Sodium serum levels in hypoalbuminemic adults at general medical wards

Níveis séricos de sódio em adultos hipoalbuminêmicos numa enfermaria geral

SODIUM SERUM LEVELS IN HYPOALBUMINEMIC ADULTS AT GENERAL MEDICAL WARDS

Daniel Ferreira da Cunha, Ana Augusta Sousa Barbosa, Alessandra Manfrin, Fabiana Sucupira Tiveron and Selma Freire de Carvalho da Cunha

RHCFAP/2959

CUNHA, D. F. da et al. - Sodium serum levels in hypoalbuminemic adults at general medical wards. Rev. Hosp. Clín. Fac. Med. S. Paulo 54 (2): 39 - 42, 1999.

SUMMARY: Hypoalbuminemia may cause interstitial edema and hemodilution, which we hypothesized may influence serum sodium levels. Our purpose was to compare serum sodium levels of hospitalized adults with or without hypoalbuminemia. All sodium and albumin serum levels of 142 adults hospitalized at general medical wards over a six-month period were searched at a University Hospital mainframe computer. Relevant laboratory data and clinical details were also registered. Hypoalbuminemia was defined by serum albumin concentration < 3.3 g/dl Fisher, Mann-Whitney, and Student's t tests were applied to compare groups with or without hypoalbuminemia. Ninety-nine patients, classified as hypoalbuminemic, had lower blood hemoglobin (10.68 ± 2.62 vs. 13.54 ± 2.41), and sodium (135.1 ± 6.44 vs. 139.9 ± 4.76mEq/l) and albumin (2.74 ± 0.35 vs. 3.58 ± 0.28g/dl) serum levels than non-hypoalbuminemic (n=43). Pearson's coefficient showed a significant direct correlation between albumin and sodium serum levels (r=0.40) and between serum albumin and blood hemoglobin concentration (r=0.46). Our results suggest that hypoalbuminemic adults have lower serum sodium levels than those without hypoalbuminemia, a phenomenon that may be at least partially attributed to body water retention associated with acute phase response syndrome.

DESCRIPTORS: Sodium. Hypoalbuminemia. Acute phase response syndrome.

Considered as a marker of severe disease and a consistent predictor of mortality and poor outcome among hospitalized adults², hypoalbuminemia is seen in up to 50% of internal medicine patients and 65% of adults in intensive care units^2,5. The main causes of low serum albumin levels include² decreased synthesis (protein-energy malnutrition, cirrhosis), increased catabolism (trauma, infection) and body losses (burns, nephrotic syndrome), hemodilution (postoperative state, sepsis), and fluid shifts from intravascular to interstitial space secondary to increased vascular permeability (systemic leaky capillary syndrome)¹.

Hypoalbuminemia is often associated with decreased colloid oncotic pressure, which causes interstitial sodium and water retention², eliciting hypovolemia, and increases in aldosterone and antidiuretic hormone secretion and/or activity. These hormonal changes lead to positive body water balance and weight gain, as well as progressive dilution of cells and other solid components of plasma, including electrolytes^6,9. As sodium is the main intravascular cation⁶, our hypothesis was that hospitalized adults with decreased serum albumin levels would also have lower serum sodium levels. Our purpose was to compare serum sodium levels of hospitalized adults with or without hypoalbuminemia.

METHODS

This retrospective study was conducted at the University Hospital of the Medical School of Uberaba, MG, Brazil, after official approbation by our institutional Ethics Committee. All plasma albumin and sodium results (n=1.253) over a 6-month period (July to December of 1994) were searched in the hospital computer mainframe. The names and patients' records were organized in a database, which also included patients' demographic data, such as age, gender, and color.

Cases with more than one biochemical measurement had only the first one included in the database, yielding 633 cases. In order to obtain greater uniformity in relation to age and diagnosis, all cases from Pediatrics, Surgical, or Obstetrics-Gynecological wards were excluded. The charts of the remaining 142 patients at general medical wards were then perused by three observers to obtain relevant clinical details and the most likely diagnosis on the day the albumin and sodium levels were registered. Main diagnosis and the presence of edema, dyspnea, and fever were also registered. Biochemical parameters, including glucose, potassium, magnesium, phosphorus, calcium, urea, and creatinine serum levels, besides blood hemoglobin were also included in the database file. The concomitance of intravenous dextrose-water 5% (DW5) or isotonic saline infusion was registered, as well as the length of hospitalization stay. Diabetes mellitus was ascertained¹⁰ by previous diagnosis or by the finding of two or more fasting glucose serum levels of 126 mg/dl (7.0 mmol/l) or higher. Hypoalbuminemia was defined by serum albumin concentration lower than 3.3 g/dl.

