Prevalence and Clinical Course of Methemoglobinemia After Cardiac Device Implantation

Objective: Methemoglobinemia is a 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. Prilocaine 2% was used in all procedures. Arterial blood gases and methemoglobin levels were evaluated at baseline and at 60 and 120 minutes after the procedure. A fractional methemoglobin level > 1.5% was defined as 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, and all recovered fully. Patients with FMetHb > 3% received higher anesthetic doses (P < 0.001). Differences in drug dose and pCO2 were observed between groups. Among the clinical parameters, the prilocaine dose demonstrated the strongest predictive value for methemoglobinemia, with an optimal cut-off of ≥ 24.50 mg identified by receiver operating characteristic (ROC) analysis (area under the curve: 0.693, P < 0.001).

Conclusion: Methemoglobinemia may occur more frequently than expected following CIED implantation. Early recognition and stratification using practical thresholds, such as FMetHb > 3%, may support timely management and improve clinical outcomes.

Keywords: Cardiac implantable electronic device implantation, ejection fraction, local anesthesia, methemoglobinemia