[Intestinal ischemia after abdominal aorta surgery. A dreaded complication surveyed by a combination of different methods]

The article consists of a review of findings in previously published reports on intestinal ischaemia after abdominal aortic surgery. In a combined cohort and case-control study of 2,824 patients from the Swedish vascular registry, the incidence of intestinal ischaemia was 2.8%. The independent risk factors identified were preoperative shock, emergency surgery, renal insufficiency, advanced age, operation at a regional hospital, aortabifemoral grafting, ligation of one or both internal iliac arteries, bleeding > 10 litres, and operating and cross-clamping time. Cardinal symptoms were unreliable predictors. Sigmoidoscopy was potentially diagnostic in 95 per cent of cases. In a clinical study of 34 patients, sigmoid colon pHi was highly predictive of ischaemic colitis and other life-threatening complications. In a por-cine model of ischaemic colitis, blood flow in the superior mesenteric artery, colonic pHi and histological mucosal damage were unaffected by dobutamine.

The effect of dobutamine on distal colon ischaemia in the pig

OBJECTIVE

To test the hypotheses that dobutamine increases intestinal blood flow, it reduces mucosal acidosis and it prevents mucosal injury in an experimental porcine model of distal colonic ischaemia. And the hypothesis that mannitol prevents reperfusion injury.

DESIGN

Randomised animal experiment.

SETTING

University Hospital, Department of Experimental Research.

MATERIALS

Twenty-four pigs.

INTERVENTIONS

Twenty-one pigs were subjected to 7 h of controlled non-occlusive intestinal ischaemia of the distal colon, consisting of an occlusion of the inferior mesenteric artery (IMA) and a constriction of the superior mesenteric artery (SMA). At 3.5 h six pigs were treated with dobutamine, six with mannitol (0.18 g/kgBW), six with dobutamine and mannitol and three served as controls. Three non-ischaemic pigs were treated with dobutamine.

MEASUREMENTS AND RESULTS

All animals were haemodynamically stable throughout the experiment. There was no difference in any variable between the animals treated with mannitol and those not treated. The ischaemic dobutamine-treated animals increased their cardiac output (CO) by 14% compared to baseline and by 59% compared to controls. The median final dosage of dobutamine was 13.2 micrograms/kg per min (range 8.6-25.8). The blood flow in the restricted SMA, the intramucosal pH of the colonic mucosa (pHi) and the degree of histological mucosal injury were identical in animals treated with dobutamine and controls. The pH gap (pHa-pHi) correlated well (r = 0.97) with the PCO2 gap (aPCO2-intestinal PCO2). The non-ischaemic animals treated with dobutamine increased CO by 37% and blood flow of the SMA by 16%.

CONCLUSIONS

Dobutamine increased CO but did not ameliorate or deteriorate colonic ischaemia in this experimental model. The PCO2 gap correlated well with the pH gap.

An experimental porcine model of partial ischaemia of the distal colon

OBJECTIVE

Ischaemia of the colon is a major challenge in aortoiliac surgery. The aim was to establish an animal model of partial distal colonic ischaemia to study interventional strategies.

DESIGN

Randomised experiment.

SETTING

University Hospital. Department of Experimental Research.

MATERIAL

19 pigs.

INTERVENTIONS

11 Pigs were subjected to ischaemia consisting of total occlusion of the inferior mesenteric artery and partial occlusion of the superior mesenteric artery. Eight animals were sham controls. Dextran was given.

MAIN OUTCOME MEASURES

Haemodynamic measurements, intramucosal pH-measurements (pHi) and histological grading.

RESULTS

Both ischaemic animals and controls remained haemodynamically stable. It was possible to maintain stable ischaemia in the distal colon in the pHi-range of 6.9-7.1. There was histological mucosal damage of the distal colon in ischaemic animals but not in controls.

CONCLUSIONS

The model could be of value when studying interventional strategies to reduce or reverse ischaemia.

Risk factors for intestinal ischaemia after aortoiliac surgery: a combined cohort and case-control study of 2824 operations

OBJECTIVE

To identify risk factors for intestinal ischaemia after aortoiliac surgery.

MATERIALS AND METHODS

Among 2824 patients operated on during 1987-93 and registered prospectively in the Swedish Vascular Registry, 62 cases of postoperative intestinal ischaemia were identified. They were compared with the remaining 2762 patients through the registry and with a random sample of 127 controls through patient records. Multivariate analysis was performed.

RESULTS

Patients in shock operated on for ruptured aneurysms were at greatest risk of developing postoperative intestinal ischaemia. Excluding patients in shock, operation for aneurysmal disease and for occlusive disease carried the same risk. Renal disease, emergency surgery, age, type of hospital, aortobifemoral graft, operating time, cross-clamping time and ligation of one or both internal iliac arteries were independent risk factors.

CONCLUSIONS

Patient-related haemodynamic risk factors together with surgical skill and decision making defines the risk for this serious complication.

Incidence and clinical presentation of bowel ischaemia after aortoiliac surgery--2930 operations from a population-based registry in Sweden

OBJECTIVES

To study the incidence and clinical presentation of intestinal ischaemia after aortoiliac/femoral surgery, and to validate a vascular registry concerning a serious complication.

DESIGN AND SETTING

In the Swedish Vascular Registry (SWEDVASC) the outcome and complications of all vascular procedures are registered prospectively.

MATERIALS AND METHODS

All 2930 patients operated in 1987-93 were analysed for notified complications. A 5% random sample of all patients and a 20% random sample of fatal cases were analysed for un-notified complications. Of 415 requested patient records 413 were analysed.

RESULTS

The estimated incidence of bowel ischaemia was 2.8%. Among patients operated on for a ruptured aneurysm in shock it was 7.3%. Of the 63 patients with intestinal ischaemia only 15 presented with early passage of bloody stools. In 60 patients (95%) the lesion affected the left colon within the reach of a sigmoidoscope. Bowel ischemia was unnotified only in fatal cases, the estimated un-notified complication rate was 0.7%.

CONCLUSIONS

The incidence in this study on unselected patients did not differ from previous reports from specialised centres. Diagnosis is difficult and justifies a high index of suspicion and early use of sigmoidoscopy. The validity of the SWEDVASC registry was confirmed by a high report-rate for this complication.

Early detection of major complications after abdominal aortic surgery: predictive value of sigmoid colon and gastric intramucosal pH monitoring

The early detection and reversal of gastrointestinal ischaemia is thought to play a key role in minimizing the incidence of complications after abdominal aortic surgery. In an open prospective non-selective study intramucosal pH (pHi) was monitored in 27 patients undergoing elective aortic surgery and in seven submitted to emergency procedures. The pHi was monitored in the sigmoid colon in all 34 patients and in the stomach in 26. Eight patients developed major complications, four of whom had ischaemic colitis, and five died. Sigmoid acidosis (pHi below 7.10) served as an early warning; if acidosis was reversed within 2 h no major complication developed, if prolonged it was predictive of major morbidity (sensitivity 100 per cent, specificity 92 per cent). A colonic pHi below 6.86 predicted endoscopically detectable ischaemic colitis. A gastric pHi below 7.20 predicted major complications with a sensitivity of 100 per cent and specificity of 81 per cent. Both monitoring procedures were considered feasible, although monitoring in the sigmoid colon was found to be superior for the patients studied.