Time course of central venous-to-arterial carbon dioxide tension difference in septic shock patients receiving incremental doses of dobutamine
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To assess the time course of the central venous–arterial carbon dioxide tension difference (∆PCO2)—as an index of the carbon dioxide production (VCO2)/cardiac index (CI) ratio—in stable septic shock patients receiving incremental doses of dobutamine.
Twenty-two hemodynamically stable septic shock patients with no signs of global tissue hypoxia, as testified by normal blood lactate levels, were prospectively included. A dobutamine infusion was administered at a dose of up to 15 μg/kg/min in increments of 5 μg/kg/min every 30 min. Complete hemodynamic and gas measurements were obtained at baseline, and at each dose of dobutamine.
Dobutamine induced a significant dose-dependent increase of CI from 0 to 15 μg/kg/min (P < 0.001). Oxygen consumption (VO2) and VCO2 were progressively increased by dobutamine. These increases were more marked between 10 and 15 μg/kg/min (8.3 and 8.6 %, respectively) than between the lower doses. ∆PCO2 and oxygen extraction (EO2) significantly decreased between 0 (8.0 ± 2.0 mmHg and 43.8 ± 13.4 %, respectively) and 10 μg/kg/min of dobutamine (4.2 ± 1.6 mmHg and 28.9 ± 7.9 %, respectively), but remained unchanged from 10 to 15 μg/kg/min (5.4 ± 2.4 mmHg and 29.5 ± 8.2 %, respectively). The central venous oxygen saturation significantly (ScvO2) increased from 0 to 10 μg/kg/min and remained unchanged from 10 to 15 μg/kg/min. Time courses of ∆PCO2, ScvO2, and EO2 were linked therefore to the biphasic changes of VO2 and VCO2.
∆PCO2 is a good indicator of the change of VCO2 induced by dobutamine. Measurement of ∆PCO2, along with ScvO2 and EO2, may be presented as a useful tool to assess the adequacy of oxygen supply versus metabolic and oxygen demand.
KeywordsCentral venous-to-arterial carbon dioxide tension difference Cardiac index Dobutamine Stable septic shock Oxygen consumption CO2 production
American College of Chest Physicians
Acute Physiology and Chronic Health Evaluation
Chronic heart failure
Fractional inspired oxygen level
Mean arterial pressure
Central venous-to-arterial carbon dioxide tension difference
Mixed venous-to-arterial carbon dioxide tension difference
Society of Critical Care Medicine
Central venous oxygen saturation
Sequential Organ Failure Assessment
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