Titrating oxygen delivery during the perioperative period is an important part of anesthesia care. For decades, clinical teaching emphasized aggressive avoidance of hypoxemia. This assumption has been substantially revised as evidence has accumulated regarding the physiological costs of excess oxygen administration. Modern perioperative care uses updated oxygenation targets to ensure adequate tissue perfusion without excessive focus on hypoxemia avoidance.
Oxygen exerts a concentration-dependent effect on the body. While adequate tissue oxygen delivery is essential for wound healing, immune function, and cellular metabolism, supraphysiologic oxygen tensions generate reactive oxygen metabolites that damage DNA, impair mitochondrial function, and injure the lung and brain parenchyma in particular (Habre and Peták, 2014). The clinical consequences of hyperoxia are not uniform across different age demographics.
Habre and Peták describe how premature infants and neonates are especially vulnerable, with hyperoxia implicated in bronchopulmonary dysplasia, oligodendrocyte apoptosis, and retinopathy of prematurity, while elderly patients face increased susceptibility to pulmonary injury, diaphragmatic dysfunction, and postoperative cognitive dysfunction related to hyperoxia-induced cerebral vasoconstriction. In contrast, adults in mid-life appear to tolerate short courses of supplemental oxygen with a more favorable risk-benefit profile, and evidence has supported modest benefit from perioperative hyperoxia in reducing surgical site infection, although this effect appears weaker and less consistent than once believed and is not observed in obese patients (Habre and Peták, 2014).
The mechanism linking oxygen delivery to surgical outcome is tissue, rather than arterial, oxygen levels, which is why it is important for anesthesia providers to understand how oxygenation measurements reflect true tissue perfusion and how that relationship differs according to physiological status. Kabon and colleagues demonstrated that obese surgical patients maintain substantially lower subcutaneous tissue oxygen than non-obese patients at equivalent arterial oxygen partial pressures, and that even markedly elevated inspired oxygen concentrations produce only modest improvement in tissue oxygenation in this population (Kabon et al., 2004). This finding underscores that arterial oxygen tension is an imperfect surrogate for the oxygen actually available in the tissue.
In the critically ill population, some research has proposed a departure from the traditional practice of tolerating unrestricted hyperoxemia while rigidly avoiding hypoxemia. The concept of precise control of arterial oxygenation calls for targeting a narrow, individualized range of arterial oxygen rather than simply exceeding a minimum threshold on the premise that both insufficient and excessive oxygenation can produce measurable harm (Martin and Grocott, 2013).
A provisional concept being explored is permissive hypoxemia, in which patients who have had time to adapt to subacute or sustained hypoxemia may tolerate, and even benefit from, oxygenation targets lower than conventionally accepted, given the marginal benefit and potential harm of pursuing normoxemia in this context. However, permissive hypoxemia remains investigational and should not yet be adopted into routine practice.
Efforts to move toward direct assessment of tissue oxygenation have also been explored as a goal-directed therapy target. A pilot trial used thenar tissue oxygen saturation to guide intraoperative dobutamine administration in high-risk abdominal surgery patients but found no statistically significant reduction in postoperative complications, a result the study’s authors attribute to limited statistical power and uncertainty regarding the optimal tissue oxygenation threshold (van Beest et al., 2014).
Perioperative oxygenation management is shifting away from uniform, high-concentration oxygen administration and toward individualized targets that account for patient age, comorbidity, and the physiological limitations of arterial oxygen tension as a proxy for tissue oxygen delivery.
References
- Habre, W., & Peták, F. (2014). Perioperative use of oxygen: variabilities across age. British Journal of Anaesthesia, 113(S2), ii26–ii36. https://doi.org/10.1093/bja/aeu380
- Martin, D. S., & Grocott, M. P. W. (2013). Oxygen therapy in critical illness: precise control of arterial oxygenation and permissive hypoxemia. Critical Care Medicine, 41(2), 423–432. https://doi.org/10.1097/CCM.0b013e31826a44f6
- Kabon, B., Nagele, A., Reddy, D., Eagon, C., Fleshman, J. W., Sessler, D. I., & Kurz, A. (2004). Obesity decreases perioperative tissue oxygenation. Anesthesiology, 100(2), 274–280. https://pmc.ncbi.nlm.nih.gov/articles/PMC1351046/
- van Beest, P. A., Vos, J. J., Poterman, M., Kalmar, A. F., & Scheeren, T. W. L. (2014). Tissue oxygenation as a target for goal-directed therapy in high-risk surgery: a pilot study. BMC Anesthesiology, 14, 122. https://doi.org/10.1186/1471-2253-14-122