Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1997
Randomized Controlled Trial Clinical TrialSimulation of an epidural test dose with intravenous isoproterenol in isoflurane-anesthetized adults.
Although a simulated intravenous (I.V.) test dose containing 3 microg isoproterenol results in a reliable heart rate (HR) increase in anesthetized patients, hypotension may limit its clinical utility. The present study was designed to determine the incidence of hypotension and the reliability of smaller doses of isoproterenol. Forty-five healthy adult patients were anesthetized with 1% end-tidal isoflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1-, 2-, and 3-microg groups (n = 15 each) received 3 mL of 1.5% lidocaine with 1, 2, and 3 microg isoproterenol I.V., respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. Mean maximal HR increases were 15 +/- 6, 23 +/- 10, and 32 +/- 7 bpm (mean +/- SD) in the isoproterenol 1-, 2-, and 3-microg groups, respectively. However, the incidence and degree of systolic hypotension were similar among groups. Isoproterenol 3 microg produced 100% sensitivity in both the conventional (> or = 20 bpm increase) and the modified (> or = 10 bpm increase) HR criteria, but 2 microg resulted in 100% sensitivity on the modified criterion alone. Isoproterenol 1 microg did not elicit reliable HR changes. Significant correlation was demonstrated between the isoproterenol dose (microg/kg) and the maximal HR increase. Ninety-five percent confidence intervals to increase HR by 10 and 20 bpm were 0.015-0.02 microg/kg and 0.03-0.04 microg/kg, respectively. The application of isoproterenol as a test dose component seems promising, pending detailed studies of neural toxicity. The appropriate dose needs to be tailored according to the patient's weight. ⋯ To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The author found that isoproterenol might be a useful drug in place of epinephrine.
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Anesthesia and analgesia · Sep 1997
Comparative StudyThe effect of priming with vecuronium and rocuronium on young and elderly patients.
The priming principle consists of administering a subparalyzing dose of nondepolarizing neuromuscular blocking drug 3-6 min before giving a second dose for tracheal intubation. This study was performed to observe the effects of priming doses of vecuronium and rocuronium on pulmonary function tests and muscular weaknesses in young (25-35 yr of age) and elderly (65-73 yr of age) patients. Ten young and 10 elderly patients were each placed in vecuronium and rocuronium groups. Oxygen saturation and train-of-four (TOF) ratio were determined, and pulmonary function tests were performed. Then 20% of the 95% effective dose (ED95) of the muscle relaxants was given intravenously. All tests were performed again 4 min after vecuronium and 3 min after rocuronium. Other signs of muscular weaknesses were also recorded. Elderly patients showed more signs of muscle weakness in both groups. The TOF ratio was 0.77 and 0.79 in the elderly rocuronium and vecuronium groups, respectively, and 0.89 and 0.90 in the young rocuronium and vecuronium groups, respectively. Dynamic spirometry revealed decreases in forced expiratory volume in 1 s and forced vital capacity in both groups, and no significant changes in peak expiratory flow rate. The expiratory reserve volume was reduced more in the elderly groups. Oxygen saturation decreased in both groups. We conclude that oxygen saturation, pulmonary function, and muscle strength decrease more in the elderly than in their younger counterparts from priming doses of vecuronium or rocuronium. ⋯ The priming principle consists of giving a subparalyzing dose of muscle relaxant 3-6 min before giving a second dose for tracheal intubation. We found that priming doses of vecuronium and rocuronium produced greater decreases in oxygen saturation and pulmonary function in the elderly (aged 65-73 yr) than their younger (aged 25-35 yr) counterparts. Priming may not be a safe approach in elderly patients.
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Anesthesia and analgesia · Sep 1997
The effect of GP683, an adenosine kinase inhibitor, on the desflurane anesthetic requirement in dogs.
