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

Dyselectrolytemia in Children With Severe Pneumonia: A Prospective Study

Background Pneumonia is a condition characterized by inflammation of the lung parenchyma. It is one of the leading causes of mortality in children below five years of age. While predominantly prevalent in developing countries, it is also associated with significant healthcare-associated costs in developed countries. Among the many risk factors for childhood pneumonia, incomplete immunization, nonexclusive breastfeeding for less than six months, delayed weaning, poor household air quality, malnutrition, and low birth weight are the most commonly found. Electrolyte disturbances, also known as dyselectrolytemia, have been associated with a broad spectrum of acute infections, including pneumonia, particularly hyponatremia. It occurs in the majority of community-acquired pneumonia. Hyper- and hypokalemia are less frequently occurring electrolyte disturbances. Electrolyte disturbances are due to impairment of the intrarenal mechanism of urine dilution due to extracellular fluid volume depletion and inappropriate secretion of antidiuretic hormone. The central nervous system is imminently affected by acute hyponatremia. This condition frequently culminates in cerebral edema, a result of the rapid fluid shift, and causes sudden fatality. Aim of the study This study aims to study dyselectrolytemia in children with severe pneumonia. Objectives The study objectives are to assess dyselectrolytemia in children with severe pneumonia and to correlate dyselectrolytemia with morbidity and hospital stay. Methodology  This prospective study was conducted on 80 children in the age group of two months up to five years who visited our tertiary care center and had severe pneumonia. We evaluated the extent of dyselectrolytemia in our study population by analyzing the frequency correlation of different kinds of electrolyte imbalances. We also analyzed the correlation between morbidity and hospital stay. Results Out of 80 children in this study with severe pneumonia, 47 (59%) had electrolyte imbalance. Among the patients with electrolyte imbalance, 31 (39%) patients had hyponatremia followed by hypokalemia in 12 (15%) patients, hypernatremia in 3 (4%) patients, and hyperkalemia in 1 (1%) patient. Among the 17 (21%) children with pneumonia requiring ICU admission, 16 (94%) had dyselectrolytemia and 4 (24%) experienced fatal outcomes. Conclusions The majority of the children who were admitted to the ICU had severe pneumonia along with electrolyte imbalance. This necessitates the monitoring of the electrolyte and nutritional status of the patients with pneumonia. Providing proper nutrition advice for children with pneumonia may reduce morbidity and mortality. Early detection and treatment of electrolyte imbalances in pneumonia cases can decrease prolonged hospital stays, ICU admissions, and the need for mechanical ventilation, ultimately contributing to a reduction in morbidity and mortality.

Effects of fluid and drinking on pneumonia mortality in older adults: A systematic review and meta-analysis

Background and aims

Methods

Results

Conclusions

Can N-3 polyunsaturated fatty acids be considered a potential adjuvant therapy for COVID-19-associated cardiovascular complications?

Coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has currently led to a global pandemic with millions of confirmed and increasing cases around the world. The novel SARS-CoV-2 not only affects the lungs causing severe acute respiratory dysfunction but also leads to significant dysfunction in multiple organs and physiological systems including the cardiovascular system. A plethora of studies have shown the viral infection triggers an exaggerated immune response, hypercoagulation and oxidative stress, which contribute significantly to poor cardiovascular outcomes observed in COVID-19 patients. To date, there are no approved vaccines or therapies for COVID-19. Accordingly, cardiovascular protective and supportive therapies are urgent and necessary to the overall prognosis of COVID-19 patients. Accumulating literature has demonstrated the beneficial effects of n-3 polyunsaturated fatty acids (n-3 PUFA) toward the cardiovascular system, which include ameliorating uncontrolled inflammatory reactions, reduced oxidative stress and mitigating coagulopathy. Moreover, it has been demonstrated the n-3 PUFAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are precursors to a group of potent bioactive lipid mediators, generated endogenously, which mediate many of the beneficial effects attributed to their parent compounds. Considering the favorable safety profile for n-3 PUFAs and their metabolites, it is reasonable to consider n-3 PUFAs as potential adjuvant therapies for the clinical management of COVID-19 patients. In this article, we provide an overview of the pathogenesis of cardiovascular complications secondary to COVID-19 and focus on the mechanisms that may contribute to the likely benefits of n-3 PUFAs and their metabolites.

Prognostic Value of Hyponatremia During Acute Painful Episodes in Sickle Cell Disease

BACKGROUND

Low plasma sodium concentration has been recognized as a prognostic factor in several disorders but never evaluated in sickle cell disease. The present study evaluates its value at admission to predict a complication in adult patients with sickle cell disease hospitalized for an initially uncomplicated acute painful episode.

