Pre-dialysis blood pressure measurements misclassify hypertension in about 1/3 of hemodialysis patients
New NDT study shows that `normal´ pre-dialysis blood pressure measurement is not reliable. “Without performing extended ambulatory BP recordings (44h – 48h) we approvingly accept an error rate of about 30% in the diagnosis of hypertension in dialysis patients, a highly vulnerable patient group with a dramatically elevated cardiovascular risk. This is why EURECA-m recommends ambulatory blood pressure monitoring as gold standard for the diagnosis for hypertension in hemodialysis patient.”
There is a bidirectional relationship between high blood pressure and chronic kidney disease (CKD). Hypertension aggravates CKD progression. On the other hand, CKD can cause hypertension, because our kidneys do not only `detox´ our bodies, but also regulate the blood pressure. This is, why nephrologists are `core experts´ when it comes to uncontrolled or difficult-to-treat blood pressure.
In hemodialysis patients, hypertension is very common, because the kidneys – and with them the main blood pressure regulation mechanism – stopped working.
“High blood pressure is dangerous, also in dialysis patients. It can lead to severe complications like heart attacks and strokes”, explains Professor Carmine Zoccali, president of the ERA-EDTA. “The monitoring of blood pressure levels is therefore an essential part of the care of these patients. The European Cardiovascular and Renal Medicine (EURECA-m) recommends the 48-h ambulatory blood pressure monitoring (ABPM) in these patients. Our new data strongly support this recommendation.”
The EURECA-m working group has previously published a study, in which 396 hemodialysis patients underwent 48-h ABPM. It showed that the prevalence of hypertension in dialysis patient was very high (84.3%). Although similar rates have been seen when blood pressure levels were measured in the dialysis center before the dialysis treatment, the sensitivity and specificity of 48-h ABPM proved to be higher. Sensitivity means that patients with hypertension are reliably detected and specificity means that those who do not suffer from hypertension are also correctly identified. Obviously, the `normal´, pre-dialysis measurement does not have a sufficient sensitivity and specificity in dialysis patients. About 30% of the patients are misdiagnosed, when the blood pressure is measured in the dialysis center before each dialysis treatment.
Why is that the case? The new EURECA-m study showed that 18.2% of the patients suffered from “white coat hypertension”: They do not have hypertension in “real life”, but develop high blood pressure levels as soon as their blood pressure is measured by a doctor or nurse. Vice versa, 14.1% of the patients suffered from “masked hypertension”, in which high blood pressure values occur often during the nights, only. Therefore, this hypertension cannot be detected before the daily dialysis treatment. Only the 48-h ABPM can reliably detect a `masked hypertension´ as well as the `white coat hypertension´.
“If we do not perform a 48-h ABPM, there is the risk that we treat patients with `white coat hypertension´, who do not need any medication and that we do not treat those with a `masked hypertension´ or with nocturnal hypertension, who need the treatment. In short: Without performing extended ambulatory BP recordings (44h – 48h) we approvingly accept an error rate of about 30% in the diagnosis of hypertension in dialysis patients, a highly vulnerable patient group with a dramatically elevated cardiovascular risk”, explains Professor Zoccali, ERA-EDTA president and co-author of the new study. “This is why EURECA-m recommends 48-h ambulatory blood pressure monitoring as gold standard for the diagnosis for hypertension in hemodialysis patient.”