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By Dr. Mark Shapiro

Hypertension and kidney disease

Elevated blood pressure (BP), also known as hypertension, is common in modern day society. Approximately 30 percent of adult Americans are believed to have hypertension when defined as a blood pressure greater than 140 (systolic – the top number is the pressure when the heart pumps blood out) over 90 (diastolic – the bottom number is the pressure when the heart relaxes before the next beat). This definition of hypertension reading greater than 140/90 is based on two or more doctor’s office blood pressure measurements after an initial screening while a patient is off blood pressure medicine.

Defining when rising blood pressure becomes hypertension is important, because having this condition raises the risk of serious complications, such as strokes, heart attacks and premature death. Reducing blood pressure in patients with hypertension reduces the risks of such events.

High blood pressure is even more common in persons with chronic kidney disease (CKD), and can affect as many as 80 percent of patients. The reasons for this are complicated, and may depend on the underlying causes of the kidney disease. Activation of certain hormonal systems and parts of the central nervous system play a role in this. The retention of salt and fluids by the kidneys also is an important factor, and treatment is often directed at eliminating this excess salt and water through the use of diuretics, a medicine prescribed by a doctor. There are a variety of other medication categories used to lower blood pressure in kidney patients, since people with kidney disease seem to be at even higher risk of complications if high blood pressure is not properly treated.

Not only does kidney disease cause high blood pressure; high blood pressure can also cause or worsen kidney disease. This may be especially true in patients with diabetes and other specific disorders. Having high blood pressure can cause gradual injury to parts of the kidney that filter the blood, such as the glomeruli.

This can sometimes cause or speed up the development of kidney failure, at which point a person would need to have kidney replacement therapy, such as dialysis or a kidney transplant. Continued treatment with appropriate medications can usually control blood pressure and often will slow down the progression of kidney disease. However, controlling blood pressure will not always prevent the development of kidney failure requiring dialysis.

High blood pressure and dialysis

Most patients are on blood pressure lowering medications when they first start dialysis for kidney failure. However, many of them also have excess fluid in their bodies, so blood pressure may improve once a patient starts regular dialysis. Nonetheless, approximately 60 percent of hemodialysis patients and 30 percent of patients on peritoneal dialysis (PD) still have high blood pressure that requires medicines.

In hemodialysis, patients usually get treatments three times per week. Typically, the weight and the excess fluid in the patient’s body go up before dialysis, and down after dialysis. As you might expect, the blood pressure also tends to be highest in the hours before a hemodialysis treatment and lowest afterwards. In fact, symptoms of low blood pressure are common after hemodialysis treatments. These symptoms include cramping, nausea, dizziness and light-headedness. It is interesting to note that high blood pressure is less common in hemodialysis patients who get daily treatments, such as those on home hemodialysis (HHD). A majority of these home hemodialysis patients who get more frequent dialysis have normal blood pressures and do not need to take blood pressure medicines.

High blood pressure and peritoneal dialysis

Peritoneal dialysis (PD) is a daily therapy, so it may not be surprising that only 30 percent of patients are estimated to require hypertension therapy. However, excess fluid in the body still plays a major role in causing the blood pressure to be high, and many peritoneal dialysis patients do not keep the fluid off as well as they should. Even in patients whose fluid is controlled perfectly, blood pressure medicines are often needed. These medicines are also sometimes given to patients on peritoneal dialysis even when their blood pressure is not high. Such medicines may help protect the patient’s heart and kidneys.

High blood pressure in peritoneal dialysis patients is defined as a blood pressure reading of greater than 140/90 – the same as patients without kidney disease. However, in comparison to the general population, it is not completely clear at what level a high blood pressure actually begins to increase a person’ risks of cardiovascular disease and premature death. In contrast, excessively low blood pressure may be potentially harmful to dialysis patients. There remains some confusion as to exactly what is an optimal blood pressure for patients on peritoneal dialysis, and it seems true that the optimal blood pressure may be different for some patients in comparison to others. Overall, for most people on peritoneal dialysis, the best blood pressure range is probably 110-140 (systolic) over 70-90 (diastolic).

Managing high blood pressure in peritoneal dialysis patients

Keeping the blood pressure in optimal range first requires that a person’s fluid be managed well. Too little fluid in the body may cause the blood pressure to be low, and can be associated with symptoms such as leg cramps, nausea and lightheadedness. Too much fluid may cause the blood pressure to be high, and can result in ankle or facial swelling, chest fullness or shortness of breath. It is often helpful for each patient to identify an ideal body weight to aim for each day. When the patient’s weight is high and blood pressure is up, there is probably too much fluid in the body. When the patient’s weight is down and the blood pressure is low, dehydration may exist with too little fluid. Achieving the proper weight and fluid status can usually be accomplished by adjusting the concentration of dextrose – a type of sugar – in PD dialysate exchanges under the supervision of a nephrologist and peritoneal dialysis nurse. Reducing your daily intake of salt and liquids are other important tools to help keep the fluid off and the blood pressure down.

Medicines for blood pressure in peritoneal dialysis patients

Medicines play an important role in controlling high blood pressure in peritoneal dialysis patients. Diuretics are often given if a peritoneal dialysis patient still makes urine, since they help to prevent fluid overload. Two other groups of blood pressure medications seem to be especially useful. Drugs known as ACE inhibitors and angiotensin receptor blockers are effective at controlling blood pressure. However, they also appear to reduce the risk of heart disease in many patients, and may also be effective at preserving residual kidney function. It is recommended by some kidney authorities that a drug from one of these two categories be used as the first choice (when tolerated) in peritoneal dialysis patients who require a blood pressure lowering medication.

Other medications may be required to lower blood pressure, and some of these also provide certain benefits besides blood pressure control. Table 1 shows several categories and some examples of each type of medication.

Table 1

Summary

Many patients on peritoneal dialysis have hypertension. Both high blood pressure and excessively low blood pressure can be dangerous and increase the risk of bad outcomes such as cardiovascular disease, stroke and premature death. Peritoneal dialysis is a daily treatment that may help keep blood pressure in an optimal range without additional medicines. Careful attention to fluid management and the proper use of appropriate medications usually will keep the blood pressure under good control.

About Mark Shapiro, M.D.

Dr. Shapiro is a nephrologist who practices in Escondido, CA. He did his undergraduate training at University of California, Los Angeles, obtained his medical degree at the University of Pittsburgh, and completed his residency training and nephrology fellowship at the University of California, San Diego.

Dr. Shapiro is an Assistant Professor of Medicine at University of California, San Diego, but also maintains an active private nephrology practice in the San Diego area. His primary area of medical interest is in peritoneal dialysis (PD). Dr. Shapiro was a medical advisor for PD within Gambro Healthcare, Inc., but more recently was named the national peritoneal dialysis medical advisor within ²ÝÝ®ÊÓƵ Inc. In addition, he serves on the Physician Advisory Council and the Pharmacy and Therapeutics Committee within ²ÝÝ®ÊÓƵ.

Dr. Shapiro is married and has two sons. He enjoys kayaking, fishing and most other outdoor sports.