Dialysis is a medical treatment that takes over the function of failing kidneys, filtering waste products and excess fluid from the blood. When kidneys no longer work effectively, the body cannot remove enough fluid, leading to accumulation. A primary goal of dialysis is to manage fluid levels to prevent serious health complications.
Why Fluid Removal is Necessary
Kidneys normally regulate the body’s fluid balance by producing urine to excrete excess water and waste. When kidney function declines, this ability is lost, causing fluid to build up, a condition known as fluid overload or hypervolemia. This excess fluid can manifest as noticeable swelling (edema) in the face, hands, feet, and ankles.
Fluid overload also places considerable strain on the cardiovascular system. The increased fluid volume can elevate blood pressure, forcing the heart to work harder. This sustained stress can weaken the heart muscle, potentially leading to heart failure. Additionally, excess fluid can accumulate in the lungs, causing shortness of breath and making breathing difficult.
The Concept of Dry Weight
“Dry weight” refers to the ideal body weight a dialysis patient should achieve after fluid removal, where there is no excess fluid without experiencing symptoms of dehydration. This weight is the target for fluid removal during each dialysis session. It is the lowest weight a patient can safely reach post-dialysis while maintaining normal blood pressure and without experiencing discomfort.
Determining dry weight involves a thorough clinical assessment by the medical team. This includes evaluating the patient’s blood pressure, checking for the absence of swelling, and assessing for signs like distended neck veins or fluid in the lungs. Patient symptoms, such as shortness of breath, also contribute to this determination. Dry weight is largely an estimated target that can change over time rather than a fixed number.
How Fluid Removal is Adjusted During Dialysis
Fluid removal during dialysis is a dynamic process, continuously monitored and adjusted by the healthcare team. The amount of fluid to be removed is initially based on the patient’s weight gain since their last treatment. Factors influencing adjustments include the patient’s interdialytic weight gain (fluid accumulated between sessions) and real-time indicators like blood pressure and heart rate during the session.
If fluid is removed too quickly or in excessive amounts, patients might experience symptoms like a sudden drop in blood pressure, muscle cramps, or dizziness. The ultrafiltration rate (UFR), or the speed at which fluid is removed, is adjusted to prevent discomfort and complications.
Recognizing Fluid Imbalance
Recognizing the signs of fluid imbalance is important for dialysis patients. If too much fluid is removed during a session, patients may experience symptoms related to dehydration. These can include a sudden drop in blood pressure, dizziness, lightheadedness, severe muscle cramping, nausea, a rapid heartbeat, unusual weakness, or excessive thirst.
Conversely, if too little fluid is removed, symptoms of fluid overload can persist or worsen. These signs include continued swelling in the legs, feet, hands, or face, persistent shortness of breath, and high blood pressure. Patients should report any of these symptoms to their healthcare team to allow for adjustments in their dialysis plan.