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 . kg¹ ( 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-insufflation 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.