Anesthesiology
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In order to determine whether or not irritation of the nasal passage with commonly used volatile anesthetics can elicit airway reflexes, we investigated respiratory, laryngeal, and tracheal responses to nasal insufflation of three volatile anesthetics (enflurane, isoflurane, and halothane) in 13 patients anesthetized with flunitrazepam, pentazocine, and nitrous oxide. The trachea of each patient was intubated with a saline-filled double-cuffed endotracheal tube. Changes in breathing pattern were measured with a pneumotachograph while changes in laryngeal wall tension and tracheal wall tension were assessed by measuring changes in the proximal cuff pressure and the distal cuff pressure, respectively. ⋯ In these patients, nasal insufflation of 1 and 3% of each anesthetic did not produce any reflex response, whereas reflex responses were evident during nasal insufflation of 5% enflurane, isoflurane, and halothane. In all 13 patients, nasal insufflation of all three anesthetics at a concentration of 5% invariably produced changes in breathing pattern characterized by prolongation of expiratory time (TE). However, prolongation of TE was the most pronounced for enflurane (from a control value of 2.1 +/- 0.5 to a maximum value of 4.8 +/- 2.2 s [mean +/- standard deviation]), less for isoflurane (from 2.2 +/- 0.5 to 3.9 +/- 1.7 s), and the least for halothane (from 2.2 +/- 0.6 to 2.9 +/- 0.9 s).(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
The automated interview versus the personal interview. Do patient responses to preoperative health questions differ?
Laboratory testing of presurgical patients has been shown to be excessive, thereby increasing costs, reducing resources for other health care uses, and increasing risks to both patients and physicians. As one step toward reducing the number of unnecessary preoperative tests ordered, we used an automated method to aid preoperative assessment of 239 patients in Chicago and in Winnipeg. The "HealthQuiz," a small hand-held device containing a computer chip and video screen, uses a decision tree to ask a minimum of 60 health-related questions (the patient's response to certain questions determines the number of questions presented). ⋯ Patient's answers to the HealthQuiz were compared with their responses to a randomly selected set of the same questions in a personal interview. Ninety-seven percent of the response pairs were identical, and most of the 3% that differed involved changes from "not sure" replies to the HealthQuiz. Laboratory tests suggested by responses to the two methods of questioning did not differ.(ABSTRACT TRUNCATED AT 250 WORDS)
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The alpha 2-adrenergic agonist medetomidine produces systemic hemodynamic effects that are mediated by both peripheral and central nervous system actions. The current investigation was designed to characterize coronary and systemic hemodynamic effects of the D- and L-stereoisomers of medetomidine in conscious, chronically instrumented dogs with and without autonomic nervous system blockade. Dogs were instrumented for measurement of aortic pressure, coronary blood flow velocity, cardiac output, left ventricular pressure, rate of change in pressure (dP/dt), and subendocardial systolic shortening. ⋯ In dogs pretreated with hexamethonium (20 mg/kg), propranolol (2 mg/kg), and atropine methylnitrate (3 mg/kg) to produce autonomic nervous system blockade, D-medetomidine also produced an initial pressor response, but no secondary reduction in heart rate or arterial pressure occurred. The results indicate that the D-isomer of medetomidine is stereospecific for alterations in hemodynamics: the active D-isomer produces decreases in heart rate, arterial pressure, and the rate-pressure product via diminished sympathetic and/or augmented parasympathetic tone. This conclusion is supported by the absence of these changes after pharmacologic blockade of the autonomic nervous system.
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Perioperative administration of the alpha 2 agonist clonidine has been shown to increase plasma alfentanil concentrations; however, the mechanism for this pharmacokinetic drug interaction is unknown. Because alfentanil undergoes extensive hepatic biotransformation, clonidine inhibition of alfentanil metabolism may alter alfentanil disposition. The first purpose of this investigation was to test the hypothesis that clonidine impairs human liver alfentanil metabolism. ⋯ Preincubation of D-medetomidine with microsomes did not enhance the inhibition of alfentanil metabolism. These results suggest that the increased alfentanil plasma concentrations and potentiation of alfentanil anesthesia associated with clonidine do not result from clonidine inhibition of alfentanil metabolism. D-medetomidine impairment of alfentanil metabolism, however,if present at therapeutic concentrations, may influence alfentanil disposition.(ABSTRACT TRUNCATED AT 250 WORDS)
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No reliable, quantifiable index of tissue perfusion is currently available to assess the efforts of coronary artery bypass graft (CABG) surgery. We used two-dimensional transesophageal contrast echocardiography with sonicated Renografin-76 microbubbles to determine the distribution of myocardial blood flow during coronary artery bypass graft surgery in 15 patients. Sonicated Renografin-76 contrast agent was injected into the aortic root of all patients after institution of cardiopulmonary bypass and application of the aortic occlusive clamp. ⋯ When predicted myocardial perfusion patterns, based on preoperative evaluation of epicardial vessel distribution derived from coronary angiography, were compared to actual perfusion patterns assessed with intraoperative echocardiography, contrast regional myocardial perfusion patterns were predicted 84% of the time (71-97%, 95% confidence limit). Regional myocardial perfusion deficits detected after coronary bypass grafting were associated with regional wall motion abnormalities detected after separation from cardiopulmonary bypass. Our technique makes possible on-line visualization of changes in regional blood flow in the heart before, during, and after CABG.(ABSTRACT TRUNCATED AT 250 WORDS)