Robert M. Rosa

Treatment of severe systemic lupus erythematosus with high-dose chemotherapy and haemopoietic stem-cell transplantation: a phase I study

BACKGROUND Patients with systemic lupus erythematosus (SLE) who experience persistent multiorgan dysfunction, despite standard doses of intravenous cyclophosphamide, represent a subset of patients at high risk of early death. We investigated the safety and efficacy of immune suppression and autologous haemopoietic stem-cell infusion to treat such patients. METHODS From 1996, we selected patients with persistent SLE despite use of cyclophosphamide. Patients underwent dose-intense immune suppression and autologous haemopoietic stem-cell (CD34) infusion. Peripheral blood lymphocytes were analysed by flow cytometry, ELISA, and T-cell-receptor spectratyping before and after transplantation. We mobilised autologous haemopoietic stem cells with 2.0 g/m2 cyclophosphamide and 10 microg/kg granulocyte colony stimulating factor daily, enriched with CD34-positive selection, and reinfused after immunosuppression with 200 mg/kg cyclophosphamide, 1 g methylprednisolone, and 90 mg/kg equine antithymocyte globulin. RESULTS Nine patients underwent stem-cell mobilisation but two were excluded before transplantation because of infection. The remaining seven received high-dose chemotherapy and stem-cell infusion. Median time to an absolute neutrophil count higher than 0.5x10(9)/L and nontransfused platelet count higher than 20x10(9)/L was 9 days (range 8-11) and 11 days (10-13), respectively. At a median follow-up of 25 months (12-40), all patients were free from signs of active lupus. Renal, cardiac, pulmonary, and serological markers, and T cell phenotype and repertoire had normalised. INTERPRETATION Patients remained free from active lupus and improved continuously after transplantation, with no immunosuppressive medication or small residual doses of prednisone. T-cell repertoire diversity and responsiveness was restored. Durability of remission remains to be established.

Adrenergic Modulation of Extrarenal Potassium Disposal

We studied the role of catecholamines in the regulation of potassium homeostasis in nine healthy subjects given intravenous potassium chloride (0.5 meq per kilogram of body weight) in the presence and absence of propranolol. Potassium infusion elevated serum potassium 0.6 +/- 0.09 meq per liter (mean +/-S.E.M.). Addition of propranolol augmented the rise (0.9 +/- 0.05 meq per liter) and prolonged the elevation in serum potassium without decreasing urinary potassium excretion. In a separate study, the same potassium load was administered with a concomitant infusion of epinephrine in five subjects. Epinephrine markedly blunted the increment in serum potassium (0.1 +/- 0.06 meq per liter) while reducing renal potassium excretion. Plasma aldosterone was not altered by the experimental procedures. Serum insulin fell minimally in the presence of propranolol but was unaffected by epinephrine. beta-Adrenergic blockade impairs and epinephrine enhances extrarenal disposal of an acute potassium load. These findings suggest that in patients with impaired potassium disposal, the risk of hyperkalemia may be increased when sympathetic blockade is induced.

Effect of experimental potassium deficiency on glucose and insulin metabolism

Disturbances in glucose and insulin metabolism frequently accompany a variety of clinical states associated with potassium deficiency. The exact role of the potassium deficit and the mechanism of its effect are in doubt. The glucose-clamp technique was therefore employed to study glucose and insulin metabolism in 7 normal young male subjects before and after induction of potassium depletion. The clamp technique places the blood glucose concentration under the investigators control. Under the conditions of steady state hyperglycemia (125 mg/dl above basal for 2 hr) it provides quantification of (1) pancreatic beta cell sensitivity to glucose (plasma insulin response), (2) glucose tolerance (glucose metabolized), and (3) tissue sensitivity to insulin (glucose metabolized/insulin response). Potassium deficiency was induced during a 7–8 day period of a weight-maintaining diet containing 40 meq potassium and at least 150 g carbohydrate, along with the administration of 60 g Na polystyrene sulfonate daily. Paired analysis showed a significant decline in the amount of glucose metabolized from pre- to postdepletion (−27.4 ± 4.5%, p < 0.01). This decline in carbohydrate tolerance was associated with a significant decrease in plasma insulin response to sustained hyperglycemia (−26% ± 6.9%, p < 0.02). Potassium depletion had no effect on tissue sensitivity to insulin (+1.7 ± 7.8%). The degree of potassium depletion as estimated by change in total body 40K ranged from 1.0% to 8.4% and correlated with the decrease in insulin response (r = 0.78, p < 0.05). This study demonstrates that potassium depletion causes glucose intolerance, which is associated with impaired insulin secretion.

