Figure 4. (A) Systolic blood pressure (SBP) after intrathecal injection of 5 [micro sign]g sufentanil plus 30 [micro sign]g clonidine (SUF-CLO) or 5 [micro sign]g sufentanil alone (SUF). Despite prompt treatment of hypotension with intravenous ephedrine, the SBP remained significantly lower in the SUF-CLO group (P = 0.02). *P < 0.05 with Bonferroni corrections compared with the SUF group. (B) Kaplan-Meier survival analysis representing the time course of intravenous ephedrine administration after intrathecal injection of 5 [micro sign]g sufentanil plus 30 [micro sign]g clonidine (dotted line) or 5 [micro sign]g sufentanil alone (solid line). Administration of ephedrine was still required 65 - 120 min after intrathecal injection on four occasions in the SUF-CLO group, whereas no patient had hypotension beyond 45 min in the SUF group.