Abstract Background: Shock is a life-threatening condition of circulatory failure that most commonly presents with hypo-tension, it can also be heralded by other vital sign changes or the presence of elevated serum lactate levels, it is important that the clinician rapidly identify the etiology so that appro-priate interventions and therapy. Aim of Study: To investigate the relationship between pCO2 gap and blood lactate concentration and 28 day mortality, as well as the prognostic usefulness of this relationship. Patients and Methods: The present studywasconducted on 30 adult septic shock patients at general intensive care unit Department of Ain Shams University Hospitals from December 2022 to May 2023, who were divided into two groups regarding pCO2 gap into normal and high gap after receiving early resuscitation and reaching ScvO2 >_70%. Results: There was a non-significant relation between SOFA score and pCO2 gap in first 12 hours of admission, but after 24 hours to end of study, patients with high pCO2 gap have higher SOFA score. An interesting result obtained in this study was finding that there was no significant relation between APACHE II and pCO2 gap on admission, but there was a significant increase in APACHE II score in high gap group after 48 hours till end of study. In the present study, there was a non-significant relation between incidence of in-hospital mortality rate and pCO2 gap among studied cases. There was a non-significant relation between 28-day mortality and pCO2 gap among studied cases. This study revealed that there was a significant relation between MAP and pCO2 gap only after 24 hours of admission and till the end of study, as MAP is lower in high gap group. This study revealed that there was a significant relation between HR and pCO2 gap only after 24 hours of admission and till the end of study, as HR is higher in high gap group. In the present study, there was a significant low Lactate in normal gap group after 6 hours of enrollment. This study revealed that there was a non-significant relation between CVP and pCO2 gap among studied cases.An interesting result obtained in this study that there was a non-significant relation between Scvo2 and pCO2 gap among studied cases. Conclusion: Targeting ScvO2 more than 70% alone may not be sufficient to monitor perfusion in septic shock patients, our results suggest that the persistence of high Pv-aCO2 during the early resuscitation of patients in septic shock is associated with significant higher multi organ dysfunction, higher lactate concentrations, lower MAP and poor outcomes, so the com-bination of PCO2 gap and ScvO2 may provide additional information about hemodynamics and the ability to clear lactate, Further research is required to determine the best use of this parameter as a treatment end-point; The predictive value for outcome of the central venous pCO2 difference is questionable but persistence of an increased central venous pCO2 difference after 24h of therapy seems to enhance the likelihood of bad outcome so the importance of PCO2 gap for outcomes might warrant its inclusion as a target in goal-directed treatment protocols.