Many dialysis patients are fluid overloaded or hypervolemic, which can lead to hypertension1, left ventricular hypertrophy2, and congestive heart failure3. Cardiovascular strain can be a consequence of interdialytic weight gain, chronic fluid overload and inappropriate fluid removal during hemodialysis4,5. Fluid overload is associated with hemodynamic instability and higher cardiovascular morbidity6,7. As such, fluid management and the achievement of a normal hydration status or euvolemia is important.

Crit-Line® technology can provide the clinician insight as to how a patient is tolerating dialysis throughout a treatment. Adjusting ultrafiltration rates and maximizing the amount of fluid removal, while minimizing the potential for hypovolemic and intradialytic symptoms, is critical to a more effective dialysis treatment. Crit-Line technology allows the clinician to do just that.

Crit-Line Technology:

  • Provides insight as to how a patient is tolerating dialysis.8,9
  • Provides the clinician with data that may help remove the maximum amount of fluid while preventing common symptoms of dialysis (nausea, cramping and vomiting).8,9,10,18
  • Provide data that allows for a more effective treatment for dialysis patients and clinicians.8,9,10,11,12,13,14,16,17 
  • Provides data to help identify patients that may be at risk for intradialytic symptoms.8,9,10,15
  • Helps the healthcare professional visualize the patient's plasma refill rate in real-time.9,15

Crit-Line technology is a cost-effective method to continuously monitor key blood parameters during therapy allowing the clinician to determine appropriate intervention, if needed, during treatment.

Watch our video on monitoring blood volume using Crit-Line Technology.  

Crit-Line Technology Support Line

877-CLM-LINE (877-256-5463)

Our team of highly trained, dedicated clinicians offer telephone assistance and Crit-Line IV and CLiC device-based support services.  We are available to answer your questions or connect you with the right resource. 


Please join as MDs with notable expertise in the areas of fluid management in the ESKD patient present current findings regarding Crit-Line technology, health outcomes, as well as health economic data from real-world scenarios.

Both programs presented monthly, select "Register Now" to review dates and select programs.

CLiC Device
Crit-Line® IV Monitor
  1. Dionisio P, et al. Influence of the hydration state on blood pressure values in a group of patients on regular maintenance hemodialysis Blood Purif. 1997; 15:25-33 
  2. Stegmayr BG. Ultrafiltation and dry weight – what are the cardiovascular effects? Artif Organs 2003; 27:227-229 
  3. Harnett JD, et al. Congestive heart failure in dialysis patients: Prevalence, incidence, prognosis and risk factors Kidney Int. 1995; 47:884-890 
  4. Kalantar-Zadeh K, et al. Fluid retention is associated with cardiovascular mortality in patients undergoing long-term hemodialysis. Circulation. 2009; 119(5):671–679 
  5. Wizemann V, et al. The mortality risk of overhydration in haemodialysis patients. Nephrol Dial Transplant. 2009; 24(5):1574–1579 
  6. Jacobs LH, et al. Inflammation, overhydration and cardiac biomarkers in haemodialysis patients: a longitudinal study. Nephrol Dial Transplant. 2010; 25(1):243–248.
  7. David S, et al. Diagnostic value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) for left ventricular dysfunction in patients with chronic kidney disease stage 5 on haemodialysis. Nephrol Dial Transplant. 2008; 23(4):1370–1377
  8. Sinha, A. et al., "Relative plasma volume monitoring during hemodialysis AIDS the assessment of dry weight." Hypertension 55.2 (2010): 305-311.
  9. Rodriguez H, et al., Assessment of dry weight by monitoring changes in blood volume during hemodialysis using Crit-Line, Kidney International 2005 Aug, 68(2); 854-861.
  10. Fresenius Medical Care, 2008T Hemodialysis Machine Operator’s Manual, P/N 490122 Rev AA, Concord, CA, January 2024.
  11. Preciado, P, et al, All-cause mortality in relation to changes in relative blood volume during hemodialysis, Nephrol Dial Transplant (2018) 1-8.
  12. Ficociello LH, Balter P, Mark Costanzo, Patrice Taylor, Claudy Mullon, Robert Kossmann, Blood Volume and Mortality in Hemodialysis Patients,  American Society of Nephrology Annual Symposium, 2015
  13. Agarwal R, Hypervolemia Is Associated With Increased Mortality Among Hemodialysis Patients, Hypertension. 2010;56(3):512-7
  14. Keane DF, Raimann JG, Zhang H, Willetts J, Thijssen S, Kotanko P. The time of onset of intradialytic hypotension during a hemodialysis session associates with clinical parameters and mortality. Kidney Int. 2021;99(6):1408–17. 
  15. Jabara, A, et al., Determination of Fluid Shifts During Chronic Hemodialysis using bioimpedance spectroscopy and an in‐line Hematocrit Monitor, ASAIO J., 1995, Jul‐Sept; 41 (3): M682‐7.
  16. Balter P, et al.,  A year-long quality improvement project on fluid management using blood volume monitoring during hemodialysis. Curr Med Res Opin. 2015;31(7):1323-31.
  17. Parker, T. et al., A Quality Initiative. Reducing rates of hospitalizations by objectively monitoring volume removal, Nephrol News Issues. 2013 Mar;27(3):30-2, 34-6.
  18. Steuer RR, et al., Reducing symptoms during hemodialysis by continuously monitoring the hematocrit. Am J Kidney Dis. 1996;27(4):525–32.


Crit-Line Technology is designed to non-invasively measure hematocrit, oxygen saturation and percent change in blood volume. The technology employs a sensor clip which emits multiple wavelengths of light to transilluminate the blood in the Crit-Line blood chamber. The differences in light absorption between blood constituents allow for the identification and measurement of the hematocrit. The measurement of hematocrit, percent change in blood volume and oxygen saturation in real-time during hemodialysis is intended to provide a more effective treatment for both the dialysis patient and the clinician. Based on the data that the monitor provides, the clinician/nurse, under physician direction, can intervene (i.e., by increasing or decreasing the rate at which fluid is removed from the blood) to remove the maximum amount of fluid from the dialysis patient without the patient experiencing the common complications of dialysis which include nausea, cramping and vomiting. The technology is available as a standalone device (Crit-Line IV Monitor) or as an optional module on the 2008T hemodialysis machine (CLiC device).

Caution: Federal (US) law restricts these devices to sale by or on the order of a physician.

Note: Read the Instructions for Use for safe and proper use of these devices. For a complete description of hazards, contraindications, side effects and precautions, see full package labeling.

© 2017, 2019-2022, 2024 Fresenius Medical Care. All Rights Reserved. Fresenius Medical Care, the triangle logo, CombiSet SMARTECH, Crit-Line, and CLiC are trademarks of Fresenius Medical Care Holdings, Inc. or its affiliated companies. All other trademarks are the property of their respective owners. D/N US-CLM-000004 Rev B 05/2024