THE IMPACT OF AN ENDOTRACHEAL SIDE PORT ON THE ABSORPTION OF LIDOCAINE

Objective: To compare lidocaine levels after administration through an IV 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 vi a IV (1.5 mg/kg), endotracheally through the main lumen (3 mg/kg dilut ed in 10 mL normal saline), and endotracheally through the modified si de 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 us ing paired t-tests. The attainment and duration of lidocaine levels co nsidered therapeutic in cardiac arrest (1.4 mu g/mL) were described, A BGs were measured at each point to describe trends in oxygenation. Res ults: Mean lidocaine levels, comparing the 3 methods of administration , were significantly different at all time points except time 0. The E TSP levels were significantly lower than the ET main-lumen levels at 3 0 sec, 1 min, 5 min, and 10 min. IV-administered lidocaine attained qu ick therapeutic levels and revealed faster elimination. Lidocaine admi nistered through the ET main lumen reached therapeutic levels more slo wly, and maintained such levels longer. Lidocaine administered through the ETSP never reached therapeutic levels, Mean PO(2)s remained >340 torr throughout each method of administration. Conclusion: This nonarr est canine model suggests that lidocaine levels achieved through an ET SP are lower than levels obtained with the same drug dose via an ET ma in lumen. Therapeutic lidocaine levels are obtainable by IV or ET main -lumen routes, but not via this ETSP.