Thomas Pasch

Preconditioning by Sevoflurane Decreases Biochemical Markers for Myocardial and Renal Dysfunction in Coronary Artery Bypass Graft Surgery: A Double-blinded, Placebo-controlled, Multicenter Study

Background Preconditioning by volatile anesthetics is a promising therapeutic strategy to render myocardial tissue resistant to perioperative ischemia. It was hypothesized that sevoflurane preconditioning would decrease postoperative release of brain natriuretic peptide, a biochemical marker for myocardial dysfunction. In addition, several variables associated with the protective effects of preconditioning were evaluated. Methods Seventy-two patients scheduled for coronary artery bypass graft surgery under cardioplegic arrest were randomly assigned to preconditioning during the first 10 min of complete cardiopulmonary bypass with either placebo (oxygen–air mixture only) or sevoflurane 4 vol% (2 minimum alveolar concentration). No other volatile anesthetics were administered at any time during the study. Treatment was strictly blinded to anesthesiologists, perfusionists, and surgeons. Biochemical markers of myocardial dysfunction and injury (brain natriuretic peptide, creatine kinase–MB activity, and cardiac troponin T), and renal dysfunction (cystatin C) were determined. Results of Holter electrocardiography were recorded perioperatively. Translocation of protein kinase C was assessed by immunohistochemical analysis of atrial samples. Results Sevoflurane preconditioning significantly decreased postoperative release of brain natriuretic peptide, a sensitive biochemical marker of myocardial contractile dysfunction. Pronounced protein kinase C &dgr; and &egr; translocation was observed in sevoflurane-preconditioned myocardium. In addition, postoperative plasma cystatin C concentrations increased significantly less in sevoflurane-preconditioned patients. No differences between groups were found for perioperative ST-segment changes, arrhythmias, or creatine kinase–MB and cardiac troponin T release. Conclusions Sevoflurane preconditioning preserves myocardial and renal function as assessed by biochemical markers in patients undergoing coronary artery bypass graft surgery under cardioplegic arrest. This study demonstrated for the first time translocation of protein kinase C isoforms &dgr; and &egr; in human myocardium in response to sevoflurane.

Volatile anesthetics mimic cardiac preconditioning by priming the activation of mitochondrial KATP channels via multiple signaling pathways

Background Volatile anesthetics induce pharmacological preconditioning in cardiac tissue. The purpose of this study was to test whether volatile anesthetics mediate this effect by activation of the mitochondrial adenosine triphosphate–sensitive potassium (mitoKATP) or sarcolemmal KATP (sarcKATP) channel in rat ventricular myocytes and to evaluate the signaling pathways involved. Methods A cellular model of ischemia with subsequent hypoosmolar trypan blue staining served to determine the effects of 5-hydroxydecanoate, a selective mitoKATP channel blocker, HMR-1098, a selective sarcKATP channel blocker, diazoxide, a preconditioning mimicking agent, and various modulators of putative signaling pathways on cardioprotection elicited by sevoflurane and isoflurane. Microscopy was used to visualize and measure autofluorescence of flavoproteins, a direct index of mitoKATP channel activity. Results Volatile anesthetics significantly enhanced diazoxide-mediated activation of mitoKATP channels as assessed by autofluorescence of myocytes. Conversely, volatile anesthetics alone did not alter mitoKATP channel activity, implying a priming effect of volatile anesthetics on mitoKATP channels. Administration of the protein kinase C inhibitor chelerythrine completely blocked this effect. Also, pretreatment with volatile anesthetics potentiated diazoxide-mediated protection against ischemia, as indicated by a reduction in trypan blue–positive myocytes. Importantly, cardioprotection afforded by volatile anesthetics was unaffected by the sarcKATP channel blocker HMR-1098 but sensitive to modulations of nitric oxide and adenosine–Gi signaling pathways. Conclusions Using autofluorescence in live cell imaging microscopy and a simulated model of ischemia, the authors present evidence that volatile anesthetics mediate their protection in cardiomyocytes by selectively priming mitoKATP channels through multiple triggering protein kinase C–coupled signaling pathways. These observations provide important new insight into the mechanisms of anesthetic-induced preconditioning.

