Thrombocytopenia in the critically ill patient

Relation between dynamic changes of platelet counts and 30-day mortality in severely burned patients

Thrombocytopenia is a common event in severely burned patients and associated with adverse outcome. The underlying relationship between the dynamic changes of platelet counts and mortality has not been well defined. We performed a 6-year retrospective chart of adult patients with a burn index of 50 or greater admitted to two burn centers and collected data on patient demographics, laboratory results, and patient outcomes. The mean daily increase in the platelet count (∆PC/∆t) from day 3 to day 10 was calculated, and 30-day mortality was determined. For the study, 141 survivors and 65 nonsurvivors were enrolled. The sequential changes in PCs presented a biphasic pattern after admission, with a slump to the nadir during the first 3 days and a subsequent recovery. With respect to 30-day mortality, compared with the AUC of APACHE-Ⅱ score (0.841), no significant difference was noted between ΔPC/ΔT and APACHE-Ⅱ score (p = 0.0648). The ΔPC/ΔT associated with the best discrimination between survivors and nonsurvivors was 20.57 × 10⁹/L due to the cutoff with optimal Youden index (0.453). By multiple logistic regression, ΔPC/ΔT ＜ 20.57 × 10⁹/L was one of the prognostic predictors of 30-day mortality. Furthermore, Kaplan-Meier estimates of hospital survival according to the size of ΔPC/ΔT revealed that a blunted increase with ΔPC/ΔT ＜ 20.57 × 10⁹/L was associated with increased 30-day mortality. A blunted daily increase in PCs, especially ΔPC/ΔT < 20.57 × 10⁹/L, is associated with increased 30-day mortality, which provides prognostic information for mortality risk assessment in severely burned patients.

Platelet counts and outcome in the pediatric intensive care unit

OBJECTIVES

Thrombocytopenia is commonly observed in critically ill patients. This study was undertaken to evaluate the variation in platelet counts and the risk factors associated with thrombocytopenia and mortality in pediatric intensive care patients. In addition, prognostic value of platelet counts for outcome in pediatric intensive care unit was studied.

STUDY DESIGN

Prospective, observational cohort analysis.

SETTING

8- bedded pediatric intensive care unit of a tertiary care teaching hospital.

PATIENTS

All consecutively admitted patients (n=138) staying in the pediatric intensive care unit (PICU) for at least 48h over a 7 months period were studied.

MEASUREMENTS AND MAIN RESULTS

Thrombocytopenia was defined as platelet counts <150.0/nL. Median 1(st) day Pediatric Risk of Mortality Score (PRISM) was 5 (range 0-30) and median ICU stay was 4 days (range 2-98 days). Twenty five percent patients had at least one episode of thrombocytopenia during the stay. Twenty percent of these patients had thrombocytopenia on admission and rest (80%) developed it during the PICU stay. Seventy one percent (19) of the patients developed thrombocytopenia by fourth day of admission. Patients with PICU acquired thrombocytopenia had statistically significant lower baseline, nadir and 4th day platelet counts and a significantly higher drop in platelet counts (56% vs. 6% P<0.001) as compared to non thrombocytopenic patients. PRISM score, long PICU stay, sepsis, coagulopathy, and creatinine levels were significantly associated with occurrence of thrombocytopenia. Patients with thrombocytopenia had higher probability of bleeding (34% vs. 15%, P=0.01). Higher platelet counts on admission were associated with significantly reduced risk of thrombocytopenia (P=0.00) Baseline, nadir and day-4 platelet counts, presence of thrombocytopenia on admission, sepsis, coagulopathy and a higher mean PRISM score on univariate analysis were significantly associated with mortality. Leucopenia or leucocytosis, thrombocytopenia and coagulopathy were found to significantly affect outcome. Drop in platelet counts was found to have slightly higher discriminative value for mortality prediction than PRISM on the ROC curve. The survivors had higher platelet counts throughout the PICU stay and after an initial fall in platelet counts in the PICU showed a significantly higher rise in the platelet counts in the following days than the non-survivors.

CONCLUSIONS

Thrombocytopenia is common in PICU. Patients requiring cardiopulmonary resuscitation or with circulatory shock, coagulopathy, sepsis and with more severe disease have higher risk of developing thrombocytopenia. Thrombocytopenic patients have a higher risk of bleeding. Drop in platelet counts >27% and thrombocytopenia were independently related to mortality. Serial measurements of platelet counts are better predictors of pediatric intensive care outcome than one-time values. Any drop in platelet counts even without thrombocytopenia needs an urgent and extensive evaluation.

