Regional-Anaesthesie最新文献

In a prospective study spinal anesthesia was performed in 500 patients (338 male and 162 female patients between 16 and 91 years of age: mean 46 years), with a total number of 603 spinal anesthetics. In all cases a 22G Whitacre needle was used. All patients were mobilized from the day of the operation onward and visited 4 days later by the interviewer and asked about any symptoms, especially headache. Mild postspinal headache occurred in 11 cases (1.8% of total), all in patients younger than 50 years of age and more in women. There were 6 patients among the 11 who did not need specific therapy their headache; for the others antipyretic analgesics, adequate hydration and/or bedrest were satisfactory. The study shows that the incidence of postspinal headache was significantly reduced by the use of Whitacre's pencil-point needle in comparison with findings reported in the literature.

This study was undertaken to develop a time- and cost-effective method for the detection of lidocaine, mepivacaine, prilocaine, bupivacaine, and etidocaine by HPLC/UV. The chromatographic system consisted of a C18-column (300 x 3.9 mm) for reversed-phase chromatography and a mobile phase of 30% acetonitrile and 70% 0.05 M sodium phosphate buffer. For the analysis of lidocaine, mepivacaine, and prilocaine, the buffer was adjusted to pH 5.8. The buffer for the analysis of bupivacaine and etidocaine was adjusted to pH 3.5. The flow rate was 1 ml/min. UV detection took place at a wavelength of 210 nm. All blood samples were taken from a central venous line. After plasma separation, 1 microgram (100 microliters) of internal standard was added to 1 ml plasma. The samples were alkalized and extracted with ether, followed by the extraction of the organic phase in 250 microliters 0.05 N sulphuric acid; 50 microliters of this solution was injected into the system. The chromatographic system allowed the separation of bupivacaine and etidocaine (pH 3.5) as well as lidocaine and mepivacaine or prilocaine (pH 5.8). Separation of prilocaine and mepivacaine in one run was not satisfactory. Recovery rates for all local anesthetic substances were about 90%, standard variations below 3%, and coefficients of variation below 2%. The detection limit was about 30 ng/ml. The method is suitable for clinical practice. Only minor methodological modifications are necessary for the detection of the amide local anesthetics in current clinical use.

Pudendal block is a well established method of achieving analgesia during the second stage of labor. Whenever a large amount of a local anesthetic has to be injected in well vascularized tissue, local anesthetic drugs with low systemic toxicity should be used, to minimize side effects. This means that prilocaine is the drug of choice. It is well known that the metabolites of prilocaine induce methemoglobinemia, and thus the question arises as to whether the methemoglobinemia affects the fetus. PATIENTS AND METHODS. Pudendal block was achieved with 2 x 10 ml prilocaine 1% in each of 17 mothers. Plasma concentrations of the local anesthetic in the second stage of labor were determined by gas chromatography in blood samples drawn from the mother and the newborn at the moment of childbirth. In addition, the time course of methemoglobinemia was determined by capillary blood samples from the neonate up to 6 h. To evaluate methemoglobinemia in the newborn, 125 microliters heparinized capillary blood was diluted with 200 microliters 0.9% sodium chloride; methemoglobin was detected by absorbance spectrometry. RESULTS. Before the pudendal block maternal methemoglobin concentrations were about 0.2% of the total hemoglobin concentration and within the physiological range. At the moment of delivery it was increased only to a small extent, without statistical significance. In the neonates mean methemoglobin concentrations were about 1% of total hemoglobin immediately after delivery, increasing up to 1.8% in the next 2 h and then decreasing continuously in all. At the moment of childbirth maternal mean prilocaine concentrations were 0.57 micrograms/ml on an average and 0.29 micrograms/ml in the newborn. DISCUSSION. With respect to systemic toxicity, prilocaine is the drug of choice in local anesthetic procedures when a long duration of anesthesia is not required; it guarantees short latency and adequate relief of pain. Methemoglobinemia induced by its metabolites is not a contraindication for its use in humans. Formerly prilocaine was judged to be contraindicated in pregnant women during delivery because of the small redox capacity of fetal erythrocytes. Our study, however, demonstrates that 200 mg prilocaine for pudendal block does not induce methemoglobinemia in newborns to any significant extent. One explanation for this may be the increased renal elimination of local anesthetics in newborns and the low fetomaternal ratio.

After standard preparation, the catheter is preferably inserted in a sitting position. A test dose of 4 ml etidocaine 1% is injected, initially followed by 1 ml per segment of the total calculated analgesic dose. Analgesic spread, blood pressure, and pulse are checked every 2 min. If a sufficient effect is not reached within 20 min, a further 2 ml per segment is injected. The patient is sedated in the operating room with diazepam, droperidol, or chlorpromazine and receives 6-8 l O2 during spontaneous respiration via a Hudson mask. The epidural catheter is left in place for postoperative analgesia. Intubation is used only as required. Of a total of 52 patients, 31 (60%) did not require intubation, 24 (46%) were age 70 or older, and 31 (60%) were classified as ASA risk group III-IV. Thirty-three of all the procedures (63%) involved upper abdominal surgery (liver, gallbladder) and the majority of these received thoracic (Th 9-10) punctures, with the catheter inserted 5 cm in the epidural space; 88% were punctured medially and 12% laterally. The most frequent complications were bradycardia and hypotension. Respiratory arrest and aspiration were not seen. Thoracic epidural catheter anesthesia can be carried out with or without intubation and with a minimum of complications in selected procedures. Postoperative analgesia is an important advantage.

