Determining the clinical value of lactate in surgical patients on the intensive care unit

Continuous and Non-Invasive Lactate Monitoring Techniques in Critical Care Patients

Lactate, once merely regarded as an indicator of tissue hypoxia and muscular fatigue, has now gained prominence as a pivotal biomarker across various medical disciplines. Recent research has unveiled its critical role as a high-value prognostic marker in critical care medicine. The current practice of lactate detection involves periodic blood sampling. This approach is invasive and confined to measurements at six-hour intervals, leading to resource expenditure, time consumption, and patient discomfort. This review addresses non-invasive sensors that enable continuous monitoring of lactate in critical care patients. After the introduction, it discusses the iontophoresis system, followed by a description of the structural materials that are universally employed to create an interface between the integumentary system and the sensor. Subsequently, each method is detailed according to its physical principle, outlining its advantages, limitations, and pertinent aspects. The study concludes with a discussion and conclusions, aiming at the design of an intelligent sensor (Internet of Medical Things or IoMT) to facilitate continuous lactate monitoring and enhance the clinical decision-making support system in critical care medicine.

The physiology of failure: Identifying risk factors for mortality in emergency general surgery patients using a regional health system integrated electronic medical record

BACKGROUND

Emergency general surgery (EGS) patients have increased mortality risk compared with elective counterparts. Recent studies on risk factors have largely used national data sets limited to administrative data. Our aim was to examine risk factors in an integrated regional health system EGS database, including clinical and administrative data, hypothesizing that this novel process would identify clinical variables as important risk factors for mortality.

METHODS

Our nine-hospital health system's billing data were queried for EGS International Classification of Disease codes between 2013 and 2018. Codes were grouped by diagnosis, and urgent or emergent encounters were included and merged with electronic medical record clinical data. Outcomes assessed were inpatient and 1-year mortality. Standard and multivariable statistics evaluated factors associated with mortality.

RESULTS

There were 253,331 EGS admissions with 3.6% inpatient mortality rate. Patients who suffered inpatient and 1-year mortality were older, more likely to be underweight, and have neutropenia or elevated lactate. On multivariable analysis for inpatient mortality: age (odds ratio [OR], 1.7-6.7), underweight body mass index (OR, 1.6), transfer admission (OR, 1.8), leukopenia (OR, 2.0), elevated lactate (OR, 1.8), and ventilator requirement (OR, 7.1) remained associated with increased risk. Adjusted analysis for 1-year mortality demonstrated similar findings, with highest risk associated with older age (OR, 2.8-14.6), underweight body mass index (OR, 2.3), neutropenia (OR, 2.0), and tachycardia (OR, 1.7).

CONCLUSION

After controlling for patient and disease characteristics available in administrative databases, clinical variables remained significantly associated with mortality. This novel yet simple process allows for easy identification of clinical data points imperative to the study of EGS diagnoses that are critical in understanding factors that impact mortality.

LEVEL OF EVIDENCE

Prognostic and Epidemiologic; Level III.

Association between Intraoperative Hyperlactatemia and Myocardial Injury after Noncardiac Surgery

Background: Oxygen demand–supply mismatch is supposed to be one of the major causes of myocardial injuries after noncardiac surgery (MINS). Impaired tissue oxygenation during the surgery can lead to intraoperative hyperlactatemia. Therefore, we aimed to evaluate the relationship between intraoperative lactate level and MINS. Methods: A total of 1905 patients divided into groups according to intraoperative hyperlactatemia: 1444 patients (75.8%) into normal (≤2.2 mmol/L) and 461 patients (24.2%) into hyperlactatemia (>2.2 mmol/L) groups. The primary outcome was the incidence of MINS, and all-cause mortality within 30 days was compared. Results: In the crude population, the risks for MINS and 30-day mortality were higher for the hyperlactatemia group than the normal group (17.7% vs. 37.7%, odds ratio [OR]: 2.83, 95% confidence interval [CI]: 2.24–3.56, p < 0.001 and 0.8% vs. 4.8%, hazard ratio [HR]: 5.86, 95% CI: 2.9–12.84, p < 0.001, respectively). In 365 propensity score-matched pairs, intraoperative hyperlactatemia was consistently associated with MINS and 30-day mortality (21.6% vs. 31.8%, OR: 1.69, 95% CI: 1.21–1.36, p = 0.002 and 1.1% vs. 3.8%, HR: 3.55, 95% CI: 1.71–10.79, p < 0.03, respectively). Conclusion: Intraoperative lactate elevation was associated with a higher incidence of MINS and 30-day mortality.

