Sodium Fate after Sodium Bicarbonate Infusion: Influence of Altered Acid-Base Status

BACKGROUND

We have previously investigated the fate of administered bicarbonate infused as a hypertonic solution in animals with each of the 4 chronic acid-base disorders. Those studies did not address the fate of sodium, the coadministered cation.

METHODS

We examined baseline total body water (TBW), Na+ space, HCO3- space, and urinary sodium and bicarbonate excretion after acute hypertonic NaHCO3 infusion (1-N solution, 5 mmol/kg body weight) in dogs with each of the 4 chronic acid-base disorders. Observations were made at 30, 60, and 90 min postinfusion. Retained sodium that remains osmotically active distributes in an apparent space that approximates TBW. Na+ space that exceeds TBW uncovers nonosmotic sodium storage.

RESULTS

Na+ space approximated TBW at all times in normal and hyperbicarbonatemic animals (metabolic alkalosis and respiratory acidosis), but exceeded TBW by ~30% in hypobicarbonatemic animals (metabolic acidosis and respiratory alkalosis). Such osmotic inactivation was detected at 30 min and remained stable. The pooled data revealed that Na+ space corrected for TBW was independent of the initial blood pH but correlated with initial extracellular bicarbonate concentration (y = -0.01x + 1.4, p= 0.002). The fate of administered sodium and bicarbonate (internal distribution and urinary excretion) was closely linked.

CONCLUSIONS

This study demonstrates that hypobicarbonatemic animals have a Na+ space that exceeds TBW after an acute infusion of hypertonic NaHCO3 indicating osmotic inactivation of a fraction of retained sodium. In addition to an expanded Na+ space, these animals have a larger HCO3- space compared with hyperbicarbonatemic animals. Both phenomena appear to reflect the wider range of titration of nonbicarbonate buffers (Δ pH) occurring during NaHCO3- loading whenever initial [HCO3-]e is low. The data indicate that the fate of administered bicarbonate drives the internal distribution and the external disposal of sodium, the co-administered cation, and is responsible for the early, but non-progressive, osmotic inactivation of a fraction of the retained sodium.

Tacrolimus-induced hypomagnesemia and hypercalciuria requires FKBP12 suggesting a role for calcineurin

Calcineurin inhibitors (CNIs) are immunosuppressive drugs used to prevent graft rejection after organ transplant. Common side effects include renal magnesium wasting and hypomagnesemia, which may contribute to new-onset diabetes mellitus, and hypercalciuria, which may contribute to post-transplant osteoporosis. Previous work suggested that CNIs reduce the abundance of key divalent cation transport proteins, expressed along the distal convoluted tubule, causing renal magnesium and calcium wasting. It has not been clear, however, whether these effects are specific for the distal convoluted tubule, and whether these represent off-target toxic drug effects, or result from inhibition of calcineurin. The CNI tacrolimus can inhibit calcineurin only when it binds with the immunophilin, FKBP12; we previously generated mice in which FKBP12 could be deleted along the nephron, to test whether calcineurin inhibition is involved, these mice are normal at baseline. Here, we confirmed that tacrolimus-treated control mice developed hypomagnesemia and urinary calcium wasting, with decreased protein and mRNA abundance of key magnesium and calcium transport proteins (NCX-1 and Calbindin-D28k ). However, qPCR also showed decreased mRNA expression of NCX-1 and Calbindin-D28k , and TRPM6. In contrast, KS-FKBP12-/- mice treated with tacrolimus were completely protected from these effects. These results indicate that tacrolimus affects calcium and magnesium transport along the distal convoluted tubule and strongly suggests that inhibition of the phosphatase, calcineurin, is directly involved.

Validating the use of bioimpedance spectroscopy for assessment of fluid status in children

BACKGROUND

Bioimpedance spectroscopy (BIS) with a whole-body model to distinguish excess fluid from major body tissue hydration can provide objective assessment of fluid status. BIS is integrated into the Body Composition Monitor (BCM) and is validated in adults, but not children. This study aimed to (1) assess agreement between BCM-measured total body water (TBW) and a gold standard technique in healthy children, (2) compare TBW_BCM with TBW from Urea Kinetic Modelling (UKM) in haemodialysis children and (3) investigate systematic deviation from zero in measured excess fluid in healthy children across paediatric age range.

