Evidence for fluid volume depletion in hyponatraemic patients with bacterial meningitis

Prevalence and fluid management of dehydration in children without diarrhoea admitted to Kenyan hospitals: a multisite observational study

OBJECTIVES

To examine the prevalence of dehydration without diarrhoea among admitted children aged 1-59 months and to describe fluid management practices in such cases.

DESIGN

A multisite observational study that used routine in-patient data collected prospectively between October 2013 and December 2018.

SETTINGS

Study conducted in 13 county referral hospitals in Kenya.

PARTICIPANTS

Children aged 1-59 months with admission or discharge diagnosis of dehydration but had no diarrhoea as a symptom or diagnosis. Children aged <28 days and those with severe acute malnutrition were excluded.

RESULTS

The prevalence of dehydration in children without diarrhoea was 3.0% (2019/68 204) and comprised 15.9% (2019/12 702) of all dehydration cases. Only 55.8% (1127/2019) of affected children received either oral or intravenous fluid therapy. Where fluid treatment was given, the volumes, type of fluid, duration of fluid therapy and route of administration were similar to those used in the treatment of dehydration secondary to diarrhoea. Pneumonia (1021/2019, 50.6%) and malaria (715/2019, 35.4%) were the two most common comorbid diagnoses. Overall case fatality in the study population was 12.9% (260/2019).

CONCLUSION

Sixteen per cent of children hospitalised with dehydration do not have diarrhoea but other common illnesses. Two-fifths do not receive fluid therapy; a regimen similar to that used in diarrhoeal cases is used in cases where fluid is administered. Efforts to promote compliance with guidance in routine clinical settings should recognise special circumstances where guidelines do not apply, and further studies on appropriate management for dehydration in the absence of diarrhoea are required.

Mechanism, spectrum, consequences and management of hyponatremia in tuberculous meningitis

Hyponatremia is the commonest electrolyte abnormality in hospitalized patients and is associated with poor outcome. Hyponatremia is categorized on the basis of serum sodium into severe (< 120 mEq/L), moderate (120-129 mEq/L) and mild (130-134mEq/L) groups. Serum sodium has an important role in maintaining serum osmolality, which is maintained by the action of antidiuretic hormone (ADH) secreted from the posterior pituitary, and natriuretic peptides such as atrial natriuretic peptide and brain natriuretic peptide. These peptides act on kidney tubules via the renin angiotensin aldosterone system. Hyponatremia <120mEq/L or a rapid decline in serum sodium can result in neurological manifestations, ranging from confusion to coma and seizure. Cerebral salt wasting (CSW) and syndrome of inappropriate secretion of ADH (SIADH) are important causes of hyponatremia in tuberculosis meningitis (TBM). CSW is more common than SIADH. The differentiation between CSW and SIADH is important because treatment of one may be detrimental for the other; evidence of hypovolemia in CSW and euvolemia or hypervolemia in SIADH is used for differentiation. In addition, evidence of dehydration, polyuria, negative fluid balance as assessed by intake output chart, weight loss, laboratory evidence and sometimes central venous pressure are helpful in the diagnosis of these disorders. Volume contraction in CSW may be more protracted than hyponatremia and may contribute to border zone infarctions in TBM. Hyponatremia should be promptly and carefully treated by saline and oral salt, while 3% saline should be used in severe hyponatremia with coma and seizure. In refractory patients with hyponatremia, fludrocortisone helps in early normalization of serum sodium without affecting polyuria or functional outcome. In SIADH, V2 receptor antagonist conivaptan or tolvaptan may be used if the patient is not responding to fluid restriction. Fluid restriction in SIADH has not been found to be beneficial in TBM and should be avoided.

