Anesthesia and analgesia
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Anesthesia and analgesia · Feb 2009
Mortality within 2 years after surgery in relation to low intraoperative bispectral index values and preexisting malignant disease.
A correlation between deep anesthesia (defined as time with Bispectral Index (BIS) <45; T(BIS <45)) and death within 1 yr after surgery has previously been reported. In order to confirm or refute these findings, we evaluated T(BIS <45) as an independent risk factor for death within 1 and 2 yr after surgery and also the impact of malignancy, the predominant cause of death in the previous report. ⋯ Using a similar set of co-variates as in previous work, we confirmed the statistical relation between 1-yr mortality and T(BIS <45), and we extended this observation to 2-yr mortality. However, this relation is sensitive to the selection of co-variates in the statistical model, and a randomized study is required to demonstrate that there really is a causal impact from and T(BIS <45) on postoperative mortality and, if it does, the effect is probably very weak in comparison with co-morbidity as assessed by ASA physical score, the preexisting malignancy status at surgery and age.
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Anesthesia and analgesia · Feb 2009
A retrospective study of intraoperative awareness with methodological implications.
Awareness during general anesthesia is a problem receiving increased attention from physicians and patients. Large multicentered studies have established an accepted incidence of awareness during general anesthesia as approximately 1-2 per 1000 cases or 0.15%. More recent retrospective data, however, suggest that the actual incidence may be as low as 0.0068%. ⋯ Using a retrospective methodology, reports of intraoperative awareness are not statistically different in patients who received general anesthesia compared with those who did not. These results suggest that, despite success with other rare perioperative events, the resolution of retrospective database analyses may be too low to study intraoperative awareness.
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Anesthesia and analgesia · Feb 2009
Fentanyl added to propofol anesthesia elongates sinus node recovery time in pediatric patients with paroxysmal supraventricular tachycardia.
In some types of pediatric supraventricular tachycardia, reentrant mechanisms are sensitive to enhanced vagal tone. Propofol is a feasible anesthetic for pediatric electrophysiological study and radiofrequency catheter ablation. Although fentanyl and propofol infusions both enhance cardiac vagal tone, it is unclear whether the combination of propofol and fentanyl has a potential to enhance it. In this study, we evaluated the hypothesis that fentanyl combined with propofol could alter cardiac electrophysiological activities in pediatric patients undergoing electrophysiological study and radiofrequency catheter ablation. ⋯ Since an enhanced cardiac vagal tone is one of the causative factors for prolonged CSNRT, our findings greatly support the hypothesis that fentanyl combined with propofol has a potential to enhance cardiac vagal tone.
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Anesthesia and analgesia · Feb 2009
Anesthetics discriminate between tonic and phasic gamma-aminobutyric acid receptors on hippocampal CA1 neurons.
Anesthesia is produced by a depression of neuronal signaling in the central nervous system (CNS); however, the mechanism(s) of action underlying this depression remain unclear. Recent studies have indicated that anesthetics can enhance inhibition of CNS neurons by increasing current flow through tonic gamma-aminobutyric acid (GABA(A)) receptor gated chloride channels in their membranes. Enhanced tonic inhibition would contribute to CNS depression produced by anesthetics, but it remains to be determined to what extent anesthetic actions at these receptors contribute to CNS depression. In the present study, we compared and contrasted the involvement of tonic versus synaptic GABA(A) receptors in the functional depression of CNS neurons produced by isoflurane and thiopental. ⋯ These results indicate that general anesthetics discriminate between synaptic and tonic GABA(A) receptors. Effects on both phasic and tonic receptors combined to depress circuit responses produced by thiopental, whereas only effects on synaptic GABA receptors appeared to play an important role for isoflurane. Together with the other known sites of action for these two anesthetics, our results support a multisite, agent-specific mechanism for anesthetic actions.
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Anesthesia and analgesia · Feb 2009
Case ReportsBispectral index monitoring of a narcolepsy-cataplexy episode during regional anesthesia.
Narcolepsy or Gélineau syndrome is an extremely incapacitating chronic sleep disorder of unknown etiology that is characterized by uncontrollable attacks of deep sleep and is typically associated with cataplexy sudden loss of muscle tone. The Bispectral Index (BIS), an electroencephalographic-derived cerebral monitor, used for monitoring the effects of anesthetic/hypnotic drugs was shown to correlate to various conditions that could influence the eletroencephalogram. We assessed the utility of using BIS for monitoring a possible narcolepsy-cataplexy episode and whether a distinctive BIS profile might offer an early warning of an impending narcoleptic/cataplectic spell. ⋯ This was followed by a second "continuous low-vigilance" phase of BIS around 75 with low electromyographic activity, ending with a third "nonresponsive vigilance" phase of a full-blown narcolepsy-cataplexy episode of BIS around 45 with complete loss of muscle power. The purpose of presenting this report is to emphasize the fact that narcoleptic patients can still run the risk of loss of consciousness with atonia under regional anesthesia, and such an undesirable complication cannot be under-estimated. BIS monitoring is a simple method that could offer an early warning of an imminent episode, with its associated hazards, in patients with narcolepsy-cataplexy undergoing surgery under regional anesthesia.