Anesthesia and analgesia
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Anesthesia and analgesia · May 2002
Should we reevaluate the variables for predicting the difficult airway in anesthesiology?
Anesthesiologists have often been confronted with the difficult question of determining which patient will present an increased difficulty for endotracheal intubation. The limits of the previously reported morphometric airway measurements for predicting difficult intubation have inadequately addressed the normal patient population variables. We designed this prospective study to investigate the age and sex-related changes in the morphometric measurements of the airway in a large group of patients without anatomic abnormality and a group of cadavers. Hyomental, thyromental, sternomental distances, neck extension, and Mallampati scores were evaluated in 12 cadavers and in 334 patients. Patients were allocated to three groups based on age: Group 1 (20-30 yr), Group 2 (31-49 yr), and Group 3 (50-70 yr). Male and female sex differences were also evaluated. Hyomental distance was the only variable not affected by age. In addition, the mean population values were less than the threshold values suggested as criteria for difficult endotracheal intubation. All the other criteria were age-dependent and inversely affected by the increase in age. Male sex was also a distinction for increased measurements of all the morphometric distances. The mean degree of neck extension was similar in both sex groups. This study provides a more comprehensible approach to the morphometric measurements of the human airway. Adequate data of normal values may help the clinician to identify patients that are outside the range and therefore may be challenging. ⋯ This study was performed to establish data on the average values of airway morphology in the adult population of different age groups and sex. Hyomental, thyromental, sternomental distances and neck extension values were measured on 12 cadavers and 334 patients.
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Anesthesia and analgesia · May 2002
Vascular responsiveness to brachial artery infusions of phenylephrine during isoflurane and desflurane anesthesia.
Compared with equi-minimum alveolar anesthetic concentration (MAC) isoflurane, desflurane is associated with greater levels of sympathetic nerve activity in humans but similar reductions in blood pressure. To explore these divergent effects, we evaluated vascular alpha(1)-adrenoceptor responses in the human forearm during isoflurane and desflurane anesthesia to determine if alpha(1)-adrenoceptor responses were more substantially attenuated during desflurane administration. Bilateral forearm venous occlusion plethysmography was used to examine arterial blood flow and to determine changes in forearm vascular resistance during brachial artery infusions of saline and phenylephrine (0.2, 0.4, 0.8, and 1.6 microg/min) in 22 conscious subjects and during anesthesia with 0.65 and 1.3 MAC isoflurane or desflurane. Infusion of phenylephrine into the brachial artery increased the forearm vascular resistance in a dose-dependent manner. The arterial response to phenylephrine was significantly attenuated by 0.65 and 1.3 MAC desflurane and similarly attenuated during 1.3 MAC isoflurane (P < 0.05). Impaired arterial alpha(1)-adrenoceptor responsiveness occurred during desflurane. However, this effect was statistically similar (P > 0.05) to the impaired responses during isoflurane. Blood pressure decreases during volatile anesthesia may be, in part, caused by decreased alpha(1)-adrenoceptor responsiveness. ⋯ alpha-receptors on blood vessels regulate constriction and dilation and therefore modulate blood pressure. This research indicates that vasoconstriction via the alpha(1)-receptor vascular response is impaired during isoflurane and desflurane anesthesia.
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Anesthesia and analgesia · May 2002
Practice Guideline GuidelineACC/AHA Guideline Update for Perioperative Cardiovascular Evaluation for Noncardiac Surgery--Executive Summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery).
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Anesthesia and analgesia · May 2002
Pulmonary gas exchange in coronary artery surgery patients during sevoflurane and isoflurane anesthesia.
As the surgical population ages, the number of patients presenting with coronary artery disease and age-related loss of pulmonary recoil will increase. Although their influence on gas exchange in this population remains unknown, sevoflurane and isoflurane are used for an increasing variety of surgical procedures. We examined pulmonary gas exchange (multiple inert gas elimination technique) in 30 patients presenting for coronary artery bypass grafting. After a baseline measurement taken during midazolam anesthesia, patients were continued on sevoflurane (n = 10), isoflurane (n = 10), or midazolam (n = 10) for 20 min, then a second measurement was taken. During sevoflurane and isoflurane anesthesia, blood flow to lung areas with a low ventilation/perfusion ratio (Va/Q) was significantly increased in comparison with control. During sevoflurane anesthesia, blood flow to lung areas with a normal Va/Q ratio (76 +/- 12 versus control: 89 +/- 5, mean +/- SD) and PaO(2) (138 +/- 31 versus control: 156 +/- 35 mm Hg, mean +/- SD) were depressed, whereas an increase in Va/Q-dispersion (log SD(Q)) was observed during isoflurane anesthesia. We conclude that both sevoflurane and isoflurane alter the distribution of perfusion in the lung, but only sevoflurane significantly depresses PaO(2). ⋯ Both sevoflurane and isoflurane modified pulmonary blood flow in patients with coronary artery disease, but only sevoflurane depresses arterial oxygenation in this population.
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Anesthesia and analgesia · May 2002
The effects of age on neural blockade and hemodynamic changes after epidural anesthesia with ropivacaine.
We studied the influence of age on the neural blockade and hemodynamic changes after the epidural administration of ropivacaine 1.0% in patients undergoing orthopedic, urological, gynecological, or lower abdominal surgery. Fifty-four patients were enrolled in one of three age groups (Group 1: 18-40 yr; Group 2: 41-60 yr; Group 3: > or=61 yr). After a test dose of 3 mL of prilocaine 1.0% with epinephrine 5 microg/mL, 15 mL of ropivacaine 1.0% was administered epidurally. The level of analgesia and degree of motor blockade were assessed, and hemodynamic variables were recorded at standardized intervals. The upper level of analgesia differed among all groups (medians: Group 1: T8; Group 2: T6; Group 3: T4). Motor blockade was more intense in the oldest compared with the youngest age group. The incidence of bradycardia and hypotension and the maximal decrease in mean arterial blood pressure during the first hour after the epidural injection (median of Group 1: 11 mm Hg; Group 2: 16 mm Hg; Group 3: 29 mm Hg) were more frequent in the oldest age group. We conclude that age influences the clinical profile of ropivacaine 1.0%. The hemodynamic effects in older patients may be caused by the high thoracic spread of analgesia, although a diminished hemodynamic homeostasis may contribute. ⋯ Analgesia levels after the epidural administration of 15 mL of ropivacaine 1.0% increase with increasing age. This is associated with an increased incidence of hypotension in the elderly, although an effect of age on the hemodynamic homeostasis may have contributed. It appears that epidural doses should be adjusted for elderly patients.