Cardiovascular and coronary physiology of acute isovolemic hemodilution : a review of nonoxygen-carrying and oxygen-carrying solutions

Acute isovolemic hemodilution is used increasingly to avoid the potentially serious side effects of homologous blood transfusions. Cardiovascular physiology during hemodilution is characterized by a marked increase in cardiac output and organ blood flow to compensate for the decrease in arterial oxygen-carrying capacity. During advanced hemodilution an increased oxygen extraction is also observed, such that oxygen consumption generally is maintained even during advanced hemodilution. The increase in cardiac output is related mainly to a decrease in blood viscosity and an enhanced sympathetic tone resulting in stimulation of the heart. The magnitude and the mechanisms involved in the increase depend upon species, state of awareness (awake versus anesthetized), type of anesthesia, type of exchange solution, and condition of the heart prior to hemodilution. Recent laboratory findings, as well as clinical practice in cardiac surgery, suggest that moderate hemodilution to hematocrit values of approximately 25% is well tolerated in single vessel coronary artery disease which should thus not be regarded as an absolute contraindication for moderate hemodilution. An integral concept to minimize homologous blood transfusions consists of preoperative autologous blood donation, preoperative isovolemic hemodilution, meticulous (asanguineous) surgical technique, and acceptance of minimum hemoglobin levels during the entire hospitalization. The incidence of homologous blood transfusions will be reduced using acute isovolemic hemodilution. This incidence will be further reduced once hemoglobin solutions become clinically available for specific indications. At present, research activities are concentrated on defining the critical level of hemodilution in various pathologic conditions and to investigate pharmacology and physiology of the new hemoglobin solutions. Finally, several chemically modified hemoglobin-based oxygen-carrying solutions devoid of renal toxicity will be available in the future. The cardiovascular physiology and pharmacology of these hemoglobin solutions have been studied. Cardiac output is generally constant and oxygen extraction is increased to maintain oxygen consumption during hemodilution with hemoglobin solutions. In most studies, some vasoconstriction was observed also, which might result from interaction of the hemoglobin molecule with the EDRF/NO system. However, with enhanced purification, chemical modification or microencapsulation of the hemoglobin molecule, vasoconstriction can be limited.

Isoflurane postconditioning prevents opening of the mitochondrial permeability transition pore through inhibition of glycogen synthase kinase 3β

Background:Postischemic administration of volatile anesthetics activates reperfusion injury salvage kinases and decreases myocardial damage. However, the mechanisms underlying anesthetic postconditioning are unclear. Methods:Isolated perfused rat hearts were exposed to 40 min of ischemia followed by 1 h of reperfusion. Anesthetic postconditioning was induced by 15 min of 2.1 vol% isoflurane (1.5 minimum alveolar concentration) administered at the onset of reperfusion. In some experiments, atractyloside (10 &mgr;m), a mitochondrial permeability transition pore (mPTP) opener, and LY294002 (15 &mgr;m), a phosphatidylinositol 3-kinase inhibitor, were coadministered with isoflurane. Western blot analysis was used to determine phosphorylation of protein kinase B/Akt and its downstream target glycogen synthase kinase 3β after 15 min of reperfusion. Myocardial tissue content of nicotinamide adenine dinucleotide served as a marker for mPTP opening. Accumulation of MitoTracker Red 580 (Molecular Probes, Invitrogen, Basel, Switzerland) was used to visualize mitochondrial function. Results:Anesthetic postconditioning significantly improved functional recovery and decreased infarct size (36 ± 1% in unprotected hearts vs. 3 ± 2% in anesthetic postconditioning; P < 0.05). Isoflurane-mediated protection was abolished by atractyloside and LY294002. LY294002 inhibited isoflurane-induced phosphorylation of protein kinase B/Akt and glycogen synthase kinase 3β and opened mPTP as determined by nicotinamide adenine dinucleotide measurements. Atractyloside, a direct opener of the mPTP, did not inhibit phosphorylation of protein kinase B/Akt and glycogen synthase kinase 3β by isoflurane but reversed isoflurane-mediated cytoprotection. Microscopy showed accumulation of the mitochondrial tracker in isoflurane-protected functional mitochondria but no staining in mitochondria of unprotected hearts. Conclusions:Anesthetic postconditioning by isoflurane effectively protects against reperfusion damage by preventing opening of the mPTP through inhibition of glycogen synthase kinase 3β.

