High incidence of hyponatremia in patients with ruptured anterior communicating artery aneurysms

Prevention and Correction of Dysnatremia After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Dysnatremia occurs commonly in patients with aneurysmal subarachnoid hemorrhage (aSAH). The mechanisms for development of sodium dyshomeostasis are complex, including the cerebral salt-wasting syndrome, the syndrome of inappropriate secretion of antidiuretic hormone, diabetes insipidus. Iatrogenic occurrence of altered sodium levels plays a role, as sodium homeostasis is tightly linked to fluid and volume management.

METHODS

Narrative review of the literature.

RESULTS

Many studies have aimed to identify factors predictive of the development of dysnatremia, but data on associations between dysnatremia and demographic and clinical variables are variable. Furthermore, although a clear relationship between serum sodium serum concentrations and outcomes has not been established-poor outcomes have been associated with both hyponatremia and hypernatremia in the immediate period following aSAH and set the basis for seeking interventions to correct dysnatremia. While sodium supplementation and mineralocorticoids are frequently administered to prevent or counter natriuresis and hyponatremia, evidence to date is insufficient to gauge the effect of such treatment on outcomes.

CONCLUSIONS

In this article, we reviewed available data and provide a practical interpretation of these data as a complement to the newly issued guidelines for management of aSAH. Gaps in knowledge and future directions are discussed.

Understanding anterior communicating artery aneurysms: A bibliometric analysis of top 100 most cited articles

Bibliometric analysis is of paramount importance in assessing the research impact wherein studies are ranked on the basis of citations received. It also brings out the excellent contribution of authors and journals in adding evidence for future research. This study aimed at evaluating the top 100 most cited articles on anterior communicating artery (ACoA) Aneurysms. Scopus database was searched using title specific search for the aneurysm of ACoA and top 100 most cited articles along with their authors, author IDs, affiliated institutions, countries and funding bodies were identified. Search yielded 841 articles and top 100 articles were identified to include in this analysis which secured 5615 citations. Citations per year was also calculated to minimize the risk of bias. Maximum citations by any article were 242. The United States was the major contributor to the number of articles while Kessler Institute for Rehabilitation became the highest contributing institution. DeLuca J proved to be a pioneer in this specialized area as he penned 6 studies being first author in 4 of them, making him the most frequent author. National Institutes of Health and the U.S. Department of Health and Human Services were the main funding bodies. Subcategory analysis revealed, 50% studies provided evidence for the treatment and the surgical outcome of the aneurysm. Studies like these can aid in better neurological and neurosurgical management in decision making of ACoA aneurysm.

Changes in endogenous daytime melatonin levels after aneurysmal subarachnoid hemorrhage - Preliminary findings from an observational cohort study

INTRODUCTION

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with early and delayed brain injury due to several underlying and interrelated processes, which include inflammation, oxidative stress, endothelial, and neuronal apoptosis. Treatment with melatonin, a cytoprotective neurohormone with anti-inflammatory, anti-oxidant and anti-apoptotic effects, has been shown to attenuate early brain injury (EBI) and to prevent delayed cerebral vasospasm in experimental aSAH models. Less is known about the role of endogenous melatonin for aSAH outcome and how its production is altered by the pathophysiological cascades initiated during EBI. In the present observational study, we analyzed changes in melatonin levels during the first three weeks after aSAH.

MATERIALS AND METHODS

Daytime (from 11:00 am to 05:00 pm) melatonin levels were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples obtained from 30 patients on the day of aSAH onset (d₀) and in five pre-defined time intervals during the early (d_1-4), critical (d_5-8, d_9-12, d_13-15) and late (d_16-21) phase. Perioperative daytime melatonin levels determined in 30 patients who underwent elective open aortic surgery served as a control for the acute effects of surgical treatment on melatonin homeostasis.

