Urinary retention: a cause of hyponatremia?

BACKGROUND: Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most common cause of hyponatremia in elderly hospitalized patients; however in many patients the etiology remains unclear even after routine investigations. OBJECTIVE: To report our experience of the association of hyponatremia and urinary retention in elderly hospitalized patients. PATIENTS: Six patients with hyponatremia and urinary retention who were admitted to the geriatric department in our hospital during a four-year period (2001-2004). RESULTS: The mean age of the patients was 85 years. The mean serum sodium level was 120 mEq/l, average volume of retained urine was 933 ml (range 500-1,500 ml). All patients underwent a comprehensive work-up seeking a possible cause for the hyponatremia. The diagnostic work-up was negative. In 5 of the patients the laboratory findings fulfilled the criteria for SIADH. In all patients hyponatremia resolved following urinary catheterization and fluid restriction. All patients made a complete recovery. CONCLUSIONS: Potentially, urinary retention by itself may cause hyponatremia. The possible mechanism for this is SIADH, triggered by bladder distention or pain due to bladder distention. Urinary catheterization may be the key to treatment in these cases of hyponatremia.     

Minireview: The neuroendocrinology of the suprachiasmatic nucleus as a conductor of body time in mammals

Circadian rhythms in physiology and behavior are regulated by a master clock resident in the suprachiasmatic nucleus (SCN) of the hypothalamus, and dysfunctions in the circadian system can lead to serious health effects. This paper reviews the organization of the SCN as the brain clock, how it regulates gonadal hormone secretion, and how androgens modulate aspects of circadian behavior known to be regulated by the SCN. We show that androgen receptors are restricted to a core SCN region that receives photic input as well as afferents from arousal systems in the brain. We suggest that androgens modulate circadian behavior directly via actions on the SCN and that both androgens and estrogens modulate circadian rhythms through an indirect route, by affecting overall activity and arousal levels. Thus, this system has multiple levels of regulation; the SCN regulates circadian rhythms in gonadal hormone secretion, and hormones feed back to influence SCN functions.     

Antiviral effects of lamivudine, emtricitabine, adefovir dipivoxil, and tenofovir disoproxil fumarate administered orally alone and in combination to woodchucks with chronic woodchuck hepatitis virus infection

Adefovir dipivoxil (ADV) and tenofovir disoproxil fumarate (TDF) are nucleotide analogs that inhibit the replication of wild-type hepatitis B virus (HBV) and lamivudine (3TC)-resistant virus in HBV-infected patients, including those who are coinfected with human immunodeficiency virus. The combination of ADV or TDF with other nucleoside analogs is a proposed strategy for managing antiviral drug resistance during the treatment of chronic HBV infection. The antiviral effect of oral ADV or TDF, alone or in combination with 3TC or emtricitabine (FTC), against chronic woodchuck hepatitis virus (WHV) infection was evaluated in a placebo-controlled study in the woodchuck, an established and predictive model for antiviral therapy. Once-daily treatment for 48 weeks with ADV plus 3TC or TDF plus FTC significantly reduced serum WHV viremia levels from the pretreatment level by 6.2 log₁₀ and 6.1 log₁₀ genome equivalents/ml serum, respectively, followed by TDF plus 3TC (5.6 log₁₀ genome equivalents/ml), ADV alone (4.8 log₁₀ genome equivalents/ml), ADV plus FTC (one survivor) (4.4 log₁₀ genome equivalents/ml), TDF alone (2.9 log₁₀ genome equivalents/ml), 3TC alone (2.7 log₁₀ genome equivalents/ml), and FTC alone (2.0 log₁₀ genome equivalents/ml). Individual woodchucks across all treatment groups also demonstrated pronounced declines in serum WHV surface antigen, characteristically accompanied by declines in hepatic WHV replication and the hepatic expression of WHV antigens. Most woodchucks had prompt recrudescence of WHV replication after drug withdrawal, but individual woodchucks across treatment groups had sustained effects. No signs of toxicity were observed for any of the drugs or drug combinations administered. In conclusion, the oral administration of 3TC, FTC, ADV, and TDF alone and in combination was safe and effective in the woodchuck model of HBV infection.     

