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Biomedical subjects

E Kochs

Publications and source records attributed to E Kochs.

At least 19 recordsLinked to original sources
PubMed2007

Teletherapeutic drug administration by long distance closed-loop control of propofol.

BACKGROUND: The objective of this pilot study was to investigate the feasibility of an EEG-controlled closed-loop administration of propofol over a long distance of about 200 km. METHODS: We performed a teletherapeutic propofol infusion during total intravenous anaesthesia with propofol in 11 patients undergoing general surgery. The teletherapeutic system consisted of a computer at the patient site in Munich and a computer at the control site in Erlangen, which were connected via the internet through a virtual private network. The patient's EEG signal was sent to the control site computer, where the median frequency (MEF) of the EEG power spectrum was calculated. The propofol infusion, determined by a model-based adaptive feedback algorithm to maintain a MEF of 1.5 to 2 Hz, was sent to the patient site computer connected to the infusion pump. The quality of the control was assessed by the performance error defined as the percentage deviation of the measured MEF from the set point and the necessity of interventions by the anaesthetist at the patient site. RESULTS: During closed-loop administration of propofol [83 (52) min] the median performance error of the system was - 4.6 (4.4)% and the median absolute performance error was 18.8 (5.7)%. From a total number of 10 905 transmitted EEG epochs, there were five epochs with transmission errors, without further consequences for drug control. In one patient, teletherapy was stopped because the internet connection was interrupted. CONCLUSIONS: Teletherapeutic drug administration could be realized over a longer distance. Further studies have to investigate the practicability and safety of teletherapeutic drug control in anaesthesia.

Adolescent↗
PubMed2007

Corresponding minimum alveolar concentrations of isoflurane and isoflurane/nitrous oxide have divergent effects on thalamic nociceptive signalling.

BACKGROUND: Suppression of nociceptive signalling in the thalamus is considered to contribute significantly to the anaesthetic state. Assuming additivity of anaesthetic mixtures, our study assessed the effects of corresponding minimum alveolar concentrations (MACs) of isoflurane and isoflurane/nitrous oxide on thalamic nociceptive signalling. METHODS: Nociceptive response activity (elicited by controlled radiant heat stimuli applied to cutaneous receptive fields) of single thalamic neurons was compared in rats anaesthetized at approximately 1.1 and approximately 1.4 MAC isoflurane with that at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide. RESULTS: Under baseline anaesthesia ( approximately 0.9 MAC isoflurane), noxious stimulation elicited excitatory responses in all neurons (n = 19). These responses were uniformly suppressed at approximately 1.1 and approximately 1.4 MAC isoflurane. In contrast, at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide, excitatory responses no different to baseline were still present in 64 and 37% of the neurons, respectively. CONCLUSIONS: These data demonstrate a pronounced nitrous oxide-induced response variability. It appears that, with respect to thalamic transfer of nociceptive information, the interaction of isoflurane and nitrous oxide may not be compatible with the concept of additivity and that the antinociceptive potency of nitrous oxide is considerably less than previously reported.

Anesthetics, Combined↗
PubMed2005

Concurrent recording of AEP, SSEP and EEG parameters during anaesthesia: a factor analysis.

BACKGROUND: Spontaneous EEG, mid-latency auditory evoked potentials (AEP) and somatosensory evoked potentials (SSEP) have been used to monitor anaesthesia. This poses the question as to whether or not EEG, AEP and SSEP vary in parallel with varying conditions during surgical anaesthesia. METHODS: A total of 81 variables (31 EEG, 22 SSEP, 28 AEP) were simultaneously recorded in 48 surgical patients during anaesthesia. A total of 307 cases of the 81 variables in stable anaesthetic states were recorded. A factor analysis was performed for this data set. RESULTS: Sixteen variables were excluded because of multicollinearity. We extracted 13 factors with eigenvalues >1, representing 78.3% of the total variance, from the remaining 65 x 307 matrix. The first three factors represented 12%, 11% and 10% of the total variance. Factor 1 had only significant loadings from EEG variables, factor 2 only significant loadings from AEP variables and factor 3 only significant loadings from SSEP variables. CONCLUSION: EEG, AEP and SSEP measure different aspects of neural processing during anaesthesia. This gives rise to the hypothesis that simultaneous monitoring of these quantities may give additional information compared with the monitoring of each quantity alone.

