Site and mechanism of action of diuretics

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

Methods for Reducing Contrast Use and Avoiding Acute Kidney Injury During Endovascular Procedures

Iodinated Contrast Media (CM) has a plethora of applications in routine non-invasive or percutaneous invasive imaging examinations and therapeutic interventions. Unfortunately, the use of CM is not without complications, with contrast-induced acute kidney injury (CI-AKI) being among the most severe. CI-AKI is a syndrome defined as a rapid development of renal impairment after a few days of CM endovascular injection, without the presence of any other underlying related pathologies. Although mostly transient and reversible, for a subgroup of patients with comorbidities related to renal failure, CI-AKI is directly leading to longer hospitalization, elevated rates of morbidity and mortality, as well as the increased cost of funding. Thus, a need for classification in accordance with clinical and peri-procedural criteria is emerged. This would be very useful for CI-AKI patients in order to predict the ones who would have the greatest advantage from the application of preventive strategies. This article provides a practical review of the recent evidence concerning CI-AKI incidence, diagnosis, and sheds light on prevention methods for reducing contrast use and avoiding AKI during endovascular procedures. In conclusion, despite the lack of a specific treatment protocol, cautious screening, assessment, identification of the high-risk patients, and thus the application of simple interventions -concerning modifiable risk factors- can significantly reduce CI-AKI risk.

Challenges of lymphoedema management in an ageing population

The risk of developing chronic oedema increases with age. Many factors affect the successful management of this condition, which a robust holistic assessment will identify. This article discusses some of the challenges and complications associated with managing this long-term condition, alongside comorbidities and the effects of ageing. It will consider the implications of wider issues such as social care and the current healthcare economy. The challenges of lymphoedema management can be overcome by offering a collaborative approach to care. This can be achieved by specialist practitioners offering support, advice and guidance on how to ensure satisfactory outcomes for patients in a timely manner.

Toxicological evaluation of the aqueous extract of Acalypha wilkesiana in Wistar albino rats

BACKGROUND

Acalypha wilkesiana (Euphorbiaceae) is highly accepted for traditional treatment of human plasmodiasis in Africa.

METHODS

The toxicological effects of the aqueous leaf extract of A. wilkesiana were studied in 45 male and female Wistar albino rats. An acute toxicity testing was done using 21 rats divided into seven groups and LD50 determined. In the sub-chronic toxicity study, the extract was administered orally over a period of 28 days to rats in three groups with doses of 400 mg kg-1, 800 mg kg-1 and 1,600 mg kg-1, respectively, and the fourth group administered with water served as control. Blood samples were collected for hematological and serum biochemical analysis; organs of the animals were harvested for histopathological examination.

RESULTS

The acute toxicity testing showed that the extract was non-toxic at doses up to 3,000 mg kg-1 and the LD50 was calculated to be 2,828.34 mg kg-1. The study showed that at 1,600 mg kg-1 dose, the extract caused a decrease in the level of neutrophils (NEUT) while lymphocytes (LYMP) were statistically significantly increased. The administration of the extract also resulted in varying significant dose dependent increase in the levels of aspartate amino transferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP). There were also significant increases in the level of total protein (TP), urea (URN) and albumin (GLB) especially at 1,600 mg kg-1 dosage. Histopathology showed that the extract caused mild to severe significant lesions that are dose dependent in the liver and kidney when compared with the control group.

CONCLUSIONS

Prolonged administration of high dose of A. wilkesiana extract has tendency to cause organ toxicity.

Chronic diuretic therapy attenuates renal BOLD magnetic resonance response to an acute furosemide stimulus

BACKGROUND

Blood Oxygen Level Dependent (BOLD) magnetic resonance (MR) is a novel imaging tool that detects changes in tissue oxygenation. Increases in renal oxygenation in response to a standard 20 mg intravenous furosemide stimulus have been evaluated to assess kidney viability in patients with renal artery stenosis (RAS). The effect of prior exposure to furosemide on the ability of BOLD MR techniques to evaluate renal function is unknown.This study tested the hypothesis that chronic loop diuretic therapy is associated with attenuated responses in renal tissue oxygenation as measured by BOLD MR with an acute 20 mg intravenous furosemide stimulus in participants undergoing evaluation for RAS.

METHODS

Thirty-eight participants referred for evaluation of RAS were recruited for this study. We examined renal cortical and medullary BOLD signal (T2*) intensities before and after a 20 mg intravenous furosemide stimulus. Additionally, we measured changes in renal artery blood flow using phase contrast techniques.