METHODS

TBW_BCM and excess fluid was determined from standard wrist-to-ankle BCM measurement. TBW_D2O was determined from deuterium concentration decline in serial urine samples over 5 days in healthy children. UKM was used to measure body water in children receiving haemodialysis. Agreement between methods was analysed using paired t test and Bland-Altman method comparison.

RESULTS

In 61 healthy children (6-14 years, 32 male), mean TBW_BCM and TBW_D2O were 21.1 ± 5.6 and 20.5 ± 5.8 L respectively. There was good agreement between TBW_BCM and TBW_D2O (R² = 0.97). In six haemodialysis children (4-13 years, 4 male), 45 concomitant measurements over 8 months showed good TBW_BCM and TBW_UKM agreement (mean difference - 0.4 L, 2SD = ± 3.0 L). In 634 healthy children (2-17 years, 300 male), BCM-measured overhydration was - 0.1 ± 0.7 L (10-90th percentile - 0.8 to + 0.6 L). There was no correlation between age and OH (p = 0.28).

CONCLUSIONS

These results suggest BCM can be used in children as young as 2 years to measure normally hydrated weight and assess fluid status.

[Serum and urine osmolality: clinical and laboratory features]

Clinical practice is frequently challenged by limited funding and resources, which finally limit both clinical effectiveness and safety of some therapies. Electrolyte disorders represent serious problems in the clinical management. Nonetheless the osmometer, that is the reference instrument for routine assessment of osmolality, it is only available in a limited number of healthcare facilities. The diagnosis of the leading electrolyte disorders relies therefore on indirect criteria, frequently inaccurate, especially when inappropriately used. According to recent evidences emerged on prevalence, severity and therapeutic approach of patients with electrolyte disturbances such as hyponatremia, the diagnostic appropriateness is now regarded as an essential aspect of the clinical decision making. Recent multidisciplinary guidelines indicate that urinary osmolality is a mainstay in the differential diagnosis of hyponatremic states. Since hyponatremia is commonplace across a broad range of clinical conditions, it is noteworthy that accurate knowledge of the different equations that may be used for its calculation in serum or urine is not widespread among general and hospital physicians. To couple with these clinical issues, this article is aimed to briefly describe the epidemiology and clinics of osmolality disturbances and to suggest some equations that may be useful for its routine assessment in serum or urine, and which can be applied to different categories of patients. The usefulness and reliability of additional indirect methods used in the diagnostic approach of electrolyte disturbances, such as the assessment of urine specific gravity, will also be briefly discussed. The equations that will be proposed have been validated in small sample population studies, but are commonly used as a surrogate or replacement of direct osmolality assessment. A larger multicentric study is hence necessary to validate the clinical use of the equations used for the calculation of serum and urine osmolality.

[Interpretation of volemia in acute kidney injury]

Assessment of volume status is often challenging in daily clinical practice. One of the clinician's tasks is to prevent or to treat organ systems failures that arise from a mismatch between the transport of oxygen and metabolic needs. Renal failure is a frequently encountered in-hospital diagnosis that is known to alter significantly the prognosis. In patients with acute renal failure in particular, the consequences of an inadequate volume management further increase morbidity and mortality.

Stimulus-specific neuroendocrine responses to osmotic challenges in apelin receptor knockout mice

The expression of the novel peptide apelin and its receptor APJ within specific regions of the brain, in particular the magnocellular neurones of the hypothalamus and the circumventricular organs, has implicated the apelinergic system in mechanisms controlling fluid homeostasis. In addition, apelin and APJ are considered to be involved in controlling arginine vasopressin (AVP) secretion into the circulation and release within the hypothalamic-neurohypophysial system. To clarify the role of APJ during regulation of fluid homeostasis, we compared the effects of osmotic stimulation on the urinary concentrating capacities and central nervous system responses of salt-loaded (SL) and water-deprived (WD) female APJ knockout (APJ(-/-)) mice and wild-type controls. SL resulted in a significantly increased urine volume in APJ(-/-) mice compared to wild-type controls, whereas WD in APJ(-/-) mice failed to reduce urine volume as seen in wild-type controls. AVP transcripts in the supraoptic and paraventricular nuclei and plasma AVP concentrations were significantly attenuated in SL APJ(-/-) mice compared to SL wild-type, but increased comparably in wild-type and APJ(-/-) mice after WD. Analysis of c-fos mRNA expression in the median preoptic nucleus and subfornical organ in response to either WD or SL showed attenuated expression in APJ(-/-) compared to wild-type mice. These findings further implicate the apelinergic system in mechanisms controlling fluid homeostasis, particularly at a neuroendocrine level, and suggest stimulus-specific involvement in vasopressinergic activity.

