Pharmacokinetics and technique of endotracheal and deep endobronchial lidocaine administration

To determine absorption characteristics of endotracheal lidocaine, we administered lidocaine to hemodynamically stable patients by different techniques. Blood samples were taken for measurement of lidocaine plasma concentrations (fluorescence polarization immunoassay), and pharmacokinetics were calculated by regression analysis. Plasma concentrations at 1.5 and 2 min after drug administration were higher (P < 0.05) after instillation into the endotracheal tube (1.40 +/- 0.19 and 1.26 +/- 0.14 microgram/mL) than after deep endobronchial administration (1.00 +/- 0.08 and 0.83 +/- 0.05 microgram/mL). A biphasic absorption with a division of the area under the curve (AUCtot) into two parts (AUC1 and AUC2) could be assumed. After tube instillation, the AUC1/AUCtot ratio (2.6%) was higher (P < 0.05) than after deep endobronchial instillation (1.1%). To achieve high plasma concentrations within a short time, AUC1, representing a nearly instantaneous absorption, seems to be more important than AUC2, representing a higher but delayed absorption (depot effect). Because deep endobronchial lidocaine administration accentuated the late absorption, presumably by preventing drug distribution to the whole lung, this technique was detrimental to obtaining high plasma concentrations within a short period of time.