Effects of nitrosopropofol on mitochondrial energy-converting system

Perioperative Inflammation and Its Modulation by Anesthetics

Surgery and other invasive procedures, which are routinely performed during general anesthesia, may induce an inflammatory response in the patient. This inflammatory response is an inherent answer of the body to the intervention and can be both beneficial and potentially harmful. The immune system represents a unique evolutionary achievement equipping higher organisms with an effective defense mechanism against exogenous pathogens. However, not only bacteria might evoke an immune response but also other noninfectious stimuli like the surgical trauma or mechanical ventilation may induce an inflammatory response of varying degree. In these cases, the immune system activation is not always beneficial for the patients and might carry the risk of concomitant, harmful effects on host cells, tissues, or even whole organ systems. Research over the past decades has contributed substantial information in which ways surgical patients may be affected by inflammatory reactions. Modulations of the patient's immune system may be evoked by the use of anesthetic agents, the nature of surgical trauma and the use of any supportive therapy during the perioperative period. The effects on the patient may be manifold, including various proinflammatory effects. This review focuses on the causes and effects of inflammation in the perioperative period. In addition, we also highlight possible approaches by which inflammation in the perioperative may be modulated in the future.

Critical illness and flat batteries

An exaggerated, dysregulated host response to insults such as infection (i.e. sepsis), trauma and ischaemia-reperfusion injury can result in multiple organ dysfunction and death. While the focus of research in this area has largely centred on inflammation and immunity, a crucial missing link is the precise identification of mechanisms at the organ level that cause this physiological-biochemical failure. Any hypothesis must reconcile this functional organ failure with minimal signs of cell death, availability of oxygen, and (often) minimal early local inflammatory cell infiltrate. These failed organs also retain the capacity to usually recover, even those that are poorly regenerative. A metabolic-bioenergetic shutdown, akin to hibernation or aestivation, is the most plausible explanation currently advanced. This shutdown appears driven by a perfect storm of compromised mitochondrial oxidative phosphorylation related to inhibition by excessive inflammatory mediators, direct oxidant stress, a tissue oxygen deficit in the unresuscitated phase, altered hormonal drive, and downregulation of genes encoding mitochondrial proteins. In addition, the efficiency of oxidative phosphorylation may be affected by a substrate shift towards fat metabolism and increased uncoupling. A lack of sufficient ATP provision to fuel normal metabolic processes will drive downregulation of metabolism, and thus cellular functionality. In turn, a decrease in metabolism will provide negative feedback to the mitochondrion, inducing a bioenergetic shutdown. Arguably, these processes may offer protection against a prolonged inflammatory hit by sparing the cell from initiation of death pathways, thereby explaining the lack of significant morphological change. A narrow line may exist between adaptation and maladaptation. This places a considerable challenge on any therapeutic modulation to provide benefit rather than harm.

Posterior spinal instrumented fusion for idiopathic scoliosis in patients with multisystemic neurodegenerative disorder: a report of two cases

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS) syndrome is a progressive multisystemic neurodegenerative disorder. MELAS syndrome impairs oxidative phosphorylation and predisposes patients to lactic acidosis, particularly under metabolic stress. We report 2 siblings with MELAS-associated idiopathic scoliosis who underwent posterior spinal instrumented fusion with measures taken to minimise anaesthetic and surgical stress, blood loss, and operating time.

Effect of remifentanil on mitochondrial oxygen consumption of cultured human hepatocytes

During sepsis, liver dysfunction is common, and failure of mitochondria to effectively couple oxygen consumption with energy production has been described. In addition to sepsis, pharmacological agents used to treat septic patients may contribute to mitochondrial dysfunction. This study addressed the hypothesis that remifentanil interacts with hepatic mitochondrial oxygen consumption. The human hepatoma cell line HepG2 and their isolated mitochondria were exposed to remifentanil, with or without further exposure to tumor necrosis factor-α (TNF-α). Mitochondrial oxygen consumption was measured by high-resolution respirometry, Caspase-3 protein levels by Western blotting, and cytokine levels by ELISA. Inhibitory κBα (IκBα) phosphorylation, measurement of the cellular ATP content and mitochondrial membrane potential in intact cells were analysed using commercial ELISA kits. Maximal cellular respiration increased after one hour of incubation with remifentanil, and phosphorylation of IκBα occurred, denoting stimulation of nuclear factor κB (NF-κB). The effect on cellular respiration was not present at 2, 4, 8 or 16 hours of incubation. Remifentanil increased the isolated mitochondrial respiratory control ratio of complex-I-dependent respiration without interfering with maximal respiration. Preincubation with the opioid receptor antagonist naloxone prevented a remifentanil-induced increase in cellular respiration. Remifentanil at 10× higher concentrations than therapeutic reduced mitochondrial membrane potential and ATP content without uncoupling oxygen consumption and basal respiration levels. TNF-α exposure reduced respiration of complex-I, -II and -IV, an effect which was prevented by prior remifentanil incubation. Furthermore, prior remifentanil incubation prevented TNF-α-induced IL-6 release of HepG2 cells, and attenuated fragmentation of pro-caspase-3 into cleaved active caspase 3 (an early marker of apoptosis). Our data suggest that remifentanil increases cellular respiration of human hepatocytes and prevents TNF-α-induced mitochondrial dysfunction. The results were not explained by uncoupling of mitochondrial respiration.

