Prognostic Value of Red Blood Cell Width Distribution-to-Platelet Ratio in Patients with Snakebite-Associated Multiple Organ Dysfunction Syndrome: A Retrospective Observational Study

Introduction

Snakebite is a profoundly deleterious affliction that poses a significant threat to human life, primarily through venom injection and the subsequent development of organ damage syndromes caused by toxins. Recent statistics reported by the World Health Organization (WHO) indicate that snakebites have resulted in a range of 81000 to 138000 fatalities, and at least 400000 patients suffering from permanent disability. The snakebite predominantly threatens roughly 5.8 billion people, affecting those residing in impoverished and rural communities.^1,2 According to WHO guidelines for grading snakebite severity,³ patients are classified into three categories: mild, moderate, and severe. This grading system is based on local symptoms (such as the extent of swelling and necrosis), systemic symptoms (such as neurotoxicity and coagulopathy), and laboratory findings (such as platelet count and coagulation function).

The mountainous population is particularly prone to snake encounters, due to their predominant engagement in agricultural activities, livestock rearing, poultry farming, and fish cultivation.⁴ The prevalent snake species in this region comprise aquatic snakes (Enhydris chinensis) and pit vipers (Gloydius brevicaudus). Pit viper bites are common in clinical practice, Pit viper venom is a mixture of neurotoxin and hemotoxin. Compared with other vipers, envenomation caused by these vipers has generally resulted in relatively low fatality rates. However, the symptoms are tremendously biased toward systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS), attributed to the widespread utilization of the target antivenom treatments.

Systemic Inflammatory Response Syndrome (SIRS) is a widespread inflammatory state triggered by infection or non-infectious insults, characterized by dysregulation of the body’s immune response.⁵ It is diagnosed by the presence of at least two of the following criteria: abnormal body temperature (>38°C or <36°C), tachycardia (>90 beats/min), tachypnea (>20 breaths/min or PaCO₂ <32 mmHg), and abnormal white blood cell count (>12,000/μL, <4,000/μL, or >10% immature forms). SIRS is often an early stage of severe conditions such as sepsis, and it plays a critical role in the progression of multiple organ dysfunction syndrome (MODS) and increased mortality in critically ill patients. Early recognition and management of SIRS are essential to prevent further complications.

Multiple organ dysfunction syndrome (MODS), is the simultaneous failure of two or more organs during infection and other systematic inflammation. This condition has been considered a primary contributor to both mortality and mobility among critically ill patients.⁶ Several studies have reported the significance of organ damage such as acute kidney injury (AKI), and coagulation disorders played an important role in snakebite envenoming development.^7,8 Red blood cell distribution width (RDW) and platelet count as part of the standard complete blood count (CBC) were widely used in disease diagnosis. With the inflammation and oxidative stress induced by disease, there is a persistent process of destruction and regeneration of red blood cells and platelets. However, the magnitude of these changes was extremely inconsistent. Red blood cell distribution to platelet ratio (RPR) is calculated by the ratio of the red blood cell distribution/platelet count, which has become an important marker used for the prognostic of mortality and mobility in severe burns, hepatitis, cancer, breast cancer, colorectal cancer and glioblastoma.^9–13 We have previously demonstrated that RPR plays an important role in the prognostic of mortality in severe burns.¹⁰

In this study, we investigated the potential indicators to predict multiple organ dysfunction failure in snakebite patients, and to determine the prognostic value of associating factors, particularly the RPR after snakebite.

Materials and Methods

A total of 1239 patients with snake attacks and clinical wounds were treated at the First Affiliated Hospital of Anhui Medical University and the First Affiliated Hospital of Anhui University of Chinese Medicine between 2015 and 2020 and were enrolled in the retrospective study. Snakebite patients should visit one of the two hospitals within 48 hours after injury; The exclusion criteria were as follows: 1) patients who visited the hospital for more than 48 hours after injury or discharged against medical advice. 2) patients with known cancer, immune diseases, and organ functional lesions such as cardiac disease, kidney disease, hepatopathy, hematological, biochemical, or serological abnormality were also excluded. 3) patients infected before being sent to the hospital or had surgery within 1 month. 4) patients had incomplete or missing information records. Finally, 637 snakebite patients were included in the study. All patients were notified in writing that their demographic data and clinical results of hospitalization might be used for scientific research.

