DILUTIONAL HYPONATREMIA NOT PREDICTOR OF DEATH

The spontaneous development of dilutional hyponatremia does not independently decrease survival chances in patients with advanced liver disease. Nevertheless, such patients do face a poor prognosis when dilutional hyponatremia spontaneously develops.

Porcel et al evaluated 155 consecutive patients with advanced liver disease, 54 of whom had dilutional hyponatremia (defined by serum sodium levels lower than 130 mEq/L after five days of a hyponatremic diet, restricted water intake, and no diuretic therapy). These 54 patients were compared with 20 cirrhotic patients without hyponatremia, who served as controls. Diuretic use was similar in the two groups.

In half of the 54 patients, factors that precipitated the hyponatremia were present; in the other 27, it appeared to have developed spontaneously. The patients with spontaneous dilutional hyponatremia had a higher mean Child-Pugh index and mean urinary sodium excretion, but they were otherwise similar to the other hyponatremic patients.

The hepatorenal syndrome developed in one cirrhotic control patient, in 15 (56%) of the patients with precipitating factors, and in 23 (85%) of those with spontaneous dilutional hyponatremia. The hepatorenal syndrome did not develop in any patient with a serum sodium level higher than 130 mEq/L.

Mortality in the three groups was 25%, 44%, and 93%, respectively. However, the only independent predictors of death were the Child-Pugh index, the presence of hepatocarcinoma, and the serum urea concentration. When patients with kidney failure on admission were excluded from the analysis, only the Child-Pugh index and the plasma norepinephrine concentration could independently predict outcome.

Porcel A, Díaz F, Rendón P, et al. Dilutional hyponatremia in patients with cirrhosis and ascites. Arch Intern Med. 2002;162:323-328.

PATIENTS ALTER BREATHING PATTERNS TO MINIMIZE DYSPNEA

Little research has been done on how variations in breathing contribute to the clinical manifestation of lung disease. A recent study by Brack et al has found that patients with restrictive lung disease have the ability to achieve different tidal volumes but may deliberately choose a breathing pattern that lessens dyspnea.

Ten men with restrictive lung disease and a control group of seven healthy, age-matched men took part in the study. Each subject’s normal ventilation was measured for one hour, after which mean tidal volume and respiratory cycle time were calculated. A computer was then used to help the subjects breathe at nine different tidal volumes for five minutes each. After each five-minute test, dyspnea was measured by asking subjects, “How uncomfortable is your breathing?” The relationship between variations in tidal volume and dyspnea was calculated.

Compared with the control group, patients with restrictive lung disease had only slight variations in normal breathing. For example, they showed decreases in the coefficients of variation of 56%, 46%, and 33% for tidal volume, expiratory time, and inspiratory time, respectively.

The patients were able to reproduce the nine tidal volumes with the same degree of accuracy as the control group, but they experienced dyspnea after only slight variations in tidal volume. This observation led the authors to conclude that patients with restrictive lung disease deliberately breathe with little variation to avoid dyspnea.

Brack T, Jubran A, Tobin MJ. Dyspnea and decreased variability of breathing in patients with restrictive lung disease. Am J Respir Crit Care Med. 2002;165:1260-1264.

IMPROVED BRONCHDILATOR RESPONSE WITH MUCUS CLEARANCE

The mucus clearance device (MCD) produces oscillations in air pressure and flow, which loosen and help clear mucus. In a study of patients with chronic obstructive pulmonary disease (COPD), Wolkove et al found that using the MCD before inhaled bronchodilation can enhance response to the drug.

Twenty-three patients with COPD were evaluated on three separate days. On day 1, they were given either the actual or a sham MCD and taught how to use it. On days 2 and 3, pulmonary function tests were performed before and after 10 minutes of real or sham MCD use. Patients then took four puffs of a bronchodilator, each puff delivering 20 µg ipratropium bromide and 120 µg albuterol. Pulmonary function tests were repeated 30, 60, and 120 minutes thereafter.

The mean improvement from baseline in forced expiratory volume in one second (FEV1) at 120 minutes after bronchodilator use was 186 mL in the MCD group, compared with 130 mL in the sham group. When expressed as a percentage change from baseline, the improvement in lung function was greater in the MCD group at all time points, but the difference in magnitude of improvement in FEV1 between groups was not significant until 120 minutes. The investigators concluded that using the MCD may improve both treatment response and pulmonary function in patients with COPD.

Wolkove N, Kamel H, Rotaple M, Baltzan MA Jr. Use of a mucus clearance device enhances the bronchodilator response in patients with stable chronic obstructive pulmonary disease. Chest. 2002;121:702-707.

ASTHMA ASSOCIATED WITH LOWER RESPIRATORY SYMPTOMS

Asthma exacerbations are often associated with upper respiratory infections (URIs), more than half of which are caused by rhinoviruses. A longitudinal cohort study by Corne et al has found that people with asthma are not at greater risk of rhinovirus infections; however, they do have more frequent lower respiratory infections (LRIs) that are caused by rhinoviruses, and the resulting symptoms are both more severe and longer-lasting.

Seventy-six adult, cohabiting couples, each with one person having atopic asthma and one with no symptoms, were enrolled. For three months, participants recorded peak expiratory flow (PEF) twice daily and kept a diary of respiratory symptoms. Participants also visited the hospital every two weeks, where nasal aspirates were taken and analyzed for rhinovirus.

Fifty-one participants developed one or more rhinovirus infections during the study. Thirty-eight of 378 samples (10%) from the asthma group tested positive for rhinovirus, as did 32 of 375 samples (9%) from the non-asthma group. Risk of rhinovirus infection did not differ between groups, nor did severity or duration of URI symptoms.

In contrast, LRIs were more likely to be associated with rhinoviruses in the asthma group than in the non-asthma group. Furthermore, the severity and duration of symptoms in those with LRI were significantly greater in the asthma group, as was the mean decrease in peak expiratory flow (14.1% vs 9.5% in those without asthma).

Corne JM, Marshall C, Smith S, et al. Frequency, severity, and duration of rhinovirus infections in asthmatic and non-asthmatic individuals: a longitudinal cohort study. Lancet. 2002;359:831-834.

Return to table of contents