Measuring Your Own Blood Pressure

All patients with kidney disease should learn to measure their own blood pressure in the arm; how often they need to take the measurement depends on whether it is high or not; if it is normal, check it at least once a month to make sure it stays that way. If you have high blood pressure, check it and record it at least once a week, at about the same time of day. Show your blood presssure log to your doctor. If your blood pressure is consistently elevated, or if protein is consistently in your urine, see your doctor.

Devices for self-measurement of blood pressure are available without a prescription at any drugstore. Buy the less expensive variety, with a stethoscope attached, rather than the more expensive electronic variety.

Learning to use a stethoscope takes a bit of practice, but the digital readout device is somewhat less reliable. If you can't master the self-measurement of blood pressure with a stethoscope, get an electronic device. In 1996, Consumer Reports rated 16 makes.

The best way to measure blood pressure is with an inflatable cuff on the upper arm (either arm) and a stethoscope. Inflate the cuff (which must be firmly placed; subjects who are very large should use a larger cuff known as a thigh cuff, placed high on the arm) to a pressure over 200 mm mercury or so, and then gradually deflate it so that the pressure in the cuff falls about 10 mm every two seconds or so, as indicated on the device. When you reach the systolic pressure you will hear a sound through the stethoscope with every heartbeat. Continue to lower the pressure at the same rate. Eventually the sounds will disappear. The pressure at which the sounds disappear is the diastolic blood pressure.

It is important to place the diaphragm of the stethoscope right over the brachial artery. You can locate this spot in the crease of your elbow by feeling there for a pulse. If you place the stethoscope incorrectly, you may not hear anything. There may be variation between beats in both the systolic and the diastolic pressure, particularly if your heart rate is irregular for any reason. Under these conditions, there is necessarily a degree of arbitrariness in deciding exactly what is the systolic and the diastolic pressure. In some individuals, the brachial pulse is not pronounced and it may be very hard to hear anything, even when the stethoscope is placed correctly.

Why measure your own blood pressure? Well, blood pressures measured by patients themselves are often more informative than those measured in the office, for two reasons: (1) water loading for a glomeru-lar filtration rate test increases blood pressure; (2) visiting the doctor's office is anxiety-producing and raises blood pressure. The average of many values recorded by the patient, if accurately measured, gives a much better idea of long-term blood pressure control than does a single value recorded at an office visit.

Current recommendations are to keep mean arterial blood pressure (systolic pressure plus two times diastolic pressure, divided by three) under 95 mm Hg in patients with renal failure. This is lower than has been recommended in the past. A blood pressure of 130/80, for example, signifies a mean arterial pressure of 97 mm Hg and is slightly high. Pronounced hypertension (say, over 160/100) can not only damage the kidney but also can lead to strokes, visual disorders, and heart failure, and must be treated urgently. According to recent information, systolic blood pressure is much more important than diastolic blood pressure.

If you have high blood pressure, check it and record it at least once a week, at about the same time of day. Show your blood pressure log to your doctor. If your blood pressure is consistently elevated, or if protein is consistently in your urine, see your doctor.

As noted earlier, there is a strong relationship between hypertension and salt balance, and this relationship is even stronger in the presence of kidney failure. Many patients will present with hypertension accompanied by signs of fluid retention; when appropriate diuresis (excretion of salt and water excess) is achieved, the blood pressure may return to normal. It follows that control of salt balance should be a first priority in treating hypertension in patients with kidney disease, and that variations in blood pressure associated with and caused by salt and water retention are best treated with salt restriction and diuretic drugs, as described in the preceding section.

But achieving an optimal extracellular fluid volume often does not bring blood pressure back to normal. Most patients will require antihy-pertensive drugs, commonly in combination.

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