1. The effect of sodium influx on anoxic damage was investigated in rat hippocampal slices.Previous experiments demonstrated that a concentration of tetrodotoxin which blocks neuronal transmission protects against anoxic damage. In this study we examined low concentrations of lidocaine (lignocaine; which do not block neuronal transmission), for their effect on recovery of the evoked population spike recorded from the CAl pyramidal cell layer. 2. Recovery of the population spike, measured 60 min after a 5 min anoxic period, was 4 + 2% of its preanoxic, predrug level. Lidocaine concentrations of 10, 50, and 100 /M significantly improved recovery to 56 + 12, 80 + 7 and 70 + 14 %, respectively. 3. Lidocaine (10 /M) did not alter the size of the evoked response before anoxia and had no significant effect on potassium levels or calcium influx during anoxia. It did, however, reduce cellular sodium levels (146 + 7 vs. 202 + 12 nmol mg-) and preserve ATP levels (2-17 + 0 07 vs. 1-78 + 0 07 nmol mg-1) during anoxia. All values were measured at the end of 5 min of anoxia except those for Ca2+ influx which were measured during 10 min of anoxia. 4. High concentrations of lidocaine (100 /M) did not improve recovery significantly over that observed with 10 jtM. They also had no significantly greater effects on sodium levels than 10/SM lidocaine (137 ± 12 vs. 146 + 7 nmol mg-); however, 100 /M lidocaine significantly improved potassium (202 + 18 vs. 145 + 6 nmol mg-1) and ATP (2-57 + 0-06 vs. 2-17 + 0 07 nmol mg-') levels, while reducing calcium influx (7-76 + 0-12 vs. 9X24 + 0 39 nmol mg-1 (10 min)-1) when compared with 10 /M lidocaine. 5. We conclude that sodium influx and ATP depletion are of major importance in anoxic damage since 10 uM lidocaine reduced these changes during anoxia and improved recovery of the population spike. In addition, our results indicate that the properties of the sodium channel are altered during anoxia, since sodium influx is blocked by a concentration of lidocaine that does not affect the population spike in the preanoxic period.Reduced oxygen delivery to the brain can lead to permanent loss of brain function (Hansen, 1985;Siesjo, 1988). It is important to understand the mechanism of this damage if one is to protect neurons. Studies have implicated calcium
The results show that the SP checklist scores and the SP ratings of interpersonal and communication skills have comparable psychometric properties. The reliabilities of the five-item rating form (.76) and the single global rating of patient satisfaction (.70) were slightly higher than the reliability of the 17-item checklist (.65); this finding is of particular significance, given the greater length of the checklist. Also, the checklist scores and ratings appear to be measuring the same underlying dimension, with correlations of the checklist with the five ratings and with the single global rating being .82 and .81, respectively. Van der Vleuten and associates, in two excellent articles, noted a recent shift away from the use of subjective measures of clinical competence, such as rating scales, toward the use of presumably more objective measures, such as SP checklists. Their concern was that these objective measures may focus on somewhat trivial and easily measured aspects of the clinical encounter, and that more subtle but critical factors in clinical performance may be overlooked or ignored. They referred to such measurement as "objectified" rather than objective. The shift is based on the presumption that objective or objectified measurement is superior to subjective measurement, such as ratings, with respect to psychometric properties such as reliability. On the basis of a survey of several studies, though, the authors concluded that "objectified methods do not inherently provide more reliable scores" and "may even provide unwanted outcomes, such as negative effects on study behavior and triviality of the content being measured." The results of the present study support this conclusion, showing somewhat higher reliabilities for subjective ratings than for the objective (or perhaps objectified) checklist. Also, the high uncorrected correlations suggest that the more reliable ratings are measuring the same underlying dimension as are the checklist scores. The present study also illustrates the application of a recently proposed method for constructing a valid SP checklist, which would consist of items that best reflect global ratings of performance. In this study, the ratings were provided by the SPs themselves, but ratings could be obtained from faculty-physician experts who observe student performance on the SP case. Thus, performance on individual checklist items would be correlated with expert ratings, to identify the items that best predict the ratings. The checklist, then, would be constructed of just those items that best predict the ratings, and the checklist could be used for future testing without the need for further faculty ratings (yet the checklist scores would reflect the faculty ratings). With this approach, it would seem possible to construct checklists for history-taking and physical-examination skills, as well as for interpersonal and communication skills. Thus, the faculty ratings would provide a basis for case development and refinement, including scoring and standard setting, and scores o...
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