Videoendoscopic endotracheal intubation in the rat: A comprehensive rodent model of laparoscopic surgery

Peritoneal absorption of CO ₂ during abdominal insufflation in laparoscopy may disrupt the acid-base equilibrium and alter the physiological response to stress. Current nonventilated rodent models of laparoscopy do not manage the CO ₂ load of pneumoperitoneum, but ventilated surgical rodent models are invasive (tracheotomy) and may independently induce the inflammatory response. A comprehensive rodent model of laparoscopy was developed. Rats were randomized to receive anesthesia alone, anesthesia plus CO ₂ pneumoperitoneum, or anesthesia plus CO ₂ pneumoperitoneum with videoendoscopic intubation and mechanical ventilation. Arterial blood-gas analysis was performed at baseline and after 30 min of intervention. Baseline pH, pCO ₂, and HCO ₃ ^- arterial blood gas parameters were normal for all rats. After 30 min, pCO ₂ and pH changed slightly but remained normal among rats receiving anesthesia alone (pCO ₂ = 46.5 ± 1.9; pH = 7.365 ± 0.009) whereas animals receiving anesthesia plus CO ₂ pneumoperitoneum that were dependent on spontaneous respiration for ventilation developed significant hypercarbic acidosis (pCO ₂ = 53.2 ± 1.9, P < 0.05; pH = 7.299 ± 0.011, P < 0.001). This acidosis was completely corrected with increased minute ventilation in intubated rats receiving mechanical ventilation (pCO ₂ = 36.8 ± 1.5, P < 0.001; pH = 7.398 ± 0.011, P < 0.001). CO ₂ pneumoperitoneum induces significant hypercarbic acidosis in nonventilated rats. Noninvasive endotracheal intubation is feasible in the rat with videoendoscopic assistance. Our noninvasive rodent model of laparoscopic surgery controls for anesthesia- and capnoperitoneum-related acid-base changes and provides an environment in which the biological response to pneumoperitoneum can be studied precisely.