Thrombocytopenia and prognosis in intensive care

Linezolid does not increase the risk of thrombocytopenia in patients with nosocomial pneumonia: comparative analysis of linezolid and vancomycin use

Reports from uncontrolled studies suggest that linezolid is associated with rates of thrombocytopenia higher than those reported in clinical studies. We assessed the risk of thrombocytopenia in 686 patients with nosocomial pneumonia who received linezolid or vancomycin for > or =5 days in 2 randomized, double-blind studies and for whom follow-up platelet counts had been measured. New-onset thrombocytopenia (platelet count of <150x10(9) platelets/L) occurred in 19 (6.4%) of 295 linezolid recipients and 22 (7.7%) of 285 vancomycin recipients with baseline platelet counts of > or =150x10(9) platelets/L; severe thrombocytopenia (platelet count of <50x10(9) platelets/L) occurred in only 1 patient in each group. Platelet counts decreased to less than the baseline level in 4 (6.6%) of 61 linezolid recipients and 5 (11.1%) of 45 vancomycin recipients who had baseline counts of <150x10(9) platelets/L. No patient had a decrease to <20x10(9) platelets/L. There were no statistically significant differences between groups in these or any other platelet assessments. Clinically significant thrombocytopenia was uncommon in our analysis, and linezolid was not associated with a greater risk of thrombocytopenia in seriously ill patients than was vancomycin.

Impact of adequacy of initial antimicrobial therapy on the prognosis of patients with ventilator-associated pneumonia

OBJECTIVE

To study the prognostic impact of the appropriateness of initial antimicrobial therapy in patients suffering from ventilator-associated pneumonia (VAP).

DESIGN AND SETTING

Observational cohort from January 1994 to December 2001 in one intensive care unit (ICU) from an university-affiliated, urban teaching hospital.

PATIENTS

All 132 consecutive patients exhibiting bacteriologically documented VAP during ICU stay.

MEASUREMENTS AND RESULTS

Initial antimicrobial treatment was deemed appropriate when the period from initial VAP diagnosis and subsequent administration of antibiotics was within 24 h and all causative pathogens were in vitro susceptible to at least one of the antibiotics of the regimen. Such a treatment was present in 106 episodes. Fifty-eight patients died. In bivariate analysis an appropriate initial antimicrobial therapy was associated with a significantly lower mortality rate (40% vs. 62%). In multivariate analysis the three independent factors present upon VAP onset and associated with death were pulmonary involvement of more than a single lobe on chest radiograph, platelet count less than 150000/mm(3), and Simplified Acute Physiology Score II higher than 37. Appropriate antimicrobial therapy was associated with a nonsignificant trend toward a lower mortality.

CONCLUSIONS

In our cohort the mortality rate was lower in patients suffering from VAP when the initial antimicrobial therapy was appropriate. However, such a factor did not appear as an independent prognostic factor.

The hematologic system as a marker of organ dysfunction in sepsis

Sepsis with acute organ dysfunction (severe sepsis) results from a systemic proinflammatory and procoagulant response to infection. Organ dysfunction in the patient with sepsis is associated with increased mortality. Although most organs have discrete anatomical boundaries and carry out unified functions, the hematologic system is poorly circumscribed and serves several unrelated functions. This review addresses the hematologic changes associated with sepsis and provides a framework for prompt diagnosis and rational drug therapy. Data sources used include published research and review articles in the English language related to hematologic alterations in animal models of sepsis and in critically ill patients. Hematologic changes are present in virtually every patient with severe sepsis. Leukocytosis, anemia, thrombocytopenia, and activation of the coagulation cascade are the most common abnormalities. Despite theoretical advantages of using granulocyte colony-stimulating factor to enhance leukocyte function and/or circulating numbers, large clinical trials with these growth factors are lacking. Recent studies support a reduction in the red blood cell transfusion threshold and the use of erythropoietin treatment to reduce transfusion requirements. Treatment of thrombocytopenia depends on the cause and clinical context but may include platelet transfusions and discontinuation of heparin or other inciting drugs. The use of activated protein C may provide a survival benefit in subsets of patients with severe sepsis. The hematologic system should not be overlooked when assessing a patient with severe sepsis. A thorough clinical evaluation and panel of laboratory tests that relate to this organ system should be as much a part of the work-up as taking the patient's blood pressure, monitoring renal function, or measuring liver enzymes.