Anesthesia, General↗
PubMed2005

Long-term effects of hypothermia on neuronal cell death and the concentration of apoptotic proteins after incomplete cerebral ischemia and reperfusion in rats.

BACKGROUND: The present study investigates the long-term effects of postischemic hypothermia on neuronal cell damage and concentration changes of apoptotic proteins after cerebral ischemia. METHODS: Sixty-four Sprague-Dawley rats were anesthetized, intubated and ventilated with 2.0 Vol% isoflurane and 70% N2O/O2. After preparation the animals were randomly assigned to the following groups: group 1 (n = 32, fentanyl-N2O/normothermia 37.5 degrees C), and group 2 (n = 32, fentanyl-N2O/hypothermia 34.0 degrees C. Ischemia (45 min) was induced by common carotid artery occlusion plus hemorrhagic hypotension (MAP = 40 mmHg). Arterial blood gases and pH were maintained constant. After 1, 3, 7, or 28 days (each n = 8) the brains were removed, frozen and cut. Neuronal damage was assessed by analyzing Bax, Bcl-2, p53, and Mdm-2 proteins, activated caspases-3-positive and eosinophilic cells. A third group (n = 8) of untreated animals served as naive controls. RESULTS: In hypothermic animals, Bax concentration was decreased by 50-70% over time compared to normothermia. On days 1 and 3, Bcl-2 was increased by 50% with hypothermia. The amount of activated caspase-3-positive cells in the ischemic hemisphere was 0.5% in the hypothermic and 1-2% in the normothermic animals. Of the hippocampal cells, 10-25% were eosinophilic in both groups over time. CONCLUSION: The present data show that hypothermia prevents an ischemia-induced increase of the pro-apoptotic protein Bax for as long as 28 days and increases the concentration of the antiapoptotic protein Bcl-2 up to 3 days compared to normothermic animals. Therefore, after cerebral ischemia, hypothermia has the sustained neuroprotective potential to shift apoptosis-related proteins towards neuronal cell survival.

Animals↗
PubMed2004

EEG-based indices of anaesthesia: correlation between bispectral index and patient state index?

BACKGROUND AND OBJECTIVE: Both the bispectral and the patient state indices are derived from the electroencephalogram and have been proposed as a measure of the same clinical target, the hypnotic component of anaesthesia. The present study evaluated whether there is concordance between the bispectral and the patient state indices with regard to end-points measured simultaneously in patients undergoing surgery under general anaesthesia. METHODS: Fifty-seven patients scheduled for elective abdominal, orthopaedic (Groups 1 and 2) or cardiac surgery (Group 3) under general anaesthesia were enrolled in the study. Anaesthesia was performed using remifentanil/ sevoflurane (Group 1, 19 patients), remifentanil/propofol (Group 2, 19 patients) or sufentanil/propofol/isoflurane (Group 3, 19 patients). The bispectral and the patient state indices were simultaneously recorded. Pearson's correlation between these two indices was calculated for the complete data and each group. The percentage of bispectral index values in the recommended range for general anaesthesia (45-60) that were confirmed by levels of patient state index (25-50) was calculated and vice versa. RESULTS: Overall correlation between the bispectral and the patient state indices was 0.667, 0.671 in Group 1, 0.650 in Group 2 and 0.675 in Group 3 (P < 0.01). For values of the bispectral index between 45 and 60, only 40% of corresponding patient state index values were between 25 and 50. For patient state index values of 25-50, only 50% of the corresponding bispectral index values were in the range of 45-60. CONCLUSIONS: Concordance between the bispectral and patient state indices is relatively weak, whereas both are thought to reflect the same clinical target, the hypnotic component of anaesthesia. As a consequence, further studies are required to compare reliability of both indices as indicators of different levels of hypnosis.

Adolescent↗
PubMed2004

Sevoflurane and propofol influence the expression of apoptosis-regulating proteins after cerebral ischaemia and reperfusion in rats.