Electrolyte disturbances and abnormal urine analysis in children with dengue infection

Serum electrolytes and urine analysis results were retrospectively reviewed in children with either dengue fever (DF) or dengue hemorrhagic fever (DHF). Children who had positive serology for dengue infection and serum electrolytes determined before starting intravenous fluid were included in the study. During the years 2004-2007, 73 DF patients, age 9.29 +/- 3.62 years, and 77 DHF patients, age 10.04 +/- 3.64 years were enrolled in the study. The patients were admitted to the hospital on average on days 4.12 +/- 1.1 and 4.25 +/- 1.4 of febrile illness for DF and DHF, respectively. The prevalence of hyponatremia in patients with DF was 61% and DHF was 72% (p = 0.149). The mean serum sodium levels in patients with DF and DHF were 133.5 +/- 3.52 and 133.5 +/- 3.20 mEq/l (p = 0.938), respectively. The prevalence of hyponatremia in patients with mild (grade I), moderate (grade II) and severe (grade III-IV) DHF were 70, 77, and 78% (p = 0.729), respectively, and the mean serum sodium levels were 134.1 +/- 3.05, 132.9 +/- 3.33, and 132.5 +/- 3.28 (p = 0.189), respectively. The prevalence of hypokalemia in patients with DF was 14% and 17% in patients with DHF (p = 0.588). A high urine specific gravity reflecting dehydration was found in 63% of patients with DF and 60% of patients with DHF (p = 0.77). The prevalences of hematuria in patients with DF and DHF were 18% and 27% (p = 0.182), respectively and proteinuria were 15% and 27% (p = 0.072), respectively. The prevalences of hematuria and proteinuria were not different among patients with mild, moderate and severe DHF. No patients had gross hematuria or developed acute renal failure requiring dialysis. Mild hyponatremia is a common electrolyte disturbance and renal involvement is mild in patients with DF and DHF.

Urinary excretion of prostaglandin F2 alpha and 6-keto-prostaglandin F1 alpha during volume expansion in patients with glomerulonephritis

Thirteen patients with active IgA glomerulonephritis (IgA GN), ten patients with a history of Henoch-Schönlein glomerulonephritis (HS GN) and nine healthy controls were studied during hydropenia (HP) and 3% volume expansion (VE) with isotonic saline. Clearance of inulin and para-aminohippurate, urinary excretion of Na, immunoreactive prostaglandin F2 alpha (PGF2 alpha) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were determined. The patients with a history of HS GN had normal blood pressure and renal function. As in the controls, the urinary excretion of PGF 2 alpha decreased and the excretion of 6-keto-PGF1 alpha increased during VE. In the patients with IgA GN the glomerular filtration rate (GFR) was normal, markedly reduced and supernormal. Five patients had hypertension and an increased NA excretion in relation to the GFR during VE. As a group, the patients with IgA GN increased their urinary excretion of 6-keto-PGF1 alpha during VE, while the excretion of PGF2 alpha did not change. In relation to the GFR, the urinary excretion of PGF2 alpha and 6-keto-PGF1 alpha was markedly increased in two patients with low GFR, which implies that these substances play a role in advanced renal disease. VE had little effect on PG excretion in these patients. In the hypertensive patients the urinary excretion of PGF2 alpha and 6-keto-PGF1 alpha was the same as in those with normal blood pressure. PGs are therefore not likely to mediate the increased natriuretic response to VE in hypertension.

