To determine the frequency, location, size, and risk factors for silent cerebral infarctions (SCIs) on brain CT, we identified 629 patients without a history of previous stroke who were enrolled in a multicenter clinical trial of therapy for acute ischemic stroke. On the baseline CT, 143 patients (22.7%) had SCIs; 34.3% of the lesions were in the right hemisphere, 38.5% in the left hemisphere, and 27.3% were bilateral. The lesion size was < 1 cm in 65.7%, and the most common site was the basal ganglia (48.3%). Patients with SCI were compared with controls without SCI to determine the odds ratios (ORs) for each risk factor. On univariate analysis, race (black versus white) had an OR of 1.80 (95% confidence interval [CI], 1.14 to 2.85), male sex an OR of 1.68 (95% CI, 1.12 to 2.51), and congestive heart failure an OR of 1.88 (95% CI, 1.07 to 3.31). Significant risk factors on multivariate analysis include age (OR 1.03 per year, p = 0.0070), male sex (OR 1.78, p = 0.0094), and race (OR 2.43, p = 0.0004). After including interaction terms with age and hypertension and age, sex, and race, hypertension was also a significant risk factor.

SummaryTo study the normal development of blood coagulation factor activities in a growing fetus while avoiding the effects of labor and delivery, a chronic fetal lamb model was developed in which serial blood samples from 10 fetuses were studied during the third trimester of pregnancy and 24 hr after birth. Under operating room conditions with sterile technique, a polyethylene catheter to which heparin had been bound to both internal and external surfaces was inserted into the femoral artery of the fetus. The catheter was brought out through a skin pouch to the side of the ewe and enclosed in a zip lock bag. Blood samples were withdrawn from the catheter three times each week for measurement of coagulation factor activities. Levels of coagulation factor activities at birth in noncatheterized animals were not different from those found in catheterized animals except for factor IX activity which was 12% higher in the catheterized animals (0.02 t P < 0.05). The patterns of development for each of the coagulation factors were similar in all 10 animals studied. Fibrinogen, prothrombin, and factor VII show a decrease in activity early in the last trimester of pregnancy whereas other factors V, VIII, IX, X, XI, XII, and XI11 show a gradual increase in activity throughout the last trimester of pregnancy. Both factors VIII and IX show a significant increase in activity (23% factor VIII and 12% factor IX) associated with the process of delivery. The levels of coagulation factor activities at birth in the lamb relative to adult sheep normals are similar to those found in humans with the exception of factor XIII. Factor XIII is at normal levels in the newborn lamb and is reported to be at levels approximately 50% of the adult level in human infants. SpeculationThe development of a chronic fetal lamb preparation has allowed the construction of developmental patterns for coagulation factor activities throughout the last trimester of pregnancy. Further studies into the biology of the changes in coagulation factor activities observed and the influences of such stresses as hypoxemia and premature delivery should enhance our understanding of the bleeding neonate.

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Summary 5,9,16,18,25,29). Some authors report changes consistent withThe effects of severe hypoxemia on blood coagulation factor activities and other physiologic parameters were examined in ten near-term chronically catheterized fetal lambs (135-140 days gestation). Six lambs were subjected to a mean Po2 of 13.8 + 1.4 mmHg for 60 min. The other four served as controls. Before, during and after hypoxemia, the white blood cell count, hemoglobin, hematocrit, platelet count, pH, Pcoz, Poz, mean arterial pressure, heart rate, norepinephrine and epinephrine were measured. Measures of coagulation factor activities including platelet counts, partial thromboplastin times, prothrombin times and quantitation of plasma activities for factors I, 11, V, VII, VIII, IX, X, XI, XII, fibrin degradation products (FDP), antithrombin 111, fibrin monomer and ristocetin cofactor activity were also done. An increase in mean arterial Dressure from 48 + 2 mmHg to 56 + 2 " mmHg, and an increase in epinephrine from 22 f 9 pg/dl to 419 2 199 pg/dl, and norepinephrine from 431 f 98 pg/dl to 2408 + 868 pg/dl occurred in-thehypoxemic animals. here was also a slight decrease in the pH from 7.37 + 0.01 to 7.32 + 0.03 in the hypoxemic animals. The only significant change in blood coagulation factors during hypoxemia was a slight increase in fibrin monomer from 5.6 f 0.8 p g / d to 12.6 + 2.0 pg/ml. After the experiment, the animals were allowed to go to term and deliver spontaneously. Delivery occurred from 2-12 days after the experiment (mean 6 days). Blood coagulation factor activities I, 11, V, VI1, VIII, IX, X, XI, XII, antithrombin 111, fibrin monomer, and fibrin degradation products were measured after delivery in the hypoxemic and control animals. Except for factor XII, values obtained from ten previously catheterized control fetal lambs after spontaneous delivery did not differ from the current control animals after delivery.Values on postdelivery samples for the two control groups were therefore pooled for analysis. Factors VIII, and IX were found to show increased activity during the 2 wk after delivery in hypoxemic animals when compared with controls. In contrast, the values for factors 11, V, VII, X and fibrinogen showed lower activity in hypoxemic as compared to control animals during the early neonatal period. The study demonstrates that though there are no severe acute effects on blood coagulation during severe hypoxemia in the near-term fetus except perhaps transient low-grade disseminated intravascular coagulation, the episode of hypoxemia appears to alter the future development of blood coagulation factor activities during the early neonatal period. SpeculationHypoxemia in the near-term fetus delays the normal development of prothrombin, factors V, VII, X, and fibrinogen during the early neonatal period and accelerates the development of factors VIII and IX. The differences in factor responses may help explain the variable results reported in human infants. The results also suggest that both thrombotic and hemorrhagic tendencies...