Hyponatraemia in Legionnaires' disease

A Novel Diagnostic Scoring System to Differentiate between Legionella pneumophila Pneumonia and Streptococcus pneumoniae Pneumonia

Objective We investigated a novel diagnostic scoring system to differentiate Legionella pneumophila pneumonia from Streptococcus pneumoniae pneumonia. Methods We retrospectively reviewed the clinical data of 62 patients with L. pneumophila pneumonia (L-group) and 70 patients with S. pneumoniae pneumonia (S-group). Results The serum sodium (Na) levels tended to be lower according to the severity [age, dehydration, respiratory failure, orientation disturbance, low blood pressure (A-DROP)] score in the L-group. On a multivariate analysis, we found that four factors were independent predictive markers for inclusion in the L-group: relative bradycardia [hazard ratio (HR) 5.177, 95% confidence interval (CI): 1.072-24.993, p=0.041], lactate dehydrogenase (LDH) levels ≥292 IU/L (HR 6.804, 95% CI: 1.629-28.416, p=0.009), C-reactive protein (CRP) levels ≥21 mg/dL (HR 28.073, 95% CI: 5.654-139.462, p<0.001), and Na levels ≤137 meq/L (HR 5.828, 95% CI: 1.411-24.065, p=0.015). Furthermore, a total score [ranging from 0 to 4, the sum of the points for each factor (0 or 1)] ≥3 points indicated a higher probability of inclusion in the L-group than in the S-group. The diagnostic accuracy of a total score of 3 had a sensitivity of 36.3%, specificity of 100%, and area under the curve of 0.682 (95% CI: 0.558-0.806, p=0.004), and that of a total score of 4 had a sensitivity 27.4%, specificity of 98.2%, and area under the curve (AUC) of 0.627 (95% CI: 0.501-0.754, p=0.045). The diagnostic accuracy had low sensitivity but high specificity. Conclusions We found four markers that might be useful for differentiating L-group from S-group and created a novel diagnostic scoring system.

HIV/AIDS-related hyponatremia: an old but still serious problem

Hyponatremia is the most common electrolyte disorder in hospitals. Many medical illnesses, including congestive heart failure, liver failure, renal failure and pneumonia, may be associated with hyponatremia. In addition, hyponatremia in patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) was first reported in 1993. The evidence suggests that severe hyponatremia is associated with increased morbidity and mortality in human immunodeficiency virus (HIV)/AIDS patients; however, the incidence of hyponatremic syndrome in HIV/AIDS patients remains very high in clinical practice, as almost 40% of HIV/AIDS inpatients in Xinjiang, a developing region of China, are hyponatremic. A method for identifying the pathogenesis and therapeutic treatments for hyponatremia in HIV/AIDS patients is needed. This review focuses on the clinical and pathophysiological aspects of hyponatremia and highlights the causes, presentation and treatment recommendations for hyponatremic patients with HIV/AIDS.

Hyponatremia in patients with infectious diseases

Hyponatremia is a common electrolyte disturbance associated with considerable morbidity and mortality. Hyponatremia may not infrequently be present during the course of an infection, does not cause specific symptoms and may be overlooked by clinicians. Nonetheless, it may reflect the severity of the underlying process. This review focuses on the clinical and pathophysiological aspects of hyponatremia associated with infectious diseases. In the majority of cases, the fall in serum sodium concentration is of multifactorial origin owing to increased secretion of the anti-diuretic hormone either appropriately or inappropriately. Inadvertent administration of fluids may worsen hyponatremia and prolong morbidity.

Clinical potential of C-reactive protein and procalcitonin serum concentrations to guide differential diagnosis and clinical management of pneumococcal and Legionella pneumonia

We retrospectively analyzed the records of 61 hospitalized patients with community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae or Legionella pneumophila. We found that serum procalcitonin and sodium concentrations were significantly lower, and ferritin levels were significantly higher, in patients infected with L. pneumophila than in those infected with S. pneumoniae. The ratio of C-reactive protein to procalcitonin significantly distinguished between the groups. High procalcitonin levels were associated with an adverse clinical course.

A predictive model for the treatment approach to community-acquired pneumonia in patients needing ICU admission

OBJECTIVE

To create a predictive model for the treatment approach to community-acquired pneumonia (CAP) in patients needing Intensive Care Unit (ICU) admission.

DESIGN

Multicenter prospective study.

SETTING

Twenty-six Spanish ICUs.

PATIENTS

One hundred seven patients with CAP, all of them with accurate etiological diagnosis, divided in three groups according to their etiology in typical (bacterial pneumonia), Legionella and other atypical (Mycoplasma, Chlamydia spp. and virus). For the multivariate analysis we grouped Legionella and other atypical etiologies in the same category.

METHODS

We recorded 34 variables including clinical characteristics, risk factors and radiographic pattern. We used a multivariate logistic regression analysis to find out a predictive model.

RESULTS

We have the complete data in 70 patients. Four variables: APACHE II, (categorized as a dummy variable) serum sodium and phosphorus and "length of symptoms" gave an accurate predictive model (c = 0.856). From the model we created a score that predicts typical pneumonia with a sensitivity of 90.2% and specificity 72.4%.

CONCLUSION

Our model is an attempt to help in the treatment approach to CAP in ICU patients based on a predictive model of basic clinical and laboratory information. Further studies, including larger numbers of patients, should validate and investigate the utility of this model in different clinical settings.

Acute infectious pneumonia is accompanied by a latent vasopressin-dependent impairment of renal water excretion

The mechanism of hyponatremia associated with pneumonia has not been definitely established. Moreover, renal water excretion was never systematically investigated in cases of pneumonia without hyponatremia. We therefore studied nine consecutive patients breathing spontaneously (nasal oxygen in five), with acute infectious pneumonia and normal plasma sodium concentration. All the patients were previously healthy. Water loads were administered during illness and after recovery. Extracellular fluid volume, arterial blood pressure, PaO2, and PaCO2 were identical during and after pneumonia. By contrast, renal water excretion was markedly impaired during pneumonia and returned to normal values after recovery. This was attested to by a significant decrease in minimum urine osmolality together with significant increases in the percentage of the excreted water load and the maximum free water clearance, after resolution of the pneumonia. Plasma arginine vasopressin values were significantly higher during pneumonia than after recovery despite similar plasma sodium concentrations, both before and after water load. A positive correlation between plasma arginine vasopressin and minimum urine osmolality was found during pneumonia. Thus, impairment in renal water excretion appeared to be due to resetting of the vasopressin osmostat and could not be attributed to any recognized nonosmotic stimulus for vasopressin secretion. On the other hand, these defects varied in severity depending on the extent of the pneumonia and persisted until clearing of alveolar opacities, accounting for their protracted course in some patients. We conclude that water excretion is impaired in most if not in all patients with acute infectious pneumonia (especially if extended), and that the administration of hypotonic solutions should be avoided in these patients.