Anaesthetic efficacy and postinduction hypotension with remimazolam compared with propofol: a multicentre randomised controlled trial

Remimazolam, a short-acting benzodiazepine, may be used for induction and maintenance of total intravenous anaesthesia, but its role in the management of patients with multiple comorbidities remains unclear. In this phase 3 randomised controlled trial, we compared the anaesthetic efficacy and the incidence of postinduction hypotension during total intravenous anaesthesia with remimazolam vs. propofol. A total of 365 patients (ASA physical status 3 or 4) scheduled for elective surgery were assigned randomly to receive total intravenous anaesthesia with remimazolam (n = 270) or propofol (n = 95). Primary outcome was anaesthetic effect, quantified as the percentage of time with Narcotrend® Index values ≤ 60, during surgery (skin incision to last skin suture), with a non-inferiority margin of -10%. Secondary outcome was the incidence of postinduction hypotensive events. Mean (SD) percentage of time with Narcotrend Index values ≤ 60 during surgery across all patients receiving remimazolam (93% (20.7)) was non-inferior to propofol (99% (4.2)), mean difference (97.5%CI) -6.28% (-8.89-infinite); p = 0.003. Mean (SD) number of postinduction hypotension events was 62 (38.1) and 71 (41.1) for patients allocated to the remimazolam and propofol groups, respectively; p = 0.015. Noradrenaline administration events (requirement for a bolus and/or infusion) were also lower in patients allocated to remimazolam compared with propofol (14 (13.5) vs. 20 (14.6), respectively; p < 0.001). In conclusion, in patients who were ASA physical status 3 or 4, the anaesthetic effect of remimazolam was non-inferior to propofol.

Enabling personalized perioperative risk prediction by using a machine-learning model based on preoperative data

Preoperative risk assessment is essential for shared decision-making and adequate perioperative care. Common scores provide limited predictive quality and lack personalized information. The aim of this study was to create an interpretable machine-learning-based model to assess the patient's individual risk of postoperative mortality based on preoperative data to allow analysis of personal risk factors. After ethical approval, a model for prediction of postoperative in-hospital mortality based on preoperative data of 66,846 patients undergoing elective non-cardiac surgery between June 2014 and March 2020 was created with extreme gradient boosting. Model performance and the most relevant parameters were shown using receiver operating characteristic (ROC-) and precision-recall (PR-) curves and importance plots. Individual risks of index patients were presented in waterfall diagrams. The model included 201 features and showed good predictive abilities with an area under receiver operating characteristic (AUROC) curve of 0.95 and an area under precision-recall curve (AUPRC) of 0.109. The feature with the highest information gain was the preoperative order for red packed cell concentrates followed by age and c-reactive protein. Individual risk factors could be identified on patient level. We created a highly accurate and interpretable machine learning model to preoperatively predict the risk of postoperative in-hospital mortality. The algorithm can be used to identify factors susceptible to preoperative optimization measures and to identify risk factors influencing individual patient risk.

Impact of instructor professional background and interim retesting on knowledge and self-confidence of schoolchildren after basic life support training: a cluster randomised longitudinal study

Introduction

To increase the rate of bystander resuscitation, basic life support (BLS) training for schoolchildren is now recommended on a broad level. However, debate continues about the optimal teaching methods. In this study, we investigated the effects of a 90 min BLS training on female pupils’ BLS knowledge and self-confidence and whether learning outcomes were influenced by the instructors’ professional backgrounds or test-enhanced learning.

Methods

We conducted a cluster randomised, longitudinal trial in a girls’ grammar school in Germany from 2013 to 2014. Pupils aged 10–17 years were randomised to receive BLS training conducted by either emergency physicians or medical students. Using a multiple-choice questionnaire and a Likert-type scale, BLS knowledge and self-confidence were investigated before training (t0), 1 week (t1) and 9 months after training (t2). To investigate whether test-enhanced learning influenced learning outcomes, the questionnaire was administered 6 months after the training in half of the classrooms. The data were analysed using linear mixed-effects models.

Results

The study included 460 schoolchildren. BLS knowledge (mean number of correct answers) increased from 5.86 at t0to 9.24 at t1(p<0.001) and self-confidence (mean score on the Likert-type scale) increased from 8.70 at t0to 11.29 at t1(p<0.001). After 9 months, knowledge retention was good (8.94 at t2; p=0.080 vs t1), but self-confidence significantly declined from t1to 9.73 at t2(p<0.001). Pupils trained by medical students showed a slight but statistically significant greater increase in the knowledge at both t1and t2, whereas instructors’ background did not influence gain or retention of self-confidence. Retesting resulted in a marginally, non-significantly better retention of knowledge.

Conclusions

BLS training led to short-term gains in knowledge and self-confidence. Although knowledge was retained at 9 months after the training session, self-confidence significantly decreased. Interim testing did not appear to impact retention of knowledge or self-confidence. Medical students should be considered as instructors for these courses given their favourable learning outcomes and greater availability.