Urine proteomics--prospects for future diagnostics

This brief overview of the potential diagnostic, prognostic and pathophysiological value of studies into the urine proteome describes hypothesis-driven investigations of individual proteins and proteome-wide search for urinary biomarkers of various diseases and their progression. It is intended to illustrate the recent progress in the area of urine proteomics and proselytize for the promise of this centuries-old technique of uroscopy, yet to reveal its secrets, using modem approaches.

Electrolyte disorders following oral sodium phosphate administration for bowel cleansing in elderly patients

BACKGROUND

Oral sodium phosphate is currently used for colon preparation prior to colonoscopy or barium enema. Sodium phosphate induces hyperphosphatemia, hypocalcemia, and hypokalemia. Elderly patients are at an increased risk for phosphate intoxication due to decreased glomerular filtration rate, medication use, and systemic and gastrointestinal diseases. We investigated these electrolyte disorders and their correlation with creatinine clearance, coexistent diseases, medications, and functional status.

METHODS

Thirty-six hospitalized patients were included in the study. On day 1, patients were administered 2 doses of oral sodium phosphate. Venous blood samples for electrolyte determination were obtained at 7 AM on days 1, 2 (the procedure day), and 3. Urine samples were obtained from 10 patients.

RESULTS

An increase in serum phosphorus level was correlated with a decreased creatinine clearance (R = -0.52; P =.001). Hypocalcemia and hypokalemia were present in 21 (58%) and 20 (56%) patients, respectively. Patients with a serum potassium concentration of 3.5 mEq/L or less on day 2 had a lower serum potassium concentration on day 1 vs those with a serum potassium concentration greater than 3.5 mEq/L on day 2 (P =.03). Five (dependent patients) had a serum potassium concentration of 3 mEq/L or less and 2 had severe diarrhea, necessitating treatment. There were more demented patients with hypokalemia compared with normokalemic patients (P<.05). Urinary fractional excretion of phosphorus tripled on day 2 (P =.01). Potassium and sodium fractional excretion remained unchanged.

CONCLUSIONS

Sodium phosphate induces serious electrolyte abnormalities in the elderly. The frequency and severity of hypokalemia is due to intestinal potassium loss associated with inadequate renal potassium conservation and is apparently more prevalent in frail patients. Assessment of serum electrolytes, phosphorus, and calcium prior to sodium phosphate preparation is advised, and in selected patients, postprocedural assessment and correction may be required.

Postnatal urinary conductance measurement in preterm infants

The aim of this study was to determine whether serial urinary conductance measurements can be used to estimate reliably the end of the transition period of negative sodium balance in preterm infants. The relationship between urine conductance, measured by a conductance meter, and urine sodium concentration was determined in 109 pooled samples of urine obtained from 14 preterm infants during the transitional period of fluid balance. It was shown by linear regression analysis that urine sodium concentration (mmol l(-1)) = 0.78 x urine conductance - 1.25. Urine sodium concentrations derived from the above formula were concordant with urine sodium measured directly when used to calculate daily sodium balance in all 14 infants.

CONCLUSION

Urine conductance can be accurately measured at the cotside by neonatal nurses and used to identify the timing of the postnatal transition from negative to positive sodium balance in preterm infants. These findings can help in making decisions on the introduction of postnatal sodium administration to preterm infants.

Blood pressure and urinary excretion of electrolytes in Spanish schoolchildren

Despite the importance of hypertension in adults, its effects on child health are poorly understood. This cross-sectional epidemiological study was designed to look for a relationship between elevated blood pressure (BP) in children and 24-h urinary excretion of sodium (Na) and potassium (K), and between BP and dietary salt intake. The study population was all 59 856 schoolchildren aged 6 to 14 years in the province of Almería in southern Spain, among whom 613 participants were chosen randomly for study. We measured 24-h urinary Na and K concentrations, systolic and diastolic BP, body weight and height. There was a weak correlation between Na excretion and systolic BP (r = 0.18, 95% confidence interval 0.10-0.26), and between K excretion and systolic BP (r = 0.49, 95% CI = 0.04-0.20). Body weight was the variable that best correlated with systolic (r = 0.49, 95% CI = 0.43-0.55) and diastolic BP, and with Na excretion (r = 0.48, 95% CI = 0.42-0.55). Multiple regression analysis also showed that body weight was the variable that best correlated with systolic BP (b = 0.58), although the variables in the equation explained little of the total variability in BP (26%). These correlations were significant at P < 0.05. In conclusion urinary electrolytes correlated poorly with BP in a sample of Spanish schoolchildren. Body weight was the only variable that showed a weak relationship with BP and Na excretion.

