A female 50-year-old patient is undergoing induction of general anesthesia for gastric bypass surgery. Which of the following intraoperative measures would have the MOST impact on preventing the development of postoperative pulmonary atelectasis?A. Preoxygenation with a PEEP of 8 cm H2O
Correct Answer: D
Perioperative hypoxemia is a risk factor for perioperative mortality and for several perioperative complications including cardiac ischemia and delirium leading to increased postoperative length of stay. Perioperative atelectasis is one of the main causes of hypoxemia in surgical patients, with their prevention being mandatory and requiring a multistep approach in all phases of the perioperative period. After surgery, optimal pain control without residual anesthesia together with CPAP and postural changes are all fundamental to pursue this target.
A fundamental mechanism leading to postoperative atelectasis is hyperoxic reabsorption of gases from the alveolar space into circulation. Extubation with a FiO2 of 1.0 has been shown to potentially jeopardize all previous intraoperative efforts to prevent and/or reduce atelectasis, even if a recruitment maneuver is performed prior to extubation. Keeping the lowest FiO2 compatible with the patient’s oxygenation requirements, not only before extubation but throughout the surgery, prevents atelectasis. Clinical studies evaluating fixed-ruled PEEP strategies have shown contradictory results, and thus there is no specific recommendation on the amount of PEEP. High PEEP has theoretical advantages in terms of protection from atelectasis. Studies comparing preset values of low versus high PEEP for intraoperative ventilation yield contradictory results. Preoxygenation with PEEP has a demonstrated role in reducing the incidence of postoperative atelectasis, yet it is not the most impactful strategy among those listed. Using an FiO2 of less than 60% during preoxygenation, induction, and intubation has a dramatic effect leading in many cases to the absence of intraoperative atelectasis. However, this strategy cannot be implemented for safety reasons, especially since this will decrease the duration of safe apnea period.