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Biomedical subjects

M B Murphy

Publications and source records attributed to M B Murphy.

At least 55 records · Page 3Linked to original sources
PubMed1993

Fenoldopam mesylate versus sodium nitroprusside in the acute management of severe systemic hypertension.

Thirty-three patients with severe systemic hypertension defined as a diastolic blood pressure (DBP) > or = 120 mm Hg were randomized in a single-blind fashion to be treated with either intravenous fenoldopam mesylate (FNP) or sodium nitroprusside (NTP). Fenoldopam mesylate and NTP infusion rates began at 0.1 microgram/kg/minute and 0.5 microgram/kg/minute, respectively and were titrated to achieve a goal DBP of between 95 and 110 mm Hg; or a reduction of at least 40 mm Hg if the baseline DBP was > 150 mm Hg. Fenoldopam mesylate (n = 15) reduced blood pressure from 217/145 +/- 6/5 to 187/112 +/- 6/3 mm Hg (P < .001) at an average infusion rate of 0.5 +/- 0.1 microgram/kg/minute. The average time to achieve goal DBP with FNP was 1.5 +/- 1.4 hours. Nitroprusside (n = 18) reduced blood pressure from 210/136 +/- 5/2 to 172/103 +/- 6/2 mm Hg (P < .001) at an average infusion rate of 1.2 +/- .24 micrograms/kg/minute. Nitroprusside response time averaged 2 +/- 2.5 hours. There was no significant difference between the magnitude of effect seen with either FNP or NTP; nor was there any difference observed in the adverse effect rates of the two agents. Fenoldopam mesylate and NTP demonstrate similar overall efficacy in the treatment of severe systemic hypertension.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

Diurnal blood pressure variability and physical activity measured electronically and by diary.

In order for 24 h ambulatory blood pressure monitoring (ABPM) to be useful in clinical decision making, it is necessary to quantify ambient physical activity and to develop appropriate norms of ambulatory pressure for different levels of activity. The present study has compared the predictive value of physical activity determined by an electronic activity monitor or a written diary, for concomitantly recorded blood pressure during ABPM in healthy normotensive subjects. Each subject wore four activity monitors, on the right and left wrists, on the left ankle and at the waist, respectively. Linear regression analysis was performed for each subject to determine the correlation between ABPM data (systolic and diastolic blood pressure and heart rate) and activity data (obtained from diaries and the four monitors). Significant differences in the degree of correlation were found for both the location of the activity monitor and the time (1/2, 2, 5, 10, 15, and 30 min preceding blood pressure measurement) over which activity was averaged (P < .05 by two-way analysis of variance). The best correlation was obtained with the activity monitor worn on the dominant wrist, and when activity was averaged over 2 to 10 min preceding blood pressure determination, accounting for 18 to 69% (mean 36 +/- 5%) of systolic blood pressure variation. Diaries performed similarly in these well-motivated subjects. It is concluded that because of the significant interaction between activity and blood pressure, ABPM data should be interpreted only in the light of concomitant activity data.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Low predictive value of positive Osler manoeuvre for diagnosing pseudohypertension.

Pseudohypertension is a condition where indirectly determined BP (e.g. via sphygmomanometry) significantly overestimates actual intraarterial pressure. A patient who has a palpable, although pulseless, radial artery while the blood pressure cuff is inflated above systolic pressure, has a positive 'Osler sign'. This 'Osler manoeuvre' has been reported to predict the presence of pseudohypertension. To evaluate its importance in diagnosing pseudohypertension, 19 hypertensive patients deemed Osler-positive by at least two observers were studied. BP was determined indirectly using a stethoscope and mercury sphygmomanometer. Intraarterial pressure was determined by a brachial artery catheter-transducer-monitoring system. For both pressure-measurement techniques and each patient, six readings were averaged to give a single systolic and diastolic value. Mean arterial pressure was calculated as diastolic pressure plus one-third the pulse pressure. Pseudohypertension was defined as a sphygmomanometric mean pressure that exceeded intraarterial mean pressure by > or = 10 mmHg. In this group of 19 Osler-positive patients, stethoscope-sphygmomanometry underestimated systolic and overestimated diastolic intraarterial pressure. For mean pressure, sphygmomanometry was > or = 10 mmHg higher than intraarterial in two patients and > or = 10 mmHg lower than intraarterial in three patients. Thus, while two patients had pseudohypertension, three could be considered to have pseudohypotension, defined as a condition where indirect blood pressure significantly underestimates intraarterial pressure. Accordingly, a positive Osler manoeuvre did not reliably predict the presence of pseudohypertension in this population.

