Have you heard of hepatorenal syndrome (HRS) but don’t really understand it? At it’s core, HRS is renal dysfunction as a result of liver disease. It’s common in patients with end-stage liver disease (ESLD) and among patients undergoing liver transplant. The good news for the kidney is, its not really a kidney problem. It’s a liver problem. So, fixing the liver is the fix for the kidneys. DocSchmidt has a really good Instragram post covering the pathophysiology, diagnosis, and treatment of HRS. All in < 2 mins!
Category: Renal/Metabolic
Bicarb in Metabolic Acidosis
The Resuscitationist has a great Instagram post about sodium bicarb in cardiac arrest, does it help or hurt? I’d expand this to just about any metabolic acidosis. IVP sodium bicarb used to be commonly given in these stations, especially during a cardiac arrest. It makes sense intuitively. Metabolic acidosis causes all sorts of cardiovascular problems including increased arrhythmias and poor contractility. Additionally, most vasopressors (vasopressin being the notable exception) won’t work in severe acidosis. So that just worsens things as the patient gets more hypotensive and you go up and up on the pressors to no effect.
So, it stands to reason that giving some bicarb would correct the acidosis (pH and HCO3 are inversely related in metabolic processes, after all) and fix all of our problems. So, why would you not want to give a couple of amps of bicarb?
Firstly, there isn’t any real evidence that it helps. Two studies mentioned in the IG post are pretty conflicting with one showing bicarbonate administration during cardiac arrest associated with earlier ROSC, but the other showing worse neurological outcomes. It may be beneficial in certain populations, including patients with severe metabolic acidosis and stage 2 or 3 AKI, some poisonings/overdoses (i.e. sodium channel blockers, TCA, salicylates, some toxic alcohols), and hyperkalemia (although a recent study question that as well).
So, there’s no real evidence it helps, but what’s the harm in trying? Well, firstly, I would argue that there’s always risk in medicine and so we shouldn’t be doing stuff “just because” if there is no evidence that it helps. But in the case of bicarb, it can actually hurt. Sodium bicarbonate (NaHCO3) gets metabolized and one of the byproducts is CO2. In a lot of cases, this isn’t really a big deal, but if your patient already has a respiratory acidosis (or is at risk for one), this is a really bad idea. It can also drop the ionized calcium, which again would be pretty bad in a critically ill patient.
So, no real evidence of benefit outside of certain situations. Possible harm. The better thing to do in most cases is to treat the cause of the metabolic acidosis. Having said that, I will sometimes give bicarb in a severe metabolic acidosis (pH < 7.2) in an unstable patient in order to buy some time. But, I’m cautious about it.
Lactic Acidosis
Every student learns the mnemonic “MUDPILES” for the diagnosis of anion gap metabolic acidosis (AGMA), but I think the one on that list that is the most misunderstood is lactic acidosis. In and of itself, “lactic acidosis” is more of a problem than a diagnosis. I’ve never yet had a patient who had spontaneous hyperlactatemia, yet we often want to just says that the patient has “lactic acidosis” and leave it at that.
When approaching the patient with an AGMA, if there is an elevated lactate, we can’t just jump to the conclusion that “lactic acidosis” is the cause, and even if it is, we need to dig in to determine WHY the lactate is elevated. and it turns out, that’s a complex question. There are a number of things than can cause an elevated serum lactate, it’s not just tissue ischemia, and despite the idea of “trending lactates” in sepsis, elevated lactate doesn’t always = sepsis.
Obiajulu Anozie (@icuexplained) has a great post over on Instagram that goes over the basics of classifying and further diagnosing a lactic acidosis. Once the cause has been identified, then you can get to work treating the cause, rather than just bolusing IVF until the “lactate clears.”
IV Bicarb: Is There Any Value?
IV Bicarbonate used to be all the rage in critical care. It was included in the ACLS algorithms. It was used, in drips or in pushes, to treat all kinds of problems. I’ll admit, there are still times that I use it when the indication is…shaky, often when my back is against the wall and I need something to buy some time. But, is there any real use for it in ICU practice? In a recent episode of The Elective Rotation, Pharmacy Joe recently took a look at when IV bicarb should be avoided (often) and when it is helpful (a lot less often).
Often, IV bicarb is used as a band-aid. This is ok to a point. If it helps buy you some time, ok. But using it without addressing the underlying issues (like I remember doing a lot in the old days) is fraught with problems. There are a handful of scenarios where we should avoid using bicarb because it’s been shown to be of no value. ACLS has removed it from the algorithms and generally avoids against its use in cardiac arrest, for example. But there are some specific times when it is helpful and should be considered.
CT Abdomen and Pelvis Anatomy
I love a good visual guide to anatomy. As someone who looks at more than a few CTs of the belly, this is super helpful in making sense of what I’m seeing. Also, as someone who does a fair amount of POCUS exams of the abdomen, it’s also super helpful.
The Rule of 15
I tweeted about this yesterday but wanted to do a whole post on it, because I think it’s a great tip! ABGs and acid-base disturbances are difficult topics to grasp. There are lots of great ways to remember how to interpret these, and we’ll cover them in time. But one of the hardest parts, especially for learners, seems to be the concept of proper compensation. How do I know if this primary problem is all that’s going on or if there is more? With anion gap metabolic acidoses, we teach students to use Winter’s Formula to calculate the expected pCO2 and thereby determine if you’re dealing with a purely metabolic problem, or if there is a concomitant respiratory derangement as well.
Of course, you can always use your handy ABG analyzer app (ABG Eval is my personal favorite), but what if you just want to know quickly? You can use the Rule of 15. Dr Jeremy Faust (@jeremyfaust on Twitter) mentioned this in a thread I was reading yesterday and it sparked my interest. I retweeted his tweet, but wanted to know more. I found a very quick video that he does along with Dr Corey Slovis on Academic Life in Emergency Medicine (ALiEM, another great resource for critical care education!). Basically, take the bicarb and add 15. That should give you roughly the expected pCO2 and if you throw a “7.” in front of it, roughly the expected pH. Watch the video here for more!
Are Diuretics Safe in Critically Ill Patients?
One of the more important (and overlooked) aspects of critical care is the concept of de-resuscitation. We give lots of fluid to patients in the throws of shock of all kinds, but even though that fluid resuscitation may be life saving at the time, it can lead to lots of complications later on. So, we need to de-resuscitate these patients and often the best way to do that is with diuresis. But, are diuretics safe to give in the critically ill? In this episode of the Elective Rotation podcast, Pharmacy Joe discusses the safety and efficacy of diuresis in the ICU. Listen here.
critical care notes 