A long-term stable normothermic cardiopulmonary bypass model in neonatal swine

What factors contribute to the elevation of serum free fatty acid levels in newborns in the cardiac surgical setting?

Elevations in serum free fatty acid (FFA) levels during heart surgery have been reported in humans and experimental animals, causing increased arrhythmias, decreased heart function, and contributing to mortality. Factors such as heparin administration, age, cardiopulmonary bypass (CPB), and cyanosis or hypoxia have been implicated but not proven. This study was designed to clarify the contribution of these factors using an experimental pig model as follows: (i) adult (n = 10) versus 3-day-old piglets (n = 18) had FFA levels assessed before and after heparin administration; (ii) 3-day-old piglets, the additional effect of CPB (n = 8) or just severe hypoxia (PaO₂ = 20-25 mm Hg; n = 6) exposure on FFA levels. This work demonstrated that significant elevations in serum FFA were mainly due to heparin administration, with modest contributions by young age, CPB, and hypoxia. Our preliminary clinical investigations also suggest that children undergoing CPB are at risk of being exposed to high FFA levels and that these patients only suffered a decrease in heart function when these elevations were present in conjunction with cyanosis and (or) prolonged ischemic time. These initial findings require further confirmation. Given these findings, pharmacotherapeutics geared towards limiting FFA elevations should be considered, especially in young children undergoing pediatric cardiac surgery.

Oxygenator Is the Main Responsible for Leukocyte Activation in Experimental Model of Extracorporeal Circulation: A Cautionary Tale

In order to assess mechanisms underlying inflammatory activation during extracorporeal circulation (ECC), several small animal models of ECC have been proposed recently. The majority of them are based on home-made, nonstandardized, and hardly reproducible oxygenators. The present study has generated fundamental information on the role of oxygenator of ECC in activating inflammatory signaling pathways on leukocytes, leading to systemic inflammatory response, and organ dysfunction. The present results suggest that experimental animal models of ECC used in translational research on inflammatory response should be based on standardized, reproducible oxygenators with clinical characteristics.

A novel minimal invasive mouse model of extracorporeal circulation

Extracorporeal circulation (ECC) is necessary for conventional cardiac surgery and life support, but it often triggers systemic inflammation that can significantly damage tissue. Studies of ECC have been limited to large animals because of the complexity of the surgical procedures involved, which has hampered detailed understanding of ECC-induced injury. Here we describe a minimally invasive mouse model of ECC that may allow more extensive mechanistic studies. The right carotid artery and external jugular vein of anesthetized adult male C57BL/6 mice were cannulated to allow blood flow through a 1/32-inch external tube. All animals (n = 20) survived 30 min ECC and subsequent 60 min observation. Blood analysis after ECC showed significant increases in levels of tumor necrosis factor α, interleukin-6, and neutrophil elastase in plasma, lung, and renal tissues, as well as increases in plasma creatinine and cystatin C and decreases in the oxygenation index. Histopathology showed that ECC induced the expected lung inflammation, which included alveolar congestion, hemorrhage, neutrophil infiltration, and alveolar wall thickening; in renal tissue, ECC induced intracytoplasmic vacuolization, acute tubular necrosis, and epithelial swelling. Our results suggest that this novel, minimally invasive mouse model can recapitulate many of the clinical features of ECC-induced systemic inflammatory response and organ injury.

Establishment of an animal model of extracorporeal membrane oxygenation in rabbits

OBJECTIVE

This study was undertaken to establish an animal model of extracorporeal membrane oxygenation in rabbits.

METHODS

Ten New Zealand white rabbits weighing 2573±330 g were used in this study. Extracorporeal membrane oxygenation was established in these animals through cannulation of the right carotid artery and jugular vein for arterial perfusion and venous return. The components of the perfusion circuit were specially designed. Arterial blood pressure was measured with a blood pressure meter through cannulation of the right femoral artery. The heart rate and blood gas parameters were also monitored by electrocardiography and a blood gas analyzer (Radiometer ABL800, Bronshøj, Denmark), respectively.

RESULTS

The rabbit model of extracorporeal membrane oxygenation was established successfully. The hemodynamic and blood gas parameters were changed within an acceptable range during the extracorporeal membrane oxygenation process. The specially designed miniature membrane oxygenator was sufficient to meet the extracorporeal membrane oxygenation needs in this animal model.

CONCLUSION

The rabbit model of extracorporeal membrane oxygenation established through right carotid artery and jugular vein cannulation is feasible, easily operated and economical. It is an ideal model for further research of the pathophysiology and organ protection offered through the application of extracorporeal membrane oxygenation.

Establishment of rat model of cardiopulmonary bypass in pulmonary hypertension

An experimental model of cardiopulmonary bypass in rats with pulmonary hypertension is necessary to understand underlying mechanisms and develop protective strategies. Male Sprague-Dawley rats were randomly divided into a sham group, cardiopulmonary bypass group, pulmonary hypertension group, and pulmonary hypertension with cardiopulmonary bypass group. Both groups with pulmonary hypertension received a subcutaneous injection of monocrotaline 60 mg x kg(-1) on day 0. Cardiopulmonary bypass was instituted in one of them 21 days later. The sham and pulmonary hypertension control groups underwent cannulation only. Cardiopulmonary bypass was conducted for 60 min at a flow rate of 100 mL x kg(-1) x min(-1). Hemodynamic investigations, blood gas analysis, interleukin-6, tumor necrosis factor-alpha, and survival studies were performed subsequently. Time-dependent increases of serum interleukin-6 and tumor necrosis factor-alpha were found after cardiopulmonary bypass in both groups. This model allows the study of multiple organ pathophysiological processes after cardiopulmonary bypass in rats with pulmonary hypertension, as well as the evaluation of possible protective strategies.

A rat model of cardiopulmonary bypass with excellent survival

BACKGROUND

Elucidating the underlying mechanisms and developing protective strategies for the pathophysiological consequences of cardiopulmonary bypass (CPB) have been hampered due to the absence of a satisfactory long-term recovery animal model. The objective of this study was to establish a survival experimental model of CPB in rats to meet the requirement of these studies.

MATERIALS AND METHODS

Male SD rats (450-550 g) were randomly divided into CPB (n = 10) group and Sham group (n = 10). All rats were anaesthetized and mechanically ventilated. The femoral artery and vein were cannulated for continuous blood pressure recordings and fluid replacement, respectively. The CPB circuit comprised a venous reservoir, a membrane oxygenator, and a roller pump. Blood was drained from the right atrium via a jugular vein catheter and returned to the right carotid artery. Priming consisted of 8 ml of homologous blood and 8 ml of colloid. CPB was conducted for 60 min at a flow rate of 100-150 ml/kg/min in the CPB group. Haemodynamic investigations, blood gas analysis, and survival studies were performed subsequently.

RESULTS

Our data show that the rat model principally simulated the clinical setting of CPB in terms of its construction, configuration, performance, material surface area, and priming volume to blood volume ratio. All CPB rats survived and the 2-week follow-up period remained uneventful.

CONCLUSIONS

The rat model of CPB was easy to establish and was associated with excellent survival. This model should facilitate the investigation of the pathophysiological processes concerning CPB-related multiple organ dysfunction and possible protective interventions.