Background and Goal of Study: During cardiopulmonary bypass (CPB) a variety of methods are used to minimize postoperative pulmonary complications and preserve pulmonary function. Various interventions are applied by anaesthesiologists, e.g. PEEP, CPAP, or recruitment manoeuvres, in order to achieve beneficial effects on the pulmonary status following CPB. To investigate the current evidence for potential beneficial effects of various manoeuvres (“lung management”) following CPB, we performed a quantitative systematic review of the literature.
Materials and Methods: A systematic search of Medline, Biosys, Embase and the Cochrane Library (1966 - July 2010) was performed to identify randomised controlled trials (RCTs) that focused on lung management during cardiopulmonary bypass.
Without any language restrictions, a search with the following terms was performed: cardiopulmonary bypass, continuous positive airway pressure, CPAP, positive pressure ventilation, PEEP, vital capacity manoeuvre. Identified studies were then hand-searched for further relevant literature. Interventions that were compared in at least 3 trials were analysed using a fixed effect model.
Results and Discussion: Data from 15 RCT's were analysed (N=739 patients). Median Oxford score of the trials was 2 (Range 1-4). Use of CPAP 5 -10 mmHg (7 comparisons) during CPB resulted in a significant higher oxygenation index (PaO2/FiO2) immediately post CPB (p< 0.00001). It also resulted in lower AaDO2 and a lower shunt fraction immediately post CPB (p=0.003 and p< 0.00001, respectively). 4 hours after weaning from CPB the AaDO2 was not significantly improved compared to control. Positive pressure ventilation during CPB (2 comparisons), PEEP following CPB (2 comparisons) and vital capacity manoeuvre (6 comparisons with various techniques and endpoints), were not analysed.
Conclusion(s): Results from this systematic review imply that the use of CPAP during cardiopulmonary bypass may improve oxygenation and pulmonary gas exchange immediately after weaning from CPB and reduces the pulmonary shunt fraction. No significant benefit was found 4 hours after CPB. Other interventions were sparsely investigated. The documentation of clinically relevant (long term) outcomes, e.g. ventilator hours, ICU length of stay, was lacking, which supports the need for further trials in this field.