2018 Annual Report of the European Liver Transplant Registry (ELTR) - 50-year evolution of liver transplantation

The purpose of this registry study was to provide an overview of trends and results of liver transplantation (LT) in Europe from 1968 to 2016. These data on LT were collected prospectively from 169 centers from 32 countries, in the European Liver Transplant Registry (ELTR) beginning in 1968. This overview provides epidemiological data, as well as information on evolution of techniques, and outcomes in LT in Europe over more than five decades; something that cannot be obtained from only a single center experience.

Propofol and Sevoflurane Differentially Modulate Cortical Depolarization following Electric Stimulation of the Ventrobasal Thalamus

The neuronal mechanisms how anesthetics lead to loss of consciousness are unclear. Thalamocortical interactions are crucially involved in conscious perception; hence the thalamocortical network might be a promising target for anesthetic modulation of neuronal information pertaining to arousal and waking behavior. General anesthetics affect the neurophysiology of the thalamus and the cortex but the exact mechanisms of how anesthetics interfere with processing thalamocortical information remain to be elucidated. Here we investigated the effect of the anesthetic agents sevoflurane and propofol on thalamocortical network activity in vitro. We used voltage-sensitive dye imaging techniques to analyze the cortical depolarization in response to stimulation of the thalamic ventrobasal nucleus in brain slices from mice. Exposure to sevoflurane globally decreased cortical depolarization in a dose-dependent manner. Sevoflurane reduced the intensity and extent of cortical depolarization and delayed thalamocortical signal propagation. In contrast, propofol neither affected area nor amplitude of cortical depolarization. However, propofol exposure resulted in regional changes in spatial distribution of maximum fluorescence intensity in deep regions of the cortex. In summary, our experiments revealed substance-specific effects on the thalamocortical network. Functional changes of the neuronal network are known to be pivotally involved in the anesthetic-induced loss of consciousness. Our findings provide further evidence that the mechanisms of anesthetic-mediated loss of consciousness are drug- and pathway-specific.

Immature platelets as a novel biomarker for adverse cardiovascular events in patients after non-cardiac surgery

This study evaluates whether immature platelets (IPF) determined in the post anesthesia care unit (PACU) can predict major adverse cardiovascular events (MACE) or other thromboembolic events after intermediate and high-risk surgery. IPF are increased in patients with acute coronary syndrome and recently gained interest as novel biomarker for risk stratification. In this prospective observational trial 732 patients undergoing intermediate or high-risk non-cardiac surgery were enrolled (NCT02097602). IPF was measured preoperatively and postoperatively in the PACU. Primary outcome was a composite endpoint defined as MACE, deep vein thrombosis or pulmonary embolism during hospital stay (modMACE). A cut off for IPF identifying a threshold between a low and high risk for modMACE was calculated by logrank optimization. A multivariate Cox regression was calculated in a forward stepwise manner to assess the relation between this IPF cut off and modMACE as well as other established risk factors (inclusion if p<0.05). Preoperatively, there were no differences in IPF between patients with and without modMACE (3.1% [2.2% – 4.7%](median [interquartile range]) vs. 2.8% [1.9% – 4.3%]. Patients with modMACE (28 of 730 patients; 3.8%) had higher IPF values in the PACU compared to patients without modMACE (3.6% [2.6–6%] vs. 2.9% [2–4.4%]; p=0.011). The optimal cut off of IPF > 5.4% was associated with an increased risk for modMACE after adjustment for covariates (hazard ratio: 2.528; 95% confidence interval: 1.156 to 5.528, p=0.02). In conclusion, IPF is an independent predictor of modMACE after surgery and might improve risk stratification of surgical patients.

Institution where the work was performed and funded: Klinikum rechts der Isar der Technischen Universität München, Ismaningerstr. 22, 81675 Munich, Germany.

Safe Brain Tumor Resection Does not Depend on Surgery Alone - Role of Hemodynamics

Aim of this study was to determine if perioperative hemodynamics have an impact on perioperative infarct volume and patients’ prognosis. 201 cases with surgery for a newly diagnosed or recurrent glioblastoma were retrospectively analyzed. Clinical data and perioperative hemodynamic parameters, blood tests and time of surgery were recorded. Postoperative infarct volume was quantitatively assessed by semiautomatic segmentation. Mean diastolic blood pressure (dBP) during surgery (rho −0.239, 95% CI −0.11 – −0.367, p = 0.017), liquid balance (rho 0.236, 95% CI 0.1–0.373, p = 0.017) and mean arterial pressure (MAP) during surgery (rho −0.206, 95% CI −0.07 – −0.34, p = 0.041) showed significant correlation to infarct volume. A rank regression model including also age and recurrent surgery as possible confounders revealed mean intraoperative dBP, liquid balance and length of surgery as independent factors for infarct volume. Univariate survival analysis showed mean intraoperative dBP and MAP as significant prognostic factors, length of surgery also remained as significant prognostic factor in a multivariate model. Perioperative close anesthesiologic monitoring of blood pressure and liquid balance is of high significance during brain tumor surgery and should be performed to prevent or minimize perioperative infarctions and to prolong survival.

Utility of basophil activation testing to assess perioperative anaphylactic reactions in real-world practice

Introduction

Perioperative anaphylactic reactions due to drugs and substances associated with general anesthesia can potentially be life‐threatening. The objective of this study was to investigate the significance of the basophil activation test (BAT) for allergy diagnosis work up.

