Lab 3 - Blood Pressure

Blood pressure (definition)

The force exerted on the walls of an artery by the pulsing blood under pressure from the heart. Blood flows from areas of high pressure to low pressure.

Systolic blood pressure

The peak (maximum) pressure when the heart contracts and ejects blood into the aorta.

Diastolic blood pressure

The minimal pressure exerted against the arterial walls at any time, when the ventricles relax.

Unit of BP and how it is recorded

Millimetres of mercury (mm Hg); recorded systolic over diastolic (e.g., 120/80).

Pulse pressure

Difference between systolic and diastolic. Normal 30 to 50 mm Hg.

Acceptable adult BP (Box 31.1)

Systolic 120 to 139 mm Hg; diastolic 80 to 89 mm Hg.

Your notes: systolic vs diastolic sounds

Systolic = the FIRST sound you hear. Diastolic = the LAST sound expected at the end (when you can no longer hear).

Hypertension

The most common alteration in BP; often ASYMPTOMATIC. Associated with thickening and loss of elasticity of arterial walls: increased peripheral vascular resistance, so the heart pumps against greater resistance and blood flow to vital organs (heart, brain, kidney) decreases.

Hypertension: symptoms (Skill 31.5)

Headache (usually occipital), flushing of the face, nosebleed, fatigue in older persons; often no symptoms until pressure is very high.

Hypertension diagnosis (Hypertension Canada 2020): urgency/emergency

A patient with features of hypertensive urgency or emergency is diagnosed as hypertensive and treated immediately.

Hypertension diagnosis: criterion 1

Mean BP (office OBPM or automated AOBP) systolic >= 180 mm Hg or diastolic >= 110 mm Hg.

Hypertension diagnosis: criterion 2 (AOBP)

First AOBP reading systolic between 135 and 179, or diastolic between 85 and 109 mm Hg.

Hypertension diagnosis: criterion 3 (OBPM)

OBPM systolic between 140 and 179, or diastolic between 90 and 109 mm Hg.

ABPM diagnosis of hypertension

Ambulatory BP monitoring: mean systolic >= 135 or diastolic >= 85 mm Hg; OR 24-hour mean systolic >= 130 or diastolic >= 80.

HBPM (home BP) series

Two readings each morning and evening for 7 days (28 total). Discard day 1 and average the last 6 days. Mean systolic >= 135 or diastolic >= 85 = hypertension.

OBPM vs AOBP

OBPM = office BP with an electronic upper-arm device and a provider in the room. AOBP = automated office BP with the patient unattended in a private room (preferred in-office method).

If OBPM is used: how many readings?

At least three readings; discard the first and average the rest.

White coat hypertension (white coat syndrome)

BP is elevated during a visit to a health care provider (e.g., due to nervousness) but normal elsewhere. Affected patients are more likely to develop true hypertension over time. Home or ambulatory monitoring is used to diagnose it.

Masked hypertension

BP reading is NORMAL while with a health care provider but becomes ELEVATED at home.

How to rule out white coat hypertension

Out-of-office BP measurement (ABPM preferred, or home BP) before the second visit.

White coat vs masked: which is high in the office?

White coat = high in the office. Masked = high at home.

Your notes: white coat syndrome

The patient may have a higher BP than usual due to nervousness.

First-line lifestyle interventions for hypertension (Hypertension Canada 2022)

Becoming more physically active; weight reduction; moderation in alcohol intake; eating healthier; relaxation therapies; smoking cessation.

Risk factors for hypertension (Leung 2019)

Physical inactivity, a diet low in fruits and vegetables, overweight/obesity, diabetes, chronic kidney disease. Family history is also a significant risk.

Hypertension: major risk for what?

Cardiovascular disease and the number one risk factor for stroke.

BP elevated above acceptable range: what to do

Repeat in the other arm and compare; verify cuff size and placement; ask a colleague to repeat in 2 minutes; watch for headache, confusion; report immediately to the nurse in charge/provider; give antihypertensives as ordered.

Hypotension

Systolic BP of 90 mm Hg or lower. Some adults normally run low, but for most people it is abnormal and linked to illness.

Causes of hypotension

Dilation of arteries in the vascular bed; loss of a substantial amount of blood volume (hemorrhage); failure of the heart muscle to pump adequately (e.g., myocardial infarction).

Hypotension: symptoms (Skill 31.5)

Dizziness, mental confusion, restlessness; pale, dusky or cyanotic skin and mucous membranes; cool, mottled skin on the extremities.

When is hypotension life-threatening?

With pallor, skin mottling, clamminess, confusion, increased heart rate or decreased urine output: report to the provider immediately.

