The possibility of predicting cardiac complications in thoracic oncosurgery using hematological indices

Introduction

Assessment of cardiac risk in thoracic oncosurgery is an important issue because perioperative cardiac complications (CC) and exacerbation of existing cardiac pathology can worsen the general condition of the patient and negatively affect the treatment results of the underlying oncologic disease [1-4]. There is increasing evidence in various fields of surgery about the possibility of predicting CC using long-known hematological indices, such as the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) [5-8]. Our previous results in vascular surgery [9] confirmed the usefulness of assessing these indices. Targeted studies devoted to the use of these indices for predicting CC in thoracic oncosurgery have not yet been conducted.

The aim of this study was to assess the informativeness of NLR and PLR in predicting cardiac complications in thoracic oncological surgeries.

Materials and methods

After obtaining permission from the local ethics committee, a simple single-center prospective observational study was conducted.

The study included patients who were undergoing planned inpatient treatment in the thoracic surgery department of the Kostroma Regional Clinical Hospital named after E.I. Korolev from March 2022 to March 2023.

The inclusion criteria for the study were as follows: age over 45 years, planned thoracic oncological surgery under general anesthesia, and patient consent to participate in the scientific study.

We excluded patients who underwent emergency surgeries in the presence of blood diseases, patients with grade 3 obesity, and those with surgical complications.

Taking into account the above criteria, 78 patients were initially selected, 7 of whom were then excluded.

We analyzed the data of 71 patients (41 men and 30 women) aged 45 to 78 years (Me = 64 [60-71]). According to the classification of the American Association of Anesthesiologists (ASA), the patients belonged to Me = 3 [3-4] risk level. The patients underwent the following surgical interventions (Table 1).

All patients underwent multicomponent general anesthesia with artificial ventilation of the lungs, and standard monitoring was performed. The duration of the operations varied from 145 to 365 min (Me = 260 [210-315]).

The calculation of the hematological indices of NLR and PLR was carried out from the data of the general blood test performed one day before the operation on the automatic hematological analyzer Mindray BC-3600 (China).

An analysis was carried out for the presence of concomitant cardiac diseases in patients, such as coronary heart disease (CHD), hypertension (HTN), chronic heart failure (CHF), and diabetes mellitus (DM), as well as cases of acute cerebrovascular accident (ACVA).

During the perioperative period, the development of the following cardiac complications was monitored: cardiac mortality, myocardial infarction (MI), transient myocardial ischemia, acute heart failure or decompensation of CHF, stroke, and pulmonary embolism (PE). Cases of a composite outcome, which included any of the listed CCs, were also recorded.

All patients were assessed preoperatively with the revised cardiac risk index (RCRI), individual CRI (Khoronenko CRI), and the American College of Surgeons CRI for assessing the risk of myocardial infarction or cardiac arrest (MICA CRI).

A database was created in the Microsoft Office Excel program to store and process the information. Advanced statistical analysis was performed in MedCalc 15. The nature of the data distribution was assessed using the Kolmogorov-Smirnov criterion. The data are presented as the minimum (min) and maximum (max) values, median (Me), and interquartile range (P₂₅-P₇₅). The average frequency of the occurrence of features (P) was also calculated.

To assess the relationships between the variables, a correlation analysis was performed with the calculation of the Spearman correlation coefficient (rho) and determination of the significance level (p).

The logistic regression method was used to analyze the influence of the independent variables on the dependent variables, which were coded in binary format. During the analysis, the odds ratio (OR), 95% confidence interval (CI), and the level of significance of influence (p) were calculated. The results of the analysis were considered statistically significant at a significance level of p <0.05.

Results

The values of NLR varied from 1.3 to 7.4 conventional units (Me=2.8 [2.1 – 4.5]). The values of NLR were in the range from 53 to 485 conventional units (Me=135 [115 – 205]). The median values of CRI corresponded to the “norm”; however, the maximum values in individual observations indicated a high risk of developing CC (Table 2). There were no correlations between NLR and PLR and the values of CRI (rho=0.075–0.113; p=0.27–0.53).

Concomitant cardiac diseases were identified in 65 (91.6%) patients: coronary heart disease in 11 cases, hypertension in 63, chronic heart failure in 11, type II diabetes mellitus in 12, and a history of stroke in 2. According to the results of the logistic regression, the hematological indices of NLR and PLR were not associated with concomitant cardiac diseases (p=0.24-0.69).

Cardiac complications in the form of a composite outcome were identified in 9 (12.7%) patients: cardiac mortality in 1 observation, MI in 2, transient myocardial ischemia in 2, CHF decompensation in 4, and PE in 1. 

Both hematological indices were not predictors of cardiovascular complications, either in the assessment of the composite outcome (Table 3) or in relation to one case of cardiac mortality (p>0.05). At the same time, Khoronenko ICR and MICA predicted CC, and RCRI had a certain tendency to predict. MICA CRI was an independent predictor of cardiac mortality (p=0.032). All this indicates a sufficient representativeness of the sample, within which the non-informativeness of hematological indices was revealed.

Conclusion 

Assessment of the risk of developing cardiac complications in oncology has attracted the active attention of clinicians [1-3]. Patients who are planned to undergo oncological surgeries often have several concomitant cardiovascular diseases, which increases the likelihood of developing perioperative CC [10]. In our study, the frequency of CC was 12.7%, which is comparable with the results of other researchers [2, 11]. There are a large number of different tools for stratifying cardiac risk, which are described in detail in international and domestic documents [12, 13]; however, they do not include the assessment of simple and accessible hematological indices. A number of modern studies [5-7] have shown that NLR and PLR, the calculation of which is possible in any medical organization, can have a certain prognostic value. The identification of patients with high cardiac risk is a step toward prescribing them targeted adjuvant cardioprotection [14, 15].

Changes in the quantitative ratios of neutrophils, lymphocytes and platelets may reflect disturbances in the processes of immunity, inflammation and thrombus formation, as well as damage to the endothelium, development of endothelial dysfunction and atherosclerosis [16, 17]. Our previous works have shown positive results in vascular and ambiguous results in abdominal oncosurgery [9, 18]. We described the biochemical and pathophysiological mechanisms of the informativeness of hematological indices in oncology in more detail in this article [18].

It is also important to note the significant variability of the reference values of hematological indices (NLR 0.78 to 4) [19-22], (PLR from 42 to 239) [19, 20, 22] conventional units. The values of these indices may increase in the presence of oncological diseases themselves.

All of the above factors probably explain our negative results in thoracic cancer patients. However, further studies are needed to increase the sample size of patients and evaluate these parameters in other areas of surgery.

Conclusion

We cannot recommend the use of the hematological indices NLR and PLR for predicting cardiac complications in thoracic oncological surgeries.