Thrombocytopenia and prognosis in intensive care

Genetic polymorphisms in the endotoxin receptor may influence platelet count as part of the acute phase response in critically ill children

PURPOSE

To determine if common polymorphisms in the endotoxin recognition complex influence the acute phase response as determined by the development of the systemic inflammatory response syndrome (SIRS) and platelet count on admission.

METHODS

This was a prospective observational cohort study. Paediatric intensive care patients (n = 913) were genotyped for common functional polymorphisms in the endotoxin recognition complex, including Toll-like receptor 4 (TLR4). We also selected potentially confounding polymorphisms in other genes of the innate immune system. SIRS was defined by age-specific consensus criteria. Platelet counts were recorded on admission.

RESULTS

The development of SIRS was primarily determined by the nature of the insult, but carriers of TLR4 variant alleles had lower platelet counts than children with wild-type genotype [mean +/- standard error of the mean (SEM) 143 +/- 7 vs. 175 +/- 4; p = 0.0001)--independent of other innate immune system polymorphisms. These findings were validated using a patient cohort of 1,170 adults with coronary artery disease. Carriers of TLR4 polymorphisms with a history of myocardial infarction (n = 573) had lower platelet counts than those with the wild-type genotype (217 +/- 7 vs. 237 +/- 2.8; p = 0.021).

CONCLUSIONS

Our results show that TLR4 variant alleles are associated with lower platelet counts across a range of ages and precipitating insults but that they do not influence the incidence of SIRS. This result may reflect redundancy and 'robustness' in the pathways leading to SIRS or the lack of specificity of this endpoint. Platelet count may vary with TLR4 genotype because it may be sufficiently sensitive and more linearly related to inflammation than other markers or, alternatively, there may be a direct TLR4-mediated platelet effect.

Inflammation and coagulation

In the pathogenesis of sepsis, inflammation and coagulation play a pivotal role. Increasing evidence points to an extensive cross-talk between these two systems, whereby inflammation leads to activation of coagulation, and coagulation also considerably affects inflammatory activity. Molecular pathways that contribute to inflammation-induced activation of coagulation have been precisely identified. Pro-inflammatory cytokines and other mediators are capable of activating the coagulation system and down-regulating important physiologic anticoagulant pathways. Activation of the coagulation system and ensuing thrombin generation is dependent on expression of tissue factor and the simultaneous down-regulation of endothelial-bound anticoagulant mechanisms and endogenous fibrinolysis. Conversely, activated coagulation proteases may affect specific cellular receptors on inflammatory cells and endothelial cells and thereby modulate the inflammatory response.

Thrombocytopenia in the intensive care unit patient

The many comorbidities in the severely ill patient also make thrombocytopenia very common (∼40%) in intensive care unit patients. The risk of bleeding is high with severe thrombocytopenia and is enhanced in intensive care patients with mild or moderately low platelet counts when additional factors are present that interfere with normal hemostatic mechanisms (eg, platelet function defects, hyperfibrinolysis, invasive procedures, or catheters). Even if not associated with bleeding, low platelet counts often influence patient management and may prompt physicians to withhold or delay necessary invasive interventions, reduce the intensity of anticoagulation, order prophylactic platelet transfusion, or change anticoagulants due to fear of heparin-induced thrombocytopenia. One approach to identify potential causes of thrombocytopenia that require specific interventions is to consider the dynamics of platelet count changes. The relative decrease in platelet counts within the first 3 to 4 days after major surgery is informative about the magnitude of the trauma or blood loss, whereas the dynamic of the platelet count course thereafter shows whether or not the physiologic compensatory mechanisms are working. A slow and gradual fall in platelet counts developing over 5 to 7 days is more likely to be caused by consumptive coagulopathy or bone marrow failure, whereas any abrupt decrease (within 1-2 days) in platelet counts manifesting after an initial increase in platelet counts approximately 1 to 2 weeks after surgery strongly suggests immunologic causes, including heparin-induced thrombocytopenia, other drug-induced immune thrombocytopenia, and posttransfusion purpura.

Coagulopathy in critically ill patients: part 1: platelet disorders

Abnormalities of platelet number and function are the most common coagulation disorders seen among ICU patients. This article reviews the most frequent causes of thrombocytopenia by providing an overview of the following most common mechanisms: impaired production; sequestration; dilution; and destruction. Guidelines for treating thrombocytopenia and platelet dysfunction are also provided.

Abnormal coagulation tests are associated with progression of traumatic intracranial hemorrhage

BACKGROUND

Intracranial hemorrhage (ICH) is common in traumatic brain injury (TBI) and a major determinant of death and disability. ICH commonly increases in size and coagulopathy has been implicated in such progression. We investigated the association between coagulopathy diagnosed by routine laboratory tests and ICH progression.

METHODS

Subgroup post hoc analysis from a randomized controlled trial including adult patients with blunt severe TBI (Glasgow Coma Scale score <or=8) and repeat computerized tomography scans in 48 hours. Coagulopathy was defined as international normalized ratio >or=1.3, activated partial thromboplastin time >or=35, or platelet count (PLT) <or=100 x 10/L any time in the first 24 hours. Progression was any size increase or new ICH. TBI-associated coagulopathy was investigated measuring soluble tissue factor (TF) and d-dimer.

