Oxygen Supplementation and Hyperoxia in Critically Ill Cardiac Patients.

Oxygen therapy is essential in critically ill cardiac patients, but its use requires careful titration. Hypoxemia (as defined by a PaO₂/FiO₂ < 300) can worsen myocardial ischemia, precipitate arrhythmias, aggravate shock, and contribute to secondary neurological injury after cardiac arrest. Conversely, unnecessary hyperoxemia may increase oxidative stress, promote coronary and systemic vasoconstriction, impair microcirculatory flow, and affect hemodynamics. This narrative review summarizes the physiological basis of oxygen as a cardiovascular intervention and discusses the evidence guiding oxygen use in acute coronary syndromes, cardiac arrest, post-resuscitation care, acute heart failure, cardiogenic pulmonary edema, cardiogenic shock, cardiac surgery, and cardiac intensive care. Oxygen should be administered immediately when hypoxemia, respiratory distress, shock, cardiac arrest, or peri-intubation instability is present. After stabilization, the fraction of inspired oxygen (FiO₂) should be reduced to maintain adequate oxygenation while avoiding supraphysiological arterial oxygen partial pressure (PaO₂>100 mmHg). Bedside decisions could integrate peripheral oxygen saturation and PaO₂ plus hemoglobin concentration, cardiac output, perfusion, lactate, acid-base status, respiratory effort, and the clinical trajectory. In cardiac critical care, oxygen should be prescribed as a titrated therapy with a clear indication, device, target range, monitoring plan, and criteria for escalation or de-escalation.