Preanalytical Errors - Questions & Answers

Heparin-induced bias

What are the potential risks of using liquid non-electrolyte-balanced heparin? 
Using liquid heparin leads to dilutional effects, where the higher the diluent volume, the higher the dilutional effect. Non-electrolyte balanced heparin will bind blood cations, like cNa⁺, cK⁺, and particularly cCa²⁺. 

What cations usually measured in BG analysis is heparin known to bind to?
Heparin is a polysaccharide with negatively charged sulfate (-OSO₃^⁻) and carboxyl (-COO^⁻) groups, at physiological pH. Thus, it attracts and binds blood cations like Na⁺, K⁺, and Ca²⁺. 

In blood gas analysis, what form and properties are recommended for heparin?
Dry (lyophilized) heparin does not dilute the sample. Electrolyte-balanced heparin contains an appropriate concentration of electrolytes (like Na⁺, K⁺, Ca²⁺) preventing it from creating negative or positive bias on blood electrolytes. 

What can cause falsely low cCa2+ in blood gas test results?
cCa²⁺ is particularly vulnerable to heparin-induced bias from cation-binding effect. Electrolyte-balanced heparin contains an appropriate concentration of electrolytes (like Na⁺, K⁺, Ca²⁺) preventing it from creating negative or positive bias on blood electrolytes.

Radiometer's syringes and capillaries contain dry electrolyte-balanced heparin that virtually eliminates the measurement bias on Na⁺, K⁺, and Ca²⁺. 

 

Patient sample mix-up

What potential risks could patient sample mix-up lead to?
Mixing-up patient results can have devastating consequences on the diagnostics and treatment decisions, because the results show the metabolic snapshot of a different patient.

How can you avoid patient-sample mix-up?
It is a good practice to label the sample with at least two patient identifiers, and make sure the sample has been labeled before leaving patient's side. 

Radiometer's 1st Automatic solution allows you to register patient samples at the bedside by linking the patient, operator and sampler IDs. The pre-barcoded safePICO syringes offer a unique identifier thus minimizing the risk of accidental patient sample mix-up. 


How many identifiers are recommended for a patient sample?
It is a good practice to label the sample with at least two patient identifiers, for example: patient ID, date of birth, medical record number, etc.

When is it recommended to label the blood gas sample?
It is good practice to label the sample with at least two patient identifiers. Make sure to label the sample before leaving the patient's side.

Radiometer's 1st Automatic solution allows you to register patient samples at the bedside by linking the patient, operator and sampler IDs. The linked data is transmitted to your Information System (HIS/LIS/EMR), and is automatically available on the Radiometer's analyzer, once the sample is scanned.

 

Contamination by venous blood

What parameters can be affected by the contamination of an arterial blood gas sample with venous blood?
Venous blood in comparison to arterial has a lower pH, pO₂ and oxygen saturation, but higher carbon dioxide content. 

What type of needles could minimize the risk of accidental penetration of veins?
The tip of short beveled needles is cut at a less acute angle, meaning the tip is shorter and advances more bluntly. This increases the likelihood that the needle will lie completely within the arterial lumen.

The short-beveled needles of Radiometer's syringes increase the likelihood of the needle lying entirely within the arterial lumen. While self-fill syringes don’t fill or fill more slowly in case of accidental venous puncture.  

Why do self-fill syringes fill more slowly when puncturing a vein?
When using self-fill syringes, the operator sets the plunger to the desired sample volume. The arterial blood pressure fills the syringe, displacing the air through the holes in the plunger, which seal spontaneously when the syringe is filled. Veins lack the blood pressure needed for effective filling.

Radiometer's self-fill syringes don’t fill or fill more slowly in case of accidental venous puncture. 

 

Contamination by flush solution

What parameters can be affected by the contamination of blood by flush solution if normal saline is used?
Normal saline content - cNa⁺ 154 mmol/L, cCl^- 154 mmol/L, both higher than the concentrations of Na⁺ and Cl^- in blood plasma. At the same time, flush solution will dilute the plasma influencing all parameters, the dilutional effect is directly proportional to the amount of the flush solution mixed with the blood.

What precautions should be taken during sample collection from an indwelling catheter line?
Remove a sufficient amount of flush solution, exceeding the dead space volume of the catheter and line significantly. Follow the manufacturer’s recommendations for intravascular line products.