RESULTS

There was no difference between serum melatonin levels measured in the control patients and on the day of aSAH onset (p = 0.664). However, aSAH was associated with a sustained up-regulation that started during the critical phase (d_9-12) and progressed to the late phase (d_16-21), during which almost 80% of the patients reached daytime melatonin levels above 5 pg/ml. In addition, subgroup analyses revealed higher melatonin levels on d_5-8 in patients with a poor clinical status on admission (p = 0.031), patients with anterior communicating artery aneurysms (p = 0.040) and patients without an external ventricular drain (p = 0.018), possibly pointing to a role of hypothalamic dysfunction.

CONCLUSION

Our observations in a small cohort of patients provide first evidence for a delayed up-regulation of circulatory daytime melatonin levels after aSAH and a role of aneurysm location for higher levels during the critical phase. These findings are discussed in terms of previous results about stress-induced melatonin production and the role of hypothalamic and brainstem involvement for melatonin levels after aSAH.

An overview of pharmacotherapy for cerebral vasospasm and delayed cerebral ischemia after subarachnoid hemorrhage

Introduction: Survival from aneurysmal subarachnoid hemorrhage has increased in the past few decades. However, functional outcome after subarachnoid hemorrhage is still suboptimal. Delayed cerebral ischemia (DCI) is one of the major causes of morbidity.Areas covered: Mechanisms underlying vasospasm and DCI after aneurysmal subarachnoid hemorrhage and pharmacological treatment are summarized in this review.Expert opinion: Oral nimodine, an L-type dihydropyridine calcium channel blocker, is the only FDA-approved drug for the prevention and treatment of neurological deficits after aneurysmal subarachnoid hemorrhage. Fasudil, a potent Rho-kinase inhibitor, has also been shown to improve the clinical outcome and has been approved in some countries for use in patients with aneurysmal subarachnoid hemorrhage. Although other drugs, including nicardipine, cilostazol, statins, clazosentan, magnesium and heparin, have been expected to have beneficial effects on DCI, there has been no convincing evidence supporting the routine use of those drugs in patients with aneurysmal subarachnoid hemorrhage in clinical practice. Further elucidation of the mechanisms underlying DCI and the development of effective therapeutic strategies for DCI, including combination therapy, are necessary to further improve the functional outcome and mortality after subarachnoid hemorrhage.

Hyponatraemia and hypernatraemia: Disorders of Water Balance in Neurosurgery

Disorders of tonicity, hyponatraemia and hypernatraemia, are common in neurosurgical patients. Tonicity is sensed by the circumventricular organs while the volume state is sensed by the kidney and peripheral baroreceptors; these two signals are integrated in the hypothalamus. Volume is maintained through the renin-angiotensin-aldosterone axis, while tonicity is defended by arginine vasopressin (antidiuretic hormone) and the thirst response. Edelman found that plasma sodium is dependent on the exchangeable sodium, potassium and free-water in the body. Thus, changes in tonicity must be due to disproportionate flux of these species in and out of the body. Sodium concentration may be measured by flame photometry and indirect, or direct, ion-sensitive electrodes. Only the latter method is not affected by changes in plasma composition. Classification of hyponatraemia by the volume state is imprecise. We compare the tonicity of the urine, given by the sodium potassium sum, to that of the plasma to determine the renal response to the dysnatraemia. We may then assess the activity of the renin-angiotensin-aldosterone axis using urinary sodium and fractional excretion of sodium, urate or urea. Together, with clinical context, these help us determine the aetiology of the dysnatraemia. Symptomatic individuals and those with intracranial catastrophes require prompt treatment and vigilant monitoring. Otherwise, in the absence of hypovolaemia, free-water restriction and correction of any reversible causes should be the mainstay of treatment for hyponatraemia. Hypernatraemia should be corrected with free-water, and concurrent disorders of volume should be addressed. Monitoring for overcorrection of hyponatraemia is necessary to avoid osmotic demyelination.

