The New England journal of medicine
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We assessed the diagnostic value of determinations of serum levels of immunoreactive erythropoietin in 90 patients referred for the investigation of a raised packed red-cell volume (hematocrit) and possible erythrocytosis (a red-cell volume greater than that predicted by weight, body-surface area, or both). The mean values for erythropoietin were 16 mIU per milliliter (range, 8 to 22) in patients with polycythemia rubra vera (n = 24), 30 mIU per milliliter (range, 14 to 123) in patients with secondary erythrocytosis (n = 12), 27 mIU per milliliter (range, 13 to greater than 400) in patients with erythrocytosis of unknown origin (n = 19), and 25 mIU per milliliter (range, 18 to 35) in normal controls (n = 25). The values in the patients with polycythemia rubra vera were lower than those in the other three groups (P less than 0.01, P less than 0.05, and P less than 0.0001, respectively). ⋯ Among patients with erythrocytosis with an unknown cause, abnormally high serum erythropoietin levels were found in 3 of 19 subjects, and in 1 of these 3 the abnormality was intermittent. Thus, measurement of serum erythropoietin in a single sample may be misleading and may not have high discriminatory value in distinguishing between polycythemia rubra vera and secondary erythrocytosis. This assay is useful in identifying patients with secondary erythrocytosis who have inappropriate erythropoietin secretion.
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To examine the natural course of insulin action in Type I diabetes, we followed 15 patients prospectively for one year after the diagnosis of diabetes and also performed a cross-sectional study of 53 additional patients who had had diabetes for 2 to 32 years. Two weeks after diagnosis, the rate of glucose uptake during hyperinsulinemia, a measure of insulin action, was 32 percent lower in the patients with diabetes than in 30 matched normal subjects (P less than 0.01), but it rose to normal during the subsequent three months. At three months after diagnosis, 9 of 21 patients (43 percent) were in clinical remission and did not require insulin therapy. ⋯ In patients who had had diabetes for one year or more, insulin action was also reduced by an average of 40 percent (although there was considerable variation between patients), and it was inversely related to glycemic control and relative body weight. Thus, in patients with newly diagnosed Type I diabetes, a transient normalization of insulin action may occur after an initial reduction, along with a partial recovery of endogenous insulin secretion, and these events may contribute to the development of a clinical remission ("honeymoon" period). A majority of patients with diabetes of long duration are characterized by varying degrees of insulin resistance.
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We investigated the acid-base condition of arterial and mixed venous blood during cardiopulmonary resuscitation in 16 critically ill patients who had arterial and pulmonary arterial catheters in place at the time of cardiac arrest. During cardiopulmonary resuscitation, the arterial blood pH averaged 7.41, whereas the average mixed venous blood pH was 7.15 (P less than 0.001). The mean arterial partial pressure of carbon dioxide (PCO2) was 32 mm Hg, whereas the mixed venous PCO2 was 74 mm Hg (P less than 0.001). ⋯ However, mixed venous blood demonstrated striking decreases in pH (P less than 0.001) and increases in PCO2 (P less than 0.004). We conclude that mixed venous blood most accurately reflects the acid-base state during cardiopulmonary resuscitation, especially the rapid increase in PCO2. Arterial blood does not reflect the marked reduction in mixed venous (and therefore tissue) pH, and thus arterial blood gases may fail as appropriate guides for acid-base management in this emergency.