What is the purpose of the BicarbiCU1 trial regarding sodium bicarbonate (NaHCO3) administration in critically ill patients with metabolic acidosis?

The BICAR-ICU Trial: Key Findings

The BICAR-ICU trial was a landmark French multicenter randomized controlled trial that evaluated whether sodium bicarbonate infusion improves clinical outcomes in critically ill patients with severe metabolic acidosis (pH ≤7.20), finding no overall benefit on the primary composite outcome but demonstrating significant mortality reduction in patients with acute kidney injury. 1

Trial Design and Population

• The study enrolled 389 ICU patients across 26 French centers between May 2015 and May 2017 1
• Inclusion criteria required pH ≤7.20, PaCO₂ ≤45 mm Hg, bicarbonate ≤20 mmol/L, and either a Sequential Organ Failure Assessment (SOFA) score ≥4 or lactate ≥2 mmol/L 1
• Patients were randomized 1:1 to receive either no bicarbonate (control) or 4.2% intravenous sodium bicarbonate infusion to maintain pH >7.30 1
• The bicarbonate protocol recommended 125-250 mL infusions over 30 minutes, with a maximum of 1000 mL within 24 hours 1

Primary Outcome Results

• The primary composite outcome (death by day 28 or presence of organ failure at day 7) occurred in 71% of control patients versus 66% of bicarbonate patients, showing no significant difference (p=0.24) 1
• Day 28 mortality showed a non-significant trend favoring bicarbonate therapy: 46% in controls versus 55% survival in the bicarbonate group (p=0.09) 1

Critical Subgroup Finding: Acute Kidney Injury

• In the prespecified subgroup of patients with AKIN score 2 or 3 (moderate to severe acute kidney injury), bicarbonate therapy significantly improved day 28 survival: 37% in controls versus 54% in the bicarbonate group (p=0.0283) 1
• This finding aligns with current guidelines from the Society of Critical Care Medicine and European Society of Intensive Care Medicine, which note insufficient evidence for bicarbonate in metabolic acidosis without acute kidney injury 2
• Subsequent systematic reviews confirmed that bicarbonate therapy yields survival improvement specifically in patients with accompanying acute kidney injury 3

Safety Profile

• Metabolic alkalosis, hypernatremia, and hypocalcemia occurred more frequently in the bicarbonate group 1
• These adverse effects are consistent with known complications noted by the Society of Critical Care Medicine, including sodium/fluid overload, increased lactate and PaCO₂, and decreased ionized calcium 2
• No life-threatening complications were reported in the trial 1

Clinical Implications

• The trial supports selective use of bicarbonate therapy rather than routine administration in all patients with severe metabolic acidosis 1
• For patients with severe metabolic acidosis but without acute kidney injury, the evidence remains insufficient to recommend routine bicarbonate administration 2
• The Surviving Sepsis Campaign guidelines suggest against using sodium bicarbonate for sepsis-related lactic acidemia with pH ≥7.15, though the BICAR-ICU trial included more severe acidosis (pH ≤7.20) 2