Anesthesiology
-
Randomized Controlled Trial Clinical Trial
Low-dose clonidine and neostigmine prolong the duration of intrathecal bupivacaine-fentanyl for labor analgesia.
Intrathecal (IT) opioid and local anesthetic combinations are popular for labor analgesia because of rapid, effective pain relief, but the duration of analgesia is limited. This study was undertaken to determine whether the addition of clonidine and neostigmine to IT bupivacaine-fentanyl would increase the duration of analgesia without increasing side effects for patients in labor. ⋯ The addition of clonidine and neostigmine significantly increased the duration of analgesia from IT bupivacaine-fentanyl during labor, but neostigmine caused more nausea. Although serious side effects were not observed in this study, safety must be further addressed before the routine use of multiple IT drugs is advocated.
-
Subarachnoid hemorrhage can lead to cerebral ischemia and irreversible brain injury. The purpose of this study was to determine whether subarachnoid hemorrhage produces changes in brain tissue oxygen pressure, carbon dioxide pressure, or pH during surgery for cerebral aneurysm clipping. ⋯ These results show that subarachnoid hemorrhage can significantly decrease brain tissue oxygen pressure and pH related to the severity of the bleed. Increasing the desflurane concentration to 9% increased brain tissue oxygen pressure in all patients and brain tissue pH in patients with subarachnoid hemorrhage with baseline acidosis.
-
Dynamic intraesophageal pressure (Pes) is used to estimate intrapleural pressure (Ppl) to calculate lung compliance and resistance. This study investigated the nonhuman primate Ppl-Pes tissue barrier frequency response and the dynamic response requirements of Pes manometers. ⋯ In monkeys, the Ppl-Pes tissue barrier has a frequency response suitable for Ppl estimation during low-frequency mechanical ventilation, and Pes manometers should have a minimum uniform frequency response up to 8.5 Hz. However, the Ppl-Pes tissue barrier adversely affects the accurate estimation of dynamic Ppl at high frequencies, with varied airway pressure amplitudes and offsets, such as the Ppl encountered during high-frequency oscillatory ventilation.
-
The noble gas xenon (Xe) has been used as an inhalational anesthetic agent in clinical trials with little or no physiologic side effects. Like nitrous oxide, Xe is believed to exert minimal unwanted cardiovascular effects, and like nitrous oxide, the vapor concentration to achieve 1 minimum alveolar concentration (MAC) for Xe in humans is high, i.e., 70-80%. In the current study, concentrations of up to 80% Xe were examined for possible myocardial effects in isolated, erythrocyte-perfused guinea pig hearts and for possible effects on altering major cation currents in isolated guinea pig cardiomyocytes. ⋯ Unlike hydrocarbon-based gaseous anesthetics, Xe does not significantly alter any measured electrical, mechanical, or metabolic factors, or the nitric oxide-dependent flow response in isolated hearts, at least partly because Xe does not alter the major cation currents as shown here for cardiac myocytes. The authors' results indicate that Xe, at approximately 1 MAC for humans, has no physiologically important effects on the guinea pig heart.
-
The authors previously reported that secondary carnitine deficiency may sensitize the heart to bupivacaine-induced arrhythmias. In this study, the authors tested whether bupivacaine inhibits carnitine metabolism in cardiac mitochondria. ⋯ Bupivacaine inhibits mitochondrial state III respiration when acylcarnitines are the available substrate. The substrate specificity of this effect rules out bupivacaine inhibition of carnitine palmitoyl transferases I and II, carnitine acetyltransferase, and fatty acid beta-oxidation. The authors hypothesize that differential inhibition of carnitine-stimulated pyruvate oxidation by various local anesthetics supports the clinical relevance of inhibition of carnitine-acylcarnitine translocase by local anesthetics with a cardiotoxic profile.