**3.3.2 Body composition monitoring in living-donor transplant recipients**

We prospectively studied five transplanted patients who had received a living-donor graft after a period of hemodialysis. These five patients had exhibited particularly rapid recovery of normal renal function after transplantation. We took bioimpedance measures before surgery and several times during a mean 2-months period after transplantation. Our findings produced a bell-shaped curve showing weight gain with increasing over-hydration followed by weight loss with normo-hydration, in correlation with the normalization of kidney graft function (Table 3).


Table 3. Over-hydration after kidney transplantation

Clinically, the patients' blood pressure improved and edema disappeared. For example, one patient weighed 48.4 kg on day 4 post-transplantation and 47.3 kg on day 10. There was a reduction of the hyperhydration, the Cole-Cole curves shifting to the right (Fig. 11), and an increase in maximal reactance (X) (from 50.6 to 62.5 Ohm). The frequency at which this reactance reached its maximum also declined from 60 kHz to 50 kHz, a frequency which is commonly observed in normo-hydration subjects.

n° 8 who had a pacemaker, fluid removal seemed to occur exclusively from the intracellular

patient 1 0,1 *0,49* -1,77 *0,55*  patient 2 1,7 *0,21* 0,72 *0,13*  patient 3 0,78 *0,11* 0,53 *0,21*  patient 4 0,98 *0,29* -0,17 *0,12*  patient 5 0,72 *0,33* -0,1 *0,39*  patient 6 2,6 *0,71* 0,57 *0,15*  patient 7 0,62 *0,63* -0,15 *0,77*  patient 8 0,5 *1,59* 1,63 *0,8*  patient 9 0,84 *0,65* -0,2 *0,26*  patient 10 -0,6 *0,12* -0,97 *0,21* 

Table 2. Body composition monitoring (BCM) diagnosis of over-hydration (OH) status

**3.3.2 Body composition monitoring in living-donor transplant recipients** 

The over-hydration data presented in Table 2 show that, according to the BCM findings, all patients except two (n° 8 and 10), were over-hydrated at dialysis onset and underhydrated at dialysis end. Comparing the clinical diagnosis of over-hydration established by the nephrologist programming the ultrafiltration at the beginning of the session (Table 1) with the over-hydration status diagnosis established by BCM before dialysis (Table 2) revealed different trends. The nephrologist tended to overestimate over-hydration before dialysis while the BCM tended towards an underestimation. At the end of the ultrafiltration six of the patients were dehydrated, but not far from their dry weight, with a difference of ≤0.5

We prospectively studied five transplanted patients who had received a living-donor graft after a period of hemodialysis. These five patients had exhibited particularly rapid recovery of normal renal function after transplantation. We took bioimpedance measures before surgery and several times during a mean 2-months period after transplantation. Our findings produced a bell-shaped curve showing weight gain with increasing over-hydration followed by weight loss with normo-hydration, in correlation with the normalization of

BCM diagnosis Day 1 post-transplantation Day 50 post-transplantation

Over-hydration 1.04±0.7 liters 0.56±0.3 liters

Clinically, the patients' blood pressure improved and edema disappeared. For example, one patient weighed 48.4 kg on day 4 post-transplantation and 47.3 kg on day 10. There was a reduction of the hyperhydration, the Cole-Cole curves shifting to the right (Fig. 11), and an increase in maximal reactance (X) (from 50.6 to 62.5 Ohm). The frequency at which this reactance reached its maximum also declined from 60 kHz to 50 kHz, a frequency which is

**OH before (l) OH after (l) mean** *SD* **mean** *SD* 

compartment.

liters from normo-hydration.

kidney graft function (Table 3).

Table 3. Over-hydration after kidney transplantation

commonly observed in normo-hydration subjects.

Fig. 11. Cole-Cole time curves after kidney transplantation. In blue at Day 4 post transplantation (OH +0.5), in red at Day 10 post transplantation (OH +0.6)

#### **3.3.3 Body composition monitoring in acute kidney failure**

We studied three patients with acute reversible kidney disease. Body composition monitoring was started at the time of the acute disease and continued to the recovery period. Results (impedance, reactance, phase shift, Cole-Cole curve) showed an overhydration period that disappeared with the normalization of kidney function. The time course of improved hydration status in this patient is represented in Figure 12. Overhydration and weight variations followed the same pattern, rising and declining in parallel.

Fig. 12. Hydration status time course in a patient recovering normal kidney function.

Bioimpedance Measurement in the Kidney Disease Patient 181

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Table 4. Resistance and frequency values at maximal reactance

Fig. 13. Cole-Cole curves with recovery of kidney function from Day 1 (blue) to Day 11 (red)

Figure 13 also shows that the Cole-Cole curves shifted to the right as hydration status returned to normal. This right shift being the expression of lesser hyperhydration. On day 1, the resistance levels at 0 and ∞ frequency went from 450 to 370 Ohms with a maximum reactance of 26 for a resistance of 410. By day 11, the curves had shifted to the right, corresponding to lesser hyperhydration, weight loss, and a diagnosis of lower overhydration. These values ranged from 590 to 480 Ohms and maximal reactance of 37.7 with a corresponding resistance at 540 (Table 4). These physical elements also corresponded to clinical reality since blood pressure levels returned to normal with involution of lower limbs edema.