The treatment of snakebite patients in this study was based on the World Health Organization (WHO) guidelines for the management of snakebites and the Chinese guideline for management of snakebites.^3,14 Key principles included the timely administration of antivenom for systemic envenoming, supportive care, and wound management to prevent infection. Regular laboratory monitoring of coagulation profiles, platelet counts, and renal function was conducted to guide treatment and ensure optimal patient outcomes.

All patients in this study were victims of viper bites and received intravenous antivenom serum (Shanghai Serum Bio-technology Co., Ltd.) upon hospital admission. A 6000U dose was administered in 200 mL of saline solution. This antivenom has been confirmed to be free of hemorrhagic, neurotoxic, and cytotoxic effects, demonstrating excellent biosafety and serving as a reliable treatment for venom neutralization.

Steroids, such as dexamethasone (10mg in 250mL of saline solution), were administered for three days to reduce edema and mitigate inflammatory responses. Prophylactic measures were also taken to protect vital organs, such as intravenous administration of 1.8g of glutathione, along with the infusion of 1000–2000mL of fluids. The bite site was treated with wound debridement and dressing changes. For areas of significant swelling, needle puncture and cupping therapy were performed daily to promote the reduction of swelling. Additionally, a topical mixture of ground Jidesheng snake medicine tablets, honey, and white vinegar was applied around the bite site and the swollen areas once per day until the swelling subsided (Figure 1).

Figure 1 Patient care flow chart.

Figure 2 The 1st-day RPR values for snakebite patients with MODS and NO-MODS. Data represented as mean, standard deviation (SD), and individual patient value markers.

Data Collection

The clinical data collected from the electronic medical record included demographics (gender, age), medical history, specialized medical, results of laboratory tests (The blood routine, biochemical test, coagulation function), and complication record. Blood draws were performed on the first 24 hours of enrollment and the fifth 24 hours after enrollment for dynamically measuring the internal environment of the snakebite patients. All patients had a 60-day follow-up to determine the endpoint and ensure complete wound healing. The diagnosis of MODS was based on organ failure criteria and the Sequential Organ Failure Assessment (SOFA) score, for evaluating and monitoring organ dysfunction in critically ill patients, particularly in intensive care units. The SOFA score assesses six organ systems: respiratory, coagulation, liver, cardiovascular, renal, and neurological (Table 1). Higher scores indicate more severe dysfunction and are generally linked to poorer outcomes.

Table 1 Sequential Organ Failure Assessment (SOFA)

Organ Failure Diagnostic Criteria

The diagnostic criteria of organ failure were as described:^15–17

1. Circulation dysfunction was defined as shock status with systolic blood pressure <90 mmHg or mean arterial pressure <70 mmHg.
2. Respiratory dysfunction was defined as PaO2/FiO2 ratio <300 or required mechanical ventilation more than 24 hours.
3. Renal dysfunction was defined as serum creatinine level >1.2 mg/dL or a urine output <0.5 mL/kg/h for more than 6–12 h.
4. Hepatic dysfunction was defined as serum bilirubin level >20.5 umol/L or alanine aminotransferase and aspartate aminotransferase more than two times the upper limit of normal.
5. Hematologic dysfunction was defined as a blood platelet count <100,000/μL.
6. Coagulopathy was defined as an international normalized ratio >1.5.
7. Nervous system dysfunction was defined as Glasgow Coma Scale < 14.

Patients with MODS after snakebite must satisfy the two following conditions: two or more organ function disorders occurred simultaneously or sequentially during hospitalization and the SOFA scores were higher than 2.

Statistical Analysis

SPSS 22.0 (SPSS, Chicago, IL, USA) was used for statistical analysis. Continuous variables were described as mean ± standard deviation (SD), and other data were represented by frequency (%). All patients were divided into the MODS group and NO-MODS group and took the 1^st day and 5^th day as time points respectively. Student’s t-test and Pearson’s χ²-test were employed to evaluate the differences between the MODS and NO-MODS groups. Before conducting the t-test, normality tests and assessed homogeneity of variance were performed to confirm that the data were normally distributed and that the assumption of sample independence was satisfied. The receiving operating characteristic (ROC) curves were constructed for RPR at two different time points the area under the ROC curves (AUC) was used for assessing the prognostic performance, and the Youden index (Youden index = sensitivity + specificity – 1) was used for calculating the best cutoff points. The T-tests, chi-square tests, and univariate logistic regression were performed to analyze the potential variables, and then the candidate variables were subjected to multivariate logistic regression to determine the independent prognostic factors for MODS after snakebite.

