Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2006
Comparative StudyEtomidate depresses lumbar dorsal horn neuronal responses to noxious thermal stimulation in rats.
Etomidate is a widely used IV anesthetic, but little is known about its analgesic properties, in particular, its effects on spinal cord neuronal responses to noxious stimuli. We hypothesized that etomidate would depress lumbar neuronal responses to noxious heat. Rats (n = 15) were anesthetized with isoflurane (1.2%) and laminectomy was performed to record single unit activity. ⋯ The responses quickly recovered, usually by the 10-min period postinjection. Similar responses were obtained in decerebrate, isoflurane-free rats administered etomidate and in isoflurane-anesthetized rats administered propofol. These data demonstrate that etomidate depresses spinal cord neuronal responses to noxious stimulation and is a possible mechanism by which this drug might produce analgesia.
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Anesthesia and analgesia · Apr 2006
Case ReportsInfusion pump delivers over-dosage of propofol as a result of missing syringe support.
We describe the malfunction of a common drug infusion pump. The syringe saddle was missing and allowed the syringe barrel to contact the pump case, which decreased the outward displacement of the syringe clamp. Then, the infusion pump falsely detected a smaller syringe size and consequently delivered an increased infusion rate and overdose of propofol to the patient. More commonly, an incorrectly mounted syringe may increase the outward displacement of the syringe clamp so that the infusion pump falsely detects a larger syringe size, with resultant less than expected infusion rate.
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Anesthesia and analgesia · Apr 2006
Comparative StudyAnticholinesterase drugs stimulate smooth muscle contraction of the rat trachea through the Rho-kinase pathway.
We performed this study to determine the effects of Rho-kinase inhibitors, Y-27632 and fasudil, on the anticholinesterase (anti-ChE)-induced contractile and phosphatidylinositol responses of the rat trachea. In vitro measurements of isometric tension and [3H] inositol monophosphate (IP1) that was formed were conducted by using rat tracheal rings or slices. ⋯ Neostigmine-induced IP1 accumulation was attenuated by fasudil at 100 microM. The results suggest that anti-ChEs cause airway smooth muscle contraction, in part, through activation of the Rho-kinase pathway.
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Anesthesia and analgesia · Apr 2006
The delivery of drugs to patients by continuous intravenous infusion: modeling predicts potential dose fluctuations depending on flow rates and infusion system dead volume.
IV drug infusion has the potential for dosing errors, which arise from complex interactions between carrier flows and the infusion set dead volume. We computed the steady-state mass of drug stored in the infusion set dead volume, using phenylephrine as a model compound. The mass of drug in the dead volume increases with stock drug concentration and desired dose but decreases with carrier flow rate. ⋯ This time is longest for large stock-drug concentrations, larger dead volumes, and slower final carrier rates. These computations illustrate that (a) the dead volume may contain a large mass of drug available for inadvertent bolus, (b) cessation of carrier flow can profoundly reduce drug delivery, and (c) after a change in carrier flow or drug dosing, a significant lag is possible before drug delivery achieves steady state. Although computed for phenylephrine, the concepts are generic and valid for any drug administered by IV infusion.
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Anesthesia and analgesia · Apr 2006
Prediction of the effect of acute normovolemic hemodilution on the hematological constituents of sequestered autologous whole blood.
During acute normovolemic hemodilution (ANH), autologous whole blood is collected in a series of collection bags containing anticoagulant. The effect of hemodilution on the actual hematological constituents of this sequestered whole blood product has never been examined. We developed a mathematical model that predicts how whole blood bag constituents change during ANH to elucidate the theoretical basis for ANH efficacy. ⋯ The impact of ANH on autologous whole blood constituents may be accurately predicted using this model. Conversion of WB(ANH) into equivalent allogeneic blood products could provide a useful method of comparing outcome in various ANH studies. The exponential envelope may be used to assess the actual ANH technique performed by the anesthesiologist, which in turn may impact quality assurance standards.