Before the Draw: Patients, Preparation, Tubes and Order

This is Unit Nineteen of Medical Assistant Prep. Unit Eighteen ran tests in the office. This unit begins the three units on drawing blood, starting before the needle: the patient, the preparation, the tubes, and the order they are filled in. Carry one idea through this lecture. The accuracy and safety of a blood draw are mostly settled before the needle goes in, by the questions you ask and the tubes you choose. Two constructed cases at the end show questions that changed a draw. By the end you will be able to verify the order and identify the patient actively. To ask the questions that change a draw. To choose a site and gather equipment. And to fill tubes in the right order and mix them correctly.

Seven entries on the patient: role, the order, active identification, allergies and fainting, consent, fasting and medications.

Only when trained.

MAS 451 Phlebotomy in the Medical Assistant's Role

Collecting and preparing blood specimens for laboratory tests is a common medical assistant duty. As with every task, you perform blood draws only when the state, the practice and your training allow, and only after you have been checked off. A blood draw is invasive. Never attempt one you have not been trained to do.

Tests decide tubes.

MAS 452 Verify the Order First

Every blood draw begins with an order, which tells you which tests to collect. Check that the laboratory form or requisition matches the patient and lists every test, so you can choose the right tubes before the needle goes in. If the order is unclear or incomplete, ask before collecting, not after.

State your name.

MAS 453 Identify the Patient Actively

Before drawing blood, ask the patient to state their full name, and check it against the laboratory form. Labels need the patient's first and last name plus a second identifier, such as date of birth, matching the paperwork exactly. Asking "Are you John Smith?" invites a mistaken yes. Ask the patient to say their name.

Ask before.

MAS 454 Ask About Allergies and Fainting

Ask the patient about allergies and whether they have ever fainted or felt ill during an injection or blood draw. A history of fainting means positioning the patient lying down if possible and watching them closely; an allergy may change your supplies. Ask before you start, not after the patient turns pale.

Refusal at any time.

MAS 455 Consent and Comfort

Explain the test and obtain the patient's verbal consent; a patient may refuse a blood test at any time before it is drawn. If the patient is anxious or afraid, reassure them and ask what would make them more comfortable. A patient who withdraws consent is not touched. Tell the provider.

Water only.

MAS 456 Fasting Before a Blood Test

Some tests require fasting, which means nothing to eat or drink except plain water for several hours before the draw. A fast usually lasts eight to twelve hours, as the provider instructs; coffee, juice and flavored waters break it. Ask whether the patient fasted as instructed, and note any break, because it can change the results.

Bleeding risk.

MAS 457 Medications That Matter for a Draw

Ask about medications before a blood draw, especially those that affect bleeding. Patients on anticoagulants or antiplatelet drugs may bleed longer afterward; some tests also require the provider's instructions about which medications to hold. Never tell a patient to stop a medication; that instruction comes from the provider.

Five entries on site and equipment: arms to avoid, common veins, gathering supplies, evacuated tubes, and winged sets.

Arms that must not be used.

MAS 458 Arms to Avoid

Some arms must not be used for a blood draw. Avoid an arm on the side of a past mastectomy or lumpectomy, an arm with a dialysis fistula or lymphedema, and any arm with an IV line, where fluids can alter the results. Ask the patient, and check the record, before you choose an arm.

The common veins.

MAS 459 Where Blood Is Usually Drawn

The most common venipuncture sites are the large veins in the bend of the elbow, the antecubital area. The median cubital vein is usually the easiest to puncture; the basilic vein runs near an artery and a nerve, so a puncture there carries more risk. Do not insert the needle where veins branch, because that raises the chance of a hematoma.

Everything within reach.

MAS 460 Gather Everything First

Gather all equipment before you begin, so you never leave a patient with a needle in place. You need the right tubes, needles and holder, a tourniquet, alcohol swabs, gauze, labels, gloves and a sharps container within reach. Keep the tube rack close to you but away from the patient, so it cannot be knocked over.

Tubes fill from the vein.

MAS 461 Evacuated Tubes and Holders

For several tubes, an evacuated tube system with a needle and holder lets each tube fill directly from the vein. A vacuum in each tube draws a set amount of blood; a winged set or a syringe can be used when the evacuated system does not suit the vein. With a syringe, fill tubes through a transfer device, never by hand.

Filling the tubing.

MAS 462 Winged Sets and the Discard Tube

A winged collection set has tubing that holds air. When a light blue coagulation tube is the first tube needed through a winged set, a discard tube is drawn first to fill the tubing, so the coagulation tube receives its full amount. The discard tube is thrown away, not sent to the lab.

Seven entries on tubes: colors, additives, the order of draw, why it matters, inversion, full fill, and capillary order.

