Der Anaesthesist
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In an attempt to develop a noninvasive monitoring technique for patients in the early postoperative period, cutaneous O2 and CO2 pressures (pctO2, pctCO2) were monitored in ten healthy adult volunteers of both sexes (5 male, 5 female, age 29 +/- 5 years, weight 68 +/- 11 kg) who received, in several sessions after a 60-min equilibration period, i.v. bolus doses of fentanyl (3 micrograms/kg and, 60 min later, another 1.5 micrograms/kg), buprenorphine (3 and 1.5 micrograms/kg), naloxone (1.8 and 0.9 micrograms/kg), and the respiratory analeptic amiphenazole (2 and 1 mg/kg) as well as combinations of fentanyl/amiphenazole or buprenorphine/naloxone in the aforementioned dosages. Data were collected and stored by a personal computer using the TCM3 system with a combination electrode for simultaneous measuring of pctO2 and pctCO2 (TINA, Radiometer) at 30-s intervals. The overall observation period was 240 min. Means, standard deviations, and ranges were calculated for individual data and data pooled for 15-min intervals. Groups were compared by means of Student's t-test and analysis of variance. ⋯ As was discussed in detail in a previous communication, monitoring of opiate-induced respiratory depression must be nonstimulant and, preferably, noninvasive. Whereas the precision and/or limitations of monitoring partial oxygen saturations by pulse oximetry is well documented in the literature, knowledge of the value of cutaneous partial pressure monitoring is still limited and controversial for the adult patient population. The present study was performed to define the usefulness of cutaneous blood gas analysis in healthy volunteers receiving opiate dosages well known in recovery room patients. It is concluded that continuous monitoring of pctO2 and pctCO2 can indeed detect opiate-induced respiratory depression in adults. The well-known difference in respiratory pattern for fentanyl and buprenorphine could easily be determined. It was confirmed that naloxone and amiphenazole in the dosage range studied do not influence spontaneous respiration in healthy adults. Thus, the authors are convinced that continuous monitoring of cutaneous partial pressures of oxygen and carbon dioxide is sensitive enough to be used, in combination with pulse oximetry, in a monitoring concept for patients recovering from surgery and anaesthesia. Results in patients undergoing conventional pain management or patient-controlled analgesia with relatively high opiate dosages will be presented in following papers. Concerning the controversy about clinically relevant interactions between fentanyl and amiphenazole or buprenorphine and naloxone, the present study did not confirm any useful antagonism. Whether this is due to limitations of cutaneous monitoring, the difference between volunteers and patients, or pharmacological reasons must be evaluated in further investigations.
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Thiopental is a hypnotic drug that is widely used for the induction of anaesthesia. The mechanism of the short-term action is based on the rapid distribution of the drug, and in contrast to methohexital, the metabolism of thiopental is not relevant in use in conditions of operative anaesthesia. However, in neurotraumatology thiopental is frequently used as continuous infusion for several days to reduce cerebral metabolism. ⋯ The actions of thiopental on global hemodynamics are comparable with the results found in the literature, characterized by a significant reduction in MAP and cardiac output after induction. The hepatic clearance of thiopental found in this study, with an absolute value of 0.21 l/min, is absolutely comparable with the data for total-body clearance reported in the literature. It is concluded that the liver is the only organ responsible for the elimination of thiopental in humans.
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The modified combined plunger pressure and manometer method (KSMM = Kombinierte Stempeldruck-Manometer-Methode) has proved to be a satisfactory alternative to the loss of resistance technique of Dogliotti. The method was tested for practicability and successful identification of the epidural space in 200 patients (80 of them pregnant) by physicians at different stages of their training. It makes it easy for young anaesthetists who are still in training and have not had much experience to learn to identify the epidural space. With this method the experienced operator can make an important contribution to the training of young doctors in epidural anaesthesia without fear of risks and failures.