Electrolyte Management
Jeff Beamish
PGY-3
Intern Bootcamp Lecture Series
August 2013
Summary
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Hyperkalemia
Hyponatremia
Hypernatremia
Hypokalemia
Others: Mg, Phos, Ca (briefly only)
Cases
Disclaimer: this is “boot camp”. I have tried to include the most common issues and
management approaches but this lecture was in no way meant to be complete.
Hyperkalemia
• Life threatening!
Hyperkalemia
My approach:
1) Is it real?
-hemolysis, need to be rechecked?
-if there is any uncertainty, get an EKG.
2) How aggressive to do I need to be?
-Magnitude: K > 6.0
-Rate of change: K yesterday was 3.5 now is 5.5
-EKG findings: peaked T’s, QRS widening
Hyperkalemia
Hyperkalemia
3) Appropriate treatment
-Ca Gluconate, 1g over 2-3 min
-immediate onset
-repeat until EKG normalizes
-lasts 30-60 min
-D50 1-2 amps + 10U IV insulin:
-takes 10-30 min to work
-lasts 30-60 min
-Lasix (if appropriate)
-Kayexalate: 15-30 g q6
-slow onset, requires multiple doses to be effective
-in 1 day can reduce K by about 1 mEq/dL
-DO NOT USE is post operative patients or if SBO suspected
-Dialysis
4) Prevent recurrence, figure out etiology:
-Renal failure (acute or resulting from missed RRT)
-Medications: ACEi, ARB, K sparing diuretics; digoxin; beta-blockers
-Acidosis (remember total body K may be depleted)
-Tissue damage
-etc…
Hyponatremia:
1) Do first? or think first?
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Siezures, altered mental status?  MICU
Otherwise, think…
2) Is it real? Glucose? Other osmotic agents?
Lipids? Sorbitol Bladder irrigation? (i.e. what is
the likely serum osmolality?)
3) What is the body’s volume status?
a) Think: Hypovolemia? CHF? Cirrhosis?
Nephrotic syndrome? Other reason why the
body might think it is dry?
b) check urine osmolarity…
Hyponatremia:
4) Fix the problem:
• if hypervolemic:
– suggested by hypervolemia on exam and/or high urine osmolarity
– optimize fluid status (CHF, Cirrhosis, Nephrotic syndrome)
• if euvolemic:
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Determine etiology:
Elevated ADH: SIADH, hypothyroid, adrenal insufficiency
Low ADH: beer potomania, polydipsia, tea & toast
Medications: HCTZ
– Fluid/free water restriction often first line
– SIADH note: remember that if the urine osm > than IVF osms, you will
make the hyponatremia worse with fluid
Hyponatremia:
5) Follow up your management:
• Goal correction ~0.5 mEq/L/h
• That’s no more than 10-12 mEq/L change per
day
• Ideally aim for an even slower correction < 9
meq/L per day
• Complications most common with very low
sodium (< 115) for a long time with rapid
correction (>10-12 mEq per day)
Hypernatremia:
1) Does this person need ICU? Significant AMS?
Seizures?
2) Etiology:
• Most commonly hypernatremia for impaired access to
free water with ongoing water loss:
• Example: Elderly pt with on help at home in a hot apartment
with diarrhea
• Example: Intubated/sedated on tube feeds at an OSH…
• Less commonly from diabetes insipidus
• Example: psych patient on lithium
• Example: post 40 min cardiac arrest in ICU rewarming
• Less commonly from osmotic diuresis:
• HHS
Workup: check u/a (SG is poor man’s osmolarity) and
urine osms.
Hypernatremia:
3) Treat:
– If possible, give oral free water
– Remove offending agents, if possible
– If this fails:
Hypernatremia:
3) Treat:
– If possible, give oral free water
– Remove offending agents, if possible
– If this fails:
• Calculate the free water deficit
• Determine the time needed to correct at 0.5 mEq/L/h
• Divide free water deficit by time to estimate D5W infusion
rate
Hypernatremia:
3) Treat:
– If possible, give oral free water
– Remove offending agents, if possible
– If this fails:
• The traditional approach involves a simple mass balance on
the body and assume essentially no excretion of water or
sodium—assumptions that are clearly violated in real life
• Does provide a reasonable estimate for starting point:
I’ll do some of the calculations for you:
All have a Na of 155 and your goal is 145:
50 kg 85 yo woman: 75 cc/h
70 kg 45 yo man: 145 cc/h
120 kg 70 yo man: 211 cc/h
Hypernatremia:
3) Treat:
– If possible, give oral free water
– Remove offending agents, if possible
– If this fails:
• Much more important: Pick a reasonable starting rate and
CHECK YOUR PROGRESS!