Translocation of Protein Kinase C Isoforms to Subcellular Targets in Ischemic and Anesthetic Preconditioning

Background Translocation of protein kinase C (PKC) to subcellular targets is a pivotal signaling step in ischemic preconditioning (IPC). However, to date, it is unknown whether PKC isoforms translocate in anesthetic preconditioning (APC). Methods The PKC blockers chelerythrine and rottlerin and the adenosine triphosphate–dependent potassium (KATP) channel blockers HMR-1098 and 5-hydroxydecanoate were used to assess the role of PKC and KATP channels in isolated perfused rat hearts subjected to IPC or APC (1.5 minimum alveolar concentration isoflurane) followed by 40 min of ischemia and 30 min of reperfusion. Immunohistochemical techniques were used to visualize PKC translocation after preconditioning. In addition, the phosphorylation status of PKC isoforms was assessed. Results Chelerythrine, rottlerin, and 5-hydroxydecanoate blocked IPC and APC with respect to functional recovery, albeit IPC at higher concentrations. HMR-1098 did not affect IPC or APC. PKC&dgr; and PKC&egr; translocated to nuclei in both IPC and APC, which was inhibited by chelerythrine and rottlerin. PKC&dgr; translocated to mitochondria but not to the sarcolemma, and PKC&egr; translocated to the sarcolemma and intercalated disks but not to mitochondria. Interestingly, PKC&egr; was accumulated at the intercalated disks in control and preconditioned hearts. Phosphorylation of PKC&dgr; on serine643 was increased in IPC and APC and blocked by chelerythrine and rottlerin, whereas phosphorylation of PKC&dgr; on threonine505 was increased only in IPC and not blocked by chelerythrine or rottlerin. PKC&egr; on serine729 did not change its phosphorylation status. Conclusions This study indicates that translocation of PKC&dgr; plays a pivotal role in IPC and APC and suggests that phosphorylation of PKC&dgr; on serine643 may be of particular relevance in transferring the APC stimulus to mitochondrial KATP channels.

Hemodilution tolerance in patients with coronary artery disease who are receiving chronic beta-adrenergic blocker therapy

Hemodilution tolerance is not well defined in patients with coronary artery disease receiving beta-adrenergic blockers chronically. Ninety patients scheduled for coronary artery bypass graft (CABG) surgery were randomized to a hemodilution (n = 60) and a control group (n = 30). During midazolam-fentanyl anesthesia, hemodynamic variables, ST segment deviation, and O2 consumption were determined prior to and after 6 and 12 mL/kg isovolemic exchange of blood for 6% hydroxyethyl starch. Hemoglobin decreased from 12.6 +/- 0.2 to 9.9 +/- 0.2 g/dL (mean +/- SEM, P < 0.05). With stable filling pressures, cardiac index increased from 2.05 +/- 0.05 to 2.27 +/- 0.05 L centered dot min-1 centered dot m-2 (P < 0.05) and O2 extraction from 27.4% +/- 0.6% to 31.2% +/- 0.7% (P < 0.05), resulting in stable O2 consumption. No alterations in ST segments were observed in leads II and V5 during hemodilution. Individual increases in cardiac index and O2 extraction were not linearly related to age and left ventricular (LV) ejection fraction (P = 0.841, P = 0.799). We conclude that isovolemic hemodilution to a hemoglobin value of 9.9 +/- 0.2 g/dL is well tolerated and fully compensated in patients with coronary artery disease receiving beta-adrenergic blockers chronically. Within the investigated ranges, the compensatory mechanisms during hemodilution are largely independent of age (35-81 yr) and LV ejection fraction (26%-83%). (Anesth Analg 1996;82:687-94)

ABCA1 modulates CSF cholesterol levels and influences the age at onset of Alzheimer’s disease

Increased formation of the beta-amyloid peptide (Abeta) is a central event in the pathogenesis of Alzheimers disease (AD). High cellular cholesterol load promotes Abeta formation. The ATP-binding cassette transporter A1 (ABCA1) mediates cholesterol efflux from cells. We hypothesized that genetic variability in ABCA1 may influence cholesterol metabolism in the central nervous system (CNS) and, thus, interfere with the development of AD. Healthy elderly carriers of the A allele of a non-synonymous (R219K) single nucleotide polymorphism (SNP) in the ABCA1 gene (rs2234884) had on average 33% lower total cholesterol in cerebrospinal fluid (CSF) than non-carriers. In 169 patients with late onset, sporadic AD, this allele was associated with delayed age at onset of the disease by 1.7 years on average. Rs2234884 and another non-synonymous SNP (R1587K) in ABCA1 (rs2234886) failed to show significant association with the risk for AD. We conclude that genetic variability of ABCA1 influences the development of AD, possibly by interfering with CNS cholesterol homeostasis.

