1. Diagnosis and Management of Common Electrolyte Disorders
Eric I. Rosenberg, MD, MSPH, FACP
Rev 11/06 electrolytes1106

2. Objectives To discuss diagnostic and therapeutic strategies for:
Hyponatremia
Hypernatremia
Hyperkalemia
Hypokalemia

3. Case 1 60 year old man “Admit for weakness and hyponatremia”
[Na+] 120 mg/dL

5. Clinical Evaluation History Physical Labs Symptomatic? Predisposed?
Medications? IVF’s?
Physical
Volume status?
Labs
Confirm (if unusually abnormal)
Context
Additional diagnostic tests

6. Case 1 (cont’d) Nausea, weak, confused x 1 week HTN, CHF
JVD, crackles (rales), edema
Na+ 120 mEq/L
BUN 93 mg/dL
Cr 3 mg/dL
Glucose 135 mg/dL
Albumin 2.9 mg/dL
Plasma osm 252 mOsm/kg
Urine osm 690 mOsm/kg

7. “Choose the most appropriate treatment”
3% I.V. NaCl
0.9% I.V. NaCl
50 mg hydrochlorothiazide daily
Salt and water restriction
Demeclocycline

8. Differential diagnosis

9. Hyponatremia usually reflects excessive H20

10. Common Differential Dx
Decreased Water Excretion
GFR
Kidney perfusion
SIADH
Addison’s Disease
Malnutrition
*Pseudohyponatremia
±Psychogenic (>1 L / hour)
Prompt them for answers
*100mg/dL glucose increase  1.6 mEq/L [Na] decrease
± Urine specific gravity < 1.003

11. COMMON CAUSES of HYPONATREMIA
History: predisposing features
Exam: volume status (including orthostatics supine/standing)
BMP; Urinalysis; Serum Osmolality; (Urine Sodium; Urine Osmolality)
Head C.T. (if symptomatic)
Other imaging/labs to evaluate CV, Renal, Endocrine systems as needed

12. Complications of Treating Hyponatremia
Delayed treatment
Cerebral edema
Permanent neurological injury
Death
Inappropriately rapid treatment
Cerebral dehydration/demyelination
Inappropriate treatment
Failure to improve  morbidity
Delayed improvement  morbidity
Further deterioration

13. Common Treatment Options
Water restriction
Diuresis (with loop diuretic)
Volume infusion (with crystalloid)
Hypertonic saline
Demeclocycline

14. What if he had cerebral edema?
Correct [Na+] to mEq/L to temporarily relieve edema
[Na+] should NOT increase by more than mEq/L in 1st 24 hours
Slow/Stop infusion as soon as symptoms improve

15. 3% NaCl Calculation [Na+] = 116 mEq/L
Goal [Na+] = 125 mEq/L at 24 hours
Amount of Na+ to be given as 3% infusion:
= [Serum Na+ (desired) – Serum Na+(measured) ] (TBW)
= [125 – 116] [(0.5)(60kg)]
= 270 mEq Na+
3% saline = 513 mEq sodium/L
270/513 = 0.5 L = 500 ml over 24 hrs.

16. Hyponatremia: Key Points
127 mEq/L
Excess water
If symptomatic, treat rapidly
Slowly correct [Na+] *towards* normal
Find the underlying cause

17. Case 2 40 y/o woman s/p hypertensive brain hemorrhage 2 weeks ago.
This morning she’s less responsive.
What may have caused this new problem?

18. Stuporous
BP 150/70, HR 94
Dry mouth, poor turgor
Na 160 mEq/L; K 2.8 mEq/L; HCO3: 18 mEq/L; Cl 137 mEq/L

19. Differential diagnosis

20. Hypernatremia usually reflects insufficient H20

21. Differential Diagnosis
Lack of water
Severe diarrhea
Severe burns
H20 excretion
Osmotic diuresis
H20 conservation
Diabetes insipidus

22. Guidelines for Hypernatremia Rx
Determine and treat likely cause(s)
Most common error is “underguesstimation” of water deficit:
TBW x ([Na+(measured)] – [Na+(desired) ])/[Na+ (desired)]
Replace H20 enterally if possible
Frequent monitoring

23. Sodium Content of IVF’s (mEq/L)
3% saline: 513
0.9% (normal) saline: 154
Ringer’s Lactate: 130
Half Normal (0.45%) saline: 77
5% Dextrose (D5W): 0