METHODS

The primary outcome of this retrospective study, performed between 2010 and 2015 in a French referral center for sickle cell disease, was a composite criterion including acute chest syndrome, intensive care unit transfer, red blood cell transfusion or inpatient death. Analyses were adjusted for age, sex, hemoglobin genotype and concentration, lactate dehydrogenase (LDH) concentration, and white blood cell count.

RESULTS

We included 1218 stays (406 patients). No inpatient death occurred during the study period. Hyponatremia (plasma sodium ≤135 mmol/L) at admission in the center was associated with the primary outcome (adjusted odds ratio [OR] 1.95, 95% confidence interval [CI] 1.3-2.91, P = 0.001), with acute chest syndrome (OR 1.95 [95% CI 1.2-3.17, P = 0.008]), and red blood cell transfusion (OR 2.71 [95% CI 1.58-4.65, P <0.001]) but not significantly with intensive care unit transfer (OR 1.83 [95% CI 0.94-3.79, P = 0.074]). Adjusted mean length of stay was longer by 1.1 days (95% CI 0.5-1.6, P <0.001) in patients with hyponatremia at admission.

CONCLUSIONS

Hyponatremia at admission in the medical department for an acute painful episode is a strong and independent prognostic factor of unfavorable outcome and, notably, acute chest syndrome. It could help targeting patients who may benefit from closer monitoring.

Coronavirus Disease-2019 (COVID-19) and Cardiovascular Complications

The coronavirus disease-2019 (COVID-19) has become a global pandemic. It has spread to more than 100 countries, and more than 1 million cases have been confirmed. Although coronavirus causes severe respiratory infections in humans, accumulating data have demonstrated cardiac complications and poor outcome in patients with COVID-19. A large percent of patients have underlying cardiovascular disease, and they are at a high risk of developing cardiac complications. The basics of the virus, the clinical manifestations, and the possible mechanisms of cardiac complications in patients with COVID-19 are reviewed. Before an effective vaccine or medicine is available, supportive therapy and identifying patients who are at high risk of cardiac complications are important.

Talaromyces marneffei laboratory cross reactivity with Histoplasma and Blastomyces urinary antigen

Talaromyces marneffei is a fungal opportunistic infection usually seen in immunocompromised patients from eastern countries. In the US when examining HIV-patients for suspected fungal infections, laboratory serological tests guide therapy until cultures are available. We present the case of a 35-year-old HIV patient originally from Thailand in which urine lab results were positive for Blastomyces and Histoplasma antigen, but biopsy showed T. marneffei. Concomitantly the patient presented with hyponatremia which was deemed to be from SIADH. We present the first case of a patient with T. marneffei cross reactivity with Blastomyces, Histoplasma and SIADH due to pulmonary disease.

Hyponatraemia in patients with community-acquired pneumonia; prevalence and aetiology, and natural history of SIAD

OBJECTIVE

Hyponatraemia is common in community-acquired pneumonia (CAP) and is associated with increased mortality. The mechanism of hyponatraemia in CAP is not completely understood and treatment is therefore ill-defined. We aimed to define the causation of hyponatraemia in CAP.

DESIGN

Prospective, single-centre, observational study of all patients with CAP and hyponatraemia (≤ 130 mmol/L) during a 9-month period.

PATIENTS

The prevalence of each subtype of hyponatraemia, and the associated mortality, was determined in 143 admissions with CAP (Study 1). A sub-cohort of patients with SIAD (n = 10) was prospectively followed, to document the natural history of SIAD associated with CAP (Study 2).

MEASUREMENTS

In Study 2, blood and urine were collected on day 1, 3, 5 and 7 following admission for measurement of plasma vasopressin, sodium, osmolality and urine osmolality.

RESULTS

In study 1, 143/1723(8.3%) of CAP patients had hyponatraemia (≤130 mmol/L). About 66 had SIAD (46%), 60(42%) had hypovolaemic hyponatraemia (HON), 13(9%) had hypervolaemic hyponatraemia (HEN) and 4(3%) patients had hyponatraemia due to glucocorticoid hormone deficiency. Mortality was higher in the HEN than in the HON, SIAD or normonatraemic groups (P < 0.01). In Study 2, plasma sodium concentration normalized in 8/10 (80%) by day 7. Two patients with persistent hyponatraemia were discovered to have underlying bronchiectasis.

CONCLUSIONS

Hyponatraemia in CAP is most commonly secondary to SIAD or hypovolaemia. HEN is less common, but has worse prognosis. Prospective observation demonstrates that in SIAD, plasma AVP and sodium concentrations normalize with antimicrobials; failure of reversal of suggests underlying lung disease, such as bronchiectasis.