• Little old lady: 50-75 cc/h
• Normal sized guy: 100-125 cc/h
• Big guy: 125-175 cc/h
Repeat labs every 4-8 h depending on severity. Goal
correction LESS THAN 0.5 mEq/h.
Pts with DI will need more aggressive volume to meet ongoing
losses
Hypokalemia
My approach:
1) What is the degree of change? (<3
requires immediate attention)
2) What is the Cr? Mg?
3) Is there an etiology for hypoK (that needs
to also be corrected if possible)?
1) GI losses: Vomiting, diarrhea, NG suction
2) Renal losses: diuretics, hyperaldosterone
3) Shifts: acidosis, insulin, adrenergic activity
Hypokalemia
My approach:
4) Replete magnesium
(goal > 2 for cardiac patients, 1.5-2 for noncardiac patients—will discuss this in a bit)
5) Replete potassium
Normal patient: 10 mEq K increases K by 0.1 mEq/L
Maximum K every 4 h is 80 mEq (40 IV, 40 PO)
Hypokalemia
My approach: (normal renal function, Mg replete)
K = 2.8
DANGER
2
Rx: 40 mEq IV now
40 mEq PO q4h x 2
SUBOPTIMAL
3
IV K
PO K
PO K
40 mEq 40 mEq 40 mEq
GOAL
4
Hypokalemia
My approach: (normal renal function, Mg replete)
K = 3.2
DANGER
2
Rx: 40 mEq IV now
40 mEq PO x 1
--OR-40 mEq PO q4h x 2
SUBOPTIMAL
GOAL
4
3
IV K
PO K
40 mEq 40 mEq
Hypokalemia
Other considerations:
1) GFR < 30-40, avoid IV K if possible, give
smaller doses, (~50% doses)
2) ESRD, be very cautious (especially if just
dialyzed)
1) Supplement only to get out danger zone
2) Use PO K if at all possible
3) Very cautious with IV K, recheck labs frequently
3) Account for ongoing losses
1) Ongoing diarrhea, NG suction
2) Ongoing diuresis (be mindful of overdiuresis can
lead to AKI and hyper K)
Hypokalemia
Special cases:
ESRD, just dialyzed last night, AM labs
K = 2.8
DANGER
2
Rx: 20-40 mEq PO
discuss higher K bath with renal fellow
recheck renal panel 6-12 h
SUBOPTIMAL
3
PO K
40 mEq
GOAL
4
Hypokalemia
Special cases:
55 yo woman with HF exacerbation on lasix gtt 10 mEq/h, normal renal function
K = 3.0
DANGER
2
Rx: 40 mEq IV, 40 mEq PO q4h x 2
recheck renal panel q12 h, monitor for AKI
consider standing K order
SUBOPTIMAL
3
GOAL
4
PO
IV KK
PO K
PO K
40 mEq 40 mEq 40 mEq
Hypokalemia
Special cases:
Baseline GFR 30 and stable renal function
K = 2.8
DANGER
2
Rx: 40 mEq IV, 40 mEq PO q4h x 1
SUBOPTIMAL
3
IV K
PO K
40 mEq 40 mEq
GOAL
4
Hypokalemia
CHECK YOUR WORK!!