Urinary excretion of aquaporin-2 in pathological states of water metabolism

Aquaporin-2 (AQP-2) is an arginine vasopressin (AVP)-regulated water channel in renal collecting duct cells. Approximately 3 % of AQP-2 in collecting duct cells is excreted into urine. Urinary excretion of AQP-2 varies widely in different physiological conditions, and it has a positive correlation with plasma AVP levels. Urinary excretion of AQP-2 was significantly increased by the single injection of AVP in patients with central diabetes insipidus. The urinary excretion of AQP-2 was one-eighth over in patients with central diabetes insipidus and three times greater in patients with impaired water excretion than that in normal subjects. In a hypertonic saline test, the urinary excretion of AQP-2 promptly increased 6-12-fold in normal subjects, but remained low in patients with central diabetes insipidus. In addition, exaggerated urinary excretion of AQP-2 persisted after an acute water load in patients with impaired water excretion. These results indicate that urinary excretion of AQP-2 is a potent marker for the diagnosis of water metabolism disorders dependent on AVP.

Magnesium supplementation alleviates premenstrual symptoms of fluid retention

We investigated the effect of a daily supplement of 200 mg of magnesium (as MgO) for two menstrual cycles on the severity of premenstrual symptoms in a randomized, double-blind, placebo-controlled, crossover study. A daily supplement of 200 mg of Mg (as MgO) or placebo was administered for two menstrual cycles to each volunteer, who kept a daily record of her symptoms, using a 4-point scale in a menstrual diary of 22 items. Symptoms were grouped into six categories: PMS-A (anxiety), PMS-C (craving), PMS-D (depression), PMS-H (hydration), PMS-O (other), and PMS-T (total overall symptoms). Urinary Mg output/24 hours was estimated from spot samples using the Mg/creatinine ratio. Analysis of variance for 38 women showed no effect of Mg supplementation compared with placebo in any category in the first month of supplementation. In the second month there was a greater reduction (p = 0.009) of symptoms of PMS-H (weight gain, swelling of extremities, breast tenderness, abdominal bloating) with Mg supplementation compared with placebo. Compliance to supplementation was confirmed by the greater mean estimated 24-hour urinary output of Mg (p = 0.013) during Mg supplementation (100.8 mg) compared with placebo (74.1 mg). A daily supplement of 200 mg of Mg (as MgO) reduced mild premenstrual symptoms of fluid retention in the second cycle of administration.

Measured vs calculated plasma osmolality in infants with very low birth weights

OBJECTIVE

To determine the relationship between measured serum osmolality (MsOsm) and calculated osmolality and to examine factors that may affect the osmolal gap.

RESEARCH DESIGN

Longitudinal cohort study.

SETTING

Regional tertiary neonatal intensive care nursery in a university-affiliated hospital.

PATIENTS

Sixty low-birth-weight infants (birth weight, 540 to 1500 g), studied daily during the first week of life.

SELECTION PROCEDURE

Consecutive sample.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

The MsOsm was significantly higher than the calculated osmolality for the first 6 days of life. The MsOsm was significantly higher during the first 6 days of life in infants with birth weights less than 1000 g than in those with birth weights greater than 1000 g, but the calculated osmolality was similar in both groups. Intraventricular hemorrhage, preservative additives in drugs, and packed red blood cell transfusions did not contribute significantly to osmolal gap or MsOsm. In 19 patients, peak MsOsm was greater than or equal to 320 mmol/kg (mean, 336 +/- 13 mmol/kg; calculated osmolality, 298 +/- 20 mmol/kg; osmolal gap, 38 +/- 19 mmol/kg). Six of these 19 patients died (all with birth weights less than 1000 g).

CONCLUSIONS

A significant proportion of patients with very low birth weights (mostly less than 1000 g) have large osmolal gaps and/or an MsOsm greater than 300 mmol/kg during the first week of life. The relationship between increased MsOsm in infants with very low birth weights and effective osmolality requires further study. Therapeutic intervention based solely on elevated MsOsm is ill advised.

