Claudio Vergassola

Ambulatory Blood Pressure Monitoring: How Reproducible Is It?

We tested the reproducibility of ambulatory blood pressure monitoring (ABPM) by the use of agreement plots. Thirty-two normotensive volunteers underwent ABPM on four separate days (interval 28 days), on the same typical weekday. Sleeping time was restricted to the ABPM nighttime subperiod from 11:00 PM to 7:00 AM. Twenty-four-hour average values-both systolic and diastolic-daytime average values, and nighttime average values, as well as standard deviation (SD) values, were analyzed for differences (analysis of variance). Adaptation occurred from the first to the fourth ABPM, ie, average 24 h, daytime, and nighttime values were lower (-1 to -3 mm Hg) during the fourth recording than the first (P < .05 to P < .01). The agreement analysis showed a surprisingly high agreement among the four data sets (ie, differences from +/-2.54 to +/-5.92 mm Hg; +/-2 SD of the distribution). We concluded that reproducibility of ABPM seems excellent, but adaptation may occur, even in normotensive volunteers under research conditions. Caution must be paid before labeling a patient as hypertensive, because initial ABPM may yield higher values than later monitorings.

Simultaneous Measurement of Plasma Catecholamine (Norepinephrine, Epinephrine, and Dopamine) and Free N—Methyl Dopamine (Epinine) Levels, by HPLC with Electrochemical Detection

Abstract Epinine is the active moiety of ibopamine, a cardiovascular prodrug used in congestive heart failure. This catecholic compound shows dopaminergic and adrenergic properties. Moreover the drug seems to affect plasma catecholamine levels in patients with heart failure. Here we present a method developed for the simultaneous determination of epinine and catecholamine plasma levels. Free epinine and catecholamines were extracted from human venous plasma via an alumina adsorption procedure. The extracts underwent an ion-pair reversed-phase HPLC separation with three-electrode coulometry. Quantitation was made by an internal standard method. Coefficients of variation were 0.997). The detection limits were ≤ 5 pg of each catechol after extraction. This method allows about 50 low cost determination to be done in a working day.

Yohimbine effects on blood pressure and plasma catecholamines in human hypertension

The purpose of this study has been to test the hypothesis of an alpha 2-adrenoreceptor alteration in human essential hypertension. The design of the study involved the oral administration of 10 mg yohimbine, an alpha 2-adrenergic antagonist, to 25 healthy volunteers and 29 sex- and age-matched untreated hypertensive patients. Volunteers and patients were studied twice in random order, after placebo or yohimbine treatment, in supine and upright positions. Arterial pressure and heart rate were monitored by servoplethysmomanometry, and venous plasma catecholamines were determined by HPLC with electrochemical detection. Yohimbine induced a significant increase in diastolic pressure only in the hypertensive patients. Plasma norepinephrine was increased significantly in both yohimbine-treated groups, but the percent increase of plasma norepinephrine after the standing test was decreased significantly only in the healthy yohimbine-treated subjects. Plasma dopamine was increased significantly only in the healthy yohimbine-treated subjects. The response of plasma dopamine to the upright position was modified only in the healthy yohimbine-treated subjects. The decrease observed after 2 min of standing was abolished, showing the involvement of alpha 2-adrenoreceptors in the physiologic response of plasma catecholamines in healthy volunteers. Our data may be consistent with some in vivo evidence of an alpha 2-adrenoreceptor desensitization or an alteration in the balance of alpha-adrenoreceptors in human hypertension.

Blood Pressure Evaluation by Noninvasive and Traditional Methods: Consistencies and Discrepancies Among Photoplethysmomanometry, Office Sphygmomanometry, and Ambulatory Monitoring. Effects of Blood Pressure Measurement

Three hundred eight outpatients referred for hypertension were studied. A continuous beat-to-beat noninvasive recording (Finapres) of blood pressure evaluated the blood pressure increase (9 mm Hg systolic and 4 mm Hg diastolic) induced by office sphygmomanometry. Thereafter, patients underwent a 24-h ambulatory blood pressure monitoring. The evaluation against Finapres showed that office sphygmomanometry overestimates the systolic blood pressure by 3 +/- 36 mm Hg (mean +/- 2 SD) and the diastolic blood pressure by 15 +/- 25 mm Hg (mean +/- 2 SD). Blood pressure monitoring showed similar discrepancies. On the basis of both monitoring (normalcy defined from a population of 550 normotensive subjects) and office sphygmomanometry, patients were considered normotensive, hypertensive (either untreated or under active drug treatment), white coat hypertensive (monitoring below the 95th percentile and sphygmomanometry more than 140/90 mm Hg, either untreated or under active drug treatment), and reverse white coat patients (monitoring over the 95th percentile and sphygmomanometry less than 140/90 mm Hg). Patients showed different levels of alert reaction (the highest in white coat hypertensive and the lowest in reverse white coat hypertensive patients), and a similar increase in blood pressure induced by conventional sphygmomanometry. During initial readings of ambulatory monitoring, blood pressure decreased from the first reading to the third reading. This decrease is related to the increase of blood pressure under sphygmomanometry. Caution should be paid in interpreting results of sphygmomanometry (error level in the single patient as high as +/- 40 mm Hg), and interpreting and averaging results of the first hour of blood pressure monitoring (variably affected by the alert reaction to the clinical environment).

