Measurement of the ductal L-R shunt during extracorporeal membrane oxygenation in the lamb

[Establishment of the patent ductus arteriosus model in preterm rats]

OBJECTIVE

To establish the patent ductus arteriosus model in preterm rats using the improved natural development method.

METHODS

In the light of the flaws of the natural development method in establishing the patent ductus arteriosus model, the experimental technology was modified to avoid the influence of fixation, dehydration, and section method on blood vessel diameter. Cesarean section was performed for a Wistar rat pregnant for 19 days, and 8 neonatal rats were obtained. After they were sacrificed by dislocation, they were embedded as a whole to avoid dehydration, and the microsection and horizontal section were made. After hematoxylin and eosin staining, a microscope was used to measure the inner diameters of the ductus arteriosus, the main pulmonary artery, and the descending aorta.

RESULTS

After the cesarean section for the rat pregnant for 19 days, patent ductus arteriosus occurred in all the 8 neonatal rats. The measurements of the inner diameters of blood vessels were as follows: the long diameter and short diameter of the descending aorta were 354±106 and 182±140 μm, respectively; the short diameter of the ductus arteriosus was 155±122 μm, and its area was 36,847±42,582 μm(2); the long axis and short axis of the main pulmonary artery were 589±150 and 174±170 μm, respectively.

CONCLUSIONS

The improved natural development method can help to successfully establish the patent ductus arteriosus model in preterm rats.

Cardiac dimensions during extracorporeal membrane oxygenation

Our aim was to analyze left ventricular fractional shortening during extracorporeal membrane oxygenation under the influence of changing volume loading conditions induced by a ductal left-to-right shunt. In all patients, the fractional shortening was observed using echocardiography before, during, and after bypass, irrespective of the presence or absence of the ductal left-to-right shunt. During membrane oxygenation, there was a significant decrease in fractional shortening (p less than 0.001), with no difference before and after membrane oxygenation. A greater decrease in fractional shortening was observed in the group with a ductal left-to-right shunt when compared to patients lacking the ductal shunt (p less than 0.006). The diastolic diameter of the left ventricle also increased significantly during the membrane oxygenation in those patients with left-to-right ductal shunting. Moreover, the patients with left-to-right shunting showed a very severe decreased fractional shortening, lower than 10 per cent, with significantly greater frequency (p less than 0.05) during the course of membrane oxygenation.

CONCLUSION

An important decrease in left ventricular fractional shortening is observed during veno-arterial extracorporeal membrane oxygenation. Left-to-right shunting during bypass, as seen in the patients with patency of the arterial duct, increases the loading conditions on the left ventricle, and produces a significant increase in left ventricular diastolic dimensions. Despite the effects of volume loading produced by the ductal shunt during bypass, the decrease in fractional shortening is significantly more pronounced for these patients. Therefore, during membrane oxygenation the volume loading produced by the ductal shunt is unable to prevent a decrease in left ventricular fractional shortening.