Coronary Artery Bypass Grafts (CABG)

Below is the audio file for the TEXT of this module, so that you can listen to it like a podcast rather than reading it. The vide contains different content.

Coronary Artery Bypass Graft (CABG)

A CABG is a very common procedure, and if you’re working cardiac, chances are you’ll work with fresh CABGs or people with a history of one. Therefore, this section is going to be a little more robust than others.

What It Is

If a patient needs this procedure, a coronary artery is compromised to a certain degree. To maintain adequate perfusion to the heart muscle, the coronary artery (or arteries) must be bypassed. Meaning we must go around the blockage to ensure the tissues on the other side still get blood flow.

Typically, if this issue is known, medical management (medications and other therapies) is attempted first. This surgery is the next option if that is unsuccessful. A CABG is a very serious surgery with very real risks and should not be attempted unless absolutely necessary. However, patients will occasionally come into the emergency department with an MI, but no idea they have any cardiac issues (this is often because they have not seen a physician for a check-up in many years). In these emergency situations, surgery can be necessary immediately rather than attempting medical management.

Essentially, a vessel is used from another part of the body to create this bypass conduit to restore blood flow.

Think of this like an interstate. Let’s say the main interstate has degraded and deteriorated slowly, and one day the road becomes impassable, so cars start to back up. Maybe a few cars can get through, but not enough to sustain the flow of traffic to prevent a huge back up and accidents. So, to fix this issue, you have the cars get off at the nearest exit and take the smaller state highway instead, bypassing where the road has broken down.

Now, let’s talk about which vessels they use to make this bypass. They do not put in artificial blood vessels. Rather, they take a blood vessel from another part of the body. Some vessels work better than others, but they may be forced to use less than ideal ones due to the patient’s anatomy, damage to the desired vessel(s), pre-existing medical conditions, etc. Because they will be harvesting a blood vessel from another part of the body, you may see incisions in other areas that you will care for as well.

The left internal mammary artery (LIMA) and the right internal mammary artery (RIMA) are most frequently used because the ten year patency rate is approximately 80%. The saphenous vein graft (SVG) can also be used, but its ten year patency rate is closer to 50%. Typically, the LIMA is used for the left anterior descending artery (LAD) because it’s the most important vessel to support left ventricular function. So, they’ll snag one of these vessels and put that bad boy on the heart and bypass the compromised coronary artery. Check out this great photo that shows the bypass from the aorta past the blockage so the heart muscle distal to the blockage can get adequate blood flow. Amazing!

A patient may have one blockage bypassed, and you’ll hear people say a “one-vessel CABG” or see people write “CABG x 1” on their report sheet. Most of the time, you’ll see a two- or three-vessel CABG. The most we’ve seen before is a seven (oh my gosh!) vessel CABG. The more vessels being bypassed, the more vessels need to be harvested. Those patients will have more incisions on their arms/legs because they had to take vessels for the bypass.

How They Present to the Hospital

Some patients will come in for a planned CABG. The decision to do a CABG is made if the patient is not a good stent candidate, has diabetes or multi-vessel disease, left main artery disease, previous in-stent restenosis (meaning they already had stents and they become narrow again), or chronic occlusions not amenable to PCI (percutaneous coronary intervention).

In report, you may hear something like, “The patient presented to the ED with chest pain, and the cath showed multi-vessel disease. A three-vessel CABG was performed the following day.”

If they’ve presented to the ED and are stable with chest pain, yet we’re still trying to figure out what’s going on (and don’t know they need a CABG yet), they may head up to the cardiac floor to get some additional tests, such as serial ECGs and labs, and a cardiac cath. They’ll get their diagnostics done, get a cardiothoracic surgery consult, and schedule surgery as soon as appropriate. This may be for the following day or so, while they are on continuous cardiac monitoring, and we are watching their labs until surgery. It’s one of those “not safe to go home, but not urgent enough to necessitate emergency surgery” type of things. Patients can get frustrated because they may feel “fine” and not understand what the big fuss is about, but they do not understand the severely increased risk of a sudden MI they’re facing with each passing moment.

As the floor nurse in this situation, you’d be preparing them for surgery. You’ll chat about what to expect post-operatively. Things like mechanical ventilation, chest tubes, IVs, foleys, pain management, coughing, deep breathing, and all that jazz. They may be on a heparin drip before surgery, which you’d be managing. You’ll get things done—the clipper-prep, chlorhexidine bath, or whatever pre-CABG protocols your hospital has in place. Typically, the night shift takes care of all this, so the patient can head to surgery first thing in the morning. Once the patient heads down to pre-op, they won’t come back to the cardiac floor until they’ve been in the cardiac ICU for (typically) a few days.

Post-operative ICU Care

Patients will come up from surgery on a ventilator, and the length of time in which they are on the vent depends on how they’re doing. It can be as short as six hours or as long as multiple days.

