Disturbance of cerebral oxygenation and hemodynamics related to the opening of the bypass bridge during veno-arterial extracorporeal membrane oxygenation

The objective of this study was to investigate changes of cerebral oxygenation and hemodynamics related to opening of the bypass bridge during veno-arterial extracorporeal membrane oxygenation (ECMO). Ten newborn infants and 12 piglets were studied during opening of the bridge for 10 and 1 s, respectively. Changes in cerebral concentration of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), (oxidized-reduced) cytochrome aa3 (cCyt.aa3), and blood volume (CBV) were continuously measured by near infrared spectrophotometry. Heart rate, arterial O2 saturation (saO2), and mean arterial blood pressure (MABP) were measured simultaneously. In the piglets, central venous pressure (CVP), intracranial pressure (ICP), and left common carotid artery blood flow (CaBF) were also measured. Opening of the bridge for 10 s in the infants resulted in a significant decrease in MABP, saO2, and cO2Hb, whereas cHHb increased. CBV did not change significantly. In piglets biphasic changes were observed for MABP, CaBF, cO2Hb, and CBV, showing an initial decrease followed by a smaller increase. cHHb and CVP showed reverse biphasic changes. ICP increased but saO2 was unchanged. In all cases heart rate and cCyt.aa3 did not change significantly. Opening of the bridge for 1 s resulted in minor changes in only a few variables. In conclusion, opening of the bridge resulted in a decrease of CBV and cerebral O2 supply due to a decrease of cerebral blood flow, followed by a compensatory increase of cerebral O2 extraction and vasodilatation. The return of oxygenated blood after reclosing resulted in an increase of CBV with overcompensation of cerebral O2 supply.