Associations of serum lactate and lactate clearance with delirium in the early stage of ICU: a retrospective cohort study of the MIMIC-IV database

Delirium is a common problem in the intensive care unit (ICU). Accurate diagnosis is limited by the difficulty of communicating with mechanically ventilated patients and by lack of a validated delirium instrument for use in the ICU. To validate a delirium assessment instrument that uses standardized nonverbal assessments for mechanically ventilated patients and to determine the occurrence rate of delirium in such patients. Prospective cohort study testing the Confusion Assessment Method for ICU Patients (CAM-ICU) in the adult medical and coronary ICUs of a US university-based medical center. A total of 111 consecutive patients who were mechanically ventilated were enrolled from February 1, 2000, to July 15, 2000, of whom 96 (86.5%) were evaluable for the development of delirium and 15 (13.5%) were excluded because they remained comatose throughout the investigation. Occurrence rate of delirium and sensitivity, specificity, and interrater reliability of delirium assessments using the CAM-ICU, made daily by 2 critical care study nurses, compared with assessments by delirium experts using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria. A total of 471 daily paired evaluations were completed. Compared with the reference standard for diagnosing delirium, 2 study nurses using the CAM-ICU had sensitivities of 100% and 93%, specificities of 98% and 100%, and high interrater reliability (kappa = 0.96; 95% confidence interval, 0.92-0.99). Interrater reliability measures across subgroup comparisons showed kappa values of 0.92 for those aged 65 years or older, 0.99 for those with suspected dementia, or 0.94 for those with Acute Physiology and Chronic Health Evaluation II scores at or above the median value of 23 (all P<.001). Comparing sensitivity and specificity between patient subgroups according to age, suspected dementia, or severity of illness showed no significant differences. The mean (SD) CAM-ICU administration time was 2 (1) minutes. Reference standard diagnoses of delirium, stupor, and coma occurred in 25.2%, 21.3%, and 28.5% of all observations, respectively. Delirium occurred in 80 (83.3%) patients during their ICU stay for a mean (SD) of 2.4 (1.6) days. Delirium was even present in 39.5% of alert or easily aroused patient observations by the reference standard and persisted in 10.4% of patients at hospital discharge. Delirium, a complication not currently monitored in the ICU setting, is extremely common in mechanically ventilated patients. The CAM-ICU appears to be rapid, valid, and reliable for diagnosing delirium in the ICU setting and may be a useful instrument for both clinical and research purposes.

Serial lactate concentrations can be used to examine disease severity in the intensive care unit. This study examines the clinical utility of the lactate clearance before intensive care unit admission (during the most proximal period of disease presentation) as an indicator of outcome in severe sepsis and septic shock. We hypothesize that a high lactate clearance in 6 hrs is associated with decreased mortality rate. Prospective observational study. An urban emergency department and intensive care unit over a 1-yr period. A convenience cohort of patients with severe sepsis or septic shock. Therapy was initiated in the emergency department and continued in the intensive care unit, including central venous and arterial catheterization, antibiotics, fluid resuscitation, mechanical ventilation, vasopressors, and inotropes when appropriate. Vital signs, laboratory values, and Acute Physiology and Chronic Health Evaluation (APACHE) II score were obtained at hour 0 (emergency department presentation), hour 6, and over the first 72 hrs of hospitalization. Therapy given in the emergency department and intensive care unit was recorded. Lactate clearance was defined as the percent decrease in lactate from emergency department presentation to hour 6. Logistic regression analysis was performed to determine independent variables associated with mortality. One hundred and eleven patients were enrolled with mean age 64.9 +/- 16.7 yrs, emergency department length of stay 6.3 +/- 3.2 hrs, and overall in-hospital mortality rate 42.3%. Baseline APACHE II score was 20.2 +/- 6.8 and lactate 6.9 +/- 4.6 mmol/L. Survivors compared with nonsurvivors had a lactate clearance of 38.1 +/- 34.6 vs. 12.0 +/- 51.6%, respectively (p =.005). Multivariate logistic regression analysis of statistically significant univariate variables showed lactate clearance to have a significant inverse relationship with mortality (p =.04). There was an approximately 11% decrease likelihood of mortality for each 10% increase in lactate clearance. Patients with a lactate clearance> or =10%, relative to patients with a lactate clearance <10%, had a greater decrease in APACHE II score over the 72-hr study period and a lower 60-day mortality rate (p =.007). Lactate clearance early in the hospital course may indicate a resolution of global tissue hypoxia and is associated with decreased mortality rate. Patients with higher lactate clearance after 6 hrs of emergency department intervention have improved outcome compared with those with lower lactate clearance.

Abstract Objective Lack of reproducibility in medical studies is a barrier to the generation of a robust knowledge base to support clinical decision-making. In this paper we outline the Medical Information Mart for Intensive Care (MIMIC) Code Repository, a centralized code base for generating reproducible studies on an openly available critical care dataset. Materials and Methods Code is provided to load the data into a relational structure, create extractions of the data, and reproduce entire analysis plans including research studies. Results Concepts extracted include severity of illness scores, comorbid status, administrative definitions of sepsis, physiologic criteria for sepsis, organ failure scores, treatment administration, and more. Executable documents are used for tutorials and reproduce published studies end-to-end, providing a template for future researchers to replicate. The repository’s issue tracker enables community discussion about the data and concepts, allowing users to collaboratively improve the resource. Discussion The centralized repository provides a platform for users of the data to interact directly with the data generators, facilitating greater understanding of the data. It also provides a location for the community to collaborate on necessary concepts for research progress and share them with a larger audience. Consistent application of the same code for underlying concepts is a key step in ensuring that research studies on the MIMIC database are comparable and reproducible. Conclusion By providing open source code alongside the freely accessible MIMIC-III database, we enable end-to-end reproducible analysis of electronic health records.