Rare cause of delirium and hypoxemia after coronary bypass surgery: transdermal lidocaine patch-associated methemoglobinemia.

We present a case of a patient administered parasternal transdermal lidocaine patch therapy as part of a multimodal analgesic regime designed to diminish opioid-associated delirium after coronary bypass surgery. The patient presented with delirium and severe methemoglobinemia (41%) that responded to discontinuation of lidocaine therapy, oxygen administration, and methylene blue administration. The clinical contributors and medicolegal implications of this degree of lidocaine-associated methemoglobin-mediated delirium are presented in the hope of avoiding similar complications in the postoperative setting after coronary bypass surgery.