Results

602 patients were excluded due to hospitalization exceeding 48 hours (n=146). Incomplete cure patients discharged from the hospital (n=104). Patients with known cancer (n=6), immune diseases (n=22), and organ functional lesions such as cardiac disease, kidney disease, and hepatopathy. Hematological, biochemical, or serological abnormalities were also excluded (n=62), incomplete or missing information records (n=262).

A total of 637 patients were included in the study. According to the (Table 2), the mean age was 52.81±17.78 (range: 1–88). The gender balance remains roughly equal in the snakebite patients (male to female; 57.5% to 42.5%). As far as the patients are concerned, the majority of snakebite wounds were located in the lower limb (61.4%), 245 patients (38.5%) in the upper limb, and only one patient in the shoulder for the snake coiled around the branch before attacking. The snake attack happened commonly in summer (74.9%), the incidence rate in the autumn (21.2%) was not far behind, it was very low in the spring (3.8%) and winter (0.2%).

During the hospitalization, 56 (8.8%) patients developing MODS were recorded, 61 (9.6%) patients developed shock and received fluid resuscitation, 5 (0.8%) patients received mechanical ventilation for respiratory dysfunction, 13 (2.0%) patients developed renal dysfunction, 118 (18.5%) patients occurred liver dysfunction, 97 (15.2%) patients developed hematologic dysfunction, 20 (3.1%) patients developed coagulation dysfunction, and 3 (0.5%) patients developed nervous system dysfunction (Table 2).

Table 2 Baseline Clinical Characters for the Snakebite Patients

Table 3 shows the comparison of baseline clinical characteristics. The endpoint of this study was the occurrence of MODS, all snakebite patients were divided into the MODS group (56 cases) and the NO-MODS group (581 cases). Gender and the site of the bite were considered without difference between the two groups. In the MODS group, age and bite-to-hospital time were higher than in the NO-MODS group.

Table 3 Comparisons of Baseline Clinical Characters Between MODS and NO-MODS Patients

Table 4 compared the clinical subjects between the MODS group and the NO-MODS group at two different time points. Compared to the NO-MODS patients, the MODS patients had significantly higher WBC, Neutrophils, PLT, RPR, ALT, AST, TBIL, DBIL, and CR in the 1^st-day laboratory result. However, on the 5^th-day post-snakebite, significant hematological and biochemical differences were observed between patients with MODS and those NO-MODS. The MODS group exhibited lower lymphocyte, RBC, hemoglobin, and PLT, suggesting immune dysregulation and inflammation associated with organ dysfunction. cBiochemical markers in the MODS group revealed elevated ALT, AST, TBIL, DBIL, and IBIL, reflecting impaired liver function or rhabdomyolysis. The myotoxicity of snake venom can induce rhabdomyolysis, leading to muscle breakdown and the release of intracellular components, including CK, LDH, myoglobin, and AST.¹⁸ This process may contribute to the development of acute renal dysfunction. Additionally, significantly higher BUN and CR levels in MODS patients indicated renal dysfunction.

Table 4 Comparison of Laboratory Subjects Between MODS and NO-MODS Patients at Two Different Time Points

Figure 2 shows the 1^st-day RPR values for snakebite patients with MODS and NO-MODS. The significantly elevated RPR on MODS group suggests increased inflammation and coagulopathy. Figure 3 presents the ROC curves of the RPR on the 1^st day and 5^th day and the occurrence of the MODS in the snakebite patients. The sensitivity and specificity of the 1st-day RPR (AUC=0.720 95% CI,0.642–0.798). The Youden Index was used to calculate the optimal cut-off value of the RPR (the 1st day RPR=0.110, the 5th day RPR=0.085).

Figure 3 Received operating characteristic curve of the 1st-day RPR (AUC=0.720 95% CI,0.642–0.798) and the 5th-day RPR (AUC=0.689 95% CI,0.612–0.767) for prediction of MODS in snakebite injury.

