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Estimated respiratory quotient and venoarterial pCO2 difference are outcome markers in patients with left ventricular dysfunction submitted to coronary artery bypass surgery

Introduction

Experimental and clinical research has successfully evaluated the performance of the respiratory quotient as a useful marker of anaerobic metabolism in shock from different causes. The aim of the present study was to evaluate the estimated respiratory quotient and venoarterial pCO2 difference as suitable anaerobic metabolism signs and outcome markers in patients with left ventricular dysfunction undergoing coronary artery bypass surgery.

Methods

A prospective study including 87 patients with left ventricular dysfunction undergoing coronary artery bypass surgery with pump was performed from January 2006 to January 2008. Hemodynamic and metabolic parameters were obtained during five moments: after anesthesia induction and mechanical ventilation initiation (T0), at end of surgery (T1), at admission to the postsurgical ICU (T2), and 6 hours after (T3) and 12 hours after ICU admission (T4). The venoarterial carbon dioxide tension difference (ΔpCO2) and estimated respiratory quotient (eRQ) were also calculated. Postoperative outcomes were compared regarding clinical events and mortality.

Results

In patients with unfavorable postoperative evolution, the eRQ values as venoarterial ΔpCO2 presented significantly higher values at T4 compared with other groups (1.94 ± 0.9 vs. 1.43 ± 0.65, P < 0.05; 8.07 ± 3.24 vs. 5.66 ± 2.78, P < 0.05). Patients with unfavorable evolution had significant higher levels of arterial lactate concentration at 6 hours after ICU admission (4.30 ± 2.47 vs. 2.72 ± 1.48, P < 0.05). Stepwise logistic regression showed that a higher age, higher estimated respiratory quotient at T4, and higher lactate at T3 were all independently associated with unfavorable postoperative evolution (OR = 1.12; OR = 3.45; OR = 1.46).

Conclusion

In a population of patients with left ventricular dysfunction submitted to coronary artery bypass surgery, age, postoperative arterial lactate, eRQ and venoarterial ΔPCO2 after 12 hours of ICU admission are independent predictors of unfavorable outcome.

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Hajjar, L., Yamaguti, T., Galas, F. et al. Estimated respiratory quotient and venoarterial pCO2 difference are outcome markers in patients with left ventricular dysfunction submitted to coronary artery bypass surgery. Crit Care 13, P230 (2009). https://doi.org/10.1186/cc7394

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Keywords

  • Left Ventricular Dysfunction
  • Lactate Concentration
  • Unfavorable Outcome
  • Anaerobic Metabolism
  • Coronary Artery Bypass Surgery