don’t CHEAT a heart

Hey, there. It’s been awhile.

This post is for nurses who care for patients immediately following open-heart surgery, but most of it applies to any patient. I mean, since they all have hearts. Or so I assume.

The top six concerns for patients following open-heart surgery…


Cold. Cold is the first problem with open-heart surgery. Cold hearts are bradycardic hearts. What do we see in induced hypothermia? Exactly. Bradyarrhythmias.

Open heart surgeries come back to us with epicardial leads–often both atrial and ventricular, but sometimes they will only have a V lead. Keep your patient connected to the pacemaker, ensuring both capture and sensitivity are appropriate for your patient.

While you’re at it, mark the end of the V cable with a piece of tape. Do not mark both. In an emergency it’s really hard for someone under stress to see the difference between an A and a V.

Mark the V lead only.

If you’re having difficulty maintaining cardiac output and your patient’s heartrate is less than 80, consider turning on the pacer to 90 bpm. Definitely will not work on everyone, particularly if you only have a V lead. Pesky atrial kick, amirite?

Cold doesn’t just increase the odds your patient will be bradycardic. It also increases the odds of atrial and ventricular arrhythmias, and could lower the vfib threshold.

It also causes vasoconstriction. What happens to your hands when you go outside in cold weather? Peripheral vasoconstriction, right? That’s increased afterload (SVR) in action, as well as elevated filling pressures. Another thing cold does–reduces the clearance of anesthetic and sedative medications.

Warm your patient up. Remember, if they aren’t 36 degrees C when they hit the door anesthesia loses their 5%, so they want to hit that mark. Warm blankets or the forced-air warmer are available.

Cold does another thing. It influences coagulopathy. Hypothermic patients bleed more, right?

*Really has no effect down to 35C. Below 35C but above 33C you may see some mild platelet dysfunction. Below 33C the coagulation cascade is affected, but rarely will you ever see an open heart patient come back this cold.

It also precipitates shivering. Shivering increases lactic acid production, CO2 production, and O2 consumption, which brings us to H.


Hypoxia–tissue ischemia–is the next consideration. This may or may not be reflected in the ABG alone due to the way oxygen dissociates from the hemoglobin, the amount of circulating hemoglobin, or the presence of methemoglobin.

Here’s where I reference that horrible oxyhemoglobin dissociation curve we all remember being dense about in physiology.

No, it’s not that bad. In fact, I’m not even going to bring it up. How about that. Important thing to understand is that hypoxic patients are more prone to dysrhythmias. An ischemic heart is an unhappy one.


No, it’s not exanguination. Although that would be bad. Everyone remember the old saying, “Surgical bleeding is bleeding you can hear”? It rushes, dumping in the chest tubes.

If you hold the chest tubes level with the insertion point and blood fills them, that’s an indication for urgent return to the OR. All roads lead rapidly to a resternotomy.

Electrolytes. The heart simply adores magnesium and potassium and calcium. Typical goals in a post-op heart surgery:

K+ >4.2 mEq/L

Mg++ >2.2 mEq/L

ionized Ca++ >4.7 mg/dL.

Low-normal levels of potassium and magnesium predispose an irritated heart to dysrhythmias, which is why our goals for replacement are a touch supratherapeutic, but not high.

Ionized calcium is the amount of circulating calcium not bound to albumin, which means it’s the bit of the electrolyte that’s free to do work–clotting, muscle relaxation, contractility–and this last function is the one we’re interested in.

Most open-heart protocols require you to check these electrolytes with an ABG and CBC fifteen to twenty minutes after arrival and four hours later. Because things change, yeah? Sometimes quite unexpectedly. If your open-heart protocol doesn’t require ionized calcium, check one anyway. Tell ’em Eve said so.

Nah. Tell them that, in light of blood product administration and relative tenderness of the myocardium following surgical manipulation, you wanted to ensure there were adequate amounts of calcium ions to do the work. Tilt your head to the side, wink and smirk as you say it. Or not.


This next one is a biggie. Acidosis. Obviously acid-base balance affects heart function. Acidosis impairs contractility. As it turns out, the body requires the blood supply to be a certain pH for proper functioning. Even oxygen…oh. Yes. There we are again, at the oxyhemoglobin dissociation curve. Yes. I promised I wouldn’t bring it up. Ok, fair.

Let’s not be acidotic. Query me this: what is the fastest way to correct an acid-base imbalance safely?

Did you say by increasing the respiratory rate? DING DING DING. Yes. And the tidal volume. Which is…what Kussmaul respirations are. You guys remember those, right? The deep, rapid respirations of metabolic acidosis? Oh, DKA is the classic example. But our patients, our immediate cardiac post-op patients, the ones who are anesthetized and chemically paralyzed, they are unlikely to be capable of mustering said response, correct? Which means we must help them.

Except maybe not blow their lungs with high tidal volume. So. Rate is the way to go.

Oh, and by the way–let’s not give a ton of sodium bicarbonate. I mean, every amp you give you’ll pay for later. It dissociates in the serum to make NaCl and CO2…so…yeah…


Touch. We fiddled with that heart. Hearts don’t like to be touched. Just sayin. And yes, it’s almost Valentine’s Day. Take it from the twice divorced mom of five. Hearts are tender. They can’t take a lot of rough handling. Most post-ops experience myocardial depression for 6-12 hours after surgery, with a drop in ejection fraction of 10-15% even when hyperdynamic on pre-op TEE.

You think the LV is the whole story?

Got another think coming. If the LV is occasionally fussy, the RV is a straight bitch. Any intervention on the right side, affecting the right side, and you need to consider primacor or dobutamine for forward flow. Low-dose epinephrine will also work, say, 0.02-0.05 mcg/kg/min.

Know your surgeon and your patient.