“Stolen” Blood Flow: Effect of an Open Arterial Filter Purge Line in a Simulated Neonatal CPB Model

Abstract

The purpose of this study was to evaluate the effect of different flow rates and pressures on the degree of shunting of blood flow by the arterial filter purge line in a simulated neonatal cardiopulmonary bypass circuit. The circuit was primed with heparinized bovine blood (hematocrit 24%) and postfilter pressure was varied from 60-180 mm Hg (20 mm Hg increments) using a Hoffman clamp. Trials were conducted at flow rates ranging from 200-600 ml/min (100 ml/min increments). During trials conducted at a postfilter pressure of 60 mm Hg, 42.6% of blood flow was shunted through the purge line at a flow rate of 200 ml/min, whereas only 12.8% of flow was diverted at a flow rate 600 ml/min. During trials conducted at a postfilter pressure of 180 mm Hg, 82.8% of blood flow at 200 ml/min and 25.9% of blood flow at 600 ml/min was diverted through the open arterial purge line. The results of this study confirm that a significant amount of flow is diverted away from the patient when the arterial purge line is open. Shunting of blood flow through the arterial purge line could result in less effective tissue perfusion, particularly at low flow rates and high postfilter pressures. To minimize hypoperfusion injury, a flow probe (distal to the arterial filter) may be used to monitor real-time arterial flow in the setting of an open arterial filter purge line.

Evaluation of the Quadrox-I neonatal oxygenator with an integrated arterial filter

“…Our results show that the open arterial filter purge line causes "stolen" blood flow across the oxygenator, which is consistent with our lab's past findings 14 . This "stolen" blood flow increases with higher flow rates and hypothermic conditions, as turbulence and viscosity of blood are increasing, respectively.…”

“…Blood flow and pressure measurements across a CPB circuit are significant parameters in that a significant decrease in blood flow to the patient ("stolen" blood flow) 14 or pressure drop can result in hypoperfusion of the patient, thus, increasing the potential for post-operative morbidity. These parameters can be affected by the oxygenator and arterial filter that are used, the flow rate settings, and the temperature and viscosity of the blood.…”

Microemboli Generation, Detection and Characterization During CPB Procedures in Neonates, Infants, and Small Children

“…This is especially important in neonates, infants, and small children, since it has been shown that 42.6% of pump flow was shunted through the purge line at flow rate of 200 ml/min and postfilter pressure of 60 mm Hg. 23 …”

Impact of Translational Research on Optimization of Neonatal Cardiopulmonary Bypass Circuits and Techniques—The Penn State Health Approach

“…In neonates and infants, however, the relatively large proportion of shunted flow may lead to inadequate endorgan perfusion and tissue hypoxia during CPB procedures, especially after rewarming. Our in vitro studies demonstrated that a significant amount of flow is diverted away from the patient when the arterial purge line is open (20). For example, at pump flow rates of 200-600 mL/min, the purge line diverted 87.7 mL/min (42.6%)276.3 mL/min (12.8%) of pump flow at the post-filter pressure 60 mm Hg, and 169.7 mL/ min (82.2%)2154.5 mL/min (25.9%) of pump flow at the post-filter pressure 180 mm Hg.…”