BACKGROUND AND OBJECTIVE: Sevoflurane and propofol reduce the extent of necrosis and improve neurological outcome in rodent models of cerebral ischaemia and reperfusion. However, the effects of these anaesthetics on programmed cell death (apoptosis) are unclear. The present study investigates whether sevoflurane and propofol affect the expression of apoptosis-regulating proteins after cerebral ischaemia in rats. METHODS: Thirty-two fasted male Sprague-Dawley rats were tracheally intubated and the lungs were ventilated (isoflurane and N2O/O2 anaesthesia). After surgical preparation, the animals were randomly assigned to one of the following groups: control (n = 8): fentanyl intravenous (10 microg kg(-1) bolus and 25 microg kg(-1) h(-1) infusion) with N2O/O2; sevoflurane (n = 8): 2.0% sevoflurane (end-tidal concentration) and O2/air; propofol (n = 8): 0.8-1.0 mg kg(-1) min(-1) propofol intravenous and O2/air; sham-operated (n = 8): 25 microg kg(-1) h(-1) fentanyl intravenous and N2O/O2, no cerebral ischaemia. Ischaemia (30 min) was induced by unilateral common carotid artery occlusion plus haemorrhagic hypotension to a mean arterial pressure of 30-35 mmHg. Four hours after cerebral ischaemia the brains were removed and the expression of apoptosis-regulating proteins (Bax, Bcl-2, p53, Mdm-2) was determined using immunofluorescence and Western-blot analyses. RESULTS: The expression of the pro-apoptotic protein Bax was greater in control animals than in sevoflurane or propofol anaesthetized rats and than in sham-operated animals. The concentrations of Bcl-2, p53 and Mdm-2 were not changed 4 h after cerebral ischaemia. CONCLUSIONS: In addition to the anti-necrotic effects of sevoflurane and propofol, these anaesthetics also reduce the concentration of the apoptosis-inducing protein Bax as early as 4 h after ischaemia.

Anesthetics, Inhalation↗
PubMed2004

Effect of remifentanil on intracranial pressure and cerebral blood flow velocity in patients with head trauma.

BACKGROUND: Remifentanil, an ultra-short-acting opioid, is used as an on-top analgesic in head trauma patients during transient painful procedures, e.g. endotracheal suctioning, physiotherapy, on the intensive care unit. However, previous studies have shown that opioids may increase intracranial pressure and decrease cerebral blood flow. METHODS: The present study investigates the effect of remifentanil on mean arterial blood pressure, intracranial pressure measured with intraparenchymal or epidural probes, and on cerebral blood flow velocity assessed by transcranial Doppler flowmetry in 20 head trauma patients sedated with propofol and sufentanil. Ventilation was adjusted for a target PaCO2 of 4.7-5.1 kPa. After baseline measurements a bolus of remifentanil (0.5 microg x kg(-1) i.v.) was administrated followed by a continuous infusion of remifentanil (0.25 microg x kg(-1) x min(-1) i.v.) for 20 min. RESULTS: There was no change in mean arterial blood pressure, intracranial pressure, and cerebral blood flow velocity in response to remifentanil infusion over time. Statistical analysis was performed using the Wilcoxon Signed Rank test. CONCLUSIONS: These data suggest that remifentanil can be used for on-top analgesia in head trauma patients without adverse effects on cerebrovascular haemodynamics, cerebral perfusion pressure or intracranial pressure.

Analgesics, Opioid↗
PubMed2003

Effects of xenon on mesenteric blood flow.

