Why does blood pressure drop during dialysis?

During dialysis, a patient's blood pressure can drop for several reasons:

Fluid removal: Dialysis involves the removal of excess fluid from the body to prevent fluid overload. As fluid is removed, the volume of blood circulating in the body decreases, leading to a drop in blood pressure.

Ultrafiltration: During hemodialysis, a process called ultrafiltration is used to remove fluid from the blood. Ultrafiltration involves the application of a negative pressure to the dialyzer, which draws fluid out of the blood vessels and into the dialysis solution. This fluid removal can cause a decrease in blood volume and blood pressure.

Solute removal: Dialysis also removes waste products and solutes from the blood, including sodium and urea. These solutes can have an effect on blood pressure regulation. For example, sodium retention can lead to increased blood pressure, while sodium removal during dialysis can result in a decrease in blood pressure.

Vasodilation: Dialysis can cause vasodilation, which is the widening of blood vessels. Vasodilation reduces the resistance to blood flow, leading to a drop in blood pressure. This vasodilation may be caused by several factors, including the removal of vasoconstrictors (substances that cause blood vessels to narrow) during dialysis and the release of vasodilators (substances that cause blood vessels to widen) in response to the changes in fluid and electrolyte balance.

Medications: Some medications used during dialysis, such as antihypertensive drugs or diuretics, can also contribute to a drop in blood pressure.

Underlying medical conditions: Patients with underlying medical conditions that affect blood pressure, such as diabetes, heart disease, or kidney disease, may experience fluctuations in blood pressure during dialysis.

Therefore, it is essential for healthcare professionals to closely monitor a patient's blood pressure during dialysis and make necessary adjustments to maintain hemodynamic stability and prevent complications related to blood pressure changes.