Catecholamine Modulation of Rapid Potassium Shifts during Exercise

Plasma potassium rises during muscular exercise and falls rapidly when exercise is stopped. Since the sympathoadrenal system is stimulated with exertion and both alpha- and beta-adrenergic agonists affect internal potassium homeostasis, we studied the influence of catecholamines on potassium shifts during and after exercise. Six healthy subjects were given maximal exercise stress tests under three conditions: with no medication (control), during beta-blockade with propranolol, and during alpha-blockade with phentolamine. Compared with a peak rise in plasma potassium of 1.23 +/- 0.27 mmol per liter (mean +/- S.E.M.) during the control study, propranolol caused a rise of 1.89 +/- 0.35 (P less than 0.01) and a sustained elevation during recovery. Phentolamine diminished the rise of potassium (0.70 +/- 0.21 mmol per liter; P less than 0.01) and lowered the potassium level throughout recovery. These effects of catecholamines were independent of the venous pH, the plasma bicarbonate and serum glucose levels, and urinary potassium excretion, and they did not appear to be due to insulin. High norepinephrine and epinephrine levels confirmed the release of catecholamines capable of stimulating alpha- and beta-receptors. Exercise work did not differ among the groups. beta-Adrenergic receptors appear to moderate the acute hyperkalemia of exercise, whereas alpha-adrenergic receptors act to enhance hyperkalemia and may protect against hypokalemia when exertion ceases.

The effect of age and sodium depletion on cardiovascular response to orthostasis.

To test the hypothesis that normal age-related limitations in cardiovascular homeostasis may become clinically significant under stress, the cardiovascular response to postural change was assessed in six young and six old healthy subjects before and after modest diuretic-induced sodium depletion. Before diuresis, systolic blood pressure was maintained (from 110 +/- 4 to 113 +/- 6 mm Hg) while heart rate increased 22% (from 67 +/- 2 to 82 +/- 5 beats/min) at 3 minutes after 60-degree upright tilt in young subjects. After a significant diuretic-induced weight reduction and natriuresis, the young again maintained systolic blood pressure (from 110 +/- 4 to 110 +/- 6 mm Hg) and increased heart rate 49% (from 68 +/- 2 to 101 +/- 5 beats/min; p less than 0.05, compared with prediuresis values) in response to the same postural stimulus. During the prediuresis tilt, the older subjects showed no change in systolic blood pressure (from 132 +/- 4 to 134 +/- 6 mm Hg) and a 9% increase in heart rate (from 68 +/- 3 to 74 +/- 2 beats/min). After a similar significant weight reduction and sodium loss, the older subjects showed a significant reduction in systolic blood pressure (from 132 +/- 6 to 108 +/- 6 mm Hg; p less than 0.05) and a 17% increase in heart rate (from 69 +/- 4 to 81 +/- 3 beats/min; p less than 0.05) during tilt compared with values in young subjects. Three of six elderly subjects noted postural symptoms. These results suggest that, although the healthy old may appear well compensated under optimal conditions, decreased cardiovascular reserve renders them susceptible to postural change following mild sodium depletion.

A Study of Induced Hyponatremia in the Prevention and Treatment of Sickle-Cell Crisis

Because the formation of sickle cells is dependent on the intracellular concentration of deoxyhemoglobin S, we investigated the possibility of altering or preventing sickle-cell crises by reducing serum sodium so as to cause red cells to swell. In three patients with sickle-cell anemia who had been disabled by recurrent painful crises, sustained dilutional hyponatremia was induced by 1-desamino-8-D-arginine vasopressin (DDAVP) in combination with a high fluid intake. Mean corpuscular hemoglobin concentration fell, and the degree of sickling at low partial oxygen pressure was reduced, as determined by morphologic criteria and by increased oxygen affinity of blood. Chronic hyponatremia (serum sodium, 120 to 125 mmol per liter) reduced the frequency of painful crises, whereas acutely induced hyponatremia abbreviated the duration of crises. These results, although preliminary, are encouraging enough to warrant further study of the safety and effectiveness of induced hyponatremia in the prevention and treatment of sickle-cell crises.

