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Saudi Journal of Kidney Diseases and Transplantation
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Year : 1999  |  Volume : 10  |  Issue : 3  |  Page : 283-285
Hypertension in the Hemodialysis Population - How little do we know?


Assistant Professor of Medicine, University of Mississippi Medical Center, Jakson, Mississippi, USA

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How to cite this article:
Salem M. Hypertension in the Hemodialysis Population - How little do we know?. Saudi J Kidney Dis Transpl 1999;10:283-5

How to cite this URL:
Salem M. Hypertension in the Hemodialysis Population - How little do we know?. Saudi J Kidney Dis Transpl [serial online] 1999 [cited 2020 Aug 4];10:283-5. Available from: http://www.sjkdt.org/text.asp?1999/10/3/283/37236
Hypertension is ubiquitous in renal disease. Indeed, renal disease is the commonest cause of secondary hypertension. When patients reach end-stage renal disease, over 90% of them are hypertensive. [1] Classical teaching holds that as dialysis is initiated and both uremia and excess volume are corrected, the blood pressure returns to normal. This concept was challenged in recent years by several cross-sectional studies showing a high prevalence of hypertension in the dialysis population. In 1995, we [2] published a survey of hypertension in a group of 649 patients. These patients were on dialysis for a mean of four and half years and 72% of them were still hypertensive (defined as predialysis blood pressure above 160/90). This high prevalence existed despite widespread use of antihypertensives in 60% of the patients. Younger age was the only significant factor associated with high blood pressure. Volume parameters, including the interdialytic weight gain and excess weight above dry weight did not correlate with the blood pressure. This study was confirmed in several consequent surveys from both the United States and Europe. Similar high prevalence of uncontrolled hypertension was found in the peritoneal dialysis population. The amount of dialysis delivered and the type of membrane used did not seem to affect level of the blood pressure. It thus became clear that the problem of hypertension in the dialysis patients is not amenable to our current modes of therapy. In a further prospective analysis, [3] we followed the same original group of 649 patients for one year to determine the effect of hypertension on survival. Surprisingly, we found out that the hypertensive patients had a smaller risk of dying at one year than the normotensive ones. These results hold true at two years analysis. They were also true after adjusting for the known variables influencing survival including age, diabetes mellitus, serum albumin and the quantity of dialysis. Our results were confirmed in two large studies from Zager et al [4] and the United States Renal Data System. Zager et al showed no adverse effect of increased blood pressure on survival. Those with hyper­tension as a cause of their end stage renal disease had a relative risk of 0.86. There was a one percent decrease in risk of death for each 1 mmHg increase in the pre­dialysis mean arterial pressure. Even more interesting was the gradual continuous decline in mortality as blood pressure rose from "optimal levels" to very "high levels", according to the classification of the Fifth Joint National Committee Report on Detection, Evaluation, and Treatment of High Blood Pressure (JNCV). [5] The lack of association between blood pressure and mortality may also reflect the overall poor prognosis of the dialysis population in the USA. If you only have an average life expectancy of five years, smoking and drinking, and for that matter, high blood pressure is unlikely to kill you. This may explain the observation that, in a cohort of well-dialyzed patients from France where the annual death rate was low and life expectancy was high, only those patients with normotension were long-term survivors. Another possibility is that malnourished older patients have lower blood pressure. The Cox proportional hazard may be inadequate to correct for these factors. Are patients with low blood pressure overmedicated? Are we simply seeing the effect of iatrogenesis rather than a true medical condition? However, the morbidity of the hypertensive dialysis patients, including strokes and heart disease, was increased. The issue of morbidity of hypertension in the hemodialysis population is worthy of more consideration. Unfortunately, there is little or no data on the subject with few exceptions (e.g. Foley et al [6] in Canada). The contribution of the hypertension to cerebrovascular accidents was documented in Japan [7] and the USA. Thus the issue is not whether to treat hypertension or not, but to what extent should the blood pressure be controlled in this population. It appears that a happy intermediate blood pressure is required in the dialysis patient and that aggressive lowering of the blood pressure is probably harmful. Since these patients have an average age of 64 years and have underlying atherosclerosis, a blood pressure no less than 160/90 may be required for adequate tissue perfusion.

The mechanisms of hypertension in the dialysis patients have been the subject of intensive study in the early days of dialysis. Volume appears to play a predominant role and the renin/angiotensin axis plays a minor role. Addressing both factors may lead to better blood pressure control. We have to remember that removal of fluid during the dialysis procedure is often associated with compensatory activation of the sympathetic and renin/angiotensin mechanism. From the above discussion, the ideal antihypertensives in this population should be a combination of a beta blocker plus an angiotensin converting enzyme inhibitor. Unfortunately, there are no prospective studies in this population on the selective benefit of one antihypertensive versus another. The nephrologist will have to continue to use an empiric approach in dealing with this problem.

 
   References Top

1.Thomson GE, Waterhouse K, McDonald HP Jr, Friedman EA. Hemodialysis for chronic renal failure. Arch Intern Med 1967; 120: 153-67.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Salem MM. Hypertension in the hemodialysis population; a survey of 649 patients. Am J Kidney Dis 1995;26:461-8.   Back to cited text no. 2  [PUBMED]  
3.Salem MM, Bower J. Hypertension in the hemodialysis population: any relation to one-year survival? Am J Kid Dis 1996;28:737-40  Back to cited text no. 3  [PUBMED]  
4.Zager PG, Nikolic J, Brown RH, et al. "U" curve association of blood pressure and mortality in hemodialysis patients. Medical Directors of Dialysis clinic, Inc. Kidney Int 1998;54(2):561-9.  Back to cited text no. 4    
5.The fifth report of the Joint National 7. Committee on Detection, Evaluation and Treatment of High Blood Pressure (JNC V). Arch Intern Med 1993; 153:154-83.  Back to cited text no. 5    
6.Foley RN, Parfrey PS, Harnett JD, Kent GM, Murray DC, Barre PC. Impact of hypertension of cardiomyopathy, morbid­dity and mortality in end-stage renal disease. Kidney Int 1996;49:1379-85.  Back to cited text no. 6    
7.Iseki K, Miyasato F, Tokuyama K, et al. Low diastolic blood pressure, hypoalbuminemia, and risk of death in a cohort of chronic hemodialysis patients. Kidney Int 1997;51:1212-7.  Back to cited text no. 7  [PUBMED]  

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Correspondence Address:
Mahmoud Salem
Assistant Professor of Medicine, University of Mississippi, Medical Center 2500 North State Street, Jackson, MS 39216
USA
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PMID: 18212438

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