Severe Hyponatremia due to Levofloxacin Treatment for Pseudomonas aeruginosa Community-Acquired Pneumonia in a Patient with Oropharyngeal Cancer

Hyponatremia (serum Na levels of <135 mEq/L) is the most common electrolyte imbalance encountered in clinical practice, affecting up to 15–28% of hospitalized patients. This case report refers to a middle-aged man with severe hyponatremia due to Syndrome of Inappropriate Antidiuretic Hormone Secretion related to four possible etiological factors: glossopharyngeal squamous cell carcinoma, cisplatin treatment, right basal pneumonia with Pseudomonas aeruginosa, and the treatment with Levofloxacin. This case report discusses a rare complication of common conditions and of a common treatment. To our knowledge this is the first case of hyponatremia related to Levofloxacin and the second related to fluoroquinolones.

Hyponatremia in the intensive care unit: How to avoid a Zugzwang situation?

Hyponatremia is a common electrolyte derangement in the setting of the intensive care unit. Life-threatening neurological complications may arise not only in case of a severe (<120 mmol/L) and acute fall of plasma sodium levels, but may also stem from overly rapid correction of hyponatremia. Additionally, even mild hyponatremia carries a poor short-term and long-term prognosis across a wide range of conditions. Its multifaceted and intricate physiopathology may seem deterring at first glance, yet a careful multi-step diagnostic approach may easily unravel the underlying mechanisms and enable physicians to adopt the adequate measures at the patient’s bedside. Unless hyponatremia is associated with obvious extracellular fluid volume increase such as in heart failure or cirrhosis, hypertonic saline therapy is the cornerstone of the therapeutic of profound or severely symptomatic hyponatremia. When overcorrection of hyponatremia occurs, recent data indicate that re-lowering of plasma sodium levels through the infusion of hypotonic fluids and the cautious use of desmopressin acetate represent a reasonable strategy. New therapeutic options have recently emerged, foremost among these being vaptans, but their use in the setting of the intensive care unit remains to be clarified.

Dysnatremia, vasopressin, atrial natriuretic peptide and mortality in patients with community-acquired pneumonia: results from the german competence network CAPNETZ

BACKGROUND

Dysnatremia is a frequent finding in patients with community acquired pneumonia (CAP) and a predictor of mortality. We studied the relation between dysnatremia, comorbidities and CT-pro-AVP and MR-proANP.

METHODS

We enrolled 2138 patients (60 ± 18 years, 55% male) with CAP from the CAPNETZ database. Pro-atrial natriuretic peptide (proANP), pro-vasopressin (proAVP), serum sodium and CRB-65 score were determined on admission. Patients were followed up for 28 days. Sodium concentration on admission was examined as a function of mortality at 28 days. Hyponatremia (HypoN) was defined as admission serum sodium <136 mmol/L, hypernatremia (HyperN) as admission serum sodium >145 mmol/L.

RESULTS

HypoN was diagnosed in 680 (31.8%) patients, HyperN in 29 (1.4%) patients. Comorbidities were associated with sodium levels, and CT-pro-AVP and MR-proANP were inversely related to sodium levels. Patients with HypoN were older, had a higher CRB-65 score and higher values of CT-proAVP and MR-proANP (all p < 0.05). When examined as a function of sodium values, a U-shaped association was found between sodium levels and 28 day mortality. In multivariate Cox proportional hazards analysis, HypoN and HyperN were independent predictors of 28 day mortality. Sodium levels added to the predictive potential of proAVP and proANP.

CONCLUSION

HypoN is common at admission among CAP patients and is independently associated with mortality. HyperN is rare at admission among CAP patients but is also independently associated with mortality. The combination of sodium and CT-pro-AVP and MR-proANP levels achieved the highest prediction of mortality.

A severe H7N9 pneumonia with syndrome of inappropriate antidiuresis and vitamin D deficiency

Objective

Some H7N9 patients presented with hyponatremia. But whether SIAD could be the etiology of hyponatremia in H7N9 pneumonia is still not known.

Design, setting, and participants

A H7N9 patient was enrolled. Clinical sign were evaluated. Effective osmolality, urinary osmolality, urinary sodium, thyroid function, adrenal function, 25(OH) Vitamin D and cellular immune function were measured.

Results

(1) The results showed low serum osmolality, inappropriately elevated urine osmolality, elevated urine sodium concentration, low serum uric acid concentration, relatively normal serum creatinine concentration, normal acid-base and potassium balance, normal adrenal and thyroid function in our patient. (2) Our patient showed vitamin D deficiency and decline of cellular immune function.

Conclusions

Some H7N9 pneumonia could cause SIAD. Early detection and appropriate treatment of SIAD in H7N9 pneumonia might be important. Our patient showed vitamin D deficiency and decline of cellular immune function.

