Transsphenoidal surgery

Transsphenoidal surgery is the approach of choice for pituitary adenomas and is indicated when the mass impacts the function of other surrounding structures (Melmed & Jameson, 2018, p. 2672).  The common symptoms from a local mass effect of a pituitary tumor are headache and visual disturbances; and other symptoms that vary by adenoma type (Melmed & Jameson, 2018, p. 2671). Postoperative central diabetes insipidus (CDI) is a result of damage to the pituitary stalk, hypothalamic injury, or a disruption in the hypothalamic-neurohypophyseal connections (Elisaus & Ball, 2021). This results in a deficiency of AHD and prevents concentration of urine in the renal collecting tubule. DI can be classified into three different types: nephrogenic, central, and dipsogenic (Elisaus & Ball, 2021). Nephrogenic occurs when there is a lack of renal response to ADH and dipsogenic occurs secondary excess fluid intake. To determine which etiology of DI is present; a water restriction test is performed. If urine concentrates with water restriction, then there is no DI; next desmopressin (dDAVP) is given and if urine concentrates then it is CDI; in nephrogenic DI, urine will not concentrate with either intervention (Elisaus & Ball, 2021). In this scenario, we know the patient is manifesting CDI secondary to a pituitary adenoma resection. CDI occurs transiently in 10-20% of transsphenoidal pituitary surgeries and is permanent in 2-7% of patients (Swearingen, 2021). Thus, post-operative transsphenoidal surgical patient should be closely monitored for CDI by monitoring urine output. Polyuria (3L/d) and polydipsia are hallmark symptoms of DI (Elisaus & Ball, 2021). A diagnosis can be made by a low urine osmolality (<250mosmol/kg) with high serum osmolality (>290mosmol/kg) and no hyperglycemia (Elisaus & Ball, 2021). Treatment for CDI is with DDAVP 5-20mcg/day and fluid replacement. Serum sodium, urine osmolality, and urine output help guide the continued need for dDAVP and fluid therapy (Swearingen, 2021). Typically, only one or two doses of dDAVP are needed (Elisaus & Ball, 2021). CDI can vary from mild to severe with the major concern of life-threatening hypernatremia and dehydration. Hypernatremia can manifest with neurologic symptoms of: confusion, restlessness, lethargy, seizures, and death. Severe volume depletion can cause circulatory collapse. For these reasons, post-op transsphenoidal patients are typically monitored in the ICU for the first 48 hours to monitor for the development of DI.  Transsphenoidal surgery

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References

Elisaus, P., & Ball, S. (2021). Diabetes insipidus. Medicine, 49(8), 495–497. https://doi.org/10.1016/j.mpmed.2021.05.009

Melmed, S., & Jameson, J. L. (2018). Pituitary tumor syndromes. In Harrison’s principles and practice of hospital medicine (20th ed.). McGraw Hill.

Swearingen, B. (2021). Transsphenoidal surgery for pituitary adenomas and other sellar masses. UpToDate. Retrieved March 31, 2022, from https://www.uptodate.com/contents/transsphenoidal-surgery-for-pituitary-adenomas-and-other-sellar-masses?search=transsphenoidal%20surgery&source=search_result&selectedTitle=1~35&usage_type=default&display_rank=1#H21307966

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Mar 31, 2022, 1:53 AM

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Diabetes insipidus (DI) is an uncommon neurological condition that accounts for 1 in every 25,000-patient population (Christ-Crain et al., 2021). The underlying clinical issue with DI comes as part of the polydipsia-polyuria syndrome, which is characterized by hypotonic urine and excessive polydipsia (Christ-Crain et al., 2021; Christ-Crain, 2020). The postoperative neurosurgical patient is prone to developing the central form of DI (Christ-Crain et al., 2021; Christ-Crain, 2020). The pathophysiological underpinning of central DI is the lack or inability of the posterior pituitary to secrete arginine vasopressin (Christ-Crain et al., 2021; Christ-Crain, 2020). The insufficient synthesis of arginine vasopressin in the hypothalamic neurohypophyseal system causes this inappropriate osmotic stimulation (Christ-Crain et al., 2021; Christ-Crain, 2020).  Transsphenoidal surgery

The clinical manifestation of Di is excessive urinary excretion, usually more than 50 mL per kilogram in 24 hours, and increased oral intake of water (Christ-Crain & Gaisl, 2021). The patient with DI will also present with serum hyperosmolar and hypernatremia associated with urinary hypo osmolar (Christ-Crain & Gaisl, 2021). Some patients may or may not present with fever, excessive sense of thirst, irritability, etc. (Christ-Crain & Gaisl, 2021). The main treatment in DI is to identify the primary cause, postoperative neurosurgery in this case (Christ-Crain & Gaisl, 2021). Therefore, it is vital that the provider must keep in mind that severe hyperosmolality from dehydration should be managed promptly (Christ-Crain & Gaisl, 2021). The water should be replaced by at least 50 % of the calculated free water deficit within 24 hours (Christ-Crain & Gaisl, 2021). The overcorrection of water can lead to unwanted neurological consequences such as cerebral edema, seizures (Christ-Crain & Gaisl, 2021). Furthermore, the management of diabetes insipidus should be focused on the prevention of secondary complications of excessive water intake, which can further cause severe fluid and electrolyte imbalances (Christ-Crain & Gaisl, 2021). In addition, a single dose of desmopressin is sufficient to treat neurosurgery-related DI (Christ-Crain & Gaisl, 2021).

References

Christ-Crain, M, Winzeler, B, Refardt, J. (2021). (University Hospital Basel, University of Basel, Basel, Switzerland). Diagnosis and management of diabetes insipidus for the internist: an update (Review). J Intern Med.,290(1), 73– 87. https://doi.org/10.1111/joim.13261

Christ-Crain M: Diabetes Insipidus: New Concepts for Diagnosis. Neuroendocrinology 2020;110:859-867. doi: 10.1159/000505548

Christ-Crain, M. & Gaisl, O. (2021). Diabetes insipidus. La Presse Médicale, 50 (4), 104093. https://doi.org/10.1016/j.lpm.2021.104093.