A comparative study between serum lactate level versus change in end tidal carbon dioxide level regarding assessment of hemodynamic instability in intensive care unit patients after cardiac surgeries

ABSTRACT

Background

After cardiac surgeries, elevated lactate level is used as a marker of tissue hypoperfusion. Still, there is a search for other helpful markers of hemodynamic instability. Exhaled carbon dioxide has been recently studied as marker of cardiac output and tissue perfusion and may be considered a reliable alternative which is more convenient and real time.

Objectives

The main aim is to correlate between end tidal carbon dioxide (ETCO₂) and serum lactate level as indicators of hemodynamic instability in intensive care unit (ICU) patients after cardiac surgeries. The secondary objective is to correlate the measured parameters to the changes in the vital data and the resuscitation efforts.

Methods

A prospective cohort study that enrolled 51 adult patients admitted to ICU after cardiac surgeries. The serum lactate and ETCO₂ values as well as vital data and vasopressor doses were recorded on admission to ICU, after 2 hours and after 6 hours.

Results

The study shows insignificant weak positive correlation between Lactate and ETCO₂ levels at admission (r = 0.172, p value = 0.229), and insignificant negative weak correlation after 2 hours (r = -0.148, p value = 0.300) and after 6 hours (r = -0.235, p value = 0.096). Moreover, lactate level showed significant direct relation with the doses of vasopressors at admission, after 2 hours and after 6 hours postoperative (p value < 0.001 at all intervals). Whereas there was insignificant relation between ETCO₂ and doses of vasopressors at all intervals (p value = 0.23, 0.4 and 0.18 respectively).

Conclusion

In post-cardiac surgery ICU patients we detected no statistically significant relation between serum lactate and ETCO₂ as indicators of hemodynamic instability. The change in ETCO₂ over a period of time has failed so far to be of a beneficial value as a non-invasive real-time cardiac output monitoring parameter. In addition, serum lactate had strong correlation with changes in vital signs and resuscitation efforts.

KEYWORDS:

• Carbon dioxide
• cardiac surgery
• hemodynamic
• lactate

Disclosure statement

No potential conflict of interest was reported by the author(s).