Reduction of CO2-pneumoperitoneum-induced metabolic hypoxaemia by the addition of small amounts of O2 to the CO2 in a rabbit ventilated model. A preliminary study.

BACKGROUND: CO2-pneumoperitoneum used in endoscopic surgery induces system effects by CO2 absorption. This study investigated the effect of the addition of O2 to CO2-pneumoperitoneum, upon CO2 absorption. METHODS: The effect of a pneumoperitoneum using 100% CO2 or 94% CO2 6% O2 upon arterial blood gases, acid base and O2 homeostasis was evaluated. In series A suboptimal ventilation and a pneumoperitoneum pressure (PP) of 10 mmHg was used. In series B adequate ventilation and PP of 6 mmHg was used. RESULTS: CO2pneumoperitoneum profoundly affected blood gases and acid base homeostasis i.e. increasing pCO2, HCO3 (P < 0.001) and lactate concentrations (P < 0.05) and decreasing pH, actual base excess and standard bicarbonate (P < 0.001), resulting in metabolic hypoxaemia with desaturation, lower pO2 (P < 0.001) and O2Hb (P < 0.05). These effects were more pronounced with higher PP and suboptimal ventilation. CONCLUSION: CO2pneumoperitoneum profoundly affected blood gases and acid base homeostasis resulting in metabolic hypoxaemia. The addition of 6% of O2 to the CO2-pneumoperitoneum prevented these effects to a large extent. If these preliminary data are confirmed in the human, the addition of a few percent of O2 to CO2 could become important for endoscopic surgery of long duration, especially in obese patients with limited cardiorespiratory adaptation and steep Trendelenburg.