1. Anyone who needs IV K also needs a f/u
renal panel at most 12 h later
2. Everyone is different, adjust repletion
based on individual responses
Others…
Hypomagnesemia
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Very common
You don’t know it’s not there if you
don’t look (I usually check a magnesium
level on all pt’s I admit at time of
admission)
Cardiac patients: Mg > 2 mg/dL
Toxicity: Mg > 4.8 mg/dl
Hypomagnesemia
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Repletion:
Slow…
Dangerous peak
Renal excretion threshold
Mg
Wasted Mg
t
Infusion time
Mg
t
Infusion time
Hypomagnesemia
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Repletion: normal renal function, goal 2
Very rough guidelines:
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1.8-2.0  1 g Mg sulfate / 1h
1.2-1.7  2 g Mg sulfate / 2h
< 1.2  4 g Mg sulfate or more over 4h or more
If repletion inadequate the next day, try longer
infusion time (4g over 12-18 h)
Dose with caution in renal failure, GFR < 30,
reduce dose by at least 50%
Oral: magnesium oxide 200-400 mg BID-TID
(causes diarrhea)
Hypophosphatemia
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Malnutrion, re-feeding syndrome
Normal 2.5-4.9
Repletion can be given as sodium or potassium salt
IV repletion indicated if Phos < 1.5
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Choose K-phos (contains 1.5 mmol K for each mol phos) or Na-Phos
2.0-2.5  15 mmol (22 mEq K)
1.0-1.9  21 mmol (31 mEq K)
< 1.0  30 mmol (45 mEq K)
Often there are shortages: can substitute PO phos, often given
every 6 h for a day, then recheck
Potassium acid phos tabs have about 4 mEq K / 500 mg
Must be infused slowly, cannot be infused with calcium
Caution with renal failure.
Hypocalcemia
1)
2)
3)
4)
Correct for albumin (add 0.8 for each g/dL < 4)
Check ionized Ca (need to draw a new sample)
Check RFP, Mg, PTH, 25-OH vit D with iCa
If IV repletion needed (iCa < 1)
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5)
6)
0.85-1  2 g Ca Gluconate over 2h
< 0.85  3 g Ca Gluconate over 3h
Consider etiology
Correct underlying problem
Again: caution in renal disease (esp with elevated Phos!)
Hypercalcemia
1) Correct for albumin (add 0.8 for each g/dL < 4)
(it’s probably worse than you think!)
2) Is acute treatment needed (Ca > 12):
1) IV hydration 200-300 cc/h initially then adjust to
maintain UOP ~ 100-150 cc/h
2) Lasix AS NEEDED ONLY to maintain euvolemia
3) For Ca > 14: Calcitonin 4 U/kg SQ q6-12h
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4)
Check Ca after 4-6 h and if responding, can continue
Rapid tachyphylaxis develops
Zolendronate 4 mg IV over 15 min
3) Think about etiology and workup…
Cases:
68 yo man evaluated for jaw pain and difficulty eating found
to have. CT neck shows LUL spiculated lung lesion:
Na = 126
Cl = 87
Cr = 0.71
Ca = 11.2
Alb = 2.7
Now what?
Cases:
75 yo man admitted to OSH ICU for hepatic
encephalopathy. Admission labs notable for elevated
ammonia but otherwise unremarkable. He had been in
their MICU for 3 d transferred to the floor at the OSH
yesterday and now to you on the VA wards. He
remains disoriented and minimally responsive on
exam.
Na = 159
K = 4.2
Cr = 1.2
Now what?
Cases:
56 yo man admitted to ICU after tylenol OD
who subsequently develops liver and
renal failure, but now transferred to the
floor and getting intermittant HD only.
Last HD was yesterday.
K = 6.0
Now what?
Cases:
57 yo man admitted to the VA for Na 121 on
routine labs at a CBOC. It took him all
day to get to the hospital. You notice he
is a little shaky when you meet him.
Now what?
Cases:
55 yo woman with PMH of extensive CAD
s/p recent TAH-SAO for large ovarian
mass is admitted to CICU POD # 8 for
n/v and CP with transient lateral ST
depressions
K = 2.8
Now what?
Cases:
27 yo woman with h/o of medication nonadherance and DM1 is admitted to UH MICU
with DKA.
K = 5.8
CO2 = 8, AG 20
BG 423 on arrival
What should we do about the K?
Cases:
85 yo woman with h/o diastolic HF transferred to
Hellerstein service for placement after aggressive
diuresis in the CICU. Continues to look wet, but Cr
has been rising over the last 3 days from 1.03.0.
She is on a lasix gtt at 10 mg/h. 2 days ago her K was
3.0 and now she is getting standing 40 mEq K each
evening while on the gtt.
K = 5.2 at 4 AM (not hemolyzed)
What should we do about the K?