Comparative Doppler flow measurements of the ulnar artery and of the postanastomotic radial artery in radiocephalic arteriovenous fistulas to detect steal syndromes.

OBJECTIVE: This study aims to assess whether a comparison of the Doppler flow measurements of the ulnar artery and of the postanastomotic radial artery can help detect steal syndromes at the level of native dialysis fistulas of the wrist. PATIENTS AND METHODS: We have prospectively analyzed 35 distal radiocephalic arteriovenous fistulas presenting with postanastomotic radial artery Doppler inversion of flow. The flows of the ulnar artery and of the postanastomotic radial artery have been measured and compared. Subsequent clinical examination to detect any sign of ischemia at the hand level was performed and the results of medical imaging were confronted with the clinical data. RESULTS: A steal syndrome was discovered in a total of 6 patients (17%), 4 patients out of 23 displaying an ulnar flow lower than the postanastomotic radial one and 2 patients among 12 with an ulnar flow higher than the radial one. Sensitivity, specificity, positive predictive value and negative predictive value of the test were 67%, 34%, 17% and 83%, respectively. Paradoxically, the mean intensity of ulnar flow deficiency has been measured at 40% among true positive patients and at 70% among false positive ones. We have not been able to identify any difference, be it in terms of systolic upstroke time, maximum systolic speed, telediastolic speed or in terms of global architecture of the curves between the Doppler waveforms of 4 true positive and 4 false positive patients. CONCLUSION: The comparative Doppler study of the flows of the ulnar and postanastomotic radial arteries does not enable us to detect steal syndromes at the level of wrist dialysis fistulas. Hence we consider that a systematic study of the postanastomotic radial artery flow, during routine Doppler examination of distal dialysis fistulas, proves superfluous.

Dialysis arteriovenous fistulas: the critical role of color doppler ultrasound.

Despite being time-consuming and observer-dependent, CDUS is a method of choice for performing and controlling dialysis shunts. It contributes to increasing the number of native AVFs and enables early detection of lesions therefore allowing quick percutaneous or surgical therapy.

Evidence that chronicity of hyponatremia contributes to the high urate clearance observed in the syndrome of inappropriate antidiuretic hormone secretion.

The high fractional excretion (FE) of uric acid observed in hyponatremia associated with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is commonly attributed to the volume-expanded state, although volume expansion in normonatremic volunteers is unable to increase urate clearance to a degree similar to that in SIADH. The goal of the present study is to analyze whether hyponatremia by itself could influence the FE of uric acid, as well as the effects of intravascular volume and glomerular filtration rate on FE of uric acid in SIADH. This study examines the effects of a 2-L infusion of isotonic saline over 24 hours on FE of uric acid in 9 normonatremic volunteers and 17 hyponatremic patients with SIADH. We also studied the FE of uric acid in 6 patients with SIADH with only mild water retention and the urate and creatinine clearances in 18 hyponatremic patients with SIADH before and after normalization of serum sodium levels by water restriction. When infusing 2 L of isotonic saline over 24 hours in healthy subjects, there was a decrease in plasma protein concentration of 8%, suggesting a similar degree of volume expansion than in patients with SIADH. The FE of uric acid did not increase to the same extent (9% +/- 1.5% versus 17% +/- 1.5%; P: < 0.01). Conversely, in 6 hyponatremic patients with mild water retention (1 L), the FE of uric acid was still high despite indirect signs of only a small increase in plasma volume. The mainstay of these observations is that chronicity of hyponatremia by itself could affect urate excretion. We also observed that in the patients with SIADH, high FE of uric acid inversely correlated with glomerular filtration rate (r = -0.66; P: < 0.01) only during the hyponatremic state. These data suggest that hyponatremia by itself, combined with mild volume expansion and glomerular filtration rate, has a role in the high FE of uric acid in the SIADH.

Relationship between red cell mean corpuscular volume and 6-thioguanine nucleotides in patients treated with azathioprine.