Orthostatic (postural) hypotension

A normotensive person develops symptoms of low BP when rising to an upright position. Volume-depleted patients' vessels are already constricted, so BP drops significantly on standing and heart rate rises to compensate.

Who is at risk for orthostatic hypotension?

Patients who are dehydrated, anemic, on prolonged bed rest, or with recent blood loss.

How to assess orthostatic hypotension

Take BP and pulse supine, sitting and standing, 1 to 3 minutes after each position change. Usually detected within a minute of standing. Watch for fainting, weakness, light-headedness.

Orthostatic readings: how to record

Record the position with each BP, e.g., '140/80 supine, 132/72 sitting, 108/60 standing'.

If orthostatic hypotension occurs

Assist the patient to a lying position and notify the provider or nurse in charge.

Can orthostatic measurements be delegated to a UCP?

No. It requires advanced reasoning and ongoing nursing judgement.

BP not sufficient for perfusion: what to do

Compare with baseline (systolic 90 is acceptable for some patients); position supine to enhance circulation and restrict activity; assess for decreased cardiac output (weak/thready pulse, confusion, pallor, cyanosis) and notify immediately; IV rate or vasoconstrictors if ordered.

BP reading cannot be obtained: what to do

Check pulse and respiratory rate for a crisis; assess for decreased cardiac output; use alternative sites/methods (lower extremity, Doppler, palpation for systolic); repeat with a sphygmomanometer (electronic devices are less accurate in low blood flow).

Skill 31.5 Step 1

Identify the patient with two person specifics.

Skill 31.5 Step 2: risk factors for BP alteration

Cardiovascular disease, renal disease, diabetes, circulatory shock, acute or chronic pain, rapid IV fluids/blood products, increased intracranial pressure, postoperative conditions, toxemia of pregnancy.

Skill 31.5 Step 3: choosing the site (avoid)

Avoid the extremity with IV fluids infusing; AV shunt or fistula; side of breast or axillary surgery; traumatized or diseased extremity; one needing a cast or bulky bandage. Use the lower extremities if the brachial arteries are inaccessible.

Skill 31.5 Step 4

Determine the previous baseline BP from the record.

Skill 31.5 Step 5: preparing for accuracy

Identify factors that interfere (anxiety, stress, pain). Avoid caffeine and tobacco for 30 minutes before; rest quietly for 5 minutes.

Smoking and caffeine effects on BP

Smoking raises BP immediately, lasting up to 15 minutes. Caffeine raises BP for up to 3 hours.

Skill 31.5 Step 6

Explain; patient rests at least 5 minutes sitting or lying (wait 1 minute if standing); no talking during measurement.

Skill 31.5 Step 7: cuff size

Select the appropriate size. Too small (or loose) = falsely HIGH; too large = falsely LOW.

Skill 31.5 Step 8

Check cuff components: release valve clean and moves freely; bulb and tubing intact, no leaks.

Skill 31.5 Step 9-10

Hand hygiene. Sitting or lying; warm, quiet, relaxing room.

Skill 31.5 Step 11: arm position

Forearm at HEART level, supported, palm up, thigh flat (knee slightly flexed if using the leg). If sitting: legs NOT crossed, feet touching the floor.

Why support the arm?

An unsupported arm may cause isometric exercise that raises diastolic BP. Leg crossing falsely raises BP.

Skill 31.5 Step 12

Expose the arm by fully removing constricting clothing.

Skill 31.5 Step 13: cuff placement

Palpate the brachial artery (popliteal for the leg). With the cuff fully deflated, centre the bladder over the artery. Position the cuff 2.5 cm above the site of pulsation (antecubital space). Wrap evenly and snugly. Never over clothing. (Your notes say 3 cm up from the bend of the elbow; textbook says 2.5 cm.)

Cuff too loose: effect

Falsely high reading.

Skill 31.5 Step 14

Position the aneroid manometer gauge no further than 1 metre away.

Two-step method: purpose

Provides an estimate of systolic pressure to guide cuff inflation level, particularly when the baseline BP is unknown.

Two-step method: step 1 (palpatory estimate)

Palpate the brachial (or popliteal) pulse distal to the cuff while rapidly inflating to 30 mm Hg ABOVE the point where the pulse disappears. Slowly deflate and note the reading when the pulse reappears. Deflate fully and WAIT 1 MINUTE.

Two-step method: why wait 1 minute?

Completely deflating the cuff prevents venous congestion and false high readings.