All serum measurements were made using an Automatic Chemical Analyzer, model Cobas Mira Plus® (Roche Diagnostic Systems, Inc - Branchburg, NJ). The laboratory reference ranges were 135-148 mEq/l for sodium; 3.5-5.0 g/dl for albumin; 70-115 mg/dl for glucose; 3.7-5.5 mEq/l for potassium; 2.0-4.8 mg/dl for phosphorus, 1.9-2.5 mg/dl for magnesium; 8.5-10.4 mg/dl for calcium; 09-1.5 mg/dl for creatinine, and 10-50 mg/dl for urea.

Numeric variables with normal distribution were expressed as mean ± standard deviation; differences among patients with or without oalbuminemia were compared by the non-paired t test. The Mann-Whitney test was applied to compare non-homogeneous numeric data that were expressed as median, minimum and maximum values (range). The proportions were compared by the Chi-square or the Fisher's exact tests. Pearson's correlation coefficients were determined for serum albumin and sodium, and between albumin and hemoglobin. Probabilities (p) less than 0.05 were considered significant.

RESULTS

A total of 142 patients were eligible for the study. Ninety-nine (69.7%) hypoalbuminemic patients did not differ from those classified as non-hypoalbuminemic in relation to demographic data, including a greater percentage (%) of male (57.6 vs. 58.1) and white color (72.3 vs. 69.8). Nevertheless, when compared to non-hypoalbuminemic, hypoalbuminemic patients were statistically older (53.9 ± 18.3 vs. 44.1 ± 21.1 years) and had a more prolonged hospital stay (17.5; range: 2 to 96 days vs. 11.5; range: 3 to 45 days).

Except for cancer (14.1 vs. 2.3%), there were no statistical differences between hypoalbuminemic and non-hypoalbuminemic patients, respectively, in relation to the diagnosis (%) of pneumonia (19.2 vs. 16.3), systemic arterial hypertension (16.2 vs. 13.9), diabetes mellitus (14.1 vs. 13.9), hepatic cirrhosis (11.1 vs. 4.6), protein-energy malnutrition (6.1 vs. 2.3), stroke (8.0 vs. 2.3), chronic obstructive pulmonary disease (5.0 vs. 7.0), and acquired immunodeficiency syndrome (3.0 vs. 4.6). Similarly, there was no difference between hypoalbuminemic and non-hypoalbuminemic groups in relation to the presence (%) of edema (36.4 vs. 34.3), dyspnea (31.1 vs. 25.8), fever (13.7 vs. 6.7) and congestive heart failure (11.1 vs. 4.6).

The percentage of patients receiving isotonic saline was statistically similar among hypoalbuminemic and non-hypoalbuminemic (37.4 vs. 30.9), the same occurring in relation to DW5% infusion (44.6 vs. 28.6). Although hypoalbuminemic patients more frequently received two or more antibiotics, the percentage of cases taking these drugs was similar between groups (respectively 43.4 vs. 30.2%).

There were no significant differences among patients with or without hypoalbuminemia in relation to the serum levels (mg/dl) of creatinine (0.89 ± 0.38 vs. 0.86 ± 0.32) and urea (35.5 ± 18.1 vs. 34.2 ± 22.6), the same occurring in relation to peripheral leukocytes (8,000; range: 500-24,600 vs. 7,700; range 650-15,800 cells/mm3) and lymphocytes (1916.6 ± 1196.7 vs. 1963.6 ± 1067.6 cell/mm³). Leukocytosis (WBC > 9000/mm³) occurred in 33.1% of cases, without statistical difference among hypoalbuminemic (36.4%) and non-hypoalbuminemic (25.6%). Electrolytes and glucose serum levels were similar between hypoalbuminemic and non-hypoalbuminemic patients (Table 1). Thirty hypoalbuminemic and fifteen non-hypoalbuminemic patients showed hyperglycemia (serum glucose > 115 mg/dl; p = 0.58).

Hypoalbuminemic patients had lower values of serum sodium and blood hemoglobin (Table 1). Pearson's coefficient showed a significant direct correlation between albumin and sodium serum levels (r = 0.40; p > 0.01; (Figure 1) and between serum albumin and blood hemoglobin concentration (r=0.46; p < 0.01).

Figure 1 -
Pearson's correlation between serum sodium and albumin levels of 142 adults hospitalized at general medical wards of Medical School of Uberaba (Brazil).

DISCUSSION

Regarding lower sodium serum levels in hypoalbuminemic patients, this study shows a positive and significant correlation between albumin and sodium serum levels. Albumin serum levels are lower in older persons², and the same occurs with serum sodium⁷, in accordance to our findings. Hypoalbuminemic patients were older, stayed a longer time in hospital and had a greater proportion of cancer diagnosis than non-hypoalbuminemic ones; likewise, hypoalbuminemic patients also had lower blood hemoglobin levels. Taken together, these findings suggest that hypoalbuminemic patients had more severe diseases, in accordance with the increased morbidity and mortality in hypoalbuminemic^2,5 or hyponatremic^4,6 patients.

