[Central venous-to-arterial carbon dioxide difference in critically ill pediatric patients with septic shock]

To assess the value of central venous-to-arterial carbon dioxide difference [ P( cv-a) CO₂] in evaluation of disease severity and prognosis in children with septic shock who already had central venous oxygen saturation (ScvO₂) higher than 70% after early resuscitation.

In this prospective study, 48 septic shock children seen in Shanghai Children's Hospital, Shanghai Jiao Tong University were enrolled from Jun 2012 to May 2014. 36(75.0%) were male, 12 (25.0%) were female, the average age was (31.9 ± 24.5) months. The critically ill patients with septic shock were treated to achieve ScvO₂greater than 70% depending on early goal-directed therapy (EGDT). All patients were divided into two groups, based on P(cv-a)CO₂, low P(cv-a)CO₂group with P(cv-a)CO₂< 6 mmHg (1 mmHg = 0.133 kPa) and high P(cv-a)CO₂group with P(cv-a)CO₂≥ 6 mmHg. The parameters of hemodynamics including mean blood pressure (MAP), heart rate (HR), central venous pressure (CVP), perfusion-related parameters [ScvO₂, P(cv-a)CO₂, serum lactate (Lac), Lac clearance rate], pediatric critical illness score, PRISMIII score, and 28 days in-hospital mortality were recorded for all patients.

Of the 48 cases with septic shock whose ScvO₂was higher than 70%, 17 patients (35.4%) had high P(cv-a)CO₂( ≥ 6 mmHg) and 31 (65.6%) had lower P(cv-a)CO₂(<6 mmHg). There were no significant differences between the 2 groups of patients in age, PRISMIII score and PCIS (P > 0.05 ), but Lac and P(cv-a)CO₂values were significantly different ( P < 0.05). Low P(cv-a) CO₂group patients had lower 28 days mortality than high P(cv-a) CO₂group[11/17 vs. 32.3% (10/31), P < 0.05]; 24 h after resuscitation, compared with high P(cv-a) CO₂group, low P(cv-a) CO₂group patients had lower Lac values [(2.0 ± 1.3) vs.( 2.7 ± 1.2) mmol/L, P < 0.05]. Low P(cv-a) CO₂group patients had shorter duration of vasoactive drugs use [(16 ± 14) vs. (44 ± 21)h, P < 0.05], 24 h Lac clearance rate was significantly higher for low P(cv-a) CO₂group than for high P(cv-a) CO₂group[ (31 ± 10) % vs. (26 ± 6)%, P < 0.05].

When ScvO₂> 70% was achieved after early resuscitation in septic shock children, P(cv-a) CO₂is a sensitive biomarker to assess tissue perfusion, and high P(cv-a) CO₂group patients had poor outcome.