The circle of Willis revisited: Forebrain dehydration sensing facilitated by the anterior communicating artery: How hemodynamic properties facilitate more efficient dehydration sensing in amniotes

We hypothesize that threat of dehydration provided selection pressure for the evolutionary emergence and persistence of the anterior communicating artery (ACoA - the inter-arterial connection that completes the Circle of Willis) in early amniotes. The ACoA is a hemodynamically insignificant artery, but, as we argue in this paper, its privileged position outside the blood-brain barrier gives it a crucial sensing function for the osmolarity of the blood against the background of the rest of the brain, which efficiently protects itself from dehydration. Till now, the questions of why the ACoA evolved, and what its physiological function is, have remained unsatisfactorily answered. The traditional view-that the ACoA serves as a collateral source of vascularization in case of arterial stenosis-is anthropocentric, and not in accordance with principles of natural selection that apply more generally. Diseases underlying arterial stenosis are associated with aging and the human lifestyle, so this cannot explain why the ACoA formed hundreds of millions of years ago and persisted in amniotes to this day. The peculiar hemodynamic properties of the ACoA could be selected traits that allowed for more efficient forebrain detection of dehydration and complex behavioral responses to water loss, a major advantage in the survival of early amniotes. This hypothesis also explains insufficient hydration often seen in elderly humans.

Hyponatremia After Spontaneous Aneurysmal Subarachnoid Hemorrhage-A Prospective Observational Study

OBJECTIVE

Hyponatremia has been frequently observed after aneurysmal subarachnoid hemorrhage (SAH), and some data have suggested a correlation with symptomatic cerebral vasospasm and poor outcomes. The present prospective study investigated sodium and water disturbances after aneurysmal SAH with regard to symptomatic vasospasm and patient outcomes.

METHODS

Data from all patients with aneurysmal SAH treated in our department during a 2-year period were collected. Daily natriuresis, sodium levels, water balance, and serum and urine osmolality were measured at 4 different points: day 1 of admission or bleeding, day 3, day 7, and day 14-21 or discharge. The clinical parameters (i.e., Hunt and Hess grade, aneurysm location and treatment, onset of vasospasm) were reviewed. The patients' outcome was assessed using the Glasgow outcome score and modified Rankin scale.

RESULTS

A total of 101 patients (70 women; median age, 52 years) were enrolled in the present study. Of these 101 patients, 59.4% had a good grade SAH (Hunt and Hess grade 1-3). The most common aneurysm location was the anterior communicating artery (37%). The results from an electrolyte analysis were available for ≤91 patients at days 1 and 78 at discharge. In 33 patients (32.7%), hyponatremia had been diagnosed at any time point. Hyponatremia was most frequently observed at day 1 and later at days 7-10. A location in the anterior communicating artery resulted in hyponatremia more frequently only at day 1 (P = 0.007). The main causes of hyponatremia were cerebral salt-wasting syndrome (early onset) and syndrome of inappropriate antidiuretic hormone secretion (early and late onset).

CONCLUSION

Distinguishing early- and late-onset hyponatremia is of major relevance, because different therapeutic approaches are required. Only hyponatremia at discharge resulted in less favorable outcomes.

Korean Clinical Practice Guidelines for Aneurysmal Subarachnoid Hemorrhage

Despite advancements in treating ruptured cerebral aneurysms, an aneurysmal subarachnoid hemorrhage (aSAH) is still a grave cerebrovascular disease associated with a high rate of morbidity and mortality. Based on the literature published to date, worldwide academic and governmental committees have developed clinical practice guidelines (CPGs) to propose standards for disease management in order to achieve the best treatment outcomes for aSAHs. In 2013, the Korean Society of Cerebrovascular Surgeons issued a Korean version of the CPGs for aSAHs. The group researched all articles and major foreign CPGs published in English until December 2015 using several search engines. Based on these articles, levels of evidence and grades of recommendations were determined by our society as well as by other related Quality Control Committees from neurointervention, neurology and rehabilitation medicine. The Korean version of the CPGs for aSAHs includes risk factors, diagnosis, initial management, medical and surgical management to prevent rebleeding, management of delayed cerebral ischemia and vasospasm, treatment of hydrocephalus, treatment of medical complications and early rehabilitation. The CPGs are not the absolute standard but are the present reference as the evidence is still incomplete, each environment of clinical practice is different, and there is a high probability of variation in the current recommendations. The CPGs will be useful in the fields of clinical practice and research.

