The purpose of this study was to determine whether lidocaine is absorbed from the trachea during the artificial circulation of cardiopulmonary resuscitation. The tissue distribution of lidocaine was investigated in eight individuals (Cases 1–8) who underwent cardiopulmonary resuscitation before being pronounced dead.
In Cases 1–4, there was no restoration of heart beat during cardiopulmonary resuscitation. Heart massage had been continued for 5 min in Cases 1 and 2, and for 60 min in Cases 3 and 4. Relatively high concentrations of lidocaine (more than 0.1 mg/L) were detected in the blood left in the heart and/or in the large thoracic vessels in the four cases. In Cases 1–3, a large proportion of the lidocaine detected in these blood samples may have diffused from the trachea after cessation of cardiopulmonary resuscitation since no lidocaine was detected in the cerebrospinal fluid, cerebrum, liver, right kidney, and/or right femoral muscle. In Case 4, however, tracheal lidocaine was thought to have been absorbed during cardiopulmonary resuscitation because 0.167–0.340 mg/L or mg/kg lidocaine was detected in the cerebrospinal fluid, liver, right kidney, and right femoral muscle. This was substantiated in experiments performed in rabbit carcasses given 50 µL/kg Xylocaine™ jelly (a 2% lidocaine hydrochloride preparation) intratracheally, followed by rhythmical thoracic compressions (100–150 times per minute) for 60 min. A possible reason for lack of absorption of lidocaine from the trachea of Case 3 during a 60-min cardiopulmonary resuscitation procedure may have been that effective blood circulation was not obtained during cardiopulmonary resuscitation because of bleeding and pulmonary collapse.
Cases 5–8 survived for 3 h to 10 days after successful cardiopulmonary resuscitation; it was obvious that lidocaine was distributed to the tissues under the influence of the natural circulation. The kidney to liver lidocaine ratio in Case 4 (0.8) was much lower than that in Cases 5–8 (1.3–4.6), although the lidocaine ratio in the blood in the left ventricle when compared to blood in the right ventricle was similar in the five cases. The kidney to liver lidocaine ratio may be helpful in judging whether the lidocaine detected was absorbed during the artificial circulation of cardiopulmonary resuscitation or naturally. Additionally, postmortem diffusion of tracheal lidocaine into the blood in the left ventricle was much greater than into the blood in the right ventricle due to their anatomical location during a supine position. The pattern of tissue distribution of lidocaine gives useful information on the state of decedents during cardiopulmonary resuscitation.