Biomedical subjects

J Biscoping

Publications and source records attributed to J Biscoping.

At least 37 records · Page 2Linked to original sources

PubMed1991

[Microbiological care of ventilated intensive care patients. Feasibility of diagnosis and therapy of pulmonary infection].

Pulmonary infections are the most life-threatening infections in mechanically ventilated patients. Methods to avoid these infections by prophylactic systemic or local administration of antibiotics may promote resistance and selection of distinct groups of pathogens. In mechanically ventilated patients we studied the impact of early diagnosis and specific therapy on the prevention of pulmonary infections. Due to the very short interval between colonization and infection, daily microscopic and microbiologic examinations of tracheobronchial secretions proved to be essential for early and successful therapy and even prevention of pulmonary infections. PATIENTS AND METHODS. The present study comprised a total of 190 patients admitted to the surgical intensive care unit who required mechanical ventilation for a period of at least 48 h: 56 were admitted for multiple trauma; 38 had peritonitis; and the remainder had postoperative complications such as renal failure, cardiac problems, septicemia or pneumonia. Multitraumatized patients (16.5 days) and those with peritonitis (13.8 days) needed the most extensive ventilatory support. After admission antibiotic therapy was started with a second-generation cephalosporin or amoxicillin/clavulanic acid. Further antibiotic treatment was directed strictly against the isolated pathogens. Tracheobronchial secretions were monitored daily by microscopy and cultures. Microscopic evaluation was essential to discriminate between colonization and inflammation, and often indicated the infective agent. If infections were suspected provisional antibiograms were performed on the material. This procedure allowed a specific antibiotic treatment to be initiated 8-12 h later. In patients with pulmonary infections, additional bronchoscopic material was taken in order to correlate these findings with those gained from the tracheobronchial secretions. RESULTS. In 85% of cases massive colonization of the trachea with Pseudomonas aeruginosa, enterobacteria, Staphylococcus aureus or Streptococcus pneumoniae resulted in pulmonary infections 24-48 h later. The reduced virulence of Pseudomonas species (non-aeruginosa) and Acinetobacter species is reflected by an infection rate of 50% and an extended period of time to establish an infection (2-4 days). Only 30% of patients highly contaminated with Candida developed pulmonary infections after 3-6 days. A fair correlation (86%) was found between pathogens isolated in tracheobronchial secretions and bronchoscopic material. In the population studied, 68 patients (35.7%) developed pulmonary infections, 32 of them pneumonia (16.8%), and the others purulent tracheobronchitis with fever. Both groups were treated with antibiotics. Patients with multiple trauma, often accompanied by lung contusion, were most frequently affected. In 59 patients (87%) pulmonary infections were treated successfully by specific antibiotic therapy; 9 patients died so rapidly, that the pulmonary complication could not account for the fatal outcome. In 38 patients with massive contamination of the tracheobronchial system by enterobacteria, Pseudomonas aeruginosa or Staph. aureus, progression from colonization to infection was prevented by early administration of specific therapy. CONCLUSIONS. Because pulmonary infections in most cases arise very soon after pathogens have gained access to the tracheobronchial system daily monitoring of tracheobronchial secretions is required for early initiation of specific therapy.

Adolescent↗

PubMed1991

[Pharmacokinetic studies of blood protein binding of bupivacaine following acute preoperative hemodilution].

This randomized study was designed to determine the effects of isovolemic hemodilution and lumbar epidural anesthesia on plasma concentrations of bupivacaine in patients scheduled for endoprosthetic hip surgery. PATIENTS, MATERIALS AND METHODS. The patients were randomly assigned to two groups. In a hemodilution group (n = 15), which included patients undergoing lumbar epidural anesthesia following isovolemic hemodilution (15 ml/kg body weight), withdrawn blood was substituted by colloidal solution (hydroxyethyl starch solution 6%, 450/0.7; ratio of replacement 1:1). Controls were 15 patients who were not subjected to isovolemic hemodilution; epidural anesthesia only was performed. Both groups had identical fluid pretreatment (1000 ml Ringer's solution) before injection of the epidural bupivacaine dose (mean 14 ml, 0.75%); central venous blood samples were drawn at short intervals over 180 min. Both, the total plasma concentrations and the free bupivacaine fractions were determined by HPLC and ultrafiltration. RESULTS. Peak bupivacaine plasma levels (mean 1.30 microgram/ml) were found 10 min after application of the analgesic dose in the control patients. In contrast, in hemodiluted patients mean maximum plasma levels of bupivacaine were measured between the 20th and 30th min, with peak levels of only 0.75 microgram/ml plasma. The unbound bupivacaine levels were not significantly different in both groups over the entire measuring period despite the differing total bupivacaine concentrations. Therefore, protein binding of bupivacaine was about 6% lower in the hemodilution group, especially during the period shortly after injection. DISCUSSION. We conclude that isovolemic hemodilution leads to lower plasma bupivacaine concentrations after epidural anesthesia, probably due to an increased volume of distribution. Protein binding of bupivacaine is reduced by hemodilution; the free, non-protein-bound concentrations of local anesthetic were not associated with any systemic side effects in this study.

