A Guide to Understanding "State-of-the-Art" Basic Research Techniques in Anesthesiology.

Perioperative medicine is changing from a "protocol-based" approach to a progressively personalized care model. New molecular techniques and comprehensive perioperative medical records allow for detection of patient-specific phenotypes that may better explain, or even predict, a patient's response to perioperative stress and anesthetic care. Basic science technology has significantly evolved in recent years with the advent of powerful approaches that have translational relevance. It is incumbent on us as a primarily clinical specialty to have an in-depth understanding of rapidly evolving underlying basic science techniques to incorporate such approaches into our own research, critically interpret the literature, and improve future anesthesia patient care. This review focuses on 3 important and most likely practice-changing basic science techniques: next-generation sequencing (NGS), clustered regularly interspaced short palindromic repeat (CRISPR) modulations, and inducible pluripotent stem cells (iPSCs). Each technique will be described, potential advantages and limitations discussed, open questions and challenges addressed, and future developments outlined. We hope to provide insight for practicing physicians when confronted with basic science articles and encourage investigators to apply "state-of-the-art" technology to their future experiments.

TRPA1 channel contributes to myocardial ischemia-reperfusion injury.

Myocardial ischemia-reperfusion (I/R) results in the generation of free radicals, accumulation of lipid peroxidation-derived unsaturated aldehydes, variable angina (pain), and infarction. The transient receptor potential ankyrin 1 (TRPA1) mediates pain signaling and is activated by unsaturated aldehydes, including acrolein and 4-hydroxynonenal. The contribution of TRPA1 (a Ca2+-permeable channel) to I/R-induced myocardial injury is unknown. We tested the hypothesis that cardiac TRPA1 confers myocyte sensitivity to aldehyde accumulation and promotes I/R injury. Although basal cardiovascular function in TRPA1-null mice was similar to that in wild-type (WT) mice, infarct size was significantly smaller in TRPA1-null mice than in WT mice (34.1 ± 9.3 vs. 14.3 ± 9.9% of the risk region, n = 8 and 7, respectively, P < 0.05), despite a similar I/R-induced area at risk (40.3 ±8.4% and 42.2 ± 11.3% for WT and TRPA1-null mice, respectively) after myocardial I/R (30 min of ischemia followed by 24 h of reperfusion) in situ. Positive TRPA1 immunofluorescence was present in murine and human hearts and was colocalized with connexin43 at intercalated disks in isolated murine cardiomyocytes. Cardiomyocyte TRPA1 was confirmed by quantitative RT-PCR, DNA sequencing, Western blot analysis, and electrophysiology. A role of TRPA1 in cardiomyocyte toxicity was demonstrated in isolated cardiomyocytes exposed to acrolein, an I/R-associated toxin that induces Ca2+ accumulation and hypercontraction, effects significantly blunted by HC-030031, a TRPA1 antagonist. Protection induced by HC-030031 was quantitatively equivalent to that induced by SN-6, a Na+/Ca2+ exchange inhibitor, further supporting a role of Ca2+ overload in acrolein-induced cardiomyocyte toxicity. These data indicate that cardiac TRPA1 activation likely contributes to I/R injury and, thus, that TRPA1 may be a novel therapeutic target for decreasing myocardial I/R injury. NEW & NOTEWORTHY Transient receptor potential ankyrin 1 (TRPA1) activation mediates increased blood flow, edema, and pain reception, yet its role in myocardial ischemia-reperfusion (I/R) injury is unknown. Genetic ablation of TRPA1 significantly decreased myocardial infarction after I/R in mice. Functional TRPA1 in cardiomyocytes was enriched in intercalated disks and contributed to acrolein-induced Ca2+ overload and hypercontraction. These data indicate that I/R activation of TRPA1 worsens myocardial infarction; TRPA1 may be a potential target to mitigate I/R injury.

Exercise-Induced Changes in Glucose Metabolism Promote Physiological Cardiac Growth.