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.

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.

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.

Frequency of heparin-induced thrombocytopenia in critical care patients

The diagnosis of heparin-induced thrombocytopenia (HIT) in critically ill patients is complicated by lack of information on the frequency of HIT relative to thrombocytopenia from other causes. In addition, results from HIT diagnostic tests have not been clearly evaluated for clinical utility. In this prospective study, we estimated the frequency of HIT and the predictive performance of the heparin-platelet factor 4 enzyme-linked immunosorbent assay (heparin-PF4 ELISA) in 748 consecutive, heparin-treated patients in a combined intensive and coronary care unit. The criteria for diagnosis were as follows: two or more consecutive platelet counts below 150 x 10(3)/mm3 or a 33% or greater decrease in platelet count 5 or more days after beginning heparin, or any time after starting heparin for patients exposed to the agent within the previous 8 weeks; and a positive 14C-serotonin release assay (SRA), the reference standard. Specificity and predictive values for the heparin-PF4 ELISA were estimated in patients who met the clinical criteria for HIT. Of 748 patients, 267 were exposed to heparin for a sufficient length of time to be considered to be at risk for HIT. Forty of these patients (15.0%, 95% confidence interval [CI] 10.7%-19.3%) met the clinical criteria for HIT. Serum samples were available for 32 of these patients, one of whom tested positive by the SRA, yielding a HIT frequency of 0.39% (95% CI 0.01-2.1%). The specificity of the heparin-PF4 ELISA among thrombocytopenic patients with negative SRA results was 71%, and the positive (PPV) and negative (NPV) predictive values of this test were estimated to be 10% and 100%, respectively. The point estimate of the frequency of HIT in critically ill patients was less than 1% in this cohort. The low PPV and high NPV of the heparin-PF4 ELISA suggest that it can be used to exclude HIT as a cause of thrombocytopenia in this patient population.

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.

Bioactive oxidized lipids in the plasma of cardiac surgical intensive care patients

Critical illness is associated with increased oxidative stress that may give rise to the formation of lipid hydroperoxides (LOOH) and various secondary degradation products such as fragmented phosphatidylcholine (FPC) and lipids related to the platelet-activating factor (PAF). Because some oxidized phospholipids are potent proinflammatory agents, we measured the concentration of LOOH, FPC, and PAF-like activity in blood plasma of 36 patients who had undergone cardiac surgery and developed postoperative complications associated with systemic inflammatory response syndrome (SIRS) or multiple organ failure (MOF). These patients were compared to two control groups, namely preoperative patients scheduled for cardiac surgery (n = 13), and postoperative patients without complications (n = 19). Postoperative patents had higher concentrations of LOOH and lower concentrations of FPC than preoperative patients (P < 0.01). However, SIRS and MOF had no significant effect on the concentration of oxidatively modified lipids. This is despite the fact that MOF patients showed evidence of increased lipid peroxidation (7-fold higher ratio of alpha-tocoquinone/alpha-tocopherol compared to control). LOOH correlated positively with the white blood cell count. Postoperative patients had 4-fold higher plasma activities of phospholipase A2 and this activity was further increased in patients with SIRS (P < 0.04). Phospholipase A2 activity correlated negatively with the concentration of FPC. The data suggest that oxidatively modified lipids do not accumulate in patients with SIRS and MOF, perhaps because enhanced peroxidation of lipids is offset by enhanced lipolytic activity.

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.

Thrombocytopenia and prognosis in intensive care

OBJECTIVE

To study the incidence and prognosis of thrombocytopenia in adult intensive care unit (ICU) patients.

DESIGN

Prospective observational cohort study.

SETTING

The medical ICU of a university hospital and the combined medical-surgical ICU of a regional hospital.

PATIENTS

All patients consecutively admitted during a 5-month period.

INTERVENTIONS

Patient surveillance and data collection.

