DSA 2 Flashcards
Normal ranges of plasma: K+, Ca2+, PO4, Mg2+
- 3.5-5mEq/L
- 1000mg/day
- 1500mg
- 1.8 mEq/L
Where is K+ distributed throughout the body?
98% ICF, 2% ECF
*of the ICF, 80% muscle cells, 20% other cells
What causes the difference between K+ ICF and ECF levels?
Na/K ATPase, NKCC2, K+ channels, Transcellular distribution regulated by other factors
Hypokalemia
- Plasma [K+] < 3.7
- Vomiting/diarrhea, insulin excess, deficiency, alkalosis
- Hyperpolarizes the membrane, and cell is less excitable
Hyperkalemia
- Plasma [K+] >5.2
- Excess intake, tissue release (rhabdomyolysis, burns, hemolysis), shifts ICF–>ECF (acidosis, insulin deficiency, tissue damage, hyperglycemia)
- Hypopolarizes the membrane, and cell is more excitable
Pseudohyperkalemia
- artificially high Plasma [K+]
2. RBC lysis during blood daw
How is K+ excreted from the body?
- Feces (10)
- Kidneys (60)
*assuming 70 intake via GI
How do cardiac cells respond to hyperkalemia? hypokalemia?
- hyper polarizes membrane–>less excitable (brady)
a. tall, peaked T wave - hypo polarizes membrane–>more excitable (tachy)
a. low T wave
Cell Volume Maintenance:
a. Net loss of K+
b. Net gain of K+
a. cell shrinkage
b. cell swellings
Intracellular pH regulation:
a. Low plasma [K+]
b. High plasma [K+]
a. cell acidosis
b. cell alkalosis
DNA/protein synthesis, growth:
a. Lack of K+
a. reduction of protein synthesis, stunted growth
RMP:
a. Reduced [K+]i/[K+]o
b. Increased [K+]i/[K+]o
a. membrane depolarization
b. membrane hyperpolarization
Neuromuscular activity:
a. Low plasma [K+]
b. High plasma [K+]
a. muscle weakness, muscle paralysis, intestinal distention, respiratory failure
b. initially increased muscle excitability; later–>muscle weakness (paralysis)
Cardiac activity:
a. Low plasma [K+]
b. High plasma [K+]
a. prolonged repolarization; slowed conduction; abnormal pacemaker activity–>tachyarrhythmias
b. enhanced repolarization; slowed conduction–> bradyarrhythmias and cardiac arrest
Vascular resistance:
a. Low plasma [K+]
b. High plasma [K+]
a. vasoconstriction
b. vasodilation
How does insulin affect K+ distribution?
enhanced cell uptake
How does beta-catecholamines affect K+ distribution? alpha-catecholamines?
a. enhanced cell uptake
b. impaired cell uptake
How does acidosis affect K+ distribution? alkalosis
a. impaired cell uptake
b. enhanced cell uptake
How does external K+ balance affect K+ distribution?
loose correlation
How does cell damage affect K+ distribution? hyperosmolality?
a. impaired cell uptake
b. enhanced cell efflux
3 ways Ca2+ can enter circulation
- Reabsorption from the kidneys
- Resorption from bones
- Ingestion
What does hypocalcemia cause? hypercalcemia?
- Increases neuromuscular excitability (tetany/spasticity)
- Depress neuromuscular excitability (threshold shifts away from RMP)
*Regulators: PTH, calcitonin, caclitriol
What can cause elevated serum Ca2+? Low levels?
- Primary hyperparathyroidism, malignancy
2. Hypoparathyroidism, renal disease, vitamin D deficiency
Where is phosphate distributed throughout the body?
a. bone - 85%
b. cells - 14%
c. serum - 1%
*lost through stool, urine, or distribution into bone