Week 1 Flashcards
4 qualities in a good venepuncture vein
- Well anchored to the skin
- Shows elasticity
- Large enough for good blood flow
- Easily visible
Pre analytical factors
Test ordering system, patient ID matching sample, patient preparation, specimen transport
Analytical factors
Calibration, reagents, QC, equipment maintenance
Post analytical factors
Result reporting, turn around time
Non analytical factors
Staff training, lab policies, health and safety
Best vein for venepuncture and why
Median cubital vein as it is large and well anchored, less painful and likely to bruise
Second best venepuncture vein and why
Cephalic vein
May be more painful, not as well anchored but large
3rd best venepuncture vein
Easy to palpate but more painful and near brachial artery/nerve which could cause pain and you don’t want artery blood
Secondary venepuncture sites
Hands and feet is the last resort
What are some inappropriate venepuncture sites
Edematous/lympodema sites
Bruised and scarred areas
Arms with grafts/fistula
Inner wrist
Diabetic feet/ anyone with peripheral vascular disease
Arm with IV in, use the other arm or hand
Thrombosed veins
Types of needles
Flashback- to see if you’re in a vein
Butterfly - good for training, less pain
Hand washing precaution
Assume all substances from the body are dangerous
Wash hands before and after touching patients/doing a procedure and after touching surroundings near a patient
Procedure before sticking the needle in
Wash hands
Greet patient and check ID
Position patient
Consider the vein using a torniquet
Alcohol wipe
Order of draw saying
Stop light red, green light go
Order of draw colour order
Light blue
Red
Gold
Green
Light green
Lavender
Grey
Light blue tube
First in order of draw as it uses a weak anticoagulant reversible
Na citrate
Looking at coagulation and platelets
Red tube
Second in draw order
Plain tube
No anticoagulants as you want the blood to clot
Gold tube
SST
3rd in order
Serum, no anticoagulants
Light green
5th
PST plasma
Non coagulating
Green tube
4TH
LiHep
Non coagulating plasma
Lavender tube
6th
EDTA
Whole blood used for blood films and HbAc1, full blood counts
Grey tube
Last in order of draw
NaF or F oxalate
Plasma
For glucose
Pink tube
Just before grey
EDTA for blood banks only
Tourniquet uses
Make veins easier to feel and locate
10cm above vein
Stays on for 1 min at a time
What happens if tourniquet for longer than a min
Haemo concentration so increase in proteins/albumin/Ca
Water balance changes
Haemolysis
What do you clean the venepuncture surface/ features
70% alcohol
Circular motion, wait 30sec to dry
Underfilling tube leads to
Excessive additive
Not enough blood for testing
Need to recollect
Overfilling tubes results in /common with what type
Not enough additive in tube
Common with syringe draws
When do you remove the needle in regards to tourniquet
After the tourniquet is released
What do you do after removing the needle
Dispose it first
Apply pressure second
Should you bend arm after venepuncture
No
Do not wipe either
What to do with tubes after needle is disposed of
Gently invert
Label patient info
Then give plaster
How many times do you invert a citrate tube
3-4x
How many times do you invert every tube but citrate
8-10x
What is phlebotomy syncope
1% of procedures
Vasovagal response - BV dilate, heart rate slows down, BP drops so less blood reaches brain
Fainting after procedure
What to do if patient feels faint
Stop procedure
Call for assistance
Remove needle and tourniquet
Apply pressure to wound
Head between knees if seated
Elevate legs if on back
111 if not breathing
Cold compress to back of neck
Stay with patient for 15-30 mins
No vehicle operation 30 mins after fainting
What are influencing factors
Cause a true change in analyse quantity
Patient related not method
What are interfering factors
Cause a false change in analyse quantity
Dependent on method more so
What are some modifiable influencing factors
Fasting state
Exercise before coming in
Vein or artery blood
Posture
Tourniquet
Treatments
What are some unmodifiable influencing factors
Sex, race, gender
Medications
Disease state
Pregnancy
Period
Mode of baby delivery
Altitude
What are some endogenous interfering factors
Tourniquet left on too long = haemoconcentration
Lipaemia
Icterus
Paraproteins
Pathologies
List exogenous interfering factors
Shaking tube
Wrong tube additive
Didn’t invert
In vitro haemolysis from tube temp
Drugs
Tracer dye
Canula additives
Tube additives
Clot in tube
How to reduce influencing and interfering factors
Standardise methods
Beer lambert law
For spectrophotometry
Small particle scattering
Not all light is absorbed
Symmetrical scattering
Less than 5% of wavelength
Large particle scattering
Due to constructive and destructive interferences
Forward scattering increases
Backwards scattering decreases so asymmetrical
What is turbidimetry measuring and what type of particles is it better for
Decrease in transmitted light is measured
Better for larger particles and higher concentrations
Detector placement in turbidity vs nephelometry
In turbidity the detector is in line with the source
In neph the detector is at a 90 angle to the source
What is nephelometry measuring
Scattered light
Better for smaller particles at lower concentrations
More scattered =less absorbed
What is haemolysis
Disruption in blood cell membrane causing lysis of RBC
What is the most common preanalytical error in chem path tests
Haemolysis
In vivid haemolysis occurs how/ what proteins does this effect
Due to pathology
Less serum haptoglobin
Increased urine Hb
Sample reflects patient so it’s fine
In vitro haemolysis cause
Cells damaged via
Vein trauma
Needle size
Syringe collection too fast
IV lines
Shaking tubing
Temp
May need to redraw
How does haemolysis cause spectrophotometric interference
Causes peaks at 415, 540, 570nm
False analyte conc
Haemolysis causes interference by increasing what analyte conc
LDH
Pi
AST
K+
In plasma
What does haemolysis do to sample dilution
Effects analytes with greater extracellular conc like albumin, Ana and bilirubin
How does haemolysis affect assays with an example
It competes for binding sites, inhibit reactions
Free Hb may start binding
When is lipaemia found the most
Lipid disorders
Acute pancreatitis
Drugs some
Post prandial samples
Had a fatty meal
What type of fats contribute to lipaemia
Lipoproteins chylomicrons
VLDL
How to reduce lipaemia in blood samples
Fasting before the sample is taken
Lipid clearing agents
High speed centrifugation so lipids go to the top
How does lipaemia cause spectrophotometric interference
Absorption decreases between 300-700n
Light scattering interferes with turbidity and nephelometry
What is the volume depletion in lipaemia
Lipid droplets take up volume in aspirated sample
Falsely decrease concentration of analyte of interest
Random problems with lipaemia
Abnormal peaks in electrophoresis
Masking of binding sites
Partitioning of sample hard for automatic analyser
What is icterus
High bilirubin levels in plasma/serum
When is icterus samples seen
Liver disease
Cancer
Neonates
How does icterus interfere
Spec interference at 400-540nm
Chemical interference with hydrogen peroxide for cholesterol/glucose/triglyceride
What does automated serum indices measure
Haemolysis
Lipaemia
Icterus
How does automated serum indices work
Sample blanked at absorbance maxima of Hb/lipids/bilirubin and interference is graded and unsuitable samples are flagged
What is bichromatic analysis
Measures two wavelengths
Measures absorbance at points where no change in absorbance occurs and is used as a reference point
Example of bichromatic analysis with equations
Want to measure chromogen but bilirubin will interfere
Primary absorbance - bilirubin absorbance = absorbance from chromogen
Abs at 2nd - 1st = abs from interference