Evaluation of the Antioxidant Properties of Propofol and its Nitrosoderivative. Comparison with Homologue Substituted Phenols

Propofol (2,6-diisopropylphenol), some substituted phenols (2,6-dimethylphenol and 2,6-ditertbutylphenol) and their 4-nitrosoderivatives have been compared for their scavenging ability towards 1,1-diphenyl-2-picrylhydrazyl and for their inhibitory action on lipid peroxidation. These products were also compared to the classical antioxidants butylated hydroxytoluene and butylated hydroxyanisole. When measuring the reactivity of the various phenolic derivatives with 1,1-diphenyl-2-picrylhydrazyl the following order of effectiveness was observed: butylated hydroxyanisole > propofol > 2,6-dimethylphenol > 2,6-di-tertbutylphenol > butylated hydroxytoluene. In cumene hydroperoxide-dependent microsomal lipid peroxidation, propofol acts as the most effective antioxidant, while butylated hydroxyanisole, 2,6-di-tertbutylphenol and butylated hydroxytoluene exhibit a rather similar effect, although lower than propofol. In the iron/ascorbate-dependent lipid peroxidation propofol, at concentrations higher than 10 microM, exhibits antioxidant properties comparable to those of butylated hydroxytoluene and butylated hydroxyanisole, 2,6-Dimethylphenol is scarcely effective in both lipoperoxidative systems. The antioxidant properties of the various molecules depend on their hydrophobic characteristics and on the steric and electronic effects of their substituents. However, the introduction of the nitroso group in the 4-position almost completely removes the antioxidant properties of the examined compounds. The nitrosation of the aromatic ring of antioxidant molecules and the consequent loss of antioxidant capacity can be considered a condition potentially occurring in vivo since nitric oxide and its derivatives are continuously formed in biological systems.

[Mitochondria in anaesthesia and intensive care]

OBJECTIVE

Mitochondria play a key role in energy metabolism within the cell through the oxidative phosphorylation. They are also involved in many cellular processes like apoptosis, calcium signaling or reactive oxygen species production. The objectives of this review are to understand the interactions between mitochondrial metabolism and anaesthetics or different stress situations observed in ICU and to know the clinical implications.

DATA SOURCES

References were obtained from PubMed data bank (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) using the following keywords: mitochondria, anaesthesia, anaesthetics, sepsis, preconditioning, ischaemia, hypoxia.

DATA SYNTHESIS

Mitochondria act as a pharmacological target for the anaesthetic agents. The effects can be toxic like in the case of the local anaesthetics-induced myotoxicity. On the other hand, beneficial effects are observed in the anaesthetic-induced myocardial preconditioning. Mitochondrial metabolism could be disturbed in many critical situations (sepsis, chronic hypoxia, ischaemia-reperfusion injury). The study of the underlying mechanisms should allow to propose in the future new specific therapeutics.

Treating critical illness: the importance of first doing no harm

Singer and Glynne present evidence to suggest that the short- term benefits of many interventions for treating critical illness may camouflage an underlying tendency to cause harm.

Adverse Events Associated with Sedatives, Analgesics, and Other Drugs That Provide Patient Comfort in the Intensive Care Unit

Since the 2002 publication of multidisciplinary clinical practice guidelines for intensive care unit (ICU) sedation and analgesia, additional information regarding adverse drug events has been reported. Our understanding of the risks associated with these sedative and analgesic agents promises to improve outcomes by helping clinicians identify and respond to therapeutic misadventures sooner. This review focuses on many issues, including the potentially fatal consequences associated with the propofol infusion syndrome, the evolving understanding of propylene glycol intoxication associated with parenteral lorazepam, new data involving high-dose and long-term dexmedetomidine therapy, haloperidol- and methadone-related prolongation of QTc intervals on the electrocardiogram, adverse events associated with atypical antipsychotics, and the potential for nonsteroidal antiinflammatory drugs to interfere with bone healing.