Color duplex measurement of cerebral blood flow volume: intra- and interobserver reproducibility and habituation to serial measurements in normal subjects.

Color duplex flowmetry of internal carotid and vertebral arteries permits estimation of intravascular flow volumes and global cerebral blood flow volume (CBFV) by summing the flow volumes measured in each of the four extracranial vessels. Intravascular flow volumes were calculated as the product of angle-corrected time-averaged flow velocity and the cross-sectional area of the vessel. The reliability of this new method was tested in a prospective, intra- and interdiane, intra- and interobserver reproducibility study of 32 healthy subjects aged 7-57 years. In each subject, CBFV was tested by each observer twice on day 1 and once on day 2 in consecutive recordings. In each artery, both examiners found closely similar mean intravascular flow volumes. Intradiane interobserver reproducibility of CBFV was high on both days (correlation coefficient, CC, 0.90 and 0.85, p < or = 0.0001; coefficient of variance, CV, 10.0 and 10.4%, respectively), as was the interdiane comparison (CC = 0.81, p < or = 0.0001; CV < or = 13.3%). Intraobserver reproducibility was even higher. On both days, there was a progressive decrease in CBFV from each subject's first to the last examination within a 1-h examination period (day 1: 717 +/- 150 ml/min to 690 +/- 120 ml/min; difference, p < or = 0.05; day 2: 700 +/- 120 ml/min to 665 +/- 126 ml/min; difference, p < or = 0.01). This habituation effect was more pronounced in subjects with high initial CBFV. Reproducibility of CBFV is comparable to that of mean CBF measurements with 133Xe inhalation and H2 15(O) positron emission tomography techniques reported by other groups. This method makes serial bedside-monitoring of CBFV feasible without posing the risks of radiation exposure.

Cholestyramine-induced hyperchloremic metabolic acidosis.

Cholestyramine is a nonabsorbable anion exchange resin that is used predominantly for the treatment of hypercholesterolemia in adults and the management of acute diarrhea in children. The authors report two cases of severe hyperchloremic nonanion gap metabolic acidosis associated with the use of cholestyramine therapy. The authors recommend that patients taking cholestyramine who have concomitant renal insufficiency or who are volume depleted or who are taking spironolactone be monitored carefully for the emergence of a hyperchloremic metabolic acidosis.

Lymphocyte suppression by rolipram with other immunosuppressive drugs.

Pentoxifylline, a nonselective phosphodiesterase inhibitor, has immunomodulatory activity in vitro and in vivo and potentiates the suppressive effects of glucocorticoids and cyclosporine on lymphocyte proliferation in vitro. Since phosphodiesterase isotypes 3 and 4 predominate in lymphocytes, the authors measured the suppressive effect of rolipram alone and in combination with low concentrations of methylprednisolone and calcineurin enzyme inhibitors, compared to that of pentoxifylline on mitogen-stimulated lymphocyte proliferation. The percent inhibition of 3H-thymidine incorporation by both 10(-5) and 10(-8) mol/L concentrations of rolipram were significantly greater than that by both 10(-4) mol/L pentoxifylline and 10(-8) mol/L methylprednisolone. The percent inhibition by the combination of 10(-5), but not 10(-6), mol/L rolipram and methylprednisolone was significantly greater than that by 10(-4) mol/L pentoxifylline and methylprednisolone. Potentiation of the suppressive effects of cyclosporine and tacrolimus by rolipram was less consistent. Measurement of cell culture supernatant concentrations of interferon gamma and interleukin-10 indicate that one of the mechanisms underlying the immunosuppressive activity of rolipram is a significantly disproportionate inhibition of the proinflammatory cytokine, interferon gamma.

Pentoxifylline potentiates in vitro lymphocyte suppression by glucocorticoids and immunosuppressive drugs.

Pentoxifylline, which has immunomodulatory effects in addition to its better known rheologic effects, might potentiate the effectiveness of traditional immunosuppressive drugs. We therefore studied the suppressive effect of pentoxifylline in combination with clinically relevant concentrations of prednisolone, methylprednisolone, cyclosporine, tacrolimus, rapamycin, and mycophenolic acid on mitogen-stimulated lymphocytes from 29 patients with glomerular diseases. Inhibition of lymphocyte proliferation obtained with 10(-7) and 10(-8) mol/L concentrations of the glucocorticoids and with 300 ng/mL cyclosporine was significantly increased when each was combined with 5, 25, or 50 microg/mL of pentoxifylline. The additive inhibitory effect of pentoxifylline in combination with 10(-7) mol/L glucocorticoids was inversely proportional to the inhibitory effect of the 10(-7) mol/L concentration of glucocorticoid alone, suggesting that the less sensitive the patient's cells, the greater the potentiation by pentoxifylline. The greatest degree of potentiation by pentoxifylline occurred when combined with the lower (10(-8) mol/L) concentration of glucocorticoids. Pentoxifylline also significantly increased lymphocyte suppression in combination with 150 and 300 ng/mL concentrations of cyclosporine, 5 ng/mL of tacrolimus, 2.5 x 10(-7) mol/L mycophenolic acid, and 10 ng/mL of rapamycin. These in vitro results suggest that pentoxifylline might have steroid-sparing effects and contribute to improved clinical outcomes from immunosuppressive treatment of renal diseases.

