Low-level Elevations Research Articles

Chronic renal neuroadrenergic hypertension is associated with increased renal norepinephrine sensitivity and volume contraction.

Individuals with essential hypertension have been characterized by increased renal sympathetic vascular tone with decreased plasma volume and normal cardiac output compared with normotensive individuals. We used a servo-controlled intrarenal infusion system to evaluate the hemodynamic, renal excretory, and plasma hormonal responses to 28-day, low-level elevations in the intrarenal adrenergic neurotransmitter norepinephrine. In uninephrectomized dogs (n = 6), servo-controlled norepinephrine infusion increased mean arterial pressure from 95.6 +/- 3.1 to 115.7 +/- 4.9 mm Hg on day 1 without concomitant reductions in renal blood flow. Arterial hypertension was sustained and renal vascular resistance increased during the 28 days of servo-controlled norepinephrine infusion despite significant decreases in the daily dose of intrarenal norepinephrine (1.49 +/- 0.23 to 0.47 +/- 0.25 mg/d) necessary to maintain renal blood flow constant. Arterial pressure returned to control values with the cessation of servo-controlled norepinephrine, whereas renal blood flow and renal vascular resistance remained slightly decreased and increased, respectively. Cumulative sodium balance exhibited a net 177 +/- 37 mmol sodium loss over the 28 days of norepinephrine infusion, indicating that the hypertension did not result from sodium retention or expansion of extracellular fluid volume. Intrarenal norepinephrine did not change plasma epinephrine, norepinephrine, or vasopressin concentrations. Atrial natriuretic factor, however, increased at 7 and 14 days of servo-controlled norepinephrine, and plasma renin activity increased on day 14 of norepinephrine infusion. We conclude that low-level elevation of intrarenal adrenergic neurotransmitter produces sustained arterial hypertension that is independent of expansion in extracellular fluid volume, increases in circulating catecholamines or plasma renin activity, or reductions in renal blood flow. This hypertension may be associated with increased renal vascular sensitivity to norepinephrine and/or other renal vasoactive factors.

Lead-contaminated house dust and urban children's blood lead levels.

This study assessed the relationship between lead-contaminated house dust and urban children's blood lead levels. A random-sample survey was used to identify and enroll 205 children, 12 to 31 months of age, who had resided in the same house since at least 6 months of age. Children's blood and household dust, water, soil, and paint were analyzed for lead, and interviews were conducted to ascertain risk factors for elevated blood lead (> or = 10 micrograms/dL). Children's mean blood lead level was 7.7 micrograms/dL. In addition to dust lead loading (micrograms of lead per square foot), independent predictors of children's blood lead were Black race, soil lead levels, ingestion of soil or dirt, lead content and condition of painted surfaces, and water lead levels. For dust lead standards of 5 micrograms/sq ft, 20 micrograms/sq ft, and 40 micrograms/sq ft on noncarpeted floors, the estimated percentages of children having blood lead levels at or above 10 micrograms/dL were 4%, 15%, and 20%, respectively, after adjusting for other significant covariates. Lead-contaminated house dust is a significant contributor to lead intake among urban children who have low-level elevations in blood lead. A substantial proportion of children may have blood lead levels of at least 10 micrograms/dL at dust lead levels considerably lower than current standards.

Pyogenic Liver Abscess Changes in Etiology, Management, and Outcome

Pyogenic liver abscess (PLA) is an important entity with a changing clinical spectrum and may be more prevalent than previously reported. PLA remains most common in older patients, although we found a trend in age range downward. In contrast to earlier reports, PLA affected male and female patients with equal frequency. The most common known cause of PLA remains biliary tract disease, but the majority of patients with PLA were those in whom no underlying cause of PLA could be identified. Single PLA was more common than multiple PLA regardless of etiology. The clinical presentation of patients with PLA ia nonspecific and emphasizes the fact that a high index of suspicion is often required to make the diagnosis. Jaundice and a markedly elevated alkaline phosphatase are clues to the possibility of biliary tract involvement, but may not distinguish patients with liver abscess from those with other hepatic processes. While plain chest and abdominal X-rays were often abnormal and may point to the right upper quadrant as a source of abnormality, ultrasound (US) and abdominal computed tomography (CT) play a central role in this disease. Not only are they often paramount in elucidating the diagnosis of PLA, but US and CT are critical because of their ability to provide other useful information that may address the cause of PLA (that is the biliary tract, and in the case of abdominal CT, other structures). Further, our data suggest that in patients without clinical or imaging evidence of biliary tract disease or pylephlebitis, aggressive random evaluation of the intestinal tract is unwarranted. Percutaneous drainage combined with intravenous antibiotics was the most common therapeutic modality and resulted in cure in 76% of all patients in which it was used (compared to 65% with antibiotics alone and 61% with surgery) and has been successful in 90% of patients over the last 5 years (n = 50). In this study, percutaneous catheter drainage (PCD) appeared to result in a higher cure rate than percutaneous needle aspiration (PNA) but comparative studies are required to further address and determine their relative efficacies. Intravenous antibiotics alone are an important option in carefully selected patients. Surgical intervention as a primary mode of therapy has been almost completely replaced by less invasive approaches such as PCD/PNA, but remains an important consideration in patients who fail these therapies. Although PLA was once considered a fatal disease, the prognosis is now excellent. We have identified a subgroup of patients with no or low-level elevations in bilirubin and alkaline phosphatase and most often single right-sided PLA who do not have a readily identifiable cause of PLA (that is, cryptogenic), as having a particularly favorable prognosis. Death due to PLA is now limited primarily to those patients with severe underlying disease processes, including malignancy.

ORAL DMSA FOR LOW-TO-MODERATE LEAD POISONING IN CHILDREN.

Even low-level blood lead elevations can cause toxicity and neurobehaviorial impairment. This retrospective study adds to a growing literature supporting meso-2,3- dimercaptosuccinic acid (DMSA), a relatively new oral chelator, as a treatment for low to moderate pediatric lead intoxication (25 to 49 micrograms/dl). The authors reviewed …

Relation between sodium intake, renal function, and the regulation of arterial pressure.

The long-term regulation of arterial pressure requires the maintenance of a balance between sodium and water intake and sodium and water excretion. Normal salt and water balance leads to stable body fluid volumes and the maintenance of normal renal function is critical to establishing extracellular fluid volume homeostasis. This review focuses on the role of the kidney in the long-term control of salt and water balance with particular emphasis on the relations between sodium intake, the renin-angiotensin-aldosterone system, renal sympathetic nerve activity, and the regulation of arterial pressure via renal sodium and water excretion. The accumulation of evidence in recent years demonstrates that low level elevation of renin release, circulating angiotensin II or aldosterone, or activation of renal sympathetic outflow may alter renal function such that normal natriuretic and diuretic responses to arterial pressure are significantly impeded. Under these circumstances, the maintenance of normal sodium and water excretion requires a significant elevation of arterial pressure. Thus, compromised renal function leads to elevation of arterial pressure to maintain adequate sodium and water balance during periods of increased sodium intake. The resultant chronic elevation of arterial pressure then becomes a compromise that is used by the kidneys to maintain normal extracellular body fluid volumes.

House and hand dust as a potential source of childhood lead exposure.

Blood lead sampling has demonstrated an almost universal low-level elevation in inner-city children. The ingestion of lead paint chips is questioned as the main source of this exposure. Dust containing lead was found on the hands of inner-city children and interior household surfaces in substantially larger amounts than in similar suburban settings. It is possible that children may ingest this lead through typically frequent mouthing activity.