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Biomedical subjects

G Hempelmann

Publications and source records attributed to G Hempelmann.

At least 379 records · Page 21Linked to original sources
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

[Epidural conduction anesthesia versus general anesthesia. A critical evaluation of outcome studies using as examples cesarean section and patients with hip fractures].

In the field of anaesthesiology, outcome studies are undertaken to investigate the influence of different anaesthetic techniques on the intra- and postoperative course of patients in special clinical situations. The design of these studies should follow high methodological standards. In the past, most studies were undertaken in patients during Caesarean section and in the treatment of hip fractures in the elderly. Up to now, results do not clearly indicate the use of certain techniques in concrete clinical situations. Decisions must be made in accordance with clinical aspects, individual experience and in cooperation with the patient and the surgeon.

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

[Perioperative anemia and erythropoiesis].

50 consecutive patients with hip arthroplasty had acute normovolaemic haemodilution and intra- and postoperative autotransfusion using Autotrans, Dideco GmbH. 18 of 50 patients received homologous blood products additionally to autotransfusion (Hb less than 8 g/dl, hemodynamic instability). There was no evidence for coagulation disorders, hypoxia or hypovolaemia during the whole investigation period (until the 10th p.o. day) though in some cases haemoglobin-levels less than 7 g% were accepted. No variations of erythropoietin levels could be observed postoperatively, suggesting that acute anaemia alone does not affect erythropoiesis. Reticulocytes, however, increased significantly from the 4th postoperative day. There was no correlation between number of reticulocytes and erythropoietin levels. Lactate levels stayed within normal range during the whole investigation period thus indicating normal microcirculation. The present data demonstrate that postoperative anaemia can be tolerated even in elder patients if intravascular volume is kept constant (normovolaemia). In accordance with recent literature the course of erythropoietin levels seemed to prove that there was no functional reduction in oxygen-availability.

Anemia↗
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↗
PubMed1990

[Local anesthetic mixtures in various regional anesthesia procedures].

The use of local anaesthetic mixtures in regional anaesthesia has been discussed controversially. This assumption led us to conduct an inquiry on anaesthesiologist opinion on local anaesthetic mixtures. The study was performed on 131 anaesthesiologists answering a questionnaire. It was asked how often and how many procedures of regional anaesthesia were performed, whether local anaesthetic mixtures were used or not, and what were the most common mixtures. Other questions were in what kind of regional anaesthesia mixtures were applied, and which causes led to the use of local anaesthetic mixtures. Local anaesthetic mixtures were used by 70.2% of the anaesthesiologists who responded. Generally, however, parent components were preferred (88.3%). The types of regional anaesthesia in which mixtures were applied, were blockades of plexus brachialis (50.4%), spinal anaesthesia (29.0%), and epidural anaesthesia (28.4%). Locally applied anaesthetic mixtures - in 40.5% a mixture of bupivacaine and prilocaine and in 38.2% a mixture of bupivacaine and mepivacaine - were used in 58.0% because of their short latency and their long duration. In 27.5% the reply was that the anaesthesiologists used such combinations since in these the maximal doses of the parent components were not exceeded. In 22.9% it was argued that mixtures were less toxic than the parent components. On the other hand, the application of local anaesthetic mixtures was rejected because of their unpredictable effect (33.6%), and also to avoid local anaesthetic interactions (13.7%). The results of the inquiry demonstrate that the use of local anaesthetic mixtures in regional anaesthesia is common practice. However, mixing local anaesthetics may produce unpredictable interactions. We conclude that mixtures of local anaesthetics should be used only in exceptional cases.

Anesthesia, Conduction↗
PubMed1989

Early detection of cerebral ischemia during carotid endarterectomy using transcranial Doppler sonography and somatosensory evoked potentials.

Cerebral function during carotid endarterectomy can reliably be monitored using somatosensory evoked potentials (SEP). Transcranial Doppler sonography (TCD) is a noninvasive method providing on-line data about cerebral hemodynamics. The combination of both techniques during carotid surgery is helpful in evaluating the hemodynamic ("input") and the functional ("output") consequences of carotid clamping within a short time. In the present report, combined TCD and SEP monitoring early detected left hemispheric ischemia in a 68-year-old woman subjected to left carotid endarterectomy. The impairment of cerebral perfusion occurred before carotid clamping due to an intraoperative thrombosis of the left internal carotid artery as could be revealed after declamping. A temporary shunt was not inserted. Postoperatively, the patient had a new transient neurological deficit. In this case, TCD correctly indicated cerebral ischemia as confirmed by SEP recording. For carotid artery surgery, combined TCD and SEP may be helpful in detecting those patients who will profit from temporary shunting if this is not done routinely.

Aged↗
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

Effects of thiopentone and etomidate on median nerve somatosensory evoked responses.

