Patients' representations of their end-stage renal disease: relation with mortality.

BACKGROUND: Self-regulation theory explains how patients' illness perceptions influence self-management behaviour (e.g. via adherence to treatment). Following these assumptions, we explored whether illness perceptions of ESRD-patients are related to mortality rates. METHODS: Illness perceptions of 182 patients participating in the NECOSAD-2 study in the period between December 2004 and June 2005 were assessed. Cox proportional hazard models were used to estimate whether subsequent all-cause mortality could be attributed to illness perception dimensions. RESULTS: One-third of the participants had died at the end of the follow-up. Mortality rates were higher among patients who believed that their treatment was less effective in controlling their disease (perceived treatment control; RR = 0.71, P = 0.028). This effect remained stable after adjusting for sociodemographic and clinical variables (RR = 0.65, P = 0.015). CONCLUSIONS: If we consider risk factors for mortality, we tend to rely on clinical parameters rather than on patients' representations of their illness. Nevertheless, results from the current exploration may suggest that addressing patients' personal beliefs regarding the effectiveness of treatment can provide a powerful tool for predicting and perhaps even enhancing survival.

Acute effects of hemodialysis on salivary flow rate and composition.

AIMS: To evaluate acute effects of hemodialysis (HD) on the salivary flow rate, pH and biochemical composition before, during and after completion of a dialysis session. MATERIAL AND METHODS: Unstimulated whole saliva (UWS) and chewing-stimulated whole saliva (CH-SWS) were collected in 94 HD patients. Salivary flow rate, pH, concentrations of total protein, albumin, cystatin C, secretory immunoglobulin A (S-IgA) and of sodium, potassium and urea were measured. RESULTS: HD had an acute stimulating effect on the salivary flow rate (UWSbefore = 0.30+/-0.22 ml/min, UWSduring = 0.39+/-0.25 ml/min, p < 0.005). The mean pH of UWS showed a small but significant increase during HD mainly due to an increased watery secretion from the salivary glands. The salivary biochemical constituents changed markedly, but no significant difference in output was found. The electrolyte concentration did not change significantly during dialysis. The level of urea in CH-SWS declined to 40% (Ureabefore = 25.+/-6.4 mmol/l, Ureaduring = 15.3+/-4.5 mmol/1). CONCLUSIONS: This study shows that HD has significant acute effects on both salivary secretion rate and protein concentrations in saliva. We conclude that the observed changes in salivary concentrations and proteins are mainly due to an increased watery secretion from the salivary glands.

Long term health complaints following the Amsterdam Air Disaster in police officers and fire-fighters.

BACKGROUND: On 4 October 1992, a cargo aircraft crashed into apartment buildings in Amsterdam, the Netherlands. Fire-fighters and police officers assisted with the rescue work. OBJECTIVES: To examine the long term health complaints in rescue workers exposed to a disaster. METHODS: A historical cohort study was performed among police officers (n = 834) and fire-fighters (n = 334) who performed at least one disaster related task and reference groups of their non-exposed colleagues (n = 634 and n = 194, respectively). The main outcome measures included digestive, cardiovascular, musculoskeletal, nervous system, airway, skin, post-traumatic stress, fatigue, and general mental health complaints; haematological and biochemical laboratory values; and urinalysis outcomes. RESULTS: Police officers and fire-fighters who were professionally exposed to a disaster reported more physical and mental health complaints, compared to the reference groups. No clinically relevant statistically significant differences in laboratory outcomes were found. CONCLUSIONS: This study is the first to examine long term health complaints in a large sample of rescue workers exposed to a disaster in comparison to reference groups of non-exposed colleagues. Findings show that even in the long term, and in the absence of laboratory abnormalities, rescue workers report more health complaints.

Glycyrrhizic acid: the assessment of a no effect level.

Because from earlier experiments in rats and a pilot study in humans a no-effect level of glycyrrhizic acid could not be established, a second experiment was performed in healthy volunteers. The experiment was performed in females only, because the effects were most marked in females in the pilot study. Doses of 0, 1, 2 and 4 mg glycyrrhizic acid/kg body weight were administered orally for 8 weeks to 39 healthy female volunteers aged 19-40 years. The experiment lasted 12 weeks including an adaptation and a "wash-out" period. A no-effect level of 2 mg/kg is proposed from the results of this study, from which an acceptable daily intake (ADI) of 0.2 mg/kg body weight can be extrapolated with a safety factor of 10. This means consumption of 12 mg glycyrrhizic acid/day for a person with a body weight of 60 kg. This would be equal to 6 g licorice a day, assuming that licorice contains 0.2% of glycyrrhizic acid. The proposed ADI is below the limit advised by the Dutch Nutrition Council of 200 mg glycyrrhizic acid/day. This reflects the relatively mild acute toxicity of glycyrrhizic acid, which is also emphasised by the "generally recognised as safe" (GRAS) status of glycyrrhizic acid in the USA in 1983. However, the long-term effects of a mild chronic intoxication (causing, for example, a mild hypertension), although not immediately lethal, justify special attention to the amount of glycyrrhizic acid used daily.

