Hypophosphataemia after cardiopulmonary bypass – Incidence and clinical significance, a South African perspective

Abstract

Background: Hypophosphataemia is well-known in the intensive care units (ICU), for example, in refeeding syndrome. There is limited research available for hypophosphataemia in the ‘post-cardiac surgery’ population. Objectives: Defining the incidence of hypophosphataemia after cardiopulmonary bypass, in a South African population. Secondary objectives include the clinical implication of hypophosphataemia on duration of mechanical ventilation, ICU stay, and cardioactive drug support; and possible associations between demographic variables, intraoperative variables (including cardioplegic solution), and the postoperative phosphate levels. Methods: This was a single-centre, non-blinded, prospective cohort analytical study at an academic hospital, in patients presenting for open cardiac surgery. Over a one-year period, 101 patients were included. Preoperative variables included all the factors of the EuroSCORE II risk evaluation score. Intraoperative variables recorded were drug and blood product administration, cardioplegic solution and cardiopulmonary bypass-related variables. Postoperatively, serum phosphate levels were taken daily and postoperative care measures, such as duration of cardioactive drug support, mechanical ventilation, and ICU stay, were recorded. Results: The incidence of hypophosphataemia, immediately postoperative, was 12.6% (95% confidence interval [CI] 6.7–21.0%) and peaked on Day 3 at 29.0% (95% CI 20.1–39.4%). New onset hypophosphataemia at any stage during the ICU stay was 52.6% (95% CI 42.1–63.0%). No significant associations between hypophosphataemia and secondary objectives were found. Conclusion: Hypophosphataemia was common with an incidence higher than expected. This did not translate into a clinical effect, as the degree was usually mild (0.66–0.79 mmol/L).