Objective: To explore the prognostic value of arterial blood lactate ( Lac ) levels and lactate clearance rate ( LCR ) in the patients with septic shock.
Methods: A retrospective study was conducted. Clinical data of 94 septic patients admitted in the Department of Critical Care Medicine in Subei People's Hospital from January 2011 to June 2014 were analyzed. The arterial blood Lac levels at the moment of diagnosis of septic shock ( incipient value, 0 hour ) and early-stage after treatment ( 3, 6 and 24 hours ) were reviewed, and individual LCR was calculated at 3, 6, 24 hours for each patient. According to the outcome in intensive care unit ( ICU ), patients were divided into survival group ( n = 48 ) and death group ( n = 46 ). The Lac and LCR at different time points in two groups were analyzed, and the relationships between them and outcome were analyzed. The receiver-operating characteristic ( ROC ) curve was plotted to assess the value of Lac and LCR at different time points for predicting the outcome.
Results: Lac level after treatment in survival group was significantly lower than incipient value, but there was no obvious change in death group. Compared with death group, early Lac levels ( mmol/L ) in survival group were significantly reduced ( 0 hour: 3.80±2.14 vs. 5.75±3.21, 3 hours: 2.05±1.04 vs. 5.03±2.53, 6 hours: 1.80±0.77 vs. 4.40±2.02, 24 hours: 1.35±0.43 vs. 4.90±2.72, P<0.05 or P<0.01 ), the LCR was significantly increased [ 3 hours: 50.00 ( 72.35 )% vs. 13.51 ( 20.67 )%, 6 hours: 41.43 ( 58.42 )% vs. 22.00 ( 22.31 )%, 24 hours: 58.73 ( 29.94 )% vs. 18.92 ( 47.28 )%, P<0.05 or P<0.01 ]. The Lac levels at all time points were positively correlated with the outcome, and 6-hour and 24-hour LCR were negatively correlated with the outcome. According to the incipient Lac level, patients were divided into low Lac group ( Lac<2 mmol/L ), mild Lac group ( Lac 2-3 mmol/L ) and high Lac group ( Lac ≥ 4 mmol/L ). The mortality in low Lac group, mild Lac group, high Lac group was gradually increased [ 23.07% ( 6/26 ), 50.00% ( 8/16 ), 61.54% ( 32/52 ), χ(2) = 10.270, P = 0.006 ]. ROC curves demonstrated that the area under ROC curve ( AUC ) of 24-hour Lac was the largest, 0.944, and it was more sensitive and specific in the prognosis evaluation ( 100% and 78.3%, respectively ). According to the cut-off value of 24-hour Lac as 2.35 mmol/L, patients were divided into high Lac and low Lac groups, and mortality rate in high Lac group was significantly higher than that in low Lac group [ 100.0% ( 36/36 ) vs. 17.24% ( 10/58 ), χ(2) = 30.441,P = 0.000 ]. The AUC of 24-hour LCR was the largest, 0.865, and it was more sensitive and specific for the prognosis evaluation ( 83.3% and 91.3%, respectively ). According to the cut-off value of 24-hour LCR as 36.8%, patients were divided into high LCR group and low LCR group, and mortality rate in low LCR group was significantly higher than that in high LCR group [ 84.00% ( 42/50 ) vs. 9.09% ( 4/44 ), χ(2) = 26.278, P = 0.000 ].
Conclusions: Early high Lac in patients with septic shock prompts a poor prognosis, and 24-hour Lac levels and LCR are indicators of assessment of clinical therapeutic effect and prognosis of patients with septic shock.