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Achieving blood pressure targets during dialysis improves control but increases intradialytic hypotension

2007; Elsevier BV; Volume: 73; Issue: 6 Linguagem: Inglês

10.1038/sj.ki.5002745

1523-1755

Andrew Davenport, Claire Cox, Raj Thuraisingham,

Dialysis and Renal Disease Management

Cardiovascular disease remains the most common cause of mortality in patients with end-stage kidney disease treated by regular hemodialysis. To improve blood pressure control and reduce cardiovascular risk, the United Kingdom Renal Association standards committee introduced pre- and post-dialysis target blood pressures of less than 140/90 and 130/80 mm Hg, respectively. We audited blood pressure control and symptomatic intradialytic hypotension requiring fluid resuscitation in the Greater London area renal centers that serve 2630 patients. The study captured 7890 hemodialysis sessions during a 1-week period where only 36% of the patients achieved the pre-dialysis target and 42% the post-dialysis target, with a wide variation between centers. Different antihypertensive medication prescriptions did not affect achievement of these targets. Fifteen percent of the patients suffered symptomatic hypotension requiring fluid resuscitation associated with significantly greater interdialytic weight gains. Our study found that intradialytic hypotension was significantly greater in centers that achieved better post-dialysis blood pressure targeting. Cardiovascular disease remains the most common cause of mortality in patients with end-stage kidney disease treated by regular hemodialysis. To improve blood pressure control and reduce cardiovascular risk, the United Kingdom Renal Association standards committee introduced pre- and post-dialysis target blood pressures of less than 140/90 and 130/80 mm Hg, respectively. We audited blood pressure control and symptomatic intradialytic hypotension requiring fluid resuscitation in the Greater London area renal centers that serve 2630 patients. The study captured 7890 hemodialysis sessions during a 1-week period where only 36% of the patients achieved the pre-dialysis target and 42% the post-dialysis target, with a wide variation between centers. Different antihypertensive medication prescriptions did not affect achievement of these targets. Fifteen percent of the patients suffered symptomatic hypotension requiring fluid resuscitation associated with significantly greater interdialytic weight gains. Our study found that intradialytic hypotension was significantly greater in centers that achieved better post-dialysis blood pressure targeting. In the general population, there is a strong association between hypertension and death and, in particular, increasing pulse pressure as a result of decreased conduit artery compliance.1.Blacher J. Asmar R. Djane S. et al.Aortic pulse wave velocity as a marker of cardiovascular risk in hypertensive patients.Hypertension. 1999; 33: 1111-1117Crossref PubMed Scopus (1205) Google Scholar The relative risk of hypertension for stroke and heart attack is greatest for younger subjects, although the absolute risk increases with age. In addition to stroke and heart attack, hypertension is also causally linked with heart failure and chronic kidney disease. A nonlinear association or 'J'-shaped curve has been reported between blood pressure and recurrent events in patients with previous myocardial infarction. Despite concerns that this increased risk may have been attributable to an adverse effect of treatment, it is now considered more likely to reflect the severity of disease on blood pressure—the larger the size of myocardial infarction, the greater the fall in blood pressure—rather than the effect of blood pressure or its treatment on the disease.2.Isles C.G. Prevalence, epidemiology, and pathophysiology of hypertension.in: Warrell D.A. Cox T.M. Firth J.D. Benz Jr., E.J. Oxford Textbook of Medicine. 4th edn. Oxford University Press, Oxford, UK2003: 1153-1160Google Scholar Hypertension has been defined by the US Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure3.Chobanian A.V. Bakris G.L. Black H.R. et al.Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.Hypertension. 2003; 42: 1206-1252Crossref PubMed Scopus (9729) Google Scholar (Table 1).Table 1JNC-VII classification of blood pressure in adults3.Chobanian A.V. Bakris G.L. Black H.R. et al.Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. National Heart, Lung, and Blood Institute; National High Blood Pressure Education Program Coordinating Committee. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.Hypertension. 2003; 42: 1206-1252Crossref PubMed Scopus (9729) Google ScholarCategorySystolic blood pressure (mm Hg)Diastolic blood pressure (mm Hg)Normal<120and 180 mm Hg.5.Kawamura T. Fijimoto S. Hisanga S. et al.Incidence, outcome and risk factors of cerebrovascular events in patients undergoing maintenance haemodialysis.Am J Kid Dis. 1998; 31: 991-996Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar In addition, post-mortem studies have shown that lacunar infarcts secondary to hypertension were the most common finding, even in patients without overt cerebrovascular disease.6.Kamata T. Hishida A. Takita T. et al.Morphological abnormalities in the brain of chronically haemodialysed patients without cerebrovascular disease.Am J Nephrol. 2000; 20: 27-31Crossref PubMed Scopus (50) Google Scholar In view of the risk of cardiovascular death in hemodialysis patients, blood pressure control has become a major target for intervention. As with the general population, there is a 'J'-shaped relationship with increased mortality in both those with the highest and lowest blood pressure.7.Port F.K. Hulbert-Shearon T.E. Wolfe R.A. et al.Predialysis blood pressure and mortality risk in a national sample of maintenance haemodialysis patients.Am J Kidney Dis. 1999; 33: 507-517Abstract Full Text Full Text PDF PubMed Google Scholar This may be the consequence of prolonged sustained hypertension, resulting in cardiac damage, and eventually cardiac failure, associated with a low blood pressure8.Mazzuchi N. Carbonell E. Fernandez-Cean J. Importance of blood pressure control in haemodialysis patient survival.Kidney Int. 2000; 58: 2147-2154Abstract Full Text Full Text PDF PubMed Google Scholar and increased mortality. Although there has been no adequately powered intervention to study the potential benefit of blood pressure control in hemodialysis patients, standards committees have introduced blood pressure targets for dialysis patients. In the United Kingdom, the Renal Association standards committee produced a document in 2002 that stated that hemodialysis patients with chronic kidney disease stage V should have pre- and post-dialysis blood pressures of <140/90 and <130/80 mm Hg, respectively.9.Renal Association Standards Treatment of Adults and Children with Renal Failure Standards and Audit Measures. 3rd edn,. 2002Google Scholar These targets were stricter than in the previous version, based on the absolute benefits of blood pressure control being greater in those patients with a high pulse pressure and non-compliant vasculature.10.Blacher J. Guerin A.P. Pannier B. et al.Impact of aortic stiffness on survival in end-stage renal disease.Circulation. 1999; 99: 2434-2439Crossref PubMed Scopus (1786) Google Scholar To determine whether these targets were achievable in clinical practice and also whether the lower pre-dialysis blood pressure targets resulted in increased intradialytic hypotension, we prospectively audited blood pressure in a cohort of thrice weekly chronic hemodialysis patients attending dialysis centers in the Greater London area. The first part of the audit was designed to assess how many patients achieved the UK Renal Association targets of pre- and post-dialysis blood pressures of <140/90 and <130/80 mm Hg, respectively. A total of 2630 patient pro formas were completed and returned for the audit, capturing 7890 hemodialysis sessions. The number of patients dialysing in the 11 centers ranged from 91 to 408, with median of 244 patients. The average pre-dialysis blood pressure recorded before the three dialysis sessions was 146.9±23.6/88.2±13.1 mm Hg. The pre-dialysis blood pressure standard was achieved in 36% of all patients. This varied between the 11 hospital centers, ranging from 28 to 57% (Figure 1). The average post-dialysis blood pressure was 134.5±28.2/72.3±12.8 mm Hg, and 42% of all patients achieved the post-dialysis standard of 0.1), or post-dialysis target, 20 vs 13%, respectively (χ2=0.43, P=0.5), and both targets, 11 vs 6%. In addition, there was no significant difference in achieving either the pre-dialysis blood pressure target, whether patients were prescribed antihypertensive medication, or not (Figure 3). There was no difference in the number of patients selected to be on the cadaveric renal transplant waiting list