RESULTS

The ICH progressed in 37 of 72 patients (51%), in 80% if any abnormal laboratory test (coagulopathic patients) versus 36% in noncoagulopathic (p = 0.0004). Abnormal international normalized ratio (odds ratio [OR] = 4.09; 95% confidence interval [CI] = 1.29-12.95; p = 0.017), PLT (OR = 12.59; 95% CI = 1.52-108.57; p = 0.019), head Abbreviated Injury Scale (AIS) (OR = 1.82; 95% CI = 1.15-2.88; p = 0.011) were significantly associated with progression (univariate analysis). In a multiple logistic regression, only head AIS (OR = 1.81; 95% CI 1.10-2.98; p = 0.0198) and PLT (OR = 11.8; 95% CI = 1.38-101.23; p = 0.024) correlated with progression. All patients with abnormal partial thromboplastin time experienced progression. ICH progression carried a 5-fold higher odds of death; 32% with progression died versus 8.6% without. Age, head AIS, Injury Severity Score, and d-dimer were also associated with mortality. Tissue factor was not associated with progression or mortality.

CONCLUSION

This study demonstrates an association between coagulopathy, diagnosed by routine laboratorial tests in the first 24 hours, with ICH progression; and ICH progression with mortality in patients with severe TBI. The causal relationship between coagulopathy and ICH progression will require further studies.

Six-month follow-up of patients with in-hospital thrombocytopenia during heparin-based anticoagulation (from the Complications After Thrombocytopenia Caused by Heparin [CATCH] registry)

Thrombocytopenia is a predictor of adverse outcomes in patients with acute coronary syndromes and in critically ill patients. The Complications After Thrombocytopenia Caused by Heparin (CATCH) registry was designed to explore the incidence, management, and clinical consequences of in-hospital thrombocytopenia occurring during heparin-based anticoagulation in diverse clinical settings. We conducted a prospective observational study of 37 United States hospitals participating in the CATCH registry to assess the relation of in-hospital thrombocytopenia to long-term outcomes. A total of 2,104 patients at increased risk of developing in-hospital thrombocytopenia or thrombosis were identified, and the 6-month mortality and rehospitalization rates were determined. Thrombocytopenia was not a significant predictor of 6-month mortality. In an adjusted model for in-hospital death in this cohort, thrombocytopenia had an odds ratio of 3.59 (95% confidence interval 2.24 to 5.77). The postdischarge mortality rate at 6 months was 9.7%. No significant difference was observed in the long-term mortality between patients who developed thrombocytopenia and those who did not. Thrombocytopenia was a weak, but statistically significant, predictor of a composite of mortality and rehospitalization at 6 months (hazards ratio 0.80, 95% confidence interval 0.65 to 0.98, p = 0.03). In conclusion, the 6-month mortality rate among heparin-treated patients with thrombocytopenia is high, although the risk independently related to thrombocytopenia appears to be restricted to the acute hospital phase.

Recent progress of proteomics in critical illness

Critical illness, such as sepsis or septic shock with multiple organ dysfunction syndrome, is the leading cause of morbidity and mortality in intensive care units. The complexity of critical illness requires a robust methodology to explore the underlying mechanisms. Proteomics represents a powerful postgenomic biotechnology used for simultaneous examination of a large number of proteins or the proteome. Recent progress in proteomic techniques allows thorough evaluation of molecular changes associated with critical illness, thereby permitting to identify novel biomarkers and therapeutic targets. This review provides an update on the recent progress and potential of rapidly evolving proteomics approach to facilitate new discoveries in the field of critical care medicine.

IL-1beta, IL-6, and RANTES as biomarkers of Chikungunya severity

Background

Little is known about the immunopathogenesis of Chikungunya virus. Circulating levels of immune mediators and growth factors were analyzed from patients infected during the first Singaporean Chikungunya fever outbreak in early 2008 to establish biomarkers associated with infection and/or disease severity.

Methods and Findings

Adult patients with laboratory-confirmed Chikungunya fever infection, who were referred to the Communicable Disease Centre/Tan Tock Seng Hospital during the period from January to February 2008, were included in this retrospective study. Plasma fractions were analyzed using a multiplex-microbead immunoassay. Among the patients, the most common clinical features were fever (100%), arthralgia (90%), rash (50%) and conjunctivitis (40%). Profiles of 30 cytokines, chemokines, and growth factors were able to discriminate the clinical forms of Chikungunya from healthy controls, with patients classified as non-severe and severe disease. Levels of 8 plasma cytokines and 4 growth factors were significantly elevated. Statistical analysis showed that an increase in IL-1β, IL-6 and a decrease in RANTES were associated with disease severity.

Conclusions

This is the first comprehensive report on the production of cytokines, chemokines, and growth factors during acute Chikungunya virus infection. Using these biomarkers, we were able to distinguish between mild disease and more severe forms of Chikungunya fever, thus enabling the identification of patients with poor prognosis and monitoring of the disease.

Thrombotic thrombocytopenic purpura associated with severe acute pancreatitis in a context of decreased ADAMTS13 activity: a case report

Thrombotic thrombocytopenic purpura (TTP) is a severe multisystemic microvascular disease defined by the association of hemolytic anemia, thrombocytopenia, acute renal failure, fever, and neurological disorders. The pathophysiology has recently been elucidated by the discovery of a von Willebrand factor-cleaving protease (ADAMTS13) deficiency involved in platelet aggregation and ischemia. The association between TTP and acute pancreatitis (AP) has rarely been reported, described either as a cause or a consequence. The role of ADAMTS13 during AP is still unknown. We describe the case of a 41-year-old woman who developed a TTP, with decreased ADAMTS13 activity, associated with severe AP. Published cases of thrombotic microangiopathy associated with AP are reviewed. The pathophysiology, management, prognostic factors, and rationale for treatment are discussed. AP should be sought in patients with TTP presenting with abdominal pain. On the other hand, TTP should be considered in patients with AP and thrombocytopenia.

Implications of thrombocytopenia and platelet course on pediatric intensive care unit outcomes

INTRODUCTION

Thrombocytopenia has been shown to be an independent predictor of mortality and prolonged hospital length of stay in critically ill adults. Studies are lacking in the pediatric intensive care unit population. We evaluated the relationship between platelet counts at admission, platelet course, and outcomes.

