Relationship among sigmoid pHi, blood lactate and outcome in surgical patients of abdominal aortic aneurysm

Introduction

Many works have shown the relationship between the outcome of surgical critically ill patient and oxygen availability of the body. Many factors cause an insufficient oxygen availability: tissutal traumatism with the consequent beginning of the inflammatory cascade, anemia, hypotension due to the blood losses, anesthesia. Shoemaker has called this alteration as 'oxygen debt' and has demonstrated that patient outcome is directed correlated to it and that this oxygen debt must be extinguished as soon as possible. The higher is the oxygen debt, higher is the risk of multiple organ failure and death. The gut has certainly a prominent role to determine these two last events and previous studies have shown the importance of a low gastric perfusion to cause death, measuring intramucosal pH with a gastric tonometer. A previous study has shown a correlation between IL-6 levels and outcome in major abdominal surgery. Now we have done a work to investigate the correlation between gut hypossia, measured with sigmoid tonometry, during aortic clamping for abdominal aortic aneurysm operation, and patient outcome.

Materials and methods

It was a prospective study on a series of 13 patients operated for abdominal aortic aneurysm. These patients were monitored with a sigmoid tonometer and pHi was detected at some times, together with arterial blood lactate and blood lactate of portal vein. These parameters have been detected at these times: at the beginning of anesthesia (t0), before aortic clamping (t1), 30 min after aortic clamping (t2), just after the operation (t4). The portal blood have been taken only in the first two times by the surgeon.

Results

Data have been divided in two groups following the developing or not of organ failures (OF) in the postoperative period. Seven patients had not organ failure, while among the other six patients, one died for MOF and the other five developed organ failures: three patients had acute renal and two cardiac failure. Arterial blood lactate trend was not significatly different between the two groups. Tables 1 and 2 show portal blood lactates and pHi trend. Patients with organ failure had a drop of sigmoid pHi with an increase of portal blood lactate after aorta declamping. At T4 pHi was still significatly lower in patients with OF. Fisher exact test has shown a significative relationship between pHi < 7.15 at 30 min after declamping and outcome (P < 0.05).

Table 1

Table 2

Conclusions

Patients operated for abdominal aortic aneurysm often have organ failures in the postoperative period. The developing of organ failure is correlated with the gut ischemia which happens in the intraoperative period. In fact from these preliminary data patients with a persistent drop of pHi < 7.15 had organ failure in the postoperative period.