achieving either the pre-dialysis blood pressure target, 40% compared to 35% not on the waiting list, or the post-dialysis target, 45 vs 40%, respectively. There was no difference between ethnic groups in terms of achieving the UK Renal Association blood pressure targets, with 39% of Caucasian, 33% black, 33% Asian, and 33% of other races achieving the pre-dialysis standard, and 43% Caucasian, 41% black, 41% Asian, and 41% of other races achieving the post-dialysis target. Although more patients from ethnic minorities were prescribed antihypertensive medication, including 74% of blacks, 73% of Asians, 73% for other races, and 66% Caucasians, there was no statistical difference in blood pressure control between ethnic groups. There was a very weak correlation between interdialytic weight gain for all patients and pre-dialysis blood pressure, r=0.1, P<0.01, but not post-dialysis blood pressure. Similarly, there was a weak correlation between dialysate sodium concentration and pre-dialysis systolic blood pressure, r=0.032, P<0.05. There was a direct correlation between dialysate sodium concentration and interdialytic weight gain, r=0.137, P<0.01. However, there was an unexpected correlation between dialysate sodium concentration and the post-dialysis blood pressure, r=-0.56, P<0.01, and this may have been due to clinicians trying to sustain blood pressure in severely hypotensive patients by deliberately increasing the dialysate sodium. Hypotension during dialysis requiring intravenous fluid resuscitation was recorded in 7% of all hemodialysis sessions, which varied from 4 to 13% between centers. Overall, some 15% of patients experienced at least one hypotensive episode over the three dialysis sessions and 2% of patients suffered hypotensive episodes during each of the three dialysis sessions. The incidence of persistent clinically symptomatic intradialytic hypotension, requiring intravenous fluid resuscitation, varied from 0 to 4% between centers. There was a correlation between the percentage of patients achieving the post-dialysis blood pressure standard in a center and the percentage of symptomatic intradialytic hypotensive episodes requiring intravenous fluid resuscitation, r=0.81, P=0.003 (Figure 4), but there was no correlation between intradialytic hypotension and achievement of the pre-dialysis blood pressure target, r=-0.12, P=0.71. Patients were more likely to suffer clinically symptomatic hypotensive episodes requiring intravenous fluid resuscitation if they were not prescribed antihypertensives, 21% compared to 13% of those prescribed antihypertensives, (χ2=20.2, P<0.001). This apparent difference could have been potentially exaggerated, as patients prone to intradialytic hypotension prescribed antihypertensive medications may have been advised to withhold their antihypertensives before dialysis. The advice regarding taking prescribed antihypertensive medication varied from center to center, with 57% of patients advised not to take their medication before dialysis, but this advice varied from 0 to 100% between centers. Eleven percent of patients who omitted their antihypertensives before dialysis suffered one or more hypotensive episodes compared to 7% of those who took their medication (χ2=0.58, P=0.44). There was no significant difference between the incidence of recorded hypotensive episodes and drug prescription; 23.1% of patients prescribed α-blocker monotherapy, 15.6% calcium channel blockers, 20.7% β-blockers, and 16.9% prescribed ACEIs/ARBs (Figure 5). Patients who developed clinically symptomatic intradialytic hypotension requiring intravenous fluid resuscitation had greater median interdialytic weight gains as both absolute weight gain, 2.42 kg (1.8–3.0) vs 2.1 kg (1.3–2.8), P<0.01 and percentage increase compared to target dry weight, median 3.2% (2.4–4.3) vs 2.8% (1.8–3.9), P<0.0001. Those patients who suffered clinically symptomatic intradialytic hypotension had a lower pre-dialysis mean diastolic pressure, median 75 mm Hg (66–85) compared to those who did not, median 78 mm Hg (69–88), P<0.001. In addition, hypotensive-prone patients were also noted to have a lower pulse pressure, 64 mm Hg (50–81) vs 68 mm Hg (54–81), P 160/90 mm Hg,8.Mazzuchi N. Carbonell E. Fernandez-Cean J. Importance of blood pressure control in haemodialysis patient survival.Kidney Int. 2000; 58: 2147-2154Abstract Full Text Full Text PDF PubMed Google Scholar whereas other studies have reported increased mortality