A Day in Cardiac Anesthesia
As many of you who follow this blog know, I’m currently finishing up my anesthesia residency. While I certainly am happy to answer questions about specialty choices in general, it’s not a secret I’m biased to the field of anesthesia (good lifestyle, procedural medicine, with great pay, what’s not to love). I just finished up a month doing specifically cardiac anesthesia and I wanted to post about the awesome experience I had.
I think of cardiac anesthesia as the pinnacle of anesthesia care. Everyday the patients you put to sleep are the highest of risk. Critical aortic stenosis, severe mitral regurgitation, symptomatic coronary artery disease – seeing these terms on the H&P of a patient certainly catches the nerves of most anesthesiologists. Yet these patients need their medical problems addressed and need someone to get them safely through the procedures. Here was the typical day on my cardiac rotation. (Note: patient in this story is fictional, any likeness to patients, attendings, hospitals, or academic centers is purely coincidental).
Arrive to the hospital, 5:45AM. Change into scrubs. Check the assignment board. I’m in room 32 – aortic valve replacement. I’ve looked the patient up the night before, he’s mid 70s with symptomatic critical aortic stenosis. The usual co-morbidities – HTN, HLD, DM2. Once an aortic valve stenosis becomes symptomatic, if untreated, a patient will usually die within 2-5 years. This patient desperately needs this fixed.
His cardiac cath report luckily shows only mild non-obstructive coronary disease. His pre-op echocardiogram demonstrates his critical aortic stenosis, some left ventricular hypertrophy, but otherwise is fairly normal. His ejection fraction and LV function are also luckily normal.
I quickly set up the room for the day. Check out the anesthesia machine. Set up a couple IV lines, an art line, get out my airway equipment, draw up drugs, and head over to see the patient.
Since I’ve looked up the patient the night before (and cardiac patients are usually very well worked up), I keep my preop H&P brief and focused to anesthesia. I want to insure the the patient is appropriately NPO, check allergy history, ask about anesthesia history, briefly confirm medical history, and ask about functional status (i.e.how symptomatic the patient is). Then a quick focused physical exam to mostly address the patient’s airway and my ability to intubate with ease.
I then talk to the patient about the anesthesia plan and the risks. There are a million styles to doing this – mine is both detailed but to the point. I like patients to know what to expect before we go to sleep, what extra lines/procedures I’m planning to do, the general course of the operation, and basic risks of everything I’m doing. You have only a few minutes to talk to patients, and I want to give the impression I’m competent, thorough, and confident I can safely get them through this operation. Anesthesia is the specialty where first and often only impressions count the most and I pride myself on this aspect of my care.
I then go discuss the case with the attending, who has the luxury of arriving a little later than I do. We go over the hemodynamic goals in a patient with aortic stenosis. Because the lesion is stenotic, lower heart rates are ideal to allow adequate time for systolic election against the fixed lesion. Tachycardia must be absolutely avoided and quickly treated, usually with a short acting beta blocker such as esmolol. In the case of any tachy-arhythmia, such as atrial fibrillation, prompt defibrillation must be performed as these patients generally are very dependent on that the addition of atrial kick. It is also essential to maintain adequate systemic vascular resistance and blood pressure. AS patients have very hypertrophied, muscular hearts, which have high oxygen demands. This along with their elevated end diastolic pressure from ejecting against the stenosis, places them at a constant threat of ischemia with only minimal drops in blood pressure (remember Coronary Perfusion Pressure = End Aortic Diastolic Pressure – End LV Diastolic pressure).
The scary scenario with AS is if a patient drops their vascular resistance from the anesthesia induction medications, which leads to a drop in blood pressure, which then leads to cardiac ischemia. If left untreated, the cardiac ischemia will decrease cardiac output and further lower blood pressure causing even more ischemia. This “death cycle” can be very hard to recover from once the original insult occurs. Lastly, because the stenosis is so severe in these patients, chest compressions are essentially impossible as a rescue.
Back to our case: We place a pre-induction “awake” arterial line to be able to carefully monitor our hemodynamics throughout induction. Then we got off to sleep with high dose Midazolam and Sufentanil to provide a very stable induction and then paralyze with rocuronium. We maintain anesthesia with inhaled anesthetics and small boluses of narcotics as needed. After intubation, we place a left subclavian quad-lumen central line, and then a right internal jugular introducer for the pulmonary artery catheter (Swan line). These cases often have 2 central lines, and it was not uncommon for me to place anywhere from 2-6 CVLs a day in this rotation – great for learning my own style and improving my efficiency.
After our lines are in, the nurses are busy placing a foley and then prepping/drapping the patient. We have moved on to performing a Transesophageal echocardiogram (TEE). This involves inserting a echo probe down the esophagus to get real time pictures of the heart. This allows us to monitor volume status, evaluate heart function, and look for cardiac valvular disease. We go through each aspect the same, but in this case, finally focus in on the aortic valve. We confirm the critical aortic stenosis but note no other pathology and normal heart LV function.
Next we are in tight contact with the surgeons as they are working on getting through the chest. As they progress, we eventually “heparinize” the patient to a goal ACT of 450+. This is to prevent the patient’s blood from clotting in the bypass machine. As they prepare to place the aortic cannula to begin bypass, we need to also lower the patient’s blood pressure. Usually you want <100 systolic to avoid the risk of aortic dissection during cannulation. We accomplish lowering BP through careful titration of nitroglycerin, more high dose narcotics, and inhaled anesthetics. After the bypass cannulas all are in place, the bypass perfusionist turns on and increases flows to the patient – we can stop ventilating the patient and now essentially turn over care of the patient to the perfusionist and surgeon. Time for a cup of coffee!
The surgeons will replace the aortic valve in about 1.5 hours. This goes smoothly and it’s time to start planning how we will come off bypass. There are several ways and drugs to help in this regard, though norepinephrine is the favorite at this institution. Dopamine, dobutamine, milirone, and epinephrine are also not infrequently used. In this case, given the patients normal LV function, we expect the heart to function ok and will mostly need to augment vascular tone post bypass. Because of its strong alpha effects, norepinephrine is a great choice for this.
As the perfusionist decreases their support of the heart, we are closely monitoring the blood pressure and also using the TEE to get a real time look at the heart. The heart function appears excellent and is clearly happy to no longer be beating against the high resistance of a stenotic aortic valve. We continue to titrate our norepinephrine to maintain vascular resistance and a stable blood pressure. As the surgeons take their bypass cannulas out, we slowly start to reverse the effect of the blood thinning by heparin with protamine. Protamine works by binding the heparin molecule, but if given too quickly can lead to CV collapse through histamine release or allergic anaphylaxis. The perfusionist will also prepare several units of the patient’s own blood back from the pump and tubing, which we can administer to the patient. Once the surgeons are finished closing the patient’s chest, we then take the patient sedated and still intubated over to the ICU. They will hopefully be extubated in a few hours. But for us, it’s luckily time to call it a day!
Hopefully this gives the readers an idea of what a cardiac anesthesia day is like. There are a million other details that I could have included, but this is the most basic representation I could come up with. I love the field, and plan to do healthy hearts as an attending next year. I would have enjoyed a fellowship in cardiac anesthesia to be able to confidently take care of higher risk hearts, but my wife and I are looking forward to me being done with residency even more 🙂
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