Inhalational Sedation and Mechanical Power

Overview

Analgosedation is usually given to critically ill patients admitted in ICU. Fentanyl is the most common agent used for this purpose. For sedative agent, midazolam and propofol are commonly administered. However, too much sedation is apparently associated with increased duration of mechanical ventilation, prolonged ICU stay, and increased mortality. In mechanically ventilated patients, mechanical power is the respiratory mechanic that can predict clinical outcomes including mortality in both ARDS and non-ARDS patients. Previous study demonstrated that sedating mechanically ventilated patients with propofol could decreased mechanical power. This was possibly associated with improved clinical outcomes in these patients. At present, there is no clinical study investigating effects of inhalation sedation on mechanical power and clinical outcomes in mechanically ventilated patients.

In the intensive care unit (ICU), sedation is used to improve comfort and tolerance during mechanical ventilation, invasive diagnostic and therapeutic interventions or nursing care. The most commonly used sedatives are intravenous benzodiazepines and propofol. These agents are associated with over-sedation in 40 to 60% of patients, which can lead to prolonged intubation, delirium and drug-induced hypotension. Volatile anesthetics are increasingly used for sedation in European and Canadian intensive care units that offer advantages of rapid drug on and off effects and clearance via pulmonary exhalation with no active metabolites. Delivery of volatile agents in the ICU can be simply performed using a small lightweight and portable anesthetic reflector so-called anesthesia conserving device. Compared with intravenous sedatives, volatile anesthetics may allow shorter time to extubation and can facilitate mental recovery. In mechanically ventilated patients, a growing body of evidence suggests that the mechanical power (MP) plays an important role in the ventilator-induce lung injury (VILI) and prognosis in in both acute respiratory distress syndrome (ARDS) and non-ARDS patients. MP is the energy per unit time released to the respiratory system according to the tidal volume, PEEP, respiratory rate, and flow applied. In ARDS patients receiving invasive mechanical ventilation, high MP was associated an increased mortality. Moderate to deep sedation can inhibit the respiratory center and reduces the excessive respiratory drive, thereby reducing transpulmonary pressure and MP as well as probably reducing lung injury. The purpose of this study aims to investigate the effect of inhalation sedation on MP in mechanically ventilated patient admitted in the ICU. We hypothesize that MP in mechanically ventilated patients can be reduced by administering inhalational sedation.