Clinical Outcomes in Patients with Phosphate Abnormalities After Cardiac Surgery: A Retrospective Cohort Study.

Background: The clinical significance and incidence of phosphate abnormalities in cardiac surgery have not been investigated extensively. We hypothesize that phosphate abnormalities are associated with a longer time to tracheal extubation.

Methods: This was a single-center, retrospective cohort study in patients who underwent nontransplant cardiac surgery with cardiopulmonary bypass between August 2009 and December 2020. Serum phosphate levels were measured within 6 hours of arrival to the intensive care unit (ICU). Select clinical outcomes were extracted from an intramural database: time to tracheal extubation, hospital length of stay, and in-hospital mortality. The lactate level within 6 hours of arrival to the ICU was extracted as well.

Results: A total of 2659 patients were included. There were 502 (18.9%) patients who were found to be hypophosphatemic (phosphate <2.5 mg/dL), 1905 (71.6%) had normal phosphate levels (phosphate 2.5-4.5 mg/dL), and 252 (9.5%) were hyperphosphatemic (phosphate >4.5 mg/dL). Hyperphosphatemia was associated with 26% longer time to tracheal extubation (incident rate ratio, 1.26, 95% confidence interval [CI], 10%, 44%, P = .001), 37% longer hospital length of stay (acceleration factor = 0.63, 95% CI, -43% to -30%); P < .001), and increased in-hospital mortality (odds ratio, 4.0; 95% CI, 2.3-7.1; P < .001) when compared to patients with normal phosphate levels. These associations were not found for hypophosphatemia.

Conclusions: Hyperphosphatemia in the immediate postoperative period after cardiac surgery is associated with adverse clinical outcomes. Future studies will need to investigate if actively correcting the phosphate level has an impact on clinical outcomes.