Conventional habits with which oxygen has been dispensed in the clinical setting is under scrutiny. A conservative approach is warranted. The practice, borne of a desire to avert the immediate dangers of oxygen deprivation, has perhaps led us to overlook the subtler, yet no less significant, hazards of oxygen excess. Most recent evidence paints a compelling picture: Hyperoxia, defined with precision as a PAO2 exceeding normative physiological levels, has been implicated in the possibility of exacerbating outcomes across a spectrum of clinical scenarios, from post-cardiac arrest care to the management of acute respiratory distress.
The strategy, therefore, is threefold:
1. Identify those at risk of oxygen toxicity: Patients receiving mechanical ventilation for respiratory failure, especially with a fraction of inspired oxygen (FiO2) above 0.6 for extended periods, stand at the highest risk. The risk associated with oxygen toxicity is multifaceted, influenced by the FiO2, exposure duration, and the presence of sensitizing agents like certain drugs or radiation.
2. Closely Monitor: Anesthesia providers should carefully monitor arterial oxygen levels, employing the tools at our disposal. This involves not only the measurement of oxygen saturation but also a keen appreciation of the patient's clinical context and the dynamic interplay of physiological factors.
3. Judicious use of Oxygen: The adjustment of supplemental oxygen must be guided by the law of diminishing returns. As we increase the FiO2, the marginal benefits in terms of oxygenation must be weighed against the marginal costs in terms of potential toxicity. The goal is to find that optimal point where the benefits of supplemental oxygen are maximized while the risks are minimized. Focus on minimizing FiO2 to the lowest effective level to achieve target oxygenation, personalized according to the patient's needs. For those at increased risk, particularly in the context of ARDS, a conservative approach targeting an FiO2 below 0.6 is advocated, complemented by a suite of therapeutic strategies aimed at minimizing the need for high FiO2 levels.
