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Sigmoid and gastric tonometry during infrarenal aortic aneurysm repair
R Englund1, N Lalak, T Jacques
1Department of Vascular Surgery, St George Hospital Kogarah, New South Wales, Australia.
Background:
The value of the sigmoid tonometer in predicting sigmoid ischaemia and postoperative enteric organism infection has been reported but the value of tonometric measurement has been challenged. The purpose of this study was to examine the use of tonometric measurements in a series of patients undergoing infrarenal aortic aneurysm repair.
Methods:
We assessed the results obtained when sigmoid (n=11) and gastric (n=8) tonometry were performed in patients undergoing infrarenal aortic aneurysm repair (n=11). We measured blood flow ultrasonically (n=6) in the inferior mesenteric artery(IMA) and IMA stump pressures. Sigmoid and gastric tonometry were measured prior to clamping of the infrarenal aorta, during cross clamping and after clamp release at 1, 4, 16 and 20h. Ultrasonic flow was measured before clamping. Stump pressures in the IMA were measured before, during and after clamping.
Results:
The IMA was chronically occluded in five patients. The IMA flow was 37.5 +/- 8.7 mL/min (mean +/- s.e.). The mean IMA stump pressures before, during and after clamping were 64 +/- 13, 48 +/- 8 and 69 +/- 10 mmHg, respectively, and did not differ significantly. Mean systematic arterial pressures at these times were 89 +/- 7, 95 +/- 5 and 86 +/- 8 mmHg. These did not differ significantly or when compared with IMA stump pressure. The gradient between systemic arterial pressure and IMA stump pressure did not vary significantly at any of these times. Sigmoid and gastric intramucosal pH (pHi) did not differ significantly at any of the above times. Both sigmoid gastric pHi dropped on clamp application but 4 h afterwards had returned to baseline levels. Systemic arterial pH reflected significant ischaemia during clamping and shortly after release of the clamp(P=0.008).
Conclusions:
Tonometry may reflect systemic events as much as regional ischaemia. Useful tonometry results may depend on the development of a trend rather that individual measurements. The routine use of tonometry to detect intestinal ischaemia may not be cost-effective in aortic surgery.