Unfortunately, there is not a simple answer to this question. Abnormal elevation of blood pressure in a given individual best defines the hypertensive state. For example, a blood pressure of 130/80 mmHg in a 10-year-old is considered hypertensive and is greater than the 95th percentile for that age. Generally, physicians accept a blood pressure 140/90 mmHg in patients older than 30 years and blood pressure 160/95 mmHg in patients older than 65 years as being hypertensive.
What are the two hemodynamic determinants of blood pressure? Which predominates in essential hypertension?
Arterial blood pressure is the product of cardiac output and systemic vascular resistance. By definition, systemic vascular resistance is elevated in hypertension, but it is unclear if it is the initiating event or response to increases in cardiac output. Relative contributions of both factors to the hypertensive state vary among patients. Both black and elderly hypertensive patients appear to have increased plasma volumes and cardiac output contributing to the hypertensive process, and they may respond more favorably to a diuretic or calcium channel blocker in the treatment of their hypertension.