MEASUREMENTS AND MAIN RESULTS

The primary outcome measure was ICU mortality. Data of 329 patients were analyzed. Overall ICU mortality rate was 19.5%. A total of 136 patients (41.3%) had at least one platelet count <150 x 10(9)/L. These patients had higher Multiple Organ Dysfunction Score (MODS), Simplified Acute Physiology Score (SAPS) II, and Acute Physiology and Chronic Health Evaluation (APACHE) II scores at admission, longer ICU stay (8 [4-16] days vs. 5 [2-9] days) (median [interquartile range]), and higher ICU mortality (crude odds ratio [OR], 5.0; 95% confidence interval [CI], 2.7-9.1) and hospital mortality than patients with daily platelet counts >150 x 10(9)/L (p < .0005 for all comparisons). Bleeding incidence rose from 4.1% in nonthrombocytopenic patients to 21.4% in patients with minimal platelet counts between 101 x 10(9)/L and 149 x 10(9)/L (p = .0002) and to 52.6% in patients with minimal platelet counts <100 x 10(9)/L (p < .0001). In all quartiles of admission APACHE II and SAPS II scores, a nadir platelet count <150 x 10(9)/L was related with a substantially poorer vital prognosis. Similarly, a drop in platelet count to < or =50% of admission was associated with higher death rates (OR, 6.0; 95% CI, 3.0-12.0; p < .0001). In a logistic regression analysis with ICU mortality as the dependent variable, the occurrence of thrombocytopenia had more explanatory power than admission variables, including APACHE II, SAPS II, and MODS scores (adjusted OR, 4.2; 95% CI, 1.8-10.2).

CONCLUSIONS

Thrombocytopenia is common in ICUs and constitutes a simple and readily available risk marker for mortality, independent of and complementary to established severity of disease indices. Both a low nadir platelet count and a large fall of platelet count predict a poor vital outcome in adult ICU patients.

Autoantibodies against platelet glycoproteins in critically ill patients with thrombocytopenia

PURPOSE

The aim of the study was to investigate immunologic causes of thrombocytopenia in critically ill patients, especially causes that were related to platelet-associated IgG antibodies.

SUBJECTS AND METHODS

All patients admitted to two intensive care units between May 1 and October 30, 1997, who developed thrombocytopenia (less than 100 x 10(9) platelets/L) were studied prospectively. We measured platelet-associated IgG with a radioimmunoassay using I(125)-labeled polyclonal antihuman IgG. Characterization of platelet-associated IgG was assessed with a monoclonal antibody immobilization of platelet antigen. Circulating immune complexes were also assayed.

RESULTS

Of the 61 patients with thrombocytopenia, elevated platelet-associated IgG was found in 18 (30%). Associated antiplatelet autoantibodies (glycoprotein IIb/IIIa) were detected in 4 patients, circulating autoantibodies (glycoprotein Ib/IX) were detected in sera from 2 patients, and circulating immune complexes were detected in 3 patients. The nature of the platelet-associated IgG could not be determined in 10 patients. Elevated platelet-associated IgG was associated with sepsis and previous cardiopulmonary bypass. Thrombocytopenic patients with elevated platelet-associated IgG had a lower nadir platelet count (58 +/- 27 x 10(9)/L vs 74 +/- 24 x 10(9)/L, P = 0.03).

CONCLUSION

Elevated platelet-associated IgG, some of which are platelet autoantibodies, is frequent in thrombocytopenic patients with sepsis or after cardiopulmonary bypass.

Thrombocytopenia in a surgical ICU

STUDY OBJECTIVES

To assess the incidence of thrombocytopenia in surgical ICU patients, the factors associated with thrombocytopenia, the outcome of thrombocytopenic patients, and the possible mechanisms involved.

DESIGN

Prospective study.

SETTING

An 8-bed surgical ICU in an 885-bed teaching hospital.

PATIENTS

147 consecutive patients admitted to the surgical ICU during a 6-month period.

MAIN OUTCOME MEASURES

Incidence of thrombocytopenia (defined by a platelet count < 100,000/mm3), risk factors for thrombocytopenia, or death in thrombocytopenic patients identified by a stepwise logistic regression analysis, as well as the mechanisms involved.

RESULTS

Thrombocytopenia occurred in 52 patients (35%) with a mortality rate of 38%, compared with a 20% mortality rate in nonthrombocytopenic patients (p = 0.02). Sepsis, episodes of bleeding or transfusions, and an acute physiology and chronic health evaluation (APACHE) II score of > 15 were the independent risk factors identified for thrombocytopenia. The correction of thrombocytopenia was a protective factor reducing the risk of mortality in thrombocytopenic patients. Disseminated intravascular coagulation was found in 40% of thrombocytopenic patients, elevated platelet-associated IgG in 33%, and hemophagocytic histiocytes in 67%. Combinations of two of these mechanisms were demonstrated in one quarter of thrombocytopenic patients.