The structure of the spinal dura mater and the consequences of puncturing the dural tissue with different types of spinal needles were examined. There is no uniformly longitudinal parallel arrangement of dural fibers in human lumbar dura mater from the segments L3-5, but as shown in both scanning electron microscope imaging and polarized light microscopy the small collagenous fibrils are connected by cross-linked bridges. After perforation with Whitacre's pencil-point needle a kind of double layer membrane surrounds the puncture hole and might be responsible for the rearrangement of dural fibers and sealing of the hole after removal of the needle, like wings closing over each other (curtain-effect). This double layer membrane was not seen after dural puncture with sharp Quincke-bevelled needles.

Space-occupying subarachnoid bleeding after atraumatic puncture of the spinal canal for spinal anesthesia in a patient with no coagulation disorders or anticoagulant therapy is described. The hematoma was caused by puncturing a previously undiagnosed small spinal ependymoma. A thorough and specific preoperative evaluation is of importance to minimize the risks associated with spinal anesthesia.

It has not yet been clarified whether prilocaine-induced methemoglobinemia is a problem in patients with chronic anemia. We therefore performed supraclavicular brachial blockade for upper limb surgery (6 mg/kg prilocaine 2% + 0.1 IU vasopressin/ml) in ten female patients with chronic renal failure (mean Hb 8.19%) requiring hemodialysis. Before the blockade, a catheter was inserted into the opposite internal jugular vein and blood samples were drawn before and 10, 15, 20, 30, 45, 60, 90, 120 and 180 min after injection. Plasma prilocaine concentrations and methemoglobin levels were within the ranges measured by other authors in healthy patients. There was no correlation between plasma prilocaine levels and methemoglobinemia. We therefore consider prilocaine to be a safe local anesthetic in patients with renal failure and chronic anemia.

A chronic subdural hematoma was observed 4 weeks after spinal anesthesia. The 70-year-old patient complained of severe, long-lasting headache soon after lumbar puncture. The later symptoms of hemiparesis and aphasia were first misinterpreted as a cerebral vascular accident. After evacuation of the hematoma the patient recovered. Long-lasting, severe headaches after lumbar puncture may be caused by a chronic subdural hematoma, a very rare complication. Risk groups are elderly patients and alcoholics, but every age group can be affected, including parturient women who deliver under spinal anesthesia. The diagnostic procedure of choice is computerized tomography (CAT). The application of contrast medium might be necessary if the CAT scan appears suspicious for a hematoma with the same density as the brain tissue. Because this complication is so rare informing the patient before spinal anesthesia does not seem to be necessary. According to expert opinions, a connection between lumbar puncture and subdural hematoma should be possible. In elderly patients and alcoholics, a pre-existing subdural hematoma may be possibly present.

Tachyphylaxis to local anesthetics is defined as decrease in duration, segmental spread, or intensity of a regional block after repeated doses of equal size, i.e. to maintain a given level of effect the dose has to be increased. In contrast, time-dependent variations in pain or circadian changes in the duration of local anesthetic action only simulate the occurrence of tachyphylaxis (pseudotachyphylaxis). Tachyphylaxis appears neither to be linked to structural (ester vs amide) or pharmacological properties of the local anesthetics (short- vs long-acting) nor to technique (surface anesthesia, conduction block, spinal, caudal, or epidural anesthesia, brachial plexus block) or mode of administration (intermittent vs continuous). There is even disagreement about the clinical significance of tachyphylaxis because some authors found it in almost every patient, others less often whereas a third group did not find tachyphylaxis at all. The mechanisms underlying tachyphylaxis are open to debate. Changes in pharmacokinetics (local alterations of disposition and absorption; decrease of perineural pH) and pharmacodynamics (antagonistic effects of nucleotides or increased sodium concentration; increase in afferent input) have been implicated. None of the theoretical considerations presented are strong enough to explain tachyphylaxis. However, results from isolated nerve preparations suggest that pharmacokinetics rather than pharmacodynamics might play a role in the development of tachyphylaxis.

Local and regional anesthesia, especially peridural anesthesia, is a rarely used method in pediatric anesthesia. That cannot be explained by children's physis, since it shows in general neither a different margin of therapeutic safety nor a different effect/side-effect ratio than in adult. Nevertheless, psychologic alteration of children through operation and anesthesia necessitate simultaneous endotracheal narcosis during peridural anesthesia. The following characteristics of regional anesthesia in children should be regarded: The younger the child the higher is the ratio between extracellular water and body weight. Thus higher doses of local anesthetics in relation to body weight can be applied. The smaller diameters of children's nerves support diffusion of local anesthetics and, therefore, allow the use of lower concentrations. Increased perfusion of tissues and high cardiac output lead to rapid resorption and accelerated increase of anesthetic blood levels. This disadvantage can be avoided by use of lower concentrations of anesthetics. Even an extended sympathetic block during peridural anesthesia hardly causes any negative effect on circulatory parameters. We performed thoracic epidural anesthesia during thoracic and upper abdominal surgery in 40 5-15-year-old children. In many of the patients additional risks had already occurred through atelectasis or lung fibrosis. Before introducing the epidural catheter we always carried out endotracheal anesthesia with relaxation to achieve perfect conditions for the puncture. This puncture was made between Th 6 and 10, mostly between Th 7/8, the patient lying on one side. An extension of analgesia between Th 3 and Th 12 was intended, which, however, could not be controlled because of simultaneous endotracheal anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)