HYPOTHESES

1) Thrombocytopenia at the time of admission to the pediatric intensive care unit is a risk factor for increased mortality and prolonged length of stay. 2) Thrombocytopenia at any point during pediatric intensive care unit stay is associated with increased mortality and length of stay. 3) Falling platelet counts during a pediatric intensive care unit course are associated with greater mortality and longer length of stay.

METHOD

Prospective observational study.

STUDY POPULATION

All patients admitted to a multidisciplinary tertiary care pediatric intensive care unit in a University Hospital over the course of a year. ANALYSIS OF DATA: Data were analyzed using logistic and linear regression.

RESULTS

Thrombocytopenia (platelet count <150 x 10/L) was present in 17.3% of pediatric intensive care unit patients on admission. Mortality was higher in thrombocytopenic patients (17.6% vs. 2.47%, p < 0.001). The median length of stay in the thrombocytopenia and nonthrombocytopenia groups was 4 days vs. 1.6 days, respectively (p < 0.001). The pediatric intensive care unit patients (25.3%) were thrombocytopenic at some point in their stay. They had higher mortality (17.1% vs. 0.9%, odds ratio [OR] 23.8, 95% confidence interval [CI] 5.2-108.6, p < 0.0005) and longer length of stay (median 6.6 days vs. 1.5 days, p < 0.0005) compared with those who were never thrombocytopenic. For every 10% fall in platelet count from the time of admission, the OR for mortality was 1.4 (95% CI 1.1-1.8) and the length of stay was longer (p < 0.0005). Patients with normal platelet counts at admission who later developed thrombocytopenia had increased mortality (OR 18.6, 95% CI 3.2-107.3) and longer length of stay (p < 0.0005) compared with those who did not develop thrombocytopenia.

CONCLUSION

Thrombocytopenia and falling platelet counts are associated with increased risk of mortality and length of stay in the pediatric intensive care unit.

Thrombocytopenia at baseline is a predictor of inhospital mortality in patients undergoing percutaneous coronary intervention

BACKGROUND

Thrombocytopenia (TP) is a common baseline abnormality in patients undergoing percutaneous coronary intervention (PCI). Whether TP has any influence on the outcome of PCI patients is unknown. Our aim was to determine if TP at baseline impacts on inhospital mortality in patients undergoing PCI at our institution.

METHODS

From April 2000 until October 2005, 11,021 PCI procedures were performed at the University Health Network in Toronto, Canada. Baseline platelet count was recorded in 10,821 (98.2%) cases. Patients with platelets <150 x 10(9)/L were assigned to the TP group (n = 639), and those with > or =150 x 10(9)/L to the normal platelet group (n = 10,182). Clinical, angiographic, procedural, and inhospital outcome data were collected prospectively. Multivariable analysis was performed using logistic regression.

RESULTS

In-hospital death rate was higher in the TP group (1.9% vs 0.6%, P < .001) due to an increased mortality in TP patients undergoing urgent (3.55% vs 1.15%, P < .001) but not elective (0% vs 0.04%, P = 1.0) PCI. Major bleeding (1.7% vs 0.8%, P < .05) and gastrointestinal bleeding (1.1% vs 0.5%, P < .05) complications were greater in the TP group. Multivariate analysis demonstrated that baseline TP was an independent predictor of inhospital mortality (odds ratio 2.07 [1.1-4.1], P = .035).

CONCLUSIONS

Baseline TP is an independent predictor of inhospital mortality in patients undergoing PCI for urgent indications. Thrombocytopenia should be considered an important addition to PCI risk prediction models to improve their precision and clinical applicability.

The clinical diagnosis of heparin-induced thrombocytopenia in patients receiving continuous renal replacement therapy

BACKGROUND

Thrombocytopenia is common in critically ill patients who receive continuous renal replacement therapy. Often, these patients receive heparin therapy and the diagnosis of heparin induced thrombocytopenia (HIT) is considered as a potential etiology. No data regarding the clinical diagnosis of HIT is available for patients receiving continuous renal replacement therapy.

PATIENTS AND METHODS

We performed a retrospective study of 29 consecutive patients who received CRRT in a medical-surgical intensive care unit (ICU) and determined trends in platelet counts following CRRT and the frequency of meeting platelet based clinical criteria for consideration of a HIT diagnosis.

RESULTS

For patient exposures to CRRT concurrent with heparin, 54% met at least one clinical threshold for consideration of the diagnosis of HIT. In 31% of exposures, both a platelet count <100,000/mm3 and a >50% decrease from baseline were seen. In contrast, the majority (73-85%) of patients receiving CRRT had a low pre-test probability of HIT using the "4T's" scoring system. Mean platelet counts while on CRRT concurrent with heparin were significantly lower than when patients received heparin alone (P < 0.02).

CONCLUSIONS

The clinical diagnosis of HIT in ICU patients initiating CRRT is challenging given the decrease in platelet counts seen following CRRT initiation in the majority of patients. A prospective study in this population is needed to optimize patient outcomes.

Severe sepsis and septic shock in the emergency department

Increased attention has focused recently on the acute management of severe sepsis and septic shock, conditions that represent the end-stage systemic deterioration of overwhelming infection. Clinical trials have identified new therapies and management approaches that, when applied early, appear to reduce mortality. Practice guidelines have been advanced by critical care societies, and many of the proposed interventions involve therapies other than antimicrobials directed at hemodynamic resuscitation or addressing adverse effects of the inflammatory cascade. Although many emergency departments (EDs) are now adopting treatment protocols for sepsis that are based on published treatment guidelines, recent research calls many of the initial recommendations into question, and validation trials of some of these approaches are ongoing. This article reviews the initial evaluation and treatment considerations of sepsis in the ED setting.