The use of APACHE II, SOFA, SAPS 3, C-reactive protein/albumin ratio, and lactate to predict mortality of surgical critically ill patients: A retrospective cohort study

Several prognostic indices have been employed to predict the outcome of surgical critically ill patients. Among them, acute physiology and chronic health evaluation (APACHE) II, sequential organ failure assessment (SOFA) and simplified acute physiology score (SAPS 3) are widely used. It seems that biological markers such as C-reactive protein (CRP), albumin, and blood lactate levels correlate with the degree of inflammation during the immediate postoperative phase and could be used as independent predictors. The objective of this study is to compare the different predictive values of prognostic indices and biological markers in the outcome of 847 surgical patients admitted to the intensive care unit (ICU) in the postoperative phase.The patients were divided into survivors (n = 765, 57.4% males, age 61, interquartile range 51-71) and nonsurvivors (n = 82, 57.3% males, age 70, interquartile range 58-79). APACHE II, APACHE II death probability (DP), SOFA, SAPS 3, SAPS 3 DP, CRP, albumin, and lactate were recorded on ICU admission (first 24 hours). The area under the ROC curve (AUROC) and 95% confidence interval (95% CI) were used to measure the index accuracy to predict mortality.The AUROC and 95% CI for APACHE II, APACHE II DP, SOFA, SAPS 3, SAPS 3 DP, CRP/albumin ratio, CRP, albumin, and lactate were 0.850 (0.824-0.873), 0.855 (0.829-0.878), 0.791 (0.762-0.818), 0.840 (0.813-0.864), 0.840 (0.813-0.864), 0.731 (0.700-0.761), 0.708 (0.676-0.739), 0.697 (0.665-0.728), and 0.601 (0.567-0.634), respectively. The ICU and overall in-hospital mortality were 6.6 and 9.7%, respectively. The APACHE II, APACHE II DP, SAPS 3, SAPS 3 DP, and SOFA scores showed a better performance than CRP/albumin ratio, CRP, albumin, or lactate to predict in-hospital mortality of surgical critically ill patients.Even though all indices were able to discriminate septic from nonseptic patients, only APACHE II, APACHE II DP, SOFA and to a lesser extent SAPS 3, SAPS 3 DP, and blood lactate levels could predict in the first 24-hour ICU admission surgical patients who have survived sepsis.

The incidence and outcome of hyperlactatemia in patients admitted to the intensive care unit after elective surgery

BACKGROUND

Although hyperlactatemia is often developed in critically ill patients, it is unclear whether hyperlactatemia is associated with poor prognosis for surgical ICU (SICU) patients.

METHODS

We performed a retrospective analysis in an academic hospital in Tokyo. The maximum lactate was defined as the highest value within the SICU stay. The primary outcome was the composite outcome of in-hospital mortality, re-admission to the SICU or admission to the general ICU and emergency reoperation.

RESULTS

There were 3421 patients with normal lactate (<2 mmoL/L), 1642 with moderate hyperlactatemia (2-3.9 mmoL/L) and 299 with severe hyperlactatemia (≥4 mmoL/L). The composite outcome occurred in 6.2%. In multivariable logistic regression analysis, the odds ratio for the composite outcome was 1.49 for moderate hyperlactatemia and 1.42 for severe hyperlactatemia.

CONCLUSIONS

The odds ratio was similar between moderate and severe hyperlactatemia, so the cause and meaning of hyperlactatemia might be different among patients with elective surgery.