Platelet-endothelial interactions: sepsis, HIT, and antiphospholipid syndrome

Acquired abnormalities in platelets, endothelium, and their interaction occur in sepsis, immune heparin-induced thrombocytopenia (HIT), and the antiphospholipid syndrome. Although of distinct pathogeneses, these three disorders have several clinical features in common, including thrombocytopenia and the potential for life- and limb-threatening thrombotic events, ranging from microvascular (sepsis > antiphospholipid > HIT) to macrovascular (HIT > antiphospholipid > sepsis) thrombosis, both venous and arterial. In Section I, Dr. William Aird reviews basic aspects of endothelial-platelet interactions as a springboard to considering the common problem of thrombocytopenia (and its mechanism) in sepsis. The relationship between thrombocytopenia and other aspects of the host response in sepsis, including activation of coagulation/inflammation pathways and the development of organ dysfunction, is discussed. Practical issues of platelet count triggers and targeted use of activated protein C concentrates are reviewed. In Section II, Dr. Theodore Warkentin describes HIT as a clinicopathologic syndrome, i.e., the diagnosis should be based on the concurrence of an appropriate clinical picture together with detection of platelet-activating and/or platelet factor 4-dependent antibodies (usually in high levels). HIT is a profound prothrombotic state (odds ratio for thrombosis, 20-40), and the risk for thrombosis persists for a time even when heparin is stopped. Thus, pharmacologic control of thrombin (or its generation), and postponing oral anticoagulation pending substantial resolution of thrombocytopenia, is appropriate. Indeed, coumarin-associated protein C depletion during uncontrolled thrombin generation of HIT can explain limb loss (coumarin-associated venous limb gangrene) or skin necrosis syndromes in some patients. In Section III, Dr. Jacob Rand presents the most recent concepts on the mechanisms of thrombosis in the antiphospholipid syndrome, and focuses on the role of beta(2)-glycoprotein I as a major antigenic target in this condition. Diagnosis of the syndrome is often complicated because the clinical laboratory tests to identify this condition have been empirically derived. Dr. Rand addresses the practical aspects of current testing for the syndrome and current recommendations for treating patients with thrombosis and with spontaneous pregnancy losses.

The prognostic value of global haemostatic tests in the intensive care unit setting

BACKGROUND

Global haemostatic tests are often abnormal in critically ill patients, secondary to activation or consumption of coagulation factors or inhibitors. Methods for analysing plasma levels of these factors are, however, not widely available, and the predictive value of global tests is not known. We examined the clinical applicability to predict the outcome of the global haemostatic tests used at most hospitals.

METHODS

Blood was collected from patients within 6 h of admission to an intensive care unit (ICU) and tested regarding platelet count, International Normalized Ratio (INR), and activated partial thromboplastin time (APTT). Ninety-two patients with platelet counts <100 x 10(9) l(-1), INR > 1.36 and/or APTT >45 s were included in a study group, and an additional 92 patients with a comparable age and sex distribution, but not fulfilling these laboratory criteria, constituted a control group. The following data were recorded for each patient: number of days in the ICU and hospital; alive or deceased when released from the ICU and hospital; survival at 30 days and 180 days.

RESULTS

Survival upon discharge from the ICU and hospital was significantly reduced in the study group. This was especially pronounced in patients with medical disorders, whereas the survival rate was slightly higher in surgery patients. Expressing the survival predicting ability of the screening tests as odds ratios for all patients (study and control groups together) indicated that prolonged APTT in particular foretold a lower survival rate at studied time-points after admission to the ICU.

CONCLUSIONS

The global haemostatic tests INR and APTT can predict survival in critically ill patients, and prolonged APTT in particular seems to be associated with a negative prognosis.

Thrombocytopenia in patients in the medical intensive care unit: bleeding prevalence, transfusion requirements, and outcome

OBJECTIVE

To determine prevalence, risk factors, and outcome of thrombocytopenia in medical intensive care patients.

DESIGN

Prospective observational study.

SETTING

The 12-bed medical intensive care unit of a university hospital.

PATIENTS

All consecutively admitted patients with normal platelet count at admission and an intensive care unit stay of >48 hrs during a 13-month period (n = 145).