Azathioprine (AZA) is characterized by high interindividual differences in bioavailability and metabolization. The aim of the present study was to analyze, in patients treated with AZA for various immune system disorders, whether the variation in red blood cell mean corpuscular volume (deltaMCV) could be used as an indirect estimation of the level of the active immune modifier metabolite 6-thioguanine nucleotides (6-TGN). In 43 consecutive patients treated with a stable dose of AZA for at least 6 months who were not initially anemic, the erythrocyte 6-TGN levels with routine hematologic parameters were determined two to four times at 1-month intervals. In most patients MCV significantly increased after 3 months of therapy and stabilized after 6 months. The correlation between the daily dose of AZA and the 6-TGN level was mild (r = 0.51; P<.001). A weak correlation was also found between the dose of AZA and the deltaMCV after at least 6 months of therapy (r = 0.36; P<.05). The correlation between deltaMCV and 6-TGN level, however, was much better (r = 0.74; P<.001). The lack of a significant increase in MCV after 3 to 4 months of AZA therapy reflects low 6-TGN levels, sometimes a result of undertreatment. A determination of the 6-TGN level during the first months after AZA therapy is begun will allow more accurate adaptation of the effective dose. We observed that deltaMCV could be used as an indicator of 6-TGN levels after 6 months of AZA treatment. An increase in MCV of at least 6 fL is expected to reflect a 6-TGN level of about 175 pmol/8x10(8) red blood cells (probably being within a therapeutic value).

Restoration of the uricosuric effect of probenecid after triglycylvasopressine administration in a gouty patient.

A 35-year-old patient with severe gout and mild renal insufficiency presented very low urinary urate excretion. Volume expansion induced by fludrocortisone combined or not with a uricosuric drug (Benzbromarone) was unable to significantly increase his urate excretion. A combined Probenecid (PB) and Pyrazinamide (PZA) test was performed. These drugs being considered to affect renal tubular reabsorption or secretion. No significant modification of uric acid fractional excretion (FE.uric acid) was observed after PB and PZA. When the same test was performed after the administration of Triglycyl-lysine vasopressine (TGLV), a potent V1 receptor stimulator, we observed a three fold increase in FE.uric acid after PB intake (from 6 to 18%) followed by a decrease after PZA (from 18 to 5.6%). When TGLV was administered alone their was no significant modification of uric acid fractional excretion. We propose that TGLV decrease proximal tubular urate reabsorption that could only be detected when postsecretory reabsorption is blocked by an uricosuric drug.

The treatment of severe hyponatremia.

Severe hyponatremia may be chronic (days) or acute (hours), symptomatic or asymptomatic. Severe chronic symptomatic hyponatremia (serum sodium concentration < 110 to 115 mM/liter) occurs most commonly in the syndrome of inappropriate antidiuretic hormone secretion (SIADH). The treatment of this hyponatremia is a challenge to practicing physicians, in part because an overly rapid correction of hyponatremia may cause brain damage. The latter sometimes takes the form of central pontine myelinolysis (CPM). On the basis of available clinical and experimental literature, the rate of correction of this symptomatic hyponatremia should be no more than 0.5 mM per liter per hour, and the initial treatment should be halted once a mildly hyponatremic range of the serum sodium concentration has been reached (approximately 125 to 130 mM/liter). In contrast, severe chronic asymptomatic hyponatremia may be treated sufficiently by a fluid restriction. On the other hand, severe symptomatic acute hyponatremia should be treated promptly and rapidly, using hypertonic saline, to initially reach a mildly hyponatremic level.

Hyperuricemia as a clue for central diabetes insipidus (lack of V1 effect) in the differential diagnosis of polydipsia.

