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Acute changes of metabolic parameters after fluid challenge

Introduction

The detection of heart response to fluid administration is still a challenge in clinical practice. Changes in metabolic parameters may be useful to detect changes in cardiac output (CO) after fluid expansion.

Methods

This is a prospective observational study in adult critically ill patients. CO was measured either by echocardiography or by a thermodilution method (PiCCO, Swan-Ganz catheter). Hemodynamic measurements and blood gas analysis were obtained before and after a fluid challenge with either 1,000 ml crystalloid or 500 ml colloid. Arterial and central venous blood gas samples were taken simultaneously. Oxygen delivery (DO2), oxygen consumption (VO2) and carbon dioxide production (VCO2) were calculated according to well-known formulas. Patients were divided into three groups (high responders, mild responders and nonresponders) according to their change in CO (>20%, 10 to 20%, <10%, respectively).

Results

We evaluated 27 patients, age 68 (95% CI: 61 to 74) and APACHE II score 22 (95% CI: 18 to 26). Seven patients were high responders, eight patients were moderate responders and 12 were nonresponders. DO2 was significantly increased in high responders (37 ± 35%, P < 0.01) as compared with moderate responders or nonresponders. Furthermore, nonresponders had a decrease in their DO2 (-10 ± 7%, P < 0.01), while moderate responders showed no change in their DO2 (1.6% ± 10, P = 0.73) after fluid challenge. We found no differences in changes in lactate levels and central venous oxygen saturation (ScvO2) between high responders, moderate responders and nonresponders. No differences in the changes of VCO2 or VO2/VCO2 ratio were found between high responders, mild responders and nonresponders too. Changes in DO2/VCO2 ratio were found to be significantly increased only in high responders (47 ± 73% vs. -14 ± 31%, P = 0.02) and not in mild responders (15 ± 54% vs. -14 ± 31%, P = 0.15) as compared with nonresponders.

Conclusion

Only significant increases of CO (>20%), after fluid administration, lead to improved oxygen delivery; DO2 may be decreased in nonresponders. The changes of ScvO2 and lactate levels do not track the changes of CO after fluid challenge. The DO2/VCO2 ratio may be a useful index to identify significant increases of CO after fluid challenge in cases where CO measurement is not feasible.

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Nguyen, T., Bels, D.D., Pustetto, M. et al. Acute changes of metabolic parameters after fluid challenge. Crit Care 19, P178 (2015). https://doi.org/10.1186/cc14258

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Keywords

  • Cardiac Output
  • Lactate Level
  • Oxygen Delivery
  • Metabolic Parameter
  • Fluid Administration