1. Management of Hypokalemia in the Hospital
Hospitalist Best Practices
December 16, 2010
J Rush Pierce Jr, MD, MPH
Section of Hospital Medicine, Univ of New Mexico

2. Hospital treatment of hypokalemia
Agenda
Review (briefly) physiology of potassium homeostasis and clinical disturbances thereof
Review (briefly) common causes of hypokalemia, emphasizing those of importance to inpatient care
Discuss management of hypokalemia in the hospital
Derive some specific clinical care issues
12/17/2010
Hospital treatment of hypokalemia

3. Hospital treatment of hypokalemia
Management issues
When should hypokalemia be corrected?
What is the preferred agent for correction of hypokalemia?
What is the preferred route of administration to correct hypokalemia?
12/17/2010
Hospital treatment of hypokalemia

4. Cases – select a response
20 y/o vomiting, K = 2.9
30 y/o asthmatic K = 2.9
40 y/o with DT’s, K = 2.9
50 y/o with CHF, K = 2.9
60 y/o old with Child’s C cirrhosis, K = 2.9
No treatment w/KCl
Oral KCl to get K ≥ 3.5
Oral KCl to get K ≥ 4.0
IV KCl to get K ≥ 3.5
IV KCl to get K ≥ 4.0
12/17/2010
Hospital treatment of hypokalemia

5. Potassium homeostasis –general principles and teaching points
Potassium is mainly an intracellular cation
Serum potassium is surrogate marker for total body potassium
With marked production of cells, may see hypokalemia
Treatment of vitamin B12 def
With neupogen
Potassium is major determinant of membrane potential
12/17/2010
Hospital treatment of hypokalemia

6. Potassium homeostasis –general principles and teaching points
Cellular shifts of K influenced by hydrogen
Alkalosis cause intracellular shift and may cause hypokalemia on this basis alone
Magnitude of effect is ~0.4 mEq decrease K for each 0.1 increase in pH (pH 7.4 ->7.6 = K 3.5 -> 2.7)
Very often clinical conditions causing alkalosis promote renal excretion of potassium
Cellular shifts of K influenced also by beta-agonists, insulin, and thyroxin
12/17/2010
Hospital treatment of hypokalemia

7. Potassium homeostasis –general principles and teaching points
Dietary intake of potassium almost always exceeds obligate potassium losses in urine, stool, and sweat
Usual dietary intake of K = 40 – 120 mEq/d
Very difficult to become hypokalemia due to decreased dietary intake (exc = 800 cal protein diets)
Obligate renal and GI loss = 5 – 25 mEq/d
12/17/2010
Hospital treatment of hypokalemia

8. Potassium homeostasis –general principles and teaching points
12/17/2010
Hospital treatment of hypokalemia

9. Non-renal causes of hypokalemia
Poor intake
Shift (hypokalemic periodic paralysis, alkalosis, insulin, beta-adrenergics, hyperthyroidism)
Excess extrarenal loss
Sweat
Dialysis, plasmpheresis
Vomiting (5 – 10 mEq/l)
Diarrhea (20 – 50 mEq/l)
12/17/2010
Hospital treatment of hypokalemia

10. Renal causes of hypokalemia
Diseases of kidney
RTA, salt-wasting nephropathies (incl Bartter’s)
Delivery of non-reabsorbable anions (ketoacids, bicarb, toluene, PCN)
Excess mineralocorticoid
Hypomagnesemia
Drugs
diuretics, Amphotericin B, platinum
12/17/2010
Hospital treatment of hypokalemia

11. Management of hypokalemia in the hospital
When to treat
What agent to use
What route of administration
12/17/2010
Hospital treatment of hypokalemia

12. Adverse effects of hypokalemia
Hepatic encephalopathy <3.5 [case reports]
Cardiac arrhythmias (acute MI < 4.0, cardiac surgery < 3.7; CHF; in normal, rarely unless <3.0; Class I anesthesia <2.6) [epidemiologic data]
Rhabdomyolisis < 2.5 [case reports]
Diaphragmatic muscle paralysis <2.0 [case reports]
More likely with rapid decline of K
Arrhythmias more likely with CHF, IHD, digoxin
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Hospital treatment of hypokalemia