Learn the additive.

MAS 463 Tube Colors Can Vary

Collection tubes are coded by stopper color, but colors and additives can vary by manufacturer and laboratory. Learn each tube by its additive as well as its color, and check your laboratory's own chart. When in doubt about a tube, ask the laboratory before drawing.

Additives by purpose.

MAS 464 What the Additives Do

Each additive prepares blood for a kind of test. Light blue holds sodium citrate, for clotting tests such as the prothrombin time. Red and gold yield serum, many with a clot activator, and gold adds a gel that separates serum when spun. Green holds heparin and yields plasma for many chemistry tests. Lavender holds EDTA, for the complete blood count and hemoglobin A one C. Gray holds sodium fluoride, for glucose and lactate. The test decides the tube, so look each ordered test up in the laboratory's catalog rather than relying on memory.

One sequence.

MAS 465 The Order of Draw

Tubes from one venipuncture are filled in a set sequence, the order of draw, which each lab publishes for its tubes. Blood cultures come first, before any tube. Then light blue citrate, then red and gold serum, then green heparin, then lavender EDTA, then gray fluoride. Some labs place specialty tubes within this sequence, so check the lab's own chart. The wrong order can give wrong results or get specimens rejected, which means another needle for the patient. Follow the order every time, even for two or three tubes, with the chart where you draw.

Why order matters.

MAS 466 Why the Order Matters

The order of draw exists to prevent additives from being carried from one tube into the next. The needle that pierces a tube's stopper can carry a trace of its additive into the following tube, which can change that tube's results; cultures go first to protect them from contamination. A small carryover can produce a large error in a sensitive test.

Gently, never shaken.

MAS 467 Inverting Tubes

After filling, tubes with additives are gently inverted to mix the blood with the additive. The number of inversions differs by tube and laboratory; one guide says six to eight for all tubes, another eight to ten, another gives counts by tube. Invert gently, never shake. Follow your laboratory's chart for the count.

Blood to additive ratio.

MAS 468 Let Tubes Fill Completely

Allow each evacuated tube to fill until its vacuum is used up. Many tests depend on a set ratio of blood to additive, and clotting tests in the light blue tube require a full draw. An underfilled tube may be rejected, which means drawing the patient again.

Fingersticks.

MAS 469 Capillary Collections Use a Reversed Order

For skin punctures, such as fingersticks, the order of collection is reversed from venipuncture. The hematology specimen is collected first, followed by chemistry and blood bank specimens, which helps prevent platelet clumping from affecting results. If many specimens are needed, a venipuncture may give more accurate results than a skin puncture.

Three entries close the unit: positioning the patient, and two constructed cases where the questions mattered.

Seated or lying, supported.

MAS 470 Positioning the Patient

Position the patient comfortably and safely before the draw. The patient sits or, if possible, lies down, with the arm extended and supported; a patient with a fainting history should lie down if possible. Have gauze and a bandage within reach before you begin, so you never have to turn away from the patient during the draw.

Coffee and a muffin.

MAS 471 The Patient Who Ate Breakfast

A constructed case pays off the opening idea. The order includes a fasting glucose and a lipid panel. The assistant has the patient state his name and date of birth and checks both against the form. Before gathering the gray and gold tubes, she asks when he last ate. Coffee with cream and a muffin, two hours ago; he forgot the fast. He also takes a blood thinner, so she notes it for firm pressure later. She neither draws anyway nor sends him home; she tells the provider. The provider reschedules, and she repeats the fasting instructions, water only for eight to twelve hours, and has him say them back. A muffin sample recorded as fasting would have misled the provider. Her job was to give the provider the facts.

A restriction and a fainting history.

MAS 472 Choosing an Arm

A second constructed case chooses an arm. A woman in her sixties says she had a mastectomy on her left side and was told never to let anyone use that arm. The record confirms it, and the assistant notes it for every future visit. She has also fainted during draws, so the assistant has her lie down with the right arm supported. She finds a straight, visible vein in the bend of the elbow, away from where veins branch, explains each step, and asks her to speak up if lightheaded. The rack sits out of reach, with gauze and a bandage ready. Afterward the patient rests lying down before sitting up slowly. Neither the restriction nor the fainting could be seen; asking first prevented both a lymphedema risk and a fall.

Look at what you can now do. You can verify the order, have the patient state their name, and ask about allergies, fainting, consent, fasting and medications. You can choose a safe arm and site and gather everything before you begin. You can match tubes to tests by additive, fill them in the order of draw, invert gently and let each tube fill completely. And you can position the patient and bring every answer that changes a draw to the provider. Unit Twenty turns to the draw itself: venipuncture and capillary puncture.