Use of lidocaine in endotracheal intubation. Blood and urine concentrations in patients and deceased after unsuccessful resuscitation

Abstract

In toxicological analysis of postmortem samples the local anesthetic lidocaine is often identified. In most cases, lidocaine levels result from its use as aid in endotracheal intubation. The range of the drug's concentration in blood and urine was studied under controlled conditions from a cohort of cardiac surgery patients (n=35).Plasma concentrations 1h after exposure to lidocaine in the range of the recommended 81mg coating the endotracheal tube were less than 0.2mg/l, its metabolite monoethylglycinxylidide (MEGX) less than 0.05mg/l (median ratio 0.18, range 0.03–1.23). Also the concentrations of lidocaine and MEGX in urine samples were low (less than 1.2 and 0.1mg/l, respectively) with MEGX/lidocaine ratios of 0.11 (median, range up to 1.2). These data were compared with results obtained by analyzing postmortem blood and urine samples of 18 deceased with a documented cardiopulmonary resuscitation attempt prior to death. Blood concentrations were in the same range (lidocaine median 0.07, range 0.02–1.07mg/l; MEGX median 0.01, range <0.001–0.044mg/l); besides low lidocaine concentrations in urine. MEGX was detected only in 2 out of 9 urine samples.The results of the present study confirm that lidocaine is absorbed in the trachea from the endotracheal tube coated with lidocaine containing gel. Postmortem quantitative results can be explained on the basis of the data obtained in the controlled study.