DEFINITION / CLINICAL DETERMINATION
One of the greatest challenges for nephrologists caring for haemodialysis patients is assessing their extracellular fluid volume (Ishibe & Peixto, 2004); most nephrologists have used the concept of ‘dry weight’ to drive such decisions.
This complex investigation may result in the successful determination of the patients dry weight.
Different weight terms used in routine practice.
The pre dialysis weight (75 kg in this example) is unambiguous and obviously provides the starting point for treatment.
The normohydration weight represents the weight that would be achieved when the hydration of the patient reflects the normal hydration of body tissues that would be encountered in healthy controls with matched body composition. It is the weight obtained when zero excess fluid is present. The normohydration weight is a definition based on tissue hydration properties known from scientific analysis. It is synonymous with the clinical ideas of normovolaemia or euvolaemia or the concept of normal extracellular volume. It is essential to appreciate that although normohydration weight represents a possible target weight for a patient it does not necessarily mean that this weight can be achieved. Comorbidity and the use of antihypertensive agents are factors that influence the vascular stability of a patient during treatment.
Relative high ultrafiltration rates may lead to recurrent intradialytic symptoms. Hence, the patient may not reach the normohydration weight but the tolerated weight. In order to reach the individual dry weight of the patient, prolonged treatments and/or low ultrafiltration rates may be necessary.
Post dialysis weight
Is the weight of the patient after treatment.
It may be the normohydration weight, the tolerated weight, or clinical dry weight.