This retrospective cohort study found a curvilinear relationship between the platelet count and the 28-day mortality rate in medical-surgical ICU patients with sepsis. The nonlinear analysis showed that when the platelet count was less than 127 x10ˆ9/L, every 10-unit increase in platelet count was associated with a significantly decreased risk of the 28-day mortality rate. When the platelet count was more significant than 127 x10ˆ9/L, an increase in the platelet count per 10 change was not associated with the mortality rate. To our knowledge, this is the first study to report the association between platelet count and 28-day mortality in medical-surgical ICU septic patients.
Most studies investigating the relationship found that platelet count was associated with mortality risk. A prospective cohort study of adult ICU patients in 52 ICUs across ten countries found that patients with thrombocytopenia had worse outcomes, including 90-day mortality and bleeding[24]. Furthermore, some studies have found that the platelet count is associated with 28-day mortality in different ICU patients. A retrospective study utilizing the eICU database suggested that patients in the neurological ICU who developed thrombocytopenia had a higher risk for in-hospital mortality[13]. Using the eICU database, another study found that the association between platelet count and in-hospital mortality was curvilinear in critically ill patients with tumors [12]. Another study using the eICU database revealed a curvilinear relationship between platelet counts and mortality risk for patients with infectious diseases in the intensive care unit, with an increased risk of mortality when the platelet count fell below 130 × 109/L[14]. The above studies have investigated the relationship between platelet count and mortality rate, representing a limited perspective on the complex physiological processes in the human body. This relationship cannot be generalized to all patient populations.
Our study revealed that the platelet count was associated with the 28-day mortality rate in medical-surgical ICU patients. And this association was L-shaped. When the platelet count was < 127× 109/L, an increase of 10 units in the platelet count was associated with a 10% decreased risk of a 28-day mortality rate. Nevertheless, this relationship was insignificant when the platelet count was ≥ 127 x10ˆ9/L. This shows that the safe range for the platelet count in medical-surgical ICU patients with sepsis is 127 x10ˆ9/L.
Medical-surgical ICU patients can experience various platelet-related issues, with multiple factors often at play concurrently. The main mechanisms involve (1) hemodilution[25], (2)immune thrombocytopaenia[26, 27], (3)blood coagulation mechanism abnormalities[28], (4)the use of heparin and low-molecular-weight heparin (LMWH)[29], (5)pseudothrombocytopenia[30]. This study analyzed data from medical-surgical patients with sepsis in the ICU and identified the relationship between platelet count and the 28-day mortality rate was nonlinear. This information may help guide early clinical interventions in patients who are at risk, thereby prolonging their survival. When the platelet count of medical-surgical ICU patients falls below 127 x 10^9/L, clinicians may pay close attention to their condition and consider whether intervention measures are necessary.
This study has several strengths. First, the large sample size from eICU-CRD strengthened the statistical power and credibility. We utilized multiple logistic regression models to assess the correlation between platelet count and 28-day mortality. Second, we used strict statistical adjustment to reduce residual confounding to avoid the influence of unavoidable potential confounding in this observational study. Third, we used a GAM to investigate a curvilinear relationship between the platelet count and 28-day hospital mortality in medical-surgical ICU patients with sepsis. Fourth, we conducted a two-piece-wise linear regression model to examine the threshold effect of the platelet count and 28-day mortality. Finally, to minimize the bias introduced by missing data, we grouped the missing data into a set of dummy variables and included them in all analyses.
This study has several limitations. First, this was a retrospective study subject to the inherent limitations of a retrospective design. Second, despite employing multivariate logistic regression to adjust for potential confounding variables, some potential confounding factors were not included in the analysis, leading to biased results. Third, due to differences in population characteristics, blood testing methods, ethnic blood traits, and even the timing of data collection, these values vary across different laboratories. Since the data were collected from 2014 to 2015, observation of changes over a longer timeframe is impossible. Fourth, the eICU database only evaluates and treats critical illnesses and does not include information on treating platelets.