Somatosensory evoked potentials (SEP) after median nerve stimulation were recorded in 40 patients during infusion of either 15 mg/kg bw thiopentone or 1 mg/kg bw etomidate (n = 10) within 15 min and after 0.3 mg/kg bw etomidate (n = 20). Marked alterations of SEP waveforms and changes in latencies were observed in all patients. Central conduction time (CCT) was significantly correlated to plasma thiopentone concentration. Infusion of high doses of thiopentone and etomidate was followed by a complete loss of middle and long latency components. Amplitude of the primary cortical SEP N20 was found to be unchanged after thiopentone and to be increased after etomidate, indicating the synchronizing properties of this drug. A pronounced increase in SEP latencies and CCT and waveform alterations have to be considered during hypnotic drug administration in intensive care medicine and intraoperatively.

Adult↗
PubMed1989

Influence of acute volume loading on right ventricular function after cardiopulmonary bypass.

The influence of acute volume loading on right ventricular function immediately after extracorporeal circulation (ECC) was investigated in 25 patients undergoing elective aortocoronary bypass grafting. In addition to commonly monitored hemodynamic variables, right ventricular (RV) ejection fraction (EF) was measured by thermodilution technique using a new fast-response thermodilution catheter. In eight patients with concomitant severe stenosis (greater than 89%) of the right coronary artery (RCA), volume loading was followed by a decreased RVEF and cardiac output. In contrast, RVEF in the 17 patients without diseased RCA increased significantly, with an increase in cardiac output. Duration of aortic cross-clamping (i.e., ischemia) was more pronounced in the group with decreased RVEF due to RCA grafting. Increased end-diastolic volume and decreased RV contractility index indicated that patients with myocardial ischemia during cardiac surgery procedures sometimes were unable to make the adaptations required. We conclude that cardiocirculatory dysfunction associated with ECC may be caused by depressed RV function. Acute volume loading in this situation may lead to further deterioration of myocardial function due to RV failure, a condition which cannot be diagnosed readily at the bedside with the usual monitoring techniques.

Aged↗
PubMed1989

Hemodynamic effects of enoximone in cardiac surgery patients.

Enoximone belongs to a new class of inotropic drugs that are not related either to digitalis or to catecholamines. It acts primarily through selective inhibition of phosphodiesterase III (PDE-III) and has additional vasodilating properties. Hemodynamic effects of intravenously administered enoximone (0.5 mg/kg) were investigated in patients undergoing aortocoronary bypass grafting before and during anesthesia as well as during extracorporeal circulation (ECC). Patients who were impossible to be weaned off ECC without pharmacological support were investigated also. A significant increase in cardiac index and dp/dtmax, a decrease in pulmonary capillary pressure, and a small decrease in mean arterial pressure were the major hemodynamic effects. Heart rate was not changed and no signs of arrhythmia were seen during the entire investigation period. Interactions with the anesthetics used could not be observed in this study. In patients with impaired myocardial performance during weaning from ECC, enoximone seems to be helpful in stabilizing cardiac output and decreasing filling pressure. The mechanism for improvement appears to be enhanced contractility due to its positive inotropic effects, as well as a decrease in left ventricular outflow resistance resulting from peripheral vasodilation.

Cardiac Surgical Procedures↗
PubMed1989

[Hemodynamic effects of the new phosphodiesterase inhibitor enoximone in heart surgery patients].

The new phosphodiesterase-III inhibitor (PDI) enoximone is a non-catecholamine, non-glycoside cardiotonic agent with concomitant vasodilating properties. It has proved beneficial in patients with severe chronic heart failure. The influence of enoximone i.v. on hemodynamics was investigated during cardiac surgery under various conditions. METHODS. A randomized series of 60 patients undergoing elective aorto-coronary bypass grafting were studied. The hemodynamic effects of 0.5 mg/kg enoximone given i.v. as a bolus (30 s) were investigated before anesthesia (n = 10), during anesthesia (n = 10), and during extracorporeal circulation (ECC, n = 10) and compared with those observed in corresponding control groups (n = 10 in each control) of patients who had received saline solution as placebo. Anesthesia was maintained with weight-dependent dosages of fentanyl, midazolam and pancuronium bromide. All patients were invasively monitored by means of a pulmonary artery catheter. Additionally, left ventricular pressure (LVP), left ventricular end-diastolic pressure (LVEDP) and dp/dtmax were measured before the initiation of ECC. During ECC direct vascular effects were investigated with measurement of perfusion pressure and the volume of the oxygenator. RESULTS. Before the induction of anesthesia no significant change in MAP and HR could be observed, whereas CI increased (+20%) and TSR decreased (-24%) significantly. During anesthesia, the injection of enoximone was followed by a significant decrease in MAP only in the 1st min (-17%); baseline level was reached again after 6 min; and HR was slightly increased (+8%). TSR (-31%) and LVEDP (-38%) decreased, whereas CI (+17%) and dp/dtmax (+45%) were increased significantly. During ECC perfusion pressure (-37%) and the volume of the oxygenator (-17%) were significantly decreased, demonstrating direct vasodilating effects on both the arteries and the vein. CONCLUSION. Arterial and venous vasodilation with an increase in myocardial performance (dp/dtmax) resulting in an increase in CI were the predominant hemodynamic effects of enoximone i.v. No arrhythmogenic effects or interactions with the anesthetics used were observed in this study.

Anesthesia↗
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↗