Risk of Hyponatremia in Patients with Aneurysmal Subarachnoid Hemorrhage Treated with Exogenous Vasopressin Infusion

BACKGROUND

Vasopressin is one of the vasopressors used to augment blood pressure in subarachnoid hemorrhage (SAH) patients with clinically significant vasospasm. The purpose of the present study was to determine whether the administration of vasopressin to a population of SAH patients was an independent predictor of developing hyponatremia.

METHODS

A retrospective review on the health records of 106 patients admitted to the University of Alberta Hospital Neurosciences ICU, Edmonton AB, Canada, with SAH from June 2013 to December 2015 was conducted. Serum sodium changes in patients receiving vasoactive drugs were compared. In addition, independent predictors for hyponatremia (Na < 135 mmol/L) were determined using a multivariate logistic regression model.

RESULTS

Patients treated with vasopressin in addition to other vasoactive drugs had significantly higher sodium changes compared to those treated with other vasoactive drugs (-4.7 ± 6 vs -0.1 ± 2.4 mmol/L, respectively, p value 0.001). Hyponatremia occurred in 14 patients (70 %) treated with vasopressin, 10 patients (44 %) treated with vasoactive drugs other than vasopressin (p value 0.081), and 24 patients (38 %) who did not receive any vasoactive drug (p value 0.013). In multivariate logistic regression analysis, when adjusting for disease severity, age, sex, aneurysm location, and treatment, vasopressin was associated with hyponatremia (OR 3.58, 95 % CI, 1.02-12.5, p value 0.046).

CONCLUSIONS

The results of the present study suggest that hyponatremia may be more common in SAH patients treated with exogenous vasopressin compared to those who did not receive it. Serum sodium should be monitored closely when vasopressin is being used in the SAH population. Further studies are needed to confirm the effect of exogenous vasopressin on serum sodium levels in SAH populations.

Polyuria and cerebral vasospasm after aneurysmal subarachnoid hemorrhage

Background

Natriuresis with polyuria is common after aneurysmal subarachnoid hemorrhage (aSAH). Previous studies have shown an increased risk of symptomatic cerebral vasospasm or delayed cerebral ischemia (DCI) in patients with hyponatremia and/or the cerebral salt wasting syndrome (CSW). However, natriuresis may occur in the absence of hyponatremia or hypovolemia and it is not known whether the increase in DCI in patients with CSW is secondary to a concomitant hypovolemia or because the physiology that predisposes to natriuretic peptide release also predisposes to cerebral vasospasm. Therefore, we investigated whether polyuria per se was associated with vasospasm and whether a temporal relationship existed.

Methods

A retrospective review of patients with aSAH was performed. Exclusion criteria were admission more than 48 h after aneurysmal rupture, death within 5 days, and the development of diabetes insipidus or acute renal failure. Polyuria was defined as >6 liters of urine in a 24 h period. Vasospasm was defined as a mean velocity > 120 m/s on Transcranial Doppler Ultrasonography (TCDs) or by evidence of vasospasm on computerized tomography (CT) or catheter angiography. Multivariable logistic regression was performed to assess the relationship between polyuria and vasospasm.

Results

95 patients were included in the study. 51 had cerebral vasospasm and 63 met the definition of polyuria. Patients with polyuria were significantly more likely to have vasospasm (OR 4.301, 95 % CI 1.378–13.419) in multivariate analysis. Polyuria was more common in younger patients (52 vs 68, p <.001) but did not impact mortality after controlling for age and disease severity. The timing of the development of polyuria was clustered around the diagnosis of vasospasm and patients with polyuria developed vasospasm faster than those without polyuria.

Conclusions

Polyuria is common after aSAH and is significantly associated with cerebral vasospasm. The development of polyuria may be temporally related to the development of vasospasm. An increase in urine volume may be a useful clinical predictor of patients at risk for vasospasm.

