Round-the-clock monitoring of blood pressure can be a useful clinical biomarker in predicting the outcome of patients suffering from non-dialysis chronic kidney disease (CKD) as reported in the June 27 issue of Archives of Internal Medicine. The report claimed that Ambulatory BP Monitoring can indicate prognosis of patients with CKD by predicting their likelihood of developing end stage renal disease or cardiovascular events requiring hospitalization and even death.
Automatic blood pressure readings at pre-specified intervals (usually every 15 to 20 minutes) within the 24 hour cycle can be recorded by the use of an ambulatory blood pressure monitor (ABPM). ABPM, a machine of the size of a portable radio can be easily worn by the patient underneath their clothing and the data recorded can be presented to the doctor for analyses. ‘White coat hypertension,’ is a phenomenon (highly prevalent in CKD) in which patients experience an artificial increase in BP only at the physician’s office. ABPM can be a valuable tool in preventing such false high readings to estimate prognosis and therapeutic regimens. Further, evidence is available to suggest that the BP recorded during the night may be a better measure of actual BP status as the person is away from physical, emotional or any other stress. This nocturnal BP recording may be a better predictor of a person’s cardiovascular risk.
A study of patients with CKD conducted by Roberto Minutolo, M.D., Ph.D., from the Second University of Naples in Italy, and his colleagues, at four Italian nephrology clinics has suggested that ABPM may be a more useful tool than office BP measurements in assessing the risk of end stage renal disease, cardiovascular events or mortality for patients suffering from CKD.
This study enrolled a total of 436 participants between 2003 and 2005. All study participants were provided with diaries to record their daily activities and were fitted with an ABPM to automatically collect BP readings every 15 minutes during day the and every 30 minutes during the night. Three blood pressure readings were recorded at the nephrology clinic the next day.
Over a median follow up period of 4.2 years, 86 patients developed end stage renal failure and 69 succumbed to the illness. A total of 115 cardiovascular events were observed in the study of which 52 were fatal events. The results of the study indicated that study participants who either had a daytime systolic blood pressure (SBP) of ≥ 135 mm Hg (milligrams of mercury), night time SBP ≥ 124 mm HG, or those in the highest quintile of diastolic blood pressure (DBP), were at the highest risk of both renal and cardiovascular outcomes.
The authors also reported that a nighttime DBP of ≥ 70 mm Hg was a predictor of cardiovascular events and end-stage renal disease. A significant finding of the study was that neither the diastolic nor the systolic blood pressure recordings made during regular clinic visits predicted renal or cardiovascular events.
The study clearly revealed the predictive value of ABPM in assessing the risk of cardiovascular or renal events in patients with CKD and its independence from other determinant or prognostic indicators. This study has also raised concerns regarding the relevance of hypertension guidelines in the management of CKD patients which are based more on expert opinion and post hoc analysis rather than randomized controlled trials.
The authors concluded by highlighting an urgent need for intervention studies based on ABPM rather than office BP measurements in the high risk chronic kidney disease patients.
Blood pressure is a major prognostic indicator in patients with CKD and needs regular monitoring. Cardiovascular morbidity increases with progressive deterioration in renal function, as stated by David Goldsmith, F.R.C.P of the King’s Health Partners AHSC in London, England, and Adrian Covic, M.D., Ph.D., F.R.C.P.(Lond), F.A.S.N., of C.I. Parhon University Hospital in Iasi, Romania. For the 13 percent US nationals having CKD, a regular monitoring of blood pressure can make a difference in long term survival rate and quality of life. Cardiovascular homeostasis is equally important at the time of dialysis, which can have fatal consequences.
As was proven in a recent study by Minutolo et al., Ambulatory BP Monitoring is considered an evidence based practice in the management of patients with CKD. This study also demonstrated a white coat hypertension of 43.3%, thereby supporting the fact that BP should be recorded in an ambulatory setting. For a better patient care of selected cohorts, Goldsmith and Covic acknowledge the usefulness of extra efforts and expenditure put into regular AMBP monitoring. They further state that the study conducted by Minutolo et al. supports the hypothesis and that a complete reliance on blood pressure measurement at a nephrology clinic may not suffice for targeted BP intervention. However, the benefits of ABPM need to be further demonstrated in a larger prospective randomized controlled trial.