Intrathoracic and pulmonary blood volume during CO2-pneumoperitoneum in humans

Background: Induction of CO2-pneumoperitoneum may have significant effects on systemic and pulmonary haemodynamics. We hypothesized, that intrathoracic (ITBV) and pulmonary blood volume (PBV) are affected during intra-abdominal CO2-insufflation, which may be pronounced by positional changes of the patient. Methods: Sixteen anaesthetized patients were studied before, during and after CO2-pneumoperitoneum for laparoscopic cholecystectomy. A dye indicator technique was used to assess ITBV and PBV. In addition, gas exchange and haemodynamics were recorded. Results: In the supine position, induction of CO2-pneumoperitoneum had no effects on ITBV, PBV and cardiac output. Mean systemic arterial pressure increased from 10.9+/-1.5 kPa (82+/-11 mmHg) to 12.7+/-1.5 kPa (95+/-11 mmHg, P<0.01). In the reverse Trendelenburg position ITBV decreased from 19.8+/-5.1 ml.kg(-1) to 16.7+/-3.7 ml.kg(-1) (P<0.05) during CO2-insufflation, but increased to control values after 20 min. PBV decreased from 4.2+/-1.2 ml.kg(-1) to 3.4+/-1.1 ml.kg(-1) (P<0.05) and remained decreased during CO2-pneumoperitoneum. Calculated venous admixture was unchanged throughout the study. Deflation of CO2-pneumoperitoneum increased ITBV (22.4+/-5.2 ml.kg(-1) P<0.05) and cardiac output above control values. Conclusions: In anaesthetized-paralyzed patients in the reverse Trendelenburg position intra-abdominal CO2-insufflaiion is associated with significant alterations of ITBV and PBV. The release of CO2-pneumoperitoneum is associated with a re-distribution of blood into the thorax.