Physiologic Changes in a Small Animal Model for Neonatal Minimally Invasive Surgery.

Background: Minimally invasive surgery (MIS) has gained increasing importance in neonatal surgery but the effects on neonatal physiology remain unclear. We aimed to characterize the impact of capnoperitoneum on physiologic parameters in a small animal model for neonatal MIS. Material and Methods: Twenty-four 10-day-old Sprague Dawley rats underwent inhalative anesthesia (1% isoflurane in 100% O-2 250 mL/minutes) and were allowed to breathe spontaneously. CO2 was insufflated into the abdominal cavity for 1 hour via a 24G cannula. Anesthetized litter mates without insufflation served as sham controls, those without any treatment as external controls. Continuous monitoring included O-2-saturation, heart and respiration rate, pulse and breath distension. After euthanasia, blood gas analysis was performed. Results: All animals survived the experiment. Capnoperitoneum was best tolerated at a pressure of 2 mmHg and a flow of 0.5 L/minutes. A significant decrease in heart rate was observed within the first 30 minutes of insufflation comparing the CO2 and sham group (P < .05). In both, the CO2 and sham group, postmortem pH-levels were lower and pCO(2) levels were higher compared to external controls (P<.05). Additionally, levels of pCO(2) were higher but pH levels remained unchanged in the CO2 compared to sham group (P <.05). Conclusion: We established a small animal model for neonatal laparoscopy. A pressure of 2 mmHg and flow of 0.5 L/minutes induced physiologic alterations but was well tolerated by the animals. These settings can be used in future studies on the impact of the capnoperitoneum in neonatal MIS.