SIRS-associated coagulopathy and organ dysfunction in critically ill patients with thrombocytopenia

BACKGROUND

Coagulopathy and thrombocytopenia often occur in critically ill patients, and disseminated intravascular coagulation (DIC) can lead to multiple organ dysfunction and a poor outcome. However, the relation between coagulopathy and systemic inflammatory response has not been thoroughly clarified. Thus, we evaluated coagulative activity, organ dysfunction, and systemic inflammatory response syndrome (SIRS) in critically ill patients with thrombocytopenia and examined the balance between coagulopathy and systemic inflammation.

PATIENTS AND METHODS

Two hundred seventy-three patients, who were admitted to 13 critical care centers in Japan and fulfilled the criteria of platelet count of less than 150*10(9)/L, were included. Coagulative variables (platelet count, fibrin/fibrinogen degradation products, and DIC scores), organ dysfunction index (Sequential Organ Failure Assessment [SOFA] score), and SIRS score in each patient were evaluated for 4 consecutive days after fulfilling the above entry criteria. The effect of SIRS on coagulopathy and organ dysfunction was evaluated in these patients.

RESULTS

Both the maximum SIRS score and entry SIRS score had significant relation to the maximum SOFA score during the observation period. Coagulation disorders indicated by the minimum platelet count, maximum DIC scores, and positivity for DIC worsened gradually with increases in SIRS scores. Both the minimum platelet count and maximum DIC scores were significantly correlated with the maximum SOFA score, indicating that a relation exists between coagulopathy and organ dysfunction.

CONCLUSIONS

In critically ill patients with thrombocytopenia, coagulopathy and organ dysfunction progress with significant mutual correlation, depending on the increase in SIRS scores. The SIRS-associated coagulopathy may play a critical role in inducing organ dysfunction after severe insult.

Disseminated intravascular coagulation

OBJECTIVE

To review the current knowledge on the clinical manifestation, pathogenesis, diagnosis, and management of disseminated intravascular coagulation (DIC).

DATA SOURCE

Selected articles from the MEDLINE database.

DATA SYNTHESIS

DIC may complicate a variety of disorders and can cause significant morbidity (in particular related to organ dysfunction and bleeding) and may contribute to mortality. The pathogenesis of DIC is based on tissue factor-mediated initiation of systemic coagulation activation that is insufficiently contained by physiologic anticoagulant pathways and amplified by impaired endogenous fibrinolysis. The diagnosis of DIC can be made using routinely available laboratory tests and scoring algorithms. Supportive treatment of DIC may be aimed at replacement of platelets and coagulation factors, anticoagulant treatment, and restoration of anticoagulant pathways.

CONCLUSIONS

Insight into the pathogenesis of DIC has resulted in better strategies for clinical management, including straightforward diagnostic criteria and potentially beneficial supportive treatment options.

Impact of thrombocytopenia on outcome of patients admitted to ICU for severe community-acquired pneumonia

OBJECTIVE

To evaluate the prevalence and the prognostic value of thrombocytopenia in patients admitted to ICU for severe community-acquired pneumonia.

METHODS

Multicentre observational study was conducted in 7 ICUs in the north of France over a 19-year period (1987-2005). The primary outcome measure was the ICU mortality.

RESULTS

Eight hundred and twenty-two patients were studied. A platelet count < 150x10(9)/L was observed at ICU admission in 202 (25%) patients. Admission platelet count was between 101 and 149x10(9)/L, 51 and 100x10(9)/L, 21 and 50x10(9)/L, and < or = 20x10(9)/L in 100, 61, 32 and 9 patients, respectively. ICU mortality rate was 35.4%. Classifying patients into 3 categories with the following cut-offs of platelet count, > or = 150x10(9)/L, 51-149x10(9)/L, and < or = 50x10(9)/L, we observed a significant increase in ICU mortality rates which were 30.8% in the first group, 44.1% in the second group and 70.7% in the last one (p<0.0001). In multivariate analysis, thrombocytopenia < or = 50x10(9)/L appeared as an independent predictor of mortality (AOR=4.386).

CONCLUSIONS

In patients admitted to ICU for severe community-acquired pneumonia, thrombocytopenia has a high prevalence and influences the outcome.

Platelet count decline: an early prognostic marker in critically ill patients with prolonged ICU stays

BACKGROUND

Thrombocytopenia is common in ICU patients. The objective of this study was to evaluate possible links between declining platelet counts early in the ICU stay and survival.

METHODS

All patients who were admitted to the ICU for at least 5 days and had no thrombocytopenia at the time of admission were included in the study. A multivariable logistic regression model, with hospital mortality as the outcome variable, was built.

RESULTS

We included 1,077 patients in the study. At ICU admission, the median platelet count was not significantly different in survivors (256 x 10(9) cells/L; interquartile range [IQR], 206 to 330 x 10(9) cells/L) and nonsurvivors (262 x 10(9) cells/L; 211 to 351 x 10(9) cells/L). Median simplified acute physiology scores II (SAPS II) at ICU admission was worse in nonsurvivors than in survivors (50 [IQR, 37 to 63] vs 37 [IQR, 27 to 48], respectively; p < 0.0001), as was the mean (+/- SD) sequential organ failure assessment (SOFA) score on day 3 (6.3 +/- 3.24 vs 4 +/- 2.8, respectively; p < 0.0001). Absolute platelet counts were lowest on day 4, but differed significantly between survivors and nonsurvivors only on day 7. Conversely, any percentage decline in platelet counts from 10 to 60% on day 4 was significantly associated with mortality. By multivariable analysis, a 30% decline in platelet count independently predicted death (odds ratio, 1.54; 95% confidence interval, 1.12 to 2.14; p = 0.008), in addition to increasing or stable SOFA scores from ICU admission to day 4, older age, male gender, ICU admission for coma, worse SAPS II score at ICU admission, transfer from another ward, and comorbidity.

