I/NF CASE #11 - Hypokalemia

[sozme]

I/NF CASE #11
These are cases which require potassium repletion. I'm trying to create more cases that are relevant to the intern. There is not very good information out there on how to exactly replete potassium, especially on inpatients. Most books provides cursory rules or in-depth examination of differential, but very few give specific recommendations on what formulation to use and how much to give.
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Links to previous cases:
Case 1 Case 2 Case 3
Case 4 Case 5 Case 6
Case 7 Case 8 Case 9
Case 10
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#1: 39-year old female on observation for presumed viral gastroenteritis following a 4-day cruise with friends. Yesterday, she showed-up to the ED after several episodes of watery diarrhea and non-bloody, non-bilious vomiting. She was resuscitated with 2 L of NS and admitted to observation. Patient takes no medications, nor does she have any diagnosed medical conditions other than allergic rhinitis and exercise-induced asthma.

You, the intern, are called at 0528, because the patient's BMP shows a K+ of 3.1.

What is your immediate management?

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#2: 66-year old male with a history of essential hypertension sent to the emergency department from an urgent care facility owing to "extremely high blood pressure." Of note, patient visited urgent care to request refill of pain meds for chronic lower back pain. In the ED, patient's BP is 220/123 (about equal in both arms). He is not complaining of chest pain, SOB, dizziness, visual changes, or headache. He takes hydrochlorothiazide 25mg PO QD, amlodipine 2.5mg PO QD, hydrocodone/APAP 5/325 Q4H PRN. A BMP ordered in triage revealed a K+ of 3.0.

What is your immediate management?

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[Psai]

1) reeducate the nurse for calling about something so stupid at 5 in the morning then wait until right before their sign out before ordering 40 po, 40 iv and get the day nurse mad at them for signing out electrolyte repletion

2) when trop, ekg, lfts, etc. are negative, discharge pt from ed and reeducate urgent care pa about the misuse of resources in having someone with asymptomatic hypertensive being sent to the ed. tell them to go up on the damn blood pressure meds while working them up for things like conns in the outpatient setting

 

[673441]

Don't have time to look at all of them, but for case 1:

Severe hypokalemia should be max infusion K+ at 10 to 20 meq per U2D with careful monitoring

 

[cbrons]

10 Meq per .10 for K over 3.0. So 40 mEq?

20 mEq KlorCon with food BID.

Obviously only need 2 doses total and then BMP again tomorrow am.

I think that would be the correct order for #1. Please tell me of In wrong.

If stil on IVFs then you would replete 40 mEq total over 24 hr period. But max you can go is 10 mEq through peripheral line per hour. So if you do 1,000 mL of NS with 20 mEq KCL at 125cc/hr x2 that should be sufficient.

Please tell me if Im incorrect here.

Sent from my SM-N910P using SDN mobile

 

[GadRads]

1. Assuming her creatinine is normal and can tolerate PO, she can take 2 oral doses of 40 meq KCl q4h apart. Else IV 10 meq/hr over 4 hrs. Recheck BMP.

2. assuming hypertensive emergency is ruled out (trops, EKG, chest xray, CMP and no neuro symptoms), I would give 100-200 mg of labetalol, short-term script for trandate, and 40 meq of KCl PO q4h apart. Outpatient workup for uncontrolled HTN.

 

[cbrons]

short-term script for trandate

Why?

And how are you getting the K+ dose based on that number? (genuinely curious).

 

[alpinism]

Don't forget to give Mg with that K if needed.

(except for a few rare exceptions)

 

[GadRads]

Why?

And how are you getting the K+ dose based on that number? (genuinely curious).

With a BP that high and since he might have a 2+wk period before he sees a PCP, a short-term prescription is reasonable. 25 mg of HCTZ and that baby dose of amlodipine may not be adequate for BP control at home. Labetalol is a good BP med for HTNsive urgency. I try to avoid clonidine unless it's necessary, but some people give it without blinking.

10 meq of K will increase serum K by 0.1 meq/L, assuming creatinine/kidney function is normal. Rough calculation is 100*(Target K - current K)/current creatinine. So giving the same dose of K to an end-stage renal disease patient is likely to cause hyperkalemia.

 

[mehc012]

Any thoughts on eventually switching the second guy to a potassium sparing diuretic if he's dropping his K that low? I know this said 'immediate management' but I'm just curious whether that's in the playbook at all.

 

[Tenk]

I would have discharged both of these patients. Prolly would have looked for a AAA on the ol vasculopath with back pain first though unless he currently doesn't have pain. Then D.C.

 

[cbrons]

I guess I'm curious if anyone can comment on the K+ replacement dosing.

 

[Radetzky]

Would have told the first girl to eat some bananas. If her gastro is getting better she will eat her own way to normokalemia. Despite the numbers not looking the way we want them a k 3 or above will not cause any harm to people not on digoxin or amiodarone. If she needs further IVF then chuck 40mmol in a litre bag.

Would put the second guy on slow release potassium 1.2g bd (which provides 32mmol a day) to combat his likely thiazide induced hypokalemia and send him home with increased dose of amlodipine. If he was hypokalemic prior to starting thiazides then worth ruling out Conns.

 

[sozme]

Thanks for replies.

Any one have methods for oral K+ dosing in situations like these?

 

[Tenk]

Just give them 20-40 meq a day for a few days and fix whatever is causing it: i.e. Vomiting and diarrhea. Assuming good kidney function your body is REALLY good at getting rid of excess potassium. Otherwise we would all be dead.

 

[boshtrich]

#2 sounds like they'd also warrant investigation for hyperaldosteronism, but like others have said this could be done as outpatient. Probably still reasonable to stop HCTZ send out on some spironolactone.

 

[Raryn]

#2 sounds like they'd also warrant investigation for hyperaldosteronism, but like others have said this could be done as outpatient. Probably still reasonable to stop HCTZ send out on some spironolactone.

If you want to work them up for primary hyperaldo (a reasonable thought), don't start them on spironolactone before you complete your workup. It will screw up your labs for the next 4-6 weeks.

Reasoning to test for primary hyperaldo is this: While HCTZ can be contributing to the low K, there's millions of people on thiazides who don't get hypokalemia... so diuretic induced hypokalemia in the setting of significant HTN points you to possibly some other underlying issue. What you'd do with this guy is rule out any huge acute issue with a careful history and phyisical (+/- EKG), uptitrate his amlodipine, and send him home to his PCP. Stopping the HCTZ is not unreasonable, but you'd have to start a different agent in lieu of it, so it might be easier to give him some PO potassium in the meantime (since you're the ER doctor and not going to follow this guy up). As an outpatient, the PCP should get a renin/aldosterone ratio as an initial screening test for hyperaldosteronism, assuming the patient is K replete by that point. The rest of the workup will depend on what that initial test shows.

What you shouldn't do btw is work this guy up for all causes of resistant hypertension, as he doesn't actually meet criteria for it. For resistant hypertension you must be on adequate doses of three agents, including a diuretic. He's on a diuretic and barely on a second agent (the lowest possible dose of amlodipine), so he doesn't count.