Objective To explore relationship between the change of serum N terminal brain natriuretic peptide (NT-proBNP) , central venous oxygen saturation (SCVO2 ) and venous-arterial partial pressure of carbon dioxide [P(v-a)CO2 ] levels and prognosis in elderly patients with septic shock .Methods 94 cases of elderly patients with septic shock ,treated from March 2015 to July 2016 in Intensive Care Unit (ICU) of our hospital ,were chosen as the observation group A ,another 80 cases of nonsevere sepsis patients were chosen as the observation group B ,and a total of 56 patients healthy volunteers with the physical examination at the same peri-od of time in our hospital as normal control group .The serum NT-proBNP level was detected by electrochemiluminescence immuno-assay ,and PvCO2 ,PaCO2 and SCVO2 levels were detected by blood gas analyzer .records of patients with central venous blood car-bon dioxide .The NT-proBNP and P (v-a) CO2 levels in the serum of the three groups were compared between the groups of pa-tients in the observation group (SCVO2 ) .Logistic regression analysis was used to analyze the prognostic factors in elderly patients with septic shock ,and the receiver operating characteristic curve (ROC) was used to analyze the predictive value of NT-proBNP ,P (v-a)SCVO2 and SCVO2 levels .Results The serum NT-proBNP level of the observation group A was higher than that in the the observation group B and the control group (P<0 .05) .The SCVO2 level of the A group was lower than that in the B group ,and the P(v-a)CO2 level of the A group was higher than that in the B group ,the difference was statistically significant (P<0 .05) .The age , NT-proBNP ,P(v-a)CO2 ,lactic acid level and APACHE II score in the death group were higher than those in the survival group , and the difference was statistically significant (P< 0 .05) .SCVO2 level in the death group was lower than that in the survival group ,and the difference was statistically significant (P<0 .05) .Logistic multivariate regression analysis showed that NT-proBNP , P(v-a)CO2 and SCVO2 levels were the risk factors for the prognosis of elderly patients with septic shock .ROC curve showed AUC and the sensitivity of P(v-a)CO2 were higher than those of NT-proBNP ,SCVO2 .Conclusion The levels of serum NT-proBNP ,SC-VO2 and P(v-a)CO2 are related to the prognosis of elderly patients with septic shock ,and P(v-a)CO2 has a high value in the prog-nosis of the patients with septic shock ,and has a good clinical value .