Mechanism, spectrum, consequences and management of hyponatremia in tuberculous meningitis

Hyponatremia is the commonest electrolyte abnormality in hospitalized patients and is associated with poor outcome. Hyponatremia is categorized on the basis of serum sodium into severe (< 120 mEq/L), moderate (120-129 mEq/L) and mild (130-134mEq/L) groups. Serum sodium has an important role in maintaining serum osmolality, which is maintained by the action of antidiuretic hormone (ADH) secreted from the posterior pituitary, and natriuretic peptides such as atrial natriuretic peptide and brain natriuretic peptide. These peptides act on kidney tubules via the renin angiotensin aldosterone system. Hyponatremia <120mEq/L or a rapid decline in serum sodium can result in neurological manifestations, ranging from confusion to coma and seizure. Cerebral salt wasting (CSW) and syndrome of inappropriate secretion of ADH (SIADH) are important causes of hyponatremia in tuberculosis meningitis (TBM). CSW is more common than SIADH. The differentiation between CSW and SIADH is important because treatment of one may be detrimental for the other; evidence of hypovolemia in CSW and euvolemia or hypervolemia in SIADH is used for differentiation. In addition, evidence of dehydration, polyuria, negative fluid balance as assessed by intake output chart, weight loss, laboratory evidence and sometimes central venous pressure are helpful in the diagnosis of these disorders. Volume contraction in CSW may be more protracted than hyponatremia and may contribute to border zone infarctions in TBM. Hyponatremia should be promptly and carefully treated by saline and oral salt, while 3% saline should be used in severe hyponatremia with coma and seizure. In refractory patients with hyponatremia, fludrocortisone helps in early normalization of serum sodium without affecting polyuria or functional outcome. In SIADH, V2 receptor antagonist conivaptan or tolvaptan may be used if the patient is not responding to fluid restriction. Fluid restriction in SIADH has not been found to be beneficial in TBM and should be avoided.

Cerebral salt wasting in tuberculous meningitis: treatment with fludrocortisone

Three cases of cerebral salt wasting complicating tuberculous meningitis are described. Diagnosis was based on hyponatraemia associated with high urinary sodium excretion and inappropriately high urine output in the presence of dehydration. Treatment with fludrocortisone resulted in sodium and fluid homeostasis.

Renal salt-wasting syndrome in children with intracranial disorders

Hypotonic hyponatremia, a serious and recognized complication of any intracranial disorder, results from extra-cellular fluid volume depletion, inappropriate anti-diuresis or renal salt-wasting. The putative mechanisms by which intracranial disorders might lead to renal salt-wasting are either a disrupted neural input to the kidney or the elaboration of a circulating natriuretic factor. The key to diagnosis of renal salt-wasting lies in the assessment of extra-cellular volume status: the central venous pressure is currently considered the yardstick for measuring fluid volume status in subjects with intracranial disorders and hyponatremia. Approximately 110 cases have been reported so far in subjects ≤18 years of age (male: 63%; female: 37%): intracranial surgery, meningo-encephalitis (most frequently tuberculous) or head injury were the most common underlying disorders. Volume and sodium repletion are the goals of treatment, and this can be performed using some combination of isotonic saline, hypertonic saline, and mineralocorticoids (fludrocortisone). It is worthy of a mention, however, that some authorities contend that cerebral salt wasting syndrome does not exist, since this diagnosis requires evidence of a reduced arterial blood volume, a concept but not a measurable variable.

A case of cerebral salt-wasting syndrome associated with aseptic meningitis in an 8-year-old boy

Cerebral salt-wasting syndrome is a disorder in which excessive natriuresis and subsequent hyponatremic dehydration occur in patients with intracranial diseases. Cerebral salt-wasting syndrome often develops in patients with severe neurosurgical disorders, such as hydrocephalus, cerebral infarction, and tuberculous meningitis. Here, we report on the case of an 8-year-old boy with cerebral salt-wasting syndrome associated with aseptic meningitis. He showed mild developmental retardation and had a history of convulsion. Four days after his admission, cerebral salt-wasting syndrome abruptly started: natriuresis and hyponatremia gradually improved over 10 days. To the best of our knowledge, this is the first report on cerebral salt-wasting syndrome associated with clinically benign aseptic meningitis.

