Effect of low tidal volume during general anesthesia for urological procedures on lung functions

BackgroundPostoperative lung function impairment is common after surgery specially in the lateral decubitus position. Evidence suggests that if we use low tidal volume during mechanical ventilation this may limit post-operative lung injury. We compared post-operative lung functions in patients put in the lateral position when ventilated with low vs. high tidal volumes.MethodsThis prospective open label clinical trial was performed on 104 patients ASA I&II scheduled for elective urological operations done in the right or left lateral position expected to last more than 2 hours. Patients were divided into two groups: group L ventilated with 5–7 ml/kg tidal volume, with positive end expiratory pressure (PEEP) 10 cm H2O and recruitment maneuver (RM) and group H ventilated with 10–12 ml/kg tidal volume with zero-end expiratory pressure and no recruitment maneuver. Pulmonary functions were measured pre-operatively and 6, 12, 24 hours after extubation.ResultsBetter pulmonary functions were found in the first post-operative six hours in the low tidal volume group and significant difference was found in all parameters. FVC and FEV1/FVC were significantly higher in the low tidal volume group (P = 0.000) after 12 hours of extubation. After 24 hours we found significant difference in the predicted FEV1 and FVC and FEV1/FVC ratio (P = 0.000) being higher in the low tidal volume group.ConclusionIn comparison with conventional mechanical ventilation using high tidal volume with zero PEEP and no RM: a lung protective strategy using low tidal volume with 5–10 cm H2O PEEP and RM did improved lung functions in the first post-operative 24 hours. The overall postoperative follow up did not show significant difference between the two groups.