Optimizing working space in porcine laparoscopy: CT measurement of the effects of intra-abdominal pressure

• Published in: Surgical endoscopy Vol. 27; no. 5; pp. 1668 - 1673
• Main Authors: Vlot, John, Wijnen, Rene, Stolker, Robert Jan, Bax, Klaas
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01-05-2013; Springer Nature B.V
• Subjects: Abdomen; Abdominal Cavity - diagnostic imaging; Abdominal Cavity - physiology; Abdominal Surgery; Abdominal Wall - physiology; Acidosis; Anesthesia; Anesthesia, Intravenous; Anesthesiology; Animals; Biometry - methods; Carbon Dioxide - administration & dosage; Carbon Dioxide - adverse effects; Compliance; Experiments; Gastroenterology; Gynecology; Heart Rate; Hepatology; Hypercapnia - chemically induced; Hypercapnia - therapy; Insufflation; Laparoscopy; Laparoscopy - veterinary; Medical research; Medicine; Medicine & Public Health; Organ Size; Pediatrics; Pneumoperitoneum, Artificial; Pressure; Proctology; Propofol; Respiration; Respiration, Artificial - methods; Respiratory Rate; Sufentanil; Surgery; Sus scrofa - surgery; Swine; Tomography; Tomography, X-Ray Computed; Ventilation; Ventilators; Netherlands; Germany; Animal model; Laparoscopy; Computed tomography; CO; Pneumoperitoneum; Working space
• ISSN: 0930-2794; 1432-2218
• DOI: 10.1007/s00464-012-2654-0

Background
Several factors may affect volume and dimensions of the working space in laparoscopic surgery. The precise impact of these factors has not been well studied. In a porcine model, we used computed tomographic (CT) scanning for measuring working space volume and distances. In a first series of experiments, we studied the relationship between intra-abdominal pressure (IAP) and working space.
Methods
Eleven 20 kg pigs were studied under standardized anesthesia and volume-controlled ventilation. Cardiorespiratory parameters were monitored continuously, and blood gas samples were taken at different IAP levels. Respiratory rate was increased when ETCO
2
exceeded 7 kPa. Breath-hold CT scans were made at IAP levels of 0, 5, 10, and 15 mmHg. Insufflator volumes were compared to CT-measured volumes. Maximum dimensions of pneumoperitoneum were measured on reconstructed CT images.
Results
Respiratory rate had to be increased in three animals. Mild hypercapnia and acidosis occurred at 15 mmHg IAP. Peak inspiratory pressure rose significantly at 10 and 15 mmHg. CT-measured volume increased relatively by 93 % from 5 to 10 mmHg IAP and by 19 % from 10 to 15 mmHg IAP. Comparing CT volumes to insufflator volumes gave a bias of 76 mL. The limits of agreement were −0.31 to +0.47, a range of 790 mL. The internal anteroposterior diameter increased by 18 % by increasing IAP from 5 to 10 mmHg and by 5 % by increasing IAP from 10 to 15 mmHg. At 15 mmHg, the total relative increase of the pubis–diaphragm distance was only 6 %. Abdominal width did not increase.
Conclusions
CT allows for precise calculation of the actual CO
2
pneumoperitoneum volume, whereas the volume of CO
2
released by the insufflator does not. Increasing IAP up to 10 mmHg achieved most gain in volume and in internal anteroposterior diameter. At an IAP of 10 mmHg, higher peak inspiratory pressure was significantly elevated.