BACKGROUND AND OBJECTIVE: The effects of xenon on mesenteric vascular resistance have not been investigated. Because human beings anaesthetized with xenon show good cardiovascular stability, we believed that the agent would have little or no effect on vascular resistance in the splanchnic bed. We determined the effects of different inhaled xenon concentrations on mesenteric blood flow and mesenteric oxygen consumption in pigs sedated with intravenous propofol. METHODS: Twenty-three minipigs were instrumented with transit time flow probes around the pulmonary and superior mesenteric arteries as well as with pulmonary artery and portal venous catheters. A 14 h recovery was allowed followed by recordings of baseline values. Xenon was then randomly administered in 0.30, 0.50, and 0.70 end-tidal fractions. RESULTS: The administration of xenon resulted in an 8% (not dose dependent) decrease in mean arterial pressure (from 99 +/- 15 to 91 +/- 19 mmHg; P < 0.05), a 20% decrease in calculated systemic oxygen consumption (from 0.23 +/- 0.07 to 0.19 +/- 0.04L min(-1); P < 0.01), a 20% reduction in mesenteric oxygen delivery (from 41 +/- 12 to 33 +/- 11 mL min; P < 0.001), a 37% reduction in mesentericmetabolic rate of oxygen (from 11.3 +/- 3.6 to 7.1 +/- 3.2 mL min(-1); P < 0.01) and an 8% decrease in mesenteric artery blood flow (0.22 +/- 0.07 to 0.20 +/- 0.07 L min(-1); P < 0.05) in a dose-dependent fashion. Heart rate, cardiac output, systemic vascular resistance, mesenteric vascular resistance, mesenteric oxygen extraction fraction and portal lactate concentration were not significantly altered by xenon. CONCLUSIONS: Xenon inhalation in the propofol-sedated pig had no measurable effects on mesenteric vascular resistance. This finding may partly explain the well-known cardiovascular stability observed in patients anaesthetized with xenon. Although mesenteric artery blood flow and mesenteric oxygen delivery decreased during xenon administration, unchanged mesenteric oxygen extraction fraction and portal lactate suggest that metabolic regulation of the splanchnic circulation remained unaltered.

Anesthetics, Inhalation↗
PubMed2003

[Anaesthesia today].

Anaesthesia today is a cross-over of all medical sub-specialities, based on a stable scientific fundament and a high margin of safety. Anaesthetic techniques are sophisticated and enable a differentiated treatment of pre-, intra- and post-operative medical demands. The physician-patient-relationship and the patients' satisfaction are main aspects of peri-operative care by anaesthetists even in the area of conflict by economic pressure. Nonetheless, the credit to anaesthetists given by physicians and also by the general public is inadequate resulting in difficulties to recruit a sufficient percentage of the decreasing number of aspiring physicians. This could be prevented by an improved medical school and training. Anaesthesiologists in science address either fundamental questions as to mechanisms of anaesthesia and epidemiological aspects of peri-operative medicine.

Anesthesia↗
PubMed2003

Detection of awareness in surgical patients with EEG-based indices--bispectral index and patient state index.

BACKGROUND: Patient state index (PSI) and bispectral index (BIS) are values derived from the EEG, which can measure the hypnotic component of anaesthesia. We measured the ability of PSI and BIS to distinguish consciousness from unconsciousness during induction and emergence from anaesthesia and a period of awareness in surgical patients. METHODS: Forty unpremedicated patients were randomized to receive: (1) sevoflurane/remifentanil (< or =0.1 microg kg(-1) min(-1)), (2) sevoflurane/remifentanil (> or = 0.2 microg kg(-1) min(-1)), (3) propofol/remifentanil (< or =0.1 microg kg(-1) min(-1)), (4) propofol/remifentanil (> or = 0.2 microg kg(-1) min(-1)). Every 30 s after the start of the remifentanil, patients were asked to squeeze the investigator's hand. Sevoflurane or propofol were given until loss of consciousness (LOC1). Tunstall's isolated forearm technique was used during neuromuscular block with succinylcholine. After tracheal intubation, propofol or sevoflurane were stopped until return of consciousness (ROC1). Propofol or sevoflurane were re-started to induce LOC2. After surgery, drugs were discontinued and recovery (ROC2) was observed. PSI and BIS at LOC (LOC1 and LOC2) were compared with those at ROC (ROC1 and ROC2) (t-test). Prediction probability (P(k)) was calculated from values at the last command before and at LOC and ROC. Values are mean (SD). RESULTS: At non-responsiveness, BIS (66 (17)) and PSI (55 (23)) were significantly less than at responsiveness (BIS, 79 (14); PSI, 77 (18); P<0.05). The wide variation with both BIS and PSI measurements of the 80 'awareness' values led to an erroneous classification as unconscious in some cases (BIS, six patients; PSI, nine patients). P(k) was 0.68 (0.03) (BIS) and 0.69 (0.03) (PSI). CONCLUSIONS: Despite significant differences between mean values at responsiveness and non-responsiveness for BIS and PSI, neither measure may be sufficient to detect awareness in an individual patient, reflected by a P(k) less than below 70%.