L-arginine does not prevent the renal effects of endothelin in humans.

The infusion of endothelin to obtain plasma levels as present in sodium-retaining conditions such as heart failure and hepatorenal syndrome has been shown to cause sodium retention and renal vasoconstriction. Whether these renal effects of endothelin could be modulated by the stimulation of nitric oxide production by the infusion of L-arginine was examined. Therefore, the renal and endocrine effects of the systemic administration of endothelin (2.5 ng/kg per minute for 90 min), L-arginine (5 mg/kg per minute for 90 min), or the combination of endothelin and L-arginine were studied in healthy subjects under clearance conditions. During endothelin infusion, plasma endothelin levels rose from 3.0 +/- 0.2 to 14.1 +/- 2.4 pmol/L (P < 0.01). Mean arterial pressure increased by 7 mm Hg (P < 0.01). The effects on renal function were disproportionately large: renal vascular resistance increased from 77.5 +/- 3.2 to 124.1 +/- 6.7 mm Hg/min per liter (P < 0.01), and sodium excretion fell from 178 +/- 30 to 83 +/- 11 mumol/min (P < 0.01). Endothelin had no effect on urinary nitrite excretion. L-Arginine caused a fall in blood pressure of 5 mm Hg (P < 0.01) and decreased renal vascular resistance by 12% (P < 0.05). Sodium excretion increased twofold. This was associated with an increase in urinary nitrite excretion from 112 +/- 36 to 465 +/- 190 nmol/min (P < 0.01), suggesting stimulation of renal nitric oxide production. During the combination of endothelin and L-arginine, urinary nitrite excretion increased similarly.(ABSTRACT TRUNCATED AT 250 WORDS)

Natriuretic and hypotensive effect of adenosine-1 blockade in essential hypertension.

We studied the effects of a single dose (100 mg orally) and repeated administration (100 mg o.d. for 7 days) of FK453, a novel adenosine-1 receptor antagonist, on renal sodium handling and blood pressure in eight patients with essential hypertension. Within 60 minutes after administration of FK453, sodium excretion increased threefold. This occurred in the absence of a change in renal hemodynamics, assessed from inulin and para-aminohippurate clearance, and was accompanied by increased fractional excretion of lithium, phosphate, and uric acid and by increased excretion of calcium and magnesium. Maximal free water clearance data showed an increase in maximal urine flow and distal delivery term and a decrease in the diluting segment reabsorption term. FK453 also decreased blood pressure and increased heart rate, but this did not occur until about 3 hours after ingestion, that is, when the natriuresis was already over. The natriuretic effect of FK453 was short-lasting, and continued use of FK453 was in fact accompanied by some net sodium retention. Blood pressure on the seventh day before FK453 treatment was not different from blood pressure before administration of the first dose of FK453. Again an acute natriuretic response followed, although less than after the first dose. Changes in intrarenal sodium handling parameters, blood pressure, and heart rate were similar to those seen after the first dose. The natriuretic and hypotensive effects of FK453 indicate that adenosine-1 receptor activity plays a role in the regulation of blood pressure and renal sodium handling in patients with essential hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Indomethacin- and desamino-8-D-arginine vasopressin-induced lithium reabsorption is not amiloride sensitive in humans.

This study was undertaken to analyze whether the mechanism of decreased fractional lithium excretion (FELi) induced in humans by the prostaglandin synthesis inhibitor indomethacin and the vasopressin analog desamino-8-D-arginine vasopressin (d-DAVP) is amiloride inhibitable. Eight sodium-restricted (10 mmol/day) healthy volunteers underwent clearance studies to evaluate the effects of indomethacin (50 mg tid for 6 days), amiloride (10 mg twice before the clearance study) and d-DAVP (4 micrograms, i.v.), and combinations of these drugs. Despite the sodium restriction, amiloride had no effect on FELi, although the dosage was sufficient to cause a 6-fold increase in sodium excretion, and potassium retention. Compared to a base-line value of 27.9 +/- 2.1%, FELi fell to 20.7 +/- 2.1% after indomethacin (P < .01) and to 22.4 +/- 1.5% after d-DAVP (P < .01). When d-DAVP was administered during indomethacin, the FELi fell to 18.0 +/- 1.4%. Compared to indomethacin alone, this represented no significant further change. Amiloride did not prevent the fall in FELi caused by indomethacin or d-DAVP or both. These data indicate that in humans, 1) sodium restriction does not cause amiloride-sensitive lithium reabsorption, and 2) the lithium reabsorption caused by d-DAVP and indomethacin is not amiloride sensitive.

