Anesthesiology
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Randomized Controlled Trial Clinical Trial
Herpes labialis in parturients receiving epidural morphine following cesarean section.
A significant association exists between the use of epidural morphine (EM), reactivation of herpes labialis (HL) commonly known as coldsores, and pruritus in the obstetric population. A randomized prospective study was designed to eliminate previously identified confounding variables. Immediately following delivery, parturients having undergone cesarean section with epidural anesthesia with carbonated lidocaine (Xylocaine CO2, Astra, Mississauga, Ontario, Canada) with 1:200,000 epinephrine were sequentially randomized to receive either EM or im opioids for postoperative analgesia. ⋯ The incidence of oral viral shedding was low. Surgical stress, the local anesthetic solution, and epinephrine addition to the local anesthetic were eliminated as confounders. Stepwise logistic regression analysis revealed that EM and a history of herpes labialis in these patients were predictive for reactivating oral HSV.
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A combined pharmacokinetic and pharmacodynamic model of methohexital was used to establish and evaluate feedback control of methohexital delivery during total intravenous anesthesia with fentanyl in 11 surgical patients. The median frequency of the EEG power spectrum served as the pharmacodynamic variable constituting feedback. Based on previous investigations a median frequency from 2-3 Hz was chosen as the desired EEG set point. ⋯ The decrease of median EEG frequency to 2-3 Hz was primarily induced by an increase in fractional power in the 0.5-2- Hz frequency band to 46 +/- 4%. The average requirement of methohexital during the first 2 h was 675 +/- 250 mg. The authors conclude that model-based feedback control of intravenous methohexital delivery can help establish and quantitate methohexital requirements during total intravenous anesthesia with fentanyl.
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The authors examined the American Society of Anesthesiologists Closed Claims Study database to define the role of nerve damage in the overall spectrum of anesthesia-related injury that leads to litigation. Of 1,541 claims reviewed, 227 (15%) were for anesthesia-related nerve injury. Ulnar neuropathy represented one-third of all nerve injuries and was the most frequent nerve injury. ⋯ The closed claims reviewers judged that the standard of care had been met significantly more often in claims involving nerve damage than in claims not involving nerve damage. The authors conclude that nerve damage is a significant source of anesthesia-related claims but that the exact mechanism of nerve injury is often unclear. In particular, ulnar nerve injuries seemed to occur without identifiable mechanism.
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Use of pharmacokinetic concepts to predict anesthetic drug concentrations has not had extensive use in clinical anesthetic practice to date. The multiple exponent equations needed to describe iv drug disposition have required computer capability not practical for the operating room. An algorithm is presented that allows the clinician to use information from the pharmacokinetic literature to improve accuracy of drug dosing in the operating room. Implemented on a pocket calculator, this approach does not involve complex mathematics or lengthy computations and allows the clinician to obtain a continuous prediction of the plasma anesthetic concentration during the course of the anesthetic from iv bolus or continuous infusion of anesthetic drugs.
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The electrical current thresholds for pain (ECTP) in the skin of the neck and tail were measured in rats with chronically implanted lumbar subarachnoid catheters. The effects of a benzodiazepine antagonist and a gamma-aminobutyric acid (GABA) antagonist on the analgesic effects of equivalent doses of midazolam, fentanyl, and ketocyclazocine were studied. These were the minimum doses producing maximal segmental analgesia when given intrathecally (i.e., they all caused a significant and maximum increase in ECTP in the tail, which was similar for all three drugs, but no significant change in the ECTP in the neck). ⋯ Segmental analgesia following midazolam was also significantly attenuated (P less than 0.05) when the selective GABA antagonist bicuculline was given intrathecally at the same time as midazolam. The highest dose of bicuculline used (50 pmol) caused no significant attenuation of the segmental analgesic effects of either ketocyclazocine or fentanyl. The authors concluded that the segmental analgesia produced by intrathecal midazolam is mediated by the benzodiazepine-GABA receptor complex that is involved in other benzodiazepine actions.