Adult↗
PubMed2003

Early recovery after remifentanil-pronounced compared with propofol-pronounced total intravenous anaesthesia for short painful procedures.

BACKGROUND: We compared recovery from high-dose propofol/low-dose remifentanil ('propofol-pronounced') compared with high-dose remifentanil/low-dose propofol ('remifentanil-pronounced') anaesthesia. METHODS: Adult patients having panendoscopy, microlaryngoscopy, or tonsillectomy were randomly assigned to receive either propofol-pronounced (propofol 100 microg x kg(-1) min(-1); remifentanil 0.15 microg x kg(-1) min(-1)) or remifentanil-pronounced (propofol 50 microg x kg(-1) min(-1); remifentanil 0.45 microg x kg(-1) min(-1)) anaesthesia. In both groups, the procedure was started with remifentanil 0.4 microg x kg(-1), propofol 2 mg x kg(-1), and mivacurium 0.2 mg x kg(-1). Cardiovascular measurements and EEG bispectral index (BIS) were recorded. To maintain comparable anaesthetic depth, additional propofol (0.5 mg x kg(-1)) was given if BIS values were greater than 55 and remifentanil (0.4 microg x kg(-1)) if heart rate or arterial pressure was greater than 110% of pre-anaesthetic values. RESULTS: Patient and surgical characteristics, cardiovascular measurements, and BIS values were similar in both groups. There were no differences in recovery times between the groups (time to extubation: 12.7 (4.5) vs 12.0 (3.6) min, readiness for transfer to the recovery ward: 14.4 (4.4) vs. 13.7 (3.6) min, mean (SD)). CONCLUSIONS: In patients having short painful surgery, less propofol does not give faster recovery as long as the same anaesthetic level (as indicated by BIS and clinical signs) is maintained by more remifentanil. However, recovery times were less variable following remifentanil-pronounced anaesthesia suggesting a more predictable recovery.

Adolescent↗
PubMed2002

Prediction of movement following noxious stimulation during 1 minimum alveolar anesthetic concentration isoflurane/nitrous oxide anesthesia by means of middle latency auditory evoked responses.

This paper investigates the applicability of generalized dynamic neural networks for the design of a two-valued anesthetic depth indicator during isoflurane/nitrous oxide anesthesia. The indicator construction is based on the processing of middle latency auditory evoked responses (MLAER) in combination with the observation of the patient's movement reaction to skin incision. The framework of generalized dynamic neural networks does not require any data preprocessing, visual data inspection or subjective feature extraction. The study is based on a data set of 106 patients scheduled for elective surgery under isoflurane/nitrous oxide anesthesia. The processing of the measured MLAER is performed by a recurrent neural network that transforms the MLAER signals into signals having a very uncomplex structure. The evaluation of these signals is self-evident, and yields to a simple threshold classifier. Using only evoked potentials before the pain stimulus, the patient's reaction could be predicted with a probability of 81.5%. The MLAER is closely associated to the patient's reaction to skin incision following noxious stimulation during 1 minimum alveolar anesthetic concentration isoflurane/nitrous oxide anesthesia. In combination with other parameters, MLAER could contribute to an objective and trustworthy movement prediction to noxious stimulation.

Anesthetics, Inhalation↗
PubMed2002

Capillary leak syndrome after cardiopulmonary bypass in elective, uncomplicated coronary artery bypass grafting operations: does it exist?

