Plasma lidocaine levels following hematoma block for distal radius fractures.

Venous plasma levels of lidocaine were determined in 8 patients presenting to the emergency department with acute distal radius fractures and who had had anesthesia with fracture hematoma block. The block was performed in an aseptic fashion via a dorsal approach with a dose of 2.2-2.4 mg/kg of lidocaine without epinephrine. Onset of anesthesia was in less than 5 min which reduced pain from manipulation of the fracture to modest levels. Plasma lidocaine levels determined by gas chromatography-mass spectrometry reflected rapid systemic absorption of lidocaine from the fracture hematoma. Maximum systemic concentrations were seen at 20-30 min and ranged from 100 to 1,100 ng/ml, well below the toxic threshold of 5,000 ng/ml.