CLINICAL LAB SCIENEC

CHAPTER 14: CLINICAL CHEMISTRY 383
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant
or other cleaning solution
2. Report form provided by your instructor
3. Non-hemolyzed sample of serum or plasma (not
from EDTA anticoagulant as K+ would be artificially
increased (Potassium ions (K + ) are greatly
elevated in hemolyzed serum or plasma due to
the rich supply of intracellular K + in RBCs) (note
that some instruments require cartridges for
testing and quality control)
4. Quality control samples
5. Electrolyte analyzer
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Electrolyte procedures do not require specific
steps for determining the blood levels of
electrolytes, as the procedure for the measurement of electrolytes is almost
entirely performed by instruments that require little specimen preparation and
little operator expertise and training. The sample is introduced into the instrument,
which contains two electrodes. The reference electrode has a known
FIGURE 14-5 Nova CCX analyzer that uses ion-selective
electrode technology for a variety of analyses.
Source: Delmar/Cengage Learning.
concentration of the ion to be measure. A reference electrode is present for each
of the electrolytes to be measured (e.g., sodium [Na + ], potassium [K + )]). The difference
between the electrical potential across a membrane in the electrode is
proportional to the concentration of the ions (charged atoms). A microprocessor
converts the voltage to a digital figure representing the ion concentration of the
unknown sample. Each of the electrodes is ion specific and will react only to a
particular electrolyte.
4. Procedures for measuring electrolytes in some instruments may differ. The i-Stat
analyzer distributed by Abbott Laboratories requires placing the patient’s sample
into a disposable cartridge with two reservoirs, one for a calibration solution
and the other for the sample. Other instruments may use a probe to aspirate the
sample into the machine. Some instruments perform a variety of tests other than
electrolytes and use various methods to place the sample into the analyzer.
5. Discard all supplies used for the procedure in the appropriate containers. A disinfectant
should be used to clean the work surfaces and equipment should be
cleaned and restored to its former position. Gloves should be discarded appropriately
and the hands washed thoroughly in accordance with established policies.
Reporting of Results
Report your findings from the Electrolytes procedure in the form supplied by your
instructor. The four major electrolytes most often tested for are reported as follows:
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