Michaël Piagnerelli

Microvascular response to red blood cell transfusion in patients with severe sepsis.

Objectives:Microvascular alterations may play a role in the development of multiple organ failure in severe sepsis. The effects of red blood cell transfusions on microvascular perfusion are not well defined. We investigated the effects of red blood cell transfusion on sublingual microvascular perfusion in patients with sepsis. Design:Prospective, observational study. Setting:A 31-bed, medical-surgical intensive care unit of a university hospital. Patients:Thirty-five patients with severe sepsis requiring red blood cell transfusions. Interventions:Transfusion of one to two units of leukocyte-reduced red blood cells. Measurements and Main Results:The sublingual microcirculation was assessed with an Orthogonal Polarization Spectral device before and 1 hr after red blood cell transfusion. Red blood cell transfusions increased hemoglobin concentration from 7.1 (25th–75th percentile, 6.7–7.6) to 8.1 (7.5–8.6) g/dL (p < .01), mean arterial pressure from 75 (69–89) to 82 (75–90) mm Hg (p < .01), and oxygen delivery from 349 (278–392) to 391 (273–473) mL/min·M2 (p < .001). Microvascular perfusion was not significantly altered by transfusion, but there was considerable interindividual variation. The change in capillary perfusion after transfusion correlated with baseline capillary perfusion (Spearman-rho = −.49; p = .003). Capillary perfusion was significantly lower at baseline in patients who increased their capillary perfusion by >8% compared with those who did not (57 [52–64] vs. 75 [70–79]; p < .01), while hemodynamic and global oxygen transport variables were similar in the two groups. Red blood cell storage time had no influence on the microvascular response to red blood cell transfusion. Conclusions:The sublingual microcirculation is globally unaltered by red blood cell transfusion in septic patients; however, it can improve in patients with altered capillary perfusion at baseline.

Association between duration of storage of transfused red blood cells and morbidity and mortality in adult patients: myth or reality?

BACKGROUND: The duration of red blood cell (RBC) storage before transfusion may alter RBC function and, therefore, influence the incidence of complications.

Red blood cell rheology in sepsis

Changes in red blood cell (RBC) function can contribute to alterations in microcirculatory blood flow and cellular dysoxia in sepsis. Decreases in RBC and neutrophil deformability impair the passage of these cells through the microcirculation. While the role of leukocytes has been the focus of many studies in sepsis, the role of erythrocyte rheological alterations in this syndrome has only recently been investigated. RBC rheology can be influenced by many factors, including alterations in intracellular calcium and adenosine triphosphate (ATP) concentrations, the effects of nitric oxide, a decrease in some RBC membrane components such as sialic acid, and an increase in others such as 2,3 diphosphoglycerate. Other factors include interactions with white blood cells and their products (reactive oxygen species), or the effects of temperature variations. Understanding the mechanisms of altered RBC rheology in sepsis, and the effects on blood flow and oxygen transport, may lead to improved patient management and reductions in morbidity and mortality.

Disseminated Aspergillosis in Intensive Care Unit Patients: An Autopsy Study

Abstract Disseminated aspergillosis is an uncommon but frequently fatal disease in critically ill populations. With studies suggesting that the incidence of this disease is increasing, and with relatively few epidemiological data available in this population, we evaluated cases of disseminated aspergillosis identified at autopsy over a one-year period on a 31-bed mixed medico-surgical intensive care unit (ICU) of an academic university hospital. In 1999, there were 489 deaths out of 2984 ICU admissions, and 222 autopsies were performed. Post-mortem examination demonstrated disseminated aspergillosis involving non-contiguous organs in 6 (2.7%) autopsies and, of these, five patients (2.3% of total) had had chronic obstructive pulmonary disease (COPD) and had been treated with corticosteroids and mechanical ventilation for pulmonary infection. One patient also had granulocytopenia. In each patient, sputum and bronchoalveolar lavage (BAL) cultures had been positive for Aspergillus fumigatus after ICU admission but this was considered as colonization and the patients were given fluconazole for suspected candidal infection. In conclusion, COPD patients treated with corticosteroids and presenting with pulmonary infection should be considered at risk for disseminated aspergillosis. The rapidly fatal outcome after ICU admission suggests that colonization with Aspergillus can occur before ICU admission.

Transfusion in the intensive care unit

Objective:To summarize the incidences of anemia and blood transfusions in critically ill patients, assess their comparative risks and benefits, and briefly speculate on the possible effects of leukoreduction and blood storage on the need to reevaluate transfusion triggers. Design:A review of the current literature was performed. Results:Anemia is common in intensive care unit patients and is associated with increased mortality. Some 20–53% of intensive care unit patients will receive a blood transfusion during their stay, and these have also been associated with worse outcomes. Leukoreduction may limit some of the infectious and immunomodulatory risks associated with blood transfusion. Conclusions:Data on the risks and benefits of blood transfusion are conflicting, and with recent changes in blood transfusion practice, including the widespread introduction of leukoreduction, it is time to reevaluate our transfusion triggers.

