Effects of respiratory rate on venous-to-arterial CO2 tension difference in septic shock patients undergoing volume mechanical ventilation

Abstract

Background: To explore the effects of the respiratory rate (RR) on the venous-to-arterial CO 2 tension difference (gapCO 2 ) in septic shock patients undergoing volume mechanical ventilation. Methods:Adult patients with septic shock underwent volume mechanical ventilation between October 2015 and October 2016. RR was started at 10 breaths/min, and 2 breaths/min were added every 60 min until 16 breaths/min was reached. At every point, central venous and arterial blood gas measurements were obtained simultaneously.Results: In this study, gapCO 2 induced by hyperventilation significantly increased, while the central venous carbon dioxide pressure (PvCO 2 ) and the partial pressure of CO 2 (PaCO 2 ) in arteries decreased. The decreasing trend of the PaCO 2 was more obvious than that of the PvCO 2 . HCO 3 − and ctCO 2 were markedly decreased, when the RR was increased (P < 0.05). Central venous oxygen saturation (S cv O 2 ) had a decreasing trend between 14 (77.1 ± 8.3%) and 16 (75.2 ± 8.7%) breaths/min; however, the difference was not significant. Conclusions:In septic patients undergoing ventilation, respiratory alkalosis induced by hyperventilation caused an increase in the gapCO 2 . Clinicians should cautiously interpret the gapCO 2 in hemodynamically stable ventilated septic shock patients and its relationship with low cardiac output and inadequate perfusion.

Embracing a New Evidence-Based Thought Paradigm of Sepsis

“…Current guidelines dictate that clinicians utilize lactate clearance and central venous oxygen saturation as fundamental measures of tissue perfusion 26,27 . However, when central venous oxygen saturation and lactate values continue to remain elevated in the presence of adequate resuscitation, clinicians must consider other modalities to address this conundrum 28,29 . Having a broader understanding of these dynamic measures can help clinicians consider other possibilities of persistent hypoxia and poor tissue perfusion.…”

The Evolution of Central Venous-to-arterial Carbon Dioxide Difference (PCO2 Gap) during Resuscitation Affects ICU Outcomes: A Prospective Observational Study

“…Despite these findings, PCO 2 gap remains a clinically useful diagnostic tool for detecting tissue perfusion derangements. 29 , 30 We tried to analyze if high PCO 2 gap is a good discriminator to predict mortality. The AUROC (AUC = 0.76) at T6 and T12 suggests a moderate discriminatory ability.…”