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Biomedical subjects

J R Humbert

Publications and source records attributed to J R Humbert.

At least 19 recordsLinked to original sources
PubMed2001

Management of preterm infants with intracardiac thrombi: use of thrombolytic agents.

Improvement in neonatal care has led to improvements in survival and patient outcome in preterm infants; however, this improved survival has been associated with the development of secondary complications, such as catheter-associated intravascular and intracardiac thrombus formation with a non-negligible morbidity and mortality. The sick preterm infant is at high risk of catheter-related thrombus formation because of the combination of a high prothrombotic activity, low levels of natural anticoagulants, and various imbalances in the fibrinolytic systems. Based on clinical experience in adults and children, and several neonatal case reports demonstrating the efficacy and tolerability of specific thrombolytic treatment, this approach should be recommended as a first choice treatment in the premature infant with intracardiac or intravascular thrombosis. The thrombolytic agents of choice are urokinase or tissue plasminogen activator (tPA); however, none of them have proven to be superior to the other in terms of efficacy or tolerability, either in adult patients or premature infants. In the past, it has been suggested that newborn infants may require higher doses of thrombolytic agents than adults for effective systemic thrombolysis; however, based on more recent in vitro studies, it seems unlikely that this is true. Nevertheless, systemic (high dose) fibrinolysis is of concern as premature neonates present an increased risk of cerebral haemorrhage during the first weeks of life; therefore, low dose treatment has been proposed with, if possible, direct infusion of the fibrinolytic agent into, or close to, the thrombus. This approach has proven to be efficient and well tolerated in several small case series of newborn and preterm infants. Recommended doses are 1000 to 3000 U/kg/h for urokinase or 0.01 to 0.05 mg/kg/h for tPA. A systemic proteolytic state will not be induced by this low dose; however, specific monitoring of fibrinogen plasma levels has to be recommended. Fibrinogen levels should remain above 100 mg/dL during low dose treatment. Lower levels of fibrinogen will indicate the presence of an unwanted systemic fibrinolytic state. After successful thrombolysis, a follow-up treatment, preferentially with low-molecular-weight heparin for neonates at adjusted doses, should be instituted for at least 6 weeks in the absence of any persisting thrombophilic factor. A longer course (3 to 6 months) of anticoagulation therapy is recommended when thrombophilic factors (i.e. hereditary thrombophilia or central venous catheter still in place) are present. Furthermore, it is recommended that any neonate with thrombosis should be evaluated for hereditary thrombophilia later in life.

Fibrinolytic Agents↗
PubMed1998

Bone mineral density of the lumbar spine and proximal femur is decreased in children with sickle cell anemia.

Bone mineral density (BMD) was evaluated in the proximal femora (femoral neck, Ward's triangle, and greater trochanter) and lumbar spines of 25 black children and young adults with sickle cell anemia using dual-photon absorptiometry. Compared with normal subjects from the general population, the patients with sickle cell anemia exhibited lower bone mineral density values in all scan regions (approximately 6% to 21% lower than expected). These differences in the lumbar spine were significant for both girls and boys. When compared with normal black subjects from the general population, the girls with sickle cell anemia exhibited significantly lower lumbar spine bone mineral density, and the boys with sickle cell anemia exhibited significantly lower bone mineral density in the femoral neck and Ward's triangle. No consistent or significant correlations were found between the bone mineral density data and the patients' hematologic indices.

Absorptiometry, Photon↗
PubMed1994

Correlation of transcranial Doppler ultrasonography with MRI and MRA in the evaluation of sickle cell disease patients with prior stroke.

We prospectively evaluated a group of patients with sickle cell disease and a clinical history of prior stroke, comparing transcranial Doppler sonography (TCD) to both magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) to determine its efficacy for the detection of flow abnormalities associated with prior cerebral infarction. Using MRI as the standard examination, there was 94% sensitivity and 30% specificity, and using MRA as the standard examination, there was 91% sensitivity and 22% specificity. We concur with other reports that the transcranial Doppler examination is a highly sensitive study. In our group of sickle cell disease patients with prior stroke, TCD reliably detected flow abnormalities that correlated to areas of prior cerebral infarction.

