Blood Gas Analysis Specimen Collection Methods and Some Factors Affecting Results
Blood Gas Analysis Blood Collection Kit with Rubber Stopper and Needle, Sterile Cotton Swabs, Amyl Iodine, Sterile Cotton Balls, and Treatment Tray. Users who are willing to prepare their own anticoagulant blood collection needles can prepare a heparin dilution with 0.9% NS 50ml + 2 sodium heparin injections (12,500U) for backup and good sterile storage. The following is the method of blood gas analysis specimen collection and some factors affecting the results that I brought for you, welcome to read.
I. Arterial blood gas specimen collection methods
1. Puncture methods
1.1 Preparation of supplies
Blood gas analysis blood collection kit (including rubber stopper and needles), sterile swabs, aneriodine, sterile cotton wool, and treatment trays. Users who are willing to prepare their own anticoagulant blood collection needles can prepare a heparin dilution solution with 0.9% NS50ml + 2 sodium heparin injections (12,500U) for spare use and aseptic storage. Before each blood gas draw, use a 2ml syringe to extract 2ml of heparin diluent, discard the heparin liquid after completely wetting the whole syringe, and the heparin liquid remaining in the dead space of the needle and head of the syringe can play an anticoagulant role. Less anticoagulant will make the blood agglutinate and block the flow path system of the blood gas analyzer, more anticoagulant will affect the results of blood gas and ion detection, and large doses of anticoagulant will seriously make the ionic calcium low and mislead the clinic.
1.2 Patient preparation
The patient should be in a natural state, and should rest for 15min after the activity, and oxygen should be stopped 30min before the blood draw. As the patient's understanding of the collection of arterial blood is small, easy to produce fear, the nurse should be targeted to do a good job of explaining the work of eliminating the patient's psychological concerns, stabilizing their emotions, to avoid various factors to breathe too much or hold their breath caused by the blood gas error.
1.3 Assessment of the patient's arteries and selection of blood vessels
Most of the arterial pulsation is obvious, good elasticity, easy to fix, puncture site without hard knots of the blood vessels, commonly used blood collection sites in order: radial artery, brachial artery, femoral artery and dorsalis pedis artery, radial artery is the most suitable for arterial puncture blood collection. Generally choose the radial artery, because here the artery is fixed, easy to expose, not subject to the position and the operation of the location of the limitations; followed by the choice of the femoral artery and brachial artery, the patient is easy to accept, and the success rate is high, it is not easy to accidentally enter the vein or accidentally stab the deep nerve.
1.3.1 Adults: puncture with heparinized glass syringe or disposable syringe, blood collection site preferred radial artery, followed by the femoral artery
1.3.2 Pediatrics:
1.3.2.1, preferred use of the superficial temporal artery or scalp arterioles, strict disinfection, with heparinized No. 5 scalp needle connected to the 2 ml syringe, waiting for the arterial blood to the syringe papilla When the arterial blood flow to the nipple of the syringe, immediately use a small hemostatic forceps to clamp the scalp needle plastic hose head and tail respectively (about 0.5 ml of blood), and then pull out the needle and immediately mixing to send for inspection.
1.3.2.2, with heparinized . Syringe puncture, blood collection site preferred pediatric radial artery, small infants can be used in the superficial temporal artery to take blood, after taking blood must be sealed.
1.3.2.3, because of technical constraints, can not be repeated arterial puncture, preterm infants and small infants can be in the heel of the heparinized capillary take arterialized capillary blood can also be. Arterialized capillary blood collection, with not more than 42 ~ 45 ℃ wet towel hot compresses the skin at the site of blood collection for 5 ~ 15 minutes, so that the blood increases, blood flow accelerated to achieve arterialization, and then puncture, puncture should be deep, so that the blood flow is rapid and automatic outflow, discard the first drop of blood, can not be extruded, heparinization of the capillary to absorb (it is recommended to use the manufacturers of supporting the provision of the special capillaries), suction full of must be sealed, mixing and immediately after the Sent for examination. The PO2 of insufficiently arterialized capillary blood is low, and the effect on the results of PH, PCO2 and HCO3- determination is not obvious.
