Bladder mucosa pH and Pco2 as a minimally invasive monitor of hemorrhagic shock and resuscitation.

Background: Continuous monitoring of pH, Pco2, and Po2 using fiberoptic sensor technology has been proposed recently as a clinical monitor of the severity of shock and impaired tissue perfusion. Surrogates of gut tissue perfusion such as gastric tonometry, although cumbersome, have been used to indirectly quantify the degree of gut ischemia. The purpose of this study was to demonstrate the feasibility of monitoring bladder mucosa (BM) and to compare urinary bladder mucosa and proximal jejunum mucosa interstitial pH and Pco2 during hemorrhagic shock and resuscitation.

Methods: Eleven male miniature swine (25-35 kg) (control, n = 4; shock, n = 7) underwent jejunal tonometry and cystostomy. A multisensor probe was placed adjacent to the BM. Urine was diverted. Normocarbia was maintained. Animals were hemorrhaged and kept at a mean arterial pressure of 40 mm Hg. When a constant infusion was required to maintain the mean arterial pressure at 40 mm Hg (decompensation), animals were resuscitated with shed blood plus two times the shed volume in lactated Ringer's solution (20 minutes) and observed for 2 hours.

Results: During decompensation, BM pH values decreased significantly from 7.33 +/- 0.08 to 7.01 +/- 0.2 (p < 0.01) and recovered to 7.11 +/- 0.19 at 120 minutes after completion of resuscitation. During decompensation, BM Pco2 values increased significantly compared with baseline (from 49 +/- 6 mm Hg to 71 +/- 19 mm Hg, p < 0.05) and returned to baseline with resuscitation. Jejunum mucosa and BM interstitial Pco2 correlated throughout shock and resuscitation (r = 0.49). Bland-Altman analysis demonstrated significant differences between jejunum mucosa (intramucosal pH) and BM interstitial pH.

Conclusion: Shock-induced changes in the Pco2 of the BM are comparable to tonometric changes in the gut. These data suggest that continuous fiberoptic multisensor probe monitoring of the BM could potentially provide a minimally invasive method for the assessment of impaired tissue perfusion of the splanchnic circulation during shock and resuscitation.