Anesthesiology
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The Edwards lung water computer system uses the thermal-dye indicator technique to estimate the lung extravascular fluid volume (EVLW). The authors tested the effect of changes in cardiac output (CO) on EVLW estimates made with the lung water computer in six dogs anesthetized with halothane. Baseline CO was 2.5 +/- 1.3 l/min (mean +/- SD); CO subsequently was increased either by 220% or decreased by 70% by either giving 0.5 mg/kg of isoproterenol or increasing the inspired halothane (1-4%), respectively. ⋯ At increased COs, estimated EVLW decreased. The authors conclude that the Edwards lung water computer overestimates lung water, possibly because the thermal indicator diffuses into nonpulmonary as well as pulmonary tissue. The overestimate is greatest at low cardiac outputs.
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Comparative Study
Facilitation of rapid endotracheal intubations with divided doses of nondepolarizing neuromuscular blocking drugs.
The authors sought to determine whether prior administration of a small, subparalyzing dose of nondepolarizing muscle relaxant would shorten the onset time of an intubating dose of muscle relaxant. Initially, in 60 anesthetized patients, twitch response of adductor pollicis to ulnar nerve stimulation was studied after a small dose of pancuronium 0.015 mg . kg-1, metocurine 0.03 mg . kg-1, or d-tubocurarine 0.04 mg . kg-1, followed 3 min later by pancuronium 0.08 mg . kg-1 or atracurium 0.4 mg . kg-1 administered iv. After 60 s, the minimum neuromuscular block, in all patients was 79.0 +/- 5.0%. ⋯ In 17% of the patients, after atracurium intubating conditions were fair. When nondepolarizing neuromuscular blocking drugs are administered in divided doses, neuromuscular blockade adequate for endotracheal intubation is achieved in less than 90 s. This facilitates rapid endotracheal intubation in a time comparable to using succinylcholine, without undesirable effects of the depolarizing neuromuscular blocking drugs.
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Twenty patients (23-76 yr) were studied with regard to lung tissue changes prior to and following induction of general anesthesia with muscular relaxation, and another four subjects were studied for a longer period awake. The transverse thoracic area and the structure of the lung tissue were determined by computerized tomography. No abnormalities in the lung tissue were noted before anesthesia. ⋯ The application of positive end-expiratory pressure of 10 cmH2O eliminated or reduced the densities. The four awake subjects showed no lung densities after 90 min in the supine position. It is suggested that these crest-shaped densities represent atelectases, which develop by compression of lung tissue rather than by resorption of gas.
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After Morton's demonstration in the Ether Dome of the Massachusetts General Hospital, anesthesia for surgery was accepted around the world at a speed unusually fast for any medical or scientific innovation. However, the concept of surgical anesthesia had been rejected on four occasions during the preceding 40 years. The rapid acceptance of anesthesia in 1846 appears to have had a political and social basis as well as medical. ⋯ First was a change in the perception of disease and pain; both lost religious connotations and became biologic phenomena as part of a process of secularization that affected all aspects of Western society. Second was the growth of a sense of well-being and progress, which imbued patients and physicians alike with confidence in their ability to control natural processes. During the last half century, pain has remained secular, but the confidence in both progress and the ability to control nature may have diminished.
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Following the administration of a single 0.1 mg/kg dose of vecuronium bromide, satisfactory conditions for tracheal intubation developed in 156 +/- 12 s (mean +/- SEM), and the clinical duration of the initial dose was 36 +/- 2 min. When the initial dose of vecuronium was administered in two increments, a 0.015 mg/kg "priming" dose, followed 6 min later by a 0.050 mg/kg "intubating" dose, intubation time decreased to 61 +/- 3 s and clinical duration to 21 +/- 1 min. ⋯ With the described technique, comparable intubating conditions could be obtained just as rapidly with vecuronium as with succinylcholine chloride, without subjecting the patients to the side effects of and the complications occasionally encountered with succinylcholine. An added advantage of the use of a priming dose is that it will reveal undiagnosed, pathologic, or idiopathic increase of sensitivity to nondepolarizing muscle relaxants.