Lymphocyte suppression by glucocorticoids with cyclosporine, tacrolimus, pentoxifylline, and mycophenolic acid.

Methylprednisolone has been found to be significantly more suppressive than prednisolone (the pharmacologically active metabolite of prednisone) of mitogen-stimulated human lymphocyte proliferation. In this study, peripheral blood mononuclear cells (PBMC) from end stage renal disease patients were cultured with phytohemagglutinin (PHA) alone and with methylprednisolone and prednisolone individually, as well as each glucocorticoid (10(-7) mol/L) in combination with 300 ng/ml cyclosporine, 10 ng/ml tacrolimus, 25 microg/ml pentoxifylline, and 10(-7) mol/L mycophenolic acid. Under each experimental condition, the mean +/- SD % inhibition of PHA-stimulated 3H-thymidine incorporation was significantly greater with methylprednisolone than with prednisolone: methylprednisolone 55 +/- 17 versus prednisolone 28 +/- 14, p < 0.001; methylprednisolone + cyclosporine 76 +/- 18 versus prednisolone + cyclosporine 52 +/- 18, p < 0.001; methylprednisolone + tacrolimus 74 +/- 18 versus prednisolone + tacrolimus 50 +/- 20, p = 0.001; methylprednisolone + mycophenolic acid 69 +/- 14 versus prednisolone + mycophenolic acid 46 +/- 15, p < 0.001. These results confirm and extend previous observations and suggest that methylprednisolone might be more effective than prednisone in treatment protocols used to suppress allograft rejection.

Lymphocyte responsiveness to glucocorticoids, cyclosporine, or both.

The reason why some patients with glomerular diseases respond to steroid treatment and others do not remains obscure, and it is not possible to prospectively evaluate the probability of response in individual patients. One factor that might contribute to the clinical response to treatment could be the relative sensitivity of a patient's immune system to the suppressive effects of steroids or other immunosuppressive agents. To evaluate this possibility, phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC) from 16 patients with various biopsy-proven glomerulopathies were cultured with prednisolone or methylprednisolone in final concentrations of 10(-5) to 10(-8) mol/L. From the dose-response curves, the concentration of steroid required to cause 50% inhibition (IC50) of the PHA-induced proliferative response was determined. The PBMC from 10 patients also were cultured with 400 ng/mL cyclosporine both alone and with 10(-7) mol/L steroid, and the inhibitory effects were calculated. There was considerable heterogeneity in the sensitivities of individual patients to steroid inhibition, and the mean +/- SEM IC50 was significantly lower for methylprednisolone than for prednisolone. Cyclosporine caused 50% or greater inhibition in 6 of the 10 patients but had < 10% inhibitory effect in 2 patients. In most patients studied, cyclosporine plus steroid was significantly more inhibitory than cyclosporine alone, but the combination was usually no more effective than 10(-7) mol/L methylprednisolone alone. These results are consistent with the hypothesis that differences in the sensitivity of individual patient's immune systems to the immunosuppressive effects of steroids and cyclosporine might contribute to differences in their clinical responsiveness to treatment.

Suppression of lymphocyte interleukin-2 receptor expression by glucocorticoids, cyclosporine, or both.

Although glucocorticoids and cyclosporine are frequently used to treat patients with various types of glomerulopathy, clinical responses to treatment vary considerably. Considerable interindividual heterogeneity in the suppressive effects of glucocorticoids on lymphocyte proliferation in vitro has been previously reported, suggesting that differences in the pharmacodynamic responsiveness of the immune system to these agents might be an important determinant of how well an individual patient responds to treatment. It also has been shown that methylprednisolone is significantly more suppressive than prednisolone. To identify cellular mechanisms by which these drugs act, a study of the suppressive effects of prednisolone, methylprednisolone, and cyclosporine on lymphocyte proliferation and the expression of the cell surface receptor for interleukin-2 (IL-2R) was conducted using phytohemagglutin-stimulated peripheral blood mononuclear cells (PBMCs) from 13 patients with glomerulopathy and 12 control subjects. Heterogeneity among individuals in both parameters of lymphocyte responsiveness to these drugs was again found, and the significantly greater suppressive effect of methylprednisolone was confirmed for both proliferation and IL-2R expression in patients and control subjects. Cyclosporine alone was moderately suppressive. For most individuals, the greatest degree of suppression occurred when cells were exposed to both cyclosporine and glucocorticoid. Further studies are being conducted to determine whether pretreatment assessment of in vitro lymphocyte responsiveness has any predictive value regarding therapeutic efficacy of each drug in individual patients and to identify of those patients likely to require a more intensive or multidrug immunosuppressive regimen.

