Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2006
The differential effects of halothane and isoflurane on windup of dorsal horn neurons selected in unanesthetized decerebrated rats.
Halothane and isoflurane, in the peri-minimum alveolar anesthetic concentration (MAC) range, exert differential effects on spinal nociceptive neurons, whereby halothane further depresses their responses from 0.8 to 1.2 MAC, whereas isoflurane does not. We presently investigated if these anesthetics differentially affect windup, the progressive increase in neuronal responses to repetitive noxious stimuli, over a broad concentration range from 0 to 1.2 MAC. In decerebrated rats, single-unit recordings were made from dorsal horn neurons exhibiting windup to 20 1-Hz C-fiber strength electrical stimuli. ⋯ The dose-dependent suppression of windup is consistent with reduced temporal summation of pain. Further depression at 1.2 MAC halothane, but not isoflurane, suggests different sites of immobilizing action for these two anesthetics. Immobility seems to not be mediated by severe anesthetic depression of a subpopulation of nociceptive neurons.
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Anesthesia and analgesia · Sep 2006
Transcutaneous blood gas CO2 monitoring of induced ventilatory depression in mice.
We assessed a simple, noninvasive method of monitoring transcutaneous partial pressure of CO2 (Ptcco2) in mice to determine whether it would provide an accurate and reproducible method to assess ventilatory depression in mice. To this end, Ptcco2 and Paco2 (partial pressure of arterial CO2) measurements were performed on isoflurane-anesthetized male C57Bl/6 mice breathing differing percentages of CO2 or fentanyl, a known ventilatory depressive drug. All doses of fentanyl produced a sharp increase in Ptcco2 values within 20 min with difference in Ptcco2 values between saline and all fentanyl groups being statistically significant (P < 0.0001). ⋯ A Bland-Altman analysis likewise found that Ptcco2 measurements in the mice reliably and accurately reflected their Paco2 values. Therefore, under controlled conditions, Ptcco2 measurements were found to reliably reflect Paco2 values in mice. Consequently, the Ptcco2 method can be used as a means to rapidly and quantitatively assess the ventilatory depressive properties of a wide spectrum of drugs, under varying conditions in numerous mouse models.
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Anesthesia and analgesia · Sep 2006
Tetracaine at a small concentration delayed nerve growth without destroying neurites and growth cones.
Local anesthetics have direct neurotoxicity and induce growth cone collapse when applied to neurons at large concentrations. However, the effects of prolonged exposure to local anesthetics at a small concentration have never been studied. We examined whether neurite growth was slowed by tetracaine at small concentrations in chick embryo dorsal root ganglions. ⋯ Filopodia of growth cones retracted, and their number was significantly decreased 24 and 48 h after the application of 10 and 20 microM of tetracaine. The quantity of actin in cell bodies increased, contrary to the effect on neurites and growth cones, where actin decreased 48 h after the application of 5, 10, and 20 microM of tetracaine. In conclusion, continuous exposure to tetracaine at small concentrations delayed neurite growth, reduced the number of filopodia, and decreased actin content.
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Anesthesia and analgesia · Sep 2006
Randomized Controlled TrialHypercapnia improves tissue oxygenation in morbidly obese surgical patients.
Risk of wound infection is increased in morbidly obese surgical patients, in part because a major determinant of wound infection risk, tissue oxygenation, is marginal. Unlike in lean patients, supplemental inspired oxygen (Fio2) only slightly improves tissue oxygenation in obese patients. Mild hypercapnia improves tissue oxygenation in lean patients but has not been evaluated in obese patients. ⋯ Demographic characteristics, cardiovascular measurements, and Pao2 (222 +/- 48 versus 230 +/- 68 mm Hg in normocapnic versus hypercapnic; mean +/- sd; P = 0.705) were comparable in the groups. Tissue oxygen tension, however, was greater in hypercapnic than in normocapnic patients (78 +/- 31 versus 56 +/- 13 mm Hg; P = 0.029). Mild hypercapnia increased tissue oxygenation by an amount believed to be clinically important and could potentially reduce the risk of surgical wound infection in morbidly obese patients.
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Anesthesia and analgesia · Sep 2006
The National Practitioner Data Bank and anesthesia malpractice payments.
A publicly available SPSS database was obtained at the National Practitioner Data Bank website (www.npdb-hipdb.com). After analysis, we found that between 1991 and 2004, there were 276,274 medical malpractice-related payments in the United States. ⋯ Also, the median anesthesia malpractice payments, adjusted to 2005 dollars, increased significantly from 1991 to 1994 and 2001 to 2004 (69,330 dollars versus 205,222 dollars). We conclude that over the past 14 yr, whereas the number of anesthesia malpractice payments has decreased, the median payment of cases has increased.