York A. Zausig

Cardiac effects of induction agents in the septic rat heart

IntroductionThe current debate about the side effects of induction agents, e.g. possible adrenal suppression through etomidate, emphasizes the relevance of choosing the correct induction agent in septic patients. However, cardiovascular depression is still the most prominent adverse effect of these agents, and might be especially hazardous in septic patients presenting with a biventricular cardiac dysfunction - or so-called septic cardiomyopathy. Therefore, we tested the dose-response direct cardiac effects of clinically available induction agents in an isolated septic rat heart model.MethodsA polymicrobial sepsis was induced via cecal ligation and single puncture. Hearts (n = 50) were isolated and randomly assigned to five groups, each receiving etomidate, s(+)-ketamine, midazolam, propofol, or methohexitone at concentrations of 1 × 10-8 to 1 × 10-4 M. Left ventricular pressure, contractility and lusitropy, and coronary flow were measured. Cardiac work, myocardial oxygen delivery, oxygen consumption, and percentage of oxygen extraction were calculated.ResultsAll of the induction agents tested showed a dose-dependent depression of cardiac work. Maximal cardiac work dysfunction occurred in the rank order of s(+)-ketamine (-6%) <etomidate (-17%) <methohexitone (-31%) <midazolam (-38%) <propofol (-50%). In addition, propofol showed a maximum decrease in contractility of -38%, a reduction in lusitropy of -44%, and a direct vasodilator effect by increasing coronary flow by +29%.ConclusionsOverall, this study demonstrates that these tested drugs indeed have differential direct cardiac effects in the isolated septic heart. Propofol showed the most pronounced adverse direct cardiac effects. In contrast, S(+)ketamine showed cardiovascular stability over a wide range of concentrations, and might therefore be a beneficial alternative to etomidate.

Prehospital emergency treatment of palliative care patients with cardiac arrest: a retrolective investigation.

BackgroundToday, prehospital emergency medical teams (EMTs) are confronted with emergent situations of cardiac arrest in palliative care patients. However, little is known about the out-of-hospital approach in this situation and the long-term survival rate of this specific patient type. The aim of the present investigation was to provide information about the strategic and therapeutic approach employed by EMTs in outpatient palliative care patients in cardiac arrest.MethodsDuring a period of 2xa0years, we retrolectively analysed emergency medical calls with regard to palliative care emergency situations dealing with cardiac arrest. We evaluated the numbers of patients who were resuscitated, the prevalence of an advance directive or other end-of-life protocol, the first responder on cardiac arrest, the return of spontaneous circulation (ROSC) and the survival rate.ResultsEighty-eight palliative care patients in cardiac arrest were analysed. In 19 patients (22%), no resuscitation was started. Paramedics and prehospital emergency physicians began resuscitation in 61 cases (69%) and in 8 cases (9%), respectively. A total of 10 patients (11%) showed a ROSC; none survived after 48xa0h. Advance directives were available in 43% of cases. The start of resuscitation was independent of the presence of an advance directive or other end-of-life protocol.ConclusionsStrategic and therapeutic approaches in outpatient palliative care patients with cardiac arrest differ depending on medical qualification. Although many of these patients do not wish to be resuscitated, resuscitation was started independent of the presence of advance directive. To reduce legal insecurity and to avoid resuscitation and a possible lengthening of the dying process, advance directives and/or “Do not attempt resuscitation” orders should be more readily available and should be adhered to more closely.

