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Anesthesia

Low Blood Pressure after surgery

01/05/2007

Question:

My 75 year old father had double knee replacement surgery yesterday 1/4/06. His blood pressure never reached a level for him to leave recovery. He went straight to ICU. On 1/5/06 a.m., he received two pints of blood. His blood count had dropped below 30.0. His pressure has not changed much, 84/42....the top number has gone up some and then down but the bottom number really hasn`t changed. What are the reprocussions of a sustained low low blood pressure? Is there anything that should be happening here?

Answer:

A blood pressure of 85/42 is definitely on the low side for a 75 year old man. There is a wide variation in what is considered normal so one would want to know what his BP usually runs at. The most reliable number as far as blood pressure is concerned is the "mean" BP. A mean BP of at least 50 millimeters of mercury is what we generally aim for, usually a bit higher to be on the safe side.

The cause of low BP are many. There are general categories. There may be not enough circulating blood (e.g. bleeding). The heart may not be pumping adequately (heart attack, heart valve problems, abnormal heart rhythm or rate, the effects of drugs). The blood vessels that hold blood may be open too much ("vasodilation)(allergic reactions, infection, drugs). One cause of vasodilation is epidural anesthesia, which your father may have received for his double knee replacement. However the BP-lowering effects of epidural anesthesia are terminated after a few hours.

When the blood pressure is low the "vital" organs (heart, brain, kidneys) may not receive enough oxygen. The function of the vital organs decreases. If the ischemia continues long enough the damage may be permanent (heart attack, stroke, kidney failure).

Low blood pressure should be treated promptly while a search is undertaken for the cause. Supportive treatment includes oxygen, intravenous fluids or blood, and drugs which increase the pressure by acting on blood vessels or making the heart beat more strongly.

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Response by:

Gareth S Kantor, MD Gareth S Kantor, MD
Assistant Professor of Anesthesiology
School of Medicine
Case Western Reserve University