What is a Cross Clamp?
A cross clamp is a surgical instrument used to isolate the heart from the rest of the body's circulation during procedures on and around the heart. This results in a state known as cardioplegia, where the heart is not beating. In surgeries where the heart needs to be stopped, there are a number of risks, addressed by keeping the surgery as short as possible and taking protective steps such as chilling the heart to prevent damages associated with ischemia, where no blood is flowing through the organ. The alternative is a beating heart surgery, where the heart is allowed to beat freely and the surgeon works around it, but this option may not always be available.
Also known as an aortic cross clamp, this instrument is designed to be clamped down on the aorta to stop the flow of blood from the heart. Depending on the type of procedure, it may be left on continuously or the surgeon may use a technique called cross clamp fibrillation, where the clamp is periodically relaxed to allow the heart to reperfuse with blood. The surgical team monitors the patient throughout the surgery for signs of distress, and a cardiothoracic surgeon usually supervises.
There are some risks with the cross clamp. One is damage caused by ischemia, as tissues will die when deprived of oxygen long enough. Chilling the heart first reduces this risk, as the cold slows the rate of damage. Patients can also develop clots, potentially leading to a blockage of a vein or a stroke. In addition, sometimes releasing the clamp causes a reperfusion injury, and the removal of the clamp must be conducted with care.
Like other surgical instruments, the cross clamp is made from surgical-grade steel, a steel product specifically developed for use in operating rooms. This steel is strong, with some flexibility to prevent it from snapping under stress. It resists rust and can also endure very hot and cold temperatures, allowing people to use it in chilled procedures, as well as autoclaving it between surgeries.
After surgery, all of the tools are counted to confirm that everything used in the surgery has been accounted for. They are soaked in antiseptic solution and scrubbed before being packaged for an autoclave, a device that uses high heat to kill infectious organisms. Autoclaved medical instruments are safe for use in new patients, and tools may remain in use for years or even decades.
The cross clamping itself should be much less than that. The surgery itself takes about four or five hours, depending on the type of surgery.
One clarification: The heart beats because of the SA node, not because of the blood flowing into the heart. Because the heart beats, it can fill and empty the blood.
Am I right in assuming that cross clamps, or at the fibrillation procedure, would be more likely to be used in surgeries that were focused on something around the heart and not on the heart itself?
I have no idea whether this would ever happen, but for example, if you were having surgery to remove something from around your lungs, it seems like a cross clamp would be more useful. The surgeon could block off the aorta or other arteries so that they didn't cause problems while the surgery was happening. When the heart needed more oxygen, they could just release the clamps and then reset them quickly.
@TreeMan - If you aren't squeemish, you can find videos of open heart surgeries online. They are fascinating if you are at all interested in medical procedures.
Obviously, the exact type of surgery determines the length of time it takes, but I think they are usually in the ballpark of 2 or 3 hours. I have heard of ones taking over 24 hours, though.
In the videos I have seen, they actually do have a machine that reroutes the blood through the body after they use the cross clamps to stop the blood flow. The way they freeze the heart itself is with a potassium solution.
I never knew what the specific name of the clamps was, but they don't look much different than any other surgical clamps.
@jcraig - I was wondering how they got the heart to stop beating as well. How long does a normal cardiac operation last? How does that compare to how long the body can go without having oxygenated blood pumped through it? Is there any way that they could bypass the blood from the heart and run it through a machine that could pump it back into the body?
I was wondering, too. How are they able to freeze the heart? Surely they don't just use a bag of ice or something, do they?
I've never heard of this being done. I knew doctors had to stop the heart from beating for most procedures, but I never knew how they did it.
Is it really the blood flowing into the heart that makes it beat? I always thought the heart contracted on its own and forced blood through it.
As for the clamp itself, what does it look like and how is it applied?
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