ECG and Phlebotomy Skills
ECG basics
Standard paper speed is 25 mm per second with calibration at 10 mm per millivolt, so one small box is 0.04 second and one large box is 0.2 second. Apply electrodes to clean, dry skin without lotion, avoiding bony prominences and areas of heavy muscle movement. Know three artifacts and their fixes: muscle tremor (warm and calm the patient, reposition), baseline wander (movement or breathing; secure cables), and 60-cycle interference (check connections, move away from electrical equipment). Lethal rhythms such as ventricular fibrillation, pulseless ventricular tachycardia, and asystole require an immediate call for help; never leave the patient alone.
Phlebotomy order of draw
Blood culture or sterile tubes first, then light blue (sodium citrate, coagulation), then serum tubes (red or gold/SST), then green (heparin), then lavender (EDTA), then gray (oxalate/fluoride). Additive carryover distorts results, so the sequence matters. Capillary collections differ, with EDTA tubes first.
Technique traps
Leave the tourniquet on no more than one minute; prolonged tourniquet time causes hemoconcentration and falsely high potassium. Cleanse with 70 percent alcohol in concentric circles from the site outward and let it dry. Insert bevel up at 15 to 30 degrees. Prefer the median cubital vein, then cephalic, then basilic. Avoid arms with IVs, fistulas, mastectomy, or lymphedema. Hemolysis falsely raises potassium and LDH, so avoid shaking tubes and use an appropriate needle size.
Worked example
A specimen arrives grossly hemolyzed. Rule of thumb: re-collect rather than report, because hemolysis falsely elevates potassium, LDH, and AST.