Role of Arterial Serum Lactate as a Predictor of Undifferentiated Shock on Admission and its Outcome- A Cohort Study

Abstract

Introduction: Patients with elevated serum lactate levels may be at risk for considerable morbidity and mortality and require a prompt, thoughtful and systematic approach for diagnosis and treatment. Aim: To find an association of on admission arterial serum lactate with outcome in Intensive Care Unit (ICU) patients. Materials and Methods: This observational cohort study was conducted on 168 patients at Poona Hospital and Research Centre, Pune, India, between June 2018 to November 2019 after obtaining Institutional Ethical Clearance. The patients included were above 18 years of age who had Systolic Blood Pressure (SBP) <90 mmHg, Heart Rate (HR) >100/min and Respiratory Rate (RR) >20/min. The arterial serum lactate level were examined on the day of admission, 12 hours and 24 hours. The need of ionotropic support, duration of ICU stay and mortality in one month was noted. The primary outcome measures were to study the association of on admission arterial serum lactate level with a duration of ICU stay and in-hospital mortality, whereas the secondary outcome measure was to study the association of on admission arterial serum lactate with the requirement of ionotropic support. Analysis of data was done using Statistical Package for Social Sciences for Windows, version 20.0. Results: The incidence in-hospital mortality was 20 (22.7%) out of 88 and 3 (3.8%) out of 80 in patients whose serum lactate levels on admission were >36 mg/dL and ≤36 mg/dL, respectively (p-value=0.002). The median duration of ICU stay was six and three days in patients whose serum lactate levels on admission were >36 mg/dL and ≤36 mg/dL, respectively (p-value=0.001). A 87 (98.9%) patients whose serum lactate levels >36 mg/dL on admission had the higher requirement of inotropes as compared to 35 (50.7%) patients whose serum lactate levels were ≤36 mg/dL. The percentage of patients whose serum lactate level >36 mg/dL, had a significantly higher Quick Sequential Organ Failure Assessment (qSOFA) scores and higher Shock Index (SI). There was a statistically significant positive correlation between serum lactate levels and qSOFA score (r=0.555) and SI (r=0.559). Conclusion: Initial serum lactate level was associated with higher in-hospital mortality, the higher requirement of inotropic support and longer duration of ICU stay.