Désordres hydroélectrolytiques des agressions cérébrales : mécanismes et traitements

Acute kidney injury after brain injury: does it exist?

Acute kidney injury (AKI) is frequent after cerebral insults, with an incidence close to 10% in both traumatic brain injury (TBI) and cerebrovascular disease. AKI in this context has substantial impact on mortality and neurological outcome. Numerous factors may play a role in the development of AKI after brain injury: intravascular volume depletion, raised-intra-abdominal pressure, rhabdomyolysis or sepsis in TBI; age, ischemic heart disease or arteriosclerotic disease in stroke. However, brain-kidney crosstalk mechanisms are complex and there remains a strong rationale for a causal relationship between brain and kidney injury. Cerebral lesions might alter renal function through a neuro-endocrine pathway combining sympathetic system, renin-angiotensin-aldosterone and glucocorticoid activation. Altogether these systems impair renal autoregulation ultimately leading to AKI. In addition, cerebral lesions might lead to a systemic inflammatory response making the kidney vulnerable for dysfunction. Indeed, inflammation and immune system activation are core mechanisms for the development of AKI. Last, direct lesions of specific area of the brain might lead to vasomotor changes and AKI. In this work, we reviewed the epidemiology of AKI after brain injury and examine potential mechanisms suggesting a causal relationship between these two entities.

Management of Intracranial Pressure Part II: Nonpharmacologic Interventions

Pharmacologic and nonpharmacologic interventions are available to treat patients who experience serious elevations in intracranial pressure (ICP). In some cases, patients may experience ICP that is refractory to treatment. Significant negative effects on cerebral blood flow, tissue oxygenation, and cerebral metabolism occur as a result of intracranial hypertension, leading to secondary brain injury. In part 2 of this series, nonpharmacologic interventions for ICP and ICP refractory to treatment are discussed. Interventions include neurologic monitoring (bedside assessment and multimodal monitoring), ventilatory support, fluid and electrolyte maintenance, targeted temperature management, and surgical intervention. Technology is always evolving, and the focus of multimodal monitoring here includes devices to monitor ICP, brain tissue oxygen tension, and cerebral blood flow and cerebral microdialysis monitors. Nursing care of these patients includes perspicacious assessment and integration of data, monitoring ventilatory and hemodynamic functioning, and appropriate patient positioning. Nurses must collaborate with the interprofessional care team to ensure favorable patient outcomes while utilizing an evidence-based guideline for the management of ICP.

Hypochloremia in Patients with Severe Traumatic Brain Injury: A Possible Risk Factor for Increased Mortality

OBJECTIVE

To determine association between electrolyte disturbances and mortality in patients with severe traumatic brain injury.

METHODS

Medical records of patients with severe traumatic brain injury and Glasgow Coma Scale score <8 and electrolyte alterations were reviewed in a retrospective cohort study. Electrolyte levels were analyzed to establish an association between patients who died and patients who survived. Bivariate analysis was performed using χ² test with a statistical reliability of 95% for categorical variables. Analysis for electrolyte changes to determine association with mortality was performed using χ² test with multiple comparisons. Logistic regression was performed between the electrolyte alterations and their association with mortality. The reliability of statistical tests was 95%.

RESULTS

There was a significant relationship between hypochloremia and increased risk of mortality in 23.1% of deceased patients (P = 0.03). Furthermore, there was a significant correlation with age (P < 0.01) and with the Acute Physiology and Chronic Health Evaluation APACHE II (P < 0.01).

CONCLUSIONS

Hypochloremia could be an important prognostic factor to determine mortality risk and to improve treatment in patients with severe traumatic brain injury.

[Hormonal dysnatremia]

Because of antidiuretic hormone (ADH) disorder on production or function we can observe dysnatremia. In the absence of production by posterior pituitary, central diabetes insipidus (DI) occurs with hypernatremia. There are hereditary autosomal dominant, autosomal recessive or X- linked forms. When ADH is secreted but there is an alteration on his receptor AVPR2, it is a nephrogenic diabetes insipidus in acquired or hereditary form. We can make difference on AVP levels and/or on desmopressine response which is negative in nephrogenic forms. Hyponatremia occurs when there is an excess of ADH production: it is a euvolemic hypoosmolar hyponatremia. The most frequent etiology is SIADH (syndrome of inappropriate secretion of ADH), a diagnostic of exclusion which is made after eliminating corticotropin deficiency and hypothyroidism. In case of brain injury the differential diagnosis of cerebral salt wasting (CSW) syndrome has to be discussed, because its treatment is perfusion of isotonic saline whereas in SIADH, the treatment consists in administration of hypertonic saline if hyponatremia is acute and/or severe. If not, fluid restriction demeclocycline or vaptans (antagonists of V2 receptors) can be used in some European countries. Four types of SIADH exist; 10 % of cases represent not SIADH but SIAD (syndrome of inappropriate antidiuresis) due to a constitutive activation of vasopressin receptor that produces water excess. c 2013 Published by Elsevier Masson SAS.

Balanced versus chloride-rich solutions for fluid resuscitation in brain-injured patients: a randomised double-blind pilot study

INTRODUCTION

We sought to investigate whether the use of balanced solutions reduces the incidence of hyperchloraemic acidosis without increasing the risk for intracranial hypertension in patients with severe brain injury.

METHODS

We conducted a single-centre, two-arm, randomised, double-blind, pilot controlled trial in Nantes, France. Patients with severe traumatic brain injury (Glasgow Coma Scale score ≤8) or subarachnoid haemorrhage (World Federation of Neurosurgical Society grade III or higher) who were mechanically ventilated were randomised within the first 12 hours after brain injury to receive either isotonic balanced solutions (crystalloid and hydroxyethyl starch; balanced group) or isotonic sodium chloride solutions (crystalloid and hydroxyethyl starch; saline group) for 48 hours. The primary endpoint was the occurrence of hyperchloraemic metabolic acidosis within 48 hours.

RESULTS

Forty-two patients were included, of whom one patient in each group was excluded (one consent withdrawn and one use of forbidden therapy). Nineteen patients (95%) in the saline group and thirteen (65%) in the balanced group presented with hyperchloraemic acidosis within the first 48 hours (hazard ratio = 0.28, 95% confidence interval [CI] = 0.11 to 0.70; P = 0.006). In the saline group, pH (P = .004) and strong ion deficit (P = 0.047) were lower and chloraemia was higher (P = 0.002) than in the balanced group. Intracranial pressure was not different between the study groups (mean difference 4 mmHg [-1;8]; P = 0.088). Seven patients (35%) in the saline group and eight (40%) in the balanced group developed intracranial hypertension (P = 0.744). Three patients (14%) in the saline group and five (25%) in the balanced group died (P = 0.387).

CONCLUSIONS

This study provides evidence that balanced solutions reduce the incidence of hyperchloraemic acidosis in brain-injured patients compared to saline solutions. Even if the study was not powered sufficiently for this endpoint, intracranial pressure did not appear different between groups.

TRIAL REGISTRATION

EudraCT 2008-004153-15 and NCT00847977.