patients, this dose was administered as 3.5 mg bupivacaine 0.5%, 7 ml bupivacaine 0.25% or 10 ml bupivacaine 0.175%. The development, spread and regression of sensory block (anesthesia, analgesia) and motor block (Bromage scale, rectus abdominis muscle test) were determined. The clinical data recorded in the three groups were comparable. The rate of development, the maximal spread or intensity, and the regression of sensory and motor blockade did not differ in the three groups. The only difference was that the complete regression was shorter following 10 ml bupivacaine 0.175% (P less than 0.05). It is therefore concluded that the dose, and not the volume, determines the course of sensory and motor blockade of isobaric spinal anesthesia.

In a prospective study, 100 patients who underwent general surgical or urological operations under spinal anesthesia were examined to determine whether there was a relation between the anesthesia and postoperative hearing loss. Audiograms were performed preoperatively and as the 1st, 2nd, 3rd, and 5th postoperative days. It was found that 16 patients had impairment of hearing. The average ages of these patients were similar to those of the total population. The hearing loss was typical: only the frequencies between 125 and 2000 Hz were affected. It began on the 2nd day after spinal anesthesia and disappeared within 3 days without special therapy. The cause of this typical hearing loss after spinal anesthesia is a drop in cerebrospinal fluid pressure transmitted to the perilymph via the cochlear aqueduct. The change in the endoperilymphatic pressure difference results in a change in the oscillation of the basilar membrane. Because 16% of patients may suffer hearing loss after spinal anesthesia, it seems reasonable from a medicolegal point of view to explain the possibility of defective hearing to the patient.

Many anesthesiologists prefer epidural anesthesia for cesarean section because of the potential risks of general anesthesia such as Mendelson's syndrome. For this indication, the local anesthetic of first choice is the long-acting substance bupivacaine. The aim of the following study was to determine maternal and neonatal plasma concentrations of bupivacaine 0.5% following epidural anesthesia for cesarean section in order to give critical statements about the systemic toxicity of the local anesthetic. MATERIALS and METHODS. Central venous blood samples were collected for bupivacaine analysis (gas chromatography) in 15 patients (Table 1) undergoing cesarean section with epidural anesthesia over a period of 60 min after injection of 14 to 23 ml bupivacaine 0.5%. Six of these patients had received the epidural anesthesia earlier to relieve labor pain. Before administering the anesthetic dose, a blood sample was taken to determine the baseline value. Immediately after cord clamping, blood sampling was done to determine bupivacaine concentrations in the umbilical artery and vein. Apgar scores and blood gases were also checked and compared with those of neonates born by cesarean section under general anesthesia. RESULTS. Ten to 15 min following epidural application of 70 to 115 mg bupivacaine (mean = 99 mg), peak plasma concentrations occurred (mean = 0.41 micrograms/ml) The maximum plasma level of 0.7 micrograms/ml bupivacaine was found in a patient who had received epidural anesthesia for pain relief during labor. In this case, the baseline bupivacaine level after several epidural injections (125 mg in 15 h) before the anesthetic dose for cesarean section was 0.2 micrograms/ml. Immediately after delivery the mean plasma bupivacaine concentrations in the umbilical vein and artery were 0.11 micrograms/ml and 0.07 micrograms/ml respectively. Apgar scores and blood gas analyses showed no significant difference between neonates born by cesarean section under regional or general anesthesia. DISCUSSION. Using bupivacaine 0.5% for epidural anesthesia for cesarean section, we found maternal and neonatal plasma concentrations of the local anesthetic far below the accepted threshold level for producing systemic toxic reactions. In contrast to others, we obtained good analgesia and sufficient motor blockade accompanied by low plasma levels. In our opinion, there is no need to use 0.75% bupivacaine, especially since peak plasma concentrations of more than 2 micrograms/ml occur shortly after its epidural administration.

We estimated in this study the efficacy of axillary plexus blockade with 60 ml prilocaine 0.5% (300 mg). Following electrostimulation of the median, radial or ulnar nerve (depending on the area of the hand to be operated on), we injected prilocaine in two groups of patients (large volume group, 60 ml prilocaine 0.5% in 20 s; n = 114 patients; normal volume group, 40 ml prilocaine 1% in 20 s; n = 30 patients). Anesthesia of the median and ulnar nerves was virtually complete in all patients, but anesthesia of the radial and musculocutaneous nerves was complete in only 67% (radial) and 75% (musculocutaneous) in the group with normal injection volume. The injection of a larger volume but a lower concentration of prilocaine (300 mg) achieved better anesthesia of the radial (81%) and musculocutaneous (92%) nerves by 30-60 min after the injection. This difference was significant (p less than 0.05). The measurement of higher subfascial pressure in the axillary plexus following the larger volume of 60 ml than after 40 ml could explain the improved efficacy in overcoming anatomical hindrances in the plexus space. Estimation of the prilocaine concentration in the central venous blood 120 min after injection did not reveal different plasma concentrations in the two groups. The plasma concentrations were far below toxic levels. Only the time of plasma peak was earlier in the group with the larger volume, which was attributed to the larger area of diffusion of the vascular system in the plexus space.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous regional anesthesia (IVRA) of the foot is a rarely used but alternative method to other regional techniques and general anesthesia, especially when operating on the distal portion of the lower limb. The present report describes our method and experience with this type of anesthesia in approximately 500 patients, including pharmacokinetic and -dynamic aspects. MATERIALS AND METHODS. Pharmacological studies were performed in 17 orthopedic outpatients undergoing operations on the foot following an IVRA technique with prilocaine. A plastic cannula was inserted into a peripheral vein of the forefoot and a pneumatic tourniquet (350 mm Hg) applied proximally and close to the malleoli after achieving exsanguination with an Esmarch bandage. If there was no sufficient analgesia (pinprick testing) 5 min after injection of 200 mg prilocaine, IVRA was supplemented with another 100 mg of local anesthetic. Peripheral venous blood samples were collected at short intervals for up to 2 h before and after cuff release to determine total plasma concentrations of prilocaine (HPLC) and the degree of methemoglobinemia (CO-Oximeter). RESULTS. Administration of 200-300 mg prilocaine resulted in complete analgesia in 15 of 17 cases that was sufficient for operations lasting up to 85 min. The tourniquet was tolerated for up to 105 min without any complaints. Plasma concentrations after 200 (n = 12) and 300 mg prilocaine (n = 3) peaked between 10 and 20 min after cuff release, respectively, with maximum levels of 0.96 micrograms/ml (means = 0.56 micrograms/ml) and 1.45 micrograms/ml. The extent of methemoglobin formation was low (maximum 3.8% of total hemoglobin). DISCUSSION. In addition to conventional anesthetic techniques, IVRA deserves a firm place in modern anesthesiological practice and should be used more widely. In order to avoid systemic toxic reactions, the use of prilocaine is recommended. Prolocaine plasma concentrations and methemoglobin formation were both far below toxic levels. Failure of IVRA was probably caused by premature outflow of the local anesthetic solution, as shown by the course of prilocaine plasma concentrations and methemoglobinemia.