#### **4. Conclusion**

Bioimpedance is an easy-to-use tool providing a useful evaluation of patients' dry weight. The method remains limited due to the lack of standards of normality. Moreover, changes in electrolytes, red cells, protein, body temperature or implanted devices affect bioimpedance measures, further compromising use of bioimpedance for determining the dry weight or normal hydration level of hemodialysis patients. Nevertheless, measurable values such as impedance, reactance, or phase shift enable the identification of patient groups and the description of trends. Impedance, reactance and phase shift can be used to identify population groups with similar behavior patterns useful for determining dry weight or detecting hydration disorders. Analysis of correlations between physical data and clinical findings is another point of interest discussed in this chapter.

#### **5. References**

180 Technical Problems in Patients on Hemodialysis

Fig. 13. Cole-Cole curves with recovery of kidney function from Day 1 (blue) to Day 11 (red) Figure 13 also shows that the Cole-Cole curves shifted to the right as hydration status returned to normal. This right shift being the expression of lesser hyperhydration. On day 1, the resistance levels at 0 and ∞ frequency went from 450 to 370 Ohms with a maximum reactance of 26 for a resistance of 410. By day 11, the curves had shifted to the right, corresponding to lesser hyperhydration, weight loss, and a diagnosis of lower overhydration. These values ranged from 590 to 480 Ohms and maximal reactance of 37.7 with a corresponding resistance at 540 (Table 4). These physical elements also corresponded to clinical reality since blood pressure levels returned to normal with involution of lower

Bioimpedance is an easy-to-use tool providing a useful evaluation of patients' dry weight. The method remains limited due to the lack of standards of normality. Moreover, changes in electrolytes, red cells, protein, body temperature or implanted devices affect bioimpedance measures, further compromising use of bioimpedance for determining the dry weight or normal hydration level of hemodialysis patients. Nevertheless, measurable values such as impedance, reactance, or phase shift enable the identification of patient groups and the description of trends. Impedance, reactance and phase shift can be used to identify population groups with similar behavior patterns useful for determining dry weight or detecting hydration disorders. Analysis of correlations between physical data and clinical

findings is another point of interest discussed in this chapter.

 Day 1 Day 11 weight (kg) 86.2 82.3 Over-hydration (Kg) 2.8 0.2 Maximal reactance 25 37.7 Resistance (Ohm) 410 540 Frequency (kHz) 67 5O

Table 4. Resistance and frequency values at maximal reactance

limbs edema.

**4. Conclusion** 


Bioimpedance Measurement in the Kidney Disease Patient 183

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**11** 

*United Kingdom* 

**Management of Fluid Status** 

**The Roles of Technology and Dietary Advice** 

*Department of Renal Medicine, Leeds Teaching Hospitals NHS Trust* 

Elizabeth Lindley, Lynne Aspinall, Claire Gardiner and Elizabeth Garthwaite

The kidneys play a vital role in maintaining normal tissue hydration and serum sodium level. In haemodialysis patients, with impaired or absent kidney function, fluid status is managed by removing excess fluid using ultrafiltration and by restricting dietary sodium intake. Ideally, haemodialysis patients should remain close to normal hydration throughout the interdialytic period, with minimal periods of excessive dehydration or fluid overload

Optimal fluid management is achieved by adjusting the post-dialysis 'target' weight and, where necessary, limiting the fluid gained between dialysis sessions. While clinical history and examination remain the basis for prescribing the target weight, technology can provide useful objective information especially where the clinical indications are ambiguous. A simple non-invasive test can now be carried out when a patient attends for dialysis enabling staff to pick up changes in body composition so that their target weight can be adjusted to

In most patients, interdialytic fluid gain (IDFG) is directly related to sodium intake. Acceptable fluid gains can usually be achieved by limiting salt intake to the recommended daily allowance for the general population and avoiding unnecessary sodium loading during dialysis. Low pre-dialysis serum sodium levels can help identify patients with other causes of high IDFG, such as high blood sugar or social drinking, who need additional counselling. For the patients, lowering sodium intake may also improve blood pressure control and reduce requirements for antihypertensive medication. Staff education, and preferably participation, is vital when implementing salt restriction in a

A typical definition found on patient-focussed websites is 'the weight your doctor thinks you would be when all the extra fluid is removed from your body'(DaVita, n.d.). This actually defines the 'normally hydrated' weight which is a very useful concept but not

**1. Introduction** 

and with no fluid–related co-morbidity.

**2. Optimisation of the target weight 2.1 What is meant by target weight?** 

necessarily the weight the patient should achieve post-dialysis.

maintain optimal fluid status.

haemodialysis unit.

**in Haemodialysis Patients:** 

