Failure of lipid emulsion to reverse neurotoxicity after an ultrasound-guided axillary block with ropivacaine and mepivacaine

Abstract

lipid a second generalized convulsion appeared and this was terminated by 125 mg of thiopental. Blood samples were taken 1 h after the anesthetic procedure to assess the venous plasma concentration of ropivacaine and mepivacaine. Because of the patient’s history of syncope, brain computed tomography (CT) was performed after the surgery. It was normal. The concentrations of local anesthetics were high, at 1.45 μg·ml −1 for ropivacaine and 4.80 μg·ml −1 for mepivacaine. Postoperative electrocardiogram showed no signs of arrhythmia or changes in the PQ or QT intervals or QRS width. After 3 h the tracheal tube was removed. The brachial plexus showed no impairment of sensory function. The patient woke up without any sequelae. Intralipid (Baxter Healthcare) has been reported as being able to reverse neurologic and cardiac complications due to the administration of local anesthetics [5]. We report here a second convulsion after the administration of Intralipid in a patient anesthetized with propofol and mechanically ventilated (to control acidosis). Several hypotheses can be suggested to explain this fi nding: fi rst, the dose of Intralipid (4.16 ml·kg −1 ; 250 ml) was insuffi cient; second, Intralipid was not effi cient enough to decrease the blood concentration of the local anesthetics; and third, the administration of the lipid emulsion was too late (15 min after the beginning of the seizure). Moore [6] advises injecting lipid emulsion after classical resuscitation failure. We think it must be administered as soon as possible after intubation concomitantly with other drugs. Furthermore, with ultrasonographic guidance, direct intravascular injection could probably have been avoided. However, the resorption of local anesthetic into cellular tissues 20 min after the injection cannot be excluded. Ultrasonographic guidance associated with electric stimulation may make the technique of peripheral nerve block more secure, but it is not an absolute guarantee of safety.