MEASUREMENTS AND MAIN RESULTS

The prevalence of intensive care unit-acquired thrombocytopenia (platelet count, <150.0/nL) was 64 of 145 patients (44%). Intensive care unit mortality was 31% in thrombocytopenic patients and 16% in nonthrombocytopenic patients (p =.03). Mortality was higher in patients with a nadir platelet count of <100.0/nL (p <.001) and in patients with a drop in platelet count of >/=30% (p <.001). In nonsurvivors, the decrease in platelet count was greater (p <.001), the nadir platelet count lower (p <.001), and the duration of thrombocytopenia longer (p =.008) than in survivors. A logistic regression analysis identified septic shock (odds ratio [OR], 3.65; 95% confidence interval [CI], 1.40-9.52), a higher Acute Physiology and Chronic Health Evaluation II Score at admission (OR, 1.06 for 1 point; 95% CI, 1.01-1.12), and a drop in platelet count exceeding 30% (OR, 3.73; 95% CI, 1.24-11.21), but not thrombocytopenia, as independent risk factors for intensive care unit death. Correction of thrombocytopenia was associated with reduced mortality (OR, 0.002; 95% CI, 0-0.08). Major bleeding prevalence and transfusion requirements were significantly higher with thrombocytopenia. Nadir platelet count was the only independent risk factor for bleeding (OR, 4.1 for every 100.0/nL; 95% CI, 1.9-8.8). Independently associated with thrombocytopenia were disseminated intravascular coagulation (OR, 14.94; 95% CI, 3.92-57.00), cardiopulmonary resuscitation as an admission category (OR, 5.17; 95% CI, 1.42-18.85), and a higher Sequential Organ Failure Assessment score (OR, 1.20 for a 1 point change; 95% CI, 1.02-1.40).

CONCLUSIONS

Thrombocytopenia is common in medical intensive care unit patients. Thrombocytopenic patients have a higher prevalence of bleeding and greater transfusion requirements. A drop in platelet counts of > or = 30%, but not thrombocytopenia per se, is independently associated with intensive care unit death. Serial measurements of platelet counts are important and readily available markers for monitoring the patient's condition. Any drop in platelet count requires urgent clarification. Disseminated intravascular coagulation, signs of organ failure at admission, and cardiopulmonary resuscitation are predictors of intensive care unit-acquired thrombocytopenia.

Tissue factor production not balanced by tissue factor pathway inhibitor in sepsis promotes poor prognosis

OBJECTIVE

To determine the precise relationship among tissue factor, tissue factor pathway inhibitor (TFPI), and neutrophil elastase in sepsis, as well as to test the hypothesis that low TFPI concentrations are not sufficient to prevent tissue factor-dependent intravascular coagulation, leading to multiple organ dysfunction syndrome and death.

DESIGN

Prospective, cohort study.

SETTING

General intensive care unit of tertiary care emergency department.

PATIENTS

Thirty-one consecutive patients with sepsis, classified as 15 survivors and 16 nonsurvivors. Ten normal, healthy volunteers served as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Tissue factor antigen concentration (tissue factor), TFPI, neutrophil elastase, and global variables of coagulation and fibrinolysis were measured on the day of diagnosis of sepsis, severe sepsis, and septic shock and days on 1-4 after diagnosis. The number of systemic inflammatory response syndrome criteria that patients met and the disseminated intravascular coagulation score were determined simultaneously. The results of these measurements were compared between the survivors and the nonsurvivors. In the nonsurvivors, significantly higher concentrations of tissue factor and neutrophil elastase were found compared with the survivors and control subjects. However, the TFPI values showed no difference between the two groups. No correlation was found between the peak concentrations of tissue factor and TFPI. Disseminated intravascular coagulation scores and numbers of the SIRS criteria met by the survivors significantly decreased from day 0 to day 4, but those of the nonsurvivors did not improve during the study period. The nonsurvivors showed thrombocytopenia and higher numbers of dysfunctioning organs than did the survivors.

CONCLUSIONS

We systematically elucidated the relationship between tissue factor and TFPI in patients with sepsis, severe sepsis, and septic shock. Activation of tissue factor-dependent coagulation pathway not adequately balanced by TFPI has important roles in sustaining DIC and systemic inflammatory response syndrome, and it contributes to multiple organ dysfunction syndrome and death. High concentrations of neutrophil elastase released from activated neutrophils may explain, in part, the imbalance of tissue factor and TFPI in sepsis.

Risk markers for thrombocytopenia in critically ill patients: a prospective analysis

STUDY OBJECTIVE

To identify independent risk markers for thrombocytopenia in critically ill patients.

DESIGN

Prospective, observational study.

SETTING

Eleven-bed intensive care unit-coronary care unit (ICU-CCU) in a community hospital.

PATIENTS

Three hundred sixty-two consecutive patients meeting inclusion criteria during 1 year.

INTERVENTION

Potential risk marker data were collected on admission to the ICU-CCU and for the period before development of thrombocytopenia (defined as two or more consecutive platelet counts < 150 x 10(3)/mm3 obtained at least 12 hours apart), or for the duration of ICU-CCU stay if thrombocytopenia did not develop.