Methods

A total of 14 patients (5 men, 9 women; mean age: 57.8 years) with clinical records of anaphylactic reactions under general anesthesia were studied by means of anesthesia records, skin and serological tests. Eleven healthy subjects without any history of allergic sensitization to anaesthetic drugs served as controls. BATs based on stimulation of whole blood cells measuring CD63 activation of basophils and using CCR3 as basophil marker by flow cytometry (Flow CAST®, BÜHLMANN Laboratories AG, Schönenbuch, Switzerland) were performed with the following substances (in dependence on the history and the skin tests of the patient): analgesics (acetylsalicylic acid, celecoxib, diclofenac, ibuprofen, indometacin, metamizole, paracetamol, propyphenazone, tramadol), antibiotics (PPL (benzylpenicilloyl polylysine), MDM (minor determinant mixture), amoxicillin, cefuroxime, ciprofloxacin, doxycycline, erythromycin, roxithromycin, sulfamethoxazole, trimethoprim), local anesthetics (articaine, bupivacaine, lidocaine, prilocaine, procaine, methyl‐4‐hydroxybenzoate), narcotics and NMBA (atracurium, cisatracurium, etomidate, neostigmine, midazolam, mivacurium, pancuronium, propofol, pyridostigmine, succinylcholine, sufentanil, thiopental, vecuronium), and other individual substances.

Results

Three patients showed positive results in the BAT: One to metamizole, one to PPL, and one to pancuronium. BATs with these substances were negative in controls.

Conclusions

The BAT should be used complementary to skin tests, especially if IgE‐mediated mechanisms are presumed and skin tests are inconclusive. A positive reaction in BAT identifies the culprit agent with high probability.

[Current status of teaching in lung ultrasound : Query of knowledge, utilization, need, and preferred teaching method]

BACKGROUND

Lung ultrasound (LUS) is a point-of-care technique which can quickly identify or rule out pathological findings. To date, it is unclear if knowledge about the use of LUS is readily available.

OBJECTIVES

We aimed to identify how much knowledge about the use of LUS is present, if there is a need for teaching in LUS, as well as the preferred teaching method in LUS.

MATERIALS AND METHODS

A total of 54 participants from two university departments of anesthesiology were randomized into the groups Online, Classroom, and Control. The Online group was taught by videos, the Classroom group by a traditional lecture with hands-on training, and the Control group was not taught at all. We conducted a pre- and posttest as well as a retention test 4 weeks after the end of the study by means of a survey (comparison with Mann-Whitney U test or t‑test, respectively, with p < 0.05 considered to be significant).

RESULTS

LUS is used "rarely" or "never", and mainly if there is a suspicion for pleural effusion (41.3%). There is a need for LUS (Online: 21.7%; Classroom: 60.9%; Control: 62.5%, p < 0.05). Hybrid teaching consisting of classroom-based and online-based teaching is preferred by the users (Online: 52.2%; Classroom: 56.5%; Control: 62.5%). At the end of the study, 32.6% of the participants of the intervention groups had used LUS in the diagnosis of a pneumothorax. Of the participants, 93.5% planned to use LUS more often in the future.

CONCLUSIONS

LUS is rarely used. There is a considerable need for teaching of LUS. Internet-based teaching and traditional lectures are considered equal. Both teaching methods improve the knowledge about LUS and lead to increased use of LUS in daily practice. The participants prefer hybrid teaching incorporating both teaching methods.

Perioperative risk factors for postoperative pulmonary complications after major oral and maxillofacial surgery with microvascular reconstruction: A retrospective analysis of 648 cases

BACKGROUND

Postoperative pulmonary complications (PPCs) are common and result in prolonged hospital stays, higher costs and increased mortality. However, data on the incidence and predictors of PPCs after major oral and maxillofacial surgery with microvascular reconstruction are rare. This retrospective analysis identifies perioperative risk factors for postoperative pulmonary complications (PPCs) after major oral and maxillofacial surgery with microvascular reconstruction.

METHODS

Perioperative data and patient records of 648 subjects were analyzed in the period of June 2007 to May 2013. PPCs were defined as pneumonia, atelectasis, pleural effusions, pulmonary embolism, pulmonary oedema, pneumothorax or respiratory failure.

RESULTS

18.8% of all patients developed PPCs. Patient-related risk factors for PPCs were male sex, advanced age, smoking, alcohol abuse, a body mass index >30, American Society of Anaesthesiologists grade higher than 2, pre-existent pulmonary diseases and preoperative antihypertensive medication. Among the investigated procedure-related variables, the length of the operation, the amount of fluid administration and blood transfusion and an impaired oxygenation index during surgery were shown to be associated with the development of PPCs. Using a multivariable logistic regression model, we identified a body mass index >30, American Society of Anaesthesiologists grade higher than 2 and alcohol abuse as independent risk factors for PPCs.

CONCLUSIONS

Several perioperative factors can be identified that are associated with the development of PPCs. Patients having one or more of these conditions should be subjected to intensified postoperative pulmonary care.

[Preoperative patient-oriented advance planning of emergency and intensive care treatment--Necessary or imposition? : Questionnaire survey]

BACKGROUND

Traditional advance directives can often not be satisfactorily implemented into patient care; therefore, patient-oriented decision-making prior to scheduled interventions and beyond the actual surgery is of particular importance. Data on inpatient advance care planning (ACP) in Germany are lacking.