1.4 Positioning
Traditionally, the site of blood sampling is the radial artery at the point of strongest pulsation. The blood sampling point is determined by the operator's feeling, because the radial artery is thin, the beating point is striated, and the beating can be touched in a longer section, the error of blood sampling position is larger. Yang Lanjie reported that the positioning is based on the radial styloid as the base point, move 1cm to the ulnar side, and then to the direction of the elbow to move up 0.5cm that is the point of entry, the undergraduate use of this method of positioning, the success rate of puncture is significantly improved.
1.5 Operation method
Assist the patient to take a comfortable position, expose and elevate the puncture site with a soft pillow. Strictly disinfect the puncture site, open the blood gas determination blood collection kit packaging, pull the live plug to 1cm, disinfect the operator's left hand index finger and middle finger, according to the above positioning method to find the most obvious arterial pulsation and fix the artery, the right hand holding the syringe, the needle and the skin was 45?to 90?piercing the artery, the needle into the wall of the vessel there is a kind of penetrating sensation, without the need to pull the plunger handle, the arterial blood automatically back to the blood, to the filling of the preset amount of blood, with a cotton ball pressed into the arterial blood, and the patient's body was then filled with the blood. After the blood volume, the needle is removed by pressing the eye of the needle at the puncture site with a cotton ball, and the patient is instructed to press for a period of not less than 5~10min, and then the needle is quickly stabbed into the rubber stopper, and then the specimen is immediately rubbed and mixed palmarly for at least 5s to prevent the specimen from coagulating, and then the label is attached and immediately sent to the hospital for examination.
2, post-collection treatment
Immediately after blood collection, the tip of the needle or capillary suction vessels at both ends of the rubber cap or rubber cement seal, to prevent air bubbles into the air, and immediately fully mixed to achieve the purpose of anticoagulation, and immediately sent to the test, from the collection of blood to the test should not be more than 20 minutes, so as not to metabolism of the blood cells oxygen depletion, so that the PO2 and PH value decreased PCO2 elevated. If you can't measure immediately, the blood gas specimen should be stored in a container at 2 to 8 degrees Celsius, but even then the time to be measured should not be more than 2 hours.
2. Factors affecting the results of blood gas analysis
1. What are the types of samples for blood gas analysis?
The sample types for blood gas analysis are arterial blood samples, venous blood samples, and capillary blood samples.
Arterial blood samples. Arterial blood is the most commonly used type of blood for blood gas analysis because it provides the best information on oxygen uptake and transport, and the information obtained is stable and does not vary depending on the sampling point.
Venous blood samples, which are generally not recommended for blood gas analysis because they are influenced by the state of peripheral circulation and cellular metabolism, are not useful for assessing oxygen status, but they can be used to reflect acid-base status (pH, pCO2, cHCO3) ctHb, FCOHb, FmetHb, FHbF, and ctBil.
Capillary blood samples, which can be used when circumstances do not permit the use of arterial blood, can be used when circumstances do not permit the use of capillary blood samples. Capillary blood samples can be used for analysis when the situation does not allow the use of arterial blood. sO2,pO2,FOHb,FHHb results are for reference only, and can better reflect the following parameters: ctHb, FCOHb, FMetHb, FHbF, ctBil.
2. How to choose the sampling point for blood gas analysis?
Arterial blood samples: The flexure artery is most commonly used because it is very superficial and easy to reach, there are no large veins in the vicinity, and there is very good collateral circulation in the ulnar artery, which makes it easy to sample, and it is generally pain insensitive if it does not touch the periosteum during the puncture process. A modified Allen?s test is performed prior to flexor artery sampling to determine the adequacy of collateral circulation. The brachial artery can be used but is not commonly used, due to the high risk of damaging the surroundings as it is not suitable for sampling because of its location. The femoral artery, although large and easy to puncture, has poor collateral circulation and is prone to inadvertent injury to the femoral vein and should be avoided in neonates and elderly patients.