Aged↗

PubMed1991

[The use of ketamine and midazolam for analgesia and sedation in ventilated patients subject to obligatory treatment with catecholamines].

This study was undertaken to compare two regimens for analgesic sedation in intensive care patients with exogenous catecholamine therapy, giving special regard to catecholamine demand and hemodynamic parameters. A total of 20 ventilated patients in a surgical intensive care unit were investigated in a prospectively randomized design. Exogenous catecholamine therapy with epinephrine and/or norepinephrine was started at systolic pressure (SAP) less than 85 mmHg or mean arterial pressure (MAP) less than 65 mmHg to maintain cardiovascular function. For analgesic sedation, patients received bolus injections of about 0.2 mg/h fentanyl and 2.5 mg/h midazolam (fentanyl group, n = 10) or an infusion of about 50 mg/h ketamine and 2.5 mg/h midazolam by syringe pump (ketamine group, n = 10). Before the investigation, all patients received fentanyl and midazolam. The study period was 48 h. During the course of the study, mean catecholamine dosage increased significantly in the fentanyl group from 12.1 to 16.3 micrograms/min (+33%, P = 0.003). In the ketamine group, mean catecholamine dosage decreased from 43.9 to 38 micrograms/min (-13%, P = 0.19). No significant differences in group levels or time course were observed with regard to MAP, heart rate, cardiac index, pulmonary capillary wedge pressure, and shunt volume. Levels of pulmonary artery pressure (PAP) were comparable in both groups (ketamine group 29 mmHg, fentanyl group 26 mmHg). In time course, PAP increased by about 5 mmHg in the ketamine group but not in the fentanyl group (P = 0.009). The average central venous pressure (CVP) was 12 mmHg in both groups. At the end of the investigation, CVP decreased in the fentanyl group and increased in the ketamine group (P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1990

[Neurologic complication following spinal anesthesia for manual detachment of the placenta].

Long-term paralysis of the lower extremities was observed in a 31-year-old fourth-gravida patient, undergoing a curettage under spinal anaesthesia because of placenta accreta. The patient recovered within three days from her neurological signs and symptoms, consisting of complete paresis of the hip and knee flectors and severe headache. Clinical investigations including a neurological examination, spinal puncture, x-ray pictures of the lumbosacral area and haemograms revealed no evidence for an infection, abscess or haematoma. With regard to the fact, that neurological deficiency disappeared completely within three days, it seems probable, that the symptoms were caused by the longer lasting gynaecological position (Steinschnitt-position) during the period of delivery and curettage thereafter.

Adult↗

PubMed1990

[Local anesthetics in the aqueous humor in local anesthesia of the eye].

Local anesthetics injected retrobulbarly are detectable in the aqueous humor. From 40 patients who received a total dose of 140 mg lidocaine, 15 mg bupivacaine, and 30 mg etidocaine, samples of aqueous humor were taken between 30 and 90 minutes after administration (average 57 minutes). The mean lidocaine concentration was 1.02 micrograms/ml, that of bupivacaine 0.075 micrograms/ml. Etidocaine, used only for facial nerve block in front of the ear, could not be detected in the aqueous humor. All three substances were found in the central venous blood. It therefore appears unlikely that any of them are transported via the blood-aqueous barrier, whether actively or passively. Local anesthetics can inhibit corneal cell proliferation and result in lens opacification when administered into the conjunctival sac. It may be that local anesthetics detected in the aqueous humor have similar effects resulting from contact with the cornea and lens.

Aged↗

PubMed1990

Protein binding of prilocaine in human plasma: influence of concentration, pH and temperature.