The availability of an analgesic compound devoid of the side effects associated with the commonly used opioid and nonsteroidal antiinflammatory drugs would be useful during the perioperative period. Although adenosine has analgesic and anesthetic-sparing properties, it also produces dose-dependent cardiovascular depression. Inhibitors of adenosine kinase may be able to provide analgesia without producing acute cardiovascular or respiratory depression. This preliminary study investigated the effects of a novel adenosine kinase-inhibiting drug, GP683, on the minimum alveolar anesthetic concentration (MAC) of desflurane in dogs. Seven mongrel dogs were administered one of three different GP683 dose regimens (or the solvent) by intravenous infusion on separate occasions according to a cross-over study design. After determining the baseline desflurane MAC value, GP683 was infused at 75, 150, or 300 microg x kg(-1) x min(-1) for 5 min as a loading dose, followed by 15, 30, or 60 microg x kg(-1) x min(-1) for an additional 85 min to maintain a stable plasma drug level. The desflurane MAC was redetermined 30-90 min after starting the study drug or vehicle infusion, and 30-90 min and 120-180 min after termination of the infusion. Cardiovascular variables and plasma concentrations of GP683 were determined at specific intervals before, during, and after the MAC determinations. The three GP683 dose regimens produced 22%, 31%, and 50% decreases in the desflurane MAC, respectively. In addition, there was good correlation between the decrease in desflurane MAC and the plasma GP683 concentration (r = -0.78). Although the mean arterial pressure (MAP) was decreased up to 25% by the highest infusion rate of GP683, adjustments in the desflurane concentration to an equi-MAC value resulted in normalization of the MAP values. Furthermore, GP683 produced no changes in heart rate. In conclusion, the adenosine kinase-inhibiting drug, GP683, produced dose-dependent decreases in the desflurane MAC of dogs without producing untoward hemodynamic changes. ⋯ An investigational drug (GP683) that can increase the levels of an important endogenous substance in the body (adenosine) has been found to decrease the anesthetic requirement in dogs without producing adverse effects on the cardiovascular system.
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Anesthesia and analgesia · Sep 1997
Comparative StudyThe effects of sevoflurane on recovery of brain energy metabolism after cerebral ischemia in the rat: a comparison with isoflurane and halothane.
Isoflurane is an appropriate anesthetic for neuroanesthesia. We evaluated whether the effect of sevoflurane is similar to that of isoflurane or halothane on brain energy metabolism after cerebral ischemia followed by reperfusion using 31P-magnetic resonance spectroscopy. Wistar rats (n = 21) were divided into three groups: isoflurane-, sevoflurane-, or halothane-treated. After anesthesia induction and surgical preparation, each anesthetic concentration was adjusted to 1 minimum alveolar anesthetic concentration. Cerebral ischemia was induced with bilateral carotid occlusion and reduction of mean arterial blood pressure to 30-40 mm Hg by blood withdrawal. Magnetic resonance measurements were performed during ischemia and for 120 min of reperfusion. Intracellular pH in the isoflurane-treated, sevoflurane-treated, and halothane-treated groups decreased to 6.180 +/- 0.149, 6.125 +/- 0.134, and 6.027 +/- 0.157, respectively, at the end of ischemia. There were no differences in the change of phosphorous compounds and intracellular pH between the isoflurane-treated and the sevoflurane-treated groups during ischemia and reperfusion. However, in the halothane-treated group, we observed a significant delay in the recovery of adenosine triphosphate and intracellular pH (0.038 +/- 0.013 pH unit/min compared with 0.064 +/- 0.011 in the isoflurane-treated group and 0.058 +/- 0.008 in the sevoflurane-treated group) until 24 min of reperfusion (P < 0.05). We conclude that sevoflurane has effects similar to isoflurane on brain energy metabolism during and after cerebral ischemia. ⋯ It is important to know whether anesthetics adversely effect brain metabolism during ischemia and reperfusion. A new anesthetic, sevoflurane, affected the brain in a manner similar to isoflurane, which has been used for many years as an anesthetic.