Venous blood samples: the brachial vein is easy to sample.
Capillary blood samples: earlobes, fingertips, thumbs, and heels for blood sampling; patients should be older than six months when heels and thumbs are used.
3. How to choose an anticoagulant for blood gas analysis?
It is recommended that dry heparin with sodium or lithium be used as the preferred anticoagulant, and liquid heparin should be avoided to avoid dilution of the sample. The following concentrations of heparin are recommended based on sample type: test tube: 7-30 IU/mL blood, syringe: 50-500 IU/mL blood, capillary: 50-100 IU/mL blood. If electrolyte measurements are included, use electrolyte-balanced heparin to minimize heparin-induced bias in electrolyte measurements for optimal results.
4. How is the patient prepared for blood gas analysis sample collection?
The patient's respiratory status should be stable: the patient should be stabilized prior to sampling, with calm breathing and stable ventilation. Inform the patient of the sampling procedure to avoid unnecessary stress, which can cause hyperventilation. Hyperventilation is a major cause of blood gas errors and can increase alveolar ventilation, resulting in a decrease in pCO2, an increase in pH, and an increase in pO2.
5. How is the arterial catheter prepared for sample collection for blood gas analysis?
The flushing solution in the arterial catheter must be completely removed from the system to avoid diluting the blood sample.
6. How do I prepare a capillary blood sample for blood gas analysis?
The capillary sampling site should be fully arterialized, arterialized by applying heat or gently massaging it for 5-10 minutes, so that the blood vessels are locally dilated and congested, so that the capillaries are fully arterialized. If this requirement is not met, the blood sample will only represent the local tissues and will not respond to the patient's overall status. Otherwise, the pCO2 measurement may be low. In the case of patients with systolic blood pressure less than 95 mmHg, decreased cardiac output and vasoconstriction, or neonates within a few days of birth, capillary blood cannot be used.
7, blood gas analysis sample collection should pay attention to what?
It is important to note that blood sample testing should be performed by specialized personnel only, and to remember to handle blood samples and blood sample collection instruments with care. Use proper rubber gloves to prevent direct contact with the blood sample, and always use sterilization techniques to prevent infection of the sampling site.
8. How is arterial sampling performed for blood gas analysis?
Arterial sampling: arterial puncture, be careful not to confuse venous blood with arterial blood samples, arterial blood (due to high pressure) flows faster than venous blood and is lighter in color; remove air bubbles from it immediately; mix the sample with heparin immediately after sampling. For arterial catheters, inhale the sample slowly to avoid hemolysis; remove any air bubbles immediately; mix the sample with heparin immediately after sampling.
9. How do I collect a venous sample for blood gas analysis?
Venous samples: the hand and forearm should be immersed in 45OC water for 20 minutes to arterialize the venous blood in the area, and then blood should be drawn from the vein of the arm (or the back of the hand), but the blood should not be drawn with a pressurized band, and should only be sucked up slowly so as not to produce air bubbles. If a pressure band is used, the blood must be drawn in the first few seconds, and from time to time to flex the fingers or make a fist. Otherwise, the venous pO2 can be reduced, increasing the content of acidic products.
10, blood gas analysis how to capillary sampling?
For capillary sampling, use a lancet or other similar tool to puncture and the blood will flow out automatically without squeezing, discard the first drop of blood as it may contain tissue fluid. The first drop of blood is discarded as it may contain tissue fluid. The collection is started in the center of the second drop of blood to prevent air bubbles. It is forbidden to squeeze the blood collection point in order to avoid mixing some of the tissue fluid, which may cause deviation of the instrument measurement. It may also cause hemolysis of the sample (or part of it), resulting in high cK+ values. Sample analysis should be completed within 10 minutes. If storage is necessary, keep the sample at 0-40C for a maximum of 30 minutes. NOTE: Especially pO2 in measurements obtained with capillaries should be applied with caution.