Serum lactate predicts resource utilization, but not surgical need, in the emergency department

BACKGROUND

Serum lactate is frequently tested in the emergency department (ED) setting to diagnose visceral ischemia and as a marker of end-organ perfusion. It is highly nonspecific, and levels can be affected by both kidney and liver function. In this retrospective chart review, we aim to demonstrate that serum lactate is overused in the ED setting and predicts resource utilization but not the need for surgical intervention.

METHODS

ED records with a chief complaint of "abdominal pain" were queried for the preceding 12 mo. We excluded pregnant patients, patients aged less than 18 years, and patients for whom a blood count and chemistry were not obtained. Vital signs, laboratory values, resource utilization, and outcome of the visit were obtained. Logistic regression models were developed to correct for confounding associations.

RESULTS

A total of 1003 records were obtained initially with 753 patients (75%) included in the study. Serum lactate was drawn in 118 patients (15%) and was elevated in 19 patients (16% of those drawn). Utilization of computed tomography imaging was associated with lactate utilization (P < 0.001). Patients in whom lactate was drawn were more likely to have a general surgery consult (51% versus 34%, P < 0.001) and to be admitted to the hospital (P < 0.001).

CONCLUSIONS

The use of serum lactate in the workup of patients with abdominal pain should be targeted at patients who have signs of sepsis and based on the index of suspicion for specific disease processes such as mesenteric ischemia.

Searching for predictors of surgical complications in critically ill surgery patients in the intensive care unit: a review

We reviewed the use of the levels of C-reactive protein, lactate and procalcitonin and/or the Sequential Organ Failure Assessment score to determine their diagnostic accuracy for predicting surgical complications in critically ill general post-surgery patients. Included were all studies published in PubMed from inception to July 2013 that met the following inclusion criteria: evaluation of the above parameters, describing their diagnostic accuracy and the risk stratification for surgical complications in surgical patients admitted to an intensive care unit. No difference in the Sequential Organ Failure Assessment scores was seen between patients with or without complications. The D-lactate levels were significantly higher in those who developed colonic ischemic complications after a ruptured abdominal aortic aneurysm. After gastro-intestinal surgery, contradictory data were reported, with both positive and negative use of C-reactive protein and procalcitonin in the diagnosis of septic complications. However, in trauma patients, the C-reactive protein levels may help to discriminate between those with and without infectious causes. We conclude that the Sequential Organ Failure Assessment score, lactate concentration and C-reactive protein level have no significant predictive value for early postoperative complications in critically ill post-surgery patients. However, procalcitonin seems to be a useful parameter for diagnosing complications in specific patient populations after surgery and/or after trauma.

Development and validation of a novel derivatization method for the determination of lactate in urine and saliva by liquid chromatography with UV and fluorescence detection

We developed a novel and straightforward derivatization method for the determination of lactate by reversed phase high-performance liquid chromatography (RP-HPLC) with fluorescence and UV detection in biological matrices as urine and saliva. The derivatization of lactate was achieved employing 9-chloromethyl anthracene (9-CMA) as fluorescence reagent, which has never been previously used to obtain a lactate derivative. Lactate reacts with 9-CMA with high selectivity in a very short time, without requiring extraction procedures from the aqueous solution, and the reaction reaches 70% completion in 30 min. The ester derivative obtained can be easily determined by RP-HPLC with fluorescence detection at 410 nm (λ ex=365 nm) and UV detection at 365 nm. The method was also optimized in order to allow for the simultaneous determination of lactate and creatinine for the application to urine samples. The lactate calibration curve was linear in the investigated range 2 × 10(-4)-3 × 10(-2)mM and the limit of detection, calculated as three times the standard deviation of the blank divided by the calibration curve slope, was 50 nM for both fluorescence and UV detection. Intra-day and inter-day repeatability were lower than 5% and 6%, respectively. The method proposed was successfully applied to the analysis of urine and saliva samples.