13. Risk of hypokalemia in acute MI
Am J Kidney Dis 45:
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Hospital treatment of hypokalemia

14. Risk of hypokalemia in acute MI
J Am Coll Cardiol 2004; 43:155–61
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Hospital treatment of hypokalemia

15. Risk of hypokalemia in cardiac surgery
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Hospital treatment of hypokalemia

16. Risk of hypokalemia in cardiac surgery
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Hospital treatment of hypokalemia

17. Risk of hypokalemia in LV Failure
J Am Coll Cardiol 2004; 43:155–61
12/17/2010
Hospital treatment of hypokalemia

18. Risk of hypokalemia in HTN
J Am Coll Cardiol 2004; 43:155–61
12/17/2010
Hospital treatment of hypokalemia

19. Risks of treatment of hypokalemia
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Hospital treatment of hypokalemia

20. Risks of treatment of hypokalemia
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Hospital treatment of hypokalemia

21. When to treat – Brenner and Rector recommendations
< 4.0 – Acute MI, CHF, digoxin, severe hepatic dz
< 3.5 – HTN or sxs
< others
12/17/2010
Hospital treatment of hypokalemia

22. Treatment – K-containing foods
Least expensive
Less effective because potassium in foods predominantly potassium phosphate of citrate
Only 40% as effective as KCL
12/17/2010
Hospital treatment of hypokalemia

23. Treatment –oral therapy
K-bicarb – if acidosis
KPO4 - if hypophosphatemic
KCl – all others
Quantity – Studies in normal subjects
↓ 0.3 mEq K →100 mEq total body K depletion
75 mEq KCl → 1 – 1.5 mEq in 90 mins
125 mEq → 2.5 – 3.5 mEq in 60 – 120 mins
12/17/2010
Hospital treatment of hypokalemia

24. Treatment – intravenous therapy (Brenner and Rector)
Reserve for those unable to take orally, K ≤2.5 and true emergencies (significant arrythmias, muscle weakness)
Use non-dextrose containing solutions
If > 10 mEq/hr, cardiac monitoring
KPO4 ≤ 50 mEq over 8 hours
12/17/2010
Hospital treatment of hypokalemia

25. Treatment – intravenous therapy
Crit Care Med 1991;19:694
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Hospital treatment of hypokalemia

26. Treatment – potassium sparing diuretics
Amiloride, triamterene – block Na/K channels
Spironolactone, eplerone – inhibit aldosterone
Caution in diabetics, renal insuff
Freq monitoring of K
12/17/2010
Hospital treatment of hypokalemia

27. Cases – select a response
20 y/o vomiting, K = 2.9
30 y/o asthmatic K = 2.9
40 y/o with DT’s, K = 2.9
50 y/o with CHF, K = 2.9
60 y/o old with Child’s C cirrhosis, K = 2.9
No treatment w/KCl
Oral KCl to get K ≥ 3.5
Oral KCl to get K ≥ 4.0
IV KCl to get K ≥ 3.5
IV KCl to get K ≥ 4.0
12/17/2010
Hospital treatment of hypokalemia

28. Discussion re: consensus practice
Treat urgently
all pts with K < 2.5
sxtic pts with K <3.5 (serious vent ectopy, new atrail fib, or new muscle weakness)
Pts with acute MI and K < 3.5
Treat promptly pts with CHF, IHD, serious liver dz and K < 3.5
Oral therapy is preferred
Use smaller doses and more freq monitoring in pts with hematologic malignancy or if receiving Mg
12/17/2010
Hospital treatment of hypokalemia

29. Possible items to include in a hypokalemia order set
Evaluate pt for underlying conditions (CHF, IHD, cirrhosis)
Option to check magnesium
Option to order K/creat if etiology unclear
Reminder that certain conditions may be due to shifts (periodic paralysis, B-agonists, hyperthyroidism)
Options for routes of administration and types
12/17/2010
Hospital treatment of hypokalemia