Under physiologic conditions, serum sodium levels are tightly regulated by a complex array of neural, humoral, and renal mechanisms that regulate osmolality, intravascular volume, blood pressure, and intake of sodium and water⁴. Disorders of fluid and sodium balance are common findings at general medical wards patients^6,8, with decreasing serum sodium concentration occurring as a result of inappropriate ADH secretion, renal (e.g. tiazide excess) or extra renal (diarrhea, vomiting, third spacing of fluids) losses⁶, acute or chronic renal failure, and glucose or saline⁹, infusion. Elevated body sodium content and dilutional decreasing of serum sodium concentration may also occur in congestive heart failure, cirrhosis, and nephrotic syndrome⁶.

Despite their occurrence in some cases, these conditions do not explain all of our findings, including the high percentage of patients with hypoalbuminemia. A possible explanation for decreased serum sodium levels in hypoalbuminemic cases would be an elevated total body sodium content plus hemodilution, as occurs in acute phase response (APR) syndrome-related hypoalbuminemia^1,3. In addition to hypoalbuminemia (70%), there was a high percentage of patients receiving antibiotics (37%) and displaying leukocytosis (33.1%) and hyperglycemia (30.3%), which also suggests the concomitance of infection-associated APR syndrome³. Hemodilution, or a higher proportion of water in relation to the number of red blood cells, albumin molecules, and sodium ions, may occur in response to renal retention of sodium, chloride, and water during acute infectious illness, secondary to changes in cortisol, aldosterone, and antidiuretic hormone secretion³.

Although positive statistical correlation does not necessarily implicate a cause-effect relationship, body water retention with dilution of intravascular sodium could explain our findings. Some limitations of this retrospective study include: a need for better characterization of APR syndrome, lack of volume status assessment, and lack of urinary electrolytes measurements. Another possible concern is the lack of detailed information about coadministration of medications other than antibiotics and intravenous hydration. Despite that, our preliminary results suggest that hypoalbuminemic adults have lower serum sodium levels than those without hypoalbuminemia, a phenomenon that may be partially attributed to body water retention associated with acute phase response syndrome.

RESUMO

RHCFAP/2959

CUNHA, D.F. da e col. - Níveis séricos de sódio em adultos hipoalbuminêmicos numa enfermaria geral. Rev. Hosp. Clín. Fac. Med. S. Paulo 54 (2): 39 - 42,1999.

Na hipoalbuminemia há menor excreção de água livre, o que diminuiria os níveis séricos de sódio. O objetivo do presente estudo foi comparar os níveis séricos de sódio de adultos hospitalizados, com ou sem hipoalbuminemia. Do computador central do Hospital Escola, obteve-se um banco de dados eletrônico referente a 142 adultos internados nas enfermarias de Clínica Médica entre junho e dezembro de 1994, com registro dos níveis séricos simultâneos de sódio e albumina. Foram registrados as características demográficas dos pacientes, bem como os diagnósticos e exames laboratoriais de rotina. Hipoalbuminemia foi definida por albumina sérica menor que 3,3g/dl. Hipoalbuminêmicos (n=99) diferiram estatisticamente dos controles (n=43) quanto à idade (53,9 ± 18,3 vs. 44,1 ± 21,1anos) e tempo (mediana; faixa de variação) de internação (17,5; 2-96 vs. 11,5; 3-45 dias), bem como menores níveis séricos de albumina (2,74 ± 0,35 vs. 3,58 ± 0,28g/dl), sódio (135,1 ± 6,4 vs. 139,9 ± 4,8 mEq/l) e de hemoglobina (10,7 ± 2,6 vs. 13,5 ± 2,4 g/dl) sangüínea. A correlação de Pearson foi positiva e significativa para sódio e albumina (r = 0,40) e para albumina e hemoglobina (r=0,46). Adultos hipoalbuminêmicos têm menores níveis séricos de sódio que os com albumina normal, fenômeno possivelmente associado à retenção hídrica e hemodiluição.

DESCRITORES: Sódio. Hipoalbuminemia. Síndrome da resposta de fase aguda.

Received for publication on the 03/11/98

From "Departamento de Clínica Médica da Faculdade de Medicina do Triângulo Mineiro" Uberaba, MG. Financial Support from "CNPq" and "FUNEPU".

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Publication Dates

• Publication in this collection
  31 Aug 2000
• Date of issue
  Apr 1999

History

• Received
  03 Nov 1998