Protein binding of prilocaine was investigated in vitro under various conditions of changing pH, temperature and total plasma concentration by means of HPLC with UV-detection and ultrafiltration. Whereas changes in temperature (25 degrees C-40 degrees C) and pH (pH 5-pH 10) influenced protein binding markedly, rising plasma concentrations up to 16 micrograms/ml did not affect plasma protein binding significantly. This may be a possible explanation for clinical evidence of low toxicity associated with the use of prilocaine. Discussions concerning protein binding of local anaesthetics should always be based on defined ambient conditions (pH, temperature, concentration).

Aged↗

PubMed1990

[Maternal and neonatal plasma concentrations of bupivacaine during peridural anesthesia for cesarean section].

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.

Adult↗

PubMed1990

[Proposals for standardized documentation of regional anesthetic techniques in anesthesia protocols].

The wide-spread use and wide variety of regional anesthetic procedures makes it essential to insist on careful documentation in the anesthetics record, with special emphasis on technique, effects and complications. With a view to possible medico-legal problems, data should be recorded in considerable detail with each technique applied specified. Documentation is discussed according to the different procedures and their clinical relevance, with various examples.

Abbreviations as Topic↗

PubMed1990

[The significance of the sampling site in the determination of plasma levels of local anesthetics using 0.75% bupivacaine as an example].

Knowledge of the actual concentrations of local anesthetic administered by various techniques is essential requisite when undesirable side effects and possible toxicity of a substance are to be evaluated. Therefore, numerous studies of plasma concentrations have been presented, which were carried out with the additional purpose of analyzing the kinetics of different local anesthetics with respect to limiting-value concentrations in the organism. Despite a sufficient degree of precision in the analysis of amide local anesthetics, it is uncertain whether the results of the different studies are comparable, because blood samples have been taken variously from peripheral veins, central veins or arteries. In the present study changes in bupivacaine concentrations were monitored by means of a standardized method consisting in simultaneous sampling of blood in peripheral veins, central veins and arteries. METHODS. Each of 12 patients undergoing orthopedic hip surgery received average 17 ml bupivacaine (0.75%) via peridural lumbar catheter. After the administration of bupivacaine, blood samples were taken simultaneously from peripheral veins, central veins and arteries at 1, 3, 5, 10, 15, 30, 45, 60, and 90 min after injection. Placement of an arterial cannula and central venous catheter was indicated in all patients (hip-joint revision arthroplasty). Quantitative analysis of bupivacaine concentration was carried out by means of high-pressure liquid chromatography (HPLC). All patients had given their informed consent. RESULTS. All patients showed a rapid increase in bupivacaine concentration in the central venous blood within the first few minutes after administration, the maximum being reached between 3 and 10 min after. A similar course was observed with arterial plasma concentrations; absolute values, however, were an average of 10-20% lower at 15 min following administration. Bupivacaine concentrations in peripheral veins rose more slowly and reached a maximum between 15 and 30 min. At 30 min after peridural application the concentration curves in blood from all three sites were similar. DISCUSSION. In earlier studies the influence of the site of blood sampling has often been underestimated. According to our results, central venous and arterial plasma concentrations correspond closely at all times following peridural application. The observed uniform differences in concentrations at the various sites of sampling can be explained by the fact that pulmonary uptake of local anesthetics causes the lower arterial levels. Especially in the early phase of resorption after administration of local anesthetics, the concentration in peripheral blood does not seem to be representative, because an equilibrium is not established between arterial and central venous blood until 30 min after administration at the earliest. In our opinion the peripheral venous concentrations are unreliable, particularly in the early phases, for the evaluation of unwanted effects or toxicity of local anesthetics, because the initial low values and the delayed increase in these could lead to a false sense of security.

Aged↗

PubMed1990

[Axillary blockade of the brachial plexus using 60 ml prilocaine 0.5% vs. 40 ml prilocaine 1%. A clinical study of 144 patients carried out by the determination of the prilocaine concentration in the central venous blood and by the measurement of the subfascial pressure in the plexus following the injection].

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)

Adult↗

PubMed1990

[Intravenous regional anesthesia of the foot using prilocaine. Clinical aspects, pharmacokinetic and pharmacodynamic studies].

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.

Adolescent↗

PubMed1989

[The sympatho-adrenergic stress reaction in ear surgery using various anesthesia technics].