Diagnosis and Management of Hyponatremia in Patients with Aneurysmal Subarachnoid Hemorrhage

Hyponatremia is the most common, clinically-significant electrolyte abnormality seen in patients with aneurysmal subarachnoid hemorrhage. Controversy continues to exist regarding both the cause and treatment of hyponatremia in this patient population. Lack of timely diagnosis and/or providing inadequate or inappropriate treatment can increase the risk of morbidity and mortality. We review recent literature on hyponatremia in subarachnoid hemorrhage and present currently recommended protocols for diagnosis and management.

Randomized, double-blind trial of the effect of fluid composition on electrolyte, acid-base, and fluid homeostasis in patients early after subarachnoid hemorrhage

BACKGROUND

Hyper- and hyponatremia are frequently observed in patients after subarachnoidal hemorrhage, and are potentially related to worse outcome. We hypothesized that the fluid regimen in these patients is associated with distinct changes in serum electrolytes, acid-base disturbances, and fluid balance.

METHODS

Thirty-six consecutive patients with SAH were randomized double-blinded to either normal saline and hydroxyethyl starch dissolved in normal saline (Voluven(®); saline) or balanced crystalloid and colloid solutions (Ringerfundin(®) and Tetraspan(®); balanced, n = 18, each) for 48 h. Laboratory samples and fluid balance were evaluated at baseline and at 24 and 48 h.

RESULTS

Age [57 ± 13 years (mean ± SD; saline) vs. 56 ± 12 years (balanced)], SAPS II (38 ± 16 vs. 34 ± 17), Hunt and Hess [3 (1-4) (median, range) vs. 2 (1-4)], and Fischer scores [3.5 (1-4) vs. 3.5 (1-4)] were similar. Serum sodium, chloride, and osmolality increased in saline only (p ≤ 0.010, time-group interaction). More patients in saline had Cl >108 mmol/L [16 (89 %) vs. 8 (44 %); p = 0.006], serum osmolality >300 mosmol/L [10 (56 %) vs. 2 (11 %); p = 0.012], a base excess <-2 [12 (67 %) vs. 2 (11 %); p = 0.001], and fluid balance >1,500 mL during the first 24 h [11 (61 %) vs. 5 (28 %); p = 0.046]. Hyponatremia and hypo-osmolality were not more frequent in the balanced group.

CONCLUSIONS

Treatment with saline-based fluids resulted in a greater number of patients with hyperchloremia, hyperosmolality, and positive fluid balance >1,500 mL early after SAH, while administration of balanced solutions did not cause more frequent hyponatremia or hypo-osmolality. These results should be confirmed in larger studies.

Clinical and predictive significance of hyponatremia after aneurysmal subarachnoid hemorrhage

OBJECTIVE

Hyponatremia after SAH was the object of several studies with conflicting results. The aim of this study was to determine a predictive correlation of hyponatremia with delayed cerebral ischemia (DCI) and poor clinical outcome.

MATERIAL AND METHODS

We have used a retrospective hospital chart review of 82 patients with SAH treated from August 2008 to August 2010. Patients were divided into hyponatremia and normonatremia groups. Hyponatremia was defined as serum sodium level <135 mmol/l. Information compared and analyzed included demographics, preoperative neurological status, aneurysm characteristics, postoperative intensive care, duration of stay, DCI and clinical outcome at hospital discharge. P<0.05 was considered significant.

RESULTS

Thirty-two patients with SAH (39%) developed hyponatremia. In that group we had a significantly higher WFNS score at admission (p=0.03) and longer duration of stay in intensive care (p=0.001). DCI with transit or definitive deficit included 20 patients (62%) in the hyponatremia group, and 19 patients (38%) in the normonatremia group (p=0.03). Binary enter logistic regression revealed a significant correlation of hyponatremia with DCI (p=0.03) and poor clinical outcome (p=0.001).

CONCLUSION

This result revealed a possible use of hyponatremia as an additional predictor of developing DCI and poor clinical outcome.

Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association

PURPOSE

The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

A formal literature search of MEDLINE (November 1, 2006, through May 1, 2010) was performed. Data were synthesized with the use of evidence tables. Writing group members met by teleconference to discuss data-derived recommendations. The American Heart Association Stroke Council's Levels of Evidence grading algorithm was used to grade each recommendation. The guideline draft was reviewed by 7 expert peer reviewers and by the members of the Stroke Council Leadership and Manuscript Oversight Committees. It is intended that this guideline be fully updated every 3 years.

