Hyponatremia Clinical Trial
Official title:
Comparison of the Vasopressin-2 Antagonist Tolvaptan and Fluid Restriction in the Treatment of Hyponatremia Following Pituitary Surgery
Context. The relevance of hyponatremia has been acknowledged by guidelines from the United
States of America (2013) and Europe (2014). However, treatment recommendations differ due to
limited evidence.
Objective. In hyponatremia following pituitary surgery - caused by the syndrome of
inappropriate antidiuretic hormone (SIADH) secretion - the investigators compared fluid
restriction with the pharmacological increase of water excretion by blocking the vasopressin
2 receptors with tolvaptan at a low and moderate dose.
Design. Prospective observational study.
Setting. Neurosurgical Department of a University hospital with more 200 pituitary procedures
per year.
Patients. Participants undergoing surgery for sellar lesions and developing a serum sodium
below 135 mmol/L. The diagnosis of SIADH was established by eu- or hypervolemia (daily
measurement of body weight and fluid balance daily), an inappropriately concentrated urine
(specific gravity) and exclusion of a cortico- and thyreotropic insufficiency.
Intervention. Participants were treated with fluid restriction (n=38) or tolvaptan at 3.75
(n=38) or 7.5 mg (n=48) orally.
Main Outcome Measures. Treatment efficacy was assessed by the duration of hyponatremia,
sodium nadir and length of hospitalization. Safety was established by an increment serum
sodium below 10 mmol/L per day and exclusion of side effects.
Patients of the Department of Neurosurgery, University of Erlangen-Nuremberg, undergoing
surgery for sellar lesions were prospectively included. The study protocol was approved by
the local Ethical Committee (Re.-No. 103_12 BC). Informed written consent was given by the
participants or the next-of-kin in each case. Exclusion criteria comprised of those below 18
years of age, pregnancy and a drug intolerance.
Patients Baseline information included age, gender, BMI and the clinical presentation. The
pre-operative work-up included an opthalmological examination, a 1.5 Tesla magnetic resonance
imaging (MRI) with 2mm axial, coronal and sagittal sections revealing the tumor localization,
extension, and its invasive behavior. Microsurgery was always performed by the same surgeon.
The macroscopic delineation and invasiveness, the surgical manipulation of the pituitary
stalk and extend of tumor resection, surgical complications, as well as an intraoperative
cerebrospinal fluid (CSF) leak were documented. The tumor and the dura of the floor of the
sella were examined histo-pathologically including the proliferation rate, regressive
changes, atypical findings, and the existence of Crooke cells and periodic acid-Schiff (PAS)
expression. Routine laboratory work-up included creatinine, urea, and alanine
aminotransferase (ALT).
The pre- and postoperative endocrine testing of the pituitary function comprised the basal
values of cortisol (CORT), growth hormone (GH), insulin-like growth factor (IGF) 1, thyroid
stimulating hormone (TSH), free thyroxine (fT4), total triiodothyronine (tT3), luteinizing
hormone (LH), follicle stimulating hormone (FSH), testosterone (TES), estradiol (E2), and
prolactin (PRL). Insufficiency of the corticotropic axis was determined by a short synacthen
test (adreno-corticotropic hormone; ACTH)-test stimulating with 0.25 mg Syntropin (Synacthen,
Novartis Pharma, Nuremberg, Germany) intra-venously and serum cortisol measurement at 0 and
30 minutes.
Surveillance Post-operatively, participants were transferred to the general floor. For a
minimum of 10 days, fluid intake, body weight, and urine volume with specific gravidity are
documented daily, along with blood pressure and heart rate three-times daily, blood samples
for the assessment of electrolytes are taken on day 1, 2, 3, 5, 7, and 9. An endocrine
dynamic testing was performed on day 7.
Analytical methods Venous blood samples were drawn in the morning between 7:00 and 9:00 am
into pre-cooled tubes. Clotted samples were promptly centrifuged at 3,000 X g for 15 min at 4
degree Celsius, and then the plasma was frozen at -80 degree Celsius until analysis.
An automated system (Immulite®2000, Diagnostic Products Corporation) was used for the
following serum hormone measurements: Serum cortisol levels > 10.5 µg/dL, with an assay
sensitivity of 0.20 µg/dL, was considered normal; a cortisol response peak to the ACTH-test
higher than 18 µg/dl was considered adequate; for IGF-1 of 135-485 ng/mL (18-30 years),
120-397 ng/mL (31-40 years), 113-306 ng/mL (41-50 years), 100-250 ng/mL (51-60 years), and
92-229 ng/mL (>60 years) (assay sensitivity of 20 ng/mL); LH > 0.25 U/L (follicular phase)
and > 20 U/L (menopausal) in women, and > 1 international units (IU)/L in men (assay
sensitivity of 0.05 mIU/mL); FSH > 0.25 U/L (follicular phase) and > 30 U/L (menopausal) in
women, and > 1 IU/L in men (assay sensitivity of 0.1 mIU/mL); TES > 90 ng/dL in men (assay
sensitivity of 15 ng/dL); E2 > 60 pg/mL (follicular phase) and > 10 pg/mL (menopausal) in
women (assay sensitivity of 15 pg/mL); PRL < 500 micro international units (µIU)/L (assay
sensitivity of 0.16 µU/L); PRL serum concentrations were considered normal < 360 ng/ml in men
and < 530 ng/mL in women. TSH serum concentrations were considered normal > 0.45 µU/mL, fT4 >
0.77 ng/dL, and tT3 > 0.8 ng/mL.
Study design Treatment of hyponatremia was initiated as soon as a SIADH was confirmed by eu-
or hypervolemia (daily measurement of body weight and fluid balance), an inappropriately
concentrated urine (measurement of specific gravity), and exclusion of a cortico- and
thyreotropic insufficiency. The established treatment regime consisted of a restriction of
fluid intake < 1 L whenever the serum sodium dropped below 135 mmol/L or the body weight
gained more than 1 kg (fluid restriction). In a second cohort of patients, the fluid
restriction was replaced by a low dosage of tolvaptan (tolvaptan 3.75 mg), and in a third
cohort by a medium dosage (tolvaptan 7.5 mg). Since a rapid correction of hyponatremia is
hazardous and leaves the patient vulnerable to the risk of osmotic demyelination, we not only
started the cohort study with a very low concentration of 3.75 mg tolvaptan, but also
established a tight follow-up regime after medication. The serum sodium concentration was
controlled at 6:00 pm. Those participants, whose serum sodium concentration further dropped
below 132 mmol/L, were treated with a second tablet of tolvaptan and the serum sodium was
measured the next day at 8:00 am. Those participants, whose serum sodium was increased by not
more than 5 mmol/L underwent the next blood check on the next day at 8:00 am. Those
participants, whose serum sodium increased by more than 5 mmol/L were treated by 1L tea/water
or a 500 mL 5% glucose infusion.
Statistical analysis SPSS statistical software (SPSS Inc., Chicago, Illinois, USA) was used
for all statistical analyses. Analyses were performed using the Chi-squared test and
Mann-Whitney U tests where appropriate. Significance was accepted at p < 0.05.
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