I had a patient with severe ARDS who had been anuric for 24 hours. She was in a respiratory acidosis, with a PaCO2 of 75 and a bicarb of 18. Her pH was 7.20.
The fellow ordered CRRT, but the next day the attending d/c it saying that the pt didn't need CRRT because this was a respiratory acidosis.
This didn't make sense to me. First of all, even though the pt's electrolytes were stable, shouldn't anurea itself be an indication for immediately starting dialysis? (She was hypotensive, so she needed CRRT). Also, the bicarb wasn't compensating for the respiratory acidosis. I agreed with the fellow's reasoning which was that by starting dialysis to compensate for the respiratory acidosis we could use lower lung volumes, which would benefit the pt's ARDS. All that made sense to me, but the attending disagreed. I didn't hear his reasoning, but what do you guys think?
Ok, got it. Thanks for all the responses. I realize now that the dialysis could not have made a significant impact on reducing the respiratory acidosis. Makes sense.
At one point after she was intubated, I had a chance to bag her for a little while. Wow, I never realized just how poor the compliance is on a ARDS patient. I thought you could only have such poor compliance with an obstruction or a pneumo. That made me really understand just how damaged these patients are!
I mean it all depends on the severity of the condition. Pulmonary edema, pneumothorax, pneumonia, ARDS can all cause serious problems with lung compliance. I'd say the worst case of noncompliant lung I've seen was a severe ARDS case. ARDS is like the lungs turning into concrete so imagine trying to ventilate that!
Obstructions bring more of a problem with airway resistance, where you can't ventilate properly because the airway is obstructed with secretions, mucus plug, ET tube tip occluded or you are dealing with bronchospasm. In these situations you would be able to ventilate properly if the obstruction was removed, but the lung itself is compliant.
Sounds like she could benefit from being proned. What is the patients Tv and RR on the vent? Which mode is the patient on? A/C, SIMV, PC? How far into this process is she? The kidneys are not going to compensate quickly but they should some. If she's septic did she get fluid resuscitation?
I am surprised by how many are suggesting bicarb administration. I thought we had moved away from that for a large part.
Just wondering, how long have you been a nurse? You sound so knowledgeable and I can't ever imagine knowing how everything works as well as you lol. Just wanted to say I loved reading your reply!
Give bicarb when the patient has been resuscitated adequately with fluids/products, Ca is ok, and they are refractory to pressors and actively trying to die. The drips are the worst. You're essentially just injecting them with co2. You'll need a higher minute ventilation to blow off the resultant increase in co2 after an administration of bicarb. Which, in a person with ARDS your vent settings might not allow much of an increase at all. You'll just get a paradoxical increase in acidemia.
Give it as a last resort to buy a few minutes in a death spiral, otherwise, it's working against you. It still amazes me to see (bad, usually the older ones) intensivists that think any acidemia as something inherently bad that must be corrected, but won't bat an eye with an alkalotic patient, when that is potentially more dangerous from an oxygen off-loading perspective.
As for the NAG acidosis you still need to correct the underlying cause of the acidosis, not correct it for 5 minutes with bicarb. RTA, diarrhea, etc.
A very wise intensivist once told me that "healthy kidneys are smart kidneys" they know when to hold on to water. Your patient being hypotensive and in ARDS/septic and GI bleed was most likely hypovolemic and your "healthy kidneys" as indicated from the normal labs were doing what they could to help.
Yeah I would have liked to see the vent settings on this patient. With a pco2 of 75 and a bicarb of 18, it seems like a quick fix - just up your rate. I've had patients on rates of in the 30's when on AC/PC. Curious of the pa02 as well. Now, if this patient already had a rate in the 30's, then like one of the posters above - you might be looking at paralyzing this patient, iNO, going prone, or screw it just take the lungs out of the mix and just put some VV-ECMO in (which I've seen wayy more lately over the past 12 months!).
About the dialysis - yeah, like someone already mentioned, just because someone isn't voiding, doesn't mean they need dialysis. Normal cr? That's odd, calm before the storm? What's their K? Get those MAPs up, give them some fluid---Bumex maybe? Bladder scan?
Thats what we call a combined acidosis. The RT needs to fix those vent settings fast. And the docs need to get on that renal issue too. CRRT would help but we can blow that CO2 off to bring that pH up to make it suitable for life.
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Needed volume?