Citrate storage affects Thrombelastograph® analysis

Background Thrombelastograph® analysis (TEG®) is used to evaluate blood coagulation. Ideally, whole blood is immediately processed. If impossible, blood may be citrated and assessed after recalcification. No data describe the effect of such treatment and storage on TEG® parameters. Methods Three studies were performed in 90 surgical patients. In 30 patients, blood was citrated (1:10, 0.129 M) and recalcified (20 &mgr;l 2 M CaCl2 to 340 &mgr;l citrated blood), and TEG® was performed with native blood and after recalcification after 0, 15, and 30 min of citrate storage. In another 30 patients, TEG® was performed with citrated blood recalcified immediately and after 1–72 h storage. In a third study, thrombin–antithrombin complex, prothrombin fragment 1+2, and &bgr;-thromboglobulin were measured (using enzyme-linked immunoabsorbant assay tests) at corresponding time points. Data were compared using repeated-measures analysis of variance and post hoc paired t tests. Results TEG® parameters were different in recalcified citrated blood compared with native blood (P < 0.05) and changed significantly during 30-min (P < 0.025) and 72-h (P < 0.001) citrate storage. TEG® parameters measured between 1 and 8 h of citrate storage were stable. Thrombin–antithrombin complex and prothrombin fragment 1+2 values were not elevated in native blood. After 30 min of citrate storage a gradual thrombin activation was observed, as evidenced by increasing thrombin–antithrombin complex and prothrombin fragment 1+2 values (P < 0.05). &bgr;-Thromboglobulin level was increased after 2 and 8 h of citrate storage (P < 0.01). Conclusions Analysis of native blood yields the most reliable TEG® results. Should immediate TEG® processing not be possible, citrated blood may be used if recalcified after 1–8 h.

Alveolar macrophages regulate neutrophil recruitment in endotoxin-induced lung injury

BackgroundAlveolar macrophages play an important role during the development of acute inflammatory lung injury. In the present study, in vivo alveolar macrophage depletion was performed by intratracheal application of dichloromethylene diphosphonate-liposomes in order to study the role of these effector cells in the early endotoxin-induced lung injury.MethodsLipopolysaccharide was applied intratracheally and the inflammatory reaction was assessed 4 hours later. Neutrophil accumulation and expression of inflammatory mediators were determined. To further analyze in vivo observations, in vitro experiments with alveolar epithelial cells and alveolar macrophages were performed.ResultsA 320% increase of polymorphonuclear leukocytes in bronchoalveolar lavage fluid was observed in macrophage-depleted compared to macrophage-competent lipopolysaccharide-animals. This neutrophil recruitment was also confirmed in the interstitial space. Monocyte chemoattractant protein-1 concentration in bronchoalveolar lavage fluid was significantly increased in the absence of alveolar macrophages. This phenomenon was underlined by in vitro experiments with alveolar epithelial cells and alveolar macrophages. Neutralizing monocyte chemoattractant protein-1 in the airways diminished neutrophil accumulation.ConclusionThese data suggest that alveolar macorphages play an important role in early endotoxin-induced lung injury. They prevent neutrophil influx by controlling monocyte chemoattractant protein-1 production through alveolar epithelial cells. Alveolar macrophages might therefore possess robust anti-inflammatory effects.

Complaints of sore throat after tracheal intubation: a prospective evaluation

Background and objective: Sore throat and hoarseness rank, besides pain and nausea, among the most frequent subjective complaints after tracheal intubation for general anaesthesia. Our intention was to determine the incidence of postoperative sore throat from a large sample of patients and thus to identify the most important associated factors. Methods: We prospectively followed up 809 adult patients who underwent elective surgical interventions and examined their history, the applied anaesthetic techniques, perioperative course and the occurrence, intensity and duration of postoperative throat complaints. The assignment and professional experience of the involved intubators were also assessed. The influence of a multitude of variables on postoperative throat complaints was statistically analysed. Results: Postoperative sore throat was present in 40% overall being significantly higher in female than in male (44% vs. 33%; P = 0.001). The mean pain intensity in the affected patients (n = 323) was 28 ± 12 mm on a visual analogue scale where 0 = no pain and 100 = extreme pain. The average duration was 16 ± 11 h. Main factors associated with throat complaints were female sex, history of smoking or lung disease, duration of anaesthesia, postoperative nausea, bloodstain on the endotracheal tube and natural teeth. We could find no influence on the occurrence or intensity of throat complaints by the professional assignment or the length of professional experience of the personnel involved. Conclusions: Postoperative throat complaints frequently arise after tracheal intubation for general anaesthesia in the first 2 postoperative days, but they are of limited intensity and duration.