Carbon dioxide output in laparoscopic cholecystectomy |
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Authors: | Kazama T; Ikeda K; Kato T; Kikura M |
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Institution: | Department of Anaesthesiology and Intensive Care, Hamamatsu University School of Medicine, 3600 Handa-cho, Hamaamtsu, Japan 431-31 |
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Abstract: | In pneumoperitoneum, carbon dioxide eliminated in expired gas (carbon
dioxide output) contains both metabolic and absorbed carbon dioxide from
the peritoneal cavity. When elimination of carbon dioxide is much higher
than carbon dioxide output, storage of tissue carbon dioxide and arterial
carbon dioxide concentrations change. Finally, the rate of carbon dioxide
eliminated in expired gas is not a match for the real rate of metabolic
production and absorbed carbon dioxide from the peritoneal cavity. During
and after insufflation of carbon dioxide, changes in carbon dioxide output
were elucidated under constant arterial carbon dioxide pressure (PaCO2),
the same as the preinduction level. We studied patients undergoing elective
laparoscopic cholecystectomy. Carbon dioxide output, oxygen uptake,
respiratory exchange ratio (RER), expired minute ventilation (VE),
deadspace to tidal volume ratio (VD/VT ratio) and arterial to end-tidal
carbon dioxide partial pressure difference (PaCO2-PE'CO2) were determined
before induction, and during anaesthesia, pneumoperitoneum and recovery. By
controlling ventilatory frequency (f) every 1 min, PaCO2 was adjusted to
concentrations before induction. Constant monitoring of end-tidal carbon
dioxide partial pressure (PE'CO2) and intermittent measurement of
(PaCO2-PE'CO2) (15-min intervals) were conducted to predict PaCO2). Carbon
dioxide output and oxygen uptake decreased significantly from mean values
of 83.5 (SEM 5.2), 101.6 (5.1) to 68.5 (4.2), 81.1 (4.6) ml min-1 m-2
(ATPS, P < 0.05) with sevoflurane anaesthesia, and RER did not change.
During carbon dioxide pneumoperitoneum (intra-abdominal pressure 8 mm Hg),
carbon dioxide output increased by 49% (102.4 (5.0) ml min-1 m-2) (P <
0.05) while oxygen uptake remained stable and RER increased from 0.84
(0.02) to 1.16 (0.03) (P < 0.05). It was necessary to increase VE during
pneumoperitoneum by 1.54 times that during anaesthesia to maintain
individual PaCO2 values constant. After removal of carbon dioxide from the
abdominal cavity, the regression equation of excess carbon dioxide
output/BSA best fitted a two-compartment model. The time constants of the
rapid and slow compartments were 8.2 and 990 min, respectively. Excess
carbon dioxide output/BSA was still 5.5 ml min-1 m-2, 30 min after
pneumoperitoneum.
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