Anesthesiology
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Randomized Controlled Trial Clinical Trial
The neuromuscular effects of ORG9426 in patients receiving balanced anesthesia.
In searching for a nondepolarizing muscle relaxant with intermediate duration but more rapid onset of action than the presently available compounds, the neuromuscular and circulatory effects of ORG9426 were investigated in two studies in humans receiving fentanyl, droperidol, thiopental, and nitrous oxide-oxygen anesthesia. Eighty patients, randomly assigned to one of four groups of 20 each, received 0.12, 0.16, 0.20, or 0.24 mg/kg ORG9426. In the first study, the doses (in milligrams per kilogram) of ORG9426 that caused 50% (ED50), 90% (ED90), or 95% (ED95) neuromuscular block were determined by the individual dose-response method; they were 0.170, 0.268, and 0.305 mg/kg, respectively. ⋯ After the administration of 0.6 mg/kg ORG9426, maximal neuromuscular block developed in 1.5 +/- 0.12 min in group 1 and in 1.2 +/- 0.14 min in group 2. Patients tracheas were intubated after development of the maximal neuromuscular effect of the intubating dose and after the recording of heart rate and systolic and diastolic blood pressure. There was no difference in the clinical duration of the intubating doses, which were 40.0 +/- 3.2 (15-73) min in group 1 and 39.3 +/- 2.4 (19-57) min in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Dose-response for atropine and heart rate in infants and children anesthetized with halothane and nitrous oxide.
The dose recommendations for atropine in anesthetized children vary, and the dose-response for heart rate has not been defined. We determined the dose-response for atropine and heart rate in 181 healthy children anesthetized with halothane and nitrous oxide. After induction of anesthesia, atropine in a dose of 5, 10, 20, 30, or 40 micrograms.kg-1 was administered by rapid intravenous infusion of each subject. ⋯ Subjects less than 6 months old had higher control and peak heart rates than did subjects greater than or equal to 2 yr old, but the older subjects had greater change in heart rate after atropine. For subjects greater than or equal to 2 yr old, all doses of atropine produced a significant increase in heart rate. The same was true for younger subjects, less than 6 months old, except that 5 micrograms.kg-1 did not increase heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Direct vasodilation by sevoflurane, isoflurane, and halothane alters coronary flow reserve in the isolated rat heart.
Direct vasodilation of coronary resistance vessels by anesthetics may reduce coronary flow reserve and interfere with myocardial flow-metabolism coupling. This study was performed to evaluate the potential for the halogenated anesthetic agents sevoflurane, isoflurane, and halothane to alter the regulation of coronary flow via a direct action on coronary resistance vessels. Coronary flow and flow reserve were measured in the quiescent isolated perfused rat heart at anesthetic concentrations between 0 and 3 x MAC. ⋯ At high concentrations (3.0 x MAC), coronary flow reserve was abolished by halothane and was decreased to near zero by isoflurane; however, flow reserve was reduced only 48% from control by sevoflurane. This difference among anesthetics is explained primarily by variations in the magnitude of direct coronary vasodilation produced by each anesthetic, rather than by effects on maximal vasodilator capacity. These data show that sevoflurane's intrinsic vasodilator action on coronary resistance vessels differs substantially from that of halothane and isoflurane.
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Knowledge of anesthetic effects on the automaticity of dominant and subsidiary cardiac pacemakers is fundamental to an understanding of mechanisms of arrhythmia during anesthesia, as well as to the management of patients with sinus node dysfunction or atrioventricular (AV) conduction block. Among potential pacemakers of the heart are subsidiary atrial pacemakers (SAP), which are located outside the classic sinoatrial (SA) node region but still within the right atrium. SAP have a higher inherent rate of automaticity than AV junctional pacemakers, may contribute to a multicentric atrial pacemaker complex, and can control the rhythm of the heart when the SA node is absent or inhibited. ⋯ Delivered concentrations of halothane of 1 or 2% corresponded to measured perfusate concentrations of 0.50 +/- 0.02 or 0.80 +/- 0.04 mM in experiments with E (n = 24) and 0.45 +/- 0.02 or 0.75 +/- 0.04 mM in experiments with NE (n = 54). E or NE perfusate concentrations were 1, 2, and 5 micrograms/l or 2, 5, and 10 micrograms/l, respectively. To determine the site of earliest activation (SEA), extracellular recordings were made from the SA node region and distal sites (approximately 1, 2, and 3 cm) along the sulcus terminalis, the previously reported locations of SAP.(ABSTRACT TRUNCATED AT 250 WORDS)