Aged↗
PubMed1992

Selecting optimum antihypertensive therapy: indications for choosing a calcium channel blocker.

In choosing the optimum antihypertensive agent for an individual patient, various factors should be considered. Demographic characteristics (e.g., age, gender, race) and the circadian pattern of blood pressure elevation may influence the response to therapy. Concomitant therapy for coexisting medical disorders must be evaluated for possible drug interactions. Calcium channel blockers, which can be used in any age group, may be particularly useful in hypertensive patients with certain concurrent conditions (e.g., coronary artery disease, migraine, or gastrointestinal motility disorders). Life-style, including occupation and leisure-time activities, may contraindicate the use of certain drugs in a particular patient. It also may be necessary to consider the economic status of the patient, particularly in the elderly, who often have limited disposable income. Since to a great extent successful therapeutic management of hypertension depends on patient compliance, reduced frequency of dosing (i.e., once or twice daily) is desirable. The clustering of morbid events in the hours immediately following awakening highlights the need for therapy that provides 24-hour control, thereby ensuring adequate pharmacodynamic effects during that crucial period. The challenge is to select the most appropriate first-line agent (diuretic, beta blocker, calcium channel blocker, or angiotensin-converting enzyme inhibitor) for a particular patient.

Age Factors↗
PubMed1992

Diurnal blood pressure variation and cardiac mass in American blacks and whites and South African blacks.

American blacks exhibit higher nocturnal blood pressure than American whites with similar daytime pressure. To determine whether this represents a true racial difference, as opposed to a consequence of different environmental factors, we measured ambulatory blood pressure, cardiac left ventricular mass, and urinary electrolyte excretion in 22 South African blacks (15 women, aged 36 +/- 12 years) and age, sex, and daytime mean pressure-matched American blacks and whites. While all three groups exhibited similar daytime blood pressure, American blacks displayed significantly higher nighttime mean blood pressure. Both African blacks and American whites experienced the same fall in nighttime blood pressure. Left ventricular mass index was highest in American blacks and lowest in South African blacks. Urine sodium excretion was similar in all groups, but both black populations excreted significantly less potassium than American whites. The data suggest that the differences in diurnal blood pressure rhythm between American blacks and whites do not represent a true racial difference, but more likely are environmental in origin. Furthermore, since both black populations had similar cation excretion rates, yet differed in blood pressure pattern and cardiac mass, divergence in dietary sodium or potassium intake cannot explain the ethnic group differences in the United States.

Adult↗
PubMed1992

5-Hydroxytryptamine receptor activity of the dopamine receptor agonist fenoldopam in canine tracheal smooth muscle.

Fenoldopam is a new vasodilator undergoing clinical trials for the treatment of hypertensive emergencies. Its pharmacologic effects result from activation of vascular dopamine-1 receptors. In canine tracheal smooth muscle strips, fenoldopam caused a concentration- and calcium-dependent increase in tension, which was not antagonized by atropine, indomethacin or the dopamine-1 receptor antagonist, SCH 23390. The EC50 (1.89 x 10(-6) M) exceeded that of serotonin or acetylcholine (8.38 x 10(-8) and 8.25 x 10(-8) M, respectively). Maximum tension was similar for fenoldopam and serotonin (11.6 +/- 1.5 g, n = 7 and 13.8 +/- 0.8 g, n = 24; P greater than .2) and considerably greater for acetylcholine (20.5 +/- 1.3 g, n = 14; P less than .005). The serotonin antagonists ketanserin and methysergide reversed completely the effect of fenoldopam (5 x 10(-7) M) with IC50 values of 2.5 x 10(-9) and 2.7 x 10(-9) M, respectively. Phentolamine, rauwolscine and chlorpheniramine were also effective, but they were less potent (IC50 values 6.6 x 10(-8), 1.0 x 10(-7) and 1.7 x 10(-7) M, respectively). By contrast, only very high concentrations (IC50, 5.3 x 10(-5) M) of terazosin produced an inhibition of fenoldopam-induced tension increases. The effect of antagonists could be overcome by increasing the fenoldopam concentration. Experiments performed on strips precontracted with serotonin (5 x 10(-8) M) revealed a very similar order of potency for the five antagonists. The addition of serotonin did not increase the tension produced by supramaximal concentrations of fenoldopam (and vice-versa), whereas acetylcholine increased tension further.(ABSTRACT TRUNCATED AT 250 WORDS)