Hyponatremia and anti-diuretic hormone in Legionnaires' disease

Background

Medical textbooks often list Legionnaires’ disease as a differential diagnosis of the syndrome of inappropriate secretion of anti-diuretic hormone (ADH) (SIADH), but evidence supporting this association is largely lacking. We tested the hypothesis whether hyponatremia in patients with Legionnaires’ disease would be caused by increased CT-ProVasopressin.

Methods

We measured CT-ProVasopressin and sodium levels in a prospective cohort of 873 pneumonia patients from a previous multicentre study with 27 patients having positive antigen tests for Legionella pneumophila.

Results

Patients with Legionnaires’ disease more frequently had low sodium levels (Na < 130 mmol/L) (44.4% vs 8.2%, p < 0.01), but similar mean CT-ProVasopressin levels (pmol/l) (39.4 [±7] vs 51.2 [±2.7], p = 0.43) as compared to patients with pneumonia of other etiologies. In patients with Legionnaires’ disease, CT-ProVasopressin levels showed a positive correlation with sodium (r = 0.42, p < 0.05). Independent of pneumonia etiology, CT-ProVasopressin correlated significantly with the pneumonia severity index (r = 0.56, p < 0.05), ICU admission (adjusted odds ratio per decile, 95% CI) (1.6, 1.2 - 2.0), and 30-day-mortality (1.8, 1.3 - 2.4).

Conclusion

While Legionnaires’ disease was associated with hyponatremia, no concurrent increase in CT-ProVasopressin levels was found, which argues against elevated ADH levels as the causal pathway to hyponatremia. Rather, Vasopressin precursors were upregulated as response to stress in severe disease, which seems to overrule the osmoregulatory regulation of ADH.

Thirst perception and osmoregulation of vasopressin secretion are altered during recovery from septic shock

Objective

Vasopressin (AVP) secretion during an osmotic challenge is frequently altered in the immediate post-acute phase of septic shock. We sought to determine if this response is still altered in patients recovering from septic shock.

Design

Prospective interventional study

Setting

Intensive care unit (ICU) at Raymond Poincaré and Etampes Hospitals.

Patients

Normonatremic patients at least 5 days post discontinuation of catecholamines given for a septic shock.

Intervention

Osmotic challenge involved infusing 500 mL of hypertonic saline solution (with cumulative amount of sodium not exceeding 24 g) over 120 minutes.

Measurements and main results

Plasma AVP levels were measured 15 minutes before the infusion and then every 30 minutes for two hours. Non-responders were defined as those with a slope of the relation between AVP and plasma sodium levels less than < 0.5 ng/mEq. Among the 30 included patients, 18 (60%) were non-responders. Blood pressure and plasma sodium and brain natriuretic peptide levels were similar in both responders and non-responders during the course of the test. Critical illness severity, hemodynamic alteration, electrolyte disturbances, treatment and outcome did not differ between the two groups. Responders had more severe gas exchange abnormality. Thirst perception was significantly diminished in non-responders. The osmotic challenge was repeated in 4 non-responders several months after discharge and the abnormal response persisted.

Conclusion

More than half of patients recovering from septic shock have an alteration of osmoregulation characterised by a dramatic decrease in vasopressin secretion and thirst perception during osmotic challenge. The mechanisms of this alteration but also of the relationship between haematosis and normal response remain to be elucidated.

Acute pneumonia and the cardiovascular system

Although traditionally regarded as a disease confined to the lungs, acute pneumonia has important effects on the cardiovascular system at all severities of infection. Pneumonia tends to affect individuals who are also at high cardiovascular risk. Results of recent studies show that about a quarter of adults admitted to hospital with pneumonia develop a major acute cardiac complication during their hospital stay, which is associated with a 60% increase in short-term mortality. These findings suggest that outcomes of patients with pneumonia can be improved by prevention of the development and progression of associated cardiac complications. Before this hypothesis can be tested, however, an adequate mechanistic understanding of the cardiovascular changes that occur during pneumonia, and their role in the trigger of various cardiac complications, is needed. In this Review, we summarise knowledge about the burden of cardiac complications in adults with acute pneumonia, the cardiovascular response to this infection, the potential effects of commonly used cardiovascular and anti-infective drugs on these associations, and possible directions for future research.

Radiologic predictors of hyponatremia in children hospitalized with community-acquired pneumonia

BACKGROUND

Hyponatremia (HNa) is the most common electrolyte imbalance seen in clinical practice and a common laboratory finding in children with community-acquired pneumonia (CAP). This study investigated whether there is a link between the radiological pattern seen in patients with CAP and the occurrence of HNa, hypothesizing that children with moderate and severe HNa would have a lobar-segmental pattern on chest radiograph.