HPLC with electrochemical detection of catecholamines in human plasma. A mini-review

Abstract Since 1970s HPLC received growing attention among catecholamine (CA) assay methods. Earlier methods such as colorimetric (1) or fluorimetric (2) nowadays seem obsolete. Radiotracer methods are usually effective for the determination of norepi-nephrine (NE) and epinephrine (Epi) in human plasma, although the high cost per sample, the poor sensitivity regarding plasma dopamine (DA), the involvement of radiolabelled compounds and the te-

Plasma dopamine response to sympathetic activation in man: A biphasic pattern

We studied the plasma catecholamine response to standing and bicycle ergometric tests in 16 normal male subjects. During the standing test (performed in 10 subjects), we observed an early increase in plasma dopamine together with the fast increase in norepinephrine values; in the second half of this test (i.e. from 5 to 10 min of standing), we observed an increase in plasma dopamine levels. During the ergometric test (performed in 6 subjects), we observed a plasma dopamine increase at the maximal exercise; this persisted during the early recumbent recovery phase (6 min), despite the clear-cut decrease of both norepinephrine and epinephrine plasma levels. Our data are not in agreement with previous papers describing a simple increase in plasma dopamine after stimulation. This paper provides no informations regarding the mechanisms of this response of plasma dopamine. Other approaches must be used to study this aspect more directly.

Free and sulfoconjugated catecholamines in normotensive uremic patients: effects of hemodialysis.

In 9 normotensive uremic patients undergoing chronic hemodialysis, the baseline plasma catecholamines varied widely from low-normal to very high; sulfoconjugated plasma catecholamines were constantly high. A dialysis-induced fall of all sulfated catecholamines and epinephrine was observed. Norepinephrine decreased in 5 patients and increased in 4, with a strong inverse correlation between predialysis norepinephrine and delta norepinephrine (p less than 0.0001). No correlation was evident between clinical parameters (mean arterial pressure, heart rate) and catecholamines (both predialysis and postdialysis). Significant (p less than 0.0001 and p less than 0.0002) inverse correlations between epinephrine and norepinephrine and their sulfoconjugation degree were demonstrated only in predialysis. Our data may support the presence of a uremic autonomic neuropathy and adrenoceptor damage.

Absence of correlations between plasma catecholamine levels and mononuclear leukocyte β2-adrenergic receptors in the elderly

To assess the effects of aging on catecholamine plasma levels and mononuclear leukocyte (NML) beta 2-adrenergic receptors and on the possible relationships between these two parameters, we evaluated two groups of human subjects: 18 elderly volunteers (age 65-70 years) and 13 young volunteers (age 21-35 years). Norepinephrine plasma levels were significantly higher in the elderly subjects compared to the younger ones (P less than 0.05), whereas plasma epinephrine levels were not different. Also MNL beta 2-adrenoceptor density was significantly higher in elderly subjects (P less than 0.05). The binding dissociation constants were not significantly different. In young subjects there was a significant (P less than 0.02), inverse relationship between receptor densities and plasma norepinephrine levels; this relationship was not present in elderly persons. Our data suggest that the increase in beta 2-adrenoceptors may be due to a compensatory phenomenon, owing to the reduced beta-adrenergic sensitivity observed in the elderly subjects; moreover, the regulation of beta-adrenoceptors by plasma catecholamines seems to be altered by aging.

Measurement of Conjugated Catecholamines in Human Plasma. A Low Cost HPLC-ECD Method

Abstract We present an HPLC assay with electrochemical detection of conjugated catecholamine levels in human plasma. This method allows the direct assessment of the conjugated catecholamine values without the subtraction of the free catecholamine amounts: the assay is performed in the residual supernatant after the extraction (and the assay) of free catecholamines. The results are comparable with the classic enzymatic and acid-neat hydrolysis methods (which yield the sum of free and conjugated catecholamine concentrations). This technique shows good reproducibility (within-run and between-run CVs < 8% in the physiological range), and sensitivity (< 20 pg per each deconjugated catecholamine per extract). This method allows about 30 low cost determinations of plasma free and conjugated catecholamines to be done in a working day.

Effects of opioid substances on cAMP response to the β-adrenergic agonist isoproterenol in human mononuclear leukocytes

The effects of different opioid substances on isoproterenol and forskolin-stimulated cyclic AMP (cAMP) intracellular accumulation, and on the binding of 125I-pindodol (IPIN) to beta 2-adrenoceptors were studied in human mononuclear leukocytes (MNL). The opioids used were alpha-endorphin, beta-endorphin, tau-endorphin, DAGO (a mu receptor agonist), dermenkephalin (a delta receptor agonist and morphine. Only morphine was able to increase the cAMP response to isoproterenol. The EC50 of isoproterenol for cAMP accumulation was shifted leftward by morphine; this effect was blocked by naloxone. On the contrary, the cAMP response to forskolin, direct activator of adenylate cyclase, was similar in the control test with respect to the experiments with morphine. The five opioid peptides induced no changes in the dose-response curves with isoproterenol and forskolin. Furthermore, none of the opioids induced changes in the IPIN binding. Our data show that morphine is able to exert a significant enhancement of the response of beta 2-adrenergic receptors to isoproterenol in human mononuclear leukocytes. This effect seems to be mediated by mu opioid receptors and seems to involve G protein.