Renal function in children with β-thalassemia major and thalassemia intermedia

In beta-thalassemia, profound anemia and severe hemosiderosis cause functional and physiological abnormalities in various organ systems. In recent years, there have been few published studies demonstrating proteinuria, aminoaciduria, low urine osmolality, and excess secretion of the tubular damage markers, such as urinary N-acetyl-D-glucosaminidase (U(NAG)) and beta2 microglobulin, in patients with thalassemia. The object of this study was to analyze renal tubular and glomerular function in pediatric patients with beta-thalassemia and to correlate the renal findings to iron overload. Thirty-seven patients with beta-thalassemia major and 11 with thalassemia intermedia were studied. Twelve children without iron metabolism disorders or renal diseases served as a control group. No difference in blood urea nitrogen (BUN), serum creatinine, creatinine clearance, electrolytes, fractional excretion of sodium and potassium, and tubular phosphorus reabsorption was found. Serum uric acid was equal in the two groups, but its urine excretion was significantly higher in the thalassemic group. U(NAG) and U(NAG) to creatinine ratio (U(NAG/CR)) were elevated in all patients with thalassemia compared with the control group (p < 0.001) and were directly correlated to the amount of transfused iron but not to actual ferritin level. We found that renal tubular function is impaired in children with beta- thalassemia major and intermedia. It is not known whether these functional abnormalities would have any long-term effects on the patients. Further studies are needed, and means of preventing these disturbances should be sought.     

A randomized comparison of conventional vs articulating laparoscopic needle-drivers for performing standardized suturing tasks by laparoscopy-naive subjects

Associate Editor Ash Tewari Editorial Board Ralph Clayman, USA Inderbir Gill, USA Roger Kirby, UK Mani Menon, USA

OBJECTIVES

To compare the efficacy of conventional and articulating laparoscopic needle‐drivers for performing standardized laparoscopic tasks by medical students with no previous surgical experience.

SUBJECTS AND METHODS

Twenty medical students with no surgical experience were randomly assigned to two equal groups, one using a conventional laparoscopic needle‐holder (Karl Storz, Tuttlingen, Germany) and the other using a first‐generation articulating laparoscopic needle‐holder (Cambridge Endo, Framingham, MA, USA). Each student performed a series of four standardized laparoscopic tasks, during which speed and accuracy were assessed. The tasks tested needle passage through rings (1), an oblique running suture model (2), a urethrovesical anastomosis model (3) and a model simulating renal parenchymal reconstruction following partial nephrectomy (4).

RESULTS

Tasks 1 and 3 were completed significantly more quickly by those using the conventional instruments (P < 0.05), but there was no statistically significant difference for task 2 and 4 (P > 0.05). Those using conventional instruments were significantly more accurate in all of the tasks than those using the articulated instruments (P < 0.05).

CONCLUSIONS

The conventional laparoscopic needle‐driver allowed laparoscopy‐naive medical students to complete a series of standardized suturing tasks more rapidly and accurately than with the novel articulating needle‐driver. Laparoscopic suturing with first‐generation articulating needle‐drivers might be more difficult to learn, secondary to the complexity of physical manoeuvres required for their use.     

IL-6 Levels,Nutritional Status,and Mortality in Prevalent Hemodialysis Patients

Summary

Background and objectives

The influence of serum IL-6 levels on nutritional status in chronic hemodialysis (HD) patients remains to be elucidated. The present report describes a prospective longitudinal study of IL-6 levels and nutritional parameters to determine whether high IL-6 levels are independently associated with nutritional status over time in a cohort of prevalent hemodialysis patients.

Design, setting, participants, & measurements

85 clinically stable hemodialysis patients (37.6% women), with a mean age of 66.5 ± 10.6 years, were studied after exclusion of patients with BMI < 20 kg/m² and/or serum albumin <35 g/L. IL-6, dietary energy and protein intake, and biochemical markers of nutrition and body composition (anthropometry and bioimpedance analysis) were measured at baseline and at 6, 12, 18, and 24 months following enrollment. Observation of this cohort was continued over 2 additional years.

Results

IL-6 levels increased with time in both unadjusted (linear estimate: 2.57 ± 0.44 pg/ml per 2 yrs; P = 0.001) and adjusted models (linear estimate: 2.35 ± 0.57 pg/ml per 2 yrs; P = 0.049). Significant reductions of daily energy intake, laboratory markers (albumin, transferrin, cholesterol, creatinine), and body composition (fat mass) with higher IL-6 levels were observed over the duration of the longitudinal observation period. However, none of the studied parameters were associated with changes in IL-6 levels over time (IL-6-by-time interactions were NS). Furthermore, cumulative incidences of survival were correlated with the baseline serum IL-6 levels (P = 0.004 by log-rank test). Finally, for each pg/ml increase in IL-6 level, the hazard ratio for death from all causes was 1.06 (95% CI 1.01 to 1.10) after adjustment for demographic and clinical parameters.

Conclusions

Our results suggest that higher serum IL-6 levels are associated with all-cause mortality without additional changes in clinical and laboratory markers of nutritional status in clinically stable HD patients.