Prevalence and Clinical Course of Methemoglobinemia After Cardiac Device Implantation.

OBJECTIVE: Methemoglobinemia is potentially serious complication of local anesthetic use during cardiac implantable electronic device (CIED) implantation. Although it is mostly asymptomatic limited awareness may delay diagnosis and treatment. METHOD: This prospective observational study included 126 patients undergoing CIED implantation under local anesthesia. Prilocain 2% has been used in all procedures. Arterial blood gases and methemoglobin levels were evaluated at baseline, 60, and 120 minutes after the procedure. Fraction of methemoglobin levels > 1.5 % results in methemoglobinemia. Patients were categorized into three groups based on 60-minute fractional methemoglobin (FMetHb) levels: ≤1.5%, 1.5-3%, and >3%. Clinical parameters, anesthetic dosage, and outcomes were compared between groups. RESULTS: Methemoglobin levels >1.5% were observed in 80.2% of patients. Three patients required treatment; all recovered fully. Patients with FMetHb >3% received higher anesthetic doses (p<0.001). Drug dose and pCO₂ were observed between groups. Among the clinical parameters, prilocaine dose demonstrated the strongest predictive value for methemoglobinemia, with an optimal cut-off of ≥24.50 mg identified by ROC analysis (AUC: 0.693, p<0.001). CONCLUSION: Methemoglobinemia may occur more frequently than expected following CIED implantation and early recognition and stratification using practical thresholds such as >3% FMetHb support timely management and improved outcomes.