Toxic effects of midazolam on differentiating neurons in vitro as a consequence of suppressed neuronal Ca2+-oscillations

BACKGROUNDnIn immature neurons anesthetics induce apoptosis and influence neuronal differentiation. Neuronal Ca(2+)-oscillations regulate differentiation and synaptogenesis. We examined the effects of the long-term blockade of hippocampal Ca(2+)-oscillations with midazolam on neuronal synapsin expression.nnnMATERIAL AND METHODSnHippocampal neurons were incubated at day 15 in culture with the specific GABA(A) receptor agonist muscimol (50μM) or with midazolam (100 and 300nM), respectively, for 24h. TUNEL and activated-Caspase-3 staining were used to detect apoptotic neurons. Ca(2+)-oscillations were detected using the Ca(2+)-sensitive dye FURA-2 and dual wavelength excitation fluorescence microscopy. Synapsin was identified with confocal anti-synapsin immunofluorescence microscopy.nnnRESULTSnMuscimol, when applied for 24h, decreased the amplitude and frequency Ca(2+)-oscillations significantly. Midazolam concentration-dependently suppressed the amplitude and frequency of the Ca(2+)-oscillations. This was associated by a downregulation of the synapsin expression 24h after washout.nnnCONCLUSIONnNeuronal Ca(2+)-oscillations mediate neuronal differentiation and are involved in synaptogenesis. By acting via the GABA(A) receptor, midazolam exerts its toxic effect through the suppression of neuronal Ca(2+)-oscillations, a reduction in synapsin expression and consecutively reduced synaptic integrity.

Comparison of two different minimized extracorporeal circulation systems: hematological effects after coronary surgery.

Cardiopulmonary bypass induces hemolysis and activation of inflammatory and coagulation systems as a result of a combination of mechanical trauma and biological mechanisms. The aim of our study was to evaluate the performance of two different minimized extracorporeal circulation (ECC) systems and to compare their influence on blood components. From January 2003 to December 2008, 1,218 patients underwent coronary artery bypass grafting with minimized ECC. The PRECiSe system (41%) consists of a microporous capillary membrane oxygenator (MO) and a diagonal pump (DeltaStream DP2). The MECC system (59%) is composed of a polymethylpentene MO with a plasma-tight diffusion membrane and a centrifugal pump (RotaFlow). Serial blood samples were taken preoperatively (T0), on arrival to intensive care unit (T1), 6 hours postoperatively (T2), and at discharge (T3). Demographic data, intraoperative, and technical parameters were similar in both groups. At T1 and T2, the platelet count in the PRECiSe group was significantly lower than that in the MECC group (p < 0.01). Furthermore, at T1, levels of lactate dehydrogenase were significantly higher in the PRECiSe group (p < 0.05). In addition, postoperative blood loss was significantly higher using the PRECiSe system (p < 0.05). In conclusion, cardiac surgery with the MECC system is associated with less postoperative bleeding and improved blood cell preservation.

The impact of crystalloidal and colloidal infusion preparations on coronary vascular integrity, interstitial oedema and cardiac performance in isolated hearts

IntroductionRecent data suggested an interaction between plasma constituents and the endothelial glycocalyx to be relevant for vascular barrier function. This might be negatively influenced by infusion solutions, depending on ionic composition, pH and binding properties. The present study evaluated such an influence of current artificial preparations.MethodsIsolated guinea pig hearts were prepared in a modified Langendorff mode and perfused with Krebs-Henseleit buffer augmented with 1g% human albumin. After equilibration the perfusion was switched to replacement of one half buffer by either isotonic saline (NaCl), ringers acetate (Ri-Ac), 6% and 10% hydroxyethyl starch (6% and 10% HES, resp.), or 4% gelatine (Gel), the artificial colloids having been prepared in balanced solution. We analysed glycocalyx shedding, functional integrity of the vascular barrier and heart performance.ResultsWhile glycocalyx shedding was not observed, diluting albumin concentration towards 0.5g% by artificial solutions was associated with a marked functional breakdown of vascular barrier competence. This effect was biggest with isotonic saline and significantly attenuated with artificial colloids, the difference in the pressure dependent transvascular fluid filtration (basal vs. during infusion in groups NaCl, Ri-Ac, 6% HES, 10% HES and Gel, n = 6 each) being 0.31 ± 0.03 vs. 1.00 ± 0.04; 0.27 ± 0.03 vs. 0.81 ± 0.03; 0.29 ± 0.03 vs. 0.68 ± 0.02; 0.32 ± 0.03 vs. 0.59 ± 0.08 and 0.31 ± 0.04 vs. 0.61 ± 0.03 g/5min, respectively. Heart performance was directly related to pH value (7.38 ± 0.06, 7.33 ± 0.03, 7.14 ± 0.04, 7.08 ± 0.04, 7.25 ± 0.03), the change in the rate pressure product being 21,702 ± 1969 vs. 21,291 ± 2,552; 22,098 ± 2,115 vs. 14,114 ± 3,386; 20,897 ± 2,083 vs. 10,671 ± 1,948; 21,822 ± 2,470 vs. 10,047 ± 2,320 and 20,955 ± 2,296 vs. 15,951 ± 2,755 mmHg × bpm, respectively.ConclusionsIt appears important to maintain the pH value within a physiological range to maintain optimal myocardial contractility. Using colloids prepared in calcium-containing, balanced solutions for volume replacement therapy may attenuate the breakdown of vascular barrier competence in the critically ill.