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1992

Electrocardiographic changes during acute treatment of hypertensive emergencies with sodium nitroprusside or fenoldopam.

BACKGROUND: Electrocardiograms are routinely obtained before and during the acute treatment of hypertensive emergencies, usually to rule out "ischemic changes." Despite a few anecdotal reports of electrocardiographic changes, little is known about the incidence and significance of such changes, or their relationship to the treatment used. METHODS: We prospectively analyzed 12-lead electrocardiograms from 21 patients admitted for hypertensive emergencies (average blood pressure, 222 +/- 4/140 +/- 3 mm Hg). Patients were randomly assigned to treatment with sodium nitroprusside (n = 11) or the dopamine receptor agonist fenoldopam mesylate (n = 10). Electrocardiograms were obtained at baseline and within 30 minutes of reaching goal blood pressure (diastolic blood pressure, 100 to 110 mm Hg). RESULTS: There was no significant effect of either drug treatment on PR interval, QRS duration, QT interval, or R-wave amplitude, and no major ST-segment changes were noted. During treatment with either drug, the average T-wave amplitude decreased in all leads except aVR. New T-wave inversions in lead V4 occurred in two and four patients after fenoldopam and nitroprusside treatment, respectively. There were no clinically apparent episodes of myocardial ischemia in any patient. CONCLUSIONS: Even in the absence of obvious myocardial ischemia, a decrease in T-wave amplitude, including T-wave inversion, occurs commonly during acute blood pressure reduction in hypertensive emergencies, an observation that may be explained by the accompanying acute changes in cardiac chamber volumes.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1992

Blood pressure and fitness for work.

A survey was carried out to determine whether physicians in Occupational Medicine exclude job applicants because of hypertension and to examine the critical blood pressure cut-off values they apply. The survey sampled 116 respondents, members of the American Occupational Medical Association, Central States. Of these, 33 (28%) reported excluding hypertensives from work permanently, as the policy of one or more of the companies they serve. Another 78 physicians (68%) reported excluding hypertensives permanently on their own initiative when there was no company policy. The critical determining diastolic pressure varied from 90 to greater than 130 mm Hg; 22 respondents (19%) excluded individuals with mild hypertension. The results demonstrate that blood pressure is frequently used as a criterion for employment. Additionally, the level of blood pressure precluding work is arbitrary and variable. There is a need for consensus on appropriate guidelines to preclude inappropriate discrimination against hypertensive job applicants.

Blood Pressure↗
PubMed1991

Influence of diuretic therapy on the clonidine suppression test.

Moduretic has been reported to inhibit the suppression of plasma norepinephrine (NE) levels by the alpha 2 adrenoceptor agonist, clonidine. To determine whether plasma volume reduction by hydrochlorothiazide (HCTZ) or antagonism of Na+/H+ exchange by amiloride (the constituents of Moduretic) is responsible, the authors performed a modified clonidine suppression test (CST) in nine normal volunteers (aged 25 +/- 2 years), pretreated for 1 week with HCTZ 50 mg daily, amiloride 10 mg daily, or placebo, in a randomized, double-blind, crossover study. Baseline characteristics were identical on all study days, except serum [K+] and weight, which were lowest on HCTZ (3.6 +/- 0.2 mEq/L and 78.7 +/- 2.5 kg), compared with amiloride (4.2 +/- 0.1 mEq/L and 79.9 +/- 2.4 kg) and placebo (4.0 +/- 0.1 mEq/L and 80.2 +/- 2.7 kg, P less than .05). Oral clonidine (0.3 mg) produced a reduction in mean blood pressure by about 20%. Plasma norepinephrine levels were similar in patients receiving placebo, HCTZ, and amiloride (205 +/- 18, 272 +/- 40 and 277 +/- 44 pg/mL, P greater than .20), and decreased significantly during CST. The maximal reduction for each subject averaged 72.7 +/- 12.4%, 87.9 +/- 3.8%, and 82.9 +/- 5.7% for placebo, HCTZ, and amiloride. Clonidine also produced a four to seven-fold increase in plasma growth hormone levels, reduced salivary flow by about 75%, and increased the level of sedation. There were no differences among the three pretreatment regimens in the effects of clonidine, indicating that diuretic therapy does not need to be systematically discontinued in patients undergoing CST.

