Postoperative methemoglobinemia following infiltrative lidocaine administration for combined anesthesia in pediatric craniofacial surgery

BACKGROUND: Infiltrative anesthesia of the scalp with lidocaine was used in an attempt to reduce blood loss and anesthetic requirements during pediatric craniofacial surgery. Lidocaine, however, has the potential to cause methemoglobinemia. In this retrospective cohort-study we analyzed the incidence and effects of postoperative methemoglobinemia following subcutaneous lidocaine administration. METHODS: During 1999-2006, 50 infants (age: 3-31 months) undergoing elective craniofacial surgery were analyzed. All infants received general anesthesia and routine monitoring, including invasive arterial blood pressure measurement. Prior to incision, the scalp was infiltrated with 6-15 ml lidocaine 1% (with epinephrine 1 : 200.000). Blood loss and blood transfusions were recorded. Methemoglobin (Met-Hb) levels were determined postoperatively using co-oximetry. RESULTS: Twenty percent of the operated infants showed elevated Met-Hb levels (median of maximal levels: 6%; range: 2.2-18%) at admission on the PICU. In 80% of these methemoglobinemia resolved spontaneously within 12 h, only two children received methylene blue because of visible cyanosis. The intra- and postoperative course was otherwise uneventful in all the children despite significant total blood loss (median of blood loss as percentage from total estimated blood volume: 43%; range: 11-110%). Lidocaine was the only substance identified to have the potential to cause methemoglobinemia. However, the average administered dose of lidocaine was not significantly different between patients with or without methemoglobinemia (13 +/- 3.1 vs 12 +/- 3.5 mg.kg(-1); P = 0.37). CONCLUSIONS: Even though we did not measure lidocaine plasma levels, lidocaine was the most likely cause of postoperative methemoglobinemia. Despite a high incidence, methemoglobinemia occurred sporadically and was without dangerous consequences.