Run maintenance of water homeostasis, maintenance in acid-base balance and muscle functions as well as serves as cofactors for enzymes.
What is the major cation of extracellular fluid?
What does Sodium determine in the extracellular fluid?
When is sodium excreted in the urine?
When serum sodium exceeds 110-130 mmol/L
What happens when serum levels are below 110 mmol/L?
All the sodium in the glomerular filtrate is virtually reabsorbed in the proximal and distal tubules, a process that is influenced by aldosterone.
Sodium specimens consist of…?
And should be stored at…?
Serum, plasma and urine specimens and may be stored at 4°C or may be frozen. Lipemic samples need to be ultracentrifuged.
What are the methods of measuring sodium?
Atomic Absorption Spectrophotometry (AAS),
Sodium Ion selective electrode (ISE), and Spectrophotometry.
What is the major intercellular cation?
How are high concentrations of potassium maintained?
Na+K+ adenosine triphosphate (ATP) pump which is fueled by oxidative energy and continually transports K+ into the cell against a concentration gradient.
Does potassium exhibit a renal threshold?
No, however it is excreted into the urine even in K-depleted states.
What are some of the functions of potassium?
Regulation of neuromuscular excitability (both hypo- and hyperkalemia can cause muscle weakness) and contraction of the heat and cardiac rhythm (decrease K+ increases cardiac excitability and often leads to arrhythmia. High K+ slows the heart rate).
How does potassium affect acid-base status?
In hypokalemic states, sodium and H+ ions move into the cell to replace K+. The H+ concentration is therefore decreased in the ECF=alkalemia (reverse is true of hyperkalemia).
What should the concentration of K+ be?
In plasma and whole blood the concentration is 0.1-0.7 mmol/L lower than those in serum.
How does the release of K+ affect values?
As few as 0.5% K+of RBCs will increase K+ values by 0.5 mmol/L. An increase of K+ of 0.6% has been estimated for every 10 mg/L of plasma hemoglobin (Hb) caused by hemolysis.
What causes glycolysis to be inhibited and the energy-dependent Na+, K+-ATPase will not maintain the Na+/K+ gradient?
When a whole blood specimen is maintained at 4°C versus 25°C before separation.
What does a K+ leakage from erythrocytes and other cells cause?
It causes an increase in plasma K+.
What causes falsely decreased K+ value?
When an un-separated sample is stored at 37°C because glycolysis occurs and K+ shifts intracellularly. Leukocytosis will initially cause falsely decreased K+ concentration at room temp.
In blood gas samples, air bubbles cause (increase or decrease) in total CO2, pCO2, pH, pO2.
Decrease, decrease, increase, increase.
What are the reasons for the following changes in pCO2, pH and pO2 in a sealed specimen left at room temperature for 2 hours:
Increase in pCO2 as a result of continued metabolism, decrease in pH due to increased production of carbonic acid and lactic acid during glycolysis, decrease in pO2 because O2 is consumed during prolonged standing.
Arterialized capillary blood is an acceptable alternative to arterial blood but it has to be:
freely flowing cutaneous blood.
The first drop is discarded and the subsequent free forming drops should be taken up in a: