Reperfusion Syndrome

Anticoagulation

Management After Treatment

Patients with embolic disease caused by cardiac arrhythmia or from other cardiac sources proven by ECG, medical history, or clinical signs should be anticoagulated postoperatively. Treatment regimens described previously are employed, followed by treatment with coumadin. Anticoagulation has no proven positive effect for the prognosis of the ischemic leg but is administered to reduce the risk of new emboli. The patient’s abilities to comply with treatment and the risk for bleeding complications have to be weighed against the benefits. If the source of the emboli is not clear, it should be investigated. Findings of atrial fibrillation and heart thrombus can then be treated. If the ECG is normal, echocardiography is ordered to search for thrombus and valve deficiencies. If the left atrium is a likely embolic source, transesophageal echocardiography may be indicated.

When the etiology of leg ischemia is uncertain it is difficult to give general advice. There is no scientific evidence that long-term postoperative anticoagulation reduces the risk of reocclusion or influences patient survival. Continued treatment with dextran or low molecular weight heparin is recommended at least during hospitalization.

If hypercoagulable states are suspected the patient needs to be worked up during the postoperative period to reduce the risk of reocclusion. Examples are patients with hyperhomocysteinemia, who may be treated with folates, and patients with antiphospholipid antibodies, who need coumadin and salicylic acid.

Patients treated for severe acute leg ischemia are at risk of developing reperfusion syndrome. This occurs when ischemic muscles are reperfused and metabolites from damaged and disintegrated muscle cells are spread systemically. A part of this process consists of leakage of myoglobin; it may be nephrotoxic and colors the urine red. The metabolites also affect central circulation and may cause arrhythmia and heart failure. The risk for reperfusion syndrome is higher when occlusions are proximal and the affected muscle mass is large. One example is saddle emboli located in the iliac bifurcation. The risk is also higher when the ischemia time is longer than 4–6 h.

The elevated mortality associated with severe acute leg ischemia may be due to reperfusion syndrome. Survival may therefore be improved by avoiding reperfusion and a lower mortality has been reported from hospitals where primary amputation is favored. It has also been suggested that thrombolysis saves lives by restoring perfusion gradually. For a threatened leg this is seldom an option because rapid restoration of perfusion is necessary to save it.

The best treatment for reperfusion syndrome is prevention by expeditious restoration of flow.

There are no clinically proven effective drugs but many have been successful in animal models, including heparin, mannitol, and prostaglandins.

Because heparin and mannitol also have other potential benefits and few side effects they are recommended during the postoperative period. Obviously, acidosis and hyperkalemia must be corrected, and the patient needs to be well hydrated and have good urine output. For patients with suspected reperfusion syn-

drome – urine acidosis and high serum myoglobin levels – alkalinization of the urine is often recommended in order to avoid renal failure despite weak support in the literature. If the urine is red, the urine pH <7.0, and serum myoglobin >10,000 mg/ml, 100 ml sodium bicarbonate is given IV. The dose is repeated until the pH is normalized.

Дата добавления: 2014-12-23