| Electrolytes |
This provides information about serum Na+, K+, Cl-, HCO3- |
| BUN and Cr |
These measures provide an indication of renal perfusion. An elevated
BUN generally reflects intravascular depletion. Creatinine is a useful
indicator of acute renal failure. |
| CBC |
The CBC may provide some indication of hemoconcentration in cases of
dehydration. The WBCs and differential cell count are useful indicators
of infection. Platelets can elevate as acute phase reactants. |
| UA |
The specific gravity of the urine is related to the patient's hydration
state. In cases of renal disease, it can help classify the condition.
Urine ions can be specifically requested, and are helpful in determining
whether sodium is being retained or not. |
Serum/Urine
Osmolarity |
A true measure of serum osmolarity can be compared to the calculated
osmolarity. Normally, true osmolarity is about 10 mEq/L higher than calculated
due to the presence of particles which are not in the basic osmolarity
equation. If there is a greater "osmolar gap" than this, the presence of
additional particles should be considered (such as alcohol or mannitol).
The osmolarity of serum determines whether a patient is in an isotonic
state or if this state has been disturbed. Urine osmolarity is helpful
in determining if the kidney is doing its job of concentrating urine. |
| Total Protein |
Total protein, and sometimes albumin levels, are indirect measures
of both liver function (where they are produced), dietary protein intake,
and renal loss. If serum protein levels fall, the intravascular oncotic
pressure falls and fluid migrates to "third spaces". This can be seen in
liver disease, nephrotic syndromes, malnutrition and other cases. |
Arterial Blood
Gas |
In addition to providing information about the patient's blood gases
and assisting in classification of acidosis or alkylosis, the ABG yields
information about bicarbonate levels. Usually, STAT electrolytes
can also be obtained from a blood gas sample, with turn around time better
than serum chemistry. |
