blood pressure (BP)

Epidemiology

• BP increases more rapidly in women than in men, beginning early in life

Physiology

• driving force that moves blood through the circulatory system
• systolic blood pressure is the blood pressure when the ventricular muscle contracts
• diastolic blood pressure is blood pressure when the ventricular muscle is relaxed between beats.
• mean arterial blood pressure of >= 50 mm Hg may be needed to maintain consciousness
• ambulatory blood pressure monitoring reveals a significant circadian variation in blood pressure
  • in healthy people, blood pressure declines 15% in association with parasympathetic responses during sleep
  • an early morning blood pressure surge occurs, that begins before awakening
  • a small post-prandial decline occurs & a more significant decline in blood pressure occurs during nocturnal sleep
• see exercise & blood pressure for effects of exercise on blood pressure

* also see sleep & blood pressure

Clinical significance

• automated office blood pressure readings are more accurate than manual readings
• a single blood pressure reading is inadequate; multiple measurements (a minimum of 5-6) are needed
  • >= 3 BP readings
  • check home BP monitor in office setting for accuracy
• 36% of in clinic blood pressures > 140/90 are < 140/90 with a 2nd measurement
  • mean systolic BP improvement is 8 mm Hg
• systolic blood pressure > 130 mm Hg & diastolic blood pressure > 90 mm Hg are associated with increased long-term early mortality among male adolescents
• even slightly elevated blood pressure > 120/80 in adults 20-40 years of age linked to lower gray matter volume
• clinic-based blood pressure readings unreliable; ambulatory blood pressure monitoring recommended prior to diagnosis of hypertension & prescription of antihypertensive therapy
• short & long protocols of multiple unattended BP measurements correlate with 24-hour ambulatory monitoring
• long-term elevated blood pressure associated with increased cardiovascular risk
• people with the lowest BP levels (90-114)/(60-74) mm Hg with the lowest risk for cardiovascular disease*
• association of blood pressure with cardiovascular disease decreases with increasing age*
• based on the 33,357-patient ALLHAT trial, there appearsto be a U- or J-shaped association between risk of cardiovascular events & blood pressure
  • nadir of risk
    • all-cause mortality: 140-155/70-80 mm Hg
    • congestive heart failure (CHF): 125-135/70-75 mm Hg
    • myocardial infarction (MI): 110-120/85-90 mm Hg
    • stroke: systolic BP of 110-120 mm Hg
• systolic blood pressure & diastolic blood pressure peak 14-18 years before death, then progessively decline
• attenuation of the decline in blood pressure during sleep is associated with increased amyloid burden in the posterior cingulate gyrus & altered cerebral blood flow of patients with mild cognitive impairment
• persons without blood pressure decline with sleep are at increased risk for cardiovascular mortality, heart failure, & stroke
• nighttime dosing of antihypertensives may be associated with decreases in cardiovascular events & death

blood pressure variability

• systolic blood pressure variability is associated with cognitive impairment in the elderly
• wide variability of blood pressure in hypertensive adults associated with increased cardiovascular risk
  • variability in systolic BP (> 14 mm Hg) (RR=1.3-1.6)
    • higher systolic BP variability associated with falls in nursing home residents
  • variability in diastolic BP also associated with increased risk
• diastolic blood pressure variability in subjects 55-64 years but not in subjects >= 65 years of age is associated with cognitive decline
• blood pressure variability in elderly may be associated with poorer attention span, psychomotor speed & executive function
• systolic short-term blood pressure variability may predict arterial stiffness

* huge study, adults age 30 & older, 5 year follow-up

Procedure

• caffeine, exercise & smoking should be avoided > 30 minute prior to BP measurement
• the patient should be seated quietly for 5 minutes in a chair with feet on the floor (not on an examination table)
• BP measurement in public places with noise level of 74 dB not different from BP in private quiet environment 37 dB
• if systolic BP < 140 mm Hg, automated office BP can be obtained without rest period & multiple readings may be obtained without intervening delay
• bladder of manometer should encircle 80% of arm
• lower edge of cuff 2 cm above antecubital fossa
• arm should be supported & at the level of the heart
  • supporting the arm on the lap overestimates systolic BP by 3.9 mm Hg & diastolic BP by 4.0 mm Hg
  • an unsupported arm at the side overestimates systolic BP by 6.5 mm Hg & diastolic BPby 4.4 mm Hg
• inflate cuff 20-30 mm Hg above palpated pressure
• listen for Korotkoff sounds deflating cuff at rate of 2 mm Hg/sec
• 1st occurrence of repetitive sounds (phase 1) is the systolic blood pressure
• muffling of sounds is phase IV
• disappearance of sounds is phase V
• diastolic blood pressure is phase V
• when Korotkoff sounds are heard all the way to 0 mm Hg, record phase 1, phase IV & phase V, for example: 140/70/0
• average of 2 or more measurements
• blood pressure monitoring should start at age 3

* see ref for ways measuring blood pressure may go wrong (AMA)

Notes

• electronic BP monitors may report systolic BP as slightly lower than that measures intra-arterially & diastolic BP as slightly higher

More general terms

• vital signs (V/S)

More specific terms

• bilateral blood pressure assessment
• blood pressure > 140/90
• blood pressure for HTN/CKD/DM
• blood pressure in the very old
• diastolic blood pressure (DBP)
• early morning blood pressure surge (EMBPS)
• pulse pressure
• systolic blood pressure (SBP)
• toe blood pressure

Additional terms

• ambulatory blood pressure monitoring (ABPM)
• arterial pressure
• blood pressure cuff
• exercise & blood pressure
• home blood pressure monitoring
• hypertension (HTN, high blood pressure, HBP)
• hypotension
• medications that may raise blood pressure
• sleep & blood pressure
• venous pressure