Iso-oncotic volume expansion in the nephrotic syndrome.

1. In previous studies we found that albumin infusions caused only a modest natriuresis in the nephrotic syndrome, suggesting that hypovolaemia played no part in the sodium retention of these patients. However, this finding was inconclusive, since the hyperoncocity of the infused albumin probably opposed sodium excretion. 2. In the present study, we examined the effect of sustained (68 h) plasma volume expansion (+18%), by means of iso-oncotic albumin infusions, on renal function, blood pressure, humoral factors and sodium balance. 3. Plasma atrial natriuretic peptide levels increased almost threefold and renin-angiotensin system activity was suppressed. Glomerular filtration rate remained unchanged, whereas estimated renal plasma flow increased, resulting in a further decrease in filtration fraction. 4. The increase in plasma volume expansion was accompanied by a modest increase in sodium excretion, which, however, was less than the amount of sodium daily infused with the albumin solutions and consumed with the diet, so that net sodium was retained. 5. This observation supports the concept that an intrinsic renal defect causes the sodium retention in the nephrotic syndrome, and argues against the therapeutic use of albumin infusions.

Natriuretic and kaliuretic response to potassium load: modulation by sodium intake.

Potassium (K) loading is followed by a rapid increase in sodium (Na) and K excretion. To evaluate the influence of Na intake on this effect, we studied the acute natriuretic and kaliuretic response to a single oral K load (100 mmol) in six healthy volunteers equilibrated on a 10-, 100-, and 400-mmol Na intake. Compared to the 100-mmol Na intake, the 400-mmol Na intake greatly enhanced the natriuretic effect of the K load; during the 10-mmol Na intake no natriuresis but even some Na retention occurred. The kaliuretic effect was not significantly changed and occurred at similar values of plasma K. Plasma aldosterone was suppressed during the 400-mmol Na diet and stimulated during the 10-mmol Na diet, but the relative increments after the KCl load did not differ among the three diets. In conclusion, whereas the effect of a K load on kaliuresis is relatively independent of Na intake, its effect on Na excretion varies from marked natriuresis to slight Na retention. The Na retention is probably due to acute K-induced aldosterone stimulation, and the natriuresis to K-induced increase in distal Na delivery not utilized to promote K excretion. Apparently, the integration of renal Na and K handling after a K load is such that K balance is maintained at the cost of Na balance.

Insulin increases sodium reabsorption in diluting segment in humans: evidence for indirect mediation through hypokalemia.

To examine the mechanism of renal sodium (Na) and potassium (K) retention during insulin infusion, seven healthy volunteers underwent clearance studies without (time control) and with insulin infusion (40 mU bolus, followed by 1 mU/kg/min for 150 min). Maximal free water clearance and fractional lithium clearance (FELi) were used to analyze renal sodium handling. Insulin decreased Na excretion (from 189 +/- 25 to 121 +/- 19 mumol/min, P less than 0.01) and K excretion (from 64 +/- 8 to 19 +/- 1 mumol/min, P less than 0.01), but did not change in glomerular filtration rate. FELi increased from 29.8 +/- 1.9 to 32.3 +/- 1.9% (P less than 0.05), minimal urine osmolality decreased from 59 +/- 3 to 46 +/- 3 mOsm/kg (P less than 0.01), and the diluting segment reabsorption index increased from 88.0 +/- 0.9 to 93.7 +/- 0.9%, P less than 0.01). Insulin also decreased plasma K, from 3.91 +/- 0.08 to 3.28 +/- 0.08 mmol/liter, P less than 0.01. In a third clearance study KCl was infused simultaneously (3.75 mumol/kg/min) to prevent this fall in plasma K. In this study insulin had no effect on Na and K excretion and diluting segment reabsorption, but the rise in FELi remained. In a fourth clearance study NaCl (3.75 mumol/kg/min) instead of KCl was infused together with insulin. This maneuver did not prevent the Na and K retaining effect of insulin, nor any of its effects on renal sodium handling parameters. These data suggest that Na and K retention during insulin infusion are largely secondary to hypokalemia, which causes increased reabsorption in the diluting segment.

Sodium retention by insulin may depend on decreased plasma potassium.

