Anesthesia and analgesia
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Anesthesia and analgesia · Apr 1996
Randomized Controlled Trial Clinical TrialThe onset of rocuronium, but not of vecuronium or mivacurium, is modified by tourniquet inflation.
A previous investigation showed that inflation of a tourniquet did not interrupt onset of vecuronium neuromuscular block. To test the hypothesis that this effect depended on potency, twitch tension was measured in an arm with a tourniquet inflated during onset and compared with a control arm in 30 patients under fentanyl-thiopental-nitrous oxide-isoflurane anesthesia. Patients were randomly allocated to receive either vecuronium 0.1 mg/kg (n = 10), rocuronium 0.6 mg/kg (n = 10), or mivacurium 0.2 mg/kg (n = 10). ⋯ The difference in maximum neuromuscular block between arms was 17% +/- 7%, 5% +/- 5%, and 0% +/- 2% in the rocuronium, vecuronium, and mivacurium groups (P < 0.05). To explain that onset of block continues in spite of interruption of blood flow, drug molecules must gain access to the neuromuscular junction via routes other than the circulation. The results of this investigation are consistent with the hypothesis that there is redistribution of drug from extrajunctional to junctional areas during onset of action of muscle relaxants and this process is more important for the more potent drugs (vecuronium and mivacurium) than for rocuronium.
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Anesthesia and analgesia · Apr 1996
Clinical Trial Controlled Clinical TrialMild intraoperative hypothermia reduces production of reactive oxygen intermediates by polymorphonuclear leukocytes.
Mild hypothermia directly impairs numerous immune functions in vitro. However, the in vivo effects of mild hypothermia on neutrophil phagocytosis and oxidative killing remain unknown. We tested the hypothesis that mild intraoperative hypothermia decreases neutrophil phagocytic capacity and generation of reactive oxygen intermediates (a measure of oxidative killing). ⋯ Production of oxidative intermediates was most closely related to intraoperative core temperature, decreasing nearly fourfold over a 4 degree C range. This in vitro temperature dependence was matched in vitro. Impaired neutrophil oxidative killing may contribute to the observed hypothermia-induced reduction in resistance to infection.
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Anesthesia and analgesia · Apr 1996
Factors affecting production of compound A from the interaction of sevoflurane with Baralyme and soda lime.
Various alkali (e.g., soda lime) convert sevoflurane to CF2=C(CF3)OCH2F, a vinyl ether called "Compound A, " whose toxicity raises concerns regarding the safe administration of sevoflurane via rebreathing circuits. In the present investigation, we measured the sevoflurane degradation and output of Compound A caused by standard (13% water) Baralyme brand absorbent and standard (15% water) soda lime, and Baralyme and soda lime having various water contents (including no water). We used a flow-through system, applying a gas flow rate relative to absorbent volume that roughly equaled the rate/volume found in clinical practice. ⋯ Both absorbents, especially when dry, also destroyed Compound A, the concentration exiting from absorbent resulting from a complex sum of production and destruction. We conclude that the variability of concentrations of Compound A found in clinical practice may be largely explained by the inflow rate used (i.e., by rebreathing), sevoflurane concentration, and absorbent temperature and dryness. The effect of dryness is complex, with fresh dry absorbent destroying Compound A as it is made, and with dry absorbent that has been exposed to sevoflurane for a period of time providing a sometimes unusually high output of Compound A.
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Anesthesia and analgesia · Apr 1996
Lidocaine inhibits blood coagulation: implications for epidural blood patch.
Lidocaine in the epidural space, through inhibitory effects upon coagulation, may contribute to inefficacy of epidural autologous blood patch (EBP). This study was undertaken to evaluate the effect of achievable epidural concentrations of lidocaine on blood coagulation as a step in testing this hypothesis. Ex vivo blood coagulation using whole blood (n = 20) was studied with computerized thrombelastography (TEG). ⋯ Statistical analysis using analysis of variance for repeated measures revealed that the three highest lidocaine concentrations tested caused hypocoagulable and/or fibrinolytic changes as compared with controls. Achievable epidural admixtures of lidocaine and whole blood will impair coagulation. Therefore, residual lidocaine in the epidural space may contribute to failures of immediate or early EBP.
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Anesthesia and analgesia · Apr 1996
The effects of propofol on hemodynamics and renal blood flow in healthy and in septic sheep, and combined with fentanyl in septic sheep.
Sepsis is characterized by myocardial depression and systemic vasodilation, both of which are most likely mediated by nitric oxide. Propofol inhibits nitric oxide synthase and may therefore be beneficial in sepsis. On the other hand, renal blood flow, known to be only minimally affected by propofol in healthy subjects, may be drastically reduced in septic individuals, because the renal microvasculature is known to be very sensitive to nitric oxide. ⋯ Renal blood flow was reduced to 60% +/- 10% of the preseptic baseline and to 39% +/- 4% of the septic value. This reduction was selective, since the cardiac output decreased significantly less. These adverse effects of propofol on hemodynamics and renal blood flow were reduced when propofol was combined with fentanyl.