Hemodialysis and related treatments for those with failing kidneys all involve blood flow through a circuit outside the body. This extracorporeal circuit - the dialysis machine and its connections from and back to the body - is a non-physiological, pro-coagulant environment.  To counter the tendency for patients'...

The process of patient sample testing, whether performed in the clinical laboratory or at the point of care, is the sum of three distinct phases. The first is the preanalytical phase, which includes test selection as well as sample collection and handling.  The second is the analytical or measuring phase that...

Hypokalemia, one of the most common electrolyte disturbances, is diagnosed if plasma potassium concentration is less than 3.5 mmol/L. Mild hypokalemia (plasma potassium 3.0-3.5 mmol/L) is usually asymptomatic, but greater degree of hypokalemia can result in signs and symptoms that reflect the fundamental role of...

Of all blood chemistry parameters, sodium is one of the most frequently measured among hospitalized patients, including those admitted to critical care units. The assay is generally available on point-of-care analyzers sited in these units. Incidence of abnormality in plasma sodium concentration among critically ill...

Plasma electrolytes, which include sodium, potassium, chloride, calcium and magnesium, are among the most frequently measured blood analytes in clinical medicine. All are measured by ion-selective electrodes (ISE). ISEs are present not only in clinical laboratory instrumentation but also in blood gas analyzers and...

The serum (plasma) anion gap is a useful additional piece of clinical information that can be easily derived without cost from the results of the most commonly requested biochemical profile, urea and electrolytes (U&E). It is the difference between the sum of measured anions (chloride and bicarbonate) and the sum of...

Potassium is one of the blood analytes most frequently measured in the clinical laboratory and at the point of care. Compared with most laboratory measurements, potassium is unusually prone to preanalytical error so that pseudohyperkalemia, defined as raised serum or plasma potassium concentration despite normal in...

Critical values are those associated with imminent danger unless acted upon promptly. Critical value menus often include results that do not fit this definition, leading to highly variable practice in adult and pediatric laboratories. Existing menus may be subdivided into more uniform tiers of severity: the highly...

The anion gap (AG) is a calculated parameter derived from measured serum/plasma electrolyte concentrations. The clinical value of this calculated parameter is the main focus of this article. Both increased and reduced anion gap have clinical significance, but the deviation from normal that has most clinical...

The incidence and significance of hypernatremia (raised plasma sodium) acquired during critical illness is the subject of a recently published retrospective study conducted at the combined medical and surgical intensive care unit of a Brisbane hospital where plasma sodium of all patients is regularly monitored...