(1005) Huffing and Puffing With Olanzapine: Olanzapine-Induced Dyspnea

Introduction: Antipsychotic agents have been the primary treatment modality for schizophrenia, particularly demonstrating efficacy in the management of psychosis. Olanzapine belongs to the class of atypical antipsychotics and has demonstrated an enhanced efficacy and safety profile. In this case, we would like to highlight a rare side effect of central neurogenic hyperventilation in a patient receiving Olanzapine for the management of agitation while on mechanical ventilation.

Description: We present a 59-year-old male patient who underwent aortic root replacement and transaortic valve replacement for severe aortic stenosis and an ascending aortic aneurysm. His postoperative course was complicated by cardiogenic shock and acute hypoxic respiratory failure, resulting in multiple reintubations and eventually resulting in him getting a tracheostomy. He was started on Olanzapine in addition to dexmedetomidine drip for multiple episodes of agitation and dyssynchrony with mechanical ventilation. Over the course of the next five days, his ventilation requirements increased from 6.6 to 9.6 L/min (reaching max 20 L/min), with Vt of 550 ml and respiratory rate up to 40/min. An arterial blood gas revealed a pH of 7.62, PCO2 of 24.4, PO2 of 125 and bicarbonate of 25, indicating acute respiratory alkalosis. Chest x-ray and CTA chest demonstrated mild pulmonary edema and small bilateral effusions, treated with intermittent hemodialysis. Due to lack of explanation, an extensive review of his medications was done. A decision was made to stop Olanzapine. Over the next 48 hours, the patient’s hyperventilation resolved. ABG revealed resolved respiratory alkalosis.

Discussion: Only a few case reports have demonstrated a relationship between Olanzapine and hyperventilation. Increased minute ventilation on the ventilator while on olanzapine therapy, lack of other causes of increased respiratory drive, and improvement after discontinuation suggest a causal association. The mechanism is unclear. Olanzapine is a commonly used medication for patients with agitation and delirium in the ICU. This case report highlights that physicians should be cautious when using atypical antipsychotics - specifically Olanzapine- which can cause increased respiratory drive without other explainable causes.