Lactic Acidosis in the Setting of Severe Hypophosphatemia After High-Dose Insulin Infusion

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.

The Association Between Hypophosphatemia and Lactic Acidosis After Cardiac Surgery With Cardiopulmonary Bypass: A Retrospective Cohort Study

OBJECTIVES

The clinical significance of hypophosphatemia in cardiac surgery has not been investigated extensively. The aim of this study was to evaluate the association of postoperative hypophosphatemia and lactic acidosis in cardiac surgery patients at the time of intensive care unit (ICU) admission.

DESIGN

A retrospective cohort study.

SETTING

At a single academic center.

PARTICIPANTS

Patients who underwent nontransplant cardiac surgery with cardiopulmonary bypass between August 2009 and December 2020.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Serum phosphate and lactate levels were measured upon ICU admission in patients undergoing nontransplant cardiac surgery with cardiopulmonary bypass. There were 681 patients in the low-phosphate (<2.5 mg/dL) group and 2,579 patients in the normal phosphate group (2.5-4.5 mg/dL). A higher proportion of patients in the low phosphate group (26%; 179 of 681; 95% CI: 23-30) had severe lactic acidosis compared to patients in the normal phosphate group (16%; 417 of 2,579; 95% CI: 15-18). In an unadjusted logistic regression model, patients in the low phosphate group had 1.9-times the odds of having severe lactic acidosis (serum lactate ≥4.0 mmol/L) when compared to patients in the normal phosphate group (95% CI: 1.5-2.3), and still 1.4-times the odds (95% CI: 1.1-1.7) after adjusting for several possible confounders.

CONCLUSIONS

Hypophosphatemia is associated with lactic acidosis in the immediate postoperative period in cardiac surgery patients. Future studies will need to investigate it as a potential treatment target for lactic acidosis.