Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2000
Clinical TrialHigh frequency jet ventilation in interventional fiberoptic bronchoscopy.
High frequency jet ventilation (HFJV) is a well accepted method for securing ventilation in rigid and interventional bronchoscopy. We describe a technique of HFJV using a 14F nylon insufflation catheter placed in the trachea to support stent implantation or endobronchial balloon dilation in endobronchial stenoses with the flexible fiberscope. One hundred sixty-one cases were treated with either a metal wire stent (n = 105) or with balloon dilation (n = 56). In addition to HFJV, IV anesthesia was applied in 132 cases. Driving pressure was 1125-1275 mm Hg, frequency 80-100/min, and inspiratory:expiratory ratio of 1:2. Fraction of inspired oxygen ranged from 0.3-1.0. The effects on alveolar ventilation were assessed by using blood-gas analysis and continuous monitoring of transcutaneous oxygen and carbon dioxide tension (P(tc)CO(2)). Complications consisted of hypertension (n = 8), hypotension (n = 6), bronchospasm (n = 5), and hypoxia (n = 6). In 52% of the cases, mild hypercarbia (P(tc)CO2 50-60mm Hg) was observed. In two cases, a P(tc)CO(2) > 80 mm Hg resolved spontaneously when the patients returned to normal breathing after intermittent superimposed ventilation with a face mask. During placement of stents in the proximal trachea, the jet catheter had to be withdrawn, resulting in displacement of the catheter into the pharynx in one case, which was managed safely with the bronchoscope. In conclusion, HFJV achieves satisfactory operating conditions and provides adequate gas exchange for interventional bronchoscopic procedures with the fiberscope. ⋯ Safe ventilation is desired when performing tracheobronchial stent implantation and balloon dilation with the fiberscope. High frequency jet ventilation, applied with a 14F insufflation catheter through the nasotracheal route, offers safe ventilatory support with minimal complications. This was evaluated in 161 procedures treating benign and malignant airway stenoses.
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Anesthesia and analgesia · Jun 2000
Clinical TrialEchocardiographic and pathological evaluation of atherosclerosis in the ascending aorta during coronary artery bypass grafting.
We performed intraoperative echocardiography with an epiaortic probe to assess the correlation between echocardiographic appearance and pathological findings of the aorta and to examine the effect of cross-clamping on the aortic wall in 276 patients who underwent coronary artery bypass grafting. The ascending aorta was divided into three segments as follows: lower (L), upper (U), and innominate. The anterior (ant) and posterior (post) intimal thicknesses of each of the three segments were measured. The echogenicity at each of the six locations was examined and was classified as isoechoic or nonisoechoic (hyperechoic, hypoechoic, or mixed type). Tissue punched from the ant L wall of the ascending aorta for vein anastomosis was examined for the presence of atheroma. At the ant L, the prevalence of atheroma was significantly higher in nonisoechoic walls than in isoechoic walls (P = 0.049). We divided patients into two groups according to echogenicity at the U segments. Group A (n = 213) consisted of patients whose echogenicities at both ant U and post U were isoechoic. Group B (n = 63) consisted of patients with nonisoechoic echogenicity at ant U and/or post U. The intimal thicknesses at all six locations in Group B patients were greater than those of Group A (P < 0.01). Deformities at the clamp site after cardiopulmonary bypass were observed significantly more often in Group B than in Group A (P < 0.01). Our data suggest that a nonisoechoic aortic wall indicates more advanced atheroma and a higher risk of deformities at the clamp site. Examination of the echogenicity of the ascending aorta may be one method to reduce perioperative neurological complications. ⋯ We performed epiaortic echocardiography during coronary artery bypass grafting and found that the presence of atheroma and deformities at the cross-clamping site were significantly more prevalent in nonisoechoic walls than isoechoic walls.
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Anesthesia and analgesia · Jun 2000
Comparative StudyA comparison of the electrocardiographic cardiotoxic effects of racemic bupivacaine, levobupivacaine, and ropivacaine in anesthetized swine.
We sought, in this observer-blinded study, to determine the lethal dose for each of the local anesthetics levobupivacaine (L), racemic bupivacaine (B), and ropivacaine (R), and to compare their respective effects on the QRS interval of the precordial electrocardiograph after intracoronary injection. Anesthetized swine were instrumented with a left anterior descending artery coronary angiography catheter and injected with increasing doses of L, B, or R according to a randomized protocol. The doses administered were 0. 375, 0.75, 1.5, 3.0, and 4.0 mg, with further doses increasing in 1-mg increments until death occurred. Plotting the mean maximum QRS interval as a function of the log(10) mmol dose allowed the following cardiotoxicity potency ratios to be determined for a doubling of QRS duration-B:L:R = 2.1:1.4:1. The lethal doses in millimoles (median/range) for L and R were (0.028/0.024-0.031) and (0.032/0.013-0.032), respectively, and were significantly higher than for B (0.015/0.012-0.019) - (P < 0.05, n = 7 for all groups). The lethal dose did not differ between R and L. Thus, the cardiotoxicity potency ratios for the three anesthetics based on lethal dose were: 2.1:1.2:1. If the anesthetic potencies for B and L are similar, the latter should have less potential for cardiotoxicity in the clinical situation. ⋯ Animal experiments have shown levobupivacaine and ropivacaine to be less cardiotoxic than racemic bupivacaine. This in vivo study, using a validated swine model, compared the relative direct cardiotoxicities of these three local anesthetics. The lethal dose did not differ between levobupivacaine and ropivacaine, but was lowest for racemic bupivacaine.
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Anesthesia and analgesia · Jun 2000
Absorbents differ enormously in their capacity to produce compound A and carbon monoxide.
Concern persists regarding the production of carbon monoxide (CO) and Compound A from the action of carbon dioxide (CO(2)) absorbents on desflurane and sevoflurane, respectively. We tested the capacity of eight different absorbents with various base compositions to produce CO and Compound A. We delivered desflurane through desiccated absorbents, and sevoflurane through desiccated and moist absorbents, then measured the resulting concentrations of CO from the former and Compound A from the latter. We also tested the CO(2) absorbing capacity of each absorbent by using a model anesthetic system. We found that the presence of potassium hydroxide (KOH) and sodium hydroxide (NaOH) increased the production of CO from calcium hydroxide (Ca[OH](2)) but did not consistently affect production of Compound A. However, the effect of KOH versus NaOH was not consistent in its impact on CO production. Furthermore, the effect of KOH versus NaOH versus Ca(OH)(2) was inconsistent in its impact on Compound A production. Two absorbents (Amsorb) [Armstrong Medica, Ltd, Coleraine, Northern Ireland], composed of Ca(OH)(2) plus 0.7% polyvinylpyrrolidine, calcium chloride, and calcium sulfate; and lithium hydroxide) produced dramatically lower concentrations of both CO and Compound A. Both produced minimal to no CO and only small concentrations of Compound A. The presence of polyvinylpyrrolidine, calcium chloride, and calcium sulfate in Amsorb appears to have suppressed the production of toxic products. All absorbents had an adequate CO(2) absorbing capacity greatest with lithium hydroxide. ⋯ Production of the toxic substances, carbon monoxide and Compound A, from anesthetic degradation by carbon dioxide absorbents, might be minimized by the use of one of two specific absorbents, Amsorb (Armstrong Medica, Ltd., Coleraine, Northern Ireland) (calcium hydroxide which also includes 0.7% polyvinylpyrrolidine, calcium chloride, and calcium sulfate) or lithium hydroxide.