Complications, Adverse Reactions, Preanalytical Errors, Handling/Labeling/Transport & Chain of Custody

Adverse Patient Reactions

Some patients react to venipuncture itself rather than to any technique error. Recognizing early warning signs and responding immediately protects the patient from injury:

• Syncope (fainting) or presyncope — signs include pallor, diaphoresis (sweating), dizziness, and reports of feeling faint. Response: stop the draw immediately, release the tourniquet, remove the needle and engage the safety device, support the patient to prevent a fall, lower the head below heart level or lower the patient to the floor or a reclined position, loosen tight clothing, apply a cool compress, and monitor vital signs until recovered. Never leave the patient alone.
• Nausea or vomiting — provide an emesis basin, a cool cloth, and reassurance; if severe, treat as for syncope by stopping the draw and removing the equipment.
• Seizure — stop the draw, remove the needle and tourniquet immediately, protect the patient from injury by clearing the area without restraining the limbs and without placing anything in the mouth, and call for emergency assistance.

In every adverse reaction, the priority sequence is the same: stop, remove the tourniquet and needle, protect and support the patient, call for help, then document.

Procedural Complications

Preanalytical Errors

Most laboratory errors occur before testing begins, in the preanalytical phase, and phlebotomy technique is a leading cause:

• Hemolysis — red cell rupture that releases intracellular contents, such as potassium, into the specimen, falsely altering results. Common causes include drawing through a hematoma, using too small a needle gauge for the draw method, vigorous shaking instead of gentle inversion, pulling a syringe plunger back too fast, or forcing blood through a small needle into a tube.
• QNS, or quantity not sufficient — an underfilled tube, especially critical for citrate coagulation tubes, which require an exact blood-to-additive ratio; an underfilled citrate tube must be rejected and redrawn.
• Wrong tube or additive — drawing the incorrect tube color for the ordered test invalidates results; for example, a chemistry panel drawn in an EDTA tube shows falsely low calcium because EDTA chelates it.
• Clotted specimen — insufficient or delayed mixing of an anticoagulated tube.

Specimen Labeling

Specimens must be labeled at the patient's bedside, immediately after collection, in the patient's presence, and never prelabeled before the draw. Each label must include, at minimum, the patient's full name, date of birth or unique identifier, the date and time of collection, and the collector's initials. Labeling before collection risks attaching the wrong label to the wrong patient's tube, a serious identification error.

Specimen Transport

Certain analytes are unstable and require specific transport conditions:

• Light-sensitive specimens, such as bilirubin and some vitamins, must be protected from light by wrapping in foil or an opaque bag, because light exposure degrades the analyte and falsely lowers results.
• Chilled or iced specimens, such as ammonia, lactic acid, and blood gases, must be transported on ice immediately to slow metabolic changes in the sample.
• Room-temperature specimens must reach the lab within the time frame defined by the test, since many chemistry tests should be processed within about two hours of collection to avoid glycolysis and cellular changes, except in fluoride/oxalate tubes, which stabilize glucose longer.
• Specimens must never be transported by pneumatic tube if the test is tube-sensitive, such as some coagulation or fragile-cell tests, per facility policy.

Documentation After an Incident

Any adverse reaction or complication, from a vasovagal episode to a hematoma or a reported nerve injury, must be documented in the patient's record and, per most facility policy, on a separate incident report. Documentation should include the observed signs, the time of onset, the actions taken, the patient's response, and any follow-up such as notifying the ordering provider or nursing staff. Thorough documentation protects continuity of the patient's care and creates an accurate record if symptoms are reported again later.

Chain of Custody

Certain specimens, including forensic samples, blood alcohol content testing, and workplace or legal drug screens, require a documented chain of custody: a signed, unbroken record of every person who collected, handled, transported, and received the specimen, with tamper-evident sealing. Any gap in that documented chain can make the specimen inadmissible as legal evidence, so every transfer must be logged and initialed.