Infection-associated platelet dysfunction of canine platelets detected in a flow chamber model.

BACKGROUND: In the present study, the influence of bacterial infection, lipopolysacharides (LPS) and hydroxyethyl starch (HES) on platelet function in a parallel plate flow chamber were measured. Experiments were performed with non-activated and protease-activating-receptor (PAR) 4 agonist activated platelets. Comparative measurements were in vivo capillary bleeding time, platelet function analyzer and impedance aggregometry. RESULTS: PAR 4 agonist did not increase platelet adhesion of platelets from dogs with bacterial inflammation in the flow chamber in contrast to platelets of healthy dogs. Except from impedance aggregometry with lower sensitivity and specificity, PFA did not detect platelet dysfunctions in dogs with infection. In vitro addition of LPS or HES significantly reduced platelet covered area after PAR-activation. CONCLUSIONS: The flow chamber detects platelet dysfunctions in dogs with inflammatory diseases. In vitro addition of LPS highlights the inhibiting effect of bacterial wall components on platelet function. Platelet dysfunction induced by infection could possibly also be diagnosed after treatment of sepsis with colloids has commenced. The flow chamber could be a useful tool to detect sepsis associated platelet dysfunction given that larger prospective trials confirm these findings from a proof of concept study.

Platelet functions in patients with meningococcal meningitis at the Kenyatta National Hospital, Nairobi.

OBJECTIVE: To determine platelet abnormalities in patients with menigococcal meningitis. DESIGN: Case control study. SUBJECTS: Fifty seven cases of mennigococcal meningitis based on a cerebrospinal fluid gram stain for gram negative diplococcus or positive culture were recruited. Fifty-seven controls matched for age and sex were also recruited. The following platelet functions tests were performed; platelet counts, platelet adhesiveness, platelet aggregation and clot retraction. RESULTS: Fifty seven patients (41 males and 16 females) with meningococcal meningitis were studied. Their mean age was 25.5 +/- 8.32 years with a range of 15 to 45 years. Five patients had purpura, four peripheral gangrene, eight conjunctival haemorrhages and one was in shock. There was a statistical significant difference in the platelet aggregation and clot retraction between the patients and controls at p-values of 0.0001 and 0.0002 respectively. There was no significant difference in the platelet count and adhesiveness between the patients and the controls at a p-value of 0.203 and 0.22 respectively. No association was found between the platelet functions and the clinical presentations. CONCLUSION: Patients with meningococcal meningitis have abnormalities in the platelet functions mainly in aggregation and adhesiveness.

The syndrome of pneumococcemia, disseminated intravascular coagulation and asplenia.

A 58-year-old man who survived an episode of fulminant pneumococcal septicemia with disseminated intravascular coagulation had undergone splenectomy 23 years previously. In the literature there are 25 reported cases of fulminant septicemia and disseminated intravascular coagulation associated with asplenia in adults (excluding cases in which corticosteroid or immunosuppressive therapy was given). The pneumococcus was responsible for all of these cases as well. The mortality in this series was more than 90%, and death occurred within 24 hours of presentation at hospital in almost 70% of the fatal cases and was associated with high-density bacteremia and adrenal hemorrhage. Gram-staining of the buffy coat of the peripheral blood or the exudate from purpuric skin lesions was carried out in only 6 of the 26 cases but yielded positive results in all but 1. It is concluded that a diagnosis of septicemia in asplenic adults can be established within a short time of presentation on the basis of statistical probability and the results of Gram-staining of the peripheral blood and exudate from the skin lesions. Prevention appears to be the cornerstone of management because of the variable interval from splenectomy to the onset of the syndrome and the high mortality.