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
Case ReportsProjected complex sensations after interscalene brachial plexus block.
The development of projected complex sensations mimicking phantom pain after interscalene block is reported. The recognition of this entity is important because it may be confused with some other cardiac, esophageal, or visceral pathologies.
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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
Induction of anesthesia and insertion of a laryngeal mask airway in the prone position for minor surgery.
The use of the prone position for surgery presents potential obstacles to rapid tracking of patients during ambulatory anesthesia. We describe a prospective audit of 73 patients who placed themselves in the prone position; anesthesia was induced in this position and a laryngeal mask airway (LMA) was used to maintain the airway. Additional increments of propofol were given to one patient who had laryngospasm and to nine who required deepening of anesthesia before the LMA could be inserted. Of four cases with LMA malpositioning, the LMA was adjusted easily in three, but in one patient who was edentulous, it was necessary to hold the LMA for the duration of the procedure. Manual ventilation of the lungs via the LMA was required because of arterial oxygen desaturation and hypoventilation in four patients. Blood was noted outside the nostrils in two patients, presumably caused by soft tissue trauma after insertion of the LMA, and bradycardia occurred in five patients. In the postoperative period, hoarseness and sore throat were observed in one and six patients, respectively. With experience and appropriate patient selection, it is possible to induce and maintain anesthesia using a LMA in patients in the prone position for ambulatory surgery. ⋯ With experience and appropriate patient selection, it is possible to induce and maintain anesthesia using a laryngeal mask airway in patients in the prone position for ambulatory surgery.
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Anesthesia and analgesia · May 2002
The neuropathologic effects in rats and neurometabolic effects in humans of large-dose remifentanil.
Given in clinically relevant large doses to rats, mu-opioids produce limbic system hypermetabolism and histopathology. This investigation extends these observations, in both rats and humans, for the short-acting drug remifentanil, which allows more precise control and assessment of the effects of duration of opioid exposure. We performed two series of experiments: one in rats for neuropathologic effects and the second in humans for neurometabolic effects. Fifty mechanically ventilated rats received saline solution or remifentanil 20-160 microg x kg(-1) x min(-1) for 3 h, followed by neuropathologic evaluation 7 days later. Four volunteers underwent induction of anesthesia and endotracheal intubation with propofol and rocuronium administration followed by remifentanil infusion at 1-3 microg x kg(-1) x min(-1) with positron emission tomography evaluation of cerebral metabolic rate for glucose. In rats, dose-related electroencephalogram activation was evident and 19 of 40 remifentanil-treated rats showed brain damage, primarily in the limbic system (P < 0.01). In humans, cerebral metabolic rate for glucose in the temporal lobe increased from 6.29 +/- 0.32 to 7.68 +/- 1.05 mg x 100 g(-1) x min(-1) (P < 0.05). These data indicate that prolonged large-dose remifentanil infusion is neurotoxic in rats with congruent metabolic effects with brief infusion in humans and suggest that some adverse effects reported in rats may be clinically relevant. ⋯ This study demonstrates dose-related remifentanil neurotoxicity in physiologically controlled rats with congruent brain metabolic effects in four humans undergoing positron emission tomography evaluation during brief large-dose remifentanil anesthesia. These data suggest that some adverse effects reported in rats may be clinically relevant.