Anesthesiology
-
Randomized Controlled Trial Multicenter Study Clinical Trial
Reduction of isoflurane minimal alveolar concentration by remifentanil.
Remifentanil is a new micro-specific opioid receptor agonist currently under investigation. The interaction between opioids and volatile anesthetics is complex. Defining this interaction provides a basis for more rational dosing schemes when such combinations are used for anesthesia and allows the anesthetic potency of remifentanil relative to other opioids to be determined. ⋯ The MAC reduction of isoflurane by remifentanil is similar to that produced by other opioids. Although remifentanil was given at extremely high concentrations in the absence of isoflurane, it did not provide adequate anesthesia. A 50% isoflurane MAC reduction is produced by 1.37 ng/ml remifentanil whole blood concentration compared to previously published plasma concentrations of fentanyl of 1.67 ng/ml or sufentanil of 0.14 ng/ml.
-
The nematode Caenorhabditis elegans offers many advantages as a model organism for studying volatile anesthetic actions. It has a simple, well-understood nervous system; it allows the researcher to do forward genetics; and its genome will soon be completely sequenced. C. elegans is immobilized by volatile anesthetics only at high concentrations and with an unusually slow time course. Here other behavioral dysfunctions are considered as anesthetic endpoints in C. elegans. ⋯ Volatile anesthetics selectively disrupt C. elegans behavior. The potency, time course, and recovery characteristics of halothane's effects on three behaviors are similar to its anesthetic properties in vertebrates. The affected nervous system molecules may express structural motifs similar to those on vertebrate anesthetic targets.
-
Clinical Trial Controlled Clinical Trial
Site(s) mediating sympathetic activation with desflurane.
Three strategies were employed to better define the afferent site(s) at which desflurane initiates its neurocirculatory activation. ⋯ There are sites in the upper airway (larynx and above) that respond with sympathetic activation during rapid increases in desflurane concentration independent of systemic anesthetic changes. These responses, while lesser than those seen with rapid increases to the lung, may represent direct irritation of airway mucosa. Heart rate and mean arterial pressure responses to desflurane can be initiated by selectively increasing concentrations to either right or left lung without altering systemic levels of desflurane. From this it is inferred that there are sites within the lungs, separate from systemic sites, that mediate this response. Neither systemic lidocaine nor attempted blockade of upper airway sites with cranial nerve blocks combined with topical lidocaine was effective in attenuating the neurocirculatory activation associated with desflurane.
-
Randomized Controlled Trial Clinical Trial
Effect of flumazenil on ventilatory drive during sedation with midazolam and alfentanil.
Patients who receive a combination of a benzodiazepine and an opioid for conscious sedation are at risk for developing respiratory depression. While flumazenil effectively antagonizes the respiratory depression associated with a benzodiazepine alone, its efficacy in the presence of both a benzodiazepine and an opioid has not been established. This study was designed to determine whether flumazenil can reverse benzodiazepine-induced depression of ventilatory drive in the presence of an opioid. ⋯ Flumazenil effectively reverses the benzodiazepine component of ventilatory depression during combined administration of a benzodiazepine and an opioid.
-
Randomized Controlled Trial Clinical Trial
Dose-response characteristics of spinal bupivacaine in volunteers. Clinical implications for ambulatory anesthesia.
Small doses of bupivacaine may be a reasonable choice for spinal anesthesia for patients having ambulatory surgery. However, few dose-response data are available to guide the selection of reasonable doses of bupivacaine for different ambulatory procedures. ⋯ These dose-response data may guide the selection of reasonable doses of bupivacaine for various outpatient procedures, although individual responses vary.