Persistent Mitochondrial Dysfunction Linked to Prolonged Organ Dysfunction in Pediatric Sepsis.

Objectives: Limited data exist about the timing and significance of mitochondrial alterations in children with sepsis. We therefore sought to determine if alterations in mitochondrial respiration and content within circulating peripheral blood mononuclear cells were associated with organ dysfunction in pediatric sepsis. Design: Prospective observational study Setting: Single academic PICU. Patients: One-hundred sixty-seven children with sepsis/septic shock and 19 PICU controls without sepsis, infection, or organ dysfunction. Interventions: None. Measurements and Main Results: Mitochondrial respiration and content were measured in peripheral blood mononuclear cells on days 1-2, 3-5, and 8-14 after sepsis recognition or once for controls. Severity and duration of organ dysfunction were determined using the Pediatric Logistic Organ Dysfunction score and organ failure-free days through day 28. Day 1-2 maximal uncoupled respiration (9.7 +/- 7.7 vs 13.7 +/- 4.1 pmol O-2/s/10(6) cells; p = 0.02) and spare respiratory capacity (an index of bioenergetic reserve: 6.2 +/- 4.3 vs 9.6 +/- 3.1; p = 0.005) were lower in sepsis than controls. Mitochondrial content, measured by mitochondrial DNA/nuclear DNA, was higher in sepsis on day 1-2 than controls (p = 0.04) and increased in sepsis patients who had improving spare respiratory capacity over time (p = 0.005). Mitochondrial respiration and content were not associated with day 1-2 Pediatric Logistic Organ Dysfunction score, but low spare respiratory capacity was associated with higher Pediatric Logistic Organ Dysfunction score on day 3-5. Persistently low spare respiratory capacity was predictive of residual organ dysfunction on day 14 (area under the receiver operating characteristic, 0.72; 95% CI, 0.61-0.84) and trended toward fewer organ failure-free days although day 28 (beta coefficient, -0.64; 95% CI, -1.35 to 0.06; p = 0.08). Conclusions: Mitochondrial respiration was acutely decreased in peripheral blood mononuclear cells in pediatric sepsis despite an increase in mitochondrial content. Over time, a rise in mitochondrial DNA tracked with improved respiration. Although initial mitochondrial alterations in peripheral blood mononuclear cells were unrelated to organ dysfunction, persistently low respiration was associated with slower recovery from organ dysfunction.