MEASUREMENTS AND MAIN RESULTS

Thrombocytopenia developed in 68 patients (18.8%). Multivariate logistic regression analyses identified patients at risk on admission, but the predictive, potential of the regression model improved when all risk marker exposures during the ICU-CCU stay were considered. Independent risk markers included fresh frozen plasma administration, sepsis, musculoskeletal diagnosis, pulmonary artery catheter insertion, gastrointestinal diagnosis, packed red blood cell administration, and nonsurgical respiratory diagnosis. Higher admission platelet count and aspirin administration were associated with a lower risk of thrombocytopenia. Heparin administration was not identified as a risk marker, and no patient developed heparin-induced thrombocytopenia with thrombosis. Patients with thrombocytopenia had longer ICU-CCU and hospital stays, and higher ICU-CCU and hospital mortality than those without thrombocytopenia.

CONCLUSIONS

Development of thrombocytopenia in critically ill patients is associated with specific diagnoses, packed red cell and fresh frozen plasma transfusions, pulmonary artery catheter insertion, and admission platelet count.

Platelet function in sepsis

OBJECTIVE

To evaluate platelet function in sepsis.

DATA SOURCES

The MEDLINE database and bibliographies of selected articles.

DATA SYNTHESIS

The common occurrence of thrombocytopenia in critically ill patients has been recognized for many years and is known to be associated with an increased mortality rate. Platelet function can be divided into four areas: activation, adhesion, aggregation, and secretion. Studies have found that activated platelets secrete key components of the coagulation and inflammatory cascades and are involved in the regulation of vascular tone. However, studies on platelet function in sepsis have been scarce, and their data are often conflicting. In sepsis, aggregation of circulating platelets seems to be reduced, yet platelet receptors are present in normal amounts.

CONCLUSIONS

Platelets play a complex role in sepsis; they are able to modulate not only their own function but also that of cells around them. Further study is needed to better define the precise mechanisms and effects of platelet activation in sepsis and to determine the benefits and risks of inhibiting platelet function.

Time course of platelet counts in critically ill patients

BACKGROUND

Although thrombocytopenia in the intensive care unit (ICU) is associated with a poorer outcome, the precise relationship between the time course of platelet counts and the mortality rate has not been well defined.

OBJECTIVE

To describe the time course of the platelet count in relation to the mortality rate in critically ill patients.

DESIGN

Substudy of a prospective, multicenter, observational cohort analysis.

SETTING

Forty ICUs in 16 countries from Europe, America, and Australia.

PATIENTS

Data were collected from all ICU admissions in a 1-month period, excluding patients younger than 12 yrs old and those who stayed in the ICU for <48 hrs after uncomplicated surgery. A total of 1,449 critically ill patients were enrolled, including 257 who stayed in the ICU for >2 wks.

INTERVENTIONS

None.

MEASUREMENTS

Platelet counts were collected daily throughout the ICU stay, together with other measures of organ dysfunction. Thrombocytopenia was defined as a platelet count of <150 x 103/mm3. A relative increase in platelet count was defined as a 25% increase above the admission value, together with an absolute platelet count of > or =150 x 103/mm3.

MAIN RESULTS

For the entire population, the platelet count was lower in the 313 nonsurvivors than in the 1,131 survivors throughout the ICU course. Of the 257 patients who stayed in the ICU for >2 wks, 187 (64%) survived. The platelet count decreased significantly in the first days after admission to reach a nadir on day 4 in both survivors and nonsurvivors. In the survivors, the platelet count returned to the admission value by the end of the first week and continued to rise to become significantly greater than the admission value by day 9. In the nonsurvivors, the platelet count also returned to the admission value after 1 wk, but there was no subsequent increase in platelet count. A total of 138 (54%) patients had thrombocytopenia on day 4, and these patients had a greater mortality rate than the other patients (33% vs. 16%; p <.05). On day 14, 51 (20%) patients had thrombocytopenia, and these patients had a greater mortality rate than the other patients (66% vs. 16%; p <.05). Thrombocytopenia was less common on day 14 than on day 4 (20% vs. 54%; p <.05), but the mortality rate was greater in the thrombocytopenic patients on day 14 than those who were thrombocytopenic on day 4 (66% vs. 33%; p <.05). The ICU mortality rate of nonthrombocytopenic patients on day 14 was also significantly lower in patients with, than without, a relative increase in platelet count on day 14 (11% vs. 30%; p <.05).