Assessment of changes in body water by bioimpedance in acutely ill surgical patients

OBJECTIVE

To evaluate the relationship between changes in body bioelectrical impedance (BI) at 0.5, 50 and kHz and the changes in body weight, as an index of total body water changes, in acutely ill surgical patients during the rapid infusion of isotonic saline solution.

DESIGN

Prospective clinical study.

SETTING

Multidisciplinary surgical ICU in a university hospital.

PATIENTS

Twelve male patients treated for acute surgical illness (multiple trauma n = 5, major surgery n = 7).

SELECTION CRITERIA

stable cardiovascular parameters, normal cardiac function, signs of hypovolemia (CVP < or = 5 mmHg, urine output < 1 ml/kg x h).

INTERVENTIONS

After baseline measurements, a 60 min fluid challenge test was performed with normal saline solution, 0.25 ml/kg/min [corrected].

MEASUREMENTS AND RESULTS

Body weight (platform digital scale), total body impedance (four-surface electrode technique; measurements at 0.5, 50 and 100 kHz) and urine output. Fluid retention induced a progressive decrease in BI at 0.5, 50 and 100 kHz, but the changes were significant for BI 0.5 and BI 100 only, from 40 min after the beginning of the fluid therapy onwards. There was a significant negative correlation between changes in water retention and BI 0.5, with individual correlation coefficients ranging from -0.72 to 0.95 (p < 0.01-0.0001). The slopes of the regression lines indicated that for each kg of water change, there was a mean decrease in BI of 18 ohm, but a substantial inter-individual variability was noted.

CONCLUSION

BI measured at low frequency can represent a valuable index of acute changes in body water in a group of surgical patients but not in a given individual.

[Study on urinary function and metabolism of water and electrolytes in primary hypothyroidism]

Water excretion in 16 patients with primary hypothyroidism was lower in amount and more delayed (P less than 0.05) than that in 5 normal controls after acute water ingestion. The mean plasma osmolality of the patients was lower than that of normal controls both before and after water loading. However, the mean urine osmolality was not decreased but rather elevated. The clearance of free water in the patients was lower than that in normal controls before loading, Although the clearance of osmolality in the patients was higher than that in the controls, the difference was insignificant. These two clearance rates were lower than those in the controls after loading. The fractional excretion of sodium (P less than 0.05) and chloride (P less than 0.01) in the patients was significantly higher than that in the controls before loading and both of them remained elevated after loading. Most of the parameters mentioned above improved in 9 patients after treatment with desiccated thyroid.

Laxative abuse as a cause for ammonium urate renal calculi

Nine women with laxative abuse and predominantly ammonium urate renal calculi underwent metabolic studies to identify common chemical abnormalities and determine pathophysiology. The 24-hour urine studies demonstrated marked decreases in volume (902 cm.3), sodium (28 mEq.), citrate (116 mg.) and potassium (21 mEq.). A significant elevation in ammonium urate supersaturation was found compared to control subjects when studied by the computer model EQUIL 2. Of the patients 7 had 1 or more urine specimens positive for phenolphthalein. Gastrointestinal loss of fluid and electrolytes allowed for chronic extracellular volume depletion. Intracellular acidosis was present as judged by low urinary citrate and potassium. The fact that the ion product for ammonium urate is increased significantly compared to controls reflects the stated pathophysiological changes. Laxative abuse should be suspected whenever a woman has an ammonium urate renal calculus in sterile urine.

Impaired osmoregulation at high altitude. Studies on Mt Everest

Osmoregulation was studied in 13 mountaineers who had experienced long-term exposure to high altitude on Mt Everest. Serum osmolality rose from 290 +/- 1 mOsm/kg to 295 +/- 2 mOsm/kg at 5,400 m and finally to 302 +/- 4 mOsm/kg at 6,300 m after a mean of 26.5 days above 5,400 m. Despite this degree of osmoconcentration, plasma arginine-vasopressin concentration remained unchanged: 1.1 +/-0.1 microU/mL at sea level, 0.8 +/- 0.1 microU/mL at 5,400 m, and 0.9 +/- 0.1 microU/mL at 6,300 m. Urinary vasopressin excretion was also similar at all three altitudes. We conclude that prolonged exposure to high altitude may result in persistent impairment of osmoregulation, caused in part by an inappropriate arginine-vasopressin response to hyperosmolality.

