Differences among heart rate variability measures after anesthesia and cardiac surgery

Objective: To determine whether there are differences among measures of hea rt rate variability (HRV; traditional and nonlinear) after anesthesia and c ardiac surgery. Design: Prospective. Setting: University hospital. Participants: Patients scheduled for cardiac surgery. Interventions: None. Medical management was not varied as part of this stud y. Measurements and Main Results: HRV was measured in 13 patients from electro cardiograms (ECGs) recorded before anesthesia, during anesthesia but before cardiac surgery, and on the first postoperative day. Anesthesia was induce d with moderate-dose fentanyl. For each EGG, HRV was measured from series o f 400 heartbeat intervals using standard deviation (SD), approximate entrop y (ApEn), and point correlation dimension (PD2). Multivariate repeated-meas ures analyses of variance on ranks and Spearman correlations were performed . All HRV measures decreased significantly with anesthesia. Postoperatively , ApEn recovered to original values. PD2 and SD did not recover with consci ousness and were significantly less than original values. Correlations amon g ApEn, PD2, and SD were weak. Conclusions: Nonlinear measures of HRV differ among themselves after anesth esia and cardiac surgery. The use of multiple nonlinear and traditional mea sures may improve the effectiveness of using HRV to assess the cardiovascul ar system. Copyright (C) 1999 by W.B. Saunders Company.