BACKGROUND: Exercise promotes metabolic remodeling in the heart, which is associated with physiological cardiac growth; however, it is not known whether or how physical activity-induced changes in cardiac metabolism cause myocardial remodeling. In this study, we tested whether exercise-mediated changes in cardiomyocyte glucose metabolism are important for physiological cardiac growth. METHODS: We used radiometric, immunologic, metabolomic, and biochemical assays to measure changes in myocardial glucose metabolism in mice subjected to acute and chronic treadmill exercise. To assess the relevance of changes in glycolytic activity, we determined how cardiac-specific expression of mutant forms of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase affect cardiac structure, function, metabolism, and gene programs relevant to cardiac remodeling. Metabolomic and transcriptomic screenings were used to identify metabolic pathways and gene sets regulated by glycolytic activity in the heart. RESULTS: Exercise acutely decreased glucose utilization via glycolysis by modulating circulating substrates and reducing phosphofructokinase activity; however, in the recovered state following exercise adaptation, there was an increase in myocardial phosphofructokinase activity and glycolysis. In mice, cardiac-specific expression of a kinase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase transgene (GlycoLo mice) lowered glycolytic rate and regulated the expression of genes known to promote cardiac growth. Hearts of GlycoLo mice had larger myocytes, enhanced cardiac function, and higher capillary-to-myocyte ratios. Expression of phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in the heart (GlycoHi mice) increased glucose utilization and promoted a more pathological form of hypertrophy devoid of transcriptional activation of the physiological cardiac growth program. Modulation of phosphofructokinase activity was sufficient to regulate the glucose-fatty acid cycle in the heart; however, metabolic inflexibility caused by invariantly low or high phosphofructokinase activity caused modest mitochondrial damage. Transcriptomic analyses showed that glycolysis regulates the expression of key genes involved in cardiac metabolism and remodeling. CONCLUSIONS: Exercise-induced decreases in glycolytic activity stimulate physiological cardiac remodeling, and metabolic flexibility is important for maintaining mitochondrial health in the heart.

Genetic Deficiency of Glutathione S-Transferase P Increases Myocardial Sensitivity to Ischemia-Reperfusion Injury.

RATIONALE: Myocardial ischemia-reperfusion (I/R) results in the generation of oxygen-derived free radicals and the accumulation of lipid peroxidation-derived unsaturated aldehydes. However, the contribution of aldehydes to myocardial I/R injury has not been assessed. OBJECTIVE: We tested the hypothesis that removal of aldehydes by glutathione S-transferase P (GSTP) diminishes I/R injury. METHODS AND RESULTS: In adult male C57BL/6 mouse hearts, Gstp1/2 was the most abundant GST transcript followed by Gsta4 and Gstm4.1, and GSTP activity was a significant fraction of the total GST activity. mGstp1/2 deletion reduced total GST activity, but no compensatory increase in GSTA and GSTM or major antioxidant enzymes was observed. Genetic deficiency of GSTP did not alter cardiac function, but in comparison with hearts from wild-type mice, the hearts isolated from GSTP-null mice were more sensitive to I/R injury. Disruption of the GSTP gene also increased infarct size after coronary occlusion in situ. Ischemia significantly increased acrolein in hearts, and GSTP deficiency induced significant deficits in the metabolism of the unsaturated aldehyde, acrolein, but not in the metabolism of 4-hydroxy-trans-2-nonenal or trans-2-hexanal; on ischemia, the GSTP-null hearts accumulated more acrolein-modified proteins than wild-type hearts. GSTP deficiency did not affect I/R-induced free radical generation, c-Jun N-terminal kinase activation, or depletion of reduced glutathione. Acrolein exposure induced a hyperpolarizing shift in INa, and acrolein-induced cell death was delayed by SN-6, a Na(+)/Ca(++) exchange inhibitor. Cardiomyocytes isolated from GSTP-null hearts were more sensitive than wild-type myocytes to acrolein-induced protein crosslinking and cell death. CONCLUSIONS: GSTP protects the heart from I/R injury by facilitating the detoxification of cytotoxic aldehydes, such as acrolein.

Cardioprotection by Poloxamer 188 is Mediated through Increased Endothelial Nitric Oxide Production.

