Blood Pressure

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Last modified 21/03/2015

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Chapter 9. Blood Pressure

Blood pressure readings provide significant information about the child’s health status. Until recently, children younger than 3 years were commonly not screened for blood pressure because of the extra skill and patience required to obtain a blood pressure reading in such young patients. Most children with hypertension have renal disease; many fewer have coarctation of the aorta or pheochromocytoma. Screening of blood pressure in young children permits early detection of serious disorders and should be performed at least yearly on children from 3 years of age to adolescence. Blood pressure determination is routine on admission to health care facilities and in postoperative procedures. It should also be performed after invasive diagnostic procedures and before and after administration of drugs known to alter blood pressure. Blood pressure is taken whenever a child “feels funny” or when a child’s condition deteriorates.

Anatomy and Physiology

Blood pressure is a product of cardiac output and increased peripheral resistance. In the neonate, systolic blood pressure is low, reflecting the weaker ability of the left ventricle. As the child grows, the size of the heart and of the left ventricle also increases, resulting in steadily increasing blood pressure values. At adolescence the heart enlarges abruptly, which also results in an increase in blood pressure values, comparable to those of the adult (Table 9-1).

**Table 9-1** Blood Pressure Values for 90th and 95th Percentiles of Blood Pressure at Various Ages^*
Modified from Hockenberry MJ et al: *Wong’s nursing care of infants and children,* ed 7, St Louis, 2003, Mosby.© Elsevier Inc.2003
Age	Girls Systole (mmHg)	Girls Diastole (mmHg)	Boys Systole (mmHg)	Boys Diastole (mmHg)
^*Values that fall at or below the lower number in each range are considered normotensive. Values that fall above the higher number in each range might be indicative of hypertension.
1 yr	97–107	53–60	94–106	50–59
3 yr	100–110	61–68	100–113	59–67
6 yr	104–114	67–75	105–117	67–76
8 yr	108–118	70–78	107–120	71–80
10 yr	112–122	73–80	110–123	73–82
12 yr	116–126	75–82	115–127	75–83
14 yr	119–130	77–85	120–132	76–84
16 yr	122–132	79–86	125–138	79–87

An increase in cardiac output or in peripheral resistance will raise blood pressure. Decrease in cardiac output or in peripheral resistance will lower blood pressure. Overall maintenance of blood pressure reflects an intimate relationship among cardiac output, peripheral resistance, and blood volume, which can be influenced by several other factors (Table 9-2).

**Table 9-2** Influences on Blood Pressure
Influence	Effect
Medications	Narcotic analgesics, general anesthetics, diuretics decrease blood pressure. Aminophylline increases blood pressure.
Conditions	Blood pressure decreases during hemorrhage. Blood pressure increases with renal disease, increased intracranial pressure, coarctation of aorta (blood pressure in arms), pheochromocytoma, hyperthyroidism, diabetes mellitus, and acute pain. Pulse pressure widens with increased intracranial pressure.
Diurnal variation	Blood pressure usually is higher during morning and afternoon than during evening and night.
Apprehension and anxiety	Increases blood pressure.
Increased activity	Increases blood pressure.