Low-tidal volume ventilation is arising as a tool to optimize the ventilatory management and to improve clinical outcome in patients undergoing general anesthesia for abdominal surgery. A recent large randomized controlled trial failed to detect a significant difference between two different approaches for ensuring adequate lung recruitment (PEEP=12 cmH2O + scheduled recruiting maneuvers vs. PEEP 2 cmH2O) during protective ventilation. Thus, in patients undergoing open abdominal surgery and receiving low-tidal volumes, the effects of different positive end-expiratory pressure (PEEP) levels and recruiting maneuvers remain to be established. Design: prospective, cross-over, physiological trial. PURPOSE To assess the physiological effects of different PEEP levels with or without scheduled recruiting maneuvers in patients undergoing general anesthesia for open abdominal surgery and receiving low-tidal volume ventilation.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
30
Fluid administration or amine administration if deemed necessary by the attending physician. Haemodynamics will be monitored through noninvasive cardiac output assessment by arterial pulse contour analysis
Total intravenous anesthesia with a standard protocol
3-5 ml/kg of balanced crystalloids will be administered throughout the whole surgical procedure
Volume-control ventilation with tidal volume=7 ml/kg of predicted body weight for the entire surgical procedure. Respiratory rate will be set to maintain EtCO2 within a physiological range and kept unchanged for the entire duration of the study
Pressure-control ventilation inspiratory pressure=10 cmH2O. Steplike 5-cmH2O-PEEP increase every 30 seconds to achieve a peep of 35 cmH2O, followed by 5-cmH2O-PEEP reduction every 30 seconds to set PEEP
General surgery OR, A. Gemelli hospital
Rome, Italy
Driving Pressure
Respiratory system elastic pressure (Plateau pressure-total PEEP)
Time frame: At the end of each 40-minute step
Lung strain
Lung static and dynamic strain
Time frame: At the end of each 40-minute step
Dead space
Approximated as the difference between End-tidal CO2 and PaCO2 divided by PaCO2
Time frame: At the end of each 40-minute step
Oxygenation
PaO2/FiO2
Time frame: At the end of each 40-minute step
Lung recruitment
% (lung recruitment/change in end-expiratory lung volume)
Time frame: At the end of each 40-minute step
Lung overdistension due to PEEP
% (lung overdistension/change in end-expiratory lung volume)
Time frame: At the end of each 40-minute step
Functional residual capacity
Change in functional residual capacity due to PEEP, measured with the Nitrogen washin-washout technique
Time frame: At the end of each 40-minute step
Heart rate
heart rate
Time frame: At the end of each 40-minute step
Blood pressure
Arterial blood pressure
Time frame: At the end of each 40-minute step
Stroke volume
Stroke volume, measured by pulse contour analysis
Time frame: At the end of each 40-minute step
Stroke volume variation
Stroke volume variation, measured by pulse contour analysis
Time frame: At the end of each 40-minute step
Cardiac Output
Stroke volume x heart rate
Time frame: At the end of each 40-minute step
Fluid requirements
Fluid bolus requirements, according to the decision of the attending physician blinded to the design of the study
Time frame: At the end of each 40-minute step
Vasoactive agents
Vasoactive agents requirements, according to the decision of the attending physician blinded to the design of the study
Time frame: At the end of each 40-minute step
Adverse events
Adverse events
Time frame: At the end of each 40-minute step
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