RESULTS

After controlling for covariates age, race, gender, diabetes, glomerular filtration rate, body mass index, and stenosis severity, daily oral furosemide dose was an independent, negative predictor of renal medullary T2* response (p=0.01) to a standard 20 mg intravenous furosemide stimulus. Stenosis severity and ethnicity were also significant independent predictors of changes in T2* signal intensity in response to an acute furosemide challenge. Changes in renal blood flow in response to acute furosemide administration were correlated with changes in T2* in the renal cortex (r=0.29, p=0.03) but not the medulla suggesting changes in renal medullary oxygenation were not due to reduced renal medullary blood flow.

CONCLUSIONS

Chronic furosemide therapy attenuates BOLD MR responses to an acute furosemide stimulus in patients with RAS being evaluated for renal artery revascularization procedures. Thus, patients who are chronically administered loop diuretics may need a different dosing strategy to accurately detect changes in renal oxygenation with BOLD MR in response to a furosemide stimulus.

gamma-Tocopherol Accelerated Sodium Excretion in a Dose-Dependent Manner in Rats with a High Sodium Intake

We have previously reported that γ-tocopherol (γ-Toc) displays a natriuretic potency in rats fed a NaCl diet and administered 20 mg γ-Toc. In this study, we investigated whether γ-Toc has natriuretic potency at a dose lower or higher than 20 mg in rats given a NaCl diet. Male rats were fed a control diet or a NaCl diet and administered either placebo or 10, 20 or 40 mg of γ-Toc. The rat urine was collected for 24 hours (divided into 6 hour periods) and the 2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman (γ-CEHC) level, the sodium excretion content, and the urine volume were determined. The 24-hour γ-CEHC and sodium levels in the urine of the NaCl groups given 20 mg or 40 mg γ-Toc were significantly higher than those in the placebo group. The peak levels of urine sodium and γ-CEHC in the NaCl group given 40 mg γ-Toc appeared at 0–6 h, which was a more rapid increase than that seen in the group given 20 mg γ-Toc. The 24-hour urine volumes of the NaCl groups given 10 and 20 mg γ-Toc were significantly higher than the urine volume of the placebo group. Our findings suggested that γ-Toc increased sodium excretion in a dose-dependent manner in rats fed a NaCl diet. Moreover, a high dose of γ-Toc may accelerate its metabolism and cause an increase in the rate of sodium excretion.

[Spanish Society of Cardiology practice guidelines on arterial hypertension]

High blood pressure is a well-known cardiovascular risk factor that is responsible for an elevated morbidity and mortality. However, although efficacious drugs for treatment and numerous and updated scientific training programs are available, the reality is that only a low percentage of patients are followed up in accordance with the rates which are presently considered normal. The purpose of these guidelines is to provide medical guidance for the prevention, detection and evaluation of hypertension, and to provide the best diagnosis and treatment. The factors involved in cardiovascular complications in the hypertensive patient are multiple. That is why this report places more emphasis in the individual cardiovascular risk stratification as part of the treatment strategy. The information obtained in the most recent studies published confirms the interest in achieving the greatest decrease in rates of blood pressure. This treatment to lower levels is especially useful in the high-risk subgroup. It maintains the necessity of nonpharmacological measures or lifestyle modifications in all patients with high blood pressure who either need or do not need drug therapy. All pharmacological groups may be used, but it is appropriate to choose the specific antihypertensive agent adapted to the clinical and individual situation with the use of low doses of drugs to initiate therapy and the use of appropriate drug combinations.

Diuretics and transmembrane ionic exchanges: structure-activity relations and clinical applications

The study of membrane ion transport has facilitated the discovery of potent and quite specific inhibitory drugs. Some of these compounds are therapeutic agents acting on basic transport mechanisms as in the case of the cardiac glycosides on the myocardial sodium ion (Na+), potassium ion (K+) pump, and the loop diuretics on the renal Na+, K+, chloride (Cl-) co-transport system. The development of inhibitors for other transport systems such as Na+/hydrogen ion (H+), Na+/calcium ion (Ca2+) and bicarbonate (HCO3-)/Cl- exchangers requires the screening of a large number of molecules. For several reasons, the human red blood cell is one of the best models for screening the effect of drugs on ion transport mechanisms. The use of human red cells for pharmacologic studies of ion transport has increased the understanding of the structure-activity relations of diuretics. For instance, loop diuretics that are chemically neutral were considered for many years as drugs that act similarly to classic acid loop diuretics. They are now considered as potent inhibitors of HCO3-/Cl- anion exchange. A brief summary of the more recent results is given together with the perspectives of new fundamental and therapeutic applications of these compounds.

Critical care cardiology

Management of the critical care cardiology patient often requires a rapid, accurate diagnostic and therapeutic strategy. A wide range of cardiovascular drugs is available for treatment of shock, congestive heart failure, and arrhythmias.