1Department of Nephrology School of Clinical Medical Sciences University of Newcastle upon Tyne, UK 2Renal Research Institute NY, USA Email: Nicholas.hoenich{at}ncl.ac.uk
Sir,
Dr Dorhout Mees makes an important point relating to our recent review in respect of the clinical application of bioimpedance to determine dry weight in patients receiving haemodialysis. Haemodialysis fails to achieve full rehabilitation and the quality of life of dialysis patients remains suboptimal [1,2]. Dialysis patients have a high incidence of left ventricular hypertrophy, caused in part by hyper-tension. Excess extracellular fluid or hypervolaemia being a contributory factor [3], resolution leads to improved cardiac outcomes [4].
The ability to control hypervolaemia in patients is a function of its recognition, coupled with strategies to remove excess fluid and the control of fluid intake. Identification of hypervolaemia, particularly in patients who have latent overhydration or in whom there are no physical signs indicating fluid overload, is difficult. Bioimpedance is a diagnostic tool. It cannot be used in isolation and must be used with other measures, such as patient education to control sodium intake and treatment duration. The intake of sodium has long been a key element of dietary restriction for patients. The majority of patients do not add salt to their food, but many, if not most, are unaware of the hidden salt content of processed food. Historically, long 810 h treatment sessions were used. This approach provided good control of the blood pressure and continues to be used in some centres; however, the majority of patients are treated for <12 h weekly. An important driving force for such an approach is that it is a cost effective method of utilizing existing infrastructure in an era of financial constraint and it is favoured by patients. It may be unwise to conclude that it is impossible to reach the desired goal of dry weight with short dialysis schedules. Measures to reduce interdialytic weight gain by salt restriction, the alignment of dialysis fluid sodium and the gradual reduction in estimated dry weight over time as monitored by BIA could be useful in some patients. Clinical trials to investigate such an approach are currently under way.
It is true that clinical judgement is essential, but can any form of clinical examination establish the dry weight of the patient? Measures such as jugular venous pressure measurement, cardiac and pulmonary examination or the search for peripheral oedema are helpful in identification of fluid overload. These measures, however, lack the ability to detect the relatively small degree of extracellular fluid overhydration that may be present or provide a value of the patients dry weight.
The availability and clinical application of technology such as bioimpedance is a step in the right direction to ensure that the long-term pathophysiological consequences of intermittent treatment remain controlled. Such control will inevitably result in improved hypertensive control, reduction in cardiac mortality and an improved quality of life.
It is our view that the use of technology is an essential element of improving clinical practice, but concur with Dr Dorhout Mees that it will need to be used in association with other measures for optimum results.
Conflict of interest statement. None declared.
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