Ischemia/reperfusion (I/R) injury significantly contributes to the morbidity and mortality associated with cardiac events. Poloxamer 188 (P188), a nonionic triblock copolymer, has been proposed to mitigate I/R injury by stabilizing cell membranes. However, the underlying mechanisms remain incompletely understood, particularly concerning endothelial cell function and nitric oxide (NO) production. We employed human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) and endothelial cells (ECs) to elucidate the effects of P188 on cellular survival, function, and NO secretion under simulated I/R conditions. iPSC-CMs contractility and iPSC-ECs' NO production were assessed following exposure to P188. Further, an isolated heart model using Brown Norway rats subjected to I/R injury was utilized to evaluate the ex-vivo cardioprotective effects of P188, examining cardiac function and NO production, with and without the administration of a NO inhibitor. In iPSC-derived models, P188 significantly preserved CM contractile function and enhanced cell viability after hypoxia/reoxygenation. Remarkably, P188 treatment led to a pronounced increase in NO secretion in iPSC-ECs, a novel finding demonstrating endothelial protective effects beyond membrane stabilization. In the rat isolated heart model, administration of P188 during reperfusion notably improved cardiac function and reduced I/R injury markers. This cardioprotective effect was abrogated by NO inhibition, underscoring the pivotal role of NO. Additionally, a dose-dependent increase in NO production was observed in non-ischemic rat hearts treated with P188, further establishing the critical function of NO in P188 induced cardioprotection. In conclusion, our comprehensive study unveils a novel role of NO in mediating the protective effects of P188 against I/R injury. This mechanism is evident in both cellular models and intact rat hearts, highlighting the potential of P188 as a therapeutic agent against I/R injury. Our findings pave the way for further investigation into P188's therapeutic mechanisms and its potential application in clinical settings to mitigate I/R-related cardiac dysfunction.

Detecting and measuring of GPCR signaling - comparison of human induced pluripotent stem cells and immortal cell lines.

G protein-coupled receptors (GPCRs) are a large family of transmembrane proteins that play a major role in many physiological processes, and thus GPCR-targeted drug development has been widely promoted. Although research findings generated in immortal cell lines have contributed to the advancement of the GPCR field, the homogenous genetic backgrounds, and the overexpression of GPCRs in these cell lines make it difficult to correlate the results with clinical patients. Human induced pluripotent stem cells (hiPSCs) have the potential to overcome these limitations, because they contain patient specific genetic information and can differentiate into numerous cell types. To detect GPCRs in hiPSCs, highly selective labeling and sensitive imaging techniques are required. This review summarizes existing resonance energy transfer and protein complementation assay technologies, as well as existing and new labeling methods. The difficulties of extending existing detection methods to hiPSCs are discussed, as well as the potential of hiPSCs to expand GPCR research towards personalized medicine.

Nasopharyngeal Ventilation Compared to Facemask Ventilation: A Prospective, Randomized, Crossover Trial in Two Different Elective Cohorts.

BACKGROUND: Facemask ventilation is routinely used to preoxygenate patients before endotracheal intubation during anesthesia induction or to secure ventilation in patients with respiratory insufficiency. Occasionally, facemask ventilation cannot be performed adequately. The placement of a regular endotracheal tube through the nose into the hypopharynx may be a valid alternative to improve ventilation and oxygenation before endotracheal intubation (nasopharyngeal ventilation). We tested the hypothesis that nasopharyngeal ventilation is superior in its efficacy compared to traditional facemask ventilation. METHODS: In this prospective, randomized, crossover trial, we enrolled surgical patients requiring either nasal intubation (cohort #1, n = 20) or patients who met "difficult to mask ventilate" criteria (cohort #2, n = 20). Patients in each cohort were randomly assigned to receive pressure-controlled facemask ventilation followed by nasopharyngeal ventilation or vice versa. The ventilation settings were kept constant. The primary outcome was tidal volume. The secondary outcome was the difficulty of ventilation, measured using the Warters grading scale. RESULTS: Tidal volume was significantly increased by nasopharyngeal ventilation in cohort #1 (597 ± 156 ml vs.462 ± 220 ml, p = 0.019) and cohort #2 (525 ± 157 ml vs.259 ± 151 ml, p < 0.01). Warters grading scale for mask ventilation was 0.6 ± 1.4 in cohort #1, and 2.6 ± 1.5 in cohort #2. CONCLUSION: Patients at risk for difficult facemask ventilation may benefit from nasopharyngeal ventilation to maintain adequate ventilation and oxygenation before endotracheal intubation. This ventilation mode may offer another option for ventilation at induction of anesthesia and during the management of respiratory insufficiency, especially in the setting of "unexpected" ventilation difficulty.

Generation of two induced pluripotent stem cell lines from patients suffering from pulmonary hypertension.

