Acute Severe Hypovolemic Hyponatremia in a Patient on Intravenous Dexamethasone

Abstract

Hyponatremia is a commonly encountered electrolyte imbalance with varied etiology. Hyponatremia can be broadly classified as hypotonic, isotonic, and hypertonic hyponatremia based on the tonicity of plasma. Hypotonic hypovolemia is further classified as hypovolemic, euvolemic, and hypervolemic hyponatremia based on the volume status. Gastrointestinal fluid and electrolyte losses, secondary to vomiting and diarrhea, is an important predisposition to hypotonic hypovolemic hyponatremia. The renin-angiotensin-aldosterone system (RAAS) and antidiuretic hormone (ADH) play a pivotal role in maintaining intravascular volume and serum sodium concentration. Dexamethasone is a potent glucocorticoid with minimal mineralocorticoid activity. It negatively affects the hypothalamic-pituitary-adrenal axis and the renin-angiotensin-aldosterone system, particularly with prolonged administration. In the index case, acute severe hypovolemic hyponatremia ensued on the third post-procedure (endovascular embolization of traumatic carotico-cavernous fistula (CCF)) day while the patient was on intravenous dexamethasone. This case underscores that even small fluid and electrolyte imbalance in the setting of dexamethasone therapy may lead to severe hypovolemic hyponatremia, which requires specific therapy.

Keywords: accidental head trauma; acute hyponatremia; carotico-cavernous fistula; dexamethasone; renin-angiotensin-aldosterone system.

Figure 1. Computed tomography of the brain

(A) Acute extradural hematoma is noted in the left occipital region (black arrow) with a mass effect on the left cerebellar hemisphere (white arrow). (B) Post-embolization of the carotico-cavernous fistula shows streak artifacts due to coil mass and embosylate cast (black arrow). The extradural hematoma (white arrow) has not increased in size.

Figure 2. Digital subtraction angiogram

(A) Lateral view of the digital subtraction angiogram shows evidence of direct carotico-cavernous fistula with reflux of contract into the superior ophthalmic vein (black arrow) and into the superior petrosal vein (white arrow). (B) Post-embolization of carotico-cavernous fistula. Coil mass and embosylate cast noted in the cavernous sinus (black arrows). Note that there is no residual filling of the fistula, superior ophthalmic vein, or superior petrosal sinus.