In 44 (8.5%) of the 516 implant surgery cases, oral nifedipine had to be administered, since preoperative SBP was higher than 160 mmHg in these patients. Within 30 min of administration of nifedipine, SBP of hypertensive patients decreased to a similar range as that of hypertensive patients who did not need administration of oral nifedipine. Intravenous sedation after nifedipine administration to hypertensive patients resulted in stable hemodynamics during implant surgery.
The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure [6] classified hypertensive patients into five categories based on systolic or diastolic blood pressure. Patients with normal blood pressure (<120/80 mmHg), prehypertension (120 to 139/80 to 89 mmHg), or stage I hypertension (140 to 159/90 to 99 mmHg) can receive regular dental care, though a stress reduction protocol is necessary for stage I hypertension [2,7]. In accordance with the guidelines during oral surgery, the blood pressure of hypertensive patients should be maintained at a normal or prehypertension level. RPP is a reliable predictor of myocardial oxygen consumption [8], and RPP >12,000 bpm × mmHg is associated with myocardial ischemia [9,10]. In this study, although blood pressure was managed by a physician, hypertensive patients showed SBP >160 mmHg when they visited the dental office for dental implant surgery, and 50% of hypertensive patients showed high RPP after 30 min of rest. In patients presenting with high blood pressure and high RPP, anxiety and fear must be reduced by conscious sedation and antihypertensives to prevent cardiovascular complications during dental implant surgery.
Increases in SBP due to psychological stress are proportional to age and baseline blood pressure [4]. Intravenous sedation stabilizes measurable changes in blood pressure and pulse rate due to fear and anxiety about dental treatment and has been used to manage patients with ischemic heart disease and hypertension [11]. In this study, the effect of intravenous sedation was as follows: SBP and RPP, compared with those prior to intravenous sedation, were decreased by 15% and 20% in patients with normal blood pressure, 15% and 25% in hypertensive patients without oral nifedipine, and 15% to 20% and 20% to 30% in hypertensive patients with administered nifedipine, respectively. That is, SBP and myocardial oxygen consumption of prehypertension and stage I hypertension can be reduced to the levels recommended for dental treatment before surgery by intravenous sedation.
For patients with stage 2 hypertension before operation, it is difficult to maintain the recommended blood pressure during surgery using only intravenous sedation, and it is necessary to decrease blood pressure by antihypertensive drugs. In this study, the blood pressure of patients with sustained hypertension was reduced to stage I hypertension about 30 min after administration of oral nifedipine. On the other hand, the decrease in RPP after oral nifedipine administration was not less than 12,000 bpm × mmHg, which could be due to the fact that an increase in pulse rate with nifedipine by reflex tachycardia. Thereafter, blood pressure and RPP during surgery under intravenous sedation has remained at levels similar to those of hypertensive patients with well-controlled blood pressure. Maximum effect (21.4% decreases in SBP) appears in 30 to 60 min and lasts about 3 h on oral administration of nifedipine [12]. The half-lives of oral nifedipine, diltiazem and verapamil, and calcium antagonists are 0.2 to 1 h, 6 to 8 h, and 6 to 8 h, respectively [13]. Since oral nifedipine has the properties of fast onset (30 to 45 min) [14] and relatively short duration, it is suitable for outpatient dental implant surgery and is useful in perioperative management of patients with hypertension.
The overdose of vasoconstrictor that is added to the local anesthetic in order to prolong the anesthetic effect and hemostatic action may cause increased blood pressure and arrhythmias. Elevation of blood pressure in hypertensive patients is greater than that in normotensive patients during dental surgery [15]. Although there is an increase in blood pressure and tachycardia when using three cartridges of local anesthetic containing epinephrine 1:10,000 (5.4 ml), there are no adverse symptoms in patients with normal blood pressure [16]. Little recommended that the amount of local anesthetic solution administered should be less than two cartridges (3.6 ml) for patients with hypertension [1]. Nakamura et al. reported that patients with essential hypertension who have been administered nifedipine can receive less than 3.6 cartridges of local anesthetic containing epinephrine 1:80,000 (6.4 ml) [17]. The administration of exogenous epinephrine with local anesthesia produces the highest plasma concentration in 3 to 6 min and lasts for 20 min [18]. It has been reported that the anesthetic rate of 2% lidocaine containing 1:10,000 epinephrine is 47% 45 min after administration and 27% 60 min after administration [19]. During dental implant surgery which requires a relatively long duration and a wide field in patients with hypertension, administration of conduction anesthesia including inferior alveolar block and posterior superior alveolar nerve block is desirable. When the patient complains of pain, it is important to add local anesthesia while monitoring blood pressure to prevent increased blood pressure caused by pain.
Implant surgery is performed in patients with a wide age range, including elderly patients with hypertension. Dentists or oral surgeons often encounter hypertensive patients who are undiagnosed or noncompliant. Among Japanese over the age of 30, 60% of men and 44.6% of women suffer from high blood pressure, and 33.8% of men and 25.6% of women with a history of hypertension have not been managed medically [20]. In this study, though 13 of the patients did not have a history of hypertension, they were diagnosed with essential hypertension by a physician because they had high blood pressure before surgery. Among patients with a history of high blood pressure, 31 patients (29%) showed high blood pressure before surgery. Because there are many of dental patients with undiagnosed or noncompliant hypertension, blood pressure measurement before treatment, particularly invasive surgery, is indispensable.
For dental implant surgery in hypertensive patients who are not adequately controlled, the application of intravenous sedation and preoperative antihypertensive medication would be useful in order to prevent perioperative hypertension crisis including hypertension emergency with end-organ damage or hypertension urgency without end-organ damage. Since sublingual administration of immediate-release (IR) nifedipine may cause side effects such as significant decrease in blood pressure, reflex tachycardia, and acute myocardial infarction [21], the sublingual administration of IR nifedipine to hypertension crisis has not been approved by the Food and Drug Administration (1985) and Japanese Society of Hypertension Guidelines for the Management of Hypertension (2000). Since we could manage patients with high blood pressure without any cerebrovascular complications by oral administration of nifedipine under closely monitoring, it may be concluded that preoperative administration of oral nifedipine to patients with high blood pressure may be effective to prevent hypertensive crisis due to sudden rise in blood pressure during surgery. Further studies are necessary to evaluate the usefulness of captopril, clonidine, and labetalol, which have been reported as alternatives to nifedipine in emergency hypertension [22-24] in patients with high blood pressure.