Prevalence and Clinical Course of Methemoglobinemia After Cardiac Device Implantation

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.

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.

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).

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.