Intradialytic hypotension (IDH) is a common occurrence for individuals undergoing hemodialysis, a procedure that removes waste products and excess fluid from the blood when kidneys no longer function properly. It refers to a noticeable drop in blood pressure that happens during or shortly after a dialysis session. This condition affects a substantial portion of patients receiving hemodialysis, with reported frequencies ranging from 8% to 40%. IDH generally involves a decrease in systolic blood pressure of 20 mmHg or more, or a decrease in mean arterial pressure of 10 mmHg or more, often accompanied by symptoms.
Underlying Causes
IDH arises from a combination of factors related to the patient’s health and the specifics of the dialysis treatment. Patient-related factors include pre-existing medical conditions that affect the body’s ability to maintain stable blood pressure. Individuals with heart disease, including heart failure, are more susceptible because their hearts may struggle to compensate for rapid fluid removal. Diabetes mellitus also increases IDH risk due to its association with autonomic dysfunction, which impairs the body’s natural blood pressure regulation.
Anemia, common in kidney disease, also contributes to IDH risk. The patient’s “dry weight,” the target weight without excess fluid, plays a role; if this target is set too low, excessive fluid removal can occur. Eating a large meal right before or during dialysis can divert blood flow to the digestive system, reducing blood volume and increasing IDH risk. Taking certain blood pressure medications just before a dialysis session can also lower blood pressure, making a drop during treatment more likely.
Dialysis treatment-related factors also contribute to IDH. The rate at which fluid is removed, known as the ultrafiltration rate, is a primary cause. If fluid is removed too quickly, it can outpace the body’s ability to refill blood vessels from surrounding tissues, leading to a drop in circulating blood volume and blood pressure.
The temperature of the dialysate can influence blood pressure. A warmer dialysate can cause blood vessels to widen, which lowers blood pressure and makes IDH more likely. Conversely, cooler dialysate may help prevent blood pressure drops by promoting vasoconstriction. The sodium concentration in the dialysate also contributes; a lower sodium concentration can lead to more rapid fluid shifts out of the bloodstream, contributing to hypotension.
Recognizing the Symptoms
Identifying the signs of intradialytic hypotension quickly allows for prompt intervention by clinical staff. Patients experiencing IDH report a range of symptoms as their blood pressure falls. Common symptoms include feeling dizzy or lightheaded, which can make it hard to maintain balance. Nausea is also frequently reported.
Some individuals might experience abdominal cramping. Yawning and excessive sweating can also occur as the body reacts to the sudden blood pressure drop. Blurred vision is another symptom that may signal IDH onset. In more severe instances, the blood pressure drop can lead to fainting or loss of consciousness.
Management and Prevention
Managing IDH during a dialysis session involves immediate steps to restore blood pressure and alleviate symptoms. When a patient experiences a blood pressure drop, the dialysis staff may first place the patient in a reclined position with their head lower than their feet to encourage blood flow back to the brain and heart. Simultaneously, the rate of fluid removal (ultrafiltration) is reduced or temporarily stopped to prevent further decreases in blood volume. If these measures are not enough, a healthcare provider may administer a bolus of isotonic saline to quickly increase the volume of fluid in the bloodstream and raise blood pressure.
Long-term prevention strategies aim to reduce the frequency and severity of IDH episodes. A primary strategy involves adjusting the patient’s “dry weight” to ensure adequate fluid removal without causing excessive dehydration.
Using a cooler dialysate temperature can help prevent blood vessel widening and maintain blood pressure. Sodium profiling may be used; this often involves starting with a higher sodium concentration and gradually reducing it to help maintain plasma volume.
Patients are also advised to avoid large meals immediately before or during dialysis, as eating can divert blood flow and contribute to hypotension. Adjusting the timing of blood pressure medications, in consultation with a doctor, can also prevent medications from lowering blood pressure too much during treatment.
Potential Complications
Frequent or severe episodes of intradialytic hypotension can lead to several health complications, making effective management and prevention important. One concern is “organ stunning,” a temporary impairment of organ function due to reduced blood flow. The heart can be affected, leading to “myocardial stunning,” where the heart muscle experiences temporary weakness or damage from insufficient blood supply. The brain can also be impacted by reduced blood flow, potentially causing temporary neurological symptoms or contributing to cognitive issues over time. Similarly, the gut can suffer from mesenteric ischemia, a condition where blood flow to the intestines is reduced, leading to discomfort or more serious issues.
Another consequence of severe IDH is the premature termination of the dialysis treatment. When treatment is cut short, the patient may not receive an adequate clearance of toxins and excess fluid, which can lead to complications from fluid overload and accumulation of waste products. This inadequate dialysis can contribute to increased post-dialysis fatigue, a common symptom. Chronic or recurrent IDH has been linked to increased long-term health risks, including higher rates of cardiovascular events and overall mortality in dialysis patients.