Relationship between lymphocyte and clinical steroid responsiveness in focal segmental glomerulosclerosis.

A remission in nephrotic proteinuria with steroid treatment appears to favorably alter the natural history of focal segmental glomerulosclerosis (FSGS). It is not known why some patients have a favorable response to steroid treatment whereas others do not. Considering the possibility that differences in the pharmacodynamic responsiveness to steroids among patients might be one factor, the authors examined the relationship between the pretreatment suppressive effect of steroids on lymphocyte proliferation (% inhibition) in vitro and the short- and intermediate-term responses of creatinine clearance (Clcr) and/or nephrotic proteinuria (urine protein/creatinine ratio = Up/c) in 13 patients with FSGS. There were significant correlations between % inhibition and the changes in Clcr at 3 (r = 0.92, p < 0.001) and 6 (r = 0.86, p < 0.01) months and the changes in Up/c at 3 months (r = -0.74, p = 0.02). Thus, the greater the pretreatment lymphocyte steroid sensitivity, the greater the increase in Clcr or decrease in Up/c. The changes in these parameters could not be accounted for on the basis of steroid dose or histopathology. The in vitro sensitivity of FSGS patients' lymphocytes to steroids may be of value in anticipating their clinical response to treatment.

Clinical application of recombinant erythropoietin in renal dialysis patients.

The advent of erythropoietin (EPO) can be considered one of the major advances over the past 10 years in the treatment of end stage renal disease (ESRD) patients who are receiving chronic maintenance dialysis. Not only has it resulted in freedom from transfusion dependency and elimination of the attendant risks, but it also has led to a significant improvement in the quality of life these patients are able to achieve within the physical and emotional limitations imposed by the multiple metabolic abnormalities, concomitant medical problems of ESRD, and the dialysis process itself.

Flow velocity and flow volume measurements in the extracranial carotid and vertebral arteries in healthy adults: reference data and the effects of age.

To establish reference data and to investigate the development of haemodynamics in the extracranial carotid and vertebral arteries, we performed a prospective study in 78 age- and gender-matched healthy adults from 20 to 85 y old. Angle-corrected flow velocities and luminal diameters were measured and waveform parameters and flow volumes calculated in all the arteries. Side-to-side differences and the influence of age on these parameters were also investigated. In the common carotid arteries, the internal carotid arteries and the vertebral arteries (CCA, ICA and VA, respectively) all flow velocities decreased significantly during ageing. The luminal diameter remained constant in all the carotid arteries, but increased slightly with age in the VA. An age-related decline of intravascular flow volume was observed in the ICA. Due to a pronounced decrease in end-diastolic flow velocity, the resistance index decreased in ICA and VA during ageing. There were no significant side-to-side differences in flow velocities and flow volumes in any of the extracranial arteries. The luminal diameters of the CCA, ICA and ECA were significantly smaller in women than in men. No relevant gender-related differences in flow velocities or waveform parameters were found in the extracranial arteries. There was no gender-linked difference in the flow volumes of the brain-feeding arteries and, in the ECA, flow volumes were significantly higher in men. Reference data on all flow velocities and waveform parameters, luminal diameters and flow volumes were established for different age groups between 20 and 85 y old. These data allow us to outline the development of cerebral haemodynamics during "benign ageing" and to utilise flow volume measurements in clinical practice, especially in patients with cerebrovascular diseases.

Differential glucocorticoid responsiveness of dialysis patients' lymphocytes.

