Hypoxemic Episodes of Patients in a Postanesthesia Care Unit: Decreasing the Incidence of Postoperative Hypoxemia

Why was the incidence of oxygen desaturation similar to other studies in which no oxygen was administered? Possibilities include inadequate oxygen delivery, increased oxygen requirements in the patient population, or refractory causes of the relative hypoxemia. Oxygen delivery to the patient by aerosol face tent can be inefficient. The patients breathing pattern, tidal volume, mask position, room air entrain-ment, as well as the oxygen concentration and flow from the nebulizer all affect the true inspired concentration reaching the patients airway. A higher incidence of shivering could have increased oxygen requirements, but was not present. There were no patients with apparent sepsis and none was febrile. There was not a disproportionate number of morbidly obese patients or patients with airway obstruction who were predisposed to airway obstruction or sleep apnea. The most likely cause underlying the higher than expected incidence of oxygen desaturations despite oxygen therapy was that the desaturations were primarily secondary to causes refractory to routine oxygen administration.
Nunn and Payne believed that postoperative hypoxemia was primarily due to shunts and ventilation-perfusion mismatching. Although ventilation-perfu-sion inhomogeneity will respond to oxygen therapy, the response of hypoxemia secondary to shunts is limited. The relative contribution of these physiologic abnormalities to hypoxemia may vary from patient to patient. The fact that previous investigators have not utilized continuous oxygen saturation monitoring allowed many episodes of desaturation to be missed. When a single arterial blood gas determination or single spot checks or short, timed checks of saturation are made by pulse oximeter, improved oxygenation responses to oxygen can be documented, but then again, recurrent desaturations are missed. Nervous System
What can be done to further decrease postoperative decreases in oxygen saturation? The different methods of oxygen delivery to patients, such as aerosol mask, nonrebreathing masks, or combining nasal cannula oxygen with face tent or aerosol mask, need to be compared to determine efficacy. Can patient care can be improved by titration of postoperative oxygen administration to individual effect, administration of oxygen during transport to the RR, individualizing patient care to maximize benefits of position, and continuous oxygen saturation monitoring with a high index of suspicion that desaturations will occur? These questions and many more are not yet answered.
Despite postoperative oxygen administration by face tent, 25 percent of patients in the PAR still were demonstrated to have oxygen desaturations below 92 percent. Long-term patient follow-up for oxygen saturation levels and desaturation side effects was not done and possible interactions, such as a relationship between recurrent desaturations and postoperative pulmonary complications or length of hospitalization, were not evaluated. Rosenberg et al postulated that late postoperative desaturations may be important in the pathogenesis of cardiac dysfunction. Further studies are needed to delineate the side effects of postoperative desaturation, to compare effectiveness of the different modes of oxygen delivery in the early postoperative period, and to document the occurrence of desaturations outside the recovery room and the duration of oxygen therapy required.

This entry was posted in Hypoxemic Episodes and tagged abdominal surgery, anesthesia, hypoxemia, oxygen saturation, postoperative hypoxemia.