PURPOSE: In the differential diagnosis of patients with polyuria-polydipsia one must distinguish usually between primary polydipsia (PP) and central diabetes insipidus (CDI). The first situation is a state of volume expansion and the second of volume contraction. We evaluate whether serum uric acid determination could help to differentiate between the two conditions. PATIENTS AND METHODS: We analyzed the score of 13 consecutive patients with CDI, 7 patients with PP, and 7 patients with nephrogenic diabetes insipidus (NDI). Serum uric acid concentration was available during normonatremia without treatment with 1-desamino-8-D-arginine vasopressin (dDAVP), during mild dehydration and during treatment with dDAVP. In 8 of these patients plasma renin activity (PRA), urate, urea and creatinine clearances were also available. These data were also obtained in the patients with NDI. In 1 patient with CDI, we studied the effect on urate clearance of dDAVP, which stimulates exclusively the V2 receptors, and of triglycyl-lysine-vasopressin (TGLV), a potent V1-receptor agonist. RESULTS: Normonatremic polydypsic patients with CDI presented an increase in uric acid concentration (7.1 +/- 2.2 mg/dL), whereas in the PP group the value was decreased (3 +/- 0.75 mg/dL; P <0.001). All the normonatremic PP presented a serum uric acid concentration lower than 5 mg/dL, whereas all the normonatremic CDI patients, exept 1, presented a value higher than 5 mg/dL. In both groups blood urea concentration was decreased as a consequence of high renal clearances. The hyperuricemia of CDI was related to low uric acid clearances. Patients with hypernatremia and NDI presented a lower increase in serum uric acid concentration than those with similar levels of hypernatremia and CDI (NDI: 5.7 +/- 0.8 mg/dL and CDI: 7.9 +/- 2.3 mg/dL; P <0.05) and the NDI patients presented an urate clearance corrected for creatinine clearance which was significantly higher than in CDI (9% +/- 3% and 4% +/- 1.1%; P <0.01). When the patients with CDI were treated with dDAVP and normalyzed their PRA (0.9 +/- 0.4 ng/mL/h) we observed still mild hyperuricemia compared to controls (5.5 +/- 1.4 mg/dL and 4.3 +/- 0.9 mg/dL; P <0.01) and a low fractional excretion of filtered uric acid (6.5% +/- 1.7% compared to 8.2% +/- 2% in controls; P <0.05). Acute administration of dDAVP, stimulating the V2 receptors, in one patient with CDI, had no effect on urate clerance, while TGLV, which stimulates the V1 receptor, increased urate clearance. CONCLUSION: The presence of an serum uric acid concentration higher than 5 mg/dL in polyuric polydipsic patients is highly suggestive of CDI. Even when these patients are treated with dDAVP many of them remain hyperuricemic, and this seems to be the consequence of a lack of V1 receptor stimulation.

Indirect evidence to suggest that prolactin induces salt retention in cirrhosis.

Prolactin is known to have renal sodium retention properties in animals. In man, only two studies have suggested a similar effect in healthy volunteers or in patients with microprolactinoma. Since hyperprolactinemia is frequently observed in liver disease, this prospective study of 19 patients evaluated the influence of prolactin on urinary electrolytes excretion in cirrhosis. Basal hyperprolactinemia was found in 14 out of 19 cases. The effect of serum prolactin elevation on renal sodium and potassium excretion was studied in all patients after thyrotropin-releasing hormone stimulation (200 micrograms), with seven consecutive hourly urinary samples. Patients were separated into two groups according to amount of prolactin discharge after thyrotropin-releasing hormone injection. Group I included patients with "low prolactin release", defined as the difference between basal and peak prolactin values (delta prolactin) < 1000 mu u/ml (n = 8), and no change in natriuresis could be observed. In contrast, in group II with a "high PRL release" (delta prolactin > 1000 mu u/ml, n = 11), significant reductions in urinary sodium (p < 0.01) and potassium (p < 0.02) excretion were observed, which lasted until the third hour after thyrotropin-releasing hormone injection. A significant correlation was found between peak prolactin values and the decrements of natriuresis (r = 0.70, p < 0.02). The pattern of urinary electrolyte changes and the stability of the ratio UK/UK+Na suggest a possible sodium-retaining effect of prolactin localized proximally to the distal tubule.

Uric acid, anion gap and urea concentration in the diagnostic approach to hyponatremia.