Characterization and treatment of water, electrolyte, and acid-base imbalances of induced urethral obstruction in the cat

Urethral obstruction induced in adult male cats caused clinical signs identical with those observed in naturally occurring disease. Central nervous system depression, anorexia, dehydration, vomiting, muscle weakness, and hypothermia occurred. Weight loss (due to water loss and catabolism), metabolic acidosis, mild hyponatremia, hyperkalemia, hypermagnesemia, hypocalcemia, hyperphosphatemia, hyperglycemia, azotemia, and hyperproteinemia were also observed. Serum amylase, alkaline phosphatase, and alanine aminotransferase activities were normal. Ten of 13 cats (group 1), with 72 hours' induced obstruction but not treated with parenteral fluids, died either before the obstruction was relieved or within 8 days afterward. Eight cats (group 2) with induced obstruction for 49 to 98 hours developed severe clinical and biochemical alterations. Treatment with a multiple-electrolyte solution, in addition to relief of urethral obstruction, resulted in favorable clinical and biochemical responses. These cats survived and were clinically healthy at 9 to 10 days after relief of obstruction. It was concluded that use of a multiple-electrolyte solution to correct acidosis, restore circulatory volume, and enhance renal excretion of potassium was effective supportive therapy after urethral obstruction was removed.

Recurrent hypernatremia; a proposed mechanism in a patient with absence of thirst and abnormal excretion of water

A 7-year-old girl twice developed severe hypernatremia (serum sodium values up to 194 mEq/l) without obvious cause. The ability of her kidneys to conserve water was normal, and increasing her plasma osmolality stimulated an appropriate ADH response. Unable to excrete a water load, her kidneys continued to conserve water even with a serum sodium concentration of 133 mEq/l. She was never thirsty and did not ingest sufficient fluid by choice. Although there was no demonstrable anatomic lesion, we postulate a localized defect of her thirst center. This may have modified release of ADH and resulted in an inability to dilute the urine by interrupting a pathway that could exist from the thirst center to the supraoptic nuclei. A therapeutic regimen based on these studies has prevented further hypernatremia.

Two natriuretic substances in extracts of urine from normal man when salt-depleted and salt-loaded

When the extra-cellular fluid volume is expanded, the subsequent rise in urinary sodium excretion that occurs is due in part to a change in the concentration of some circulating natriuretic substance. Two natriuretic substances with different characteristics on Sephadex chromatography have been previously been identified separately by different workers. Extracts prepared from the urine of 31 normal subjects were tested for these two natriuretic materials in the normal conscious water-loaded rat. Two natriuretic fractions were found. The larger of the two was prepared on G50 Sephadex, and the smaller on G25 Sephadex. The natriuresis produced by the larger material was slow to develop and persisted for two hours. The natriuresis produced by the smaller material was maximal in the first 20 min, declined rapidly within the next 40 min, and tended to rise again during the subsequent 60 min. The amount of natriuretic activity that could be extracted from the freeze-dried urine was diminished by high concentrations of sodium chloride. The natriuretic activity of both materials was greater in the urine of the subjects when they were salt-loaded than when they were salt-depleted. The urine of salt-depleted subjects contained significant amounts of natriuretic material.

A preventive effect of potassium against fatal lithium intoxication in rats

The effect of potassium against lithium intoxication was studied in two groups of rats given food containing 100 mmol of sodium and 100 or 1,100 mmol of potassiam/kg dry weight. After 1 week 80 mmol of lithium chloride/kg dry weight was added to both diets. Four days later the body weight, serum lithium concentration, and urinary lithium clearance were all significantly higher in the high potassium group than in the other group. After 15 days the lithium clearance had fallen to one fifth in the lowest potassium group but was unaltered in the high potassium group. All rats in the low potassium group continued to lose weight and died of lithium intoxication within 20 days, while the rats given high potassium survived and gained weight. A high potassium content of the food was able to prevent a fatal lithium-induced loss of sodium and to maintain a normal lithium clearance. It is suggested that also a lithium-induced loss of potassium was counteracted.