OBJECTIVES

This proof-of-concept study was carried out to determine the needs of inpatients undergoing surgery for advance preoperative planning of emergency care and to assess potential discomfort caused by such a program.

MATERIAL AND METHODS

A voluntary and anonymous standardized questionnaire survey was carried out in scheduled surgery inpatients over 50 years old. Data collection was structured in a demographic part and statements dealing with preoperative advance planning of emergency care in hospital evaluated as Likert items.

RESULTS

Out of 579 patients (mean age 66 years, 51% male) 43% indicated a basic interest in being informed about advance planning of emergency care individually during the current hospital stay. Desire for patient self-determination represented an independent factor of information needs [p = 0.036, 95% confidence interval (95% CI) 0.027-0.793]. The survey was perceived as a burden by only 7.3% of patients. This perception was independently associated with less concern about perioperative complication risks (p = 0.008, 95% CI 0.144-0.975).

CONCLUSION

The results confirmed a substantial interest in patient-oriented advance planning of emergency care in a preoperative setting; however, no demographic group criteria for patients with information requirements could be defined. As the burden evoked by the topic is low, advance planning of emergency and intensive care treatment of inpatients undergoing surgery should be actively provided in the future.

Point-of-care testing on admission to the intensive care unit: lactate and glucose independently predict mortality

BACKGROUND

The aim of the study was to retrospectively investigate whether parameters of routine point-of-care testing (POCT) predict hospital mortality in critically ill surgical patients on admission to the intensive care unit (ICU).

METHODS

Arterial blood analyses of 1551 patients on admission to the adult surgical ICU of the Technical University Munich were reviewed. POCT was performed on a blood gas analyser. The association between acid-base status and mortality was evaluated. Metabolic acidosis was defined by base excess (BE) <-2 mmol/L and, wherever applicable, subdivided into lactic acidosis by lactate >50% of BE, anion gap (AG)-acidosis by AG >16 mmol/L, hyperchloraemic acidosis by chloride >115 mmol/L. Metabolic alkalosis was defined by BE ≥3 mmol/L. Logistic regression analysis identified variables independently associated with mortality.

RESULTS

Overall mortality was 8.8%. Mortality was greater in male patients (p=0.012). Mean age was greater in non-survivors (p<0.0005). Nine hundred and eighty-six patients showed no metabolic acid-base disorder (mortality 7.3%), thereof 26 patients with pCO(2)>55 mm Hg (mortality 23.1%). Three hundred and seventy-seven patients presented with acidosis (mortality 11.4%), thereof 163 patients with lactic acidosis (mortality 19%). Mortality for alkalosis (174 patients) was 12.1%. Mean blood glucose level for non-survivors was higher compared to survivors (p<0.0005). Logistic regression analysis identified lactate, glucose, age, male gender as independent predictors of mortality.

CONCLUSIONS

Lactate and glucose on ICU admission independently predict mortality. BE and AG failed as prognostic markers. Lactic acidosis showed a high mortality rate implying that lactate levels should be obtained on ICU admission. Prevalence of hyperchloraemic acidosis was low. Metabolic alkalosis was associated with an increased mortality. Further studies on this disturbance and its attendant high mortality are warranted.

Activation of CRH receptor type 1 expressed on glutamatergic neurons increases excitability of CA1 pyramidal neurons by the modulation of voltage-gated ion channels

Corticotropin-releasing hormone (CRH) plays an important role in a substantial number of patients with stress-related mental disorders, such as anxiety disorders and depression. CRH has been shown to increase neuronal excitability in the hippocampus, but the underlying mechanisms are poorly understood. The effects of CRH on neuronal excitability were investigated in acute hippocampal brain slices. Population spikes (PS) and field excitatory postsynaptic potentials (fEPSP) were evoked by stimulating Schaffer-collaterals and recorded simultaneously from the somatic and dendritic region of CA1 pyramidal neurons. CRH was found to increase PS amplitudes (mean ± Standard error of the mean; 231.8 ± 31.2% of control; n = 10) while neither affecting fEPSPs (104.3 ± 4.2%; n = 10) nor long-term potentiation (LTP). However, when Schaffer-collaterals were excited via action potentials (APs) generated by stimulation of CA3 pyramidal neurons, CRH increased fEPSP amplitudes (119.8 ± 3.6%; n = 8) and the magnitude of LTP in the CA1 region. Experiments in slices from transgenic mice revealed that the effect on PS amplitude is mediated exclusively by CRH receptor 1 (CRHR1) expressed on glutamatergic neurons. The effects of CRH on PS were dependent on phosphatase-2B, L- and T-type calcium channels and voltage-gated potassium channels but independent on intracellular Ca²⁺-elevation. In patch-clamp experiments, CRH increased the frequency and decay times of APs and decreased currents through A-type and delayed-rectifier potassium channels. These results suggest that CRH does not affect synaptic transmission per se, but modulates voltage-gated ion currents important for the generation of APs and hence elevates by this route overall neuronal activity.

