Lack of funding

Currently, decisions regarding volume management for dialysis sessions in the ICU are made in large part on the nephrologists'/intensivists' overall gestalt. This gestalt is based upon a combination of commonly used measures of circulatory function, the physical exam, fluid balance, estimates of dialysis dry weight, and monitoring changes in relative blood volume status using devices such as the Crit-Line™ III, and central venous pressures. However, these tools perform poorly in predicting the circulatory system's overall response to dialysis. Consequently, episodes of dangerously low blood pressure are still frequently encountered. Better techniques to predict the circulatory system's response to dialysis are much needed. The intent of this study is to test newer metrics of circulatory system function for their ability to predict low blood pressure episodes during dialysis. This is important because it may enable the design of newer treatment strategies created to prevent low blood pressure episodes during dialysis and improve patient outcomes. The investigators overall hypothesis is that newer measures of vascular volume and dynamic indices of fluid responsiveness, previously found to better reflect cardiac preload state than currently used parameters, will better predict low blood pressure episodes during dialysis than current methods.

Inclusion Criteria:

• Admitted to OHSU Hospitals ICUs
• Patient has acute or chronic needs for intermittent hemodialysis support during their ICU stay for any reason other than isolated hyperkalemia
• Central venous access in place separate from the dialysis catheter, or arteriovenous fistula or graft
• Two or more organ systems affected by critical illness requiring supportive care as documented in the medical chart.

Exclusion Criteria:

• age younger than 18 years old
• Weight > 160 kg
• burns greater than 40% total body surface area
• known cardiac or vascular aneurysm
• contraindications to femoral arterial puncture
• diagnosis of peripheral vascular disease
• not committed to full support
• participation in other experimental medication trial within 30 days
• current atrial or ventricular arrhythmias
• history of sever CHF- NYHA class >= III, previously documented EF < 30%
• severe aortic regurgitation
• anticipated ICU stay < 24 hrs
• not expected to require dialysis > 48 hours

Any patient 18 years and older who is admitted to the OHSU Hospitals ICUs with ARF, or End Stage Renal Disease (ESRD) for a diagnosis other than hyperkalemia, as the sole determinant for that level of care, will be invited to participate. The patient must have acute or chronic needs for dialytic support during their ICU stay in order to qualify for the study. Dialysis support may be provided by intermittent HD sessions, or continuous venovenous hemodiafiltration (CVVHDF) depending on the underlying hemodynamic stability of the patient.