Adolescent↗
PubMed1994

Pseudomonas vesicularis causing bacteremia in a child with sickle cell anemia.

Pseudomonas vesicularis is a gram-negative rod infrequently found in environmental sources or clinical specimens. We report a case of bacteremia due to Pseudomonas vesicularis in a child with sickle cell anemia, fever, and pneumonia. This is the first published report of invasive P vesicularis in a child.

Anemia, Sickle Cell↗
PubMed1993

Treatment of acute idiopathic thrombocytopenic purpura with high-dose methylprednisolone and immunoglobulin.

In childhood idiopathic thrombocytopenic purpura (ITP), both intravenous high-dose steroids and immunoglobulin treatments have been demonstrated to raise platelet counts reliably and in most cases within 72 h, when used as separate therapeutic modalities. However, until now, the preferred emergency management of life-threatening complications in children with ITP has been immediate splenectomy. Since steroids and immunoglobulin create a partial splenic dysfunction, through different mechanisms, we investigated whether combined treatment with both drugs could produce a rapid platelet count increase comparable to that of splenectomy. Eleven patients, ages 4 months to 6 years, with a diagnosis of acute ITP were entered into this pilot study. Treatment consisted of intravenous high-dose methylprednisolone (20 mg/kg in 30 min) followed by intravenous gamma globulin (Gamimune-N, 1 g/kg over 5 h). The combined therapy resulted in rapid increments in the platelet counts of all patients within the 24-hour period. At 12-h, in particular, 9/11 patients had platelet counts of 30 x 10(9)l or more. We conclude that this combined therapy provides a prompt rise in platelet counts to a safe and hemostatic level and may offer a viable alternative for emergency splenectomy and its associated morbidity/mortality in many cases of childhood ITP.

Child, Preschool↗
PubMed1993

Reversible splenic hypofunction in hypertransfused children with homozygous sickle cell disease.

Functional hyposplenism, as documented by technetium 99 metastable sulfur colloid spleen scan and increased pocked erythrocyte count (also known as a pit count), is well described in children under 2 years of age with homozygous sickle cell anemia. We evaluated the clinical course and splenic function of 16 patients with sickle cell anemia (ages 3 to 20 years) on a hypertransfusion program for more than 6 months following a cerebrovascular accident. Patients were followed with simultaneous spleen scan and pitted erythrocyte count using direct interference contrast microscopy. Pit counts were taken prior to each transfusion and hemoglobin S level maintained at less than 20%. With the exception of two patients, splenic function was recovered only in those patients who were younger than 10 years of age at the time transfusion was initiated. There were no serious bacterial infections or other complications of sickle cell anemia documented in the hypertransfused group. Based on our results and the literature review, we conclude that some patients with sickle cell anemia receiving intensive hypertransfusion therapy for a cerebrovascular accident recover a normal splenic phagocytic function. Age and level at which the hemoglobin S is maintained are important factors in reestablishing splenic phagocytic function.

Adolescent↗
PubMed1991

Spleen function in children with sickle B+ thalassemia.

Splenic function in patients with sickle B+ (SB+) thalassemia has been poorly documented. We evaluated the clinical course and splenic function in 12 children with SB+ thalassemia with simultaneous technetium sulfur colloid spleen scans and determination of pitted erythrocytes by direct interference contrast microscopy (DICM). All patients displayed normal uptake of radiocolloid. Mean percentage of pitted erythrocytes was 2.2% compared to 0.06% in 10 normal eusplenic controls and 13.8% in 10 sickle cell patients. In this group of children, who were carefully monitored for 136 patient years, there was no episode of bacteremia/sepsis, and a low prevalence of vaso-occlusive episodes. The slight increase in percentage of pitted erythrocytes of SB+ thalassemia patients does not seem to herald any clinically relevant loss of splenic function. SB+ thalassemia children younger than 10 years of age who do not seem to present a higher risk of invasive bacterial infections than eusplenic children, should receive conservative treatment for isolated febrile episodes and should not be submitted to prophylactic penicillin.