OBJECTIVES: To evaluate in vitro glucocorticoid responsiveness of phytohemagglutinin (PHA)-stimulated lymphocytes from peritoneal dialysis (PD) patients compared to hemodialysis (HD) patients. DESIGN: Cross-sectional study of prevalent PD and HD patients and concurrent control subjects. SETTING: Urban outpatient dialysis unit. PATIENTS: 20 HD, 14 PD, and 20 control subjects. MEASUREMENTS: Using standard lymphocyte culture techniques, the concentration of prednisolone (P) and methylprednisolone (MP) required to cause 50% inhibition (IC50) of the proliferative response to phytohemagglutinin (PHA) was determined from dose-response curves. RESULTS: There was considerable heterogeneity in the sensitivities of individual patients' PBMC to glucocorticoid inhibition, especially those of HD patients' cells to P. The mean +/- SD IC50 for MP was significantly (p < or = 0.001) lower than that for P in each cohort: PD 11 +/- 5 vs. 34 +/- 18 ng/mL; HD 22 +/- 14 vs. 89 +/- 43 ng/mL; control subjects 14 +/- 11 vs. 55 +/- 56 ng/mL. Interestingly, the IC50 for both P and MP was significantly higher in HD than in either PD or controls (ANOVA, P: F = 6.56, p = 0.003; MP: F = 3.77, p = 0.03), indicating decreased sensitivity of HD lymphocytes to both drugs. There were no significant differences in mean IC50 values for either P or MP between PD and controls. No correlations were found between IC50 for either P or MP and patient age, gender, duration of dialysis, serum creatinine, serum albumin, or parathyroid hormone level. CONCLUSIONS: In vitro glucocorticoid responsiveness of dialysis patients' lymphocytes appears to be influenced by dialysis modality, but the factor(s) involved remains to be determined. The greater sensitivity of PD lymphocytes to both P and MP might result in better immunosuppression and less severe rejection after renal transplantation. MP may be particularly advantageous following renal transplantation for any patient manifesting relative or absolute in vitro resistance to P.

Differential glucocorticoid responsiveness of hemodialysis patients' lymphocytes.

Acute allograft rejection remains a problem after renal transplantation, even in the cyclosporine era. Interindividual differences in the pharmacodynamic responses of the immune system to immunosuppressive agents might contribute to the vulnerability of some patients to rejection. Having previously demonstrated decreased sensitivity of hemodialysis patients' lymphocytes to glucocorticoid suppression of mitogen induced proliferation, the authors undertook a separate study to assess the suppressive effect of glucocorticoids on lymphocyte responsiveness to allogeneic cells and mitogenic stimulation. Lymphocytes were isolated from 32 hemodialysis patients in clinically stable condition for studies in both phytohemagglutinin (PHA) stimulated cultures and in one-way mixed lymphocyte (MLR) cultures. From the concentration-response relationships derived from stimulated cultures with 10 (-6), 10(-7), and 10(-8) M concentrations of prednisolone and methylprednisolone, the concentration of steroid required to achieve 50% inhibition (IC50) of lymphocyte proliferation was determined. A broad range of IC50 values was found in both PHA and MLR cultures, but within individual patients, the IC50 values for both steroids correlated significantly between PHA and MLR cultures. The inhibitory effect of methylprednisolone was significantly greater than that of prednisolone in both PHA and MLR cultures. These results demonstrate a heterogeneity of pharmacodynamic responsiveness to prednisolone and methylprednisolone that is consistent with individuals in two in vitro models of cellular immune response. Pretransplant evaluation by these methods may help identify patients at risk of suboptimal immunosuppression and assist in selecting the steroid component of the immunosuppressive regimen.

Estimation of cerebral blood flow through color duplex sonography of the carotid and vertebral arteries in healthy adults.

BACKGROUND AND PURPOSE: To noninvasively estimate cerebral blood flow volume, a prospective study of color duplex sonography of the common, external, and internal carotid arteries and vertebral arteries of healthy adults was done. Cerebral blood flow was calculated with the sum of flow volumes in the internal carotid and vertebral arteries of both sides. METHODS: Using a 7.0-MHz linear transducer of a computed sonography system, cervical arteries of 48 volunteers (23 women, 25 men; mean age, 35 +/- 12 years) were examined. We measured angle-corrected time-averaged velocities and the diameter of the vessels and calculated the flow volumes of all arteries. In addition, peak systolic, maximum end-diastolic, and time-averaged maximum velocities and the resistance, pulsatility, and spectral broadening indexes were determined. Furthermore, we analyzed the side-to-side difference, age dependence, and long-term reproducibility of these parameters. RESULTS: The mean +/- SD values of flow volumes in the common, internal, and external carotid and vertebral arteries were 470 +/- 120, 265 +/- 62, 160 +/- 66, and 85 +/- 33 mL/min on either side, respectively. Total cerebral blood flow was 701 +/- 104 mL/min (corresponding to 54 +/- 8 mL/100 g per minute), with no variation in age or sex. Long-term reproducibility of cerebral blood flow and flow volumes in all vessels was significant (P < .01). CONCLUSIONS: We conclude that color duplex sonography of cervical arteries is potentially a practical method for estimating total cerebral blood flow. This noninvasive technique may be ideally suited for bedside and follow-up examinations of the critically ill patient. In future studies it should be compared with established radionuclide techniques.