|Budget Amount *help
¥2,800,000 (Direct Cost : ¥2,800,000)
Fiscal Year 1998 : ¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1997 : ¥700,000 (Direct Cost : ¥700,000)
To evaluate the role of parasympathetic nervous system and endothelium- derived relaxing factor on hypotension during dental extraction, we have measured the changes in blood pressure (BP), pulse rate, and heart rate variability in young and old patients (study 1) as well as in normotensive and hypertensive subjects (study 2). The study included 20 young, 20 old subjects (study 1), 18 essential hypertensives and age and sex matched 18 normotensive controls (study 2) who underwent tooth extraction at our hospital. Holter electrocardiographic monitoring was used to determine the power spectrum of R-R variability before and during dental surgery. The low frequency (LF : 0.041 to 0.140 Hz), high frequency (HF : 0.140 to 0.500 Hz), and total spectral powers (TF : 0.000 to 4.000 Hz) were calculated, and the ratio of LF to HF and percentage of HF relative to TF(%HF : HF/TF x 100) were used as indexes of sympathetic and parasympathetic activities, respectively. The blood was also drawn in volu
nteer during dental extraction to measure blood NO_x and catecholamines concentrations (study 3).
Studyl : The baseline BP for study 1 subjects was 121/70 mmHg, Local anesthetic lidocaine containing epinephrine (1 : 80000) increased BP, which was further increased up to 132/173 mmHg during dental extraction. The BP elevation was prominent in subjects older than 40 years old. The percent HF was suppressed by local anesthetic injection in younger patients, while LF/ HF was enhanced in young subjects but suppressed in old subjects during local anesthesia. Study 2 : The resting BP was 149/ 85mmHg for hypertensive patients, which was significantly higher than that for normotensive patients (119/71 mmHg). The baseline pulse rate was similar in both groups. BP increased during tooth extraction in both groups ; however, changes in BP did not differ between two groups. Administration of local anesthetic significantly decreased the %HF in normotensive patients In contrast, the LF/HF significantly decreased during the administration of local anesthesia and tooth extraction in hypertensive patients. Study 3 : Dental surgery increased blood concentrations of adrenaline and noradrenaline, but did not change the concentration of NO_x.
These results showed that pressor response induced by tooth extraction was greater in older subjects than in younger subjects, while it was similar between normotensive and hypertensive patients. Cardiac parasympathetic and sympathetic nervous systems during dental surgery may be different between young and old subjects, and also differ in normotensive subjects and hypertensive patients. Endothelium- derived relaxing factor as NO_s may not play major roles on BP changes during dental treatment. Both hypertension and aging might suppress increases in sympathetic activity induced by dental surgery.