Q:  Symptomatic hypotension is a very common and frequent complication in patients receiving hemodialysis. What newer interventions are available besides sodium modeling?
 
A: Intradialytic hypotension is estimated to occur in 20% of hemodialysis sessions and leads to chronic overhydration and inadequate dialysis. A factor that is initially involved in this process is a decrease in blood volume during dialysis. This can cause an imbalance between the ultrafiltration (UF) rate  and the plasma refilling rate of the patient (Dasselaar, Huisman, deJong, & Franssen, 2005). Other contributing factors include large interdialytic weight gains and subsequent large UF goals and hemodialysis treatment times, usually 4 to 5 hours.

Traditional Method
Although there has been an increase in the sophistication of the technological aspects of dialysis hardware, linear decreasing UF profile or no UF profile have been the most common practices for years (see Figure 1).

Factors Involved in Ultrafiltration
Currently accepted thinking holds that the ability to ultrafiltrate fluid from a patient is dependent on the individual patient’s capability to refill the vascular space during dialysis, that is, move fluid from the tissues back into the vascular space. This refilling capacity plays an important role in the hemodynamic stability during hemodialysis with ultrafiltration. Modern technology, such as the ‘crit line’ or blood volume monitor (BVM), has increased the ability of dialysis staff to monitor vascular refilling during dialysis, as well as enabling nurses to observe the effects of their interventions on refilling capability. In our experience and in previous research, patients are more likely to develop hypotension when the blood volume monitor reads a blood volume below 85% of the starting value (Johner, Chamney, Schneditz, & Kramer, 1998).

Ultrafiltration Profiling
The Fresenius 4008 series/Australia model hemodialysis machine has preinstalled a number of UF profiles that nursing staff may select as alternatives to traditional linear fluid removal patterns. Preset profiles number 5 (see Figure 2) and number 6 provide rapid pulsating ultrafiltration and refilling (resting) mode. The treatment is divided into 10 equal sessions of ultrafiltration and refilling modes alternately. In these profiles, each ‘block’ of ultrafiltration or refilling lasts 24 minutes in a standard 4-hour session. That is to say, the 4-hour session (240) minutes is equally divided into 10 incremental segments of 24 minutes each. This has been found to be a useful means of achieving higher ultrafiltration goals in many younger and/or healthier patients.

Since many patients in our renal unit have underlying co-morbidities, there is a need to identify an alternate means of management. It was thought that by decreasing the length of the ultrafiltration and pulses, there would be more opportunities for refilling to occur. There would also be a concurrent decrease in the length of refilling pulses.

Optimal Method of Ultrafiltration
By dividing the UF goal and treatment time in half, and applying the UF profiling number 5 to each half of the treatment session, it creates a total of ten 12-minute sessions of ultrafiltration and refilling mode respectively. The nurse programs the machine for a 2-hour treatment and is then required to reprogram at the end of the 2-hour period (see Figure 4).

Assessment of blood pressure, jugular venous pressure, alertness, and blood volume monitoring was done every half hour to help the health care provider decide the UF volume on the second half of the treatment (see Figure 3).

Using the blood volume monitor, we were able to visualize in real time the patient’s vascular refill activity (see Figure 4). Frequent monitoring of patient blood pressure and symptoms was also undertaken. In the majority of patients, hemodynamic stability was well demonstrated (see Figure 5). About 90% of patients utilizing this method have been successfully achieving the UF goal safely.

Results seen are encouraging; patients are able to achieve greater ultrafiltration and therefore are more often meet their dry weight for the day.  Many patients engaging in such UF profiling report subjective improvements in well being during and between dialysis sessions, and request the same treatment whenever possible.

Nursing Implications
Ultrafiltration profiling can increase dialysis tolerance, decrease interventions during dialysis, and hopefully, improve patient well-being. Selecting appropriate UF profiles not only reduces intradialytic hypotension but provides a more effective treatment. By helping patients achieve their target weight (see Figure 6), nephrology nurses can have a positive impact on the detrimental effects of overhydration and help to decrease cardiac complications. This type of profiling can also help nurses in the acute setting to provide a successful treatment in patients who cannot be weighed or those who do not have an established target weight.