Study On Relationship Between Blood Loss For Laboratory Tests And Prognosis Of Critical ICU Patients

Abjective: Laboratory tests are routine examinations of inpatients for guidance of diagnosis and treatment. ICU patients need intensive monitoring due to severe illness and disturbance of internal enviroments. But the blood loss due to these laboratory tests is often ignored. The relationship between blood loss for ICU tests and iatrogenic anemia was studied by quantitative analysis and its relationship with the mortality of the patients and their relating factors were also evaluated.Methods: 65 ICU patients in the first affiliated hospital of DMU were analyzed. All patients were hospitalized for at least 72 hours without traumatic blood loss. The quantity of blood loss for laboratory tests was determined by standard blood samplings and records. The APACHEⅡscores and Marshall scores were used to estimate the severity of disease. The number of dysfunction organs was used to describe the complexity of organs and systems involved during the progression of disease. The blood volume demanded in theory is determined by the formula,'B=5(∑s+0.1)','B'represents the blood volume demanded and'∑s'represents the totle amount of serum needed altogether in each test( ml) . The data analysis was done with SPSS11.5 statistically.Results: 1) Large amount of blood is drawn from ICU patients during the length of stay (LOS). The median figure was 134.50ml for each patient with the range between 32.50 ml and 751.50ml. The daily blood loss was 15.50ml ( median). There is no statistical difference whether patients had undergone surgery or not, but the blood loss in death group was statistically greater than that in alive group. 2) The haemoglobin is 112.00g/L on admission and 101.16g/L on discharge from ICU, respectively. There is statistical difference (P=0.001). About 44 (67.70%)patients had a decreased Hb level( 2.00~76.00g/L) .A supernumerary 12(18.40%) patients with Hb<100g/L was developed when they discharge from ICU compared with admission. 3) The largest proportion of the blood samples was used for clinical chemical tests( 41.75%), followed by hematologic and coagulation( 35.69%), infection( 11.27%), blood gas analyse(s 7.24%) and other test(s 4.05%).4) The blood volume demanded for tests in theory is 28.88ml(Median) per patient per day , but the practical blood loss( M 134.50ml)was statistically greater ( p<0.001). 5) Except in patients with blood transfusion over 500ml, the blood loss was associated with the change of Hb and Alb, especially in surgery patients. 6)The correlation was observed between the amount of blood drawn and the number of dysfunction organs, Marshall scores and length of stay, but not with APACHEⅡscores.7)Multivariate analysis of logistic regression and after controlling for the effects of age, length of ICU stay, APACHEⅡscores and Marshall scores revealed that the amount of blood drawing and the numbers of dysfunction organs are the influencing factors of iatrogenic anemia. 8) The correlation is observed between the mortality and the number of dysfunction organs, emergency or not and the length of ICU stay.9) Univariate analysis of logistic regression revealed that significant (P<0.001) positive correlation was observed between mortality and the number of dysfunction organs and the degree of anemia.Conclusion: At present, the blood loss for tests and iatrogenic anemia are big problems among the ICUs. Extensive amount of blood is drawn from ICU patients, which contributes to iatrogenic anemia and increased mortality. From 1970's the blood loss for tests was concerned by some scholars and strategies were raised to decrease blood loss associated with phlebotomy and arterial blood gas sampling. The amount of blood loss is decreased in the 21st century, but the iatrogenic anemia is also observed as a factor contributing to anemia in ICU patients and mortality. On the other hand, the number of dysfunction organs is significant correlated with the amount of blood loss, anemia and mortality. This indicates that the pathogenic condition is the basis. So the treatment itself is a"two blade sword". Adverse effects and iatrogenic consequences must be carefully observed while certain treatment is being carried out.