Occurrence of a circadian rhythmicity for blood pressure in patients with circulatory shock.

Ten patients hemodynamically in shock were monitored for blood pressure along the 24-hr span while under antishock therapy. Time-qualified data were analyzed by means of the cosinor procedure. The fit of a 24-hr cosine function was able to reject the null hypothesis of amplitude = O in the majority of patients under intensive care. The blood pressure circadian rhythm was found to be independent of whether the patient was responsive or refractory to therapy. This phenomenon demonstrates that the maintenance of a blood pressure circadian rhythm is a characteristic intrinsic to hemodynamic shock even if blood pressure falls to very low values along the time scale.