The aim of the present study was to investigate the effects of various anaesthetic procedures on the endocrine stress responses during ear microsurgical operations. Simple mastoidectomies, radical mastoidectomies and tympano plastics were carried out in 49 patients under the following randomised anaesthetic procedures: Group 1 halothane anaesthesia and retroauricular infiltration anaesthesia with lidocaine and ornipressin (n = 14), Group 2 fentanyl anaesthesia and retroauricular anaesthesia with lidocaine and ornipressin (n = 10), Group 3 fentanyl anaesthesia and retroauricular infiltration anaesthesia with lidocaine and epinephrine (n = 14), and Group 4 retroauricular infiltration anaesthesia with prilocaine and epinephrine (n = 14). The plasma levels of epinephrine, norepinephrine, glucose, lactate and free glycerol were measured in addition to mean arterial pressure (MAP) and heart rate (HR) immediately before anaesthesia, 10 minutes after skin incision, 10 minutes after having started bone drilling, at the end of the operation and 3 hours after operation. All data were subjected to covariance analysis including the age factor. Plasma catecholamine concentrations remained within the normal range during the investigation in patients subjected to general anaesthesia (Groups 1-3). Plasma catecholamines (epinephrine and norepinephrine) increased significantly in Group 4 (retroauricular infiltration anaesthesia). There were no group variabilities with regard to MAP and HR. The plasma levels of epinephrine and norepinephrine demonstrate a direct response to stress followed by a secondary change in glucose, lactate and free glycerol. The beneficial effect of general anaesthesia is documented by normal plasma levels of epinephrine and norepinephrine throughout the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

[Maternal and neonatal bupivacaine plasma levels in peridural anesthesia for relief of labor pain].

Peripheral venous blood samples were drawn for bupivacaine analyses (gas chromatography) from 24 patients under epidural anaesthesia, used to reduce pain caused by contractions. The specimens were taken 10, 20, 30 and up to 45 minutes following a first injection of 11 to 13 ml bupivacaine 0.25%, before, 15 as well as 30 minutes after each repetitive dose and at childbirth. Immediately after cord clamping, blood sampling in the neonate was performed to evaluate bupivacaine concentrations in the umbilical artery and vein. Additionally, apgar scores and blood gas parameters were checked and compared with those of neonates, born without analgesic treatment of their mothers. Using bupivacaine 0.25% (average 12 ml) for epidural anaesthesia, the peak plasma levels (mean = 0.2 micrograms/ml) were found 10 minutes after application of the analgesic dose. In one patient a maximum bupivacaine plasma concentration (0.47 micrograms/ml) was determined 15 minutes after the second repetitive dose of 5 ml bupivacaine 0.25%. Apgar scores and results of blood gas analyses demonstrated no significant difference between neonates born spontaneously under regional anaesthesia or without any analgesic treatment of their mothers, respectively. Using bupivacaine 0.25% in epidural anaesthesia for pain relief in labour, we found maternal and neonatal plasma concentrations of the local anaesthetic drug far below the accepted threshold level which might produce systemic toxic reactions.

Adolescent↗

PubMed1989

[Mother and child stress parameters during cesarean section with general and peridural anesthesia].

This study compared maternal and fetal stress responses during cesarean section in either general anesthesia (GA) or epidural anesthesia (EA). Ten patients received GA with thiopental induction, intubation, and controlled ventilation with nitrous oxide and oxygen. After delivery, anesthesia was supplemented with fentanyl 0.2-0.3 mg. Ten patients received EA via catheter, using bupivacaine 0.5%, and prilocaine or lidocaine 1%. Maternal mean arterial pressure (MAP), HR, and plasma concentrations of epinephrine and norepinephrine (by HPLC/ECD), ADH, ACTH and cortisol (by RIA) were determined before and after induction, after delivery, at the end of the operation and 30 minutes postoperatively. Fetal catecholamine levels in umbilical artery blood were measured immediately after delivery. In addition, fetal blood gas analyses and Apgar scores were compared. Fetal epinephrine was slightly increased in the EA group (EA 132 pg/ml, GA 52 pg/ml). Norepinephrine was similar in both groups (EA 1.218 pg/ml, GA 1.124 pg/ml). Blood gas analyses and Apgar scores were also comparable. A negative correlation was found between norepinephrine and pH values in fetal umbilical artery blood (P = 0.01). Maternal epinephrine levels were lower under EA and below the normal range (EA 23 pg/ml, GA 77 pg/ml, P = 0.002); levels increased during GA and decreased during EA (P = 0.01). No statistical differences were seen in maternal norepinephrine (EA 206 pg/ml, GA 354 pg/ml). MAP was lower during EA (group levels EA 81 mmHg, GA 95 mmHg, P = 0.0002) and HR was higher during GA (group levels EA 89/min, GA 104/min, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1989

[Does the development of methemoglobin in the newborn infant affect the suitability of prilocaine for pudendal anesthesia? A clinical study in the peripartum phase].

