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Hemodynamic changes during opening of the bridge in venoarterial extracorporeal membrane oxygenation

van Heijst, Arno MD; Liem, Djien MD, PhD; van der Staak, Frans MD, PhD; Klaessens, John MSc; Festen, Cees MD, PhD; de Haan, Ton MSc; Geven, Wil MD, PhD; van de Bor, Margot MD, PhD

Pediatric Critical Care Medicine: July 2001 - Volume 2 - Issue 3 - p 265-270
Laboratory Investigations

Objective To investigate the cause of the hemodynamic changes occurring during opening of the bridge in venoarterial (VA) extracorporeal membrane oxygenation (ECMO).

Design Prospective intervention study in animals.

Setting Animal research laboratory of a university medical center.

Subjects Eight anesthetized lambs installed on VA-ECMO.

Interventions During VA-ECMO the bridge was randomly opened during 1, 2.5, 5, 7.5, 10, and 15 secs at ECMO flow rates of 500, 400, 300, 200, 100, and 50 mL/min. Flows in the ECMO circuit between venous cannula and bridge and bridge and arterial cannula, mean arterial blood pressure, mean left carotid artery blood flow, central venous pressure, superior sagittal sinus pressure, inline mixed venous oxygen saturation, heart rate, and arterial oxygen saturation were measured continuously. Using near infrared spectrophotometry, changes in concentrations of cerebral oxygenated and deoxygenated hemoglobin and cerebral blood volume were also measured. Values during bridge opening were compared with values before opening. The same variables were determined with a roller pump on the bridge with a flow over the bridge at various flow rates.

Measurements and Main Results Bridge opening resulted in a change of flow direction between venous cannula and bridge and bridge and arterial cannula. A biphasic response with initial decrease and secondary increase occurred in mean arterial blood pressure and mean left carotid artery blood flow. Central venous pressure, superior sagittal sinus pressure, deoxygenated hemoglobin, and cerebral blood volume increased, whereas cerebral oxygenated hemoglobin decreased. These effects occurred in each combination of ECMO flow rate and opening time. These effects could be abolished by installing a roller pump on the bridge.

Conclusions Bridge opening in VA-ECMO resulted in significant cerebral hemodynamic changes caused by an arteriovenous shunt over the bridge. The decreased cerebral perfusion pressure may contribute to the occurrence of cerebral ischemia, and the venous congestion may result in intracranial hemorrhages. These could be prevented by installing a roller pump on the bridge.

From the Departments of Pediatrics (Drs. Liem and van de Bor and Mr. Klaessens), Pediatric Surgery (Drs. van der Staak and Festen), and Medical Statistics (Mr. de Haan), University Medical Center St. Radboud, Nijmegen, The Netherlands; and the Department of Pediatrics, University Hospital Groningen, Groningen, The Netherlands (Dr. Geven).

© 2001 Lippincott Williams & Wilkins, Inc.