METHODS

The medical files and chest radiographs of 54 children with moderate to severe HNa (sodium <130 mmol/L) admitted with CAP over a 2-year period at our institution were retrospectively studied. Community-acquired pneumonia was defined as either lobar-segmental or interstitial by a radiologist blinded to laboratory results.

RESULTS

Hyponatremia was seen more frequently in children with lobar-segmental pneumonia: 40 (74%) compared with 14 (26%) with interstitial pneumonia (P = 0.004). There was no relationship between the pattern of pneumonia seen on chest radiograph and severity of HNa; however, all 6 cases of severe HNa had lobar-segmental CAP, and all patients with complicated CAP were from the lobar-segmental group.

CONCLUSIONS

We found an association between lobar-segmental CAP and moderate or severe HNa. In addition, all cases of severe HNa occurred in patients with lobar-segmental CAP. The presence of a lobar-segmental pattern on chest radiography in CAP suggests the need for assessment of electrolyte status even in patients with adequate respiratory status.

Advising patients to increase fluid intake for treating acute respiratory infections

BACKGROUND

Acute respiratory infection is a common reason for people to present for medical care. Advice to increase fluid intake is a frequent treatment recommendation. Attributed benefits of fluids include replacing increased insensible fluid losses, correcting dehydration from reduced intake and reducing the viscosity of mucus. However, there are theoretical reasons for increased fluid intake to cause harm. Anti-diuretic hormone secretion is increased in lower respiratory tract infections of various aetiologies. This systematic examination of the evidence sought to determine the benefit versus harm from increasing fluid intake.

OBJECTIVES

To answer the following questions.1. Does recommending increased fluid intake as a treatment for acute respiratory infections improve duration and severity of symptoms? 2. Are there adverse effects from recommending increased fluids in people with acute respiratory infections? 3. Are any benefits or harms related to site of infection (upper or lower respiratory tract) or a different severity of illness?

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, issue 4), which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to November Week 3, 2010), EMBASE (1974 to December 2010), Current Contents (2000 to December 2010) and CINAHL (1982 to December 2010). We searched reference lists of articles identified and contacted experts in the relevant disciplines.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that examined the effect of increasing fluid intake in people with acute respiratory infections.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the identified studies to determine eligibility for inclusion.

MAIN RESULTS

No RCTs assessing the effect of increasing fluid intake in acute respiratory infections were found.

AUTHORS' CONCLUSIONS

There is currently no evidence from RCTs for or against the recommendation to increase fluids in acute respiratory infections. The implications for fluid management of acute respiratory infections in the outpatient or primary care setting have not been studied in any RCTs to date. Some non-experimental (observational) studies report that increasing fluid intake in acute respiratory infections of the lower respiratory tract may cause harm. RCTs need to be done to determine the true effect of this very common medical advice.

The clinical challenge of SIADH-three cases

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) remains a challenging disorder to diagnose and treat. Three cases are presented to illustrate these challenges. The first two cases had drug-induced SIADH secondary to a selective serotonin reuptake inhibitor (for depression) or carbamazepine (for trigeminal neuralgia). The third case had SIADH possibly secondary to bronchiectasis. The lowest serum sodium concentrations ranged between 118 and 124 mmol/L in the three cases. Hyponatraemia was not acute and severe symptoms were absent. However, several mild neurological symptoms were present. In the first case, hyponatraemia likely contributed to a fall, which resulted in a fracture of the odontoid process of the axis. The other two cases also had gait disturbances, in addition to nausea, headache, impaired memory, difficulty concentrating and confusion. In at least two of the cases, the underlying cause of SIADH was impossible to reverse. Traditional treatment for SIADH with fluid restriction and demeclocycline failed, caused side effects or increased duration of hospital stay. These examples suggest a need for better treatment options. The introduction of the vasopressin-receptor antagonists for SIADH may be a welcome new therapy to overcome some of these challenges.

Hyponatremic seizure associated with acute respiratory infection

A 66-year-old woman was admitted to our hospital because of vomiting and appetite loss. For the 2 days prior to admission, she had a cold, which had developed into acute viral bronchitis on admission. Because laboratory data on admission showed hyponatremia, intravenous infusion of Ringer's lactate solution was started. However, generalized seizures appeared, and she developed a coma on the day of admission. Her plasma antidiuretic hormone (ADH) level was high in the context of a low serum osmolality on the second hospital day. The infusion rate was increased, and the patient's consciousness level returned to normal. However, her normalized serum Na level declined again as she drank much water to reduce throat discomfort. As the throat discomfort caused by the throat inflammation improved with azulene gargling, her water intake was reduced, and the serum Na concentration returned to normal. Thus, polydipsia caused by a throat inflammation partially contributed to hyponatremia in this patient. We note that increased ADH secretion has been reported in adults with acute respiratory infection. Therefore, we concluded that polydipsia caused by the throat inflammation, plus increased ADH secretion, resulted in hyponatremia in this patient. We should pay attention to the behavior of drinking extra fluid in patients with acute respiratory infections.

