Gastric intramucosal pH during lower body circulatory arrest under open distal anastomosis with selective cerebral perfusion in aortic arch repair.

Selective cerebral perfusion (SCP) and open distal anastomosis (OD) with hypothermia has been used as a popular means for circulatory assistance in aortic arch surgery. Although SCP has become accepted for brain protection, the influence of OD accompanying circulatory arrest on lower body ischemia is not known. We studied gastric tonometry (gastric intramucosal pH [pHi]) to estimate splanchnic ischemia during OD, and its relationship to postoperative organ function. In five patients (pts) (range, 65-78 years; mean, 71 years; group OD) who underwent arch replacement using SCP and OD with moderate hypothermia (25 degrees C) during the period from March to August of 1999, pHi was measured precardiopulmonary bypass (pre-CPB), 30 min of CPB (CPB30), 10 min after OD (OD10), at end of CPB, and post-CPB. Eight pts (range, 52-78 years; mean; 66 years) who underwent standard CPB (33 degrees C) during the same period (coronary artery bypass surgery in six and valve surgery in two) served as controls (group C). In group OD, pHi was significantly decreased at OD10 (7.35 +/- 0.03 at CPB30 vs. 7.23 +/- 0.07 at OD10, p < 0.05) but recovered by the end of CPB (7.32 +/- 0.02). Creatinine clearance on the first postoperative day (1POD) was significantly (p < 0.05) lower in group OD (82 +/- 40 ml/min) than in group C (126 +/- 25 ml/min), although there was no significant difference in preoperative values between the two groups. The pHi at OD10 did not correlate with the duration of OD (range, 30-47 min; mean, 38 min), whereas pHi at OD10 significantly correlated with BUN (r = -0.973, p = 0.0054), Cr(r = -0.977, p = 0.0043), and CCr (r = 0.908, p = 0.0328) on 1POD. One patient in group OD developed paraplegia and renal failure postoperatively. His pHi at OD10 was severely decreased to 7.11. These results suggest that intraoperative monitoring of pHi may be useful for the evaluation of visceral organ ischemia during OD in arch replacement and may contribute to improved technique for circulatory assistance in aortic surgery.