Retrograde Cerebral Perfusion

Retrograde cerebral perfusion has been introduced as an adjunct to cerebral cooling as a means to protect the brain during periods of circulatory arrest. In this technique the patients body and brain temperature are cooled to 20-25°C by CPB.

After the heart lung machine is turned off a cannula is placed directly into the superior vena cava and blood at 10°C is perfused in a retrograde fashion at a rate of 300-500 ml/min. By observing dark blood emanating from the origins of the cerebral vessels in the aortic arch the surgeon confirms the presence of retrograde flow through the brain.

Retrograde cerebral perfusion allows the surgeon an even greater safe period of circulatory arrest at a specific temperature compared to not using retrograde perfusion. Alternatively it may reduce the need for cooling the patient to low temperatures to achieve the same safe period of circulatory arrest without retrograde perfusion. Cooling the patient to temperatures of 25-28°C rather than to less than 20°C may help to reduce the negative affects of hypothermia such as coagulopathy and cerebral edema.

Although retrograde cerebral perfusion does not provide blood flow to all areas of the brain it has the important advantage of ensuring that air and atherosclerotic debris are kept out of the cerebral vessels by maintaining a constant retrograde flow of blood in them.

During the period of circulatory arrest the anesthesiologist may choose to encase the patient's head in ice packs in order to promote cerebral cooling. In addition steroids may be given to help reduce cerebral swelling although there is little evidence that steroids are beneficial.

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