Adult↗
PubMed1991

A double-blind, randomized, placebo-controlled comparison of the metabolic effects of low-dose hydrochlorothiazide and indapamide.

To compare the metabolic effects of indapamide (I) and hydrochlorothiazide (HCTZ) at equivalent hypotensive doses, 11 hypertensive patients (5 male, 8 black, aged 56 +/- 8 yr--mean +/- SEM) having serum uric acid concentrations greater than 8.0 mg/dL while receiving previous therapy with thiazides, received 28-day courses of placebo, indapamide (2.5 mg/d), and HCTZ (25 mg/d) in randomized, double-blind, double-crossover design. Supine and standing blood pressures, weight, pulse rates and sera were obtained after each 28 day period. Blood pressures and weights were lowered (P less than .001 and 0.01, respectively) equally by the diuretics: supine blood pressures fell from 168 +/- 4/104 +/- 2 (placebo) to 153 +/- 4/93 +/- 2 (HCTZ) and 155 +/- 4/94 +/- 2 mm Hg (I); standing blood pressures (after 2 minutes upright) also decreased: 171 +/- 5/104 +/- 2 (placebo) to 156 +/- 5/93 +/- 2 (HCTZ) and 157 +/- 4/94 +/- 2 mm Hg (I). There was a statistically significant difference (P less than .05) across treatments by analysis of variance in both uric acid and potassium concentrations: serum urate (in mg/dL) was lowest with placebo (7.1 +/- 0.3), and rose to 8.3 +/- 0.2 with HCTZ (P less than .001 compared with placebo by paired t test), and 8.1 +/- 0.2 with I (P less than .005 vs. placebo). The urate concentration with I was significantly lower than that with HCTZ (P less than .02), but the magnitude of the difference was small (0.2 mg/dL).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1991

Intraocular pressure increases with fenoldopam, but not nitroprusside, in hypertensive humans.

Fenoldopam mesylate stimulates adenyl cyclase in porcine ocular trabecular meshwork and raises intraocular pressure in humans. To clarify whether this results from direct activation of the dopamine-1 receptor or indirectly from baroreflex sympathetic stimulation after blood pressure reduction, intraocular pressure was measured in 14 patients with accelerated/malignant hypertension, randomized between intravenous fenoldopam or sodium nitroprusside. Intraocular pressure was measured with a Perkins tonometer, before and at the twentieth minute of each dose increment. In seven patients with a mean blood pressure of 232/131 mm Hg treated with fenoldopam, intraocular pressure increased in a dose-dependent fashion, from 16 +/- 1 to 20 +/- 2 mm Hg (p less than 0.005). In contrast, seven patients with a mean blood pressure of 225/134 mm Hg treated with sodium nitroprusside exhibited no change in intraocular pressure (15 +/- 1 versus 14 +/- 1 mm Hg) despite similar blood pressure reduction. Increases in heart rate were not significantly different. Rates of urinary excretion of norepinephrine plus epinephrine increased significantly relative to baseline (p less than 0.05) but were not different between groups. These data suggest that the increase in intraocular pressure with fenoldopam results from specific activation of the dopamine-1 receptor and is not caused by baroreflex sympathetic stimulation. Because dopamine-1 receptors may modulate intraocular pressure, dopamine-1 receptor blockers might be useful therapy for glaucoma.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1991

Selective role of dopamine in the natriuresis produced by iso-osmotic saline infusion.

