Alkalinization of intra-cuff lidocaine and use of gel lubrication protect against tube-induced emergence phenomena

In vitro evaluation of diffusion of lidocaine and alkalinized lidocaine through the polyurethane membrane of the endotracheal tube

OBJECTIVES

Endotracheal tube (ETT) and its inflated cuff are likely to induce specific reactivity at the emergence time. In ICU, the tolerance of the ETT cuff could be a part of patient agitation and increased of sedation.

MATERIALS AND METHODS

Using specific ICU ETT cuff (thin polyurethane cuff), we perform an in vitro evaluation of diffusion of lidocaine and alkalinized lidocaine (L-B) across the PU cuff for a long duration. We evaluate the safety of this procedure by a daily injection into the cuff.

RESULTS

With lidocaine alone, we observed a low rate of diffusion through the cuff (<8% over 24h), whereas the L-B solution had a high diffusion (>90% over 24h). The released profiles were similar from day 0 to day 8, and no cuff rupture was reported over the 8-day study.

CONCLUSION

The safety, controlled release, and lack of deleterious effects on cuff membrane were confirmed. In case of unexpected cuff rupture, an adequate determination of the mixture allows to obtain a safe solution with the achievement of a physiological pH (7.4) and the small dose of lidocaine (40 mg).

Alkalinization of Intracuff Lidocaine: Efficacy and Safety

When alkalinized lidocaine instead of air is used to fill the endotracheal tube (ETT) cuff, coughing, and bucking are decreased during extubation when ventilation is controlled with N2O. However, sodium bicarbonate (NaHCO3) used to transform lidocaine hydrochloride (L-HCl) to lidocaine base induces a pH increase that could be irritating for mucosa in the case of cuff rupture. Therefore, we determined, in a randomized controlled study with controlled patient ventilation without N2O, whether the smallest concentrations of NaHCO3 (1.4% versus 8.4%) reduced diffusion (in vitro evaluation) and other secondary clinical benefits. After pH determination of different solutions (2 mL of 2% L-HCl and 2 to 6 mL of 8.4%, or 1.4% NaHCO3), an in vitro lidocaine diffusion through the ETT cuffs was evaluated (2 mL of 2% L-HCl and 3 mL of 8.4% or 1.4% NaHCO3). Then, adult patients scheduled for total thyroidectomy surgery were consecutively enrolled (n = 20 for each group). The ETT cuff was filled with air (group air) or with alkalinized lidocaine (2 mL of 2% L-HCl) using 8.4% (group large dose) or 1.4% (group small dose) of NaHCO3. After tracheal extubation, sore throat was evaluated by visual analog scale as the main end-point of the study. Hoarseness, bucking, dysphonia, dysphagia, cough, restlessness, and postoperative nausea and vomiting were also evaluated. There was a slight tendency toward a slower release when a small concentration of NaHCO3 was used (i.e., 1.4%). Compared with group air, the alkalinized-lidocaine groups had a significant reduction in sore throat during the 24-h postoperative period (P < 0.0001). The difference was not significant between the two alkalinized lidocaine groups. This increase in ETT tolerance was confirmed by the analysis of secondary end-points. No laryngospasm, rupture of ETT cuff, or depression of the swallowing reflex were recorded. A decrease in sore throat during the postoperative period was recorded when the cuff was inflated with a small dose of alkalinized lidocaine (i.e., 40 mg of L-HCl and 1.4% of NaHCO3) rather than with air when ventilation was controlled without N2O.