Increased neonatal platelet deposition on subendothelium under flow conditions: the role of plasma von Willebrand factor.

In vitro platelet function of umbilical cord blood and neonatal peripheral vein blood from full-term newborns was compared with that of adults. Citrated whole blood was subjected to shear stress (1300 s(-1)) on subendothelial extracellular matrix (ECM)-coated wells in a cone and plate(let) analyzer. Adhered platelets on the ECM were quantitated by image analyzer. Both umbilical cord and neonatal peripheral blood platelets demonstrated more extensive adhesion than adult platelets, and similar aggregate formation on ECM. The ability of neonatal platelets to form aggregates on ECM was confirmed by scanning electron microscopy. Similar activation of neonatal and adult platelets after subjection to shear stress, in the suspension phase, was established by flow cytometry, which showed an increase in fibrinogen binding and a decrease in glycoprotein Ib expression on platelet membrane. The difference in adhesion rates between neonatal and adult platelets was preserved even when the hematocrit level of the neonatal blood was adjusted to that of adults. Reconstitution of neonatal or adult platelet-rich plasma with autologous or heterologous red packed cells yielded no change in adhesion and aggregation. When von Willebrand factor-covered plates were used to prevent deposition of plasma von Willebrand factor on the surface, no difference in platelet adhesion was seen between neonatal and adult blood. In conventional aggregometry assay, the response to ristocetin of washed platelets of either neonatal or adult source was higher on addition of plasma from neonates than from adults. Our data suggest that the extensive neonatal platelet deposition on ECM is mediated by plasma von Willebrand factor, which is known to be more multimerized and, therefore, more active in neonates than in adults. This mechanism may provide balanced primary hemostasis in neonates despite the platelet hyporeactivity to agonists without application of shear stress.

Aurioscope earpieces--a potential vector of infection?

OBJECTIVES: to determine whether non disposable aurioscope earpieces used in community paediatric clinics harbored pathogenic micro-organisms, and to explore primary pediatrician perception of the possibility of cross infection from contaminated aurioscope earpieces and of how their aurioscope earpieced are cleaned. DESIGN: randomized survey. SETTING: four community pediatric clinics. MATERIALS: 42 pediatricians' aurioscope earpieces were cultured on blood agar and mannitol-salt-agar plates by two methods: (1) The earpieces were rolled for 5 s onto blood agar plates (TSA + 5% sheep blood, and a mannitol-salt-agar-plate). (2) The entire surface of the earpiece was swabbed with a sterile cotton tipped applicator moistened in sterile saline solution and was inoculated immediately onto a blood agar plate, and a mannitol-salt-agar-plate. The plates were incubated at 37 degrees C for 48 h and examined for colony growth at 24 and 48 h of incubation. Culture results were recorded as mean numbers of colony-forming units (CFUs). RESULTS: 36 from 42 (86%) of the aurioscope earpieces were colonized by micro-organisms. Heavily contaminated earpieces were found in six (14%). Staphylococci were isolated from 27 (64%) of the earpieces: 19 (45%) being Staphylococci aureus coagulase positive, 4 (9%) were methicillin resistant S. aureus (MRSA). CONCLUSIONS: Non disposable earpieces can harbor potentially pathogenic bacteria including MRSA. The increased trend for children with immunodeficiency to be managed in an ambulatory setting, often by physicians who also work in hospital, might be a risk of spreading potentially serious infections to such patients. Non disposable earpieces should be regularly disinfected to minimize the spread of infection.

Plain radiography for diagnosis of gastrointestinal perforation in immune-compromised children--is it enough?

Gastrointestinal perforation is a surgical emergency in the pediatric patient and any delay in diagnosis might be hazardous. In immunocompromised children, the clinical signs of perforation may be blunted. We describe a child with acute lymphoblastic leukemia (ALL) and a perforated appendix and ileum in whom computerized tomography (CT) revealed extraluminal air that was not initially identified on plain abdominal film. Our case demonstrates the importance of early abdominal CT and ultrasound examination in detecting these potentially lethal complications.