Effect of low-dose atropine on heart rate fluctuations during orthostatic load: a spectral analysis.
Spectral analysis was utilized in order to determine the influence of low (0.7 microgram/kg)-dose atropine sulfate injections on the isolated spectral power components of heart rate fluctuations in contrast to moderate (0.02 mg/dose)-dose atropine and unmedicated states in human subjects during orthostatic load. Low-dose atropine decreased mean heart rate and increased respiration-related spectral power compared with controls in both the supine and standing posture. In supine subjects total power (0.01-0.5 Hz) was unchanged compared with controls due to a decreasing trend of low-frequency (0.01-0.05 Hz) and mid-frequency (0.05-0.15 Hz) heart rate spectral power. Standing upright, there was a distinct increase in total power with significantly higher values than in the controls resulting from an enormous activation of mid-frequency heart rate fluctuations. The peak frequency of the mid-frequency component was increased with a strong tendency compared with controls. Moderate-dose atropine increased mean heart rate and decreased total power, mid-frequency and respiration-related heart rate spectral power and peak frequency compared with controls in both positions. Our results suggest that low-dose atropine affects the interaction between sympathetic and parasympathetic limbs in the autonomic control of cardiac function in a complex manner producing a differentiated pattern of heart rate fluctuations dependent on the body posture. We suggest that low-dose atropine augments and moderate-dose atropine attenuates the vagal cardiac efferent activity in each position.
Department of Pathophysiology, Medical Academy, Magdeburg (G.D.R.).
F
F
Weise
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K
Baltrusch
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F
Heydenreich
D000328:Adult; D001285:Atropine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D008297:Male; D011187:Posture
D001285:Atropine