Experimental mesenteric ischaemia in sheep: gut peptide release and haemodynamic changes

Anesthetic management of acute mesenteric ischemia in elderly patients

Ischemic insult to the splanchnic vasculature can jeopardize bowel viability and lead to devastating consequences, including bowel necrosis and gangrene. Although acute mesenteric ischemia (AMI) may occur at any age, the elderly are most commonly affected due to their higher incidence of underlying systemic pathology, most notably atherosclerotic cardiovascular disease. Treatment options include pharmacology-based actions, endovascular, and surgical interventions. AMI remains a life-threatening condition with a mortality rate of 60% to 80%, especially if intestinal infarction has occurred and surgical intervention becomes emergent. Early recognition and an aggressive therapeutic approach are essential if the usually poor outcome is to be improved. Anesthetic management is complex and must account for comorbid disease as well as the patient's presumptive acute deterioration. Blood pressure support typically involves careful, but often massive, fluid resuscitation and may also additionally require pharmacologic support.

Myocardial ischemia in intestinal postischemic shock: the effect of hypoxemic reperfusion

OBJECTIVE

The circulatory shock following intestinal ischemia-reperfusion injury has been attributed to hypovolemia. The purpose of the current study is to clarify the pathophysiology of this type of shock and to test the hypothesis that hypoxemic compared with normoxemic reperfusion improves hemodynamics.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-one pigs.

INTERVENTIONS

Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomized into two groups: a group that received hypoxemic reperfusion (HR group, n = 8) with a PaO2 = 30-35 and a control group reperfused with PaO2 = 100 mm Hg (control group, n = 13).

MEASUREMENTS AND MAIN RESULTS

Measurements included mean arterial pressure, cardiac index, pulmonary artery occlusion pressure, and requirements for fluids and epinephrine. Biopsies from the terminal ileal mucosa were taken for malondialdehyde measurements at baseline, at 120 mins of ischemia, and at 30 and 60 mins of reperfusion. A piece of left ventricle was obtained after 120 mins of reperfusion for histologic studies. Five of 13 animals of the control group died in intractable shock; no animal of the HR group died (p =.11). The decrease in the mean arterial pressure during reperfusion was more pronounced in the control group (p <.008) despite the larger doses of epinephrine administered, compared with the HR group (p <.02). During reperfusion, both groups exhibited a decrease in cardiac index; this was more pronounced in the control group (p =.0007). Pulmonary artery occlusion pressure increased during reperfusion in both groups and was more pronounced in the control group (p =.04 at 60 mins). Although mixed venous blood oxygen saturation of the control animals was higher at 30 mins of reperfusion (p =.005), it declined after 60 mins and became lower than that of HR animals at the end of reperfusion (p <.02). The myocardial histopathologic injury score was higher in the control group (2.0 +/- 0.69 and 3.4 +/- 0.89 for the HR and control groups, respectively; p <.03). The concentrations of intestinal mucosa malondialdehyde were significantly higher in the control group at 60 mins of reperfusion (p <.03).

CONCLUSIONS

Acute myocardial ischemia and left heart failure significantly contribute to the circulatory shock that follows intestinal ischemia/reperfusion injury and are attenuated by hypoxemic reperfusion.

Systemic inflammatory response and the splanchnic bed in cardiopulmonary bypass

The splanchnic bed undoubtedly undergoes sub-clinical injury in the majority of patients undergoing routine CPB. Dependent upon patient and perfusion factors, this injury may be self-limiting or develop through a cascade of inflammatory mediators into multisystem organ failure. The gut may be damaged by the bioincompatibility of CPB, but it is, as a consequence of hypoperfusion and dysoxia, also a major source of bacterial and nonbacterial inflammatory mediators.