Lipid emulsion pretreatment has different effects on mepivacaine and bupivacaine cardiac toxicity in an isolated rat heart model

BACKGROUNDnThe use of lipid emulsions to reduce cardiac toxicity of local anaesthetics (LAs) has shown success in experimental studies and some clinical cases, and thus has been implemented in clinical practice. However, lipid treatment is usually given after the occurrence of neurological or cardiovascular symptoms of systemic intoxication. The aim of this study was to determine if pretreatment with lipid emulsion reduces cardiac toxicity produced by bupivacaine or mepivacaine.nnnMETHODSnIsolated rat hearts were perfused with or without lipid emulsion (0.25 ml kg(-1) min(-1)) before administration of equipotent doses of bupivacaine (250 µM) or mepivacaine (1000 µM). Haemodynamic parameters and times from start of perfusion LA to a 1 min period of asystole and recovery were determined.nnnRESULTSnPretreatment with lipid emulsion extended the time until occurrence of asystole and decreased times to recovery in bupivacaine-induced cardiac toxicity but not in mepivacaine-induced cardiac toxicity compared with control. Lipid pretreatment impaired rate-pressure product recovery in mepivacaine-intoxicated hearts.nnnCONCLUSIONSnThis study confirms that pretreatment with a lipid emulsion reduces cardiac toxicity of LAs. The efficacy of pretreatment with lipid emulsion was LA-dependent, so pharmacokinetic properties, such as lipophilicity, might influence the effects of lipid emulsion pretreatment.

Species- and concentration-dependent differences of acetyl- and butyrylcholinesterase sensitivity to physostigmine and neostigmine

Previous and more recent studies show that cholinesterase inhibitors (ChE-Is) are an important possibility for therapeutic intervention in Alzheimers Disease, sepsis and other inflammatory syndromes. ChE-Is maintain high levels of acetylcholine (ACh) determining beneficial effects on the disease process. Despite numerous efforts to identify the appropriate choice of agents and dose of ChE-Is, a common protocol regarding concentration- and species-dependent differences in inhibitory potency (IC 50) of clinical relevant ChE-Is is still not available. To evaluate the inxa0vitro sensitivity of Acetyl- and Butyrylcholinesterase (AChE, BChE), we compared the concentration-response effects of physostigmine and neostigmine on cholinesterases in whole blood from rat and human. A spectrophotometrical test system based on inxa0vitro Ellmans reagent has been used to determine the kinetic properties of clinical relevant ChE-Is. Inxa0vitro, the enzyme activity of human AChE and BChE was inhibited in a concentration-dependent manner until a residual activity of 4-6% for AChE and 20-30% for BChE (IC 50 human AChE: 0.117xa0±xa00.007xa0μM physostigmine, 0.062xa0±xa00.003xa0μM neostigmine; IC 50 human BChE: 0.373xa0±xa00.089xa0μM neostigmine; 0.059xa0±xa00.012xa0μM physostigmine). The inhibition curve of rat BChE in contrast showed no concentration-dependency for physostigmine and neostigmine (87% residual activity even at high inhibitor concentrations). Rat AChE was inhibited in a concentration-dependent manner until a residual activity of 53%. The results suggest that cholinesterases from human and rat show marked species- and inhibitor-dependent differences in sensitivity to physostigmine and neostigmine. Knowledge of such differences may be critical in assessing the possible therapeutic effects of ChE-Is in both species and may guide researchers in the optimal design of future experiments regarding the application of ChE-Is.

