RESUMEN
Objective To observe the effect of venous-to-arterial carbon dioxide difference to arterial-to-venous oxygen content difference [(Pv-aCO2)/(Ca-vO2)] ratio combined with critical ultrasound during the phases of fluid resuscitation of critical patients with septic shock. Methods Ninety-two critical patients with septic shock admitted to department of intensive care unit (ICU) of Anji County People's Hospital from July 2016 to December 2017 were enrolled, and they were divided into study group (42 cases) and control group (50 cases) according to random number table method. Two groups of patients were given supportive treatment such as antibiotic therapy, vasoactive drugs to support blood pressure, mechanical ventilation (MV), transfusion and nutritional therapy. The fluid resuscitation in patients of control group was guided through monitoring central venous pressure (CVP) and lactic acid (Lac). Patients in study group were given (Pv-aCO2)/(Ca-vO2) ratio combined with critical ultrasound directed therapy on the basis of the monitoring method of the control group. The differences in heart rate (HR), mean arterial pressure (MAP), CVP, Lac, central venous oxygen saturation (ScvO2), (Pv-aCO2)/(Ca-vO2) ratio, dosage of noradrenalin (NE), fluid intake in 6 hours, sequential organ failure assessment (SOFA) of 24 hours, time of MV, length of ICU stay, 28-day mortality rate, and incidence of pulmonary edema were compared. The correlation between (Pv-aCO2)/(Ca-vO2) ratio and Lac in study group was analyzed by Spearman analysis. Results In two groups, the HR, Lac, and (Pv-aCO2)/(Ca-vO2) ratio were significantly lower after 6 hours of treatment than those at admission, and MAP, CVP and ScvO2 were significantly increased compared with those at admission (all P < 0.05). The Lac and (Pv-aCO2)/(Ca-vO2) ratio in study group were significantly lower than those in control group at 6 hours after fluid resuscitation [Lac (mmol/L): 4.1±2.2 vs. 4.6±2.3, (Pv-aCO2)/(Ca-vO2) ratio:0.7±0.2 vs. 0.8±0.3, both P < 0.05], and MAP, CVP and ScvO2 were higher than those in control group [MAP (mmHg, 1 mmHg = 0.133 kPa): 78.6±10.3 vs. 71.4±11.5, CVP (mmHg): 13.2±5.1 vs. 9.8±4.4, ScvO2: 0.73±0.08 vs. 0.70±0.08, all P < 0.05]. In study group, the dosage of NE, fluid intake in 6 hours, and incidence of pulmonary edema were less than those in control group [dosage of NE (μg·kg-1·min-1): 0.22±0.16 vs. 0.43±0.11, fluid intake in 6 hours (mL): 1 290±518 vs. 1 560±426, incidence of pulmonary edema: 19.05% (8/42) vs. 32.00% (16/50)], 24 hours SOFA declined (9.3±3.2 vs. 12.6±3.8), and time of MV and length of ICU stay were obviously shortened [time of MV (hours):70.48±8.65 vs. 88.35±10.37, length of ICU stay (days): 7.28±2.07 vs. 8.42±1.51, all P < 0.05]. The 28-day mortality in study group had a trend of decrease compared with that in control group [40.5 % (17/42) vs. 44% (22/50)], but there was no statistical significant difference between two groups (P > 0.05). There was a significant positive correlation between the (Pv-aCO2)/(Ca-vO2) ratio and Lac in study group (r = 0.532, P < 0.001). Conclusion (Pv-aCO2)/(Ca-vO2) ratio combined with critical ultrasound can better guide the volume management of critical patients with septic shock, reduce the usage of vasoactive drugs and incidence of pulmonary edema, and decrease the time of MV and length of ICU stay.