Concentration Of Chloride - Siemens Rapidlab 1200 Operator's Manual

Rapidlab 1200 Operator's Guide: System Overview and Intended Use 1-43
Most potassium is excreted by the kidney, which is the major regulator of
potassium output in the body. Actually, the kidney is better at conserving sodium
and excreting potassium so in cases where potassium intake stops, the kidney
requires time to adjust and stop excreting potassium. Two hormones, insulin and
aldosterone, can affect the extracellular level of potassium. Both insulin and
aldosterone influence intercellular uptake of potassium, while aldosterone causes
increased potassium excretion through the kidney.
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High concentrations of K commonly stem from renal insufficiency (or failure),
excessive potassium replacement, drug effects (including some diuretics),
hemolytic disease, or crush injury. Low concentrations stem from gastrointestinal
loss, dietary insufficiency, or drug effects (most diuretics). Other metabolic
imbalances (acid-base, mineralcorticoid, glucocorticoid, insulin effects) also
cause abnormal potassium concentrations. An extremely abnormal plasma
potassium concentration may itself directly cause neuromuscular paralysis,
respiratory failure, cardiac arrhythmia, or cardiac arrest. Thus extreme
abnormalities of potassium reflect a potentially life-threatening pathophysiologic
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state that must be corrected promptly.
Potassium Sensor
The potassium sensor is a half-cell that combines with the external reference
sensor to form a complete electrochemical cell. The sensor contains a silver/silver
chloride wire surrounded by an electrolyte solution that has a fixed concentration
of potassium ions. The membrane, which consists of the ionophore valinomycin
immobilized in a plasticized PVC (polyvinyl chloride) matrix, separates the
electrolyte solution from the sample. Valinomycin is a neutral ion carrier that is
highly selective for potassium ions over other clinically encountered cations.
As the sample comes in contact with the membrane of the potassium sensor, a
membrane potential is created by the interaction of potassium ions with the
membrane. The potential developing in the potassium sensor is compared to the
constant potential of the external reference sensor. The final measured potential is
directly proportional to the potassium ion concentration in the sample. The
potential developed by the electrochemical cell varies with the ion activity in each
sample.

Concentration of Chloride

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Chloride (Cl ) is the major extracellular anion in the body. Cl plays a large role in
maintaining electrical neutrality and normal osmolality, and it participates in the
regulation of acid-base balance. The kidneys are the main regulator of chloride in
the body. Serum levels of chloride usually correspond to increases and decreases
of sodium. Clinically, the serum chloride level alone is rather meaningless. A
change in chloride level does not reveal much about a patient's condition; it must
be viewed as part of the overall fluid and electrolyte status.
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