To investigate the association between different doses of norepinephrine and the implementation of enteral nutrition, and to analyze the risk factors and predictors of prognosis in septic shock patients receiving enteral nutrition.

Fifty-seven septic shock patients admitted to the ICU of the Second Affiliated Hospital of Nanjing Medical University between December 2021 and August 2022 were selected and divided into a low-dose group (n = 38) and a high-dose group (n = 19) according to a norepinephrine equivalent dose (NEQ) < 0.14 μg·kg^-1·min^-1 or ≥ 0.14 μg·kg^-1·min^-1. General data of patients were collected, and the differences in superior mesenteric artery (SMA) Doppler parameters on the first and fifth days of enteral nutrition application were compared between the two groups. Factors associated with hemodynamic differences in the SMA were analyzed using multiple linear regression on the fifth day of enteral nutrition application. Septic shock patients were divided into survival (n = 41) and death (n= 16) groups according to 28-d mortality, and the Cox proportional hazard regression model was used to analyze independent risk factors affecting the outcome of septic shock patients who received enteral nutrition. A receiver operating characteristic (ROC) curve was used to evaluate the predictive value of mean arterial pressure (MAP) /NEQ for the outcome of patients with septic shock. Kaplan-Meier survival curves were used to compare the survival condition of patients with septic shock in the high MAP/NEQ and low MAP/NEQ groups.

The peak systolic velocity (PSV), end-diastolic velocity (EDV), and blood flow (Q) of patients in the low-dose group on the fifth day of enteral nutrition increased significantly compared to the first day (all P < 0.05). The EDV and Q of patients in the high-dose group increased significantly on the fifth day compared to the first day, while the pulsatility index (PI) decreased significantly (all P < 0.05). The 28-d mortality and feeding intolerance in the high-dose group increased significantly compared to the low-dose group, while the length of ICU stay shortened significantly (all P < 0.05). Multiple linear regression analysis showed that NEQ and MAP/NEQ were negatively correlated with PSV and EDV, and positively correlated with PI (all P < 0.05). MAP/NEQ was an independent protective factor affecting the prognosis of septic shock patients receiving enteral nutrition [hazard ratio (HR) = 0.9995, 95% confidence interval (CI) (0.9991, 0.9999), P = 0.047]. The area under the curve for MAP/NEQ obtained by the ROC curve was 0.716 [95%CI (0.582, 0.828)], and the optimal cutoff value was 1 116.667 mmHg/(μg·kg^-1·min^-1). According to this value, 57 patients with septic shock were divided into a high MAP/NEQ group [MAP/NEQ > 1 116.667 mmHg/(μg·kg^-1·min^-1), 36 cases] and a low MAP/NEQ group [MAP/NEQ ≤ 1 116.667 mmHg/(μg·kg^-1·min^-1), 21 cases]. The sequential organ failure assessment score, heart rate, NEQ, nutrition risk screening 2002 score, and 28-d mortality of patients in the high MAP/NEQ group were significantly lower than those in the low MAP/NEQ group, while the ICU stay was significantly longer (all P < 0.05). The Kaplan-Meier survival curve showed that the 28-d cumulative survival rate of the high MAP/NEQ group was significantly higher than that of the low MAP/NEQ group (χ² = 14.300, P < 0.001).

MAP/NEQ is an independent protective factor affecting the outcome of septic shock patients who receive enteral nutrition. MAP/NEQ > 1 116.667 mmHg/(μg·kg^-1·min^-1) may improve their prognosis.