What kind of blood gas samples collected from an indwelling catheter line can be contaminated by flush solution?
Blood collected from both arterial and venous indwelling catheter lines can be affected if not enough flush solution is removed before collecting the sample. Remove a sufficient amount of flush solution exceeding the dead space volume significantly. Follow the manufacturer’s recommendations for intravascular line products.

Radiometer’s solution offers the tools to optimize quality in the preanalytical phase of blood gas testing.

 

Contamination by tissue fluid

What parameters can be affected by the contamination of blood by tissue fluid when collecting a capillary sample applying pressure to the soft tissues?
Contamination of blood by tissue fluid (interstitial/extracellular fluid) and excessive admixture of venous blood can lead to various biases on the results like: pO₂ and sO₂ – decrease; pH – mild decrease; pCO₂ – mild increase; ctHb – mild decrease. 

How can you avoid the contamination of blood by tissue fluid when collecting a capillary sample?
Good peripheral circulation will allow the spontaneous collection of the capillary blood sample without applying pressure. In patients with compromised circulation, consider an alternative sampling technique.

What kind of clinical conditions need to be met to facilitate collection of capillary blood sample?
Good peripheral circulation will allow the collection of the capillary sample without applying pressure. With impaired peripheral circulation, capillary oxygen values cannot represent arterial values, and the need to apply pressure or milking can result in contamination by tissue fluid.

Simplify capillary blood collection with a precision tube and BG analyzer for small volumes, ensuring accuracy with minimal blood. For example, ABL90 FLEX PLUS with MicroMode measures 17 parameters in 45 μL of blood.

Air contamination

What parameters can be affected if room air is not removed from the blood sample immediately after collection?
Due to the gradients in the partial pressures of oxygen and carbon dioxide, equilibration between the blood sample and ambient air can lead to biases on pO₂, pCO₂, pH and sO₂. 

What sequence of actions should be followed to prevent air contamination of blood gas sample collected in a syringe?
Blood should be collected under anaerobic conditions. If air bubbles are present in the sample, they must be removed by gauzing the sample into a clean tissue. The sample must be sealed right after.

Why is it important to seal the sample right after removing air from it?
It is important to seal the sample right after removing air from it in order to stop any further possible gas exchange between the sample and the ambient air. Due to the differences in the partial pressures of oxygen and carbon dioxide, equilibration between the blood sample and ambient air can lead to biases on pO₂, pCO₂, pH and sO₂. 

Radiometer's vented safeTIPCAP allows sealing the sample and removing room air from the blood sample without the need to spill blood. The safeTIPCAP also stays on during sample aspiration by the analyzer.

Clotting

What potential risks can a clotted sample lead to?
Clots of various sizes can either block the analysis chamber or lodge on and/or next to sensors. This can lead to analyzer downtime and biased results.

What factors are important for heparin to prevent clotting of blood gas sample?
Adequate heparin concentration in a blood sample prevents clotting. Therefore, it’s essential to use a syringe or capillary tube containing enough heparin and to mix the sample immediately after collecting the blood and expelling air, ensuring proper dissolution and distribution.

What is the recommended anticoagulant for blood gas samples?
Dry electrolyte-balanced heparin is the recommended anticoagulant for blood gas analysis.

Radiometer's syringes and capillaries contain dry electrolyte-balanced heparin in a sufficient concentration, reducing the risk of clots. Additionally, safePICO syringes contain a special magnetic mixing ball that facilitates the dissolution of heparin.

Cold exposure effect

What parameters can be affected by exposing blood samples in plastic syringes or capillary tubes to cold?
Plastic is not impermeable to gases, and exposure to cold temperatures accelerates the diffusion of O₂ and CO₂ between the blood sample and ambient air. Cold also inhibits Na⁺/K⁺-ATPase, causing an increase in plasma cK⁺ and a decrease in plasma cNa⁺.  

Are syringes made of plastic permeable to gases?
Plastic is not impermeable to gases, and exposure to cold temperatures accelerates the diffusion of O₂ and CO₂ between the blood sample and ambient air.  

Should plastic syringes be cooled on ice slurry (stored in a cold environment) prior to analysis?
Plastic is not impermeable to gases, and exposure to cold temperatures accelerates the diffusion of O₂ and CO₂ between the blood sample and ambient air. Cold also inhibits Na⁺/K⁺-ATPase, causing an increase in plasma cK⁺ and a decrease in plasma cNa⁺. 