They’ll also typically have mediastinal and pleural chest tubes that you’ll be in charge of managing. (Check out the chest tubes module for more information on these.) One of the important things is to note how much drainage you’re seeing. If you’re getting over 100–150 mL per hour out, that’s quite a bit, and the surgeon and/or their advanced practice needs to know.

The patient will also have epicardial pacing wires in place. These wires are put in place during surgery because dysrhythmias are common afterward, and it enables us to “pace” them with a bedside pacemaker, rather than using external pacer pads. Basically, they’ve got a few thin metal wires coming out of their chest and you’ll have to “maintain them” when not in use. Honestly, this is most of the time; you’re only using these in an urgent situation. This means keeping them covered up and secured so they don’t get pulled out accidentally. A lot of places will use an empty syringe to cover them and tape them together.

Kati’s Story

I once was taking care of a post-op CABG patient on the cardiac surgery floor. He was quite a few days post-op, but had multiple issues with dysrhythmias in the ICU, so they left the pacing wires in on him longer than they typically do. Normally, we would take the syringes the pacing wires are in and tuck them into the patient’s abdominal binder during ambulation, so they aren’t dangling down and at risk of getting pulled out. I was getting the patient out of the chair to go on a walk, and he heard and felt a pop in his chest. I was immediately terrified—I thought he just popped open his midsternal incision! It turns out, one of the pacing wires was stuck in the chair but tucked where I couldn’t see it. He’d basically pulled out his own pacing wire. I got him back in bed, and the surgeon happened to be rounding at the nurse’s station. So, I let him know. They were at the point where they were thinking about removing them, but had been leaving them in, just in case. He wasn’t upset, but I definitely learned a lesson: always make sure your pacing wires are secure before moving the patient!

Most likely, these wires will stay in place for the patient’s entire stay in the ICU and be removed when the patient is out on the cardiac floor, closer to discharge. Surgeons or advanced practice providers remove them at the bedside.

Should you need to use them, you’d plug them into a device that looks like what’s pictured below.

 

Blood pressure monitoring and treatment is crucial in this post-operative period. If the blood pressure is too low, the grafts could collapse. If it’s too high, it could cause leaking and bleeding. You’ll most likely have the patient on a few drips and watching that blood pressure closely on the patient’s arterial line. These drips will be infusing through a central venous catheter (CVC) that you will also need to maintain.

Generally speaking, you’ll probably see a goal of keeping the MAP between 65 and 70 and the SBP between 110 and 130, which would be ideal. This may change depending on physician preference and the situation, but as you can tell, that’s a pretty tight parameter to maintain! One thing to consider with blood pressure management is that not all patients are alike. There isn’t one blanket parameter that works for every patient. The ultimate goal is end-organ perfusion. Meaning we want to ensure our “end-organs”—like the brain, lungs, kidneys, and so forth—are getting enough blood. Therefore, if your patient has some comorbidities like renal issues or carotid stenosis, it would be reasonable to have a higher blood pressure parameter to maintain perfusion to those organs. There can be quite a bit of gray area with these parameters, as the unique needs of each patient are so dynamic.

Therefore, you need to know the physician’s orders for your patient. If you’re in step down or ICU, make sure your bedside monitor’s alarms are specific to your orders. The monitor’s defaults or the parameters from the previous patient may not be appropriate for your patient. It is extremely easy to miss this step, and then miss a blood pressure that is out of range because you were not notified.

This also will cut down on alarm fatigue. For example, if your parameters are to maintain an SBP of 110–160, but your alarm is set to go off for anything over 140, you may start to mentally disregard your blood pressure alarm because it goes off for everything from 141–160, which would not require action on your part.

Alarm fatigue is a very real and dangerous thing, so customize your alarms to your patient’s unique parameters to enable yourself to act accordingly and promptly.

Bottom line: Know your parameters, ensure your equipment reflects them accurately, and stick to them!

Electrolytes and fluids are also monitored closely. Potassium is usually aggressively treated, which isn’t a surprise. Generally speaking, you’re looking to keep it between 4.0-5.0 to proactively prevent the common post-operative complication of dysrhythmias. Your facility may have nurse-driven protocols in place for the frequency of the lab draws and potassium replacement. These can be cumbersome to learn, but once you get familiarized with them, they are pretty awesome and enable the nurse to work autonomously. This cuts down on calls to the physician or advanced practice provider significantly.

During the operation, patients are cooled. Once the patient comes up to the ICU post-operatively, they need to be re-warmed. Rewarming cannot be done too quickly, as it can result in neurological injury. Follow your unit protocol closely!

It is important to mention that when a cardiac surgery patient experiences a cardiac arrest, they are often resuscitated differently than your “normal” ACLS protocols for noncardiac surgery patients. Cardiac arrests post-cardiac surgery are covered in another module, entitled Cardiac Codes.

Post-operative Cardiac Floor Care

Once the patient heads out to the cardiac floor, they have been extubated and are stable. Infection prevention will be a huge focus for you, at this point. This means discontinuing lines as soon as it’s appropriate (and sometimes advocating to the surgeon or advanced practice provider when it may go unnoticed that a line is still in). The patient will most likely still have pacing wires and a chest tube or two. They will still have IV access and should only have a CVC if they truly need it. CVCs should be discontinued as soon as medically appropriate. This means the patient is no longer on drips and not receiving any medications that cannot be given through a peripheral IV. They’ll have their midsternal incision and possibly others. They may have a foley catheter, but hopefully they’re working their way toward getting that removed.

Instead of being assessed every four hours like in the ICU, these patients get a full head-to-toe assessment once per shift and whenever there are any significant changes. The goals shift from stabilization to increasing mobility and discharge-planning. Your facility may have the patient work closely with cardiac rehab, physical therapy, and occupational therapy, who will have some specific goals they must meet for discharge. Examples of these goals include walking a certain distance, traversing a flight of stairs, showering, etc.

As the nurse, you want to encourage maximum effort with therapy services. You may need to time some pain medication with therapy to ensure the patient is working to the best of their capabilities.

A big thing to monitor for is dysrhythmias. Approximately 40% of post-op cardiac surgery patients experience them. Remember: the more they did in the OR, the higher the risk for these complications. So, if your patient had a CABG x1, the risk for a-fib with RVR is much lower than a patient who had a combo CABG/AVR/MVR. These combination patients are the most likely to flip and really should be on a beta blocker unless there’s a good reason not to be.

Incision care and monitoring is another priority. They will have a large incision in the middle of their chest and preventing that from splitting open (dehiscence) is important. Patients with highest risk for dehiscence are those with whom the LIMA/RIMA was used because the blood supply to the sternum is decreased. Additional factors that can increase a patient’s risk of dehiscence are obesity and/or larger breasts (simply more weight for the incision), diabetes, steroid use, DMARD use for RA, or limited extremity mobility.

 

The patient may have something called “sternal precautions” ordered. However, the optimization of this is continually evolving and heavily researched by the physical and occupational therapy realm. There is a sweet spot between doing too much and not doing enough, and it’s different for each patient. However, generally speaking, you don’t want the patient to be pulling or pushing too much with their arms. Make sure you’re aware of your facility’s protocols and therapy’s recommendation.

Monitor the incisions for increased drainage, redness, tenderness, and all the typical signs of infection (like watching their WBC count and fever). The midsternal incision is the one you really want to watch closely, as an infection there can be much more serious than one on their leg or arm, due to its proximity to the heart and major organs. Follow your orders for dressing changes closely.

Pain management is also important. The degree to which patients experience pain varies greatly on the cardiac floor. If the patient still has a chest tube in place, they most likely will be experiencing more discomfort than if they have no lines. Also, surgeries that exclusively involve the lungs (like thoracotomies) tend to be much more painful than cardiac surgeries. When we’re looking toward discharge, the patient is typically only receiving oral acetaminophen or an acetaminophen/hydrocodone (Norco) oral combination every four to six hours. Patients cannot go home when on IV pain medication, and occasionally need to be educated on the fact that they will need to fully transition to oral medications before going home.

You may run into a patient or two who have unrealistic pain management expectations. Some expect full pain elimination during their entire hospital stay and do not realize how impractical that expectation is. We must educate them on the need for pain management rather than elimination.

“I understand that you really don’t want to feel any discomfort. However, if we were to give you enough pain medicine to eliminate all your pain and ‘knock you out’ this entire time, you wouldn’t be able to breathe. You also wouldn’t be able to do all those things that help your body heal, like walking, deep breathing, eating, and cardiac rehab activities. These all get you home faster. Staying in bed asleep around the clock will make you stay here longer and increase the chances of having serious complications, like pneumonia or blood clots. We want to get you home!”

Discharge Planning and Instructions

Most patients are going to move on to home health visits after this surgery. However, some may head to rehab or an extended care facility. This is determined mainly by the recommendations of the physical and/or occupational therapist and the surgeon. 

When they head to another facility, you’ll be working with case management to facilitate placement. Once this has been secured and the patient is safe to discharge, you’ll simply call report to that facility and get them on their way (via ambulance, medic, or a transportation service).

When discharging home, you’re going to provide the patient and their caregiver with some pretty detailed instructions. See the below audio file for an example of simple discharge instructions for a typical CABG patient who’s going home.

Please note this is an example, not actual prescribed discharge instructions. It is very general and not all-inclusive. Follow your orders and hospital policies when providing actual discharge instructions to real patients. 

Complete and Continue