Blood sampling from a vein – how to prepare, sampling technique and test rates

1 49 - 15Most of the pathologies for which people are forced to consult a doctor require additional analyzes. One of the most common is taking blood from a vein for examination. This analysis allows you to identify many indicators that help in establishing a diagnosis or correcting treatment.

But it is important to correctly donate blood from a vein for analysis. This is not as simple a procedure as examining capillary blood from a finger. A laboratory assistant can cope with it, or even a person himself can learn how to do it on his own when it comes to patients with diabetes mellitus.

The study of venous blood requires qualifications:

  • Nurse,
  • Paramedic,
  • Doctor.

Preparing for the procedure

Responsible attitude to the moment of donating venous blood means properly preparing for the analysis. If some of the rules are not followed, then the research results will be incorrect. This will affect the correct diagnosis and treatment.

Conditions for preparing for a blood test:

  • It is undesirable to engage in excessive physical activity the day before,
  • On the day before the study, you should not eat too spicy, fatty foods, drink alcohol,
  • On the day of the test, do not eat, smoke or drink anything other than water,
  • Some of the medications taken may affect the test results, they must be temporarily canceled.

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The location of the veins on the arm

Blood counts depend not only on the presence or absence of the disease. The human body is sensitive to any changes.

Often, the results of the study can be influenced by several factors that are independent of the person:

  • Hormonal cyclical changes in a woman’s body – menstruation, ovulation, menopause,
  • Stress, psycho-emotional stress, including those associated with the blood sampling procedure,
  • Other studies conducted the day before.

3 44 - 19If a clinical or biochemical blood test reveals a change that does not correspond to the person’s clinical symptoms, then it makes sense to repeat the analysis. It is likely that it was the failure to follow the rules of preparation for the analysis that led to such a result. Also, laboratory error or poor quality reagents cannot be ruled out.

Blood collection technique

At the moment when blood is taken, a person can sit or lie down, depending on his condition. If he is too nervous about an upcoming study, then a 15-minute rest should be given to calm down. The presence of signs of alcohol intoxication is a recommendation for transferring the analysis to the next day.

It is most convenient and preferable to take blood from the veins of the forearm. Here they are located superficially, are visible under the skin and move slightly.

The most commonly used:

  • Elbow,
  • Median superficial
  • Beam,
  • Median vein of the elbow,
  • External superficial vein.

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Blood sampling from a vein

Of these veins, the median elbow vein and the external superficial vein are best suited. They are fixed by tendons in the elbow bend area, therefore they are inactive. A vein that is too mobile during the injection can slip away from the needle to the side.

In obese people, the veins may be almost invisible. In this case, it is convenient to use the vessels in the back of the hand. They are always more noticeable, but there are more pain receptors, blood sampling will be more painful. Also, these veins are more mobile, which will require better fixation of the vessel during blood collection. It doesn’t matter which arm veins are used.

When taking peripheral blood from a vein, a strict algorithm and rules for delivery are observed. Disposable gloves should be worn by the healthcare professional collecting blood. First, a preliminary injection site is determined, a vein is selected.

A tourniquet is applied to the shoulder. The person is asked to make several movements with the hand – this will allow the veins to fill more with blood. The nurse carefully probes the vein from which the blood will be drawn.

  • The place of the bend of the elbow is alternately processed with two balls of alcohol. This is necessary to comply with the rules of asepsis. After treatment, the vein is no longer palpable.
  • 2 50 - 23The needle is inserted at an angle of 45-50 degrees to the skin. Be sure to insert it with an oblique cut upward – this will allow you to pierce the vein wall quickly and accurately.
  • After the injection, the direction of the needle changes, it becomes parallel to the vein. The needle is inserted into the lumen of the vessel by about a third.
  • The tourniquet is removed after insertion, the patient’s hand should lie relaxed and motionless.
  • After taking the required amount of biomaterial with a syringe – blood, the injection site is pressed with a cotton ball with an antiseptic, the needle is removed.
  • The arm should be bent at the elbow and firmly applied to the blood sampling site to avoid bruising.

In many medical centers and laboratories today, vacuum tubes are used. This is more convenient than drawing blood with a syringe. Vacuum tubes are available in the form of ready-made kits, depending on what the blood is taken for.

The kit includes a test tube and a fine needle. After puncture of the vein, it is not required to substitute the tube and control the amount of blood. The tube itself sucks in as much biomaterial as required.

Normal analysis values ​​and reasons for change (table)

povyshennyj uroven eritrotsitov v krovi u muzhchin - 25The direction with which the person came is attached to the test tube with blood. This can be a referral for a general blood test or biochemical research, with certain indicators. There are normal values ​​for each indicator.

They can increase or decrease, depending on the pathology:

IndexNormal valueIncreaseReduction
Hemoglobin120-170 g/lToo thick blood – erythrocytosis, smoking, dehydration due to diarrhea, vomiting, overheating, blood transfusionAnemia – iron deficiency, due to bleeding – post-hemorrhagic, due to lack of iron from food, excessive need for iron in pregnant women, in children
Erythrocytes3,7-5,5 * 1012/lSmoking, chronic obstructive pulmonary disease, primary and secondary erythrocytosis, climbing mountains, blood clots due to dehydration, compensatory in athletesIron deficiency anemia: post-hemorrhagic, due to a lack of iron in food, vegetarianism, a great need for iron in pregnant women and children
leukocytes4,5-9,5 * 109/lInfectious pathologies: bacterial, viral, fungal,Acute and chronic leukemia, severe infections, secondary and primary immunodeficiencies – HIV, Di Giorgi syndrome, radiation sickness, heavy metal intoxication, taking cytostatics
overheating, stress, acute and chronic leukemia,
taking certain medications,
vaccination
Platelets150-400 * 109/lCongenital thrombophiliaThrombocytopenia associated with tumors of the blood system, radiation sickness, exposure to toxins, cytostatics,
removed spleenhypersplenism – increased spleen function
oncological processes,
autoimmune diseases
Erythrocyte sedimentation rate0-20 mm/