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October 16-20, 2010 San Diego, CA Home Abstract Archive Search Abstracts 2010 Session Grid 2010 Meeting Website Policy Statements ASA Website Feedback 
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A-1332
2003 |
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| Epidural Needle Angles Selected by Clinicians in an Epidural Simulator | ||||||||||||
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W. Bosseau Murray, MB, ChB, Brian A. Minarcik, B.S. Simulation Development and Cognitive Science Laboratory, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States. |
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Background: Residents learning epidural insertion techniques are taught to make small changes in angle adjustments when readjusting the needle angle after encountering "bone" or "os." The effect on needle tip position resulting from changing the angle of insertion of any needle is difficult to conceptualize during training. Furthermore, the angle selected will have a greater effect on the resulting position of the needle point at a greater depth. While residents can verbalize the concept, they often do not apply the concept during clinical practice. We were interested in determining: - to what extent physicians with varying levels of education implemented the concept of angle changes on needle tip position, and - to what extent clinicians adjusted the needle angle in simulated thin and less thin patients. Method: We constructed an epidural simulator with an adjustable distance from skin to maximal depth. We used material with thicknesses of 2.5 cm and 5.5 cm simulating thin and less thin patients respectively. After obtaining institutional (IRB) approval, physicians (n=15) inserted an epidural needle into the simulator at an angle they would typically use in clinical settings. The angle was measured as the "initial angle of insertion." Participants were informed that they had encountered a solid obstruction ("bone" or "os") and asked to adjust the needle tip as they would in clinical practice. We measured the subsequent "corrected angle" that resulted after adjustment of the epidural needle path used. We calculated the difference between the initial angle and the corrected angle of insertion for each participant. For the whole group, we calculated the averages of a.) the initial angles of insertion, b.) the adjusted angles, and c.) the differences between the initial and corrected angles for the group of participants. (see Table 1) Results: There was no correlation between the level of education (CA1, CA2, or CA3), the initial angle of insertion (74.8±7.8) (average ± standard deviation), or the corrected angle of insertion. The difference between the initial angle of insertion and the corrected angle of insertion was 5.6±3.5° in the 2.5 cm tissue and 5.2±4.5° in the 5.5 cm tissue. The angle differences in thick and thin models were not statistically significantly different (p>0.1) Discussion: After encountering an obstruction (bone), the angle change required to reach the target in an epidural procedure is dependent on the depth of tissue. This is a basic mathematical concept. The clinical experience of volunteers had little or no effect on the initial angle of insertion nor the angle adjustments, suggesting that application of knowledge of this phenomenon is not implemented in a simulator. The angle change required to reach the target area should be less for thicker tissue. The current lack of implementation of angle effects on the position of the needle tip necessitates more emphasis on training health practitioners with hands-on models to understand three-dimensional (3-D) concepts of needle insertion during epidural procedures. Anesthesiology 2003; 99: A1332 |
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