According to CLSI (Clinical & Laboratory Standards Institute), samples in plastic syringes should be handled at room temperature and analyzed immediately or as soon as possible, within 30 minutes of collection. Radiometer's point-of-care blood gas testing solution helps keep the preanalytical phase short and avoid the need for cooling the sample, by placing the blood gas analyzer closer to the patient’s bedside.

Ongoing metabolic effect

What parameters become affected over time due to prolonged storage of a blood gas sample?
Blood is a living tissue whose cells continue metabolizing even after blood collection. Cells continue to use oxygen and glucose to produce carbon dioxide and lactate. The accumulation of CO₂ and lactate leads to changes in the pH. Moreover, with time Ca²⁺ bound to protein is displaced by hydrogen ions. 

What is the recommended time from sample collection to analysis?
The sample should be analyzed immediately or as soon as possible, within 30 minutes of collection.

How fast would you recommend to measure BG sample obtained from a patient with leukemia and extremely high WBC count?
In the presence of an elevated leukocyte count oxygen and glucose are metabolized fast. Thus, the sample should be analyzed immediately.

Radiometer's 1st Automatic solution can timestamp the sample with the time of collection and measurement.  It will flag the sample if more than 30 min have elapsed.

Inhomogeneous sample

How can the homogeneity of blood sample be restored prior to analysis?
CLSI (Clinical & Laboratory Standards Institute) suggests to gently rotate the sample between your hands through two axes for at least 1 minute. Longer mixing intervals should be considered if samples sit for longer.

For how long is it recommended by CLSI to mix the blood sample prior to analysis?
CLSI suggests gently rotating the sample between your hands through two axes for at least one minute. Longer mixing intervals should be considered if samples sit for longer.

Vigorous manual mixing can effectively restore homogeneity of blood sample. Why should it be avoided?
Harsh vigorous sample mixing can rupture red blood cells, causing the cells contents to spill and mix with blood plasma, affecting the concentration of different analytes.

Which parameters are affected by inhomogeneity of the blood sample?
Total hemoglobin is particularly vulnerable to inhomogeneity.  Resulting value depends on the fraction of the blood sample reaching the oximeter where hemoglobin is measured. If, for example, a sedimented part of the sample is analyzed, hemoglobin will be measured falsely high.

Radiometer's safePICO syringes contain a special magnetic mixing ball, that is activated in the mixing unit of the analyzer. Automatic mixing improves the quality of total hemoglobin results, standardizes your workflow and achieves a homogeneous sample in just 8 seconds.

Hemolysis

Which parameters are affected by hemolysis?
Hemolysis affects mostly the blood electrolytes. The concentrations of the Na⁺, K⁺, and Ca²⁺ inside the red blood cells (RBCs) are different from the ones in blood plasma. When the RBCs' cellular membrane is broken due to hemolysis, the contents of the cell are mixing with plasma, thus changing the overall concentration of plasma components.  

Which factors can potentially lead to hemolysis? 
Many factors lead to hemolysis, thus it is important to be careful when performing any actions during the preanalytical phase.

What precautions, taken during arterial puncture, can also mitigate the risk of hemolysis?
Using an aspirating syringe can create excessive vacuum, potentially damaging red blood cell membranes. In contrast, self-fill syringes eliminate this risk by filling without vacuum. 

Many factors lead to hemolysis, thus it is important to be careful when performing any actions during the preanalytical phase. Radiometer’s solution offers the tools to optimize quality in the preanalytical phase of blood gas testing, helping to minimize the risk of hemolysis.

Operator hazard

What operator risks are associated with the preanalytical phase of blood gas testing?
The most common risks associated with the preanalytical phase of blood gas testing are needlestick injuries, unwanted contact with patient blood, and the risk of bloodborne infections. 

What elements are effective in ensuring operator safety during preanalytical phase of blood gas testing?
A combination of standardized policy, training and the availability of appropriate accessories with safety features can ensure the operator's safety throughout the preanalytical stage of blood gas testing. 

Can products ensure operator safety by reducing the risk of needlestick injuries?
Needle shield attachments are features on syringes that enable safe needle removal or sheathing. 

What can help an operator reduce the risk of unwanted contact with a patient's blood during blood gas testing?
A vented tip cap allows you to seal the sample before expelling room air, meaning no operator contact with blood. The usual method is to gauze the sample into a clean tissue. 

The features of Radiometer's syringes including the needle cube, the needle shield device, the tip cap and the vented safeTIPCAP are designed to maximize operator safety throughout the preanalytical phase of blood gas testing.