Lab Abnormalities

Question 1

Hyperkalemia

Answer 1

• ECF/ serum [K] = 3.5-5.0 mmol/L
• ICF [K] = 140 mmol/L

Etiology
- Dec renal K excretion (kidney disease), transcellular shifts K out (ie insulin def), pseudohyperkalemia (leukocyte or platelet breakdown), massive tissue breakdown (hemolysis, rhabdo), drugs that dec aldosterone (ACEI, ARB, NSAID, B-blocker, heparin, cyclosporine, K sparing diuretics).

S+S

• ↑ ECF or plasma [K] –> ↓ ICF: ECF ratio –> ↓ RMP –> ↓ electrical conduction
• Cardiac conduction block (1-3 degree block + bradyarrhythmia)
• ECG: peaked T waves, flat P waves, prolonged PR + QRS, sine wave + brady if severe.
• Weakness, GI (N/V), paralysis

Tx

• Calcium
• Trans-cellular shifts into cell: insulin, B-adrenergic ie salbutamol, bicarb
• Loop diuretic
• Kayexalate

Question 2

Hypokalemia

Answer 2

• ECF/ serum [K] = 3.5-5.0 mmol/L
• ICF [K] = 140 mmol/L

Etiology
- Transcellular shifts K in, inc non-renal loss (diarrhea), inc renal loss (ex inc aldosterone), and other rare syndromes

S+S

• ↓ ECF or plasma [K] –> ↑ ICF: ECF ratio –> ↑ RMP –> ↑ electrical conduction.
• Tachyarrhythmia
• ECG: dec T wave, U wave
• Weakness, fatigability, rhabdomyolysis

Dx

1) Check urinary K excretion, ie via TTKG (separate card)
2) Acid base status to narrow ddx. (And normal = transcellular shift)

Tx

• KCl tablets or IV, 25mg for every 0.3 K you want to go up. Can space it through the day.
• Note: also check for dec Mg - often lost together and Mg is needed for renal conservation of K.

Question 3

Hypernatremia (hyper-osmolar)

Answer 3

S+S
- Weakness, lethargy, seizures, coma

Hypovolemic (low Na, lower H2O)

• Renal: diuretics, glycosuria
  
  • > UNa >20, FeNa >1%, variable UOsm
• Non-renal: GI loss (ie diarrhea), skin loss (++sweating), respiratory loss, adrenal insufficiency
  
  • > Na 400
• Tx: hypotonic saline

Euvolemic (normal Na, lower H2O)

• Renal: DI.
  
  • > UOsm < POsm
• Non-renal: sweating
• Tx: H2O replacement

Hypervolemic (high H2O, higher Na) (usually iatrogenic)

• Renal: renal failure w NaHCO3 or hypertonic NaCl.
  
  • > UNa >20, FeNa >1%, UOsm Na 400
• Tx: Diuretics + H2O
• Dont adjust too quickly in case of cerebral edema
• Target: dec <1mmol/L/hr, 50% correction at 24-36 hrs, complete correction at 3-7 days.

Question 4

Hyponatremia (hypo-osmotic)

Answer 4

• Usually workup use corrected Na. Also mannitol, contrast, sorbitol)
• R/o pseudohypoNa (falsely large volume - ie lipids, paraproteins)

S+S

• Sx usually occur at Na UNa >20, FeNa >1%, UOsm Na 400. Low UCl if vomit.
• Tx: NS (hypertonic if sx)

Euvolemic (normal Na, higher H2O)

• Renal (impaired excretion): 1° adrenal insufficiency, hypothyroidism, SIADH (dx of exclusion).
  
  • > UOsm >100. AM cortisol, TSH, etc. SIADH will have v low uric acid + BUN.
• Non-renal: 1° polydypsia.
  
  • > UOsm UNa >20, FeNa >1%, UOsm Na 400.
• Tx: Na restriction (2-3g/day), H2O restriction (1-1.5L/day) + loop diuretics
• For sz/ coma: raise SNa by 5mmol/L.
• Monitor closely to avoid CPM
• Target: inc Na to 120 mmol/L at a rate of 1-2 mmol/L/hr, and then by 0.3-0.5 mmol/L/hr.
• Also ecstasy can cause hypoNa from inc thirst/ ADH release

Question 5

BUN: Cr

Answer 5

• N = 10-15: 1
• Inc: pre-renal -> inc urea reabsorption –> inc BUN: Cr, >=20:1. Also high protein diet, catabolic states, GI bleeding,
• Dec: liver failure, malnutrition

Question 6

HyperCa

Answer 6

1. Increase PTH
   - > primary PTH: adenoma 85%, hyperplasia 10%, carcinoma 5%, MEN syndromes (1 + 2a)
   - > tertiary PTH
   - > FHH: Ca sensing receptor interaction. dx with lithium: Ca sensing receptor interaction
2. Low PTH
   - > malignancy: primary bone, mets (from “2’s” - breast, renal, lungs, prostate), PNS (SCC&raquo_space; NSCLA), lymphoma (alpha 1 hydroxylase activates Vit D)
   - > granulomatous disease: sarcoid, TB, alpha 1 hydroxylase
   - > inc vit D: inc vit a, hctz (unmasks but doesn’t cause)
   - > chronic immobilization (most common)

S+S

• CNS: lethargy, somnolence, delirium
• Renal: nephrogenic DI/ polyuria, nephrocalcinosis
• Bone: pain, weakness
• GI: constipation, abdo pain, pancreatitis, N/V

Tx

1. A symptomatic/ mild
   - surgical criteria: >50 yrs, inc Ca >0.25mmol/L, CrCl 3.5: >150/hr, see above. Sometimes dialysis
2. Post-op primary PTH
   - “Hungry bones”: bones have down regulated PTH receptors, or bones are used to lots of PTH and need more. Low Ca + PTH