RESULTS

Evidence-based guidelines are presented for the care of patients presenting with aSAH. The focus of the guideline was subdivided into incidence, risk factors, prevention, natural history and outcome, diagnosis, prevention of rebleeding, surgical and endovascular repair of ruptured aneurysms, systems of care, anesthetic management during repair, management of vasospasm and delayed cerebral ischemia, management of hydrocephalus, management of seizures, and management of medical complications.

CONCLUSIONS

aSAH is a serious medical condition in which outcome can be dramatically impacted by early, aggressive, expert care. The guidelines offer a framework for goal-directed treatment of the patient with aSAH.

ICU management of aneurysmal subarachnoid hemorrhage

INTRODUCTION

Aneurysmal subarachnoid hemorrhage (SAH) has very high morbidity and mortality rates. Optimal intensive care unit (ICU) management requires knowledge of the potential complications that occur in this patient population.

METHODS

Review of the ICU management of SAH. Level of evidence for specific recommendations is provided.

RESULTS

Grading scales utilizing clinical factors and brain imaging studies can help in determining prognosis and are reviewed. Misdiagnosis of SAH is fairly common so the clinical symptoms and signs of SAH are summarized. The ICU management of SAH is discussed beginning with a focus on avoiding aneurysm re-rupture and securing the aneurysm, followed by a review of the neurologic and medical complications that may occur after the aneurysm is secured. Detailed treatment strategies and areas of current and future research are reviewed.

CONCLUSIONS

The ICU management of the patient with SAH can be particularly challenging and requires an awareness of all potential neurologic and medical complications and their urgent treatments.

Critical care management of subarachnoid hemorrhage

Successful critical care management of patients with aneurysmal subarachnoid hemorrhage (SAH) requires a thorough understanding of the disease and its complications and a familiarity with modern multimodality neuromonitoring technology. This article reviews the natural history of aneurysmal SAH and strategies for disease management in the acute setting, including available tools for monitoring brain function. Intensive care management of patients with SAH focuses on prevention of further neurologic injury. Aneurysmal rebleeding, hydrocephalus, seizures, and delayed ischemic injury represent major threats. There is increasing awareness of extracerebral complications, including electrolyte disturbances (eg, cerebral salt wasting) and cardiac dysfunction. Prompt recognition and treatment of these disorders maximizes the odds of a good functional outcome. Technologic advances hold the promise of improved detection and treatment of secondary neurologic insults.

Critical care management of subarachnoid hemorrhage

Successful critical care management of patients with aneurysmal subarachnoid hemorrhage requires a thorough understanding of the disease and its complications and a familiarity with modern multimodality neuromonitoring technology. This article reviews the natural history of aneurysmal subarachnoid hemorrhage and strategies for disease management in the acute setting. Available tools for monitoring brain function are discussed.

Molecular mechanisms of cerebral vasospasm following aneurysmal SAH

Cerebral vasospasm following aneurysmal vasospasm has been the subject of intensive research. However the underlying pathophysiological mechanisms remain obscure. This article should summarize the present state concerning smooth muscle contraction, endothelial dysfunction, inflammatory changes, gene expression, in the genesis of vasospasm following aneurysmal subarachnoid hemorrhage.

The systemic implications of aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is analogous to a pathophysiological watershed, disrupting brain integrity and function and precipitating an array of systemic derangements including cardiovascular, respiratory, endocrine, hematological, and immune dysfunction. Extracerebral organ dysfunction is closely linked to the magnitude of the primary neurological insult, suggesting neurogenic, neuroendocrine and neuroimmunomodulatory mechanisms. Systemic organ involvement is associated with increased mortality and neurological impairment, even after adjustment for other outcome predictors such as the severity of the initial neurological injury. This may be a reflection of secondary brain injury precipitated by hypoxemia, circulatory failure, fever, or hyperglycemia, all of which have been linked to adverse clinical outcomes. Interventions to avert or reverse these and other perturbations need to be tested in clinical trials as they represent opportunities to improve survival and neurological recovery in patients with SAH.