We analyzed the serum anion gap (AG = sodium plus potassium minus chloride plus bicarbonate, N = 11-21 mEq/l), serum uric acid and urea concentrations in hyponatremia of various origins. We found that characteristic chemical patterns emerged in association with different hypotonic states: Low uric acid concentration was typically observed in the SIADH and in hyponatremia related to hypopituitarism. The same observation was also frequently noted in hyponatremia secondary to diuretics or to polydypsia. In the SIADH, we observed a decrease in the AG but to a greater extent (-26%) than one would expect from the simple dilutional effect (-16%). Fifty percent of the patients presented an AG lower than 11 mEq/l. In patients with diuretic-related hyponatremia, one group presented an hypouricemia and a low AG as in SIADH (reflecting volume expansion), in the other group the AG was normal or increased as was uric acid concentration (reflecting volume depletion). In adrenocorticotropin deficiency, hyponatremia was typically associated with a low bicarbonate concentration, a normal AG and hypouricemia. In polydypsic patients with hyponatremia, the AG was usually normal or increased despite sometimes very low sodium levels. Uric acid levels were highly variable, most often decreased. We also noted in these patients that the serum urea levels were correlated with urine osmolality (R = +0.8; p < 0.001), and in 40% of them we observed very low blood urea concentration (0.5-2 mmol/l) at the admission time. In hyponatremia related to cardiac failure or cirrhosis, the AG was usually normal despite mild hypoproteinemia.

Effect of urea and indomethacin intake on solute excretion in the syndrome of inappropriate secretion of antidiuretic hormone.

Our purpose was to compare the effect of urea and indomethacin on solute excretion in hyponatremic patients with inappropriate secretion of antidiuretic hormone (SIADH). In 6 patients (serum Na: 126 +/- 3 mmol/l), the intake of urea (0.1 g/kg) induced a decrease in sodium excretion while urine osmolality, urine flow and osmotic clearance (Cosm) did not change. In the control group, the urinary flow and Cosm were increased as expected, while sodium excretion tended to increase. In the SIADH group, the decrease in the fractional excretion (FE) of Na+ (FE.Na+) (or FE.Cl-) after urea intake was negatively correlated with urinary urea concentration while the FE.K+ was positively correlated with FE.Na+ (or FE.Cl-), which suggests that the effect of urea on sodium excretion takes place proximally to the distal tubule, probably at the thin ascending limb. After indomethacin intake, FE.Na+ (or FE.Cl-), FE.K+, Fe.osm and Fe.urea decreased in the normal and hyponatremic groups. The mean free water reabsorption relatively to osmolar delivery was lower in SIADH (p < 0.05), and did not change significantly after indomethacin intake. The fact that the decrease of FE.Na+ (or FE.Cl-) after indomethacin was associated with a decrease in FE.K+ suggests that the increase in sodium (or chloride) reabsorption occurred more proximally to the distal tubule (probably a the medullary segment of the thick ascending limb of the loop of Henle).

5-year treatment of the chronic syndrome of inappropriate secretion of ADH with oral urea.

We report the case of a patient with an idiopathic syndrome of inappropriate secretion of ADH for more than 6 years. Water restriction was effective only during hospital care but was socially difficult to maintain at home, so that the patient presented frequent symptoms of water intoxication. Normal natremia was also obtained with a high salt intake (9 g/day) but this induced leg edema mild dyspnea and gastric intolerance. The patient was however successfully treated for more than 5 years without any side effects with oral urea (30 g/day) allowing her a normal fluid intake (1-1.5 liters/day). Oral urea, even during long periods, is a safe and effective therapeutic approach for patients with chronic SIADH which is not controlled by water restriction alone.

Evidence of defective tubular reabsorption and normal secretion of uric acid in the syndrome of inappropriate secretion of antidiuretic hormone.

The mechanisms responsible for the increased renal clearance of uric acid in the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are not fully clarified. Studies using either pyrazinamide or probenecid, or both drugs but at an interval of several days, could not undoubtedly distinguish the 'hypersecretory theory' from the one favoring a defect in either post- or presecretory reabsorption. We decided to do a combined pyrazinamide and probenecid test in 5 patients with hyponatremia due to SIADH in order to evaluate more clearly the respective importance of these different pathways. Our results allow the conclusion of a diminished presecretory and mainly postsecretory reabsorption (80 +/- 4.6 and 14 +/- 3% of filtered load, respectively). As far as the secretion of uric acid is concerned (17 +/- 10% of filtered load), we may say that this pathway is adapted to the amount of hypouricemia.