The results of the Student’s t-test and Pearson’s χ2 test were included in the univariate logistic regression analysis to identify the potential factors influencing outcomes. The statistically significant variables were performed using the multivariate logistic regression analysis for estimating the independent prognostic value between the MODS status and the potential predictors (Table 5).

Table 5 Univariate and Multivariate Logistic Regression Analysis for MODS and NO-MODS Patients at Two Different Time Points

Discussion

The occurrence of MODS emerges as a serious complication in infectious or non-infectious stimuli due to its rapid progression and deterioration.¹⁹ In this progress, the detection of the organ dysfunction and the early identification of the MODS are crucial factors for assessing the prognosis of snakebite.

Herein, we conducted an investigation into potential hematological indicators at early time points to predict the occurrence of MODS in snakebite patients to raise awareness of the systematic inflammation and potential adverse outcomes. This is the first study to explore the clinical implications of MODS in snakebite patients, with a specific focus on evaluating the prognostic value of the RPR. In our study, 56 (8.79%) patients developed MODS after snakebite. The most common organ failure was hepatic dysfunction (n=118,18.5%) followed by hematologic dysfunction (n= 97.15.2%). In the multiple logistics analysis, bite to hospital, the 1^st day RPR, CR and the 5^th day AST were identified as independent prognostic factors associated with the occurrence of MODS after snakebite.

Organ dysfunction frequently occurs in snakebite cases. Rapid venom release into the bloodstream and its interaction with major organs play a critical role in snakebite pathology, leading to infection, inflammation, neurotoxicity, and multi-organ damage.²⁰ Previous studies have extensively reported the poor outcomes after snakebite, including circulation dysfunction with hemodynamic instability, respiratory dysfunction, renal dysfunction, hepatic dysfunction, thrombocytopenia, and nervous system dysfunction.^7,21–27 Exploring the mechanism and manifestation of MODS following snakebite is essential. However, clinical identification is challenging since humans are not the primary targets of snake venom, and its metabolism in the human body remains complex.

Snakebite can be divided into three kinds according to the poisoning situation: the absence of venom being injected (dry bites), isolated local symptoms, and snakebite with systemic envenoming.¹⁸ It is difficult to diagnose snakebite and take appropriate treatment for human symptoms at the early stage, such as hyperventilation, syncope, vomiting, and other clinical features.²⁰ Therefore, we can regard the occurrence of MODS as an exacerbation condition, and early intervention offers a large opportunity for controlling MODS in snakebites.

RPR has been recognized as a valuable prognostic indicator of inflammation diseases.²⁸ The aggressive inflammation-promoting destruction of red blood cells decreased the production of red blood cells and elevated the red blood cell distribution (RDW) value.²⁹ Moreover, dysfunction in the hemostatic system, particularly thrombocytopenia was associated with acute systemic inflammation for rapid trapping and consumption of platelets.³⁰ Several studies propose that thrombocytopenia is associated with heightened disease severity and worsened outcomes.^31,32 Therefore, the combination and conversion of the RDW and platelet are biologically feasible for predicting the development of MODS. Chen, B. et al ⁹ first proposed RPR as a novel, simple noninvasive index for predicting hepatic fibrosis and cirrhosis. Further, Cetinkaya, E. et al³³ analyzed 102 acute pancreatitis patients’ data and the result showed that RPR was associated with mortality and the severity of the inflammation. Equally significant, our previous study has demonstrated that RPR was independently associated with mortality in patients with burns.¹⁰

Snakebite is a prevalent clinical issue that significantly impacts patients’ quality of life and gives rise to economic or social consequences. This paper retrospective analyzed 637 patients with snakebites coming from two major teaching hospitals. However, this study has several limitations. Firstly, the qualitative data is mainly from the two major hospitals in the Anhui Province in China, and may not fully represent the current status in other regions. Secondly, the retrospective study introduces inevitable bias. Thirdly, there were differences in the species, living habits, and characteristics of the snake among regions and countries. Lastly, differences in medical treatment levels and resources have resulted in the omission of data on medical equipment and pharmaceuticals in the study.

Conclusion

MODS represents a serious morbidity syndrome with snakebite. This study demonstrates that the red blood cell distribution to platelet ratio exhibits an independent prognostic value for the occurrence of MODS in snakebite patients. Specifically, the 1^st day-higher RPR (≥0.110) could serve as a predictive tool for identifying organ dysfunction.