only when the systolic pressure is greater than 180 mm Hg.11.Zager P.G. Nikolic J. Brown R.H. et al.'U' curve association of blood pressure and mortality in hemodialysis patients. Medical Directors of Dialysis Clinic, Inc.Kidney Int. 1998; 54: 561-569Abstract Full Text Full Text PDF PubMed Scopus (560) Google Scholar A review of the US renal database reported that a low pre-dialysis systolic blood pressure was associated with increased risk of mortality, but there was no increased mortality risk with systolic hypertension, although there was an increased risk of stroke.7.Port F.K. Hulbert-Shearon T.E. Wolfe R.A. et al.Predialysis blood pressure and mortality risk in a national sample of maintenance haemodialysis patients.Am J Kidney Dis. 1999; 33: 507-517Abstract Full Text Full Text PDF PubMed Google Scholar Similarly, the Japanese renal registry does show an increased risk of cerebral hemorrhage in patients with both pre- and post-dialysis hypertension.5.Kawamura T. Fijimoto S. Hisanga S. et al.Incidence, outcome and risk factors of cerebrovascular events in patients undergoing maintenance haemodialysis.Am J Kid Dis. 1998; 31: 991-996Abstract Full Text Full Text PDF PubMed Scopus (141) Google Scholar However, post-dialysis systolic blood pressure has been associated with an elevated mortality risk both for low and high levels as compared with mid-range blood pressures.7.Port F.K. Hulbert-Shearon T.E. Wolfe R.A. et al.Predialysis blood pressure and mortality risk in a national sample of maintenance haemodialysis patients.Am J Kidney Dis. 1999; 33: 507-517Abstract Full Text Full Text PDF PubMed Google Scholar In this audit of 2630 established thrice weekly hemodialysis patients, only 36% achieved the UK Renal Association pre-dialysis blood pressure target of <140/90 mm Hg, 42% the post-dialysis standard of 90 days, in 13 main hospitals and 30 satellite dialysis units, located in the Greater London area. Patients dialysing for 90 days or less were excluded on the basis that they may still not have achieved their appropriate target weight, and similarly patients dialysing twice weekly or less were also excluded, as these patients may potentially have had significant residual renal function. Data were collected on 2628 chronic dialysis patients, 1180 main hospitals, and 1448 satellite dialysis patients. The majority of patients were male (60.5%) and Caucasian (49%), with 24% classified as from the Asian subcontinent and 23% black. The median age for the group was 61.2 years (interquartile range 46.9–72.3 years) but varied from 56.2 years (44.7–67.9) to 67.4 years (56.3–78.3). Overall, 32% of all patients were diabetic and this ranged from 21 to 37% between the 11 main renal units. However, 44% of Asian patients were diabetic, compared to 35% of blacks and 25% of Caucasian and other patients. The majority of patients dialysed with an arteriovenous fistula (60%) and 31% used tunneled central venous access catheters. All patients used bicarbonate dialysate and polysulfone membrane dialyzers; apart from two centers that used modified cellulose acetate, the modal dialysis time was 4 h. Dialysate sodium concentrations varied within centers, and most centers dialysed patients prone to hypotension with cooled dialysate. Blood pressure was routinely measured electronically in all units, although in 2% of cases a mercury sphygmomanometer was used. Blood pressure and weight were recorded pre- and post-dialysis in each of the three dialysis sessions. Intradialytic hypotension was defined as a sudden decrease in blood pressure that required intravenous fluid replacement to restore the blood pressure. Statistical analysis was by Student's t-test, Mann–Whitney U-test, χ2-test, and either Pearson's or Spearman's correlation analysis. Data are expressed as mean±s.d. or median and interquartile range. Statistical significance was taken at or below the 5% level. The authors state no conflict of interest. We thank all the local co-ordinators in the 11 main and 30 satellite dialysis centers, who collected and submitted the patient data. Pan Thames Renal Audit Group; Andrew Frankel—Charring Cross Hospital, Anthony Warrens—Hammersmith Hospital, Adam McLean—St Mary's Hospital, Michael Almond—Southend Hospital, Paul Donohoe—King's College Hospital, Cormac Breen—Guy's and St Thomas's Hospital, Jonathon Kwan—St Helier Hospital, Steven Nelson—St George's Hospital, Guy Neild—The Middlesex Hospital and Aroon Lal—Basildon Hospital.