Endogenous dopamine (DA) selectively contributes to the natriuresis (UNaV) produced by infusion and dietary consumption of sodium chloride. The present study in anesthetized rats determined whether DA has a role in the natriuresis produced by small (2.0 +/- 0.11% increase in body weight) and large (17.9 +/- 0.58% increase in body weight) increments in extracellular fluid volume with iso-osmotic saline. Small volume expansion increased urine flow (V) by 59 +/- 15%, UNaV by 155 +/- 31%, and dopamine excretion by 25 +/- 9%. DA1-receptor blockade with SCH 23390 (SCH, 1.0 microgram/kg/min), attenuated the natriuresis; an increase in UNaV of only 69 +/- 15%. Large volume expansion increased V by 1,026 +/- 215% and UNaV by 2,735 +/- 899%, without affecting dopamine excretion. Increments in V and UNaV were unaffected by increasing doses of SCH (1.0 microgram/kg/min; 10 micrograms/kg/min; and 50 micrograms/kg bolus, followed by 10 micrograms/kg/min). Adequacy of DA1-receptor blockade was demonstrated by the fact that SCH (1.0 microgram/kg/min) attenuated the natriuresis produced by the DA1-receptor agonist, fenoldopam (0.1 micrograms/kg/min ia). We conclude that endogenous DA contributes to the natriuresis produced by small, but not large, increases in extracellular fluid volume with iso-osmotic saline.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1991

Diurnal blood pressure variation: differences among disparate ethnic groups.

We examined the possibility that excess cardiovascular morbidity in American blacks compared with whites might be partly the result of differences in diurnal blood pressure variation. Urban American blacks have higher night-time blood pressures and show a smaller increase in blood pressure during the waking day than whites. This difference is associated with a higher cardiac mass in the blacks and occurs despite similar duration and quality of sleep in blacks and whites. Both groups show similar levels of sympatho-adrenal activity at night, but the diurnal increase is smaller in blacks, paralleling the smaller increase in blood pressure. In Africa blacks show a diurnal pressure pattern similar to American whites. Disparities in cation consumption do not explain the differences in blood pressure variation between these groups.

Black People↗
PubMed1990

Williams syndrome in twins.

Two sets of identical twins with Williams syndrome have been reported previously. We report on 2 additional sets of presumed identical twins with Williams syndrome. All 4 patients had the typical Williams syndrome facial appearance, growth deficiency, and developmental delay. None of the patients had supravalvular aortic stenoses; however, all were diagnosed as having probable distal pulmonary artery stenosis. In the set of twins in which serum calcium was measured, one twin had an elevated serum ionized calcium level. These 2 sets of twins further document the occurrence of Williams syndrome in identical twins. To our knowledge, there are no reported cases of concordance in dizygotic twins. This adds further support to the likelihood that Williams syndrome is a genetic disorder.

Abnormalities, Multiple↗
PubMed1990

Cerebral blood flow during the acute therapy of severe hypertension with oral clonidine.

A major risk associated with the acute treatment of severe hypertension is a reduction in cerebral blood flow (CBF) with ischemic injury to the central nervous system. The authors studied CBF before and after the acute treatment of severe hypertension (diastolic blood pressure greater than 115 mm Hg) with clonidine in 13 patients. One patient did not reach goal blood pressure (diastolic blood pressure 105 mm Hg or a decrease by 30 mm Hg) after clonidine alone. In the remaining 12 patients, oral clonidine reduced supine blood pressure from 201.7 +/- 5.0/126.3 +/- 2.1 mm Hg to 149.4 +/- 5.3/96.8 +/- 1.7 mm Hg over an average time period of 85 +/- 7 minutes. Although mean CBF for the group did not change (72.6 +/- 4.2 v 73.7 +/- 3.5 mL/100 mg/min), a significant (greater than 10%) change occurred in 9 of the 12 patients (5 increases and 4 reductions). The magnitude and direction of the change were dependent upon initial CBF (r = -0.65, P less than .05); patients with low pretreatment CBF experienced an increase, whereas those with high initial flow exhibited a decrease. No significant adverse effects were observed. These data confirm previous reports that clonidine is effective in the acute treatment of severe hypertension and demonstrate that its effects on CBF are determined by the pretreatment levels of flow.

Administration, Oral↗