CONCLUSION

In patients who spend > 5 days in the ICU and have normal platelet counts at ICU admission, a decline in platelet counts provides prognostic information. This parameter deserves to be included in new scoring systems.

Bench-to-bedside review: thrombocytopenia-associated multiple organ failure--a newly appreciated syndrome in the critically ill

New onset thrombocytopenia and multiple organ failure (TAMOF) presages poor outcome in critical illness. Patients who resolve thrombocytopenia by day 14 are more likely to survive than those who do not. Patients with TAMOF have a spectrum of microangiopathic disorders that includes thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation (DIC) and secondary thrombotic microanigiopathy (TMA). Activated protein C is effective in resolving fibrin-mediated thrombosis (DIC); however, daily plasma exchange is the therapy of choice for removing ADAMTS 13 inhibitors and replenishing ADAMTS 13 activity which in turn resolves platelet: von Willebrand Factor mediated thrombosis (TTP/secondary TMA).

La thrombopénie en réanimation chirurgicale: incidence, analyse des facteurs de risque et impact sur le pronostic

OBJECTIVE

To determine the incidence of thrombocytopenia in a surgical intensive care unit (ICU), the risk factors associated with it, and its effect on patient outcome.

METHODS

During a 6-month period, all patients admitted to the surgical intensive care unit were studied prospectively. The factors associated with thrombocytopenia were evaluated by univariate and multivariate analysis.

RESULTS

The study included 112 patients with a mean age of 50+/-18 years and a mean SAPS II (Simplified Acute Physiology Score) of 25+/-19: 41 developed thrombocytopenia (incidence=36,6%). Risk factors associated with it in the univariate analysis were high SAPS II, high organ dysfunction score, invasive intravascular catheters, sepsis, septic shock, and bleeding. After multivariate logistic regression analysis, only 3 independent risk factors remained for thrombocytopenia: bleeding (OR=11.9; 95% CI: 3.3-43.6; p<0.001), sepsis (OR=4.1; 95% CI: 1.3-11.7; p=0.013) and SAPS II>20 (OR=2.8; 95% CI: 1.0-7.8; p=0.042). Although mortality was higher in patients with than without thrombocytopenia , this difference was not statistically significant (41% versus 31%, p=0.26). Survival was similar in both groups, according to the Kaplan-Meier survival curve.

CONCLUSION

Thrombocytopenia is common in surgical ICUs. Bleeding and sepsis are the major risk factors. In this study, thrombocytopenia was not an independent factor of poor vital outcome in these critically ill patients.

Heparin-induced thrombocytopenia in the critical care setting: Diagnosis and management^

BACKGROUND

Thrombocytopenia is a common occurrence in critical illness, reported in up to 41% of patients. Systematic evaluation of thrombocytopenia in critical care is essential to accurate identification and management of the cause. Although sepsis and hemodilution are more common etiologies of thrombocytopenia in critical illness, heparin-induced thrombocytopenia (HIT) is one potential etiology that warrants consideration.

OBJECTIVE

This review will summarize the pathogenesis and clinical consequences of HIT, describe the diagnostic process, and review currently available treatment options.

DATA SOURCE

MEDLINE/PubMed search of all relevant primary and review articles.

DATA SYNTHESIS AND CONCLUSIONS

HIT is a clinicopathologic syndrome characterized by thrombocytopenia (>/=50% from baseline) that typically occurs between days 5 and 14 after initiation of heparin. This temporal profile suggests a possible diagnosis of HIT, which can be supported (or refuted) with a strong positive (or negative) laboratory test for HIT antibodies. When considering the diagnosis of HIT, critical care professionals should monitor platelet counts in patients who are at risk for HIT and carefully evaluate for, a) temporal features of the thrombocytopenia in relation to heparin exposure; b) severity of thrombocytopenia; c) clinical evidence for thrombosis; and d) alternative etiologies of thrombocytopenia. Due to its prothrombotic nature, early recognition of HIT and prompt substitution of heparin with a direct thrombin inhibitor (e.g., argatroban or lepirudin) or the heparinoid danaparoid (where available) reduces the risk of thromboembolic events, some of which may be life-threatening.

Coagulation abnormalities in critically ill patients

Many critically ill patients develop hemostatic abnormalities, ranging from isolated thrombocytopenia or prolonged global clotting tests to complex defects, such as disseminated intravascular coagulation. There are many causes for a deranged coagulation in critically ill patients and each of these underlying disorders may require specific therapeutic or supportive management. In recent years, new insights into the pathogenesis and clinical management of many coagulation defects in critically ill patients have been accumulated and this knowledge is helpful in determining the optimal diagnostic and therapeutic strategy.

Circulating complement (C3 and C4) for differentiation of SIRS from sepsis

The systemic inflammatory response of the body to invading microorganisms, called sepsis, leads to profound activation of the complement (C3 and C4) system. The present study was conducted to compare the use of serum C3 and C4 levels with C-reactive protein (CRP) and thrombocyte and leukocyte counts in differentiating patients with systemic inflammatory response syndrome (SIRS) from those with sepsis. Over a 6-mo period, all patients with SIRS or sepsis who stayed in the intensive care unit for >24 h were enrolled in the study. At admission, each patient's clinical status was recorded, and blood was taken for laboratory analysis (complete blood count, CRP, C3, and C4). A total of 58 patients with SIRS and 41 patients with sepsis were admitted to the study. The mean+/-SD thrombocyte count was found to be significantly lower in septic patients (179,975+/-95,615) than in those with SIRS (243,165+/-123,706) (P=.005); no difference in plasma concentrations of CRP and levels of C3 and C4 was noted between groups. The thrombocyte count was determined to be the most reliable parameter for differentiating between SIRS and sepsis (highest area under the curve=0.656).