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.

Anesthesia, Obstetrical↗

PubMed1989

[The quantitative analysis of amide local anesthetics using high pressure liquid chromatography and ultraviolet detection (HPLC/UV)].

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.

Anesthetics, Local↗

PubMed1989

[Initial experiences with a novel nerve stimulator for use in axillary plexus anesthesia].

The advantages of an electrical nerve stimulator for detection of the axillary neurovascular sheath have been frequently described in the literature and are now well known. In most of these techniques, stimulation is achieved by a fixed electrical voltage and variable amplification. The new nerve stimulator presented here offers the possibility of measuring the current at the site of stimulation ("test" position). PATIENTS AND METHODS. Axillary block was performed in 23 patients undergoing orthopedic surgery. Identification of the neurovascular sheath was first achieved by the "loss of resistance" technique, after which the injection cannula was connected to the new device. Stimulation was started at 1.0 mA. In case of a negative response to stimulation the actual electric current was checked by means of the test position in order to exclude an error in the circuit system. In these cases, the position of the cannula was altered so as to maintain a response at the lowest possible current (less than 0.5 mA). After removal of the inner solid steel stylet of the cannula, the local anesthetic was injected while compressing the distal part of the neurovascular sheath in order to avoid downstream diffusion. RESULTS. All 23 patients were operated upon under axillary block after nerve stimulator control without any additional drugs. Table 2 indicates the lowest stimulation current that still evoked a response. Disturbances in the circuit system were found twice, one caused by a short circuit, the other by a desiccated gel pad on the adhesive electrode. After elimination of the defect, stimulation produced a response. DISCUSSION. Since it is now well known that induction of paresthesias in locating peripheral nerves can cause irreversible lesions, the use of electrical nerve stimulators is preferred to locate the cannula as near as possible to the nerve without direct contact. The mode of operation of the stimulator presented here, which defines the chosen technical starting impulse as well as the actual current, allows much better localization of nerves during local anesthesia. Thus, disturbances in the circuit between nerve stimulator and patient, as shown in the two cases, can be detected. According to our experience, the intensity of stimulation for successful nerve blockade should be approximately 0.5 mA or lower. Consequently, universally applicable stimulating instruments with constant electrical tension should allow fine tuning of the current in 0.1-mA aliquots.

Brachial Plexus↗

PubMed1989

[Local anesthetic level and cardiovascular changes following local anesthesia in cataract operations with 3% mepivacaine].

Are there toxic plasma levels of mepivacaine after local anesthesia for ophthalmic surgery with 3% mepivacaine? What hemodynamic changes occur during injection of the local anesthetics? Fifteen patients undergoing cataract surgery were given 10 ml of mepivacaine (3%) as a local anesthetic regardless of body weight. After inserting an arterial line, blood samples were taken before the beginning of the injection of mepivacaine and after 3, 5, 10, 15, 30, and 60 min. Concentrations of the drug were measured by gas chromatography. During the first 15 min arterial blood pressure and ECG were registered continuously on a multichannel recorder. The maximum mepivacaine plasma levels were estimated after 15 min with a range from 0.28 to 6.95 micrograms/ml (means +/- SD: 4.5 +/- 1.47 micrograms/ml). The blood pressure was elevated over the preoperative value, at the beginning of the evaluation period, but there was no change in the blood-pressure level over the whole period. In 4 patients without known cardiac arrhythmias, ventricular or supraventricular extrasystoles occurred. The mepivacaine plasma levels complied with resorption kinetics, which is an indication that there were few intravascular injections and that the injection technique war correct. On the other hand, in some patients the mepivacaine plasma levels exceeded the toxic level. Even in ophthalmic surgery, local anesthetics should be given in relation to the body weight of the patients. The high blood-pressure levels indicated non-optimal preoperative treatment of the hypertonic patients, which was followed by an intraoperative exacerbation of the blood pressure.

Aged↗