Study On The Influencing Factors And Prognostic Value Of Platelet Count In Critically Ill Patients

Objective:This study aims to clarify the characteristics of dynamic changes in platelet count of ICU patients,and find out the related factors resulting in changes.Moreover,we aim to explore the relationship between the dynamic change of platelet count and the shortterm and long-term mortality of ICU patients.Method:In this study we collected 7839 cases of ICU patients from 2001 to 2012,the United States Boston’s Beth Israel Deaconess medical center where MIMIC Ⅲdatabase was included.All kinds of information were collected such as the general situation,basic vital signs on admission to hospital,all kinds of laboratory indexes,medications,ICU related scores and events.Patients were grouped according to platelet count at admission and 28-day and 4-year prognosis(survival/death).The risk factors for 4-year death after admission to ICU were analyzed by Mann-Whitney U rank sum nonparametric test and χ2 test.Univariate and multivariate Cox proportional risk regression analysis was used to screen out independent risk factors affecting the prognosis at 28 days and 4 years.The ROC curves and Kaplan-Meier curves were drawn and the survival analysis was conducted to show the survival probability.Result:A total of 7839 patients are included in this study,with a median age of 67.8 years(54.1-78.6),including 4405 males(56.2%)and 3434 females(43.8%).The median length of ICU stay is 4.9 days(3.0-9.9).Results show that severe thrombocytopenia group(PC<50×109/L)contains 153 cases(1.95%),thrombocytopenia group(50×109/L<PC<150×109/L)contains 2140 cases(27.30%),normal platelet count group(150×109/L≤PC≤450×109/L)contains 5246 cases(66.92%)and Thrombocytopenia group(PC>450×109/L)contains 300 cases(3.83%).There are 6901 patients in the 28-day survival group and 938 patients in the 28-day death group,with a 28-day mortality rate of 12.0%.There are 4550 patients in the 4-year survival group and 3289 patients in the 4-year death group,with a 4-year mortality rate of 42.0%.The results show that APACHE Ⅱ score and RDW are related to the severe thrombocytopenia(P<0.05).Age,RDW,SAPS Ⅱ score,infection,cardiac arrest are independent risk factors of 28 days and 4 years prognosis of ICU patients,and weight,the platelet count on day7 and ΔPC7%=[(PC on day7-PC on day 1)/PC on day 1×100%]are the protective factors(P<0.05).The joint index of Δ PC7%+SAPS Ⅱ score has high accuracy in predicting the prognosis of patients at 28 days and 4 years(AUC respectively 0.747,0.730,P<0.0001).For ICU patients with sepsis,PC4,RDW,SAPSⅡ scores and infection are independent risk factors for the 4-year prognosis,and PC5 and the maximum platelet count(PCmax)within 7 days are independent protective factors for the 4-year prognosis(P<0.05).Δ PC7%can better predict the long-term prognosis of ICU patients with sepsis,and its predictive value is similar to the SAPSⅡ score.Conclusion:1.The incidence of thrombocytopenia in ICU patients is about 30%.APACHE Ⅱscore and RDW are independent risk factors for severe thrombocytopenia.2.The platelet count on day7(PC7)and rate of change in day7(ΔPC7%)are negatively correlated with the severity of disease in ICU patients,which are independent protective factors for the death within 28 days and 4 years.The joint index of ΔPC7%+SAPS Ⅱ score can better predict the long-term and short-term prognosis of ICU patients.3.Δ PC7%is closely related to the long-term and short-term prognosis of patients with sepsis.PC4,RDW,SAPS Ⅱ score and infection are independent risk factors for the 4-year prognosis of ICU patients with sepsis,of which the PC5 and maximum platelet count within 7 days(PCmax)are the independent protective factors.