Effects of Two Different Stepwise Lung Recruitment Maneuvers on Patient Hemodynamics During Anesthesia for Laproscopic Surgery

Pneumoperitonium for laproscopic surgery usually result in decrease total respiratory compliance due to cranial shift of the diaphragm. Alveolar recuirtment is applied hopefully to minimize lung atlectasis and open collapsed alveoli to maintain arterial oxygenation. The anantomical proximity of lungs and heart within the chest means that any increase in intrathoracic pressure could have major effect on cardiovascular functions.Up to now, far too little attention has been paid to the decrease in left ventricular performance owing to fluctuation within the- chamber within chamber system-that preciptate stroke volume and cardiac output reduction during recruitment maneuvers.Up to our knowledge, the effect of ARM on patient heamodynamics is still unclear. in this study, we will compare two different recruitment maneuvers on patient haemodynamics during laproscopic surgery.Therefore this study is designed to investigate the effect of two individualized recruitment maneuvers during anethesia for laproscopic surgery to encourage best arterial oxygenation with the least haemodynamic compromise. Accordingly we assume that recruitment by incremental stepwise PEEP by 5cmH2o with pressure controlled ventilation may be associated with better stroke volume stability without haemodynamic alteration in comparison to incremental stepwise tidal volume by 4ml/kg during volume controlled ventilation.

• Pre-oxygenation for 5 minutes will be done in all patients and they will receive 0.02 mg/Kg midazolam, 1-2 μg/Kg fentanyl, 2-2.5 mg/kg Propofol slowly IV until loss of verbal contact. atracurium 0.5 mg/kg to facilitate proper placement of endotracheal tube. All patients will be mechanically ventilated using volume control mode (VC mode) with tidal volumes of 6 ml/ PBWT, with respiratory rate 12 breath per minute (bpm) and PEEP 5 cmH2O to keep end tidal Carbone dioxide (ETCO2) at 30-35 mmHg. Anaesthesia will be maintained in all patients using (1-1.5) minimum alveolar concentration (MAC) of Sevoflurane in O2/air mixture with FIO2 (0.4).Patients will be randomly assigned to one of two equal groups, according to computer-generated randomization sequence:
• group 1 (RM TV ): Recruitment maneuver with tidal volume .
• group 2 (RM PEEP): Recruitment maneuver with positive end expiratory pressure.

Group 1 (RM TV):

The ventilation protocol consisted of volume controlled mechanical ventilation, FiO2 0.4, inspiratory-to-expiratory (I:E) ratio at 1:2, and respiratory rate (RR) set to normocapnia (end-tidal CO2 partial pressure between 35 and 40mmHg, TV 6 mL/kg PBW and 5 cmH2O PEEP.

RMs were conducted under volume controlled ventilation with initial settings of a limit of peak inspiratory pressure at 40cmH2O, TV at 6 mL/kg PBW (PBW = 50.0+0.905*((height in cm)-152.4) for men, and = 45.5+0.905*((height in cm)-152.4) for women) , RR at 7 breaths/min, PEEP at5 cmH2O, and I:E ratio at1:1. The TV was then increased by steps of 4 mL/kg PBW until plateau airway pressure (Pplt) was 40 cmH2O, after which 3 breaths were allowed. Finally, the limit of peak inspiratory pressure, TV, RR, and I:E ratio were reset at values equal to those preceding the RM. The ventilation protocol could be changed at any time when concerned about patient safety.