Management of hypercapnia in critically ill mechanically ventilated patients-A narrative review of literature

The use of lower tidal volume ventilation was shown to improve survival in mechanically ventilated patients with acute lung injury. In some patients this strategy may cause hypercapnic acidosis. A significant body of recent clinical data suggest that hypercapnic acidosis is associated with adverse clinical outcomes including increased hospital mortality. We aimed to review the available treatment options that may be used to manage acute hypercapnic acidosis that may be seen with low tidal volume ventilation. The databases of MEDLINE and EMBASE were searched. Studies including animals or tissues were excluded. We also searched bibliographic references of relevant studies, irrespective of study design with the intention of finding relevant studies to be included in this review. The possible options to treat hypercapnia included optimising the use of low tidal volume mechanical ventilation to enhance carbon dioxide elimination. These include techniques to reduce dead space ventilation, and physiological dead space, use of buffers, airway pressure release ventilation and prone positon ventilation. In patients where hypercapnic acidosis could not be managed with lung protective mechanical ventilation, extracorporeal techniques may be used. Newer, minimally invasive low volume venovenous extracorporeal devices are currently being investigated for managing hypercapnia associated with low and ultra-low volume mechanical ventilation.