Sevoflurane anesthesia improves cognitive performance in mice, but does not influence in vitro long-term potentation in hippocampus CA1 stratum radiatum

BACKGROUND

Whether the occurrence of postoperative cognitive dysfunction is a result of the effects of surgery or anesthesia is under debate. In this study, we investigated the impact of sevoflurane anesthesia on cognitive performance and cellular mechanisms involved in learning and memory.

METHODS

Male C57Bl6/J mice (4-5 months) were exposed to one minimum alveolar concentration sevoflurane for two hours. After 24 h, cognitive performance of mice was assessed using the modified hole board test. Additionally, we evaluated hippocampal long-term potentiation and expression levels of different receptor subunits by recording excitatory postsynaptic field potentials and using the western blot technique, respectively. Non-anesthetized mice served as controls.

RESULTS

In anesthetized mice, neither cognitive performance nor long-term potentiation was impaired 24 h after anesthesia. Interestingly, sevoflurane anesthesia induced even an improvement of cognitive performance and an elevation of the expression levels of N-methyl-D-aspartate (NMDA) receptor type 1 and 2B subunits in the hippocampus.

CONCLUSIONS

Since NMDA receptor type 1 and 2B subunits play a crucial role in processes related to learning and memory, we hypothesize that sevoflurane-induced changes in NMDA receptor subunit composition might cause hippocampus-dependent cognitive improvement. The data of the present study are in favor of a minor role of anesthesia in mediating postoperative cognitive dysfunction.

Low dose isoflurane exerts opposing effects on neuronal network excitability in neocortex and hippocampus

The anesthetic excitement phase occurring during induction of anesthesia with volatile anesthetics is a well-known phenomenon in clinical practice. However, the physiological mechanisms underlying anesthetic-induced excitation are still unclear. Here we provide evidence from in vitro experiments performed on rat brain slices that the general anesthetic isoflurane at a concentration of about 0.1 mM can enhance neuronal network excitability in the hippocampus, while simultaneously reducing it in the neocortex. In contrast, isoflurane tissue concentrations above 0.3 mM expectedly caused a pronounced reduction in both brain regions. Neuronal network excitability was assessed by combining simultaneous multisite stimulation via a multielectrode array with recording intrinsic optical signals as a measure of neuronal population activity.

Isoflurane and sevoflurane dose-dependently impair hippocampal long-term potentiation

Isoflurane and sevoflurane are commonly used volatile anaesthetics. Although acting via similar cellular mechanisms, the effect of different volatile anaesthetics on synaptic plasticity might differ. In the present study, using acute murine brain slice preparations, we compared the effects of isoflurane and sevoflurane on synaptic transmission and synaptic plasticity (long-term potentiation, LTP) in the CA1 stratum radiatum of the hippocampus. Isoflurane and sevoflurane dose-dependently diminished excitatory postsynaptic field potentials. In the presence of isoflurane (sevoflurane) at concentrations of 0.19, 0.28 and 0.37mM (0.11, 0.21 and 0.42mM), which correspond to 0.7-, 1.0- and 1.4-fold (0.3-, 0.6- and 1.1-fold) minimum alveolar concentration (MAC), high frequency stimulation reliably induced LTP. When isoflurane (sevoflurane) was applied at concentrations of 0.56 and 0.74mM (0.63 and 0.84mM), which equal 2.1- and 2.7-fold (1.7- and 2.2-fold) MAC, LTP was blocked. Our results indicate, that both anaesthetics influence synaptic strength to a similar degree, with only high concentrations blocking hippocampal CA1 stratum radiatum long-term potentiation.

Adapted variable precision rough set approach for EEG analysis

OBJECTIVE

Rough set theory (RST) provides powerful methods for reduction of attributes and creation of decision rules, which have successfully been applied in numerous medical applications. The variable precision rough set model (VPRS model), an extension of the original rough set approach, tolerates some degree of misclassification of the training data. The basic idea of the VPRS model is to change the class information of those objects whose class information cannot be induced without contradiction from the available attributes. Thereafter, original methods of RST are applied. An approach of this model is presented that allows uncertain objects to change class information during the process of attribute reduction and rule generation. This method is referred to as variable precision rough set approach with flexible classification of uncertain objects (VPRS(FC) approach) and needs only slight modifications of the original VPRS model.

METHODS AND MATERIAL

To compare the VPRS model and VPRS(FC) approach both methods are applied to a clinical data set based on electroencephalogram of awake and anesthetized patients. For comparison, a second data set obtained from the UCI machine learning repository is used. It describes the shape of different vehicle types. Further well known feature selection methods were applied to both data sets to compare their results with the results provided by rough set based approaches.

RESULTS

The VPRS(FC) approach requires higher computational effort, but is able to achieve better reduction of attributes for noisy or inconsistent data and provides smaller rule sets.

CONCLUSION

The presented approach is a useful method for substantial attribute reduction in noisy and inconsistent data sets.

Dose-dependent effect of S(+) ketamine on post-ischemic endogenous neurogenesis in rats

BACKGROUND

Ketamine is a non-competitive antagonist at N-methyl-D-aspartate (NMDA) receptors and reduces neuronal injury after cerebral ischemia by blocking the excitotoxic effects of glutamate. However, cerebral regeneration by means of endogenous neurogenesis may be impaired with blockade of NMDA receptors. The effects of S(+) ketamine on post-ischemic neurogenesis are unknown and investigated in this study.

