Sodium bicarbonate use and the risk of hypernatremia in thoracic aortic surgical patients with metabolic acidosis following deep hypothermic circulatory arrest

Objective: Metabolic acidosis after deep hypothermic circulatory arrest (DHCA) for thoracic aortic operations is commonly managed with sodium bicarbonate (NaHCO ₃ ). The purpose of this study was to determine the relationships between total NaHCO ₃ dose and the severity of metabolic acidosis, duration of mechanical ventilation, duration of vasoactive infusions, and Intensive Care Unit (ICU) or hospital length of stay (LOS). Methods: In a single center, retrospective study, 87 consecutive elective thoracic aortic operations utilizing DHCA, were studied. Linear regression analysis was used to test for the relationships between the total NaHCO ₃ dose administered through postoperative day 2, clinical variables, arterial blood gas values, and short-term clinical outcomes. Results: Seventy-five patients (86%) received NaHCO ₃. Total NaHCO ₃ dose averaged 136 ± 112 mEq (range: 0.0-535 mEq) per patient. Total NaHCO ₃ dose correlated with minimum pH (r = 0.41, P < 0.0001), minimum serum bicarbonate (r = -0.40, P < 0.001), maximum serum lactate (r = 0.46, P = 0.007), duration of metabolic acidosis (r = 0.33, P = 0.002), and maximum serum sodium concentrations (r = 0.29, P = 0.007). Postoperative hypernatremia was present in 67% of patients and peaked at 12 h following DHCA. Eight percent of patients had a serum sodium ≥ 150 mEq/L. Total NaHCO ₃ dose did not correlate with anion gap, serum chloride, not the duration of mechanical ventilator support, vasoactive infusions, ICU or hospital LOS. Conclusion: Routine administration of NaHCO ₃ was common for the management of metabolic acidosis after DHCA. Total dose of NaHCO ₃ was a function of the severity and duration of metabolic acidosis. NaHCO ₃ administration contributed to postoperative hypernatremia that was often severe. The total NaHCO ₃ dose administered was unrelated to short-term clinical outcomes.