Severe Cardiovascular Collapse Associated With Remimazolam-Based Anesthetic Induction: A Case Series of Three Elderly Patients.

Remimazolam is an ultra-short-acting benzodiazepine that is increasingly used for the induction and maintenance of general anesthesia owing to its favorable hemodynamic profile. However, severe perioperative hypersensitivity reactions associated with its use have been reported. We report three cases of elderly patients who experienced severe cardiovascular collapse immediately after anesthetic induction with remimazolam. Additionally, an institutional review conducted over an 18-month study period identified six suspected perioperative hypersensitivity reactions. All six patients were elderly and developed sudden cardiovascular or respiratory instability shortly after induction of anesthesia with remimazolam and rocuronium. Of these, three patients experienced severe cardiovascular collapse requiring epinephrine administration or cardiopulmonary resuscitation, and two progressed to cardiac arrest. Cutaneous manifestations were absent or minimal in several cases, whereas a marked reduction in end-tidal CO₂ and refractory hypotension were the predominant clinical features. In selected cases, elevated histamine or tryptase levels provided evidence of mast-cell activation. Although rocuronium remains an important alternative causative agent, the temporal relationship with remimazolam administration, the recurrence pattern within the institution, and the uneventful subsequent anesthesia with alternative regimens in some patients suggest that remimazolam or its formulation components should be considered among the potential triggers. These cases highlight the need for early recognition of perioperative hypersensitivity when abrupt cardiovascular collapse and a sudden decrease in end-tidal CO₂ occur during induction, even in the absence of skin findings.