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Biomedical subjects

J V Amerena

Publications and source records attributed to J V Amerena.

6 recordsLinked to original sources
PubMed1999

Determination of accuracies of 10 models of home blood pressure monitors using an oscillometric simulator.

BACKGROUND: Patients and doctors often use home blood pressure monitoring (HBPM) to assess the control of hypertension. Despite its popularity there has always been some uncertainty with regard to its accuracy, reliability, reproducibility, and comparability. Although there are pre-market HBPM standards of accuracy, there are no standards to assure accuracy of individual HBPM units after they have been brought home. OBJECTIVE: Determination of reliability, reproducibility, and comparability of 10 models of home blood pressure monitors. METHODS: We used a Biotek BP Pump as an oscillometric simulator of systolic and diastolic blood pressures to determine reliability, reproducibility, and comparability of 10 devices. RESULTS: All of the units tested, except the Pollonex BP1000, produced reproducible readings with the pooled SD of four blood pressure settings less than 3.10 mmHg both for systolic and for diastolic measurements. The oscillometric blood pressure pump method was found to be very reproducible, with pooled differences of less than 2 mmHg and SD of less than 0.5 mmHg for a repeated series of measurements using the same monitor. Different machines of the same model were also very comparable, with pooled differences of less than 3.6 mmHg and pooled SD less than 0.7 mmHg both for systolic and for diastolic readings. There were 11-14 mmHg differences between models for all of the simulated blood pressure readings except that a 27 mmHg difference was measured at the 200 mmHg systolic blood pressure level. These differences will not necessarily be the same for measurements with humans instead of oscillometric signal generation. A system for grading the accuracy of the tested HBPM that defines accuracy of HBPM as within +/-2 SD of the average of 85 measurements is described. CONCLUSION: All models of home blood pressure monitors tested, with the exceptions of the Pollonex BP1000, produced reproducible readings and different machines of the same model were comparable.

Blood Pressure Monitors↗
PubMed1997

Home blood pressure as a predictor of future blood pressure stability in borderline hypertension. The Tecumseh Study.

We evaluated time-related blood pressure trends in the Tecumseh study participants, none of whom received antihypertensive treatment. At baseline the blood pressures were measured in the field clinic and by self measurement at home (twice daily for 7 days). After a mean of 3.2 +/- 0.42 years, the clinic and home pressure readings were repeated. Nine hundred forty-six subjects had clinic and home blood pressure readings at baseline. Of these 735 (380 men, 355 women; average age, 32 years) also completed the second examination. Blood pressure, morphometric data, and biochemical measures at the first examination were used as predictors of future clinic blood pressures. Five hundred ninety-six subjects were normotensive on both examinations (81%). Of 79 subjects (10.7%) with clinic hypertension (> 140 mg Hg systolic or 90 mm Hg diastolic) at baseline, 38 remained hypertensive ("sustained hypertension") and 41 became normotensive ("transient hypertension") after 3 years. Another 60 normotensives at baseline (10.4%) became hypertensive on second examination ("de novo hypertensives"; incidence; 8.1%). The home blood pressure readings on both examinations were reproducible. The three hypertensive groups had elevated home blood pressure, were overweight, had dyslipidemia, and higher insulin values. Only the home blood pressure proved predictive of subsequent blood pressure trends. A home blood pressure of 128 and 83 mm Hg or higher detected "sustained" hypertension with a 48% sensitivity and 93% specificity. Readings of 120 and 80 mm Hg or lower predicted future normotension with a 45% sensitivity and a 91% specificity. We conclude that self determination of the blood pressure at home is useful in the management of borderline hypertension. An algorithm for the management of these patients is proposed.

Adolescent↗
PubMed1996

Angiotensin mediates forearm glucose uptake by hemodynamic rather than direct effects.

