Refractory Hypotension post Coronary Artery Bypass Graft Unmasking Hypoaldosteronism: Case Report and Literature Review

Abstract

The sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) are the cornerstones of cardiovascular adaptation. The simultaneous presence of disorders involving both is not uncommon, especially in patients with coronary artery disease undergoing coronary artery bypass surgery (CABG). This is the case of a patient with both hyporeninemic hypoaldosteronism and autonomic dysfunction. This article describes his clinical course before and after CABG surgery, along with a literature review of those interrelated entities. Our patient is a 63-year-old male with a history of hypertension and hyperlipidemia presenting for CABG for triple vessel disease. On the day of admission, the patient had sudden unprovoked loss of consciousness along with hypotension and bradycardia. He reported having had similar episodes in the past at times of emotional stress. After stabilization, the patient underwent CABG surgery the next day and it was uneventful. Four hours later, he developed another episode of hypotension with bradycardia which resolved upon administration of fluids. On postoperative day 2, while removing the jugular line, he had loss of consciousness with 5 seconds pause recorded on his bedside monitor. A carotid massage confirmed carotid sinus hypersensitivity, which necessitated the insertion of a pacemaker. However, patient continued to have similar episodes despite a functioning device. Workup revealed hyporeninemic hypoaldosteronism with an undetectable aldosterone level, although patient was not diabetic, had normal cortisol level, and had no other risk factors for those findings. Patient was started on fludrocortisone 0.1 mg daily; his hemodynamics improved markedly, and his symptoms resolved permanently. Our patient has hyporeninemic hypoaldosteronism caused most likely by his autonomic dysfunction, rather than having of two separate entities. A review of the literature showed that primary autonomic insufficiency with reduced circulating norepinephrine levels prevent renin activation and subsequently aldosterone release, leading to hyporeninemic hypoaldosteronism. Coronary artery disease is a known cause of autonomic dysfunction and CABG surgery unmasks this entity, which explains the exacerbation of our patient’s symptoms during this phase.