Answer. The blood pressure is the pressure inside the cardiovascular system. The readings are comprised of a systolic number (the top number) and a diastolic number (the bottom number). The systolic blood pressure reflects the pumping action of the heart and the ability of large blood vessels like the aorta to absorb the shock of the pump and the diastolic reflects the blood pressure when the heart is at rest. Thus, this diastolic number represents the resistance in the system. Blood vessel walls have muscles in their lining. If the muscles tighten, the vessels constrict and have a narrowed diameter. If the muscles relax, the diameter widens and the resistance and diastolic blood pressure fall. If the pressures are higher than normal, one may have hypertension. This hypertension may be secondary to kidney disease or may cause kidney disease.

It is estimated by the American Heart Association that one quarter of the population in the United States has hypertension. As many as one third are not aware that they have it. Hypertension not only leads to kidney disease (along with diabetes it is the most common cause) but also plays a role in congestive heart failure, stroke, atherosclerosis and blindness. A simple urine test for albumin helps determine the risk of developing adverse effects from hypertension. The Joint National Commission meets regularly to review the current literature on blood pressure and publishes guidelines. 

The National Kidney Foundation has developed a consensus statement on blood pressure and a set of guidelines to help prevent the progression of kidney disease. These guidelines are based upon several studies, a few of which are listed in the references below. Abnormal blood pressure is considered greater than 140/90 mm Hg. Optimal blood pressure may be 130/85 mm Hg and this should also be the goal for chronic kidney disease when proteinuria (the condition of protein leaking into the urine) is not significant. However, patients with kidney disease have been shown to require even lower blood pressures - with chronic kidney disease and proteinuria, the goal should be as low as 125/75 mm Hg to help preserve kidney function and protect the kidneys from further deterioration. 

Since hypertension is such a potent stimulus of heart failure and considering that the majority of patients who begin dialysis have some degree of heart failure, controlling blood pressure is a major part of the strategy to reduce heart disease in advanced kidney disease.

The strategy to control blood pressure is to use medications that will have additional benefits. Angiotensin is a hormone that constricts smooth muscles in the vessels of the kidney and in other vessels as well. Two classes of medication can block this hormone: angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs). Both classes have been shown to help reduce the progression of kidney disease, particularly in diabetics. Also, since the target blood pressure required to help protect the kidney is often lower than one can achieve with one medication, several additional medications may be required. Calcium channel blockers are also useful but are generally recommended for use once one is already on an ACE inhibitor or ARB.

Answer provided by Stephen Z. Fadem, MD, FACP. Dr. Fadem is a practicing nephrologist in Houston, TX. He also serves as a member of the AAKP Medical Advisory Board.

References

1. Bakris GL, Williams M, Dworkin L, Elliott WJ, Epstein M, Toto R, Tuttle K, Douglas J, Hsueh W, Sowers J. Preserving renal function in adults with hypertension and diabetes: a consensus approach. National Kidney Foundation Hypertension and Diabetes Executive Committees Working Group. Am J Kidney Dis.  2000 Sep;36(3):646-61.

2. Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure. The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI).

3. Brenner BM, Cooper ME, de Zeeuw D, Keane WF, Mitch WE, Parving HH, Remuzzi G, Snapinn SM, Zhang Z, Shahinfar S RENAAL Study Investigators Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. N Engl J Med.  2001 Sep 20;345(12):861-9. 

4. Effects of ramipril on cardiovascular and microvascular outcomes in people with diabetes mellitus: results of the HOPE study and MICRO-HOPE substudy. Heart Outcomes Prevention Evaluation Study Investigators. Lancet 2000 Jan 22;355(9200):253-9.

5. Estacio RO, Jeffers BW, Hiatt WR, Biggerstaff SL, Gifford N, Schrier RW.  The effect of nisoldipine as compared with enalapril on cardiovascular outcomes in patients with non-insulin-dependent diabetes and hypertension. N Engl J Med. 1998 Mar 5;338(10):645-52.

6. Hansson L, Zanchetti A, Carruthers SG, Dahlof B, Elmfeldt D, Julius S, Menard J, Rahn KH, Wedel H, Westerling S. Effects of intensive blood-pressure lowering and low-dose aspirin in patients with hypertension: principal results of the Hypertension Optimal Treatment (HOT) randomised trial. HOT Study Group. Lancet 1998 Jun 13;351(9118):1755-62.

7. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Kidney Disease Outcome Quality Initiative. Am J Kidney Dis. 2002 Feb;39(2 Suppl 2):S1-246.

8. Klag MJ, Whelton PK, Randall BL, Neaton JD, Brancati FL, Stamler J. End-stage renal disease in African-American and white men. 16-year MRFIT findings. JAMA. 1997 Apr 23-30;277(16):1293-8.

9. Lazarus JM, Bourgoignie JJ, Buckalew VM, Greene T, Levey AS, Milas NC, Paranandi L, Peterson JC, Porush JG, Rauch S, Soucie JM, Stollar C. Achievement and safety of a low blood pressure goal in chronic renal disease. The Modification of Diet in Renal Disease Study Group. Hypertension 1997 Feb;29(2):641-50.

10. Lewis EJ, Hunsicker LG, Clarke WR, Berl T, Pohl MA, Lewis JB, Ritz E, Atkins RC, Rohde R, Raz I. Collaborative Study Group. Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes. N Engl J Med  2001 Sep 20;345(12):851-60.

11. Pahor M, Psaty BM, Alderman MH, Applegate WB, Williamson JD, Furberg CD. Therapeutic benefits of ACE inhibitors and other antihypertensive drugs in patients with type 2 diabetes. Diabetes Care 2000 Jul;23(7):888-92.

12. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes: UKPDS 38. UK Prospective Diabetes Study Group. BMJ 1998 Sep 12;317(7160):703-13.

13. Tuomilehto J, Rastenyte D, Birkenhager WH, Thijs L, Antikainen R, Bulpitt CJ, Fletcher AE, Forette F, Goldhaber A, Palatini P, Sarti C, Fagard R. Effects of calcium-channel blockade in older patients with diabetes and systolic hypertension. Systolic Hypertension in Europe Trial Investigators. N Engl J Med. 1999 Mar 4;340(9):677-84.

14. Yusuf S, Sleight P, Pogue J, Bosch J, Davies R, Dagenais G. Effects of an angiotensin-converting-enzyme inhibitor, ramipril, on cardiovascular events in high-risk patients. The Heart Outcomes Prevention Evaluation Study Investigators. N Engl J Med. 2000 Jan 20;342(3):145-53.

The American Association of Kidney Patients presents Ask the Doctor, an opportunity for readers to submit kidney related health questions to healthcare professionals who specialize in an area of concern. The answers are not to be construed as a diagnosis and therefore, alterations in current healthcare should not occur until the patient’s physician is consulted.

This article originally appeared in the August 2002 issue of Kidney Beginnings: The Magazine, Vol. 1, No. 1.

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