Arginine vasopressin as a supplementary vasopressor in refractory hypertensive, hypervolemic, hemodilutional therapy in subarachnoid hemorrhage

INTRODUCTION

Hypertensive, hypervolemic, and hemodilutional (HHH) therapy for vasospasm in subarachnoid hemorrhage (SAH) refractory to phenylephrine requires high doses of catecholamines, leading to adverse adrenergic effects. Arginine vasopressin (AVP) has been shown to stabilize advanced shock states while facilitating reduction of catecholamine doses, but its use has never been reported in SAH. In this retrospective study, we investigated the hemodynamic effects and feasibility of supplementary AVP in refractory HHH therapy in SAH.

METHODS

Hemodynamic response (mean arterial pressure [MAP], heart rate, central venous pressure, cardiac index, systemic vascular resistance index, and end diastolic volume index) to a supplementary AVP infusion (0.01-0.04 IU/minute) was recorded within the first 24 hours in 22 patients. Secondary endpoints (serum sodium concentration, incidence of vasospasm, and intracranial pressure [ICP]) were compared to controls on HHH therapy with phenylephrine alone.

RESULTS

After initiation of AVP, MAP increased significantly compared to baseline. Phenylephrine doses decreased significantly, whereas other hemodynamic parameters remained stable. Serum sodium concentrations decreased similarly in both groups (-5 +/- 7 mmol/L versus -6 +/- 4 mmol/L; p = 0.25). No detrimental effects on vasospasm incidence or ICP and cerebral perfusion pressure were noted.

CONCLUSION

AVP may be considered as an alternative supplementary vasopressor in refractory HHH therapy with phenylephrine in SAH. Although we did not observe any deleterious effect of AVP on cerebral circulation, close observation for development of cerebral vasospasm should be undertaken, until it is clearly demonstrated that AVP has no adverse effects on regional cerebral blood flow and symptomatic cerebral vasospasm. Our limited data suggest that low-dose AVP does not cause brain edema, but further study is merited.

Hyponatremia in the neurosurgical patient: epidemiology, pathophysiology, diagnosis, and management

OBJECTIVE

Hyponatremia is an important and common electrolyte disorder in critically ill neurosurgical patients that has been reported in association with a number of different primary diagnoses. The correct diagnosis of the pathophysiological cause is vital because it dramatically alters the treatment approach.

METHODS

We review the epidemiology and presentation of patients with hyponatremia, the pathophysiology of the disorder with respect to sodium and fluid balance, and the diagnostic procedures for determining the correct cause.

RESULTS

We then present the various treatment options, including discussion of one of the newest groups of agents, the arginine vasopressin receptor antagonists, currently under study for the treatment of hyponatremia in neurosurgical patients.

CONCLUSION

Hyponatremia is a serious comorbidity in neurosurgical patients that requires particular attention as its treatment varies by cause and its consequences can affect neurological outcome.

The incidence and pathophysiology of hyponatraemia after subarachnoid haemorrhage

BACKGROUND

Hyponatraemia is common following subarachnoid haemorrhage (SAH) but the pathogenesis is unclear. Objective To establish the incidence, pathophysiology and consequences of hyponatraemia following SAH.

METHODS

A retrospective case-note analysis of all patients with SAH admitted to Beaumont Hospital between January 2002 and September 2003. Three hundred and sixteen cases of SAH were substantiated by computed tomography (CT) scan and angiogram findings. Hyponatraemia was defined as plasma sodium < 135 mmol/l.

