Extracellular (serum) potassium concentration is normally maintained within the approximate reference range of 3.5-5.2 mmol/L; this is important for normal cardiac function. Both reduced serum potassium (hypokalemia) and increased serum potassium (hyperkalemia) can, if sufficiently severe, be associated with...

The calcium present in blood plasma comprises two almost equal fractions: half is bound to albumin and the remainder is unbound, free ionized calcium. Only the free ionized calcium is physiologically active. There are two ways of assessing patient blood calcium status.  The first – at one time the only available...

Calcium is an essential mineral required for numerous biological functions. In circulation, calcium is found in three different fractions, anion-bound, protein-bound and free or ”ionized”. The amount of calcium in each of these fractions is dependent on the concentration of hydrogen ions, anions and plasma proteins....

In health, plasma potassium concentration is maintained within the approximate range of 3.5-5.0 mmol/L. Hypokalemia, a very common electrolyte disturbance – present in up to 20 % of hospitalized patients – is diagnosed if plasma potassium is less than 3.5 mmol/L.  Although mild hypokalemia is often asymptomatic, a...

Compared with other plasma electrolytes, such as sodium, potassium and bicarbonate, chloride usually gets very limited coverage in medical texts. Now in a wide-ranging review article chloride gets the exclusive billing that its physio-pathological significance deserves.  The article begins with consideration of the...

According to the authors of a recently published study little is known of the clinical effects of abnormal plasma chloride concentration among the critically ill. Their retrospective study illuminates this apparent grey area of clinical knowledge.  The study involved retrieval and analysis of laboratory data,...

The anion gap (AG) is a calculated parameter derived from measured plasma electrolyte concentrations that is most frequently used to elucidate acid-base disturbances in the critically ill. It is defined as the difference between measured anions and cations in blood plasma and is calculated by subtracting the sum of...

Around 25 % of blood samples recovered from patients admitted to intensive care and 8 % of those recovered from all other hospitalised patients would return a plasma sodium result 4-10 mmol higher than its true value if the method of analysis was indirect ion selective electrode (ISE). This is the headline finding of...

Unless suffering some unrelated acute/critical illness, diabetic patients are only usually submitted for arterial blood gas analysis if they are suspected of suffering diabetic ketoacidosis, the potentially life-threatening acute complication of diabetes that is almost invariably associated with severe hyperglycemia....

Plasma bicarbonate concentration, a parameter generated during arterial blood gas analysis, is essential to the assessment of patient acid-base status. Blood gas analyzers do not have the capacity to directly measure bicarbonate; instead, it is calculated from measured pH and pCO₂(a), using the Henderson-Hasselbalch...