Post-Dialysis Hypotension (PDH) is a frequent and serious complication of hemodialysis treatment. It is defined as a significant drop in blood pressure during or shortly after a dialysis session, often accompanied by symptoms such as dizziness, nausea, or fainting. This condition occurs because the rapid removal of excess fluid (ultrafiltration) overwhelms the body’s ability to compensate and replenish fluid volume in the bloodstream. The resulting reduction in blood volume can lead to inadequate blood flow to organs, requiring effective management to prevent long-term harm to the heart and other organs.
Immediate Non-Drug Interventions
When a patient experiences symptoms of low blood pressure during or immediately following dialysis, the initial response focuses on rapid, non-pharmacological stabilization. Staff must stop or drastically reduce the rate of ultrafiltration to prevent further volume loss from the blood.
Simultaneously, positional changes redirect blood flow toward the body’s core and brain. Elevating the patient’s legs while lowering their head (the Trendelenburg position) promotes venous return to the heart, increasing cardiac output and stabilizing blood pressure. Medical staff may also administer a rapid infusion of intravenous fluids, typically a bolus of normal or hypertonic saline, to quickly expand the plasma volume.
Applying a cool cloth or using a cool fan can help stabilize blood pressure by slightly lowering body temperature. For patients with mild symptoms, a small, supervised oral fluid intake may be permitted, though this is often a secondary measure.
Preventative Adjustments During Dialysis
Prevention strategies focus on modifying the dialysis prescription to make the fluid removal process gentler on the patient’s circulatory system. The Ultrafiltration Rate (UFR) is a major factor, and avoiding rates exceeding 10 mL/kg/hr is a common preventative goal. Clinicians may increase the total treatment time, allowing the necessary fluid volume to be withdrawn more slowly and giving the body more time for vascular refilling.
Using cooler dialysate fluid, often called cool dialysis, is another effective technique. Dialysate temperatures are typically lowered to approximately 0.5 degrees Celsius below the patient’s core body temperature. This cooling effect helps constrict peripheral blood vessels, which aids in maintaining vascular resistance and stabilizes blood pressure despite the fluid loss.
Dialysis machines can employ “profiling” techniques to manage fluid removal and sodium concentration dynamically throughout the session. Ultrafiltration profiling involves setting the machine to remove fluid more aggressively at the beginning of the treatment and then gradually slowing the rate towards the end. This aims to match the patient’s natural rate of vascular refilling, which is typically higher at the start of the session.
Similarly, sodium profiling involves using a higher sodium concentration in the dialysate early in the session to facilitate fluid removal, followed by a reduction later on. The higher sodium helps draw fluid into the blood, but the concentration is lowered near the end to prevent excessive thirst and subsequent high fluid gain between sessions. Adjustments to other dialysate components, such as raising the calcium concentration, are also considered to help maintain heart function and vascular tone during treatment.
Long-Term Fluid and Medication Management
Successful long-term management of low blood pressure depends on minimizing the fluid removed during each session. This requires strict management of Interdialytic Weight Gain (IDWG), the weight gained between dialysis appointments. Patients are encouraged to limit IDWG to no more than 1.0 to 1.5 kilograms between treatments.
Excessive IDWG forces the care team to use high ultrafiltration rates, which directly increases the risk of PDH. The primary strategy for controlling IDWG is adhering to prescribed fluid restrictions and limiting dietary sodium intake, often to 2 to 3 grams per day. Restricting sodium reduces the patient’s drive to drink and lowers the overall fluid accumulation between sessions.
A thorough review of the patient’s existing medication regimen is also standard chronic management. Physicians must assess whether any blood pressure medications are contributing to drops during dialysis. The timing of these medications may be adjusted, often recommending a nighttime dose instead of one taken just before the session, to reduce their hypotensive effect. For patients with persistent, severe PDH, the physician may prescribe an oral vasopressor, such as Midodrine, which helps constrict blood vessels and raise blood pressure.