RESUMO
OBJECTIVE: To compare lidocaine levels after administration through an i.v. line, a standard endotracheal (ET) tube, and an ET tube side port (ETSP) designed for medication administration. METHODS: A double-blind, prospective, triple crossover canine study was performed. Seventeen anesthetized mongrel dogs were given standard doses of 2% lidocaine via i.v. (1.5 mg/kg), endotracheally through the main lumen (3 mg/kg diluted in 10 mL normal saline), and endotracheally through the modified side port (3 mg/ kg diluted in 10 mL normal saline). Arterial blood gases (ABGs) and plasma lidocaine levels were measured at time 0, 30 sec, 1 min, 5 min, 10 min, 20 min, 30 min, and 60 min. Mean lidocaine levels across time, comparing the 3 methods of administration, were analyzed with repeated-measures analysis of variance. The main outcome was the comparison of mean ET and ETSP lidocaine levels at each time point using paired t-tests. The attainment and duration of lidocaine levels considered therapeutic in cardiac arrest (1.4 micrograms/mL) were described. ABGs were measured at each point to describe trends in oxygenation. RESULTS: Mean lidocaine levels, comparing the 3 methods of administration, were significantly different at all time points except time 0. The ETSP levels were significantly lower than the ET main-lumen levels at 30 sec, 1 min, 5 min, and 10 min. i.v.-administered lidocaine attained quick therapeutic levels and revealed faster elimination. Lidocaine administered through the ET main lumen reached therapeutic levels more slowly, and maintained such levels longer. Lidocaine administered through the ETSP never reached therapeutic levels. Mean PO2S remained > 340 torr throughout each method of administration. CONCLUSION: This nonarrest canine model suggests that lidocaine levels achieved through an ETSP are lower than levels obtained with the same drug dose via an ET main lumen. Therapeutic lidocaine levels are obtainable by i.v. or ET main-lumen routes, but not via this ETSP.