Conservative versus conventional oxygen therapy for cardiac surgical patients: A before-and-after study

Abstract

Avoiding hypoxaemia is considered crucial in cardiac surgery patients admitted to the intensive care unit (ICU). However, avoiding hyperoxaemia may also be important. A conservative approach to oxygen therapy may reduce exposure to hyperoxaemia without increasing the risk of hypoxaemia. Using a before-and-after design, we evaluated the introduction of conservative oxygen therapy (target SpO2 88%–92% using the lowest FiO2) for cardiac surgical patients admitted to the ICU. We studied 9041 arterial blood gas (ABG) datasets: 4298 ABGs from 245 ‘conventional’ and 4743 ABGs from 298 ‘conservative’ oxygen therapy patients. During mechanical ventilation (MV) and while in the ICU, compared to the conventional group, conservative group patients had significantly lower FiO2 exposure and PaO2 values ( P < 0.001 for each). Accordingly, using the mean PaO2 during MV, more conservative group patients were classified as normoxaemic (226 versus 62 patients, P < 0.01), fewer as hyperoxaemic (66 versus 178 patients, P < 0.01) and no patient in either group as hypoxaemic or severely hypoxaemic. Moreover, more ABG samples were hyperoxaemic or severely hyperoxaemic during conventional treatment ( P < 0.001). Finally, there was no difference in ICU or hospital length of stay, ICU or hospital mortality or 30-day mortality between the groups. Our findings support the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU after cardiac surgery.

Oxygen administration for postoperative surgical patients: a narrative review

“…To date, no RCT comparing liberal (conventional) and conservative oxygen therapy has focused on postoperative patients. To our knowledge, only one study, uncontrolled before-and-after design, has evaluated the introduction of conservative oxygen therapy (target SpO 2 of 88–92%) for cardiac surgical patients admitted to the intensive care unit [ 53 ]. Accordingly, this study found that conservative oxygen therapy could promote a significant decrease in hyperoxemia exposure without increasing the incidence of severe hypoxemia.…”

“…Although such findings might support the feasibility and physiological safety of conservative oxygen therapy in patients admitted to the intensive care unit after surgery, currently available studies do not provide sufficient evidence to guide practice regarding postoperative oxygen therapy. In addition, there might be a discrepancy in oxygen levels defined as liberal oxygen therapy between the clinical studies comparing two different oxygen targets [ 51 – 53 ] and in the levels reported to exert physiological harmful effects of supplemental oxygen and hyperoxemia [ 18 , 21 , 22 ]. So far, no clinical studies have examined the threshold for the onset of the association of hyperoxemia or hypoxemia with poor outcomes in patients postoperatively.…”

The effect of conservative oxygen therapy in reducing mortality in critical care patients: A systematic review and meta analysis

“…Conventional therapy would put 44.5% of the patients exposed to hyperoxemia, which is only about 11.4% in conservative oxygen group. 20 The disadvantages of hyperoxemia have been well demonstrated by many researches. First of all, high inspired oxygen concentrations would inhibit immune system: compromising the ability of macrophages, 23 suppressing the production of cytokine, 24 causing structural changes within alveolar macrophages and leading to serious impairment of their antimicrobial activity.…”

“…16,17,19−22 Three studies were randomized controlled trials (RCTs), 16,17,21 1 studies was retrospective nest cohort analysis, 19 and the other 2 studies was prospective before-after study. 20,22 Mortality was reported in 6 studies, among which hospital mortality and ICU mortality was reported in 3 studies, 16,19,20 28 day mortality was reported in 2 studies, 19,22 , 30 day mortality was reported in 1 study, 20 90 day mortality was reported in 2 studies, 17,21 180 day mortality was reported in 1 study. 17 ICU LOS was presented in 5 studies, 16,17,19−21 Hospital LOS was reported in 5 studies.…”

“…17 ICU LOS was presented in 5 studies, 16,17,19−21 Hospital LOS was reported in 5 studies. 16,17,19−21 MV hours was reported in 3 studies, 17,19,20 The rate of new organ failure was recorded in 2 studies, 16,22 the rate of new infection was recorded in 2 studies. 16,22 Details of each study were summarized in Table 1.…”