Metabolic Hypoxemia Research Articles

The Addition of O2 to the CO2 Does Not Prevent the Systemic Effects of the CO2 Pneumoperitoneum in a Rabbit Model

CO2 pneumoperitoneum used in endoscopic surgery induces systemic effects by CO2 absorption. It was claimed that a reduction in CO2 pneumoperitoneum-induced metabolic hypoxemia was achieved by the addition of small amounts of O2 to the CO2 in a rabbit ventilated model. We reevaluated the effects of the addition of O2 to the CO2 pneumoperitoneum upon CO2 absorption in a rabbit model. The effects of a pneumoperitoneum using 100% CO2, 90% CO2 + 10% O2, 95% CO2 + 5% O2, or 100% O2 on arterial blood gases, acid base and O2 homeostasis were evaluated in nonintubated rabbits. A pneumoperitoneum pressure of 10 cm H2O (approximately 7.35 mm Hg) was used. CO2 pneumoperitoneum of 120 minutes affected blood gases and acid base homeostasis. Whereas partial pressure of CO2 and HCO3 increased (P < 0.001) during pneumoperitoneum, pH and partial pressure of O2 decreased (P < 0.001). Similar results were obtained in O2-CO2 pneumoperitoneum (P > 0.05). CO2 pneumoperitoneum profoundly affected blood gases and acid base homeostasis, resulting in metabolic hypoxemia. The addition of O2 to the CO2 did not prevent the systemic effects of CO2 pneumoperitoneum in nonintubated animals.

Pathogenesis CO 2 Pneumoperitoneum-Induced Metabolic Hypoxemia in a Rabbit Model

Study Objective To investigate the effects of carbon dioxide (CO 2) pneumoperitoneum-induced changes in blood gases, acid-base balance, and oxygen homeostasis in rabbits. Design Prospective, randomized, controlled study (Canadian Task Force classification I). Setting University training and teaching center. Subjects Twenty-six adult female New Zealand white rabbits. Interventions Anesthesia and pneumoperitoneum. Measurements and Main Results In anesthetized rabbits arterial blood gases, acid-base balance, oxygenation values, and lactate concentrations were assayed during 2 hours. Spontaneous breathing, superficial and optimal ventilation without pneumoperitoneum, and with pneumoperitoneum at low (6 mm Hg) and higher (10 mm Hg) insufflation pressures were compared. The CO 2 pneumoperitoneum profoundly affected blood gases, acid-base balance, and oxygen homeostasis. Carboxemia with increasing end-tidal CO 2 and partial pressure of CO 2 (p< 0.001), acidosis with decreasing pH (p< 0.001), and base deficiency with decreasing actual base excess (p< 0.001), standard base excess and standard bicarbonate and acid excess with increasing hydrogen bicarbonate (p<0.05 and <0.01) were found. Desaturation (p <0.01) with decreasing oxyhemoglobin p <0.05) and hemoglobin oxygen affinity (p <0.01) were also found. Carboxemia with acidosis was more pronounced with higher (p <0.01) than with lower (p >0.05) intraperitoneal pressures, and also with spontaneous breathing (p <0.05) and superficial ventilation (p< 0.001) than with optimal ventilation, resulting in metabolic hypoxemia. Conclusion In superficially ventilated and spontaneously breathing rabbits, CO 2 pneumoperitoneum profoundly affected blood gases, acid-base balance, and oxygen homeostasis, resulting in metabolic hypoxemia. With optimal ventilation and low intraperitoneal pressure carboxemia, respiratory acidosis, and changes in oxygen metabolism were minimal.