Factors predicting postoperative hyponatremia and efficacy of hyponatremia management strategies after more than 1000 pituitary operations

Clinical article

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Object

Syndrome of inappropriate antidiuretic hormone secretion–induced hyponatremia is a common morbidity after pituitary surgery that can be profoundly symptomatic and cause costly readmissions. The authors calculated the frequency of postoperative hyponatremia after 1045 consecutive operations and determined the efficacy of interventions correcting hyponatremia.

Methods

The authors performed a retrospective review of 1045 consecutive pituitary surgeries in the first 946 patients treated since forming a dedicated pituitary center 5 years ago. Patients underwent preoperative and daily inpatient sodium checks, with outpatient checks as needed.

Results

Thirty-two patients presented with hyponatremia; 41% of these patients were symptomatic. Postoperative hyponatremia occurred after 165 operations (16%) a mean of 4 days after surgery (range 0–28 days); 19% of operations leading to postoperative hyponatremia were associated with postoperative symptoms (38% involved dizziness and 29% involved nausea/vomiting) and 15% involved readmission for a mean of 5 days (range 1–20 days). In a multivariate analysis including lesion size, age, sex, number of prior pituitary surgeries, surgical approach, pathology, lesion location, and preoperative hypopituitarism, only preoperative hypopituitarism predicted postoperative hyponatremia (p = 0.006). Of patients with preoperative hyponatremia, 59% underwent medical correction preoperatively and 56% had persistent postoperative hyponatremia. The mean correction rates were 0.4 mEq/L/hr (no treatment; n = 112), 0.5 mEq/L/hr (free water restriction; n = 24), 0.7 mEq/L/hr (salt tablets; n = 14), 0.3 mEq/L/hr (3% saline; n = 20), 0.7 mEq/L/hr (intravenous vasopressin receptor antagonist Vaprisol; n = 22), and 1.2 mEq/L/hr (oral vasopressin receptor antagonist tolvaptan; n = 9) (p = 0.002, ANOVA). While some patients received more than 1 treatment, correction rates were only recorded when a treatment was given alone.

Conclusions

After 1045 pituitary operations, postoperative hyponatremia was associated exclusively with preoperative hypopituitarism and was most efficiently managed with oral tolvaptan, with several interventions insignificantly different from no treatment. Promptly identifying hyponatremia in high-risk patients and management with agents like tolvaptan can improve safety and decrease readmission. For readmitted patients with severely symptomatic hyponatremia, the intravenous vasopressin receptor antagonist Vaprisol is another treatment option.

Abbreviations used in this paper:ADH = antidiuretic hormone; SIADH = syndrome of inappropriate ADH secretion.

Article Information

Address correspondence to: Manish K. Aghi, M.D., Ph.D., Department of Neurosurgery, University of California at San Francisco, 505 Parnassus Ave., Room M779, San Francisco, CA 94143-0112. email: AghiM@neurosurg.ucsf.edu.

Please include this information when citing this paper: published online August 23, 2013; DOI: 10.3171/2013.7.JNS13273.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Timing of postoperative hyponatremia after pituitary surgery. A: Postoperative hyponatremia most frequently occurred on postoperative Day 2, after which the incidence of postoperative hyponatremia decreased until a second smaller delayed peak occurring on postoperative Day 7. B: Symptomatic postoperative hyponatremia occurred most frequently on postoperative Day 1, after which the incidence remained relatively low until a second smaller delayed peak occurred on postoperative Day 7. C: In this retrospective study, all inpatients received daily sodium checks, but outpatient sodium checks only occurred as follow-up to document resolution of hyponatremia or to evaluate patients with symptoms suggestive of possible SIADH or diabetes insipidus. Thus, the number of patients receiving sodium checks on each postoperative day declined over the course of the first 29 postoperative days.

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    The frequency of postoperative hyponatremia in patients with various preoperative anterior pituitary deficits. Patients with any anterior pituitary deficit (p < 0.05) or deficits in the gonadal (follicle-stimulating hormone, luteinizing hormone, estrogen, progesterone, or testosterone), thyroid (thyroid-stimulating hormone, T3, or T4), or adrenal (adrenocorticotropic hormone or cortisol) axes had an increased risk of postoperative hyponatremia compared with those without. GH = growth hormone.

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    Rate of serum sodium correction (in mEq/L/hr) in patients as a function of individual treatments. Paired comparisons revealed that only patients receiving tolvaptan or Vaprisol alone exhibited more rapid serum sodium correction than patients receiving no treatment (p < 0.05). Bars denote the mean, and the whiskers denote the SD.

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