Impaired Diastolic Function and Disruption of the Force-Frequency Relationship in the Right Ventricle of Newborn Pigs Resuscitated with 100% Oxygen

BACKGROUND: Resuscitation with 100% oxygen increases oxidative stress and is detrimental for organ function. OBJECTIVE: To study the effects of resuscitation with 100% oxygen compared to room-air on myocardial function. METHODS: Twenty-eight newborn pigs underwent global hypoxia (8% oxygen/N2) until base excess reached -20 mmol/l. The animals were randomized into two groups and resuscitated with either 100% or room air for 30 min. Myocardial tissue Doppler velocities and acceleration of the mitral and tricuspid valve annuli during systole and diastole were assessed before global hypoxia and after resuscitation together with troponin I. RESULTS: Peak early diastolic velocity (E') and acceleration (pEac) in the septum and pEac in the lateral tricuspid valve annulus were lower after resuscitation with 100% oxygen, suggesting impaired diastolic relaxation in the right ventricle. Lower systolic velocities and acceleration in the right ventricle relative to heart rate indicate disruption of the right ventricular force-frequency relationship after resuscitation with 100% oxygen. Troponins were higher in the 100% oxygen group, suggesting increased myocardial damage in this group. CONCLUSION: Resuscitation with 100% oxygen compared to room air induces diastolic dysfunction, disrupts the systolic force-frequency relationship and increases myocardial damage in the newborn pig.