Alterations of red blood cell shape and sialic acid membrane content in septic patients

ObjectiveTo investigate the relationship between red blood cell (RBC) shape and modifications of RBC membrane protein content in critically ill patients with or without sepsis compared with healthy control volunteers. DesignProspective, observational in vitro study. SettingUniversity-affiliated cell biology laboratory. SubjectsHuman erythrocytes from healthy volunteers and nonseptic and septic intensive care unit patients. InterventionsSialic acid membrane content was measured on isolated RBC membrane proteins by high-performance liquid chromatography. RBC shape, estimated by the spherical index (M2/M1) or by the moment and effect of osmolality on RBC shape, was studied by flow cytometry at 25°C. Glycophorin A content was measured with antiglycophorin antibodies in flow cytometry. Measurements and Main ResultsSialic acid content was lower in the septic than in the nonseptic patients (1.98 ± 0.79, 2.20 ± 0.39 &mgr;g/100 &mgr;g membrane protein, respectively; p = .01) and than in the volunteers (2.71 ± 1.00 &mgr;g/100 &mgr;g membrane protein; p < .001). No significant difference was found in glycophorin A content between septic and nonseptic patients. RBCs from septic patients had a more spherical shape in isotonic solution than those of healthy volunteers, as assessed by a computed spherical index (M2/M1 ratio: 1.68 ± 0.34 vs. 1.95 ± 0.32; p = .001). Only the RBCs of septic patients failed to change their shape in hypo-osmolar solution (M2/M1 ratio: 1.68 ± 0.34 in iso-osmolar, 1.56 ± 0.28 in hypo-osmolar solution; p = .17). There was a significant correlation between the RBC shape evaluated by the spherical index or by the moment of the cytometric histogram and the sialic acid membrane content in all critically ill patients (septic and nonseptic patients) (r2 = .16, p = .01 for the moment, and r2 = .17, p = .01 for the spherical index, respectively). ConclusionsRBCs of septic patients are characterized by a more spherical shape, a decreased capacity of sphericity in hypo-osmolar solution, and a reduction in the sialic acid content of the RBC membrane. These modifications in RBC shape and membrane may contribute to the RBC rheologic abnormalities frequently described in sepsis.

Early alterations of red blood cell rheology in critically ill patients

Objective: To investigate red blood cell rheology in a large intensive care unit population on admission, and to assess the possible influence of comorbidities on the rheology. Design: Prospective study. Setting: Medico-surgical intensive care unit with 31 beds. Subjects: All intensive care unit admissions during a 5-month period and 20 healthy volunteers. Interventions: Blood sampling. Measurements and Main Results: A total of 196 intensive care patients (160 without and 36 with sepsis) and 20 healthy volunteers were studied. Red blood cell rheology (deformability and aggregation) was assessed ex vivo using the laser-assisted optical rotational cell analyzer (LORCA; Mechatronics Instruments BV, AN Zwaag, Netherlands) within the first 24 hrs after intensive care unit admission. Red blood cell deformability was determined by the elongation index in relation to the shear stress (0.3 to 50 Pa) applied on the red blood cell membrane surface. Aggregation was assessed by the aggregation index. Septic patients were more likely to have anemia, coagulation abnormalities, and comorbidities than were nonseptic patients. Red blood cell deformability was significantly altered in septic compared to nonseptic patients and volunteers for the majority of shear stress rates studied. The aggregation index was greater in septic patients than in volunteers (67.9% [54.7–73.5] vs. 61.8% [58.2–68.4]; p < .05). Only sepsis and hematologic disease influenced the elongation index (both p < .01). Other comorbidities, like cancer, diabetes mellitus, cirrhosis, and terminal renal failure, had no effect on the elongation index. Aggregation index was related to the degree of organ failure (Sequential Organ Failure Assessment score), the red blood cell count, and fibrinogen concentrations. Conclusions: Early alterations of red blood cell rheology are common in intensive care unit patients, especially in those with sepsis. Comorbidities (other than hematologic diseases) do not significantly influence these abnormalities. These alterations could contribute to the microcirculatory alterations observed in critically ill patients.