Adolescent↗
PubMed1990

Gova/b alloantigen system on human platelets.

In this report we describe a platelet alloantigen system that is carried on a novel platelet protein of 175 Kd. Antisera against the two alleles (Gova/Govb) were found in two patients who had received large numbers of platelet transfusions. The anti-Gov alloantibodies could not be detected using a whole platelet solid phase enzyme immunoassay, or by a platelet glycoprotein capture enzyme immunoassay using monoclonal antibodies against glycoproteins Ib/IX, Ia/IIa, and IIb/IIIa. Using radioimmunoprecipitation techniques, a protein was precipitated that migrated at 175 Kd (reduced). Under nonreduced conditions, a 150-Kd protein was detected with a minor component at 175Kd. The detection of the alloantigens was not activation-dependent. Using immunodepletion studies, we demonstrated that each alloantiserum recognized an epitope on a discrete population of the 175-Kd platelet protein. Family studies demonstrated that the alloantigens designated as Gova and Govb were inherited in an autosomal codominant fashion. The phenotypic frequencies were Gova/Gova, 26%; Gova/Govb, 55%; Govb/Govb, 19%; giving gene frequencies of 0.532 and 0.468 for Gova and Govb, respectively (n = 33).

Alleles↗
PubMed1990

Cerebral blood flow mapping using stable xenon-enhanced CT in sickle cell cerebrovascular disease.

The cerebral blood flow (CBF) of 25 patients with sickle cell cerebrovascular disease (SCCVD) was examined using a Xenon-CT flow mapping method. Brain CT and MR findings were correlated with those of the Xenon-CT flow studies. CBF defects on Xenon-CT correlated reasonably well with the areas of cortical infarctions on the MR images, but in 27% of the cases, flow defects were slightly larger than the areas of infarctions on the MR images. In deep watershed or basal ganglia infarctions, abnormal CBF was noted about the cerebral cortex near infarctions in 72% of the patients, regardless of infarction sizes on the MR images. However, decreased CBF was recognized in 4 of the 9 children whose MR images were virtually normal. Thus, the extent of flow depletion cannot be predicted accurately by MR imaging alone. Xenon-CT flow mapping proved a safe and reliable procedure for evaluation of the CBF of patients with SCCVD. Although this study is preliminary, it may have a potential in selecting patients for hypertransfusion therapy, as a noninvasive test and for following children with SCCVD during their therapy. Careful correlation of results of CBF with those of MR imaging or of CT is important for objective interpretations of flow mapping images.

Adolescent↗
PubMed1990

Neutrophil dysfunctions in sickle cell disease.

The abnormal susceptibility towards certain infections in SCD patients has a partial explanation in the well described functional defects of the spleen and of the alternative complement pathway; such defects probably account for the etiology of fulminant, often fatal, childhood infections with encapsulated organisms (Streptococcus pneumoniae, Haemophilus influenzae). On the other hand, the frequent systemic infections with enteric organisms in SCD patients, particularly of the salmonella species, and also with Staphylococcus aureus, are more difficult to explain. We therefore reviewed the potential contribution of neutrophil (PMN) dysfunctions to the increased infective tendency of SCD patients and included some previously unpublished data from our laboratory. While notable discrepancies still exist--and need further clarification--a tentative working hypothesis can be extracted from the available data: dysfunctions of neutrophils affect their locomotion (as reflected by decreased chemotaxis and in vivo migration), their phagocytic processes and their bactericidal performance. The latter concerns the ineffective killing of Staphylococcus aureus, Candida albicans, and Streptococcus pneumoniae. Dysfunctional bactericidal activity, in turn, apparently relates to a poor or at times non-existent PMN oxidative activity, which prevents the prompt disposal of microorganisms. Under certain circumstances salmonella species seem to further paralyze the oxidative machinery of PMNs in SCD. Serum from some patients contains a poorly defined inhibitor, or lacks an enhancing factor, and such serum abnormalities aggravate the existing defects just described. Interestingly recent findings suggest that dysfunctional PMNs may originate from the mandatory demargination of leukocytes secondary to the functional asplenia of SCD; a predominance of non-rosetting (EA-) PMNs among such leukocytes could produce the operational explanation for an exaggerated representation of dysfunctional PMNs in SCD patients with leukocytis.