OBJECTIVE: Operations coupled with cardiopulmonary bypass may provoke a systemic inflammatory response, and it has been suggested that this responses causes capillary leakage of proteins, edema formation, and even organ failure. However, capillary leak syndrome is mainly a clinical diagnosis and has not been verified as yet by actual demonstration of protein leakage from the circulation. We have therefore measured the disappearance of labeled plasma protein before and after cardiopulmonary bypass. METHODS: Sixteen patients scheduled for elective coronary artery bypass grafting were enrolled in a prospective controlled study. The cardiopulmonary bypass circuit was primed with crystalloids only. Tumor necrosis factor alpha, interleukin 6, interleukin 8, anaphylatoxin C3a, and terminal complement complex C5b9 levels were determined before, during, and 3 hours after cardiopulmonary bypass. The transvascular escape rate of plasma protein from the intravascular compartment was assessed by measuring the disappearance of intravenously injected Evans blue dye before and during the third hour after cardiopulmonary bypass. RESULTS: A significant inflammatory response could be demonstrated by means of the 5 measured mediators after bypass. The maximal increase, as compared with the baseline value, was found for interleukin 6 (36-fold). The transvascular escape rate of Evans blue dye was similar before and after bypass (7.6 +/- 0.6%/h vs 7.3 +/- 0.6%/h). CONCLUSIONS: The above data confirm the systemic inflammatory response induced by cardiopulmonary bypass. Contrary to expectations, the transvascular escape rate of Evans blue dye did not change when comparing values before and after bypass. The data do not support the concept of increased protein leakage in the exchange vessels after bypass. We were unable to demonstrate a capillary leak syndrome.

Aged↗
PubMed2002

Differential effects of isoflurane on excitatory and inhibitory synaptic inputs to thalamic neurones in vivo.

BACKGROUND: Mechanosensory thalamocortical relay neurones (TCNs) receive glutamatergic excitatory input and are subjected to gamma-aminobutyric acid (GABA)Aergic inhibitory input. This study assessed the effects of an increase in concentration of isoflurane on thalamic excitatory and inhibitory mechanisms. METHODS: TCNs (n = 15) of the thalamic ventral posteromedial nucleus responding to mechanical stimulation of whiskers were investigated in rats anaesthetized with end-tidal concentrations of isoflurane of approximately 0.9% (ISOlow, baseline) and approximately 1.9% (ISOhigh). Response activity induced by controlled vibratory movement of single whiskers was recorded before, during and after iontophoretic administration of the GABAA receptor antagonist bicuculline to the vicinity of the recorded neurone. RESULTS: The increase in concentration of isoflurane induced a suppression of vibratory responses to 14 (4)% [mean (SEM)] of baseline activity. Blockade of GABAA receptors by bicuculline during ISOlow and ISOhigh caused increases in response activity to 259 (32)% and 116 (25)% of baseline activity, respectively. The increase in isoflurane concentration enhanced overall inhibitory inputs by 102 (38)%, whilst overall excitatory inputs were reduced by 54 (7)%. CONCLUSIONS: These data suggest that doubling the concentration of isoflurane doubles the strength of GABAAergic inhibition and decreases the excitatory drive of TCNs by approximately 50%. The isoflurane-induced enhancement of GABAAergic inhibition led to a blockade of thalamocortical information transfer which was not accomplished by the effects of isoflurane on glutamatergic synaptic transmission alone. Thus, it appears that, with respect to transmission of information in the thalamus, the most prominent action of isoflurane is an enhancement of GABAAergic synpatic inhibition, and that effects on glutamatergic neurotransmission may contribute to a lesser extent.

Anesthetics, Inhalation↗
PubMed2001

Isoflurane slows inactivation kinetics of rat recombinant alpha1beta2gamma2L GABA(A) receptors: enhancement of GABAergic transmission despite an open-channel block.

Recombinant alpha1beta2gamma2L gamma-aminobutyric acid (A) receptor (GABA(A)R) channels expressed in human embryonic kidney (HEK293) cells were used for patch-clamp experiments. The currents activated by brief pulses of GABA (10(-4) M) applied with a device for fast solution exchange to cells clamped in the whole-cell configuration mimicked GABA(A)R-mediated inhibitory postsynaptic currents. Isoflurane (ISO) at clinically relevant concentrations (0.6 mM) decreased the amplitude and prolonged the decay of the GABA-evoked response. To further detail the mechanism underlying the prolonged decay time, we made simulations based on these measurements. These simulations suggest that ISO slows the rate of GABA unbinding from the receptor. Under these conditions, ISO increases the GABA-induced charge transfer and, thus, could enhance GABAergic inhibition despite the concomitant open-channel block causing the decrease in the current amplitude.

Anesthetics, Inhalation↗