Anesthesiology
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Comparative Study
Differential peripheral nerve block by local anesthetics in the cat.
Controversy still surrounds the differential susceptibility of nerve fibers to local anesthetic conduction block. In order to help resolve this controversy, we developed an in vivo model of peripheral nerve blockade in the cat that closely reproduced the clinical state. Using this model, differential rate of nerve blockade of A-alpha, A-delta, and C fibers by 2-chloroprocaine, lidocaine, bupivacaine, and etidocaine was observed and quantitated. ⋯ Etidocaine blocked A-delta fibers first. A-alpha fibers always were blocked last. Of the four local anesthetics tested, 2-chloroprocaine produced the greatest differential rate of block of the nerve fibers, and etidocaine produced the least.
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Adaptations of the critical-incident technique were used to gather reports of anesthesia-related human error and equipment failure. A total of 139 anesthesiologists, residents, and nurse-anesthetists from four hospitals participated as subjects in directed or open-ended interviews, and 48 of them functioned as "trained observers." A total of 1,089 descriptions of preventable "critical incidents" were collected. Of these, 70 represented errors or failures that had contributed in some way to a "substantive negative outcome." From these incidents, ten potential strategies were developed for prevention or detection of incidents. ⋯ Among the broad categories of key strategies for mishap prevention were additional technical training, improved supervision, improved organization, equipment human-factors improvements, and use of additional monitoring instrumentation. The data also suggest that less healthy patients are more likely to be affected adversely by errors. It is suggested that, in future studies of anesthesia mortality and morbidity, untoward events should be classified according to preventive strategy rather than outcome alone as an aid to those who wish to apply the experience of others to lessen the risk in their individual practice.
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Isolated rat sciatic nerves were used to study the interaction between 2-chloroprocaine (2-CP) and bupivacaine (BP). Five nerves studied as controls were treated with 5 X 10(-4) M BP and the amplitude of the compound action potential (CAP) evoked by suprathreshold stimulation was measured. This concentration of BP completely blocked nerve conduction; but, following washout with normal Krebs-Ringer solution, the CAP amplitude recovered to 50% of initial values in 50 (+/- 4) min with a rate of recovery of 1.7 (+/- 0.6) %/min. ⋯ When five nerves were exposed to a 5 X 10(-4) M solution of a 2-CP metabolite, 4-amino-2-chlorobenzoic acid, no nerve blockade was produced. When these nerves subsequently were blocked with BP, recovery to 50% of initial values occurred in 22 (+/- 5) min, with a rate of recovery of 2.0 (+/- 0.2) %/min. Although pretreatment with either 2-CP or 4-amino-2-chlorobenzoic acid significantly shortened the duration of BP-induced nerve blockade, neither drug had a significant effect on the rate of recovery once the CAP amplitude returned to measurable values.
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Six commercially available epidural catheters were tested in a special apparatus designed to simulate epidural catheter insertion and quantitatively measure the buckling strength of these catheters. The experimental apparatus utilized a modified Tuohy needle and a specially calibrated force transducer. Catheters were inserted through the Tuohy needle in a manner similar to that employed clinically, and the maximum forces developed against the surface of the force transducer were recorded electronically. ⋯ When comparing only new catheters without stylets, the buckling forces ranged from 201 to 285 g. All catheters, whether new or damaged showed an increase in the maximum buckling force with the use of the needle hub insert. The percentage increase in force (needle hub insert vs. no insert) ranged from a low of 23% to a maximum of 108%.(ABSTRACT TRUNCATED AT 250 WORDS)