Assessment of erythrocyte shape by flow cytometry techniques

Background: Red blood cell (RBC) rheology is altered in different diseases, including acute conditions such as patients in intensive care units (ICU) with sepsis or with an inflammatory reaction due to postoperative states or intracerebral haemorrhage, or chronic conditions such as diabetes mellitus or terminal renal failure. Several techniques are available to assess alterations in RBC rheology, especially deformability, but they are too cumbersome to be used on a large number of cells. Objective: To develop a new, rapid flow cytometry technique for easy assessment of RBC shape in patients. Methods: In flow cytometry, healthy human RBC shape shows a bimodal distribution related to the biconcave form. On this histogram, the second Pearson coefficient of dissymmetry (PCD) representing the asymmetry of this histogram and the spherical index (M2:M1) were calculated, both representing the spherical shape. This technique was used in healthy volunteers (n = 17) and in diseases characterised by abnormalities in RBC rheology, including terminal renal failure requiring haemodialysis (n = 28), diabetes mellitus (n = 18), sepsis (n = 19) and acute inflammatory states (postoperative, intracerebral haemorrhage, chronic obstructive pulmonary disease, epilepsy or severe drug intoxication; n = 21). Multivariate analysis was performed to determine the factors influencing RBC shape. Results: Measurement of RBC shape was highly reproducible. A good correlation was observed between the PCD and the spherical index, except in the critically ill patients without sepsis. RBCs were more spherical in patients with terminal renal failure (PCD −0.56 (0.14), p<0.05), diabetes mellitus (PCD −0.59 (0.23), p<0.05), sepsis (PCD −0.58 (0.22), p<0.05) or an acute inflammatory state (PCD −0.65 (0.29), p<0.05) than in healthy volunteers (PCD −0.89 (0.12)). The spherical index was also increased in all populations compared with healthy volunteers (terminal renal failure 2.30 (0.20); diabetes mellitus 2.27 (0.38); sepsis 2.28 (0.37); acute inflammatory state 2.35 (0.42) vs healthy volunteers 2.72 (0.47); all p<0.05). Multivariate analysis demonstrated that the underlying pathology (sepsis, acute inflammatory state, diabetes mellitus, terminal renal failure) was the principal cause of these RBC shape abnormalities. Conclusion: RBCs are characterised by an increased spherical shape in many disease states. The measure of the second PCD in flow cytometry is a new, easy method to investigate RBC shape in various diseases. This technique could facilitate the investigation of abnormalities of RBC rheology.

Rapid alterations in transferrin sialylation during sepsis

The inflammatory process is associated with alterations in iron metabolism. Transferrin, an acute-phase N-glycosylated glycoprotein, plays an important role in iron transport. Human serum transferrin contains two biantennary glycans, each consisting of 0 to 4 molecules of sialic acid (SA); its SA content is heterogeneous with high concentration of tetrasialotransferrin (4SA) and low amounts of disialo-, trisialo-, penta-, and hexasialotransferrin. The hepatic uptake of iron is greater for desialylated transferrin isoforms (disialotransferrin) than for the other forms. We hypothesized that serum levels of carbohydrate-deficient transferrin (CDT, disialotransferrin) may increase rapidly in septic patients. Blood samples were obtained from critically ill patients with (n = 15) and without (n = 14) documented sepsis and compared with healthy volunteers. The different forms of transferrin were studied by capillary zone electrophoresis; SA concentrations were measured by enzymatic colorimetric assay. There was a significant increase in the proportion of CDT in septic compared with nonseptic patients and volunteers (18.3% [1.3-30.5] vs. 0.7% [0.5-0.9]; P < 0.01 and 0.9% [0.5-1.1]; P < 0.05). Conversely, tri- and tetrasialotransferrin levels were lower in septic patients. Total and free SA concentrations were significantly higher in septic patients than in healthy volunteers. In a sheep model of septic shock secondary to peritonitis, serum free SA was already increased after 15 h. Sepsis is associated with decreased SA content on circulating transferrin and with an increase in blood free SA concentrations. In view of these rapid modifications and the long half-life of transferrin, the most likely explanation is degradation of transferrin by neuraminidase. Further studies including measurement of blood neuraminidase concentration and activity are needed to understand the process and exact role of SA decrease in septic patients.

Comparison of clinical and post-mortem findings in intensive care unit patients

The autopsy has long been regarded as an important tool for clinical confrontation, education and quality assurance. The aims of this study were to examine the correlation between the clinical diagnosis and autopsy findings in adult patients who died in an intensive care unit (ICU) and to identify the types of errors in diagnosis to improve quality of care. Autopsies from 289 patients who died in the ICU during a 2-year period were studied. Post-mortem examination revealed unexpected findings in 61 patients (21%) including malignancy, pulmonary embolism, aspergillosis, myocardial or mesenteric infarction and unsuspected bacterial, viral or fungal infection. These unexpected findings were classified as Goldman class I errors in 17 (6%), class II in 38 (13%) and class III in six (2%) cases. Although the incidence of unexpected findings with clinical significance was low, post-mortem examination remains a valuable source of pertinent information that may improve the management of ICU patients.