CONCLUSIONS

Sepsis was the major independent risk factor identified. Thrombocytopenic patients had a higher ICU mortality due to the severity of overall clinical status. Bone marrow examination could be diagnostic when no obvious causes are demonstrated. Thrombocytopenia probably reflects the severity and course of an underlying pathologic condition, as its correction appears to be a good prognostic factor.

Potential risk factors associated with thrombocytopenia in a surgical intensive care unit

We conducted a retrospective chart review of 193 patients admitted during a 3-month period to determine the frequency of and potential risk factors associated with thrombocytopenia, and the association of acquired thrombocytopenia with length of stay in a surgical-trauma intensive care unit (SICU) and mortality. All records were reviewed beginning 24 hours after admission. Patients were followed for the duration of SICU stay or until death. Data collected and analyzed as potential risk factors for thrombocytopenia were age, gender, admitting diagnosis, classification (trauma, surgical, medical), APACHE II score, medical history, all scheduled drugs with start and stop dates, select laboratory values, arterial or central line placement, and complications. Thrombocytopenia occurred in 25 (13%) patients. These patients were more likely (p<0.05) than those without thrombocytopenia to have the following potential risk factors: presence of a central or arterial line (76% vs 46%, p<0.025), nonsurgical diagnosis (60% vs 37%, p<0.05), diagnosis of sepsis (p<0.001), and administration of phenytoin (p<0.01), piperacillin (p<0.005), imipenem-cilastatin (p<0.001), and vancomycin (p<0.005). A longer SICU stay (mean 21 vs 4.5 days, p<0.05) and increased mortality (16% vs 4%, p<0.05) were significantly associated with thrombocytopenia. Cefazolin administration was significantly associated with nonthrombocytopenia (p<0.05). Factors not associated with thrombocytopenia were age, gender, and administration of histamine2-receptor antagonists, heparin, enoxaparin, penicillins, ceftazidime, ceftriaxone, chloramphenicol, and amphotericin B. A central or arterial line was the only factor associated with the development of thrombocytopenia in a multiple linear regression analysis (p=0.0003, multiple r=0.2580). Thrombocytopenia is not a common occurrence in the SICU, but is associated with a longer SICU stay and increased mortality.

Thrombocytopenia in intensive care patients: a comprehensive analysis of risk factors in 314 patients

OBJECTIVE

To define the incidence and severity of thrombocytopenia in a mixed medical-surgical population of critically ill patients and to examine factors that may be related to the development of thrombocytopenia.

DESIGN

Retrospective chart review of 314 critically ill patients requiring at least 3 days of critical care.

SETTING

A 17-bed combined medical-surgical intensive care unit (ICU) in a 560-bed tertiary care community hospital.

PATIENTS

Medical and surgical patients admitted to the ICU.

INTERVENTIONS

All medical records over the duration of the ICU stay were reviewed. All scheduled medications, including dosage and start/stop dates, were recorded. All platelet counts, placement of pulmonary artery catheters, liver function test results, and admission serum creatinine concentrations were collected.

MEASUREMENT AND MAIN RESULTS

Thrombocytopenia (platelet count less than 200 x 10(9)/L) was observed frequently, but rarely reached a severe stage (7 patients). No single diagnostic category was significantly associated with thrombocytopenia alone, although the combination of sepsis syndrome/septic shock and respiratory failure was strongly correlated (p < 0.0001) with thrombocytopenia. Liver function abnormalities were correlated strongly with thrombocytopenia, and the majority of patients (5 of 7) with severe thrombocytopenia (less than 20 x 10(9)/L) were found to have concurrent severe alterations in liver function test results. Pulmonary artery catheter placement and heparin exposure were associated strongly with thrombocytopenia (p < 0.0001). Drug therapies that were correlated with thrombocytopenia included heparin and vancomycin (p < 0.05). Hemodynamic instability was correlated strongly with the presence and severity of thrombocytopenia. In a stepwise linear regression model, the admission platelet count accounted for the largest proportion of the variance (43%), followed by hemodynamic instability (8%) and the requirement for inotropic agents (2%).

CONCLUSIONS

Thrombocytopenia in the critically ill occurs frequently, rarely reaches severely depressed concentrations, and primarily represents a manifestation of disease processes initiated prior to admission. Hemodynamic instability and/or heparin exposure appear to be the strongest identifiable correlates with thrombocytopenia. Although these may cause infrequent isolated cases, other specific drug causes of thrombocytopenia are not responsible for the majority of cases of thrombocytopenia in the critically ill.