24. Hypernatremia: Key Points
[Na+] >145 mEq/L
Net water loss
Calculate the water deficit
[Na+] >145 mEq/L
Usually inadequate water intake in an obtunded/ill person
Increased [Na+] in ECF  Water shift from ICF  Cerebral shrinkage  lethargy, coma, ICH from tearing of bridging veins

25. Case 3 29 y/o man with severe muscle weakness.
No vomiting or diarrhea.
Normal physical exam.

26. Na = 141 mEq/L
K = 1.4 mEq/L
Cl = 116 mEq/L
HCO3- = 11 mEq/L
pH = 7.25, pCO2 = 21 mmHg

27. Consequences of Hypokalemia [K] <3
Neuromuscular manifestations
Weakness, fatigue, rhabdomyolysis, myonecrosis, respiratory failure
GI symptoms
Constipation, ileus
Nephrogenic Diabetes Insipidus
Dysrhythmias (if heart disease)

28. Common Causes of Hypokalemia
Malnutrition/NPO
Diarrhea (100 mEq/L)
Vomiting (volume depletion)
DRUGS
Thiazides (stimulate excretion)
Amphotericin B
Penicillins
Gentamicin
Foscarnet

29. “Choose the most likely diagnosis”
Bartter’s syndrome
Laxative abuse
Primary aldosteronism
Diuretic abuse
Distal renal tubular acidosis

30. Less Common Causes Hormonal Renal tubular disease
Primary hyperaldosteronism
Adenomas, hyperplasia, ectopic ACTH, ectopic mineralocorticoid (licorice, chaw)
Secondary hyperaldosteronism
Renal hypoperfusion (CHF, RAS, severe HTN)
Renin-secreting tumor
Renal tubular disease
Type 1 or 2 RTA
Bartter’s syndrome (metabolic alkalosis, polyuria)
Chronic magnesium depletion
Laxative abuse (metabolic alkalosis)

31. Hypokalemia Rx Recognize likely total body depletion
1 mEq/L decrease = mEq total deficiency
Gradual oral replacement
I.V. replacement if serum level less than 3 mEq/L
Check & Replace magnesium
Consider telemetry

32. Hypokalemia: Key Points
[K+] < 3.5: review medications, review health status
[K+] < 3: intervention
Recognize Mg+ is cofactor
Renal/CV monitoring

33. Case 4
59 y/o man with 3-days malaise, decreased mental acuity and responsiveness, slurred speech.
ESRD on hemodialysis; HTN, DM, Hypothyroidism

34. Disoriented and lethargic
BP (supine) 148/79mmHg, HR 101/min (supine) RR 26/min, T 37.7oC.
Mucous membranes are moist, neck veins are distended. Bilateral crackles and wheezes. Loud S peripheral edema.

37. Begin I.V. infusion of normal saline for volume repletion
What is the next most appropriate step in managing this patient?
Begin I.V. infusion of normal saline for volume repletion
Administer 1 ampule dextrose and 10 units insulin I.V. for hyperkalemia
Transfer to the ICU and perform emergent peritoneal dialysis
Transfer to the ICU and perform emergent hemodialysis

38. “Dialysis machine available in 20 minutes”

39. Emergency Treatment [K] > 6 mEq/L
“STAT” ECG
“STAT” repeat [K+]
Give IV Calcium

40. Additional Rx More IV Calcium Glucose and Insulin Bicarbonate
Inhaled Beta-2 agonists
Sodium polystyrene sulfonate (Kayexalate®)

41. Severe hyperkalemia is usually preceded by moderate, uncorrected hyperkalemia

42. Differential Dx Renal Failure (GFR < 10 ml/min) Extra Renal Causes
Metabolic acidosis
Cell lysis (chemotherapy, trauma)
Salt substitutes, ACE-I/ARB,
Addison’s Disease
Pseudo (coagulated RBC’s/platelets)

43. Hyperkalemia: Key Points
K>4.5: caution with medications, & monitor
K>5.5: intervene
Calcium (not kayexalate) is 1st line
Check ECG

44. SUMMARY Construct your differential Know the complications of therapy
Know the implications of lack of therapy
Calculate water/electrolyte needs
… But repeated and frequent monitoring is most important.
Electrolyte disorders may be a diagnostic clue or an expected consequence of therapy