CONCLUSION

Platelet count changes in the critically ill have a biphasic pattern that is different in survivors and nonsurvivors. Late thrombocytopenia is more predictive of death than early thrombocytopenia. A relative increase in platelet count after thrombocytopenia was present in survivors but not in nonsurvivors. Although a single measured platelet count is of little value for predicting outcome, changes in platelet count over time are related to patient outcome.

Predictive value of antithrombin III and serum C-reactive protein concentration in critically ill patients with suspected sepsis

OBJECTIVE

To evaluate at admission the performance of serum antithrombin III, serum C-reactive protein, white blood cell and platelet counts, and thromboplastin time values in prediction of hospital mortality rates in critically ill patients with suspected sepsis.

DESIGN

Prospective, cohort study.

SETTING

University hospital medical-surgical intensive care unit.

PATIENTS

One hundred eight consecutive critically ill patients with suspected sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The outcome measure was hospital mortality rate. Hospital survivors (n = 66) and nonsurvivors (n = 42) differed statistically significantly in admission antithrombin III activity (percentage of normal): survivors' median 66% (interquartile range, 48% to 82%) vs. nonsurvivors' median 46% (37% to 65%, p =.0002 by Mann-Whitney test). Analysis revealed similarly statistically significant differences between survivors and nonsurvivors in admission platelet count, admission thromboplastin time, day 1 Logistic Organ Dysfunction score, and Acute Physiology and Chronic Health Evaluation III score, but not in serum C-reactive protein concentrations or in white blood cells. However, the areas under the receiver operating curves (AUC) showed significantly worse discriminative power for admission antithrombin III concentration (AUC, 0.71; SE, 0.05), platelet count (AUC, 0.67; SE, 0.05), thromboplastin time (AUC, 0.65; SE, 0.05), C-reactive protein concentration (AUC, 0.60; SE, 0.05), and white blood cell count (AUC, 0.53; SE, 0.06) than did the day 1 Logistic Organ Dysfunction score (AUC, 0.82; SE, 0.04) and the Acute Physiology and Chronic Health Evaluation III score (AUC, 0.84; SE, 0.04). Multivariate logistic regression analysis revealed that only the Acute Physiology and Chronic Health Evaluation III score was independently associated with hospital mortality rate.

CONCLUSIONS

Admission antithrombin III concentrations, but not C-reactive protein concentrations, differ significantly between hospital survivors and nonsurvivors among critically ill patients with septic infection. However, in prediction of hospital mortality rate, the discriminative power of admission antithrombin III concentration is poor, as judged by analysis of areas under the receiver operating curves, and is not independently associated with hospital mortality rate.

Thrombocytosis in intensive care

We conducted a retrospective study of platelet count in 226 patients admitted for critical care over a 5-month period, to explore the incidence of thrombocytosis and its relation to admission category, duration of ICU stay and outcome. Our findings indicate that thrombocytosis is not rare in ICU patients. At least one platelet count greater than 450x10(9) litre(-1) was found in 21.7% of patients and was associated with lower ICU mortality (P=0.003), lower hospital mortality (P=0.006), but longer duration of ICU stay (P<0.0001). Thrombocytosis may serve as an independent predictor of favourable outcome in ICU patients.

Microvascular thrombosis in pediatric multiple organ failure: Is it a therapeutic target?

PURPOSE: To discuss the current rationale for the use of specific and nonspecific therapies for thrombotic microangiopathy in thrombocytopenia-associated pediatric multiple organ failure syndromes. Methods: Pertinent PubMed and MEDLINE citations and proceedings of recent critical care meeting presentations were reviewed. RESULTS: Critical care clinicians have reported using antithrombin III concentrate, protein C concentrate, activated protein C, prostacyclin and its analogues, heparin, tissue factor pathway inhibitor concentrate, plasma infusion, plasma exchange, whole blood exchange, pentoxifylline, tissue plasminogen activator, urokinase, and streptokinase with perceived therapeutic benefits in patients with thrombocytopenia-associated multiple organ failure, including those with thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, disseminated intravascular coagulation syndrome, and secondary thrombotic microangiopathy syndrome without prolonged prothrombin time/activated partial thromboplastin time. CONCLUSION: Assuming that underlying disease is remediable, a consensus has developed that thrombotic microangiopathy is a therapeutic target in children with thrombocytopenia-associated multiple organ failure syndromes. Studies are warranted to delineate efficacious use of specific and nonspecific therapies to prevent and reverse thrombotic microangiopathy in these patients.