Raised urea clearance in cirrhotic patients with high uric acid clearance is related to low salt excretion.

In cirrhotic patients without renal failure, salt retention could result from a decreased effective intravascular volume or could be a primary event leading to increased intravascular volume. Clearance of urea and uric acid depend on an effective intravascular volume. In the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)--a state of increased intravascular volume--uric acid clearance is increased and that of urea is increased only when salt excretion is low. The intravascular volume of 60 consecutive cirrhotic patients without renal failure was estimated indirectly by studying the relationship between fractional excretion of filtered (FE) sodium, urea, and uric acid. Forty five per cent had a high FE uric acid (> 12%), which could mean a high intravascular volume, and presented with an FE urea that was inversely correlated with FE sodium (r = 0, 62; p < 0.001) as in SIADH, while in the controls the FE urea was positively correlated with FE sodium (r = +0, 46; p < 0.01). In patients who had a normal FE uric acid and low FE sodium (< 0.2%), the FE urea was significantly lower (40 (13)%, n = 20) than in subjects with high FE uric acid and a low FE sodium (61 (9)%, n = 16, p < 0.001); this last group also presented with lower mean blood urea concentrations (3.1 (1.2) mmol/l and 4.0 (1.8) mmol/l; p < 0.05) and a lower supine renin activity (p < 0.01). As observed in the SIADH, cirrhotic patient with high FE uric acid have raised FE urea only when salt excretion is low. It is believed that the low salt excretion is not caused by a decrease in effective intravascular volume and that this is increased in cirrhotic patients with raised FE uric acid.

Dissociation between uric acid and urea clearances in the syndrome of inappropriate secretion of antidiuretic hormone related to salt excretion.

1. Our purpose was to determine why hypouricaemia is more frequently observed than hypouraemia in the syndrome of inappropriate secretion of antidiuretic hormone. We have retrospectively analysed the scores of 35 patients with a chronic form of hyponatraemia related to the syndrome of inappropriate secretion of antidiuretic hormone and studied prospectively six patients. 2. The patients with high fractional excretion of filtered urea (greater than 55%) presented lower blood urea and lower salt excretion than the patients with normal fractional excretion of filtered urea, despite similar levels of hyponatraemia and of osmotic and uric acid clearances. In six hyponatraemic patients, an increase in salt intake was accompanied by a decrease in fractional excretion of filtered urea. In the syndrome of inappropriate secretion of antidiuretic hormone, the fractional excretion of filtered urea was inversely correlated to the fractional excretion of filtered sodium (r = -0.66; P less than 0.001), whereas the fractional excretion of filtered uric acid was not dependent on sodium excretion. 3. Hypouraemia with high fractional excretion of filtered urea in patients with the syndrome of inappropriate secretion of antidiuretic hormone is related to low urinary sodium excretion and thus reflects low sodium intake.

Central venous access for haemodialysis using the Hickman catheter.

One hundred and seven Hickman catheters for haemodialysis were inserted in 90 end-stage chronic renal failure patients, and were used for 1-448 days (median 45 days). Sixty-nine per cent of the patients were treated without any problem for 1-165 days (median 34 days). Clinically evident complications occurred in 44 catheters inserted in 28 patients, and included outflow obstruction (16.8% of the catheters) and thrombosis (13.1% of the catheters). However, many episodes of clotting or insufficient flow could be corrected by simple manoeuvres. Other less frequent complications were recorded: sepsis, mainly in patients with increased risk factors (4.1% of the catheters), laceration of the catheter (3.7%) and occasional cases of jugular-vein phlebitis, transient palsy of a vocal cord, haematoma of the wound, and bleeding of the cutaneous orifice. No clinical sign of subclavian or innominate-vein thrombosis was observed. Nevertheless, a prospective study conducted in 50 asymptomatic patients demonstrated a 12% rate of anomalies of the venous system, although two-thirds of these alterations were mild and had no consequence. When the present series is compared to the results obtained with currently available percutaneous haemodialysis catheters, it is concluded that the Hickman catheter is a safe, comfortable and efficient vascular access device.