Anemia, Sickle Cell↗
PubMed1990

Tumor necrosis factor primes neutrophils by shortening the lag period of the respiratory burst.

Pretreatment of neutrophils (PMNs) with low-dose tumor necrosis factor (TNF) enhances their capacity to produce oxidant radicals after stimulation with a variety of agents ('priming'). We used a continuous cytochrome C assay to investigate the superoxide production by human PMNs primed with TNF and subsequently stimulated with phorbol myristate acetate (PMA). There was no difference in the maximum rate of superoxide production by primed and unprimed PMNs stimulated with either high (2 x 10(-6) M) or low levels of PMA (2 x 10(-8) M). Following stimulation with high levels of PMA, primed PMNs demonstrated a significantly shorter lag period than unprimed cells (103.3 +/- 14.4 vs. 142.1 +/- 21.7 seconds) and larger amounts of superoxide generated in the intervals between 100 seconds (3.1 +/- 0.5 vs. 1.7 +/- 0.3 nmol/10(6) PMNs) and 300 seconds (14.9 +/- 1.2 vs. 12.2 +/- 1.1). Primed cells stimulated with low levels of PMA (2 x 10(-8) M) displayed a significantly shorter lag period (1225.8 +/- 96.8 vs. 1573.8 +/- 74.3 seconds) and a greater production of superoxide between 1300 seconds (5.4 +/- 0.9 vs. 3.0 +/- 0.4 nmol/10(6) PMNs) and 1900 seconds (25.7 +/- 4.3 vs. 14.9 +/- 2.4) than unprimed cells. These results indicate that priming of PMNs with TNF increases superoxide production during the early phase of the respiratory burst through a shortening of the post-stimulation lag period.

Adult↗
PubMed1990

Successful treatment of disseminated Fusarium infection in an immunocompromised child.

We report the first know case of disseminated fungal infection due to Fusarium proliferatum in a bone marrow transplant recipient to our knowledge. Fusarium was cultured from the blood, a paranasal sinus, and necrotic skin lesions. The isolate was sensitive to amphotericin B and on further sensitivity testing, synergy was demonstrated using rifampin in combination with amphotericin B. The patient had this infection while she was receiving alternate-day amphotericin, rifampin, and 5-flucytosine (5-FC) therapy. The infection was documented within 48 h of discontinuing daily granulocyte transfusions, which she had received for 3 weeks. The 5-FC was discontinued when sensitivities showed the organism resistant. After 6 weeks of treatment she showed complete remission of the infection, although neutrophil counts remained below 0.25 X 10(9)/L. From this case and from a review of the literature, it appears that synergic antifungal agents combined with leukocyte transfusions may be beneficial in the successful treatment of fusariosis in the compromised host.

Amphotericin B↗
PubMed1984

Severe homozygous protein C deficiency.

An infant with recurrent purpura fulminans in the first year of life was found to have severe homozygous deficiency of protein C (less than 1% of normal levels). The episodes of purpura fulminans were controlled by infusions of fresh frozen plasma containing protein C. The requirement of frequent plasma infusions, however, eventually resulted in several complications secondary to hyperproteinemia. Factor IX concentrates rich in protein C were then given to maintain adequate levels of the factor while minimizing the amount of extraneous proteins. The patient has remained asymptomatic and free of complications for greater than 10 months while receiving these concentrates every 48 hours.

Blood Coagulation Factors↗