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Roller Versus Centrifugal Pumps

Optimal Blood Pump

Tayama et al. Suggested That the Ideal Blood Pump for ECC Must: Have the Capacity to Deliver up to 7 l/min Against a Pressure of 500 mm Hg Should not Damage the Cellular or Acellular Components of the Blood Should Have Smooth Surfaces Must be Free of Areas of Stasis or Turbulence Should Have Accurate and Reproducible Flow Measurement Should Have a Back-up or Manual Mode of Operation in Case of Motor Failure

Roller Pumps – How They Work

The Propulsion of Blood Occurs by the Action of Two Rollers Sequentially Compressing a Segment of Tubing Causing the Forward Movement of Blood

Roller Pumps – Proper Occlusion

PRESSURE METHOD (can be done with sterile circuit primed) Place Fluid Primed Tubing Inside Roller Head Must Have a Pressure Manometer Integrated into the Positive Flow Outflow Line Tighten Occlusion of the Pump until Fully Occluded Clamp Outflow Line Immediately Beyond the Pressure Manometer Manually Rotate Pump Head until Manometer Reads 200 mmHg Slowly Back off the Occlusion until the Pressure Drops to 100 mmHg Over 1 Minute Do the Same for the Other Roller on the Pump

Roller Pumps – Proper Occlusion

WATER COLUMN METHOD (can not be done sterile) Place Tubing Inside Roller Head Must Have a Bucket of Water with Inflow Outflow Lines under Water Circulate the Water to Prime the Lines Tighten Occlusion of the Pump unti Fully Occluded Hold Outflow Line Vertical with ends two Feet Above the Pump Head Slowly Back off the Occlusion until the Fluid Level Drops 1 mm/min Do the Same for the Other Roller on the Pump

Roller Pumps Advantages:

Less Expensive Lower Prime Volume Easy to Prime Flow is not After Load Dependent Reliable Constant Flow Rate Do Not Allow Retrograde Flow

Roller Pumps Disadvantages:

Occlusive Are Not After Load Dependent Will Pump Against any Resistance and may Result in Vessel Dissection, Pump Tubing Disconnection or Rupture Capable of Pumping Massive air Through the Outflow Line Preload Dependent Highly Capable of Cavitation As the Tubing Expands Behind the Roller, There is a Period of Negative Pressure This Momentary Negative Pressure in the Absence of Adequate Preload, May Induce The Cavitation Of Air Dissolved In The Solution

Hemolysis

The Magnitude of Hemolysis is Related to both the Time and Exposure of the Blood to Shear Forces Generated by the Pump A Region of High Pressure and Shear Force is Created at the Leading Edge of the Roller Where the Tubing is Compressed Over Occlusion: Crushes the Cellular Components Causing Hemolysis Under Occlusion: Causes Severe Forward and Backward Turbulence Causing Shear Stress and Hemolysis

Spallation

Particulate Emboli may be Generated by Micro Fragmentation (or Spallation) of the Inner Surface of the Tubing where the Roller Contacts the Tubing and where the Fold at the Edges of the Tubing Occurs Studies of Tubing wear over Time have shown that Polyvinylchloride Fragments Generated from Roller Pumps are Numerous, Frequently 20 mm in Diameter, and begin to Occur During the First Hour of use

Centrifugal Pumps – How They Work

Are Nonocclusive Pumps that Function by Producing a Constrained Vortex Within a Polycarbonate Structure The Inner Mechanism may Either be Cones or Impellers that Rotate at a High RPM The High RPM Exerts an Outward Centrifugal Force on the Blood where the Outlet is Located, Where it Exits the Pump and Results in Forward Movement of Fluid Blood Flow Rate is Increased by Increasing the Revolutions per Minute Thereby Increasing the Centrifugal Force Exerted The Disposable Pump Head is Coupled to the Console Unit via Magnetic Motor Drive

Centrifugal Pumps Advantages

Non – Occlusive, will not Pump Against any Resistance Are After Load Dependent Less likely to Result in Vessel Dissection, Pump Tubing Disconnection or Rupture Flow is Preload Dependent No Cavitation Less Hemolysis Will De-Prime when challenged with Gross Air

Centrifugal Pumps Disadvantages

More Expensive Increased Prime Volume More Difficult to Prime Allow for Retrograde Flow Less Likely to Result in Vessel Dissection, Tubing Rupture or Disconnection Thrombus formation Low Anticoagulation / Long Pump Runs Heat Generation (Hemolysis, Clotting) Magnetic Decoupling

Research Studies:

A Number of Investigators have Performed in vitro Studies Comparing Centrifugal Pumps and Roller Pumps in Terms of Blood Handling During Short & Long- Term use Tamari et al. Examined Hemolysis under Various Flow and Pressure Conditions in vitro using Porcine Blood and Concluded that the Hemolysis was Related to: Duration of Blood Exposure to Shear Stress The Pump Pressure of the Outflow The Flow Rate of the Pump Many Studies Reported Less Hemolysis with Centrifugal Pump When Tested in Vitro Many Trials have been Conducted to Compare Centrifugal and Roller Pumps in Relation to Emboli Generation, Blood Trauma, and Clinical Outcomes In a Randomized Trial by Wheeldon et al., Found Centrifugal Pump to Have Significantly Less Micro-emboli Generation Less Complement Activation Better Preservation of Platelet Count was Observed in Patients with Centrifugal Pump Many Trials have been Conducted to Compare Centrifugal and Roller Pumps in Relation to Emboli Generation, Blood Trauma, and Clinical Outcomes In a Randomized Trial by Wheeldon et al., Found Centrifugal Pump to Have Significantly Less Micro-emboli Generation Less Complement Activation Better Preservation of Platelet Count was Observed in Patients with Centrifugal Pump

Literature:

Bharat Datt, MSc, CCP, CPC, FPP; Moui B. Nguyen, CCP; Gary Plancher, CCP; Mark Ruzmetov, MD, PhD, SA-C; Michael O’Brien, PA-C; Alicia Kube, RN; Hamish M. Munro, MD, FRCA; Kamal K. Pourmoghadam, MD; William M. DeCampli, MD, PhD

The Impact of Roller Pump vs. Centrifugal Pump on Homologous Blood Transfusion in Pediatric Cardiac Surgery

J Extra Corpor Technol. 2017;49:36–43 The Journal of ExtraCorporeal Technology The Heart Center at Arnold Palmer Hospital for Children, Orlando, Florida Presented at the 53rd AMSECT International Conference, Tampa, Florida, April 17 2015 and the Society for Advancement of Blood Management 2015 Annual Meeting 240 Pediatric Patients 140 Centrifugal Pump and 100 Roller Pump Roller Pump Group Decreased Priming Volume Increased Hct Blood Primes Decrease in Intra-Operative Transfusions Decreased Mortality

Research Studies – Closing Comments

In researching the clinical benefits of one type of pump versus the other, in terms of hemolysis, inflammatory response (cytokines, complement, interleukins), fibrinolysis, platelet activation, etc., one is likely to discover many contradicting studies. There are likely as many studies claiming one type of pump over the other, in many short term and long term clinical aspects. For example there are studies demonstrating centrifugal pumps being more gentle (less hemolytic, etc.), however there are studies that conclude that even a poorly occlusive roller pump is less hemolytic than centrifugal pumps. There are many studies that have found no clinical difference in outcomes. In the end, it remains the education of the perfusionist to research and conclude for one’s self which is best for their patients. However, there is one stand out characteristic that centrifugal pumps have above roller pumps, and that is in the area of Safety.