Impairment of Extrarenal Potassium Disposal by α-Adrenergic Stimulation

Abstract Since β-adrenergic stimulation enhances extrarenal potassium uptake, we postulated an opposite effect of the α-adrenergic nervous system. Seven healthy subjects were given intravenous potassium chloride (0.5 mmol per kilogram of body weight), in the presence and absence of the α-agonist phenylephrine. After potassium chloride alone, the potassium level rose to 0.64±0.03 mmol (mean ±S.E.M.); phenylephrine augmented the rise (0.93±0.09 mmol, P<0.025) and prolonged it, without changing urinary potassium excretion. Subsequent administration of potassium and phenylephrine together with the α-antagonist phentolamine blocked the rise in the potassium level due to phenylephrine and shortened the duration of elevation, again without affecting urinary potassium excretion. No changes in plasma renin and aldosterone levels or in serum insulin concentrations occurred, to account for these findings. Stimulation of α-adrenergic receptors impairs extrarenal disposal of an acute potassium load — the opposite effe...

Adrenergic Control of Serum Potassium

THE behavior of excitable cells like those in muscles and nerves, of secretory cells like those in the kidney or gastrointestinal tract, and indeed of all the bodys cells, whatever their function,...

Effect of protein ingestion on urinary dopamine excretion. Evidence for the functional importance of renal decarboxylation of circulating 3,4-dihydroxyphenylalanine in man.

Since dietary protein increases urinary dopamine (DA) excretion in animals, this study was undertaken to assess the role of DA production in the acute changes in renal function following protein ingestion in man. Excretion of DA, sodium, potassium, water, solute, and creatinine were measured in six normal men in 30-min intervals over 5 h after oral ingestion of protein and/or carbidopa, an inhibitor of DA formation from 3,4-dihydroxyphenylalanine (DOPA). Overall, protein increased urinary DA 50% (P = 0.031) while carbidopa reduced it 70% (P less than 0.0001), although suppression of DA excretion by carbidopa was not uniform over the 5 h of observation. Carbidopa doubled the level of DOPA in venous plasma and greatly magnified the DOPA response to protein. Inhibition of decarboxylase activity reduced excretion of sodium, potassium, solute and water after protein ingestion. These results indicate that extraneuronal DOPA decarboxylation in kidney contributes to acute protein-induced changes in renal function in man and suggest a general role for the decarboxylation of circulating DOPA in the expression of dopaminergic effects on the kidney in vivo.

Extrarenal Potassium Tolerance in Chronic Renal Failure: Implications for the Treatment of Acute Hyperkalemia

The role of extrarenal potassium homeostasis is well recognized as a major mechanism for the acute defense against the development of hyperkalemia. The purpose of this report is to examine whether or not the various mechanisms of extrarenal potassium regulation are intact in patients with end-stage renal disease (ESRD). The available data suggest that with the development of ESRD and the uremic syndrome there is impaired extrarenal potassium metabolism that is related to a defect in the Na,K-adenosine triphosphatase (ATPase). The responsiveness of uremic patients to the various effector systems that regulate extrarenal potassium handling is discussed. Insulin is well positioned to play an important role in the regulation of plasma potassium concentration in patients with impaired renal function. The role of basal insulin may be even more important than previously appreciated, since somatostatin infusion causes a much greater increase in the fasting plasma potassium in rats with renal failure than in controls. Furthermore, stimulation of endogenous insulin by oral glucose results in a greater intracellular translocation of potassium in uremic rats than in controls. Under at least two common physiologic circumstances, feeding and vigorous exercise, endogenous catecholamines might also act to defend against acute increments in extracellular potassium concentration. However, it is important to appreciate that the response to beta 2-adrenoreceptor-mediated internal potassium disposal is heterogeneous as judged by the variable responses to epinephrine infusion. Based on the evidence presented in this report, a regimen for the treatment of life-threatening hyperkalemia is outlined. Interpretation of the available data demonstrate that bicarbonate should not be relied on as the sole initial treatment for severe hyperkalemia, since the magnitude of the effect of bicarbonate on potassium is variable and may be delayed. The initial treatment for life-threatening hyperkalemia should always include insulin plus glucose, as the hypokalemic response to insulin is both prompt and predictable. Combined treatment with beta 2-agonists and insulin is also effective and may help prevent insulin-induced hypoglycemia.