The loss of kidney function is accompanied by numerous changes impacting health, nutrition, and quality of life. One significant challenge for people
on dialysis is the loss of the ability to excrete fluid via the urine, resulting in fluid retention and associated complications. While fluid balance is itself
an important goal for this population (and a challenge for the interdisciplinary team supporting people on dialysis), fluid balance also has implications
for assessment and management of nutritional status.

The concept of dry weight or target weight is an important one in dialysis. Dry weight is defined as body weight free from excess fluid.
The term target weight is often used synonymously with dry weight, using more common language that may be easier for patients to understand.
Dry weight is typically assessed after dialysis and includes assessment of symptoms. In practice, this means freedom from symptoms of:

  • Hypovolemia and hypotension
  • Cramps
  • Dizziness
  • Nausea

At dry weight, a patient should also be free from edema, hypertension, or shortness of breath.

Frequent monitoring and adjustment of target weight is necessary to achieve optimal dialysis outcomes. Assessment of dry weight
is also critical in the nutrition assessment of people on dialysis. Fluid imbalances can obscure the true status of both visceral and somatic proteins,
leading to erroneous nutrition assessment and inappropriate interventions.

Albumin
There are multiple interactions between fluid and albumin that are relevant to nutrition assessment and intervention. In addition to albumin’s role
in fluid dynamics, the hemodilution associated with fluid accumulation may artificially lower serum albumin levels.
Collaborating with the interdisciplinary team to assess and adjust dry weight can provide a truer picture of a patient’s visceral protein status,
helping to guide which nutrition-related interventions are most appropriate.

Body Weight
Without assessment and adjustment of dry weight, fluid retention may obscure changes in dry body weight (lean muscle or adipose tissue.
Dry weights that are not assessed and/or adjusted, particularly following a health care event or change in the patient’s condition, may result in missed weight loss and therefore missed opportunities for the most appropriate nutrition interventions.

Becoming a Dry Weight Detective
In assessing body weight and protein status, registered dietitians caring for people on dialysis should always consider fluid volume status.
Effective dry weight detectives include physical assessment (Subjective Global Assessment), oral intake assessment (3 day food record or 24 hour recall), laboratory data, and patient history in their assessments. Collaboration with the interdisciplinary team in gathering relevant data related
to dialysis treatments, medications, and medical conditions is also important. Key findings that may indicate a patient is not at their true dry weight include:

  • Presence of edema (lower extremities, face, upper extremities, trunk)
  • Evidence of muscle wasting or fat loss on nutrition physical assessment (when target weight is unchanged)
  • Shortness of breath
  • Low serum sodium (<136 mEq/L)
  • Hypertension (new onset or worsening)
  • Missed or shortened dialysis treatments
  • Pre-dialysis weight below or only slightly above established target weight
  • Post-dialysis weight above established target weight

In addition to physical assessment, dialysis treatment course, and laboratory findings, it’s important to obtain a thorough history from the patient.
Some helpful questions to ask include:

  • Have there been changes in your appetite or food intake?
  • Have you noticed that your clothes fit differently?
  • Are you able to lie flat when resting or sleeping?
  • Are you able to do your usual activities without feeling winded?
  • Do you have the strength and energy to do your usual activities?
  • Do you feel heavy or notice extra fluid in your body?

While dry weight/target weight should be evaluated or trended monthly, it is particularly important to evaluate weight after a change
in the patient’s condition. Examples of key assessment periods include:

  • The first 30 to 90 days on dialysis
  • Following hospitalization
  • At the onset of a new comorbidity, particularly one with metabolic or gastrointestinal impacts
  • Following a surgical procedure (especially an amputation!)

Case Example
Mrs. Jones returns to the hemodialysis center after a week-long hospitalization related to an infected fistula. Her target weight prior to hospitalization
was 52 kg, and she typically gained 2 kg between dialysis treatments. Upon her return, her pre-treatment weight at dialysis was 53.5, and her blood pressure was a little higher than usual at 143/82. This did not alarm the team, as she had been through a stressful event. Assessment for edema while she was reclining found none. She voiced no complaints during treatment. She stayed covered with her blanket during dialysis that first week back,
getting some rest, since she still wasn’t feeling 100%. The team was glad to have her back and let her rest during treatment.

The second week after her hospitalization, Mrs. Jones arrived at dialysis and asked for wheelchair transport from her car, saying she felt weak
and wasn’t breathing that well. Her pre-dialysis weight was 53 kg, just one kg above her target weight. Monthly labs were drawn, showing a sodium level
of 132 mEq/L and albumin of 2.9 g/dL. After her treatment was initiated, the dietitian visited her to review monthly labs and to complete an informal assessment following her hospitalization. In talking with Mrs. Jones, the dietitian identified that Mrs. Jones’s appetite was still not back to normal
and that she was worried about having to buy new clothes, as her pants were not staying up. The dietitian asked Mrs. Jones for permission to complete
a physical assessment, which revealed edema in the lower extremities and face along with evidence of muscle wasting in her legs.

The dietitian noticed that Mrs. Jones’s fluid removal goal was set at 1 kg (so that she would reach her target weight of 52 kg) and decided to talk
to the patient care technician. She shared her findings with the technician and asked if he had observed other potential signs of fluid overload.
He mentioned that Mrs. Jones’s blood pressure had been trending upward during dialysis and that she wanted to sit upright more than usual.
The dietitian consulted the social worker, who shared that the patient was having difficulties completing activities of daily living due to feeling weak
and easily fatigued. The dietitian also spoke with the nurse, sharing her findings and her suspicions that the patient may be retaining fluid.
The nurse performed a more thorough assessment for edema (including in a sitting position) and listened to the patient’s lungs. Armed with the data obtained from her assessment and the interdisciplinary team, the nurse contacted Mrs. Jones’s nephrologist to recommend decreasing her target weight.

Following the nephrologist’s orders, the team gradually challenged Mrs. Jones’s target weight until she reached 45.5 kg. At this post-dialysis weight,
her blood pressure was 130/72, there were no signs of edema, and she was comfortable to recline during treatment. Her repeat labs showed a serum sodium of 138 mEq/L and albumin of 3.2 g/dL. Working together, the interdisciplinary team put together the full picture and concluded that Mrs. Jones
had lost weight during her illness and hospitalization and that this weight loss was obscured by fluid retention. The dietitian was able to refine her plan
of care to include escalating interventions to address the (true) hypoalbuminemia and significant weight loss, and the team prevented Mrs. Jones
from being hospitalized again related to complications of fluid overload.

References

  • Agarwal R, Weir MR. Dry-weight: a concept revisited in an effort to avoid medication-directed approaches for blood pressure control in hemodialysis patients. Clin J Am Soc Nephrol. 2010 Jul;5(7):1255-60. doi: 10.2215/CJN.01760210. Epub 2010 May 27. PMID: 20507951; PMCID: PMC2893058.
  • McCann L. Pocket Guide to Nutrition Assessment of the Patient with Kidney Disease (6th Ed.) National Kidney Foundation, 2021.

We thank our guest blogger, Rory C. Pace, MPH, RD, CSR, FAND, FNKF Nutrition Therapy Consultant, for sharing his knowledge and insights
in this important blog post!