非線形解析による局所麻酔注射時の生体反応に関する研究

Abstract

Cardiovascular changes based on real or imaged pain or stress often result from dental treatment. These alterations currently are measured in linear fashion. The new theory of nonlinear dynamic systems predicts that complex physiological systems do not respond in a linear fashion, but may fluctuate, even in short time periods. To test the applicability of this theory to accept dental anesthesia procedures, blood flow waves and volume pulse waves were tested under varing condition of stress. Volunteers were randomly segregated into three groups : One group was tested for emotional stress by suggestion of impending infiltration anesthesia ; at a later time this group was tested for mental stress imposed by a mathematical task. The curves obtained by these two conditions were converted by computer numerical values using the software for nonlinear dynamic analysis (Microsoft Corp.). The second group was tested for emotional responses resulting from anticipation of injection, and from the actual injection itself (1/80, 000 epinephrin containing 2% lidocaine). The third group was tested in the same fashion as the second group, except that they also received an i.v. injection of midazolam five minutes before the start of the testing. The curves obtained from the second and third groups also were converted to numerical values by the aforementioned computer program. The results are summarized as follows : 1. Mental stress imposed by the mathematical task intensifies chaos. 2. Emotional stress by the suggestion of impending local anesthesia intensifies chaos, but is qualitively different from mental stress elicited by the mathematical task. 3. Physical responses to fear and anxiety before injection are more intense than during injection per se. 4. The Lyapunov exponent of blood flow waves reflects emotional stress elicited by suggestion of impending local anesthesia ; the Lyapunov exponent of volume pulse wave reflects physical responses to infiltration anesthesia accompanied by intravenous sedation. 5. Emotional stress of local anesthesia, combined with intravenous sedation produces less chaos than when sedation is omitted as shown by a decline in the Lyapunov exponent. 6. Physical responses without emotional stress result from the purely physical stimulation of infiltration anesthesia without emotional stress. 7. The attractor of mental and physical stress of infiltration anesthesia shows characteristics of confused shape, reduction and disorder toward normal condition.