Serum osmolality and outcome in intensive care unit patients

BACKGROUND

The aim of the present study was to compare 16 routine clinical and laboratory parameters, acute physiologic and chronic health evaluation (APACHE) and sequential organ failure assessment (SOFA) score for their value in predicting mortality during hospital stay in patients admitted to a general intensive care unit (ICU).

METHODS

A retrospective observational clinical study was carried out in a 15-bed ICU in a university hospital. Nine hundred and thirty-three consecutive patients with ICU stay > 24 h (36.2% surgical, 29.1% medical and 34.7% trauma) were observed. Blood sampling, patient surveillance and data collection were performed. The primary outcome was mortality in the hospital. We used receiver operating characteristic (ROC) analyses and logistic regression to compare the 16 relevant parameters, APACHE II and SOFA scores.

RESULTS

Two hundred and thirty-three out of the 933 patients died (mortality 25.0%). One laboratory parameter, serum osmolality [area under the curve (AUC) 0.732] had a predictive value for mortality which lay between that of APACHE II (AUC 0.784) and SOFA (AUC 0.720) scores. When outcome prediction was restricted to long-term patients (ICU stay > 5 days), serum osmolality (AUC 0.711) performed better than either of the standard scores (APACHE AUC 0.655, SOFA AUC 0.636). Using logistic regression analysis, the association of clinical parameters, age and diagnosis group with mortality was determined.

CONCLUSION

Elevated serum osmolality at ICU admission is associated with an increased mortality risk in critically ill patients. Serum osmolality is cheaper and more rapid to determine than the scoring systems. However, further studies are needed to evaluate the predictive value of serum osmolality in different patient populations.

Utilization of platelet transfusions in the intensive care unit: indications, transfusion triggers, and platelet count responses

BACKGROUND

A description of current platelet (PLT) transfusion practice in the intensive care unit (ICU) is needed.

STUDY DESIGN AND METHODS

All thrombocytopenic patients (PLT count, <150 x 10(9)/L) who received PLT transfusions were identified from a previous prospective study of consecutive medical-surgical ICU patients; trauma, orthopedic, and cardiac surgery were exclusions. Risk factors for ineffective transfusions were examined.

RESULTS

Of 261 ICU patients, 118 (45.2%) had thrombocytopenia and a PLT count nadir of less than 50 x 10(9) per L (n = 22), 50 to 99 x 10(9) per L (n = 37), and 100 to 149 x 10(9) per L (n = 59). Twenty-seven (22.9%) patients received PLT transfusions (n = 76 transfusions) and 37 (31.4%) had major bleeding. PLT dose was approximately 3 to 4 x 10(11) per L transfusion. Therapeutic (n = 24) and prophylactic (n = 52) PLT transfusion triggers were 51 x 10(9) per L (interquartile range [IQR], 26 to 68) and 41 x 10(9) per L (IQR, 20 to 57), respectively, as measured at a median of 4.5 hours (IQR, <1.6 to 6.9) before transfusion. A single PLT transfusion resulted in a median PLT increase of 14 x 10(9) per L (IQR, -2 to 30) measured at 5.2 hours (IQR, 1.8 to 8.8) after the transfusion; however, no PLT count increase was observed after 17 transfusions given to 13 (48.1%) patients. No risk factors for ineffective transfusions were identified.

CONCLUSIONS

Among critically ill patients, most PLT transfusions were administered to prevent, rather than to treat, bleeding, with a transfusion trigger of 40 to 50 x 10(9) per L. Nearly half of ICU patients who received transfusions failed to mount a PLT count increase after a single transfusion. Prospective studies are needed to determine the effects of PLT transfusions on bleeding and predictors of ineffective transfusions in the ICU.

Acute Physiology and Chronic Health Evaluation (APACHE) IV: hospital mortality assessment for today's critically ill patients

OBJECTIVE

To improve the accuracy of the Acute Physiology and Chronic Health Evaluation (APACHE) method for predicting hospital mortality among critically ill adults and to evaluate changes in the accuracy of earlier APACHE models.

DESIGN

: Observational cohort study.

SETTING

A total of 104 intensive care units (ICUs) in 45 U.S. hospitals.

PATIENTS

A total of 131,618 consecutive ICU admissions during 2002 and 2003, of which 110,558 met inclusion criteria and had complete data.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We developed APACHE IV using ICU day 1 information and a multivariate logistic regression procedure to estimate the probability of hospital death for randomly selected patients who comprised 60% of the database. Predictor variables were similar to those in APACHE III, but new variables were added and different statistical modeling used. We assessed the accuracy of APACHE IV predictions by comparing observed and predicted hospital mortality for the excluded patients (validation set). We tested discrimination and used multiple tests of calibration in aggregate and for patient subgroups. APACHE IV had good discrimination (area under the receiver operating characteristic curve = 0.88) and calibration (Hosmer-Lemeshow C statistic = 16.9, p = .08). For 90% of 116 ICU admission diagnoses, the ratio of observed to predicted mortality was not significantly different from 1.0. We also used the validation data set to compare the accuracy of APACHE IV predictions to those using APACHE III versions developed 7 and 14 yrs previously. There was little change in discrimination, but aggregate mortality was systematically overestimated as model age increased. When examined across disease, predictive accuracy was maintained for some diagnoses but for others seemed to reflect changes in practice or therapy.

CONCLUSIONS

APACHE IV predictions of hospital mortality have good discrimination and calibration and should be useful for benchmarking performance in U.S. ICUs. The accuracy of predictive models is dynamic and should be periodically retested. When accuracy deteriorates they should be revised and updated.