METHODS

Thirty-two male Sprague-Dawley rats were randomly assigned to the following treatment groups with intravenous S(+) ketamine anesthesia: S(+) ketamine 0.75 mg/kg/min with or without cerebral ischemia and S(+) ketamine 1.0 mg/kg/min with or without cerebral ischemia. Eight non-anesthetized, non-ischemic animals were investigated as naïve controls. Forebrain ischemia was induced by bilateral common carotid artery occlusion in combination with hemorrhagic hypotension. 5-bromo-2-deoxyuridine (BrdU) was injected intraperitoneally for seven consecutive post-operative days. BrdU-positive neurons in the dentate gyrus and histopathological damage of the hippocampus were analyzed after 28 days.

RESULTS

The number of new neurons was not affected by S(+) ketamine in the absence of cerebral ischemia. The ischemia-induced increase in neurogenesis was reduced by high-dose S(+) ketamine. Cell death of ischemic animals did not vary between low- and high-dose S(+) ketamine.

CONCLUSION

While low concentrations of S(+) ketamine allow an ischemia-induced increase in the number of new neurons, high S(+) ketamine concentrations block the post-ischemic increase in newly generated neurons. This effect is irrespective of the extent of other histopathological damage and in line with studies showing that NMDA receptor antagonists like MK-801 inhibit neurogenesis after cerebral ischemia.

High risk of cognitive and functional decline after postoperative delirium. A three-year prospective study

BACKGROUND/AIMS

The aim of the study was to investigate the association of postoperative delirium with the outcomes of cognitive impairment, functional disability and death.

METHODS

Hip surgery patients aged 60 years or over (n = 200) underwent preoperative and daily postoperative assessment of their cognitive status during hospital stay. Outcome variables were determined at an average of 8 and 38 months after discharge from hospital.

RESULTS

Fourty-one patients developed postoperative delirium. Delirium was a strong independent predictor of cognitive impairment and the occurrence of severe dependency in activities of daily living. The associations were more marked for the long- than for the short-term outcome. Thirty-eight months after discharge from hospital, 53.8% of the surviving patients with postoperative delirium suffered from cognitive impairment, as compared to only 4.4% of the nondelirious participants. Logistic regression analysis adjusted for age, sex, medical comorbidity and preoperative cognitive performance revealed highly significant associations between delirium and cognitive impairment (OR = 41.2; 95% CI = 4.3-396.2), subjective memory decline (OR = 6.2; 95% CI = 1.5-25.8) and incident need for long-term care (OR = 5.6; 95% CI = 1.6-19.7).

CONCLUSION

The present study confirms a poor prognosis after delirium in elderly patients. The findings suggest that delirium does not simply persist for a certain time but also predicts a future cognitive decline with an increased risk of dementia.

Anesthetics drug pharmacodynamics

Anesthesia cannot be defined in an unambiguous manner. The essential components of general anesthesia are absence of consciousness and pain. This translates into two particular qualities: (1) sedation and hypnosis, i.e., mental blockade and (2) analgesia/antinociception, i.e., sensory blockade. Anesthetic actions on these two subcomponents are difficult to separate. On the one hand, very few anesthetics act exclusively on one of these components. On the other hand, these components are closely related to each other. Unconsciousness prevents (conscious) perception of pain, and nociception may serve as an arousal stimulus and change the level of sedation and hypnosis. The art of anesthesia lies in adequate dosing of drugs to reach both mental and sensory blockade. Drug administration can be based on pharmacokinetic considerations. Pharmacokinetic models allow an estimation of what happens to the administered drug in the body. Models with an effect site compartment may facilitate a tailored administration of anesthetic drugs. Finally, the quantification of pharmacodynamic effects allows a precise titration of drugs. Clinical assessment of mental blockade is often dichotomous, and therefore not very helpful to guide drug administration. Several scoring systems exist, but once consciousness is lost they become less reliable, in particular because reaction to stimuli is assessed, which mixes assessment of mental blockade with assessment of sensory blockade. Clinical assessment of analgesia requires a conscious patient, so antinociception is difficult to measure. Several methods of objective quantification on the basis of electrical brain activity are discussed including EEG and evoked potentials. Despite numerous indexes of the hypnotic component of anesthesia, there is no parameter that unambiguously quantifies the level of mental or sensory blockade.

The Narcotrend monitor and the electroencephalogram in propofol-induced sedation

BACKGROUND

The Narcotrend (NCT) is a one-channel electroencephalogram (EEG) monitor of the level of sedation. It is based on a visual EEG scoring system, which was developed by Loomis and modified by Kugler, to yield a visual expert classification (VEC) scheme for differentiation of six levels of sedation (A-F), which are subdivided into 16 substages. We designed the present study to test whether results of the automated classification of one-channel NCT input reflect those from VEC of five-channel EEG.

METHODS

Twelve healthy male volunteers received propofol using two different infusion regimens in a randomized, crossover design with concomitant NCT monitoring and VEC. Scoring results of NCT were compared with those of VEC.

