Following confirmation of a sufficient anesthetic effect, intravenous sedation with continuous infusion of propofol 1 to 2 mg/kg/h and midazolam 20 to 40 μg/kg bolus together with inhalation of oxygen 3 L/min via nasal cannula was initiated. After confirming Verrill sign, implant surgery was initiated. During operation, the propofol dose was adjusted to maintain the optimum conscious sedative condition (level 2 on the Ramsay sedation scale) [5], and local anesthesia was added when the patient complained of pain. On completion of surgery, administration of oxygen and propofol were terminated and the patient was observed for about 1 h, until normal cognitive and motor functions were restored.

The subjects were divided into two groups: a normotensive group with no history of hypertension and a hypertensive group with a history of hypertension. Thirteen patients who had no history of hypertension were included in the hypertensive group, since they indicated SBP ≥160 mmHg on arrival at the office and were later diagnosed with essential hypertension by cardiologists. Furthermore, the patients in the hypertensive group were divided into two subgroups: with or without nifedipine administration.

From the clinical chart, data of SBP, DBP, PR, and percutaneous oxygen saturation (SpO₂) were sampled at the point of arrival to the office, prior to the initiation of sedation, 30 min after the initiation of operation, and on completion of operation. Furthermore, rate pressure product (RPP: SBP × PR) was calculated.

There were two primary outcome measures: (1) incidence of improved hypertension following oral nifedipine and (2) incidence of normal ranges of hemodynamic parameters during surgery. The secondary outcome variable was incidence of hypertension related to perioperative complications.

In this study, we used data from all cases (516 cases) for statistical analysis.

Data were described as mean ± standard deviation. The unpaired t test was used to compare demographic variables between groups. Fisher's exact test was used to compare ratios of patients in hypertensive group between subgroups. One-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test was performed to examine the change in the values of parameters. Repeated measures ANOVA followed by Dunnett's multiple comparison test was used to compare the values of parameters in groups at each time point. Statistical analysis was performed using Prism 5 for Windows Ver. 5.01 (GraphPad Software Inc., San Diego, CA, USA). The significance level was set at p < 0.05.