Hyponatremia in community-acquired pneumonia

BACKGROUND/AIM

Community-acquired pneumonia (CAP) is a frequent cause for hospitalization and may result in a number of different renal and electrolyte complications. The purpose of this study was to describe the incidence of hyponatremia in CAP and to analyze risk factors for its occurrence.

METHODS

Records were reviewed for all 342 subjects who participated in the Community-Acquired Pneumonia Standardized Order Set study, a 2-year trial of supplemental treatment tools in hospital pneumonia treatment.

RESULTS

Hyponatremia (serum sodium concentration <136 mg/dl) was present at hospital admission in 27.9% of patients. The magnitude was generally mild, only 4.1% of patients had serum sodium <130 mEq/l. Patients with hyponatremia had greater initial heart rate (100.2 vs. 93.2 beats/min, p = 0.03), white blood cell count (15,100 vs. 12,100/mul, p < 0.0001) and pneumonia severity index class 4 or 5 (35.7 vs. 25.1% of patients, p = 0.05). Hyponatremia at admission was associated with greater risk for death and increased length of hospital stay. Hyponatremia developed during the hospitalization in 10.5% of subjects, with most cases being mild, only 2.6% of all patients having serum sodium decrease to <130 mEq/l. Patients developing hyponatremia were more likely to have end-stage renal disease and to have had initial intravenous fluids other than isotonic saline, but had similar severity of illness on admission to those without acquired hyponatremia.

CONCLUSION

Hyponatremia is a common complication present at the time of admission for CAP. It is associated with more severe illness, increased mortality risk and extended hospital stays. Hyponatremia develops less frequently during the hospitalization and is unrelated to severity of illness on admission, but is an iatrogenic complication and thus initial treatment with isotonic saline may reduce the risk of this complication.

Body water and plasma volume in severe community-acquired pneumonia: implications for fluid therapy

OBJECTIVES

To determine changes in total and extracellular body water, plasma volume and sodium in children with severe and very severe pneumonia, and examine the association between these changes and oxygenation.

DESIGN

Prospective, observational.

SUBJECTS

Fifty children aged 2-59 mths with severe and very severe pneumonia.

METHODS

Serum sodium (SNa), plasma osmolality (Posm), urinary sodium (UNa) and osmolality, total body water (TBW), extracellular water (ECW) and plasma volume (PV) were estimated during the acute phase of pneumonia (within 3-6 hrs of presentation) and after recovery. These were correlated with oxygen saturation (SpO(2)) recorded on presentation.

RESULTS

All children had cough, fever, tachypnoea and chest-wall indrawing; 70% had inability to feed and 90% were hypoxaemic (SpO(2) < or = 90%). During the acute phase of illness, among the survivors (n=46), mean (SD) ECW and PV were significantly higher than that after recovery [ECW 318 (45) vs 308 (49) ml/kg, PV 53.2 (2.3) vs 52.1 (2.3) ml/kg, p<0.05]. SNa < or = 135 mmol/L was significantly correlated with ECW and PV excess. SpO(2) showed a significant linear relationship with TBW, ECW and PV (r=0.43, 0.46 and 0.42, respectively, p<0.005) and SNa (r= or <0.33, p=0.02). On multiple regression analysis, ECW, blood urea and PV were significant predictors of SpO(2) (combined r=0.63). The four patients who died had significantly higher Posm and blood urea and lower SpO(2) but in a logistic regression model SpO(2) was the only significant predictor of death (odds ratio 0.54, 95% CI 0.32-0.9, p=0.02).

CONCLUSION

ECW and PV were moderately increased in severe and very severe pneumonia and the increase correlated with better oxygenation. These findings suggest that fluid retention in response to hypoxaemia is directed towards improving circulating volume. The current practice of fluid restriction in hypoxaemic patients with severe pneumonia might be logical only after correction of hypoxaemia.

Advising patients to increase fluid intake for treating acute respiratory infections

BACKGROUND

Acute respiratory infection is a common reason for people to present for medical care. Advice to increase fluid intake is a frequent treatment recommendation. Attributed benefits of fluids include replacing increased insensible fluid losses, correcting dehydration from reduced intake and reducing the viscosity of mucus. However, there are theoretical reasons for increased fluid intake to cause harm. Anti-diuretic hormone secretion is increased in lower respiratory tract infections of various aetiologies. This systematic examination of the evidence sought to determine the benefit versus harm from increasing fluid intake.

