Plasma lactate level is a rapid and easily accessible test that can be measured in an arterial blood gas (ABG) sample and is a marker of the severity of tissue oxygen demand. Although there are many studies showing that high lactate levels increase the risk of heart failure, trauma, sepsis, pulmonary embolism and cardiovascular mortality, there are a limited number of studies examining the relationship between COPD exacerbation and lactate ⁶. Similarly, few studies have examined the prognostic value of Rapid Sequential Organ Failure Assessment (qSOFA) scoring, a scoring system used to diagnose sepsis through a rapid assessment at the time of initial presentation, in patients with COPD exacerbations. Predicting with high probability the future clinical outcome of a disease with high morbidity, such as COPD, would be very useful in making certain precautions and treatment decisions about COPD patients. In this context, there is a need for new parameters that can help determine the prognosis of COPD patients. Our aim in this study was to contribute to the literature by examining the prognostic value of lactate level and qSOFA score in patients admitted to the emergency department with COPD exacerbation.

This study was conducted as a retrospective study on chronic obstructive pulmonary disease patients who applied to the Emergency Medicine clinic with acute exacerbation. Patients were previously diagnosed with COPD according to international diagnostic guidelines. Local Ethics Committee approval (Decision No: 2024/10-192) was obtained and the study was conducted in accordance with the ethical standards set out in the 1964 Declaration of Helsinki and its subsequent amendments. Informed consent was waived because the study was retrospective. All patients enrolled in the study were those presenting to the emergency department between July 2024 and September 2024. A total of 147 cases were selected for the study. Patients over 18 years of age, with a previous diagnosis of COPD and one or more of the following exacerbation symptoms were included in the study;

increased shortness of breath,

cough and wheezing,

increased sputum purulence and quantity.

Patients with other chronic respiratory diseases such as bronchiectasis, active tuberculosis, asthma, pulmonary embolism, immune system diseases, bacterial infections outside the respiratory system, lung cancer and other malignant tumors were excluded.

Data Collection

Patient data were accessed using the hospital information management system. A data collection form was completed for each patient, in which age, gender, arterial blood pressure, pulse rate, respiratory rate, fingertip saturation value, fever, comorbidities and blood parameters taken at the time of initial presentation were recorded. In addition, the duration of hospitalization, mortality rates and the need for intensive care were analyzed. The qSOFA scores of all patients were calculated. Afterwards, comparisons were made between hospitalized and discharged patients in terms of the parameters in the patient follow-up form. Furthermore, the association of lactate and qSOFA scores with length of hospital stay, 28-day mortality, and hospitalization to the ward or intensive care unit was examined.

qSOFA

qSOFA scores were calculated for all patients hospitalized or discharged from the emergency department. qSOFA consists of 3 points: impaired consciousness, systolic blood pressure of 100mmHg or less and respiratory rate more than 22 breaths/min ⁶

Statistical Analysis

The data were first transferred to the Excel program and after some adjustments such as converting textual data into numerical data and labeling the data, they were transferred to the SPSS version 29.00 (SPSS, Inc, Chicago, IL) package program. The data were analyzed in two ways: descriptive and interpretive. Before the analysis, the data were subjected to different normality tests and the findings were reported according to the values ​​obtained. Accordingly, normally distributed data were reported as mean and standard deviation, and non-distributed data were reported as median and quartiles. Categorical variables are presented with frequency and percentage. Two-group variables were analyzed with independent sample t-test or Mann Whitney U test according to their meeting the assumptions. For variables with three groups or more, Oneway ANOVA or Kruskal-Wallis (MKW) test was used according to the fulfillment of the assumptions. In-group comparisons of categorical variables were made using the chi-square test or Fisher Exact test according to the fulfillment of the assumptions. In addition, the relationship between two continuous variables was determined by Pearson correlation analysis. All statistical analyses were two-tailed and the significance level was set at 0.05.

Parameters such as age, gender, vital signs, comorbidities, laboratory findings, need for non-invasive mechanical ventilation and qsofa were compared in hospitalized and discharged patient groups. As a result of the analysis, significant differences were found between the two groups in terms of blood pressure arterial, pulse rate, respiratory rate, finger tip saturation, renal failure, CRP, lactate and qSOFA. In terms of lactate, the inpatient group had higher lactate values than the discharged patients. This difference was statistically significant. In addition, of the 42 patients with zero qSOFA, 34 were discharged and 8 were hospitalized. This difference between the groups was statistically significant (Table 1).

