Plasma lignocaine concentrations associated with extradural analgesia in patients with and without multiple organ failure.

We have measured plasma concentrations of lignocaine after thoracic extradural analgesia with continuous infusion of lignocaine in eight intensive care patients with chest wall trauma or after major upper abdominal surgery. Four patients developed multiple organ failure (MOF). Plasma concentrations of lignocaine in arterial blood were measured 4, 8, 24 and 48 h after a continuous infusion of lignocaine was commenced in the extradural space. Plasma concentrations of lignocaine were greater in all patients with MOF (range 2.7-5.1 micrograms ml-1) than in patients without MOF (range 0.8-1.2 micrograms ml-1). Because plasma concentrations in patients with MOF were within the low toxic range, extradural infusion of lignocaine should only be considered in intensive care patients without MOF or when plasma concentrations of lignocaine are monitored.