OBJECTIVES

To answer the following questions. (1) Does recommending increased fluid intake as a treatment for acute respiratory infections improve duration and severity of symptoms? (2) Are there adverse effects from recommending increased fluids in people with acute respiratory infections? (3) Are any benefits or harms related to site of infection (upper or lower respiratory tract) or a different severity of illness?

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2005), MEDLINE (1966 to July Week 1, 2005), EMBASE (1974 to Week 29, 2005), Current Contents (current 5 years) and CINAHL (1982 to July week 3 2005). Reference lists of articles identified were searched, and experts in the relevant disciplines were contacted.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that examined the effect of increasing fluid intake in people with acute respiratory infections.

DATA COLLECTION AND ANALYSIS

Each author assessed the identified studies to determine eligibility for inclusion.

MAIN RESULTS

No RCTs assessing the effect of increasing fluid intake in acute respiratory infections were found.

AUTHORS' CONCLUSIONS

There is currently no evidence for or against the recommendation to increase fluids in acute respiratory infections. The implications for fluid management in acute respiratory infections have not been studied in any RCTs to date. Some non-experimental (observational) studies report that increasing fluid intake in acute respiratory infections may cause harm. RCTs need to be done to determine the true effect of this very common medical advice.

Systemic diseases associated with disorders of water homeostasis

Disorders of AVP secretion and action sometimes present as the first manifestation of a variety of different systemic diseases. It is prudent for the clinician to consider these causes in the differential diagnosis of hypoosmolar hyponatremia, polyuria and polydipsia, since recognizing the underlying disorder may affect treatment decisions, and intervention directed at the primary disorder often can reverse the abnormal water metabolism in these patients. Although much of the pathophysiology of these disorders is not understood completely, great progress has been made toward appreciating the complex and precise system involving thirst, AVP secretion, and renal responsiveness to AVP. Further investigation in this field likely will allow physicians to offer more effective and potent treatments in the future, such as the development of AVP V2 receptor antagonists for the treatment of SIADH [81] and edema-forming states [18, 109].

Severity prediction rules in community acquired pneumonia: a validation study

BACKGROUND

The British Thoracic Society (BTS) developed a rule (BTSr) based on severity criteria to predict short term mortality in adults admitted to hospital with community acquired pneumonia (CAP). However, neither the BTSr nor a recent modification of it (mBTSr) have been validated in the UK. A case-control study was conducted in a typical UK population to determine the clinical factors predictive of mortality and to assess the performance of these rules.

METHODS

Cases were drawn from all patients with CAP who died in 1997 in five large hospitals in the Mid Trent area. Controls were randomly selected from survivors. Factors associated with mortality were identified following review of medical case notes and performance of the severity prediction rules assessed.

RESULTS

Age >65 years, temperature <37 degrees C, respiratory rate >24 breaths/min, mental confusion, urea concentration of >7 mmol/l, sodium concentration of <135 mmol/l, and the presence of a pleural effusion, all determined on admission, were independently associated with in-hospital mortality on multivariate analysis. The BTSr was 52% sensitive and 79% specific in predicting death while the mBTSr displayed 66% sensitivity and 73% specificity.

CONCLUSIONS

The value of three of the four factors (presence of mental confusion, raised respiratory rate, raised urea) used in the mBTSr as predictors of mortality is confirmed. However, the BTSr and mBTSr did not perform as well in this validation study which included a high proportion (48%) of elderly patients (> or =75 years) compared with the derivation studies.

Hyponatraemia and the inappropriate ADH syndrome in pneumonia

We studied serum sodium, plasma osmolality and urinary sodium and osmolality on days 1, 3 and 5 of hospitalization of 100 children aged from 1 month to 12 years admitted with a diagnosis of pneumonia. Hyponatraemia (serum sodium concentration < or = 130 mmol/l) was found in 31 patients at the time of admission. The probable cause of hyponatraemia in 94% of cases was the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Symptoms and signs indicative of severe pneumonia were two to three times more frequent and the mean duration of tachypnoea, chest-wall retraction and hospital stay about one and a half times longer in children with hyponatraemia. Four children died (two on day 1, one on day 5 and one on day 8); all four had a serum sodium concentration < or = 125 mmol/l which persisted until death. Of the remaining 27 hyponatraemic children, serum sodium concentrations returned to normal on day 3 in 26, while in one hyponatraemia persisted until day 7. The recovery from hyponatraemia showed a good correlation with improvement in clinical signs of respiratory distress. The SIADH occurred in about one-third of the children hospitalized for pneumonia, and was associated with a more severe disease and a poorer outcome. Perhaps fluid restriction in these cases may improve the outcome.