Two-step method: step 2 (auscultation)

Earpieces in (clear, not muffled). Relocate the brachial pulse and place the bell/diaphragm over it without touching the cuff or clothing. Close the valve clockwise. Rapidly inflate to 30 mm Hg above the palpated systolic. Release slowly at 2 to 3 mm Hg per second.

One-step method

Used for frequent measurements and when the systolic inflation level is already known. Same auscultation steps without the palpatory estimate.

Your notes: when you know the baseline BP

1) Feel for the brachial pulse, 2) Put the cuff on and pump air until 30 mm Hg above the known systolic, 3) Place the stethoscope over the brachial pulse flat on the skin, 4) Release pressure slowly and listen for the first sound.

Your notes: when you don't know the baseline BP

1) Feel for the brachial pulse, 2) Place the cuff on, 3) Feel the radial pulse and pump until you can't feel it, 4) Note that number, then add 30 mm Hg = inflation/starting point, 5) Deflate completely, 6) Place the stethoscope over the brachial pulse and under the cuff, flat on the skin, 7) Pump to the inflation point and release slowly.

Why deflate the cuff quickly after the last sound?

Continuous inflation causes arterial occlusion: numbness and tingling in the arm.

Stethoscope placement errors

Poor fit or poor placement gives muffled sounds: false LOW systolic and false HIGH diastolic.

Skill 31.5 Step 16: how many readings?

At least 3 measurements in the same arm, patient in the same position. Discard the FIRST; average the other two.

Skill 31.5 Step 17: first-time BP

Repeat on the other extremity (compare). A difference of 5 to 10 mm Hg between extremities is normal.

Which arm do you use afterward?

The arm with the higher pressure (unless contraindicated).

Skill 31.5 Step 19

Wipe the cuff with disinfectant (or keep a disposable cuff in the room until no longer needed, then dispose per policy).

Skill 31.5 Steps 20-23

Discuss findings; hand hygiene; compare to baseline and age-appropriate values; correlate BP with pulse and other cardiovascular signs (BP and heart rate are interrelated).

Recording BP

Record on the flow sheet or nurses' notes; report abnormal findings; inform the patient of the value and need for periodic reassessment.

Delegation: what to tell a UCP about BP

Which limb; correct cuff size; frequency; patient's usual values; abnormalities to report.

Equipment for BP (auscultation)

Aneroid sphygmomanometer, cloth or disposable vinyl cuff of the right size, stethoscope, alcohol swab, pen and flow sheet.

Home care: BP

Find the quietest room; consider an electronic cuff in the home if the patient has hearing difficulties, adequate finances and dexterity.

Your notes: tips for BP

Ask the person's activity before taking BP (first thing in the morning is best); arm at the same level as the heart; right size cuff; make sure the patient is calm; stethoscope always flat against skin, not over clothing.

Table 31.9: bladder/cuff too WIDE

False LOW reading.

Table 31.9: bladder/cuff too NARROW or too short

False HIGH reading.

Table 31.9: cuff wrapped too loosely or unevenly

False HIGH reading.

Table 31.9: deflating the cuff too slowly

False HIGH diastolic reading.

Table 31.9: deflating the cuff too quickly

False LOW systolic and false HIGH diastolic reading.

Table 31.9: arm BELOW heart level

False HIGH reading.

Table 31.9: arm ABOVE heart level

False LOW reading.

Table 31.9: arm not supported

False HIGH reading.

Table 31.9: stethoscope fits poorly or examiner's hearing impaired (muffled sounds)

False LOW systolic and false HIGH diastolic reading.

Table 31.9: stethoscope applied too firmly against the antecubital fossa

False LOW diastolic reading.

Table 31.9: cuff inflating too slowly

False HIGH diastolic reading.

Table 31.9: repeating assessments too quickly

False HIGH systolic reading.

Table 31.9: inadequate inflation level

False LOW systolic reading.

Table 31.9: multiple examiners using different Korotkoff sounds for diastolic

False HIGH systolic and LOW diastolic reading.

Which errors cause a falsely HIGH BP? (list)

Cuff too narrow/short; cuff loose or uneven; arm below heart level; arm unsupported; repeating too quickly (systolic); deflating slowly or inflating slowly (diastolic).

Which errors cause a falsely LOW BP? (list)

Cuff too wide; arm above heart level; inadequate inflation level (systolic); stethoscope too firm (diastolic); deflating too fast (systolic); muffled sounds (systolic).

Your BP is oddly high: first things to check

Cuff size and placement, arm position at heart level and supported, legs uncrossed, patient rested 5 minutes and no caffeine/tobacco, then repeat in the other arm.

Patient anxious, BP higher than usual

Consider white coat effect; rest the patient and repeat; consider home/out-of-office monitoring if recurrent.