Q&A: Metabolic encephalopathy on a post-op sedated patient

Q: We had a physician document metabolic encephalopathy on a post-operative patient who was sedated on a vent. Prior to the surgery, the patient was alert and oriented to person, place, time, and event. Post-extubation one day later, they were alert and oriented to person, place, time, and event and on room air. There weren’t documented responses while on the vent and I was unable to clinically validate the encephalopathy while the patient was sedated on the vent. Do you have any suggestions for how to query this diagnosis’ validity?

A: This is certainly a challenging situation. Now if the patient had been altered prior to going on the vent, that would have been one thing. I would be a little concerned if the physician said that the encephalopathy was related to sedation, but it still is a possibility.

Some of the things that we would have to do is really think about the clinical assessment of this person through a combination of things—look at them clinically, probably do some lab tests in imaging, and do a few studies.

Metabolic encephalopathy is a term that is used to describe a group of conditions that is brain dysfunction due to a metabolic abnormality rather than a structural abnormality, like a structural brain lesion.

If we're going do the clinical validation, even though the patient was sedated and unable to respond, the provider can still actually get some good information from the medical history, their physical exam findings if those are applicable, observation of the patient's vital physical exam findings, and their neurology status and overall responsiveness.

Sometimes lab tests can provide a lot of valuable information about the patient's metabolic status as well, including their electrolytes. Electrolyte imbalance is certainly one of the causes of metabolic encephalopathy. Look for conditions like hyper or hyponatremia, hypo or hyperkalemia, and, of course, hypo or hypercalcemia. And then, ending that off with checking for hypoglycemia or blood sugar. Those are a couple of the things that the provider could be looking at.

Also, look for a blood gas analysis. Did they do a blood gas analysis? Hopefully, they did. And, again, with the hyper or hypoglycemia, what were their glucose levels? Then check for a liver function test, or a test for any toxic substances or drugs. Any abnormalities in any of these tests could indicate a metabolic disturbance and actually end up being the contributing factor to encephalopathy.

That's what we really want to get at: the etiology of this metabolic encephalopathy.

Imaging, again, can be limited, and maybe providers won't do it all the time, but they might do an MRI or they might do a CT scan just to rule out any structural abnormalities or to identify any potential causes of encephalopathy, like a possible stroke or brain edema.

They could do an electroencephalogram (EEG), that certainly can be valuable to evaluate brain function and detect any abnormal electrical activity that would be associated with an encephalopathy, even if the patient is sedated. It can certainly provide insights into the severity of the encephalopathy.

And then, obviously, look at the patient’s clinical response to treatment. If the patient's encephalopathy improves, like this one did, in response to targeted treatment, then that would be addressing the underlying metabolic abnormalities, like correcting their electrolyte imbalance or optimizing oxygenation and ventilation.

If the provider found that the patient had some type of infection and they treated the infection, that could certainly help them validate this. So, although it seems a little strange, it is not an impossibility that a patient on a vent could have metabolic encephalopathy. You just have to find the correct etiology.

Editor’s note: Sharme Brodie, RN, CCDS, CCDS-O, a CDI education specialist at ACDIS/HCPro, answered this question on the ACDIS Podcast. Contact her at sharme.brodie@hcpro.com.