Svo2
A 35-year-old woman with pancreatitis and ARDS experiences a progressively worsening oxygenation status. The care team decides to replace her PA catheter with a Svo2 catheter to better monitor and manage her care. Once the Svo2 catheter is in place and calibrated, it is noted that her Svo2 is only 55%. A quick assessment of oxygen supply variables yields the following:
Given the high levd of ventilator support already in place, the team felt that augmentation of oxygen-carrying capacity with transfusions of packed red blood cells (PRBCs) would provide the greatest boost to oxygenation. Following the infusion of 2 U of PRBC, the Svo2 increased to 70%. Over the course of the next few days, decreases in ventilator support were evaluated by monitoring changes in Svo2 in conjunction with other supply-side variables.
On day 6, she became increasingly agitated and her Svo2 decreased to 60%. She was febrile and her sputum was noted to be purulent appearing. Sputum cultures were obtained and other reasons for the agitation were also considered. A STAT chest radiograph was obtained which ruled out pneumothorax, and an arterial blood gas revealed a Paco2 of 45 mm Hg, a Pao2 of 55 mm Hg, and a Sao2 of 88%. Her ventilator settings were SIMV of 12/min (spontaneous rate was 10 above the ventilation), Fio2 of 0.45, PEEP of 5 cm H20, Hct of 29%, and CO of 6 Umin.
The team recognized that both supply and demand needed to be addressed to optimize her oxygenation. Thus, ventilator settings were increased as follows:
What factors contn"huted to the low Svo2 when the monitor was fust placed?
What&ctors contributed to the change in Svo, on day 6?