Evaluation of a Rat Cardiopulmonary Bypass Model Using an Extraluminal Flow Oxygenator

Cardiac operations with cardiopulmonary bypass (CPB) trigger a systemic inflammatory response. To understand the underlying mechanisms behind the biological reactions during CPB, rat models that mimic clinical CPB have been developed. Previously, a rat CPB model incorporating an intraluminal flow oxygenator was employed to accommodate the limited blood volume of rats. This study aimed to evaluate a rat CPB model incorporating an extraluminal flow oxygenator.

The effective membrane area and priming volume of the extraluminal flow oxygenator were 0.0236 m² and 3.0 mL, respectively. Rats were divided into three groups: (i) SHAM group (surgical preparation only); (ii) CPB with intraluminal flow oxygenator group (CPB Int-oxy); and (iii) CPB with extraluminal flow oxygenator group (CPB Ext-oxy). Blood samples were collected before and at 60 and 120 min after CPB initiation. Hemodynamics, blood gases, blood cell counts (RBC, WBC, PLT), and inflammatory responses (IL-6, IL-10, TNF-α) were measured.

Each CPB group maintained an arterial pressure and Hb at approximately 75 mmHg and 9.5%, respectively, without blood transfusion, and an oxygenation and carbon dioxide removal from the blood were confirmed. In the CPB Ext-oxy group, PLT counts were significantly preserved at 60 and 120 min after the start of circulation compared with those in the CPB Int-oxy group. However, no significant differences in IL-6, IL-10, or TNF-α levels were observed between the CPB groups.

Incorporating the extraluminal flow oxygenator into a rat CPB model enables the simulation of CPB conditions that closely mimic those encountered in clinical CPB.