What does ultrafiltration refer to in dialysis?

Ultrafiltration in dialysis specifically refers to the process of removing excess fluid from the blood through the application of pressure gradients. This process is crucial for managing fluid balance in patients undergoing dialysis, particularly those with conditions like kidney failure where the kidneys are unable to adequately remove excess fluid from the body. During dialysis, a pressure difference is created across a semi-permeable membrane, facilitating the movement of water out of the blood and into the dialysate solution. This helps to clear excess fluid and maintain proper electrolyte levels, ultimately improving patient outcomes.

The other options do not accurately depict ultrafiltration. Increasing blood pressure is not the same as ultrafiltration; rather, it is a physiological parameter that can influence fluid dynamics but does not describe the ultrafiltration process itself. Adding saline to the blood is related to fluid management but is not part of the ultrafiltration mechanism in dialysis. Monitoring patient vitals post-treatment is essential for overall patient care but does not pertain to the definition of ultrafiltration.