The effect of short-term instillation of a mucolytic agent (mesna) on airway resistance in mechanically ventilated patients.

STUDY OBJECTIVE

To determine whether bolus instillation of a mucolytic agent (mesna) could diminish airway resistance, endotracheal tube resistance, or both in patients mechanically ventilated for acute respiratory failure.

DESIGN

Randomized, double-blind, placebo-controlled, crossover trial.

SETTING

Medical-surgical ICU of a county hospital covering 350,000 inhabitants.

PATIENTS

Twenty sedated and paralyzed patients with an endotracheal tube (ET) in place more than 72 h.

INTERVENTIONS

Data were recorded in three steps: (1) basal; (2) 10 min after endotracheal instillation of 3 mL of either saline solution or mesna; and (3) 10 min after instillation of the opposite drug. A 2-h washout period was allowed between data collection.

MEASUREMENTS AND RESULTS

We measured tidal volume (VT), inspiratory flow (VI), auto-PEEP, peak pressure (both at airway opening [Pmax.aw] and trachea [Pmax-.tr]) and plateau pressure (Pplat), and we calculated respiratory system compliance (Crs) and the inspiratory resistances of airways+tube (Rmax.aw), airways (Rmax.tr), and ET (Rtube). We found significant differences after the instillation of mesna compared with baseline in the following: airway plus tube resistance (Rmax.aw) (16.9 +/- 7.1 vs 18.9 +/- 7.7 cm H2O); airways resistance (Rmax.tr) (9.8 +/- 6.2 vs 12.0 +/- 6.4 cm H2O), PaO2 (96 +/- 28.5 vs 80 +/- 24.8 mm Hg), PaO2/PAO2 (0.360 +/- 0.152 vs 0.296 +/- 0.127), and PaCO2 (42 +/- 12.9 vs 43 +/- 14.1 mm Hg). We found no changes in compliance, auto-PEEP, and hemodynamics during the study. Instillation of saline solution had no effect on the physiologic variables studied.

CONCLUSIONS

In our patients, bolus tracheal instillation of mesna does not improve airway resistance; in fact, mesna instillation induces episodes of bronchospasm that disappear 2 h later.