Excessive secretion of antidiuretic hormone in infections with respiratory syncytial virus

The association between infections with respiratory syncytial virus and plasma concentrations of antidiuretic hormone was assessed in 48 patients who had been admitted to hospital. The mean (SEM) concentration of antidiuretic hormone was significantly raised in patients with bronchiolitis (9.3 (1.4) ng/l) compared with non-pulmonary respiratory syncytial virus infections that cause apnoea or upper respiratory tract symptoms (6.1 (1.7) ng/l). The highest concentrations of antidiuretic hormone were seen in patients receiving mechanical ventilation (18.0 (6.7) ng/l). There were no differences in mean serum sodium concentrations among the subgroups. Hypertranslucency on chest radiograph or an arterial carbon dioxide tension above 6.67 kPa were associated with a significantly higher concentration of antidiuretic hormone. Increased or normal maintenance fluid intake in children with pulmonary respiratory syncytial virus infections may cause the same symptoms of fluid overload as the syndrome of inappropriate secretion of antidiuretic hormone. Patients with pulmonary respiratory syncytial virus infection, hypertranslucency in chest radiograph, hypercapnia, or mechanical ventilation are at risk for raised concentrations of antidiuretic hormone. Restricted fluid intake and careful monitoring of fluid balance and plasma electrolyte concentrations are therefore necessary in these patients.

Does the stress of admission to an intensive care unit influence arginine vasopressin secretion and renal diluting ability?

The pathogenesis of excessive arginine vasopressin (AVP) release and hyponatraemia in euvolaemic intensive care unit (ICU) patients is poorly understood. Stress has frequently been proposed as a possible determinant, but its actual responsibility has not been adequately assessed. Therefore, water-load tests were prospectively performed in 11 patients admitted to the ICU for severe or potentially severe diseases, but who had no other condition which could result in excessive AVP release or impairment of renal diluting ability. Renal diluting ability was normal in 9 patients. Two patients exhibited very slight defects, which might be the consequence of subclinical haemodynamic alterations, since one had a pulmonary embolism and the other manifested a gastrointestinal haemorrhage just after the completion of the water load. Nevertheless, plasma AVP levels decreased in response to the water load in all the patients, resulting in a significant decrease in mean values. Plasma norepinephrine values were found to be elevated both before and after water loading. A highly significant correlation existed between the levels of norepinephrine and those of AVP measured before the load, but was lost after it. In addition, norepinephrine values were markedly elevated in two patients who exhibited strictly normal renal diluting abilities, and no correlation was found between plasma norepinephrine values and any parameter of renal water excretion. Our study shows that the stress of a serious illness and of admission to an ICU does not seem to interfere, by itself, with osmotic regulation of AVP secretion and renal diluting ability, and that sympathetic activation is not, under such circumstances, a predominant stimulus for AVP release.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered water metabolism in tuberculosis: role of vasopressin

PURPOSE

Patients with hyponatremia due to tuberculosis have shown variable responses to water loading in previous small studies, ranging from persistent antidiuresis to a normal diuresis. Although tuberculosis is considered a cause of the syndrome of inappropriate antidiuretic hormone secretion (SIADH), circulating vasopressin has been documented in only a few cases. We studied a larger group of patients to determine whether it can be suppressed by a short-term reduction in osmolality.

PATIENTS AND METHODS

Twenty-eight hyponatremic patients (mean age +/- SD: 40 +/- 10 years) with pulmonary or miliary tuberculosis underwent a clinical evaluation, measurement of blood and urine chemistry values, and (in 22) a water load of 20 mL/kg. Volume status was evaluated by urine sodium concentration, blood and urine urea nitrogen, and plasma renin activity. Endocrine, renal, and other recognized causes of SIADH were excluded.

RESULTS

All 22 patients exhibited a decline in urine osmolality and an increase in free water clearance after water loading. Water excretion was fully normal in seven of 22, with the remainder showing variable impairment of diluting ability and/or volume excreted. Plasma vasopressin, measured in 11 of 22 patients as well as in six others not subjected to water loading, was detectable despite hypo-osmolality in 16 of 17. Vasopressin levels declined after water loading, from 1.85 +/- 1.32 to 0.77 +/- 0.25 pg/mL (p less than 0.05). The majority of patients had the euthyroid sick syndrome but normal adrenal responses to cosyntropin. Although several patients had mild volume depletion when studied, this factor did not appear to explain the defect in water excretion. Hyponatremia resolved predictably within days to weeks of antituberculous therapy.

CONCLUSIONS

Circulating vasopressin remains detectable in hyponatremic patients with tuberculosis and is responsive to changes in osmolality. A downsetting of osmoregulation induced by active tuberculosis ("reset osmostat") could explain this abnormality, but we cannot exclude an unidentified non-osmotic stimulus that can be counteracted by water loading.