What is the NORMAL range for Plasma [K+]?
3.5-5.0 mEq/L
What is the NORMAL K+ distribution in the body?
Total K+ = 3500 mEq
ICF = 98%
- 80% Muscle Cells
- 20% Other Cells
ECF = 2 % (3.5-5.0 mEq/L)
What accounts for the 30 FOLD difference between ECF and ICF [K+]?
- Na+/K+ ATPase
- NKCC2
- K+ Channels
- Transcellular distribution via other factors
What values define HYPOkalemia?
Plasma [K+] < Approx. 3.7 mEq/L
What are 4 COMMON causes of HYPOkalemia?
- Vomiting / Diarrhea
- Insulin EXCESS
- Deficiency
- Alkalosis
What are the values for HYPERkalemia?
Plasma [K+] > Approx. 5.2 mEq/L
LETHAL > 10 mEq/L
What are 3 COMMON causes of HYPERkalemia?
- Excessive Intake
- Tissue Related
- Rhabdomyolysis
- Burns
- Hemolysis - Shifts from ICF —> ECF
- Acidosis
- Insulin Deficiency
- Hypergylcemia
- Tissue Damage
What is PSEUDOhyperkalemia?
Artificially high plasma [K+] due to RBC lysis while blood drawn.
What are 2 major routes of K+ LOSS from the body?
- Kidneys —> Urine (Majority)
2. GI —> Feces
In regards to EXCITABLE tissue cells, how does HYPOkalemia effect resting membrane potential?
HYPOkalemia results in HYPERPOLARIZED resting membrane.
Membrane is MORE NEG. —> Stronger impulse needed to fire.
In regards to EXCITABLE tissue cells, how does HYPERkalemia effect resting membrane potential?
HYPERkalemia results in HYPOPOLARIZED resting membrane.
Membrane is LESS NEG. —> Less impulse needed to fire.
In CARDIAC cells, how do HYPOkalemia and HYPERkalemia effect membrane potential, respectively?
HYPOkalemia —> HYPOpolarizes membrane
HYPERkalemia —> HYPERpolarizes membrane
What are the characteristic EKG changes seen with HYPOkalemia and HYPERkalemia, respectively?
HYPOkalemia —> LOW T-Wave
HYPERkalemia —> PEAKED T-Wave
What is the normal value for dietary Ca2+ intake?
Approximately 1000 mg/day (Adults)
Note: Absorption best if at doses <500 mg in one sitting.
Which group is at the highest risk for Ca2+ deficiency?
Adolescents
Followed by:
- Postmenopausal women
- Vegetarians
- Lactose Intolerant
Where are the 3 places Ca2+ can enter circulation?
- Resorption from kidney
- Resorption from bone
- Ingestion via GI Tract / Diet
What are the major routes of Ca2+ LOSS from the body?
Feces - Majority
Urine
Which enzyme is involved in Ca2+ ABSORPTION from the GI Tract?
Calcitriol
Which enzymes are involved in bone formation? Resorption?
Bone Formation - Calcitonin
Bone Resorption - PTH, Calcitriol
How does HYPOcalcemia effect neuromuscular excitability?
INCREASES neuromuscular excitability
How does HYPERcalcemia effect neuromuscular excitability?
DECREASES neuromuscular excitability
What are the 2 differential diagnoses (Ddx) for HYPERcalcemia?
- Primary Hyperparathyroidism
2. Malignancy
What are the 3 differential diagnoses (Ddx) for HYPOcalcemia?
- HYPOparathyroidism
- Renal Disease
- Vitamin D Deficiency
What is the normal dietary intake requirement for phosphate?
Approximately 1500 mg/day.