RESULTS

During the infusion period, score differences of more than three substages were observed in 14 of 24 (= 58%) propofol administrations (4%-7% of total data). Often, the NCT indicated lighter sedation than VEC, which revealed more delta activity from nonfrontal leads. During recovery, NCT reported deeper sedation than VEC in 6 of 24 (= 25%) propofol administrations. Discordant trends (periods of at least five subsequent epochs with monotonic, but opposite trends for both NCT and VEC) were noted in 9 of 24 propofol administrations (37%). Furthermore, NCT had several periods when no staging information was displayed, varying from a few seconds to 10 min.

CONCLUSIONS

As the algorithm of NCT is proprietary and not accessible to the public, reasons for the observed differences between NCT and VEC cannot be analyzed and explanations must remain speculative.

Sevoflurane Affects Neurogenesis After Forebrain Ischemia in Rats

BACKGROUND

The effect of sevoflurane on the neuroregenerative potential after neuronal injury is unclear. We investigated the effect of low and high concentrations of sevoflurane on endogenous neurogenesis after cerebral ischemia.

METHODS

Anesthetized and ventilated rats were randomized to four different treatment groups. Groups 1 and 2: 1.4% sevoflurane; Groups 3 and 4: 2.8% sevoflurane. In Groups 1 and 3, no cerebral ischemia was induced (sham-operated). In Groups 2 and 4, 10 min of forebrain ischemia was induced by bilateral carotid artery occlusion plus hemorrhagic hypotension. Physiological variables were maintained constant. Bromodeoxyuridine was given as a marker of neurogenesis. After 28 days brains were perfused. Histopathological damage of the hippocampus was evaluated in hematoxylin and eosin (HE) stained sections using the HE-index (0 = no damage; 1 = 1%-10% damage; 2 = 11%-50% damage; 3 = 51%-100% damage). Immunohistochemistry was used to detect bromodeoxyuridine-positive neurons. Eight untreated rats were investigated as naive controls (Group 5).

RESULTS

In neither sham-operated group was histopathological damage or change in neurogenesis observed compared to naive controls. In rats anesthetized with 1.4% sevoflurane, cerebral ischemia caused mild neuronal damage (HE-index of 0.64 +/- 0.84) and increased neurogenesis by 60% when compared with respective sham-operated animals; with 2.8% sevoflurane, the HE-index was 1.22 +/- 1.14, and the number of newly generated neurons increased by 230% when compared with respective sham-operated animals.

CONCLUSION

The present data suggest that high concentrations of sevoflurane stimulate neurogenesis in the dentate gyrus after cerebral ischemia.

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.

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.

Nitrous oxide (N2O) pre- and postsynaptically attenuates NMDA receptor-mediated neurotransmission in the amygdala

The gaseous anaesthetic N(2)O displays analgesic, anxiolytic, and amnesic properties and has addictive psychedelic effects. N(2)O can further act as a neuroprotective agent, but may also become neurotoxic under certain conditions. Here, we employed whole-cell patch-clamp techniques in acute brain slices, and electrical afferent and infrared-guided laser stimulation to examine how N(2)O (65%) can affect NMDA receptor (NMDAR)-mediated synaptic transmission to principal neurons (PNs) of the adult murine basolateral amygdala (BLA). The BLA plays a critical role in anaesthetic-induced amnesia, the formation of aversive memories, as well as in fear and addictive behaviour. We evoked NMDAR-mediated excitatory postsynaptic currents (NMDAR-EPSCs) in PNs of the BLA (BLA-PNs). We found these currents to be markedly decreased by N(2)O via pre- and postsynaptic actions: Without changing their kinetics and open probability, N(2)O impeded the voltage-dependent channel opening of NMDARs in BLA-PNs and diminished their unitary conductance as estimated by non-stationary fluctuation analysis. In addition, our data speak in favour of a N(2)O-produced reduction in the probability of glutamate release at the synapses generating the NMDAR-EPSCs. It is conceivable that these effects not only contribute to anaesthesia and anxiolysis, but also have bearings on learning and memory as well as excitotoxicity in the amygdala.

Application of Generalized Dynamic Neural Networks to Biomedical Data

This paper reviews the application of continuous recurrent neural networks with time-varying weights to pattern recognition tasks in medicine. A general learning algorithm based on Pontryagin's maximum principle is recapitulated, and possibilities of improving the generalization capabilities of these networks are given. The effectiveness of the methods is demonstrated by three different real-world examples taken from the fields of anesthesiology, orthopedics, and radiology.

The influence of injection rate on the hypnotic effect of propofol during anesthesia: a randomized trial

OBJECTIVE

Previous studies suggested that slow injection of propofol may increase the hypnotic effect during induction of anesthesia. The aim of the present study was therefore to investigate whether injection rate of propofol has an influence on its maximum effect.

DESIGN

Randomized, single-blind trial.

SETTING

This study has been carried out in the operating rooms of a university hospital. An anesthesiologist and a resident performed the study with the aid of changing nursing staff.

PARTICIPANTS

We investigated 99 unpremedicated patients aged 18 to 60 years with American Society of Anesthesiologists (ASA) physical status 1-3.