Idiopathic pulmonary arterial hypertension (IPAH) is a rare disease, with an estimated 500-1000 new cases diagnosed every year. A portion of these cases may be caused by mutations in the BMPR2 gene, suggesting a possible genetic component in the development of the disease. Here, we report two human induced pluripotent stem cell (iPSC) lines generated from IPAH patients. Both cell lines provide valuable insight into the molecular and cellular mechanisms of IPAH and can be used to further understand the disease.

Cardiomyocyte-restricted overexpression of extracellular superoxide dismutase increases nitric oxide bioavailability and reduces infarct size after ischemia/reperfusion.

Increased levels of extracellular superoxide dismutase (ecSOD) induced by preconditioning or gene therapy protect the heart from ischemia/reperfusion injury. To elucidate the mechanism responsible for this action, we studied the effects of increased superoxide scavenging on nitric oxide (NO) bioavailability in a cardiac myocyte-specific ecSOD transgenic (Tg) mouse. Results indicated that ecSOD overexpression increased cardiac myocyte-specific ecSOD activity 27.5-fold. Transgenic ecSOD was localized to the sarcolemma and, notably, the cytoplasm of cardiac myocytes. Ischemia/reperfusion injury was attenuated in ecSOD Tg hearts, in which infarct size was decreased and LV functional recovery was improved. Using the ROS spin trap, DMPO, electron paramagnetic resonance (EPR) spectroscopy demonstrated a significant decrease in ROS in Tg hearts during the first 20 min of reperfusion. This decrease in ROS was accompanied by an increase in NO production determined by EPR using the NO spin trap, Fe-MGD. Attenuated ROS in ecSOD Tg myocytes was also supported by decreased production of peroxynitrite (ONOO(-)). Increased NO bioavailability was confirmed by attenuated guanylate cyclase-dependent (p-VASP) signaling. In conclusion, attenuation of ROS levels by cardiac-specific ecSOD overexpression increases NO bioavailability in response to ischemia/reperfusion and protects against reperfusion injury. These findings are the first to demonstrate increased NO bioavailability with attenuation of ROS by direct measurement of these reactive species (EPR, reactive fluorescent dyes) with cardiac-specific ecSOD expression. This is also the first indication that the predominantly extracellular SOD isoform is capable of cytosolic localization that affects myocardial intracellular signal transduction and function.

Elucidating effects of environmental exposure using human-induced pluripotent stem cell disease modeling.

Induced pluripotent stem cells (iPSCs) are a powerful modeling system for medical discovery and translational research. To date, most studies have focused on the potential for iPSCs for regenerative medicine, drug discovery, and disease modeling. However, iPSCs are also a powerful modeling system to investigate the effects of environmental exposure on the cardiovascular system. With the emergence of e-cigarettes, air pollution, marijuana use, opioids, and microplastics as novel cardiovascular risk factors, iPSCs have the potential for elucidating the effects of these toxins on the body using conventional two-dimensional (2D) arrays and more advanced tissue engineering approaches with organoid and other three-dimensional (3D) models. The effects of these environmental factors may be enhanced by genetic polymorphisms that make some individuals more susceptible to the effects of toxins. iPSC disease modeling may reveal important gene-environment interactions that exacerbate cardiovascular disease and predispose some individuals to adverse outcomes. Thus, iPSCs and gene-editing techniques could play a pivotal role in elucidating the mechanisms of gene-environment interactions and understanding individual variability in susceptibility to environmental effects.

Integrated Multilayer Omics Reveals the Genomic, Proteomic, and Metabolic Influences of Histidyl Dipeptides on the Heart.