Modulation of immune functions in polymorphonuclear neutrophils induced by physostigmine, but not neostigmine, independent of cholinergic neurons.

BACKGROUNDnCholinesterase inhibitors (Ch-I) improve survival in experimental sepsis consistent with activation of the cholinergic-anti-inflammatory-pathway. So far, less is known about whether Ch-I have a direct immunomodulatory effect on immune cells (polymorphonuclear neutrophils, PMN) in the absence of cholinergic neurons. We investigated the concentration-response-effects of physostigmine and neostigmine on the oxidative burst activity (human and rat PMN) and the expression of adhesion molecules on the surface of human PMN under in vitro conditions.nnnMETHODSnPMN from 10 healthy humans or 10 rats were pretreated with 2, 10, 24, 97 μM physostigmine or 3, 15, 30, 150 μM neostigmine, primed with tumor-necrosis-factor-alpha (TNF-alpha) followed by stimulation with n-formyl-methionyl-leucylphenylalanine (fMLP) or stimulated with phorbol-12-myristate-13-acetate (PMA). Human and rat samples were assessed by flow cytometry for the generation of oxidative free radicals. Stimulated human PMN were additionally incubated with antibodies against Mac-1 (CD11b) or L-selectin (CD62l).nnnRESULTSnPhysostigmine and neostigmine did not alter oxidative burst activity or the expression of adhesion molecules of PMN induced by receptor-dependent activators like fMLP or TNF-alpha/fMLP (rat and human PMN, p=n.s.). Physostigmine, but not neostigmine, inhibited the protein-kinase-C-mediated oxidative burst activity by PMA in a dose-dependent manner (rat and human PMN, p<0.05). Physostigmine, in the concentration range tested, suppressed the expression of CD11b following stimulation with PMA not significantly (human PMN: control: 63.1±10.7 vs. 97 μM physostigmine: 49.9±12.8 MESF, p=n.s.).nnnCONCLUSIONnWhile neostigmine has no effect on functional and phenotypic changes of PMN, the lipid soluble Ch-I physostigmine causes a dose dependent reduction in PMA-induced oxidative burst, independent of neuronal released acetylcholine.

Clinical Experience Does Not Correlate with the Perceived Need for Cardiopulmonary Resuscitation Training

BACKGROUNDnThe efficiency of cardiopulmonary resuscitation (CPR) training is dependent upon different influencing factors, such as the presented concepts, the participants willingness to learn, and the interval between training sessions. However, the optimal interval for refreshing CPR training is less clear.nnnOBJECTIVEnWe evaluated the perceived need of simulator-based CPR training for nurses and correlated it with their clinical experience.nnnMETHODSnThe 60 invited nurses were trained in simulator-based CPR. Knowledge about adult advanced life support was evaluated using a questionnaire after training, and participants rated their desired individual frequency of simulator-based training as well as the value of the presented training using a six-point Likert scale. The same questions were asked again after 1 year.nnnRESULTSnAll participants agreed about the usefulness of this type of simulator-based training. The average number of correct answers about typical facts in adult advanced life support showed an almost bell-shaped distribution, with the highest point at 6-15 years of clinical experience and the lowest points at≤5 and≥21 years. The desired training-frequency need was inversely correlated with clinical experience.nnnCONCLUSIONSnThere is a high interest in CPR training among nursing staff. Self-assessment about the training-frequency need was inversely correlated with clinical experience. However, the average number of correct answers on resuscitation questions decreased with clinical experience. Therefore, thexa0training effectiveness seems to be extremely dependent on clinical experience, and therefore, training experienced senior nurses might be more challenging than training novice nurses.