Severe sepsis and septic shock: review of the literature and emergency department management guidelines

Severe sepsis and septic shock are as common and lethal as other acute life-threatening conditions that emergency physicians routinely confront such as acute myocardial infarction, stroke, and trauma. Recent studies have led to a better understanding of the pathogenic mechanisms and the development of new or newly applied therapies. These therapies place early and aggressive management of severe sepsis and septic shock as integral to improving outcome. This independent review of the literature examines the recent pathogenic, diagnostic, and therapeutic advances in severe sepsis and septic shock for adults, with particular relevance to emergency practice. Recommendations are provided for therapies that have been shown to improve outcomes, including early goal-directed therapy, early and appropriate antimicrobials, source control, recombinant human activated protein C, corticosteroids, and low tidal volume mechanical ventilation.

Do we have reliable biochemical markers to predict the outcome of critical illness?

Current outcome prediction in critically ill patients relies on the art of clinical judgement and/or the science of prognostication using illness severity scores. The biochemical processes underlying critical illness have increasingly been unravelled. Several biochemical markers reflecting the process of inflammation, immune dysfunction, impaired tissue oxygenation and endocrine alterations have been evaluated for their predictive power in small subpopulations of critically ill patients. However, none of these parameters has been validated in large populations of unselected ICU patients as has been done for the illness severity and organ failure scores. A simple biochemical predictor of ICU mortality will probably remain elusive because the processes underlying critical illness are very complex and heterogeneous. Future prognostic models will need to be far more sophisticated.

Thrombocytopenia in medical-surgical critically ill patients: prevalence, incidence, and risk factors

OBJECTIVE

The purpose of this study is to describe the prevalence, to analyze the incidence and independent risk factors for thrombocytopenia, and to examine the impact of thrombocytopenia developing in the intensive care unit (ICU) on patient outcome in a well-defined cohort of critically ill patients in a medical-surgical ICU.

MATERIALS AND METHODS

As part of a prospective cohort study examining the frequency and clinical importance of venous thromboembolism in the ICU, we enrolled consecutive patients older than 18 years expected to be in the ICU for more than 72 hours. Exclusion criteria were an admitting diagnosis of trauma, orthopedic surgery or cardiac surgery, pregnancy, and life support withdrawal. Patients had platelet counts performed as directed by clinical need. We defined thrombocytopenia as a platelet count of less than 150 x 10(9)/L and severe thrombocytopenia as a platelet count of less than 50 x 10(9)/L. Protocol-directed care included routine thromboprophylaxis and twice weekly screening ultrasonography of the legs. Patients were followed to hospital discharge.

RESULTS

Of the 261 enrolled patients, 121 (46%, 95% confidence interval [CI], 40%-53%) had thrombocytopenia (62 on ICU admission and 59 acquired during their ICU stay). Patients who developed a platelet count less than 150 x 10(9)/L during their ICU stay had higher ICU and hospital mortality (P = .03 and .005, respectively), required longer mechanical ventilation (P = .05), and were more likely to receive platelets (P < .001), fresh frozen plasma (P = .005), and red blood cell transfusions (P = .004) than patients who did not develop thrombocytopenia. The only independent risk factors for thrombocytopenia developing during the ICU stay were administration of nonsteroidal anti-inflammatory drugs before ICU admission (hazard ratio, 2.8; 95% CI, 1.3-6.0) and dialysis during the ICU stay (hazard ratio, 3.1; 95% CI, 1.2-7.8). Of the 33 patients who underwent 36 tests for heparin-induced thrombocytopenia, none tested positive.

CONCLUSIONS

We found that about 50% of the patients admitted to the ICU had at least one platelet count of less than 150 x 10(9)/L during their ICU stay. Patients who developed thrombocytopenia were more likely to die, required longer duration of mechanical ventilation, and were more likely to require blood product transfusion. Heparin-induced thrombocytopenia was frequently suspected but did not develop in these critically ill patients.

Prognostic value of a simple evolving disseminated intravascular coagulation score in patients with severe sepsis

OBJECTIVE

We postulated that the coagulopathy initiated by the inflammatory response to severe sepsis would be reflected by changes in the platelet count and prothrombin time that convey prognostic information. To examine this hypothesis, we looked at the utility of a simple evolving disseminated intravascular coagulation (DIC) score that awarded 1 point for each of the following: a) an absolute platelet count <100 x 10/L; b) a prothrombin time >15.0 secs; c) a 20% decrease in platelets; and d) a >0.3-sec increase in prothrombin time in predicting outcome in patients with severe sepsis.

DESIGN

Prospective observational study.

SETTING

Intensive care units of university medical center.

PATIENTS

Patients were 163 critically ill severe sepsis patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were clinically classified as having capillary leak syndrome (n = 24), multiple organ failure with death from sepsis (n = 37), or multiple organ failure with recovery (n = 57) or as well (n = 45) if they showed rapid improvement in their modified Multiple Organ Dysfunction Syndrome (MODS) score (which did not score for thrombocytopenia). Patients with capillary leak syndrome had the highest Acute Physiology and Chronic Health Evaluation II score, modified MODS, and prothrombin time and the lowest platelet counts, whereas well patients had the most normal values. The simple evolving DIC score increased with worsening clinical class and was associated with worsening organ failure (increased modified MODS). Mortality rate increased from 10% for a simple evolving score of 0 to 73% for a score of 4 (p < .01). Overall, 86% of those with a score < or =1 survived, whereas 85% of those with a score of > or =2 developed multiple organ failure and half of them died from sepsis.

CONCLUSIONS

The simple evolving DIC score calculated in the first 48 hrs from two readily available global coagulation markers appears to reflect the severity of the underlying disorder. It can be easily calculated at the bedside and provides useful prognostic information for the patient with severe sepsis.

