may be increased cardiac out put

The answer above is incorrect....firstly the overall flow through a carotid shunt is quite small,and secondly,it is only performing the job of the native artery,bypassing it whilst the carotid is clamped and operated upon.

The real issues with carotid shunts are as follows:

1.Decision making process in inserting a shunt may take time,and in some cases may be incorrect,thus relying on good perioperative techniques for measuring or quantifying adequate cerebral blood flow such as TCD and INVOS.

2.Inserting the shunt into the carotid artery can result in dislodging plaque material distally during insertion,or occasionally dissection.

3.The shunt can be placed too far down into the common carotid,and may enter the subclavian origin and occlude flow to the arm,or lose flow through the shunt.

4.The shunt can be dislodged or blown out of the artery,neccesitating reclamping and replacement,with all of the above risk factors.

5.The shunt can interfere with visualising the operation site and may impede surgery to a small degree.

In short,if there is a lack of adequate monitoring of cerebral perfusion,a shunt can be thought of as mandatory by many,but if there is reliable and validated cerebral monitoring(such as INVOS or TCD),then shunting should only be performed where indicated.

Hope that helps.