Background Histidyl dipeptides such as carnosine are present in a micromolar to millimolar range in mammalian hearts. These dipeptides facilitate glycolysis by proton buffering. They form conjugates with reactive aldehydes, such as acrolein, and attenuate myocardial ischemia-reperfusion injury. Although these dipeptides exhibit multifunctional properties, a composite understanding of their role in the myocardium is lacking. Methods and Results To identify histidyl dipeptide-mediated responses in the heart, we used an integrated triomics approach, which involved genome-wide RNA sequencing, global proteomics, and unbiased metabolomics to identify the effects of cardiospecific transgenic overexpression of the carnosine synthesizing enzyme, carnosine synthase (Carns), in mice. Our result showed that higher myocardial levels of histidyl dipeptides were associated with extensive changes in the levels of several microRNAs, which target the expression of contractile proteins, ß-fatty acid oxidation, and citric acid cycle (TCA) enzymes. Global proteomic analysis showed enrichment in the expression of contractile proteins, enzymes of ß-fatty acid oxidation, and the TCA in the Carns transgenic heart. Under aerobic conditions, the Carns transgenic hearts had lower levels of short- and long-chain fatty acids as well as the TCA intermediate-succinic acid; whereas, under ischemic conditions, the accumulation of fatty acids and TCA intermediates was significantly attenuated. Integration of multiple data sets suggested that ß-fatty acid oxidation and TCA pathways exhibit correlative changes in the Carns transgenic hearts at all 3 levels. Conclusions Taken together, these findings reveal a central role of histidyl dipeptides in coordinated regulation of myocardial structure, function, and energetics.

The effect of aminophylline on loss of consciousness, bispectral index, propofol requirement, and minimum alveolar concentration of desflurane in volunteers.

BACKGROUND: Adenosine is a soporific neuromodulator; aminophylline, which is clinically used as a bronchodilator, antagonizes the action of adenosine in the central nervous system. Thus, we tested the hypothesis that aminophylline delays loss of consciousness (LOC) and speeds recovery of consciousness (ROC) with propofol anesthesia, and that aminophylline increases the minimum alveolar concentration (MAC) of desflurane. METHODS: In this double-blind crossover study, volunteers were randomized to either aminophylline or saline on different days. Aminophylline 6 mg/kg was given IV, followed by 1.5 mg x kg(-1) x h(-1) throughout the study day. After 1 h of aminophylline or saline administration, propofol 200 mg was given at a rate of 20 mg/min. The bispectral index was continuously monitored, as were times to LOC and ROC. After recovery from propofol, general anesthesia was induced with sevoflurane and subsequently maintained with desflurane. The Dixon "up-and-down" method was used to determine MAC in each volunteer after repeated tetanic electrical stimulation. RESULTS: Eight volunteers completed both study days. Time to LOC was prolonged by aminophylline compared with saline (mean +/- SD) (7.7 +/- 2.03 min vs 5.1 +/- 0.75 s, respectively, P = 0.011). The total propofol dose at LOC was larger with aminophylline (2.2 +/- 0.9 vs 1.4 +/- 0.4 mg/kg, P = 0.01), and the time to ROC was shorter (6.18 +/- 3.96 vs 12.2 +/- 4.73 min, P = 0.035). The minimum bispectral index was greater with aminophylline (51 +/- 15 vs 38 +/- 9, P = 0.034). There was no difference in MAC. CONCLUSION: Aminophylline decreases the sedative effects of propofol but does not affect MAC of desflurane as determined by tetanic electrical stimulation.

Induced pluripotent stem cells as a platform to understand patient-specific responses to opioids and anaesthetics.

Recent advances in human induced pluripotent stem cell (iPSC) technology may provide unprecedented opportunities to study patient-specific responses to anaesthetics and opioids. In this review, we will (1) examine the advantages and limitations of iPSC technology, (2) summarize studies using iPSCs that have contributed to our current understanding of anaesthetics and opioid action on the cardiovascular system and central nervous system (CNS), and (3) describe how iPSC technology can be used to further develop personalized analgesic and sedative pharmacotherapies with reduced or minimal detrimental cardiovascular effects.

Cardiospecific Overexpression of ATPGD1 (Carnosine Synthase) Increases Histidine Dipeptide Levels and Prevents Myocardial Ischemia Reperfusion Injury.

