This study investigated the postmortem diffusion of tracheal lidocaine into the blood after intubation in three individuals whose heart beat was not restored by cardiopulmonary resuscitation. The results are compared with those obtained in animal experiments using rabbits.
The first human subject was a 3.5-month-old female baby who died of sudden infant death syndrome. She was autopsied approximately 20 h after death. A toxicological examination revealed the presence of 0.349 mg/L and 0.102 mg/L of lidocaine in the blood in the left and right ventricles of the heart, respectively. No lidocaine was detected in the cerebrum, liver, or right femoral muscle. The second subject was a 44-year-old man who died of brain swelling due to head injuries, and was autopsied approximately 20 h after death. Lidocaine concentrations in the hili of the left and right lungs were 10.9 mg/kg and 2.65 mg/kg, respectively, and 1.02 mg/L and 0.209 mg/L in the blood in the left and right ventricles of the heart, respectively. The right femoral vein blood contained only a trace amount of lidocaine; no lidocaine was detected in the cerebrum, liver, or right femoral muscle of this subject. The third subject was a 38-year-old man who died of bleeding due to a stab wound to the left thigh, and was autopsied approximately 20 h after death. Lidocaine concentrations were 1.41 mg/kg and 1.37 mg/kg in the hili of the left and right lungs, respectively, and 0.642 mg/L and 0.746 mg/L in the blood in the thoracic aorta and superior vena cava, respectively. No lidocaine was detected in the right femoral vein blood, cerebrum, liver or right femoral muscle.
In the animal experiments, rabbits carcasses were left in the supine position at an ambient temperature following application of 1 mg/kg lidocaine hydrochloride into the trachea just above the bifurcation. Lidocaine concentrations of 0.550–4.03 mg/L and 3.05–7.30 mg/L were detected in the heart blood, one and three days after the lidocaine treatment, respectively; neither the cerebrum nor right femoral muscle contained detectable amounts of lidocaine. The pH values of body fluids and tissues of the human and animal corpses were below 7.0. This study has demonstrated that following intubation, tracheal lidocaine diffuses into surrounding fluids and tissues, and that this is attributable to postmortem acidosis. We suggest that, in subjects who underwent cardiopulmonary resuscitation with intra-tracheal intubation, heart blood and femoral vein blood should be analyzed for lidocaine. In addition, the pattern of distribution of lidocaine in the surrounding tissues may provide some information on the state of victims during cardiopulmonary resuscitation.