Use of near-infrared spectroscopy to monitor regional cerebral oxygen saturation during infrarenal aortic crossclamping in piglets

Purpose: The hemodynamic changes induced by infrarenal aortic crossclamping have been well documented, but the effects of such crossclamping on cerebral perfusion are unknown. To investigate these effects, we used near-infrared spectroscopy (NIRS) to monitor regional cerebral oxygen saturation (rSO₂) during infrarenal aortic crossclamping in a piglet model. Methods: The study involved 19 piglets, each weighing 7.8 ± 1 kg. The NIRS sensor was placed on each animal's forehead. General anesthesia was induced, and the infrarenal abdominal aorta was mobilized through a laparotomy. After heparin (1 mg/kg) was administered, crossclamps were applied proximally and distally. A 2 mm segment was resected from the proximal aortic stump, and an aortoaortic anastomosis was performed. Results: Crossclamping lasted for 30. 6 ± 6.7 min. Between the time of baseline measurement and clamp application, the rSO₂ did not decrease significantly (65.4% ± 8.9% vs. 62.4% ± 7.8%). However, significant decreases in the rSO ₂ occurred between baseline measurement and clamp removal (65.4% ± 8.9% vs. 55.7% ± 8.9%; P < 0.01), between baseline measurement and the end of surgery (65.4% ± 8.9% vs. 57.7% ± 7. 5%; P < 0.01), and between clamp application and removal (62.4% ± 7. 8% vs. 55.7% ± 8.9%; P < 0.01). At these same intervals, no intergroup differences occurred in the temperature, heart rate, or mean arterial pressure. Conclusion: Infrarenal aortic crossclamping significantly decreases the rSO₂. NIRS, which has the advantages of being non-invasive and continuous, may be useful for monitoring this variable intraoperatively.