Endoluminal pulse oximetry in ischemic colon in a swine model

Postoperative sigmoidal ischemia after aortic grafting is a severe complication. No simple methods are available to detect this entity at an early stage. This study was done to monitor for sigmoidal ischemia with a new endoluminal probe based on pulse oximetry (SmO2).

A prospective controlled animal study was done. Five pigs with low flow in the caudal mesenteric artery (20 percent of the basal flow) and four pigs in a control group were included. General and local circulatory parameters were monitored in the carotid and pulmonary artery and in the caudal mesenteric vein (CMV). Mucosal biopsy specimens were taken for histologic examination. Statistical analysis was done with the Wilcoxon and Mann-Whitney rank sum test and with analysis of variance.

During the first two hours of ischemia, no sigmoidal pulse was detected. During the third hour, in three pigs the pulse curve reappeared with a SmO2 of 48 to 88 percent. After two hours, the mean oxygen saturation in the CMV of the ischemic group was 64 percent (compared with the control group, 77 percent, p < 0.05). After one hour, the mean lactate concentrations were 2.0 and 1.3 mmol per L, respectively (p < 0.05). Significant histologic changes occurred with neutrophilic infiltration in the crypts, in the lamina propria, and in the submucosa.

Low-flow sigmoidal ischemia can be detected and monitored with endoluminal pulse oximetry in this model of early sigmoidal ischemia.