Why has oral rehydration for calves and children diverged: direct vs. indirect criteria of efficacy

Oral rehydration therapy (ORT) for acute diarrhoea has advanced in contrary directions in humans and animals; the unresolved question is whether this reflects species differences or a divergence in scientific outlook. This review suggests that the explanation lies in the fact that developments in veterinary ORT have the advantage of utilising more reliable criteria than those available from human patients. The dilemma for human ORT is that the validity of systematic reviews and meta-analyses are undermined when the underlying data only reflect crucial variables indirectly and unreliably. It is therefore possible that the approaches currently used to treat calves, which are radically different from those used by paediatricians, could potentially benefit children and the necessary additional research should be initiated. At a time when the value of animal models of human disease is frequently questioned, the benefits of being able to utilise disease models in the target species for clinical research deserve to be emphasised.

Hyponatremia in critically ill neurological patients

BACKGROUND

Hyponatremia is the most common and important electrolyte disorder encountered in the neurologic intensive care unit (NICU). Advances in our knowledge of the pathophysiological mechanisms at play in patients with acute neurologic disease have improved our understanding of this derangement.

REVIEW SUMMARY

Evaluation of hyponatremia requires a structured approach beginning with the measurement of serum and urine osmolalities. Most cases of hyponatremia in the NICU are associated with serum hypotonicity. Iatrogenic causes, most conspicuously inadequate tonicity of intravenous fluids, should be promptly identified and removed when possible. Two main mechanisms are responsible for most non-iatrogenic cases of hyponatremia in patients with neurologic or neurosurgical disease: inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting syndrome (CSW). Distinction between these two syndromes may be difficult and must be based on an accurate assessment of the patient's volume status. SIADH is associated with normal or slightly expanded volume status and should be treated with fluid restriction. Patients with CSW are hypovolemic and require adequate fluid and sodium replacement. Correction of hyponatremia should not exceed 8 to 10 mmol/L over any 24-hour period to avoid the risk of osmotic demyelination.

CONCLUSIONS

Hyponatremia may complicate the clinical course of many acute neurologic and neurosurgical disorders. It is most often iatrogenic causes, CSW, or SIADH. Physicians working with critically ill neurologic patients should be familiar with management strategies addressing these underlying pathophysiological mechanisms.

Diagnosis and treatment of bacterial meningitis

This review focuses on recent advances of topical interest regarding the diagnosis and treatment of common causes of bacterial meningitis occurring in children beyond the neonatal period. Tuberculous meningitis is beyond the scope of this review.

Controversies in the management of bacterial meningitis

Bacterial meningitis is an important infection of childhood with significant morbidity and mortality, and clinicians are faced with controversies over steroid use and fluid restriction in its initial management because the standard of practice is not clear. A 1999 survey of paediatric infectious diseases specialists demonstrated that only 56% of respondents recommended dexamethasone for Haemophilus influenzae type b meningitis and only 34% recommended dexamethasone for Streptococcus pneumoniae meningitis, despite recommendations for dexamethasone in the 1997 Red Book. The present article illustrates a typical case presentation of bacterial meningitis, and discusses dexamethasone use and fluid restriction. The use of intravenous fluid therapy is also reviewed, based on results from the single prospective randomized clinical trial in this area.

Acute symptomatic hyponatremia and cerebral salt wasting after head injury: an important clinical entity

Hyponatremia is a well known complication of traumatic and nontraumatic cerebral injury, often related to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Nonetheless, it also can be associated with a different entity, the syndrome of cerebral salt wasting (CSW). The authors report the case of a 4.5-year-old boy presenting with major head injury who at day 6 after admission had generalized tonic-clonic seizures caused by severe acute hyponatremia (serum sodium level, 119 mmol/L) and signs of dehydration. Despite initial isotonic rehydration, hyponatremia persisted because of excessive renal salt losses and concomitant enormous water losses, necessitating increasing amounts of sodium, up to 160 mmol/kg/d, and large amounts of intravenous fluids, up to 27 L/d. Highly increased levels of atrial natriuretic peptide (ANP) confirmed the diagnosis of CSW. The occurrence of a CSW has to be recognized early in the clinical course for adequate treatment and remains one of the important differential diagnosis of SIADH in hyponatremic states in patients with cerebral disorders, especially after head injury.