Evidence is accumulating that insulin is a hypertensive factor in humans. The involved mechanism may be its sodium-retaining effect. We examined whether insulin causes sodium retention through a direct action on the kidney, as is generally assumed, or indirectly through hypokalemia. Insulin was infused (euglycemic clamp technique) with and without potassium infusion to prevent hypokalemia in six healthy subjects. Without potassium infusion, insulin caused a marked decrease in plasma potassium (-0.75 mmol/L), and decreased urinary sodium and potassium excretions by, approximately 38% and 65%, respectively. Simultaneous potassium infusion largely prevented the decrease in plasma potassium, as well as the decrease in urinary sodium and potassium excretions. These data suggest that the acute antinatriuretic effect of insulin may be largely mediated in an indirect way, ie, through hypokalemia.

Effects of nitrendipine on sodium balance during changes in sodium intake and low-dosage ANP.

We found previously that calcium entry blockade with nitrendipine enhanced the natriuretic effect of high-dose atrial natriuretic peptide (ANP). It is unknown whether nitrendipine also influences the effect of physiological changes in ANP. We therefore studied the effect of nitrendipine on cumulative sodium balance during changes in sodium intake as well as on natriuresis after low-dosage ANP infusion during low and high sodium (LS and HS, respectively) intake. In eight healthy volunteers, sodium balance was recorded after the switch from LS (20 mmol/day) to HS (300 mmol/day) diet. Cumulative sodium balance was equal with (441 +/- 45 mmol) or without (458 +/- 45 mmol) nitrendipine treatment. The body weight curves were also fully congruent. ANP (0.005 micrograms/kg/min for 3 h) was administered during maximal water diuresis on both sodium intake levels with and without nitrendipine. Infusion of ANP increased sodium excretion (mumol/min) from 30 +/- 7 to 81 +/- 12 (LS) and from 316 +/- 27 to 469 +/- 46 (HS). During nitrendipine, similar increments (from 36 +/- 7 to 98 +/- 24 mumol/min, HS) were found. ANP had no effect on inulin clearance and fractional excretion of lithium, but consistently depressed diluting segment reabsorption. This pattern was also similar during nitrendipine. Apparently, under the conditions of this study in normal subjects, nitrendipine has no effect on sodium balance. ANP, in physiological concentrations, increases natriuresis mainly by depressing sodium reabsorption in the distal nephron, an effect not enhanced by nitrendipine.

Renal actions of theophylline and atrial natriuretic peptide in humans: a comparison by means of clearance studies.

The hypothesis that the methylxanthine theophylline and atrial natriuretic peptide (ANP) have similar actions in the kidney was tested. Doses of equal natriuretic potency were administered to seven healthy men during maximal water diuresis. Theophylline (1.2 mg/kg/min) increased sodium excretion to 3-fold, increased glomerular filtration rate and filtration fraction and had no effect on estimated renal plasma flow. Increments were also found in maximal urine flow, distal delivery index and fractional lithium clearance. Diluting segment reabsorption index decreased, and minimal urine osmolality increased. ANP, of which the dose was low (0.01 micrograms/kg/min), had similar effects on sodium excretion, glomerular filtration rate, filtration fraction, minimal urine osmolality and diluting segment reabsorption index, but it decreased estimated renal plasma flow and had no effect on distal delivery and fractional lithium clearance. In a third clearance study ANP was infused after 3 days of treatment with theophylline. The only difference observed was that theophylline prevented the ANP-induced fall in estimated renal plasma flow. Theophylline did not enhance the natriuretic effect of ANP nor its effect to stimulate urinary cyclic guanosine monophosphate. Pretreatment with theophylline had raised plasma renin activity, but the effect of ANP to lower plasma renin activity was not diminished. Our observations agree with the idea that theophylline and ANP act via common mechanisms in the kidney. However, ANP effects are independent of theophylline's action.

Effects of atrial natriuretic peptide on distal tubule function in humans.

To characterize the actions of atrial natriuretic peptide (ANP) in the human distal nephron, we studied interactions between ANP (0.02 micrograms/kg.min i.v.) and acutely administered substances acting in the distal nephron, that is, amiloride and aldosterone, in six healthy humans during maximal water diuresis. ANP increased NaCl excretion, fractional lithium excretion (FELi) and decreased diluting segment reabsorption estimated from free water clearance. Amiloride increased natriuresis, had no effect on FELi, but decreased diluting segment reabsorption. Aldosterone had the opposite effect. When infused in addition to amiloride, ANP still increased NaCl excretion, the changes in sodium handling parameters being comparable to those seen after ANP alone. Amiloride did not increase the further natriuretic response to ANP. These findings suggest that ANP increases distal sodium delivery, and decreases sodium reabsorption in distal segments by a mechanism also sensitive to amiloride. ANP abolished much of the antinatriuretic effect of aldosterone, which may also be explained by assuming a partial overlap of the target segments of ANP and aldosterone in the distal nephron. Remarkably, in neither of these experiments was the natriuresis after ANP accompanied by a kaliuresis, for which the explanation remains obscure.