THE EFFECT OF SHORT-TERM INSTILLATION OF A MUCOLYTIC AGENT (MESNA) ONAIRWAY-RESISTANCE IN MECHANICALLY VENTILATED PATIENTS

Study objective: To determine whether bolus instillation of a mucolyti c agent (mesna) could diminish airway resistance, endotracheal tube re sistance, or both in patients mechanically ventilated for acute respir atory failure. Design: Randomized, double-blind, placebo-controlled, c rossover trial. Setting: Medical-surgical ICU of a county hospital cov ering 350,000 inhabitants. Patients: Twenty sedated and paralyzed pati ents with an endotracheal tube (ET) in place more than 72 h. Intervent ions: Data were recorded in three steps: (1) basal; (2) 10 min after e ndotracheal instillation of 3 mt of either saline solution or mesna; a nd (3) 10 min after instillation of the opposite drug. A 2-h washout p eriod was allowed between data collection. Measurements and results: W e measured tidal volume (VT), inspiratory now (VI), auto-PEEP, peak pr essure (both at airway opening [Pmax.aw] and trachea [Pmax.tr]) and pl ateau pressure (Pplat), and we calculated respiratory system complianc e (Crs) and the inspiratory resistances of airways+tube (Rmax.aw), air ways (Rmax.tr), and ET (Rtube). We found significant differences after the instillation of mesna compared with baseline in the following: ai rway 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/PAO(2) (0.360+/-0.152 vs 0.296+/-0 .127), and PaCO2 (42+/-12.9 vs 43+/-14.1 mm Hg). We found no changes i n compliance, auto-PEEP, and hemodynamics during the study. Instillati on of saline solution had no effect on the physiologic variables studi ed. Conclusions: In our patients, bolus tracheal instillation of mesna does not improve airway resistance; in fact, mesna instillation induc es episodes of bronchospasm that disappear 2 h later.