BEYOND BLOOD PRESSURES

DEVELOPED BY MARCUS LABARBERA

FEBRUARY 1997

Page 1 Taking your patients blood pressure is one of the most basic parts of any exam. I’m sure it would surprise you to learn there is more to assessing your patients hemodynamic status than a quick palpated blood pressure. Let’s start with the blood pressure cuff its self, the recommended adult cuff should be about 80% of the circumference of the arm or (13 cm by 35 cm). Fig. 1-1 FALSELY LOW: FALSELY HIGH: Cuff too wide Cuff too narrow Bladder too short Large arm Thin arm Patient discomfort Rapid deflation Repeated readings Overlooking auscultatory gap Distended urinary bladder Too firm pressure with stethoscope

The recommended procedure for taking a blood pressure: 1) Select a cuff of the appropriate size for the patient. 2) Place the cuff approximately 2.5 cm above the crease of the elbow. 3) Find the Brachial arterial pulse, while palpating the brachial pulse

rapidly inflate the cuff about 30 mm/Hg above the level you last felt the pulse (this will help avoid falsely low pressures due to the auscultatory gap).

4) Because the Korotkoff’s sound is relatively low pitched, they can be

heard better with the bell of the stethoscope. Place the bell of the stethoscope lightly over the brachial artery; (remember that when using the bell of the stethoscope not to press too hard causing the skin underneath the bell to act as a diaphragm).

Page 2 5) Inflate the cuff again, 30 mm/Hg above the palpatory systolic pressure,

then slowly deflate the cuff at a rate of 2 to 3 mm/Hg per second. 6) Note the level, at which you hear at least two consecutive beats, (this

will be phase 1 of the Korotkoff sounds). The number you have marked is the systolic blood pressure. It is important to note that rapid deflation of the cuff will lead to under estimation of the systolic pressure and over estimation of the diastolic pressure.

7) Continue to lower the cuff pressure until the Korotkoff sounds muffle

(phase 4), and disappear (phase 5), then rapidly deflate the cuff to zero. (The point at which the sounds disappear (phase 5), is usually only a few points under where the sounds muffle (phase 4). If there is more than a 10 mm/Hg difference between phase 4 and phase 5 record both numbers. Example: 150/80/68

phase 1 phase 4 phase 5

In some patients the muffling point (phase 4) may not disappear at all such as the case in aortic regurge

Other factors to consider when taking a blood pressure: 1) Avoid slow or repetitive inflation of the cuff because this will lead to

temporary venous congestion and may artificially lower the systolic blood pressure and increase the diastolic pressure.

2) The blood pressure should be taken in both arms at least once,

especially if you suspect a CVA or subclavian steal syndrome. 3) When the patient exhibits syncope, postural dizziness, or you suspect

hypovolemia, and repositioning the patient is not contraindicated, orthostatic blood pressures should be considered. These should be taken in three positions: supine, sitting, and standing. A fall in blood pressure of more than 20 mm/Hg especially when symptomatic indicates orthostatic (postural) hypotension.

Please note, the auscultatory gap, mentioned earlier, is easily overlooked by even the most careful practitioner. In patients who exhibit an auscultatory gap there may be as much as a 100 point difference between a perceived

Page 3 correct blood pressure and a blood pressure that takes in to account the possibility of an auscultatory gap. Auscultatory gaps have been reported in patients with the diagnosis of: Hypertension, Aortic valve disease, Heart failure, and marked Bradycardia. Methods to consider when taking a blood pressure: 1) The Palpatory Method

This method, introduced by Riva – Rocci 1896, Produces slightly Lower readings than other methods. After inflating the cuff to above the systolic pressure, slowly release the pressure. At the point that you first feel the arterial pulse mark the pressure and this is the approximate systolic blood pressure. This technique is a time saver if frequent blood pressures are required to monitor trends. Many practitioners are unaware that a diastolic pressure can be obtained using this technique. The diastolic pressure can sometimes be obtained more easily as your inflating the cuff. Slowly inflate the cuff paying close attention to the arterial pulse, at The point at which the arterial pulse assumes a taping quality is the approximate diastolic pressure. Continue to inflate the cuff above the systolic pressure and obtain the systolic pressure as you deflate the cuff.

2) The Oscillometric Method This method, introduced by Pachon 1909, is based on the fact that as the cuff is deflated small oscillations abruptly become larger denoting the systolic pressure. As the cuff pressure continues to drop the warning oscillations abruptly decrease or disappear denoting the diastolic pressure. This technique also allows for calculation of the mean arterial pressure (MAP) by marking the point of maximal fluctuation during deflation. This is the technique generally used in automated blood pressure machines.

3) The Flush Method This method, introduced by Gaertner 1903, is of particular use in assessing assessment of pulseless limbs, as in: arms in aortic arch syndrome and legs in coarctation of the aorta.

Page 4 The cuff is applied to the limb; the limb is then elevated until it blanches. At this point the cuff is inflated and the arm is lowered to the level of the heart. The cuff is slowly deflated and the skin is noted for a flush appearance, at this point marks the gauge reading and this will be your approximate mean arterial pressure.

4) The Subjective Method

This method is a consideration when an arterial pulse is palpable but you are unable to hear Korotkoff sounds and you have an alert, competent patient. The cuff is placed and inflated as usual, the patient is instructed to feel for the first pulsations as the cuff is deflated, this will mark the approximate systolic pressure. Continue to deflate the cuff and instruct the patient to note when the pulsation abruptly ends, this will mark the approximate diastolic pressure. Recommended Reading: Bed Side Cardiac Diagnosis Henry J.L. Marriott J.B. Lippincott Company ISBN: 0 -397-51085-3 A Guide To Physical Examination And History Taking Barbara Bates J.B. Lippincott Company ISBN: 0-397-54623-8