47-year-old woman found stuporous and hypotensive. She has known alcohol abuse and decreased LVEF around 30%.
Her labs come back, and you should provide plausible reconstructions of these results.
| 110 | 59 | 38 | 73 |
| 3.2 | 30 | 2.2 | 8.0 |
Arterial Blood Gas on 2L nasal oxygen
| pH | 7.57 |
| pCO2 | 31 |
| pO2 | 99 |
| c HCO3 | 29 |
What do you think her acid-base diagnosis is? What additional information do you want (history, physical and/or labs)?
{ 5 comments… read them below or add one }
Well obviously the most important thing is she is hyponatremic (assuming no tricks like hyperlipidemia) -that is your immediate priority. If the history suggests this happened over a short period of time, she is prone to immediate neurologic complications -you must stop the progression (and reverse slowly).
We need her vitals but it is likely she is volume depleted -she is not, repeat not, dehydrated (don't need any more info to tell that).
If she has edema- she is not total volume contracted but simply intravascularly water depleted so she still needs saline, just a little slower. Eventually she will need sodium restriction in that case but not now.
The acid-base disturbance is a combined respiratory and metabolic alkalosis.
Given what we have here- she is likely either on diuretics or vomiting or both. (Other meds could be responsible for the hyponatremia -but this is the most likely clinical scenario with what we have been provided)
She is mildly hypoxemic – so we need her chest X-ray.
She immediately needs normal saline (but not too fast -serum sodium should not exceed 125 in first 24 hours – risk of CPM) and potassium, probably lots -but not too fast, assuming she is putting out urine.
She needs an echo and a possible work-up for a gastric outlet obstruction if she has a history of vomiting or suspicious GI complaints. Stop extraneous meds until needed.
Your biggest problem is whether she has left sided heart failure – (if the hypoxemia is infection and not LVF – she needs antibiotics). This will also limit the rate at which you can give saline.
However, since she is intravascularly water depleted and probably intravascularly volume contracted (even with peripheral) edema -if the saline is given cautiously, it should not be a problem. If it is, then the saline should be given in the ICU with an inotrope (dobutamine) or an inotrope/pressor (dopamine) if she is hypotensive.
I misspoke on the "intravascularly water depleted". She is intravascularly water overloaded, why she is not dehydrated, and if hypotensive quite likely intravascularly sodium depleted.
triple acid base disturbance – respiratory alkalosis, metabolic alkalosis, anion gap elevated metabolic acidosis. also has significant Aa gradient and severe hyponatremia.
first thought is that maybe she is on too much diuretic causing renal failure, hypokalemia and metabolic alkalosis. vomiting could produce the same array of metabolic disturbance.
with respect to the hyponatremia, i wonder if she is on a thiazide like metolazone on top of lasix. this could be a major contributor to the hyponatremia. only if she is not on diuretics, would i want to check the serum electrolytes and osmolality to futher investigate – other possibilities could include appropriate excess ADH secretion due to CHF, or beer potomania. previous lytes and Cr values would be helpful too.
respiratory alkalosis and high Aa gradient point to something wrong in the lungs ?CHF or aspiration pneumonia? check the CXR.
high anion gap likely lactate due to hypotension/tissue hypoperfusion or perhaps lactate from seizure due to hyponatremia and alcohol withdrawal. but would check serum ketones and serum osmol too to investigate other possibilites (starvation or alcoholic ketoacidosis, occult ingestion ).
I would want to know her meds list and her physical exam findings (neck veins, vital signs, presence of edema/ascites) to know if her hypotension is from simple volume depletion which would be easier to fix vs cardiogenic shock which would not be so easy to fix. is there sign of fever or sepsis otherwise that may have destabilized this lady? has she had vomiting or diarrhea recently?
my best guess is that she's on a lot of diuretics and maybe and ACE and had an intercurrent illness like gastroenteritis or vomiting from alcoholic gastritis that led to the volume depletion and severe metabolic disturbance.
the low BP and severe metabolic disturbance (particularly serum Na of 110) would be enough to explain her drowsiness, but would check a tox screen, ethanol level and CT head for subdural bleed (any obvious focal neuro sign on exam or seizure?)
The hyponatraemia with the history of alcohol abuse and poor LVEF is suggestive of reduced effective volume (effective volume not intravascular volume- the difference is important). Potentially also on diuretics as noted above. Could be causing
As noted above, this is a mixed metabolic and respiratory alkalosis with a widened anion gap. As respiratory disorders take a shorter time to develop, I'm guessing this started as a primary metabolic alkalosis and that something happened respiratory-wise to cause an "inappropriate" compensation.
Common causes of metabolic alkalosis would include vomiting (thus the marked hypochloraemia?), diuretic use (such as a loop diuretic for heart failure). Hypokalaemia could be contributing to this issue. Perhaps this patient is also taking antacids. Hyperaldosteronism would be unlikely given the profound hyponatraemia.
The hypoxaemia in conjunction with with the hypocarbia (and likely primary metabolic alkalosis) is a real worry. I suspect that this patient has a type 1 respiratory failure; is it acute pulmonary oedema, infection, hepato-pulmonary syndrome, aspiration?
Now, I apologise because I'm not very good at understanding or interpreting imperial units for lab tests as I'm from Australia… but it looks like she has renal impairment (?acute) which fits with the low effective volume and possible vomiting/diuretic use. I don't know what the two other values next to the urea and creatinine are?!
In conclusion, here are my differentials:
1) aspiration after profuse vomiting from alcoholic gastritis (+/- antacid or diuretic use)
2) acutely decompensated left heart failure causing APO (+/- in the setting of sepsis)
3) acute liver failure and encephalopathy causing her to be obtunded, volume contracted, vasodilated, hyponatraemic
4) combination of the above.
5) intra-abdominal sepsis or acute pancreatitis
Now, obviously the most important things I'd want to know are:
A/ conscious state and airway
B/ how do her lungs sound?
C/ what are her heart rate, blood pressure. Does she have any murmurs? Does she look overall volume overloaded or volume contracted?
D/ more details about her conscious state
Is there any collateral history? Can the patient give us some history? Was she unwell prior to this? Did she have any shortness of breath, vomiting, fevers, diarrhoea, oedema? Any recent change in medications?
As well as assessing fluid state and cardiorespiratory systems I'd like to examine specifically for signs of liver disease, ascites. I'd like to examine the abdomen to check for organomegaly or peritonism, and perform a rectal examination looking for GI bleeding.
I'd want to assess her neurological status and make sure there is no focal neurology, signs of meningism or raised intracranial pressure or (signs of subdural haemorrage).
This lady should have adequate fluid resuscitation with normal saline (first priority being ensuring she is not critically hypotensive, then being careful not to correct the serum sodium too quickly), a central venous catheter and in-dwelling catheter for ongoing fluid management. If she is severely hypotensive she should also have an arterial line. She should definitely have a chest x-ray earlier rather than later to guide our diagnosis. She needs an FBC, liver function testing, coagulation profile, calcium/mag/phos and ECG. And an ICU consult.
With the elevated anion gap I should have added blood alcohol & ethylene glycol, sorry, and consideration of salicylate levels