Monitoring of the neonate undergoing MR imaging: technical considerations. Work in progress

Instrument monitoring of vital signs in neonates undergoing magnetic resonance (MR) imaging can be difficult because of the unique environmental restrictions imposed by the imager. The authors present their experience with monitoring more than 50 newborn infants and discuss the interaction of monitoring devices with the MR imager. Several MR-compatible monitors allow continuous evaluation of body temperature, heart rate, blood pressure, and auscultation of heart sounds and respiration in mechanically ventilated infants. Signal-to-noise (S/N) ratio measurements taken during imaging of the head of an infant with these monitors in place did not differ appreciably from the ratio obtained during imaging without monitors. Tip angles should be optimized to account for widely varying head size among neonates, since adverse monitoring effects are significantly compounded by improper tip angle adjustment.     

Abnormalities of the neonatal brain: MR imaging. Part I. Intracranial hemorrhage

The authors prospectively evaluated 82 neonates, ranging in gestational age from 29 to 44 weeks postconception, with magnetic resonance (MR) imaging at 0.6 T. Twenty-two cases of hemorrhage in 15 infants were identified. Ultrasound (US) and computed tomography (CT) were superior to MR in the first few days after parenchymal hemorrhage, since at this time lesions were apparent on only T2-weighted images. After the first 3 days, MR was the single best modality because (a) hemorrhage on CT became imperceptible in the 2d week, whereas the high signal of hemorrhage on MR persisted for 2-11 weeks; (b) MR permitted rough dating of hemorrhage according to changes in signal intensity; and (c) MR was superior in identifying subdural or epidural hemorrhage. Because of the nonspecificity and restricted field of view of US and the inability of CT to depict hemorrhage after 7-10 days, the authors conclude that MR significantly improves the detection of intracranial hemorrhage in neonates.     

Mathematical modeling of platelet survival with implications for optimal transfusion practice in the chronically platelet transfusion- dependent patient

BACKGROUND: It is known that in vivo platelet survival varies as the platelet count changes. Previous attempts at curve fitting fail to predict the decreased platelet survival in thrombocythemia. Therefore, mathematical relations that more closely approximate platelet survival were derived and used in models of platelet transfusion practice. STUDY DESIGN AND METHODS: A differential equation for platelet loss was derived that included a constant (constant homeostatic loss), a first- order term (senescent loss), and a second-order term (one proportional to the square of the platelet concentration and whose contribution is expected to be significant only at higher platelet concentrations). Data derived from this model was compared to platelet survival data in normal, thrombocytopenic, and thrombocythemic patients and to the platelet decay after high-dose chemotherapy. To provide further validation of this model, predicted and actual platelet requirements were calculated or obtained (chart review) in bone marrow patients with uncomplicated thrombocytopenia after ablation and at two platelet- transfusion thresholds (20 and 10 × 10(9)/L). RESULTS: The equations accurately modeled normal, thrombocytopenic, and thrombocythemic platelet survival. Chart review demonstrated a 12.5 percent reduction in platelet transfusion requirements when the transfusion threshold was reduced from 20 to 10 × 10(9) per L. The model predicted a reduction of 14.0 percent. For 100 days of uncomplicated thrombocytopenia and a transfusion threshold of 10 × 10(9) per L, transfusion of 3 units of platelet concentrates compared to a 6-unit pool of platelet concentrates, resulted in a 22-percent savings of platelet units. CONCLUSION: Platelet survival as a function of platelet concentration can be modeled by use of a differential equation. This model challenges current dogma regarding platelet destruction and predicts decreased platelet survival in thrombocythemic patients. The model illustrates that large doses of platelets would result in greater time between transfusions, however, more units of platelets are used. Consideration should be given to the more frequent use of smaller doses of platelets in patients who chronically require platelet transfusion support.     

Gene and other biological therapies for vascular diseases

Summary— Gene transfer and antisense therapy offer novel approaches to the study and treatment of vascular diseases. The localized nature of vascular diseases like restenosis has made the application of genetic material an attractive therapeutic option. Viral and nonviral vectors have been developed to facilitate the entry of foreign DNA or RNA into cells. Vector improvement and production, demonstration of vector safety and demonstration of therapeutic efficacy are among the main present challenges. Various strategies have already been shown to be successful in preventing restenosis in animal models and include: the transfer of the herpes simplex virus thymidine kinase associated with ganciclovir; transfection of the cell cycle regulatory genes encoding for the active form of retinoblastoma gene product (Rb) or the cyclin-dependant kinase inhibitor p21, and antisense therapy. Therapeutic angiogenesis using gene transfer is a new strategy for the treatment of severe limb ischemia. Transfection of DNA encoding for the vascular endothelial growth factor has resulted in increasing collateral flow in animal models of peripheral ischemia. This approach is currently being investigated in a clinical trial in patients with distal ischemia. Other potential targets for genetic treatment in cardiovascular diseases include thrombosis, extracellular matrix synthesis and lipid metabolism.     

Plateletpheresis in the management of thrombocytosis

Acute thrombotic and hemorrhagic manifestations of thrombocytosis associated with myeloproliferative disorders may be life threatening. Conventional therapy with radioisotopes and/or cytotoxic drugs may require weeks for effective control of platelet counts. In five patients, plateletpheresis by discontinuous-flow (Haemonetics) or continuous-flow (Aminco Celltrifuge) centrifugation was used as a means of reducing platelet counts acutely. With each procedure, approximately 2-9 X 10(12) platelets were removed, resulting in decrements in platelet counts and relief of symptoms. Plateletpheresis is a useful and safe acute means of controlling platelet counts in myeloproliferative disorders.     

A Chromatographic Study on the Glycosides of Aerva lanata L.

AIM:In order to identify the HPTLC profile(bio-marker),at species level,for the identification and confirmation of crude drugs,HPTLC separation was initiated on different parts of Aerva lanata L.from South India.METHODS:Preliminary phyto-chemical screening was done by the method of Harborne.HPTLC studies were carried out following Harborne and Wagner et al method.The Ethyl acetate-ethanol-water(8:2:1.2)was employed as mobile phase for glycosides.RESULTS:The methanolic extract of stem,leaves,root,flowers and...     

Abnormalities of the neonatal brain: MR imaging. Part II. Hypoxic- ischemic brain injury

Eighty-five infants, 82 of whom were 29-44 weeks postconceptional age, were imaged with a 0.6-T magnet. Eight infants had cerebral infarction. In premature neonates with very water, low-intensity white matter on T1-weighted images, ultrasound was better than both computed tomography and magnetic resonance (MR) imaging in depicting parenchymal changes of infarction or edema. However, after 37 weeks gestation, MR imaging was superior. Cerebral atrophy, present in seven infants, was consistent with subarachnoid space widths of 7 mm or more, or subarachnoid space widths of 5-6 mm with ventricular/brain ratios of 0.36 or greater. Delayed myelination was seen in a total of 18 infants with histories of hypoxic-ischemic insult. MR imaging shows promise in the neonatal period. It facilitates recognition of infarcts in full-term infants and may be used to predict abnormal neurologic outcome in infants who have initial delayed myelination.