Role of the renin-angiotensin-aldosterone system for control of arterial blood pressure following moderate deficit in total body sodium: Balance studies in freely moving dogs

Association of Serum Osmolarity With Contrast-Induced Nephropathy in Patients With ST-Segment Elevation Myocardial Infarction

Contrast-induced nephropathy (CIN) is a prevalent and serious complication after primary percutaneous coronary intervention (pPCI). Although the association between serum osmolarity and chronic kidney disease is well established, its relation to CIN in patients with ST-segment elevation myocardial infarction (STEMI) undergoing pPCI needs to be elucidated. We evaluated the predictive value of serum osmolarity for CIN development in patients with STEMI (n = 768) undergoing pPCI. Serum osmolarity on admission was calculated. The study population was divided into 2 groups according to CIN development, and both groups were compared according to clinical, laboratory, and demographic features, including the serum osmolarity. Serum osmolarity was significantly higher in patients with CIN than in those without CIN (278 [8] vs 284 [9]; P = .024). Serum osmolarity (odds ratio: 1.052; 95% confidence interval: 1.018-1.086; P = .002), hemoglobin, contrast media volume, creatinine on admission, basal SYNergy between PCI with TAXus and cardiac surgery II score, and left ventricular ejection fraction were found to be independent predictors of CIN. Serum osmolarity (given the simple calculation of this parameter on admission) can be useful to define patients with STEMI undergoing pPCI who are more likely to develop CIN.

Predicting Contrast-induced Renal Complications in the Catheterization Laboratory

Risk scores should undergo 3 analytical phases before they are suitable for adoption in clinical practice, namely, derivation, external validation, and assessment of effect on clinical outcomes of use of the risk score in a so-called impact study. Major risk factors for renal complications after percutaneous coronary intervention are pre-existing chronic kidney disease, diabetes mellitus, use of a high contrast dose, and hemodynamic instability. Unfortunately, only 3 of these 10 risk scores have undergone external validation. As a result, there is a great need for further research on the already designed risk scores.

Contrast media viscosity versus osmolality in kidney injury: lessons from animal studies

Iodinated contrast media (CM) can induce acute kidney injury (AKI). CM share common iodine-related cytotoxic features but differ considerably with regard to osmolality and viscosity. Meta-analyses of clinical trials generally failed to reveal renal safety differences of modern CM with regard to these physicochemical properties. While most trials' reliance on serum creatinine as outcome measure contributes to this lack of clinical evidence, it largely relies on the nature of prospective clinical trials: effective prophylaxis by ample hydration must be employed. In everyday life, patients are often not well hydrated; here we lack clinical data. However, preclinical studies that directly measured glomerular filtration rate, intrarenal perfusion and oxygenation, and various markers of AKI have shown that the viscosity of CM is of vast importance. In the renal tubules, CM become enriched, as water is reabsorbed, but CM are not. In consequence, tubular fluid viscosity increases exponentially. This hinders glomerular filtration and tubular flow and, thereby, prolongs intrarenal retention of cytotoxic CM. Renal cells become injured, which triggers hypoperfusion and hypoxia, finally leading to AKI. Comparisons between modern CM reveal that moderately elevated osmolality has a renoprotective effect, in particular, in the dehydrated state, because it prevents excessive tubular fluid viscosity.

Association of NT-proBNP with plasma renin activity and plasma aldosterone concentration in women with singleton pregnancy

OBJECTIVE

To determine the association of the N-terminal fragment of precursor protein brain-type natriuretic peptide (NT-proBNP) levels with plasma renin activity (PRA) and plasma aldosterone concentration (PAC) in singleton pregnancies.

DESIGN

Serum NT-proBNP levels, PRA and PAC were determined in 215 blood specimens from 139 women with singleton pregnancies, including 34 and 105 women who did and did not develop hypertensive disorders in pregnancy, respectively. Twenty-five blood specimens were obtained from 25 women who later developed hypertension (systolic BP⩾140mmHg and/or diastolic BP⩾90mmHg), but were normotensive at the time of blood sampling.

RESULTS

The serum NT-proBNP levels [pg/ml, median (range), 32 (5-142)] did not change in normotensive women, but increased significantly to 97 (23-436) after the development of hypertension (D/H). The PRA [ng/ml/h, median (range), 7.1 (1-20)] did not change in normotensive women, but decreased significantly to 1.9 (1-16) after D/H. PAC (pg/ml) increased significantly from 397 (94-1750) to 667 (123-2010) between the 2nd and 3rd trimesters in normotensive women. However, as PAC of hypertensive women did not change significantly before and after D/H, PAC [293 (116-1720)] after D/H was significantly lower than that [667 (123-2010)] of the 3rd trimester in the normotensive women. The serum levels of NT-proBNP were significantly and negatively correlated with both PRA and PAC.

CONCLUSIONS

The renin-angiotensin-aldosterone system is suppressed in pregnant women with cardiac conditions associated with higher NT-proBNP levels.

Neuroendocrine changes and natriuresis in response to social stress in rats

Sympathetic activation is detected by the tachycardic, hypertensive and hyperthermic responses during social conflicts in rodents and primates. Sympathetic nervous system activation promoting sodium retention has long been recognized to play a significant role in the development and maintenance of salt-sensitive hypertension. The objective was to investigate neuroendocrine activation and renal sodium excretion in response to chronic social stress. Male Wistar rats were subjected to social stress in accordance with the resident-intruder paradigm. Intruder rats were subjected to social confrontation once daily for 6 days. After the last confrontation, plasma corticosterone and urinary catecholamines were determined to assess the neuroendocrine activation. Plasma aldosterone, plasma and urinary creatinine, Na(+) , K(+) and urinary volume were also measured. Chronic social stress increased the urinary norepinephrine, dopamine and plasma corticosterone levels, with no changes in epinephrine levels. On the other hand, high plasma aldosterone levels and low urinary sodium excretion without differences in creatinine clearance were observed. In conclusion, social stress had a strong antinatriuretic effect, which is coincident with noradrenergic and corticoadrenal activation and an increase in plasma aldosterone levels. Activation of these factors may promote sodium retention, which has long been recognized to play a significant role in the development and maintenance of hypertension.

Contrast-induced kidney injury: mechanisms, risk factors, and prevention

In general, iodinated contrast media (CM) are tolerated well, and CM use is steadily increasing. Acute kidney injury is the leading life-threatening side effect of CM. Here, we highlight endpoints used to assess CM-induced acute kidney injury (CIAKI), CM types, risk factors, and CIAKI prevention. Moreover, we put forward a unifying theory as to how CIAKI comes about; the kidney medulla's unique hyperosmolar environment concentrates CM in the tubules and vasculature. Highly concentrated CM in the tubules and vessels increases fluid viscosity. Thus, flow through medullary tubules and vessels decreases. Reducing the flow rate will increase the contact time of cytotoxic CM with the tubular epithelial cells and vascular endothelium, and thereby damage cells and generate oxygen radicals. As a result, medullary vasoconstriction takes place, causing hypoxia. Moreover, the glomerular filtration rate declines due to congestion of highly viscous tubular fluid. Effective prevention aims at reducing the medullary concentration of CM, thereby diminishing fluid viscosity. This is achieved by generous hydration using isotonic electrolyte solutions. Even forced diuresis may prove efficient if accompanied by adequate volume supplementation. Limiting the CM dose is the most effective measure to diminish fluid viscosity and to reduce cytotoxic effects.