Dysautonomia in Guillain-Barré Syndrome: Prevalence, Clinical Spectrum, and Outcomes.

BACKGROUND: Guillain-Barré syndrome (GBS), when severe, involves the autonomic nervous system; our objective was to assess the spectrum and predictors of dysautonomia, and how it may impact functional outcomes. METHODS: A retrospective review of patients admitted to the Mayo Clinic in Rochester, MN between January 1, 2000, and December 31, 2017, with GBS and dysautonomia was performed. Demographics, comorbidities, parameters of dysautonomia, clinical course, GBS disability score, and Erasmus GBS Outcome Score (EGOS) at discharge were recorded. RESULTS: One hundred eighty seven patients were included with 71 (38%) noted to have at least one manifestation of dysautonomia. There are 72% of patients with a demyelinating form of GBS and 36% of patients with demyelination had dysautonomia. Ileus (42%), hypertension (39%), hypotension (37%), fever (29%), tachycardia or bradycardia (27%), and urinary retention (24%) were the most common features. Quadriparesis, bulbar and neck flexor weakness, and mechanical ventilation were associated with autonomic dysfunction. Patients with dysautonomia more commonly had cardiogenic complications, syndrome of inappropriate antidiuretic hormone, posterior reversible encephalopathy syndrome, and higher GBS disability score and EGOS. Mortality was 6% in patients with dysautonomia versus 2% in the entire cohort (P = 0.02). CONCLUSIONS: Dysautonomia in GBS is a manifestation of more severe involvement of the peripheral nervous system. Accordingly, mortality and functional outcomes are worse. There is a need to investigate if more aggressive treatment is warranted in this category of GBS.

Hyponatraemia: the importance of obtaining a detailed history and corroborating point-of-care analysis with laboratory testing.

We describe a 67-year-old man admitted from a mental health unit with an incidental finding of hyponatraemia on routine blood tests. Laboratory investigations were in keeping with syndrome of inappropriate antidiuretic hormone secretion (SIADH). He had been recently commenced on mirtazapine. During his inpatient stay, he became increasingly confused. Review of a previous admission with hyponatraemia raised the possibility of voltage-gated potassium channel antibody-associated limbic encephalitis, although subsequent investigations deemed this unlikely as a cause of hyponatraemia. Although his sodium levels improved with fluid restriction, serial point-of-care testing proved misleading in monitoring the efficacy of treatment as inconsistencies were seen in comparison with laboratory testing. The cause of hyponatraemia may have been medication-induced SIADH and/or polydipsia. This case highlights the importance of collating detailed histories and laboratory blood testing to guide management in cases of hyponatraemia of unknown aetiology.

[Nephrogenic syndrome of inappropriate antidiuresis]. / Syndrome d'antidiurèse inappropriée néphrogénique.

Disorders of water balance are a disease commonly encountered in our clinical practice. Analysis of vasopressin receptor type II (V2R) is essential to understand the physiology of water balance and it is used as a biological prototype of G protein-coupled receptors (GPCRs). Nephrogenic syndrome of inappropriate antidiuresis (NSIAD) is a syndrome of inappropriate antidiuretic hormone secretion (SIADH) with low plasmatic vasopressin. The evidence on the role of V2 receptor and of aquaporin (AQP) in the mechanism of action for antidiuretic hormone (ADH) was based on the identification of protein gene mutations in patients with nephrogenic diabetes insipidus and NSIAD syndrome. V2R activating mutations were found in patients with NSIAD, contrasting with the numerous V2R inactivating mutations related to X-linked mutations described in patients with nephrogenic diabetes insipidus.

A quantitative approach to intravenous fluid therapy in the syndrome of inappropriate antidiuretic hormone secretion.

BACKGROUND: A wide range of interesting mathematical models has been derived to predict the effect of intravenous fluid therapy on the serum sodium concentration (most notably the Adrogué-Madias equation), but unfortunately, these models cannot be applied to patients with disorders characterized by aberrant antidiuretic hormone (ADH) release, such as the syndrome of inappropriate ADH secretion (SIADH). The use of intravenous fluids in these patients should prompt caution, as the inability of the kidneys to properly dilute the urine can easily result in deterioration of hyponatremia. METHODS: In this report, a transparent and clinically applicable equation is derived that can be used to calculate the estimated effect of different types and volumes of crystalloid infusate on the serum sodium concentration in SIADH patients. As a "proof of concept", we discuss five SIADH patient cases from our clinic. Alternatively, our mathematical model can be used to determine the infusate volume that is required to produce a certain desired change in the serum sodium concentration in SIADH patients. CONCLUSION: The presented model facilitates rational intravenous fluid therapy in SIADH patients, and provides a valuable addition to existing prediction models.

Diabetes Insipidus and Syndrome of Inappropriate Antidiuretic Hormone in Critically Ill Patients.

Diabetes insipidus and the syndrome of inappropriate antidiuretic hormone secretion lie at opposite ends of the spectrum of disordered renal handling of water. Whereas renal retention of water insidiously causes hypotonic hyponatremia in syndrome of inappropriate antidiuretic hormone secretion, diabetes insipidus may lead to free water loss, hypernatremia, and volume depletion. Hypernatremia and hyponatremia are associated with worse outcomes and longer intensive care stays. Moreover, pathologies causing polyuria and hyponatremia in patients in intensive care may be multiple, making diagnosis challenging. We provide an approach to the diagnosis and management of these conditions in intensive care patients.

Efficiency of Single Dose of Tolvaptan Treatment During the Triphasic Episode After Surgery for Craniopharyngioma

Inappropriate antidiuretic hormone syndrome (SIADH) may develop after intracranial surgery. SIADH in the pediatric age group is usually encountered in patients with an intracranial mass both before and after surgery. Fluid restriction is the standard therapy in SIADH. However, a resistant, hyponatremic pattern may be encountered in some cases. Vaptans have been recently introduced for treatment of hyponatremia due to SIADH. There is inadequate data concerning tolvaptan treatment in pediatric patients. We present a 13 year-old female with SIADH of triphasic episode who was transferred to our clinic after surgery for craniopharyngioma. Resistant hyponatremia did not resolve despite fluid restriction and hypertonic saline support. The patient responded rapidly to a single dose of tolvaptan, with no adverse effect, which resulted in successful control of her SIADH.

Possible anti-VGKC autoimmune limbic encephalitis associated with SIADH.

An 80-year-old woman presented with a 5-week history of increasing confusion. Examination was remarkable only for deficits in short-term memory and paranoid thoughts. Blood tests revealed hyponatraemia, and further biochemical testing was consistent with syndrome of inappropriate antidiuretic hormone (SIADH). After an exhaustive diagnostic workup for causes of SIADH, the only abnormal finding was a mildly raised antivoltage-gated potassium channel (VGKC) titre of 185 pmol/L (0-69) consistent with possible anti-VGKC autoimmune limbic encephalitis. However, other diagnostic features were absent. She is currently undergoing outpatient investigation for other causes of memory loss.