RESULTS

One hundred and seventy-nine patients (56.6%) developed hyponatraemia and 62 (19.6%) developed significant hyponatraemia (plasma sodium < 130 mmol/l). The incidence of severe hyponatraemia following hypophysectomy was lower in the period of analysis (5/81, 6.2%, P < 0.01). Hyponatraemia was more common in patients with identified aneurysms (anterior circulation 102/168, 60.7%, posterior circulation 56/95, 60.8%) than in those with no radiological aneurysm (21/54, 38.8%, P < 0.001). Hyponatraemia was more common after aneurysmal clipping (68/103, 66%) or coiling (82/132, 62%) than after conservative treatment (29/81, 36%, P < 0.001). The aetiology of significant hyponatraemia was the syndrome of inappropriate antidiuretic hormone secretion (SIADH) 39/62 (69.2%), cerebral salt-wasting syndrome (CSWS) 4/62 (6.5%), hypovolaemic hyponatraemia 13/62 (21%), hypervolaemic hyponatraemia 3/62 (4.8%) and mixed CSW/SIADH 3/62 (4.8%). Hyponatraemia was associated with longer hospital stay (24.0 +/- 2.6 vs. 11.8 +/- 0.8 days, P < 0.001) but did not affect mortality (P = 0.07). Hyponatraemia developed more than 7 days following SAH in 21.4% and more then 7 days following intervention in 31.8%.

CONCLUSIONS

Hyponatraemia is common following SAH and is associated with longer hospital stay. Clipping and coiling of aneurysms are associated with higher rates of hyponatraemia. SIADH is the commonest cause of hyponatraemia after SAH. Delayed hyponatraemia is common, and has implications for early discharge strategies.

Hyponatremia in the neurosurgical patient: diagnosis and management

Hyponatremia is frequently encountered in patients who have undergone neurosurgery for intracranial processes. Making an accurate diagnosis between the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting (CSW) in patients in whom hyponatremia develops is important because treatment differs greatly between the conditions. The SIADH is a volume-expanded condition, whereas CSW is a volume-contracted state that involves renal loss of sodium. Treatment for patients with SIADH is fluid restriction and treatment for patients with CSW is generally salt and water replacement. In this review, the authors discuss the differential diagnosis of hyponatremia, distinguish SIADH from CSW, and highlight the diagnosis and management of hyponatremia, which is commonly encountered in patients who have undergone neurosurgery, specifically those with traumatic brain injury, aneurysmal subarachnoid hemorrhage, recent transsphenoidal surgery for pituitary tumors, and postoperative cranial vault reconstruction for craniosynostosis.

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.

[Hyponatremia in neurologic intensive care: cerebral salt wasting syndrome and inappropriate antidiuretic hormone secretion]

Hyponatraemia is a frequent complication in neurologically injured patients; it is a secondary cerebral injury. Hyponatraemia leads to consciousness problems, convulsions, worsening of the neurological status and thus the neurological evaluation. Hyponatraemia is secondary to free water retention (inappropriate ADH secretion) or to renal salt loss. The cerebral salt wasting syndrome (CSWS) has been described with head injury, subarachnoid haemorrhage and after several sorts of brain insults. It is characterised by an increased natriuresis and diuresis. Diagnosis is based on hyponatraemia, hypernatriuresis, increased diuresis and hypovolaemia. However, inappropriate ADH secretion and CSWS share several diagnostic criteria. The atrial natriuretic factor and the C-type natriuretic factors play a role in the development of the CSWS. The diagnostic approach and monitoring are based on the assessment of sodium and water losses. Therapy is based on correction of the circulating volume and natraemia. Speed of correction is a matter of debate: slow correction presents the risk of further neurological injury whereas rapid correction presents the risk of central pontine myelinosis.

Fluid loading in rats increases serum brain natriuretic peptide concentration

Hyponatremia after subarachnoid hemorrhage has been linked to high plasma concentration of atrial natriuretic peptide and brain natriuretic peptide. Volume expansion therapy to prevent symptomatic vasospasm, such as intensive hypertensive and hypervoremic therapy, may alter systemic concentration of these peptides. We therefore examine brain natriuretic peptide secretion in rats in response to acute volume expansion, infusing to 10 ml of saline over 1 h. In the 10 ml group, brain natriuretic peptide concentrations showed a significant increase from pre-infusion concentrations 1 h after initiation of infusion, but had begun to fall 1 h later. We suspect that high plasma concentration of brain natriuretic peptide after subarachnoid hemorrhage is partly caused by hypervoremic therapy.