Table 1: Patient characteristics. 1, chi-square for categorical variables, independent sample t-test for variables reporting mean and standard deviation, Mann-Whitney U test for variables reporting median and IQR; **, significant at 0.01 level; * significant at 0.05 level; Cramer’s V for a, Cohen’s D for b and r for c were used to determine the effect size. DM, diabetes mellitus; HT, hypertension; CKD, chronic kidney disease; CAD, coronary artery disease; BUN, blood urea nitrogen; WBC, white blood cell; CRP, C-reactive protein; HCT, hematokrit; HGB, hemoglobin; ST, systolic tension; DT, diastolic tension; IQR, interquartile range; ss, standard deviation; RR, respiratory rate; NIMV, non invasive mechanical ventilation; SpO2, saturation; pH, potential hydrogen.

Association of lactate with length of hospitalization, place of hospitalization and mortality

The relationship between Lactate and place of hospitalization, mortality and length of stay in the hospitalized patient group was analyzed by Mann-Whitney U-test, independent sample t-test and Pearson Correlation test. As a result of the analyses, no significant association of Lactate with any variable was found (p>0.05 for each variable) (Table 2).

Table 2: Association of lactate with length of hospitalization, place of hospitalization and mortality. 1, Pearson Correlation; 2, Mann-Whitney U-test; 3, Independent Sample t-test; IQR, interquartile range; ss, standard deviation.

Association of qSOFA with place of hospitalization, length of stay and mortality

One-way ANOVA test was used to compare the means of different qSOFA groups for the variable “length of hospitalization”. As a result of ANOVA, there was a statistically significant difference between the groups (F(3, 77) =2.96, p =0.03, η2 =0.12). Tukey HSD post-hoc test was applied to determine the specific differences between the groups. However, according to the results of the post-hoc analysis, there was no significant difference between the groups (p >0.05 for all group comparisons). Although this showed that there was a difference between the groups in general for ANOVA, it could not determine which qSOFA groups were different. Although this is not often encountered in analyses, it may be because the overall difference was small or because the post-hoc tests were too sensitive to detect differences between groups. Chi-square test was applied to examine the relationship between qSOFA score and place of hospitalization (ward or intensive care unit). According to the results of the analysis, a statistically significant association was found between qSOFA score and place of hospitalization (χ²(3, N =78) =8.99, p =0.03). However, according to the test assumptions, the expected frequencies of the cells should be at least 5. As a result of the test, it was determined that the expected frequency was below 5 in 37.5% of the cells. Based on this result, the Fisher Exact Test result was reported. The test results showed a significant relationship similar to the Pearson's chi-square test (FisherExact =7.68; p =0.03). Adjusted Residual values were also analyzed to determine between which cell blocks the difference was between. According to the results, patients with a qSOFA score of 3 were significantly more likely to be hospitalized in intensive care (a.r. =2.9) and significantly less likely to be hospitalized in the ward (a.r. =-2.9). The same was true for patients with a qSOFA score of 1. Accordingly, patients with socket 1 were significantly more likely to be hospitalized in the ward (residual =2.0) and significantly less likely to be hospitalized in intensive care (residual = -2.0). In qSOFA 2 and 0 groups, there was no significant difference between cells.

The relationship between qSOFA and 28-day mortality was again analyzed by Pearson Chi-square test. As a result of the analysis, the Fisher-Freeman-Halton Exact Test result was reported since the expected frequency was below 5 in 37.5% of the cells. Accordingly, a significance value of p = 0.130 was obtained. This result suggests that there is no statistically significant association between qSOFA score and mortality. However, the results of the Linear-by-Linear Association test revealed a significant linear association with p = 0.039. This finding indicated that there was a significant linear association between qSOFA score and mortality and that the risk of mortality may increase with increasing qSOFA score. The association of qSOFA with place of hospitalization, length of stay and mortality is shown in table 3.

Table 3: Association of qSOFA with place of hospitalization, length of stay and mortality. a, Eta-Squared (η2); b, Cramer’s V; *, significant at 0.05 level; ss, standard deviation.

The limitations of our study are that it is retrospective, lactate levels were measured only once, and other pathologies that may cause hyperlactatemia were not evaluated. Prospective studies involving larger patient populations are needed to understand whether qSOFA and plasma lactate levels have prognostic significance in patients with COPD exacerbations. Serial plasma lactate level evaluation would be useful in prospective studies on this subject.