BACKGROUND Myocardial ischemia reperfusion (I/R) injury is associated with complex pathophysiological changes characterized by pH imbalance, the accumulation of lipid peroxidation products acrolein and 4-hydroxy trans-2-nonenal, and the depletion of ATP levels. Cardioprotective interventions, designed to address individual mediators of I/R injury, have shown limited efficacy. The recently identified enzyme ATPGD1 (Carnosine Synthase), which synthesizes histidyl dipeptides such as carnosine, has the potential to counteract multiple effectors of I/R injury by buffering intracellular pH and quenching lipid peroxidation products and may protect against I/R injury. METHODS AND RESULTS We report here that ß-alanine and carnosine feeding enhanced myocardial carnosine levels and protected the heart against I/R injury. Cardiospecific overexpression of ATPGD1 increased myocardial histidyl dipeptides levels and protected the heart from I/R injury. Isolated cardiac myocytes from ATPGD1-transgenic hearts were protected against hypoxia reoxygenation injury. The overexpression of ATPGD1 prevented the accumulation of acrolein and 4-hydroxy trans-2-nonenal-protein adducts in ischemic hearts and delayed acrolein or 4-hydroxy trans-2-nonenal-induced hypercontracture in isolated cardiac myocytes. Changes in the levels of ATP, high-energy phosphates, intracellular pH, and glycolysis during low-flow ischemia in the wild-type mice hearts were attenuated in the ATPGD1-transgenic hearts. Two natural dipeptide analogs (anserine and balenine) that can either quench aldehydes or buffer intracellular pH, but not both, failed to protect against I/R injury. CONCLUSIONS Either exogenous administration or enhanced endogenous formation of histidyl dipeptides prevents I/R injury by attenuating changes in intracellular pH and preventing the accumulation of lipid peroxidation derived aldehydes.

Cardiac myocyte-specific expression of inducible nitric oxide synthase protects against ischemia/reperfusion injury by preventing mitochondrial permeability transition.

BACKGROUND: Inducible nitric oxide synthase (iNOS) is an obligatory mediator of the late phase of ischemic preconditioning, but the mechanisms of its cardioprotective actions are unknown. In addition, it remains unclear whether sustained elevation of iNOS in myocytes provides chronic protection against ischemia/reperfusion injury. METHODS AND RESULTS: Constitutive overexpression of iNOS in transgenic mice (alpha-myosin heavy chain promoter) did not induce contractile dysfunction and did not affect mitochondrial respiration or biogenesis, but it profoundly decreased infarct size in mice subjected to 30 minutes of coronary occlusion and 24 hours of reperfusion. In comparison with wild-type hearts, isolated iNOS-transgenic hearts subjected to ischemia for 30 minutes followed by 40 minutes of reperfusion displayed better contractile recovery, smaller infarct size, and less mitochondrial entrapment of 2-deoxy-[(3)H]-glucose. Reperfusion-induced loss of NAD(+) and mitochondrial release of cytochrome c were attenuated in iNOS-transgenic hearts, indicating reduced mitochondrial permeability transition. The NO donor NOC-22 prevented permeability transition in isolated mitochondria, and mitochondrial permeability transition-induced NAD(+) loss was decreased in wild-type but not iNOS-null mice treated with the NO donor diethylene triamine/NO 24 hours before ischemia and reperfusion ex vivo. iNOS-mediated cardioprotection was not abolished by atractyloside. Reperfusion-induced production of oxygen-derived free radicals (measured by electron paramagnetic resonance spectroscopy) was attenuated in iNOS-transgenic hearts and was increased in wild-type hearts treated with the mitochondrial permeability transition inhibitor cyclosporin A. CONCLUSIONS: Cardiomyocyte-restricted expression of iNOS provides sustained cardioprotection. This cardioprotection is associated with a decrease in reperfusion-induced oxygen radicals and inhibition of mitochondrial swelling and permeability transition.

Red Cell Storage Duration Does Not Affect Outcome after Massive Blood Transfusion in Trauma and Nontrauma Patients: A Retrospective Analysis of 305 Patients.

BACKGROUND: Prolonged storage of packed red blood cells (PRBCs) may increase morbidity and mortality, and patients having massive transfusion might be especially susceptible. We therefore tested the hypothesis that prolonged storage increases mortality in patients receiving massive transfusion after trauma or nontrauma surgery. Secondarily, we considered the extent to which storage effects differ for trauma and nontrauma surgery. METHODS: We considered surgical patients given more than 10 units of PRBC within 24 hours and evaluated the relationship between mean PRBC storage duration and in-hospital mortality using multivariable logistic regression. Potential nonlinearities in the relationship were assessed via restricted cubic splines. The secondary hypothesis was evaluated by considering whether there was an interaction between the type of surgery (trauma versus nontrauma) and the effect of storage duration on outcomes. RESULTS: 305 patients were given a total of 8,046 units of PRBCs, with duration ranging from 8 to 36 days (mean ± SD: 22 ± 6 days). The odds ratio [95% confidence interval (CI)] for in-hospital mortality corresponding to a one-day in mean PRBC storage duration was 0.99 (0.95, 1.03, P = 0.77). The relationship did not differ for trauma and nontrauma patients (P = 0.75). Results were similar after adjusting for multiple potential confounders. CONCLUSIONS: Mortality after massive blood transfusion was no worse in patients transfused with PRBC stored for long periods. Trauma and nontrauma patients did not differ in their susceptibility to prolonged PRBC storage.