Sepsis and coagulation

The host response to infection is a highly complex yet well-orchestrated process that involves an elaborate array of soluble mediators and cells. Normally, the host response prevails in containing and eliminating the pathogenic threat. When excessive or sustained, however, the host response may "turn on its bearer" and lead to organ dysfunction. Severe sepsis is invariably associated with activation of primary and secondary hemostasis. This article describes sepsis-associated changes in coagulation, discusses the putative role for these changes in pathogenesis of the sepsis syndrome, and outlines current diagnostic and therapeutic strategies.

Does Disseminated Intravascular Coagulation Lead to Multiple Organ Failure?

Microvascular dysfunction with its associated impaired regional oxygen transport and use is believed to be the final common pathway in the development of multiple organ failure. The precise mechanisms underlying this dysfunction, however, are uncertain. Activation of the coagulation system is a key feature in the pathogenesis of sepsis, but whether it is also the cause of multiple organ failure is unclear. This article discusses the evidence for and against a key role for disseminated intravascular coagulation in the pathogenesis of multiple organ failure.

Use of blood products in sepsis: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for the use of blood products in sepsis that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and to improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSION

In the absence of extenuating circumstances and following resolution of tissue hypoperfusion, red blood cell transfusion should be targeted to maintain hemoglobin at 7.0 g/dL or greater. Erythropoietin is not recommended as a specific treatment for sepsis-associated anemia. Fresh-frozen plasma should be given for documented deficiency of coagulation factors and in the presence of active bleeding or before surgical or invasive procedures. Antithrombin administration is not recommended. Specific platelet transfusion thresholds are based on the presence or absence of bleeding, significant risk for bleeding, plans for surgery or invasive procedures, and platelet count </=5,000/mm.

Analyse des facteurs de risque de mortalité chez les patients thrombopéniques en réanimation

OBJECTIVE

Determine predictive factors of intensive care mortality in thrombocytopenic patients.

STUDY DESIGN

Retrospective study.

PATIENTS AND METHODS

Data including the last 100 patients hospitalised in intensive care unit during period from March 2002 to January 2003 and having presented, at least one time, a platelet count <150 x 10(9)/l. Comparison between patients was realized according to the definitive issue (death or discharge from intensive care).

RESULTS

Incidence of thrombocytopenia was 27%. Mortality rate was 53%. Thrombocytopenia in admission was noted in 44% of the patients. IGS II score (OR = 1.05 and p = 0.014), sepsis (OR = 34.2 and p = 0.002) or hepatic dysfunction cases (OR = 42.5 and p = 0.026) were predictive factors of death in intensive care unit when thrombocytopenia occurred.

CONCLUSION

Our results concerning prognostic value of thrombocytopenia in intensive care unit are partly similar to those of literature with a surmortality associated to thrombocytopenia related to sepsis and hepatic dysfunction.

Percutaneous Tracheostomy Is Safe in Patients With Severe Thrombocytopenia

STUDY OBJECTIVES

Severe thrombocytopenia has been described as a contraindication for percutaneous tracheostomy (PT). The objective of this study was to assess the safety of PT in mechanically ventilated patients with severe thrombocytopenia (defined by a platelet count of < 50 x 10(9) cells/L).

DESIGN

Retrospective, single-center cohort study.

SETTING

Medical ICU of the University Hospital Hamburg-Eppendorf, Germany.

PATIENTS

Forty-two medical patients with acute respiratory failure and severe thrombocytopenia.

INTERVENTIONS

Bedside PT under bronchoscopic guidance using the Griggs guidewire forceps technique.

MEASUREMENTS AND MAIN RESULTS

The mean (+/- SD) intubation time prior to undergoing PT was 6.7 +/- 3.9 days (range, 1 to 20 days). The mean platelet count was 26.4 +/- 11.6 x 10(9) cells/L (range, 1 x 10(9) to 47 x 10(9) cells/L). The median transfusion of platelets before the procedure in 40 of the 42 patients was 6 +/- 2.5 U (range, 3 to 12 U). Twenty-two patients (52%) had an additional coagulopathy (activated partial thromboplastin time [APTT], > 40 s; international normalized ratio, > 1.5). PT was safely performed in all 42 patients. Only two (5%) patients developed major postprocedural bleeding complications that required suturing. Both of these patients had an elevated APTT due to heparin therapy.

CONCLUSIONS

When performed by experienced personnel, PT with bronchoscopic guidance has a low complication rate in patients with severe thrombocytopenia, provided that platelets are administered beforehand. However, in order to minimize bleeding complications heparin infusions should be temporarily interrupted during the procedure.

The puzzle of sepsis: fitting the pieces of the inflammatory response with treatment

Sepsis is a complex syndrome characterized by simultaneous activation of inflammation and coagulation in response to microbial insult. These events manifest as systemic inflammatory response syndrome (SIRS)/sepsis symptoms through release of proinflammatory cytokines, procoagulants, and adhesion molecules from immune cells and/or damaged endothelium.Conventional treatments have focused on source control, antimicrobials, vasopressors, and fluid resuscitation; however, a new treatment paradigm exists: that of treating the host response to infection with adjunct therapies including early goal directed therapy, drotrecogin alfa (activated), and immunonutrition. The multimechanistic drotrecogin alfa (activated) has been shown to reduce mortality in the severely septic patient when combined with traditional treatment. Therapies targeting improved oxygen and blood flow and reduction of apoptosis and free radicals are under investigation. Early sepsis diagnosis through detection of pro calcitonin, C reactive protein, sublingual CO2, and genetic factors may be beneficial. Ultimately, intervention timing may be the most important factor in reducing severe sepsis mortality.