Figure 5. (A) Spontaneous cardiac baroreflex slope. (B-D) RR interval spectral power (B, total power, 0.0-0.5 Hz; C, low frequency power, 0.00-0.15 Hz; D, high-frequency power, 0.15-0.50 Hz), shown as mean +/− SEM. Patients given placebo demonstrated reductions in cardiac baroreflex slope and RR interval power compared with preinduction values, whereas patients given clonidine demonstrated a preservation of spontaneous cardiac baroreflex slope and RR interval power in the postoperative period (Treatment x Study period interaction of ANOVA: baroreflex slope P = 0.04; total power P = 0.001; low-frequency power P = 0.005; high-frequency power P = 0.001). *Significant difference between groups;[dagger] significant difference from respective baseline value by post hoc Tukey's tests.