phlebotomy
Meaning of phlebotomy: Routine enough to be invisible, yet most laboratory results and every unit of donated blood begin with this one procedure.
Definition of phlebotomy
Phlebotomy is the act of puncturing a vein with a needle to withdraw blood. Most draws are for laboratory testing or for blood donation, and some are treatment in themselves, since removing blood at intervals lowers the iron load in hemochromatosis and the red cell count in polycythemia. The person trained to perform it is a phlebotomist.
How phlebotomy is built
- phleb/o Combining form · Greek vein
- -otomy, -tomy Suffix · Greek cutting into, incision
A medical term is read from its ending backwards: the suffix first, then the prefix, then the root. See all 223 word parts.
How is a blood draw done?
The usual site is the crook of the elbow, where several veins run close to the surface and away from arteries and major nerves. A tourniquet above the site fills the veins so one can be felt rather than merely seen, the skin is cleaned, and a needle is advanced at a shallow angle into the vein. Blood is drawn into sealed tubes held at low pressure, each containing a different additive, and the tubes are filled in a set order so that an additive from one cannot carry over and distort the next. Pressure over the site afterward closes the puncture. Where only a drop or two is needed, a lancet prick to a fingertip or an infant's heel serves instead, and blood is sometimes drawn back through a line already in place rather than by a fresh puncture. Careful technique matters to the result as well as to comfort: a tourniquet left on too long, or a sample shaken hard, alters the numbers a laboratory test reports.
Why is blood removed as a treatment?
| Condition | Why blood is removed |
|---|---|
| Hereditary hemochromatosis | Each unit removed takes iron with it, lowering the iron stored in organs |
| Polycythemia vera | Thins blood that has become too thick with red cells |
| Porphyria cutanea tarda | Reducing iron reduces the skin fragility and blistering |
This use is called therapeutic phlebotomy, and it is the surviving remnant of bloodletting, which was applied to almost everything for centuries with no benefit. Blood taken for donation follows the same technique but a larger needle and a much larger volume, and it feeds the supply used for blood transfusion.
What can go wrong?
Bruising at the site is the most common problem and comes from blood leaking around the puncture. Fainting occurs in a minority of people through a reflex drop in heart rate and blood pressure, which is why draws are often done seated or lying down. Less often a nerve near the vein is irritated, causing brief shooting pain or tingling. Infection is rare with sterile single-use equipment. On the laboratory side, red cells damaged during collection release potassium and hemoglobin, which can make a result unusable and require a repeat draw.
Also known as
Used in a sentence
The nurse performed phlebotomy to obtain the blood samples ordered for the morning laboratory panel.
Good to know
Phlebotomy specifically refers to blood collection from a vein, while venipuncture is the broader term for any needle puncture of a vein, including one performed to start an intravenous line rather than draw blood.
Word origin
Where “phlebotomy” comes from
Formed from phlebo-, from Greek phleps, phlebos, meaning vein, and -tomy, from Greek tomia, meaning a cutting.