Effects of halothane, sevoflurane and desflurane on the force-frequency relation in the dog heart in vivo.

PURPOSE: Frequency potentiation is the increase in force of contraction induced by an increased heart rate (HR). This positive staircase phenomenon has been attributed to changes in Ca2+ entry and loading of intracellular Ca2+ stores. Volatile anesthetics interfere with Ca2+ homeostasis of cardiomyocytes. We hypothesized that frequency potentiation is altered by volatile anesthetics and investigated the influence of halothane (H), sevoflurane (S) and desflurane (D) on the positive staircase phenomenon in dogsin vivo. METHODS: Dogs were chronically instrumented for measurement of left ventricular (LV) pressure and cardiac output. Heart rate was increased by atrial pacing from 120 to 220 beats·min-1 and the LV maximal rate of pressure increase (dP/ dtmax) was determined as an index of myocardial performance. Measurements were performed in conscious dogs and during anesthesia with 1.0 minimal alveolar concentrations of each of the three inhaled anesthetics. RESULTS: Increasing HR from 120 to 220 beats·min-1 increased dP/dtmax from 3394 ± 786 (mean ± SD) to 3798 ± 810 mmHg sec-1 in conscious dogs. All anesthetics reduced dP/dtmax during baseline (at 120 beatss·min-1: H, 1745 ± 340 mmHgs·sec-1; S, 1882 ± 418; D, 1928 ± 454, allP < 0.05vs awake) but did not influence the frequency potentiation of dP/dtmax (at 220 beatss·min-1: H, 1981 ± 587 mmHgs·sec-1; S, 2187 ± 787; D, 2307 ± 691). The slope of the regression line correlating dP/dtmax and HR was not different between awake and anesetized dogs. Increasing HR did not influence cardiac output in awake or anesthetized dogs. CONCLUSION: These results indicate that volatile anesthetics do not alter the force-frequency relation in dogs in vivo.

The noble gas xenon induces pharmacological preconditioning in the rat heart in vivo via induction of PKC-epsilon and p38 MAPK.

Xenon is an anesthetic with minimal hemodynamic side effects, making it an ideal agent for cardiocompromised patients. We investigated if xenon induces pharmacological preconditioning (PC) of the rat heart and elucidated the underlying molecular mechanisms. For infarct size measurements, anesthetized rats were subjected to 25 min of coronary artery occlusion followed by 120 min of reperfusion. Rats received either the anesthetic gas xenon, the volatile anesthetic isoflurane or as positive control ischemic preconditioning (IPC) during three 5-min periods before 25-min ischemia. Control animals remained untreated for 45 min. To investigate the involvement of protein kinase C (PKC) and p38 mitogen-activated protein kinase (MAPK), rats were pretreated with the PKC inhibitor calphostin C (0.1 mg kg(-1)) or the p38 MAPK inhibitor SB203580 (1 mg kg(-1)). Additional hearts were excised for Western blot and immunohistochemistry. Infarct size was reduced from 50.9+/-16.7% in controls to 28.1+/-10.3% in xenon, 28.6+/-9.9% in isoflurane and to 28.5+/-5.4% in IPC hearts. Both, calphostin C and SB203580, abolished the observed cardioprotection after xenon and isoflurane administration but not after IPC. Immunofluorescence staining and Western blot assay revealed an increased phosphorylation and translocation of PKC-epsilon in xenon treated hearts. This effect could be blocked by calphostin C but not by SB203580. Moreover, the phosphorylation of p38 MAPK was induced by xenon and this effect was blocked by calphostin C. In summary, we demonstrate that xenon induces cardioprotection by PC and that activation of PKC-epsilon and its downstream target p38 MAPK are central molecular mechanisms involved. Thus, the results of the present study may contribute to elucidate the beneficial cardioprotective effects of this anesthetic gas.