Insulin sensitivity may be improved with the angiotensin-converting enzyme inhibitor captopril, suggesting that inhibition of angiotensin II (Ang II) improves insulin resistance. However, the administration of systemic Ang II has also been associated with an improvement in rather than worsening of glucose utilization. Since both stimulating and antagonizing the renin-angiotensin system improve glucose uptake and both angiotensin-converting enzyme inhibitors and intravenous Ang II elicit skeletal muscle vasodilation, it is conceivable that hemodynamic factors rather than a direct effect of either Ang II or angiotensin-converting enzyme inhibitors on skeletal muscle metabolism modulate the increase in glucose utilization. The direct effects of Ang II on glucose extraction in intact human skeletal muscle have not been previously described. We investigated the effects of local infusion of Ang II on glucose uptake in the forearm of 20 healthy subjects. With the use of the isolated insulin-perfused forearm model, local plasma insulin values were raised to 100 mU/mL over fasting values and maintained there for a 90-minute infusion period. After the first 60 minutes of insulin alone, Ang II was infused into the brachial artery for the last 30 minutes. Intra-arterial Ang II infusion caused a 38% decrease in forearm blood flow (P <.05) and 59% increase in the arteriovenous glucose gradients (P <.05) to maintain a steady glucose utilization (a decrease of 4%, P=NS). Thus, local Ang II infusion does not impair insulin-stimulated glucose utilization. Furthermore, glucose extraction increases to compensate for the decrease in forearm blood flow (as the Fick principle would predict for freely diffusible substances). We conclude that the described increase in glucose utilization from systemic infusion of Ang II and during angiotensin-converting enzyme inhibitor treatment is mediated by hemodynamic factors rather than a direct effect of Ang II on skeletal muscle metabolism.

Adult↗
PubMed1994

Vasoconstriction with norepinephrine causes less forearm insulin resistance than a reflex sympathetic vasoconstriction.

We used the insulin-perfused human forearm model to assess the effects of vasoconstriction induced with norepinephrine on the extraction of glucose in the forearm in two groups of healthy young volunteers. The norepinephrine findings were compared with a previously studied group in which vasoconstriction has been caused by reflex activation of the sympathetic nervous system. The aim of the study was to determine the relative importance of hemodynamic and receptor-mediated mechanisms of insulin resistance. Plasma insulin, arterial and venous glucose samples, and forearm blood flow were measured at 10-minute intervals during a 30-minute baseline, a 60-minute intra-arterial insulin infusion, and during 30 minutes of insulin infusion plus vasoconstriction. Group 1 (n = 14) had physiological vasoconstriction induced by inflation of bilateral thigh cuffs to 40 mm Hg to cause pooling of blood in the lower extremities and reflex vasoconstriction in the forearm; group 2 (n = 8) had intra-arterial infusion of norepinephrine to achieve the same degree of vasoconstriction as seen with inflation of thigh cuffs in group 1. Subjects in group 3 (n = 7) had infusion of intra-arterial norepinephrine to achieve a twofold increase in physiological vasoconstriction. With a physiological decrease in forearm blood flow (group 1), there was a 19% decrease in forearm blood flow resulting in a 23% reduction in glucose uptake in the forearm (P < .03). The same degree of reduction in forearm blood flow with a predominantly alpha-adrenergic agonist, norepinephrine (group 2), causes much less insulin resistance (a decrease in utilization of 13%) (P < .04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Arterial lignocaine concentrations following cervical plexus blockade for carotid endarterectomy.

Arterial lignocaine concentrations were measured in twenty-six patients who had carotid endarterectomy performed under deep and superficial cervical plexus blockade. A dose of 6 mg/kg of 1.5% lignocaine with 1:200,000 adrenaline was used, as well as additional supplementation by the surgeons when required. Concentrations obtained produced a mean peak of 5 micrograms/ml and were similar to those previously reported from multiple bilateral intercostal blockade, which is the regional technique widely considered to produce the highest systemic levels of local anaesthetic. Apart from one peak concentration of 16.9 micrograms/ml, levels were well below the convulsion threshold. We find the technique acceptable and safe for carotid surgery and lignocaine toxicity is not identified as a problem.

Aged↗