End-tidal carbon dioxide underestimates plasma carbon dioxide during emergent trauma laparotomy leading to hypoventilation and misguided resuscitation: A Western Trauma Association Multicenter Study

Abstract

BACKGROUND End-tidal carbon dioxide (ETCO2) is routinely used during elective surgery to monitor ventilation. The role of ETCO2 monitoring in emergent trauma operations is poorly understood. We hypothesized that ETCO2 values underestimate plasma carbon dioxide (pCO2) values during resuscitation for hemorrhagic shock. METHODS Multicenter trial was performed analyzing the correlation between ETCO2 and pCO2 levels. RESULTS Two hundred fifty-six patients resulted in 587 matched pairs of ETCO2 and pCO2. Correlation between these two values was very poor with an R 2 of 0.04. 40.2% of patients presented to the operating room acidotic and hypercarbic with a pH less than 7.30 and a pCO2 greater than 45 mm Hg. Correlation was worse in patients that were either acidotic or hypercarbic. Forty-five percent of patients have a difference greater than 10 mm Hg between ETCO2 and pCO2. A pH less than 7.30 was predictive of an ETCO2 to pCO2 difference greater than 10 mm Hg. A difference greater than 10 mm Hg was predictive of mortality independent of confounders. CONCLUSION Nearly one half (45%) of patients were found to have an ETCO2 level greater than 10 mm Hg discordant from their PCO2 level. Reliance on the discordant values may have contributed to the 40% of patients in the operating room that were both acidotic and hypercarbic. Early blood gas analysis is warranted, and a lower early goal of ETCO2 should be considered. LEVEL OF EVIDENCE Therapeutic, level IV.

Cerebral blood flow velocity during simultaneous changes in mean arterial pressure and cardiac output in healthy volunteers

“…In the third case, a reduction in ETCO 2 does not need to be associated with a reduction in PaCO 2 . Several studies indicate that this mechanism partly explains the reduction in ETCO 2 with experimental (Dubin et al 2000 ) and clinical hypovolemia (Campion et al 2019 ; Tyburski et al 2003 ), questioning the assumption that ETCO 2 can substitute PaCO 2 . This finding is supported by studies applying orthostatic stress, where both LBNP (Zhang and Levine 2007 ) and head-up-tilt (Immink et al 2006 ; Serrador et al 2006 ) induced greater reductions in ETCO 2 than PaCO 2 .…”

Liberal Oxygen with Unreliable Unpredictable Flowrate Is the Root Cause of Unexplained Physiological Events in Combat aircraft

“…There is poor correlation between end-tidal expired CO2 and PaCO2 because of the impacts of physiologic buffer systems. (Campion, 2019) Hyperkalemia (elevated potassium) is frequently used as a surrogate biomarker of metabolic acidosis, but there is poor correlation between hyperkalemia and the respiratory acidosis that exists in hypercarbia. (Weinberg, 2019) It has also been noted that confusion and disorientation can continue despite full arterial oxygen saturation.…”

CO₂ Narcosis as a Root Cause of Unexplained Physiological Events in High Performance Aircraft

“…There is poor correlation between end-tidal expired CO2 and PaCO2 because of the impacts of physiologic buffer systems [8] Hyperkalemia (elevated potassium) is frequently used as a surrogate marker of metabolic acidosis, but there is poor correlation between hyperkalemia and the respiratory acidosis that exists in hypercarbia. [43] It has also been noted that confusion and disorientation remain despite full arterial oxygen saturation.…”