11. How do I collect a mixed sample for blood gas analysis?
Mixing the sample: mix the blood with heparin immediately after collection to avoid clotting, which can clog the analyzer and cause unnecessary problems. To mix the sample, invert the sample and rotate it several times in your hand. Mixing wires or magnets may be used when mixing capillary tubes. Avoid mixing with too much force as this may cause hemolysis.
12. How do I collect a breath gas sample for blood gas analysis?
For a respiratory gas sample, the patient's respiratory gas is loaded into a Douglas bag, and a syringe is attached to the Douglas bag (minimum 20mL, containing a rubber tip). Fill, empty the syringe twice and then inject the sample, then seal the syringe using the rubber tip.
13. How are samples for blood gas analysis stored?
The sample should be used immediately at all times and preservation of the sample should be avoided as much as possible. If immediate measurement of the sample is not possible, store it at room temperature for no more than 10 minutes. If prolonged storage is required, store at 0-40C (32-390F) for up to 30 minutes. The following preservation methods are available: ice water (with crushed ice or a refrigerating substance attached) may be used to store samples. Samples should not be placed directly into ice to avoid lysis of blood cells due to ice crystallization in the sample. Samples should be placed horizontally to avoid mixing of samples. Note: Samples with high estimated partial pressures of oxygen should be measured as soon as possible; PH and blood gas values should not be measured if air bubbles are present in the capillaries.
14. How do I prepare a blood gas analysis sample for analysis?
Arterial puncture and arterial catheterization samples: PH and blood gas values should not be measured if there are air bubbles in the sample; shake and roll the sample in your hand several times to mix the sample thoroughly. Capillary samples: the sample should be mixed again before analysis, do not remove the mixing line before the sample is inhaled for measurement, slide the mixing line to the other end of the capillary tube where the sample is inhaled before inhalation, and remove the rubber tips at each end of the capillary tube.
15. What is the effect of air bubbles in the blood gas analysis sample on the test results?
Air bubbles should be removed from the sample prior to mixing and stirring. Air bubbles can lead to potential errors if they are present at 5% of the blood sample content, and the effect of air bubbles will increase with storage time and mixing and stirring. The partial pressure of oxygen in air is higher than that of arterial blood, and the partial pressure of carbon dioxide is lower than that of arterial blood. According to the law of gases, the higher partial pressure flows to the lower partial pressure, which changes both the pO2 and pCO2 in the blood and renders it worthless for measurement.
16. What are the causes of errors in blood gas analysis in the pre-analytical phase of blood sample analysis? How can they be prevented?
The presence of air bubbles in the sample affects the parameter pO2, which should be removed immediately. Sample precipitation, affecting the parameters Hct, pO2, pCO2, mix the sample before injecting into the analyzer. Hemolysis, affecting parameters cK+, cCa2+, should be avoided by avoiding vigorous mixing and by avoiding storage temperatures below 0°C. Metabolism, affecting parameters pO2, pCO2, cGlu, cCa2+, storage should be avoided, if storage is necessary please store at 0-4°C. Sample equipment structure, needle diameter too small easily cause hemolysis, affect the parameters cK+, cCa2+, should choose appropriate sampling equipment. Dilution caused by liquid heparin, affecting parameters electrolytes and metabolites, Hct, pCO2, should use dry heparin tablets. Heparin interventions affecting parameter electrolytes, especially cCa2+, electrolyte balanced heparin should be used. Arterial blood mixed with venous blood, affecting parameters pO2, sO2, standard sampling techniques should be used. Unstable patient status, affecting parameters pH and blood gases, should be ventilated and adjusted for 20 minutes before sampling, informing the patient of the sampling procedure. Leaking red blood cells, affecting the parameter cK+, should store the sample at a temperature of 0-4°C for a maximum of 30 minutes. Placement in sunlight or other light, affecting the parameter ctBil, should allow the sample to be placed out of the light and measured as soon as possible, and the light should be turned off before blood collection in patients undergoing phototherapy.
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