INTERVENTIONS

Anesthesia was induced by intravenous injection of propofol (2 mg/kg). Propofol was manually injected in group 1 over a period of 5 s; in group 2 (120-s injection interval), and in group 3 (240-s injection interval), propofol was administered by an injection pump. After loss of consciousness, mask ventilation was performed with 100% oxygen. Bispectral index (BIS) was used to measure the hypnotic effect of propofol. After the decrease of BIS to the minimum value (i.e., maximum hypnotic effect) and the following increase of BIS to 60, the study period was finished and anesthesia was performed according to clinical criteria.

OUTCOME MEASURES

We analyzed whether injection speed has an influence on the maximum hypnotic effect of a given dose of propofol (2 mg/kg).

RESULTS

BIS(min) marks the maximum electroencephalogram (EEG) effect of the propofol bolus as measured by the BIS. The lowest mean BIS(min) was measured in group 1 (28.7 +/- 10.3). In group 2, BIS(min) was 33.0 (+/-13.9), and in group 3, BIS(min) was 36.4 (+/-11.0). There were no significant differences between group 2 and groups 1 or 3, but there were significant differences between groups 1 and 3. In group 1, BIS(min) was reached after 102.91 s (+/-44.20), in group 2 after 172.33 s (+/-29.76), and in group 3 after 274.21 s (+/-45.40). These differences were statistically significant for all comparisons. In summary, the lowest value for BIS(min) was achieved in the group with the fastest rate of propofol injection (group1, 5 s). The highest BIS(min) was obtained in the group with the slowest rate of injection (group 3, 240 s). The hemodynamic parameters were not significantly different among groups.

CONCLUSIONS

The hypnotic peak effect of propofol is lower with extremely slow injection (240 s versus 5 s). For clinically usual injection rates (5 s and 120 s), there was no significant difference in propofol peak effect.

Contributions of GABAergic and glutamatergic mechanisms to isoflurane-induced suppression of thalamic somatosensory information transfer

Indications for a pivotal role of the thalamocortical network in producing the state of anesthesia have come from in vivo animal studies as well as imaging studies in humans. We studied possible synaptic mechanisms of anesthesia-induced suppression of touch perception in the rat's thalamus. Thalamocortical relay neurons (TCNs) receive ascending and descending glutamatergic excitatory inputs via NMDA and non-NMDA receptors (AMPAR) and are subjected to GABA(A)ergic inhibitory input which shapes the sensory information conveyed to the cortex. The involvement of these synaptic receptors in the suppressive effects of the prototypic volatile anesthetic isoflurane was assessed by local iontophoretic administration of receptor agonists/antagonists during extracellular recordings of TCNs of the ventral posteromedial nucleus responding to whisker vibration in rats anesthetized with isoflurane concentrations of approximately 0.9 vol.% (baseline) and approximately 1.9 vol.% (ISO high). ISO high induced a profound suppression of response activity reflected by a conversion of the sustained vibratory responses to ON responses. Administration of NMDA, AMPA, or GABA(A)R antagonists caused a reversal to sustained responses in 88, 94 and 88% of the neurons, respectively, with a recovery to baseline levels of response activity. The data show that the block of thalamocortical transfer of tactile information under ISO high may result from an enhancement of GABA(A)ergic inhibition and/or a reduction of glutamatergic excitation. Furthermore, they show that the ascending vibratory signals still reach the thalamic neurons under the high isoflurane concentration, indicating that this input is resistant to isoflurane while the attenuation of excitation may be brought about at the corticothalamic glutamatergic facilitatory input.

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.

Sevoflurane Impairs Cerebral Blood Flow Autoregulation in Rats: Reversal by Nonselective Nitric Oxide Synthase Inhibition

In this study, we investigated the effects of 1.0 and 2.0 minimum alveolar anesthetic concentration (MAC) sevoflurane on cerebral blood flow (CBF) autoregulation before and after nonselective inhibition of nitric oxide (NO) synthase in rats. Rats were randomly assigned as follows: Group 1 (n = 8): 1.0 MAC sevoflurane; Groups 2 and 3 (n = 8 per group): 2.0 MAC sevoflurane. Assessment of autoregulation within a mean arterial blood pressure range of 140-60 mm Hg was performed by graded hemorrhage before and after administration of l-arginine methyl ester (l-NAME, 30 mg/kg IV, Groups 1 and 2) or during hypocapnia (Group 3). In 10 additional animals, brain tissue NO(2)(-) concentrations were measured at 1.0 and 2.0 MAC sevoflurane. CBF autoregulation was maintained with 1.0 MAC sevoflurane (Group 1) regardless of NO synthase status indicating that CBF autoregulation might not be related to NO availability. Sevoflurane dose-dependently increased brain tissue NO(2)(-) and impaired CBF autoregulation. Administration of l-NAME (Group 2) but not hypocapnia (Group 3) restored CBF autoregulation. This suggests that sevoflurane impairs the autoregulatory capacity secondary to an increase of the perivascular NO availability and questions the importance of basal cerebrovascular tone in terms of vasodilatory capacity during hypotensive challenges.

IMPLICATIONS

The present study suggests that the volatile anesthetic sevoflurane dose-dependently impairs cerebrovascular autoregulation by mechanisms secondary to increase of perivascular nitric oxide availability.

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.