Anasthesie, Intensivtherapie, Notfallmedizin最新文献

Polyneuropathy of the critically ill patient has gained attention in recent years. The symptoms of muscle weakness and impaired somatosensory perception are more obvious for the observer and recognizable for the conscious patient, if heavy long-term sedation is avoided. The cause of polyneuropathy remains unclear and diagnostic findings are still rare and partly controversial. In five of our patients with multiorgan failure and clinical signs of muscle weakness, cortical somatosensory evoked potentials (SEP) and the evoked electromyogram (EMG) were recorded simultaneously after the stimulation of mixed peripheral nerves to test the functional integrity of the efferent and afferent neuronal pathways. We observed different degrees of SEP and EMG alterations, which were more pronounced in the lower than in the upper extremities and which may be explained by an axonal degeneration. Such a process may be caused by multiple factors and pathophysiological mechanisms. An influence of neostigmine on a reduced EMG response could not be found.

The predictability of the inspiratory and endexpiratory concentrations of the volatile anaesthetics isoflurane and enflurane by pharmacokinetic models was investigated. 67 patients of ASA-classes 1-2 that underwent minor surgical procedures were studied. The pharmacokinetic model consisted of two parts, a model of the anaesthesia machine and a model of the patient. The mean values of the predicted/measured concentrations of isoflurane had an amount of 1.01 +/- 0.13 (inspiratory) and 0.97 +/- 0.13 (endexpiratory), the mean values of enflurane showed a value of 1.00 +/- 0.11 (inspiratory) and 0.97 +/- 0.13 (endexpiratory). The interindividual variances amounted to between 10% and 40% of the variance of all patients. This corresponded to a standard deviation of about 6% (inspiratory) while the endexpiratory concentrations showed a standard deviation about 8% for the average values of every patient.

With the introduction of repetitive or continuous catheter techniques in regional anaesthesia, potential systemic intoxication hazards have increased. Especially high dose techniques such as peridural anaesthesia or plexus brachialis blockade consecutively generate high blood levels. In this study, blood levels collected from 20 patients (36 +/- 19 y, 173 +/- 9 cm, 73 +/- 15 kg) after lumbar epidural anaesthesia with mepivacaine led to the development of a linear open one-compartment-model (VD,ss: 109 l, Cltot: 594 ml/min, t1/2abs: 13 min, t1/2 beta: 149 min). With that model, dosage strategies could be studied via computer simulation. A mepivacaine dosage regimen for lumbar epidural anaesthesia, consisting of 250 mg as an initial bolus dose and an infusion rate of 150 mg/h after 15 min, cumulated to maximum concentrations of 2.5-3.5 micrograms/ml after 150 min. Such an infusion regimen may lead to concentrations of more than 4 micrograms/ml if applied for longer than 4 h. The pharmacokinetic computer simulation proved to be precise and could be compared to the measured blood levels of mepivacaine.

Based on a case report with vaginal hysterectomy, the anaesthetic implications are discussed in a patient with Shy-Drager syndrome, which is a degenerative disease in middle-aged to elderly patients, resulting in autonomic dysfunction. The syndrome is reviewed and the anaesthetic management is described. Adequate cardiovascular monitoring and maintenance of haemodynamic stability are important. The response to sympathomimetic drugs is unpredictable and may be extreme due to denervation hypersensitivity. In the postoperative period, signs of postural hypotension may be severe and require training by elevation of the upper part of the body, fluid therapy, sympathomimetics and fludrocortisone.

Anaesthesia has significant effects on circulation and oxidative metabolism which are closely related to each other. Usually there is a marked reduction of oxygen uptake (VO2) and energy expenditure. A controversial discussion on the effects of the drugs administered and the degree of metabolic depression has continued in the literature fuelled by a lack of studies in patients under standardized conditions. 18 patients (ASA I-II) scheduled for major abdominal surgery were given closed-loop feedback control anaesthesia by quantitative EEG analysis. Group 1 received a total intravenous anaesthesia with methohexital and fentanyl whereas group 2 was given a combined anaesthesia with alfentanil and N2O. The aim of this comparative study was to evaluate the effects of different techniques for general anaesthesia on oxygen uptake and on the cardiovascular system. Preanaesthetic values of VO2 taken after flunitrazepam premedication were slightly below the predicted range determined by indirect calorimetry for basal metabolism. Steady-state general anaesthesia led to an approximately 30% reduction of VO2 for both groups. In contrast to oxygen uptake, blood pressure and especially heart rate were defined by the type of anaesthesia as in the methohexital fentanyl group higher values of both blood pressure and heart rate were observed.

The direct effects of midazolam on isometric force of contraction (Fc) and on transmembrane action potential (AP) in electrically driven right ventricular papillary muscles were investigated. The results were compared with the effects of thiopental. Midazolam (0.01-200 mumol/l) had a concentration-dependent maximal negative inotropic effect of 94 +/- 4% compared with the pre-drug value on the papillary muscles of animals pretreated with reserpine (RES) [7.5 mg/kg b.wt. i.p., 16-18 h prior to the study]. The IC25 and IC50 values were 2.9 mumol/l (2.0-4.5; n = 9) and 12.4 mumol/l (6.5-30; n = 9) respectively. However, on the papillary muscles of untreated animals (nRES) midazolam developed a concentration-dependent positive inotropic effect (maximal 20 +/- 7%). Midazolam at a clinically relevant concentration of 2.8 mumol/l (= 1 microgram/ml; equivalent with the maximum plasma level following a midazolam i.v. bolus injection of 0.15 mg/kg b. wt.) reduced Fc by 15 +/- 3% (p less than 0.05) compared with the pre-drug value on the RES papillary muscles (n = 6) and increased Fc by 3 +/- 0.3% (p less than 0.05) on nRES animals. The resting membrane potential (RMP), the AP amplitude (APA) and the AP duration at 20% (APD20) and 90% (APD90) repolarisation showed no significant differences with midazolam (2.8 mumol/l; n = 5). Thiopental (0.01-200 mumol/l) produced a concentration-dependent maximal negative inotropic effect of 86 +/- 2% compared with the pre-drug value on the papillary muscles of nRES animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of incremental positive end-expiratory pressure (PEEP) on middle cerebral artery (MCA) blood flow velocity and pulsatility index were studied in 20 patients scheduled for minor elective surgery. Transcranial Doppler sonography (TCD) was used to measure systolic (Vsyst) and mean flow velocity (Vmean) and the pulsatility index (PI). Heart rate (HR), mean arterial blood pressure (MAP), end-tidal CO2(PetCO2) and TCD parameters were recorded at control (PEEP = O) and following PEEP of 5 cm H2O, 10 cm H2O and 15 cm H2O for a period of 5 minutes for each PEEP level. Vsyst and Vmean were significantly reduced with each increment of PEEP. PI increased stepwise in response to each PEEP level. MAP decreased with PEEP 10 and 15 while HR and PetCO2 remained constant over time. These data suggest that PEEP-induced decreases in MCA blood flow velocity may represent decreases in CBF due to impairment of the intracranial venous flow if the diameter of the insonated vascular segment remains constant.

Recovery of motor and mental functions were investigated in two groups with 20 young patients each. One group received total intravenous anaesthesia (TIVA) with propofol and alfentanil for urological surgery and the other group received nitrous oxide-oxygen anaesthesia in combination with 1.3 MAC of enflurane for lumbar nucleotomy. The following parameters were investigated before and up to 100 minutes after extubation: simple and discriminating motor activities, vigilance and short and long term memory. --Simple and in discriminating motor actions show a significantly faster recovery was seen in the TIVA group during the first 20 minutes after extubation compared to the enflurane-treated patients. Speech-related functions were particularly inhibited in the inhalational anaesthesia group. After 30 to 40 minutes the propofol-alfentanil group was able to meet all requirements while patients with inhalational anaesthesia needed 80 minutes to reach the same level. Recovery of short and long-term memory was also significantly shorter in the TIVA group. This clearly indicates a faster return of mental and motor functions following total intravenous anaesthesia with propofol and alfentanil. However the large dosages of alfentanil may be a problem with regard to post-anaesthetic respiratory depression. Further studies with larger numbers of patients will be necessary to evaluate the potential side effects of continuous propofol/alfentanil infusion. Presently, safety demands require, at least a sixty-minute post anaesthesia monitoring for patients receiving this new anaesthesia method.

The aim of this study was to evaluate isovolaemic haemodilution (IHD) as a method to reduce the use of homologous blood in high-risk geriatric patients undergoing cardiac surgery. Haemodynamics were continuously assessed in both the systemic and the pulmonary circulation, and, in addition, the EEG was continuously analysed by on-line power spectrum analysis. The mean blood use in this series could be reduced from 4.2 units to 1.12 units (67 patients). 73% of the patients needed intraoperatively no blood at all. The haemodynamic response to haemodilution in these patients consisted of an increase in stroke volume by 9%, and decreases in systemic vascular resistance and myocardial-O2 consumption (as reflected by the rate/pressure product RPP) by 9% and 10%, respectively. At the same time, O2 transport capacity increased by 8%. No signs of oxygen balance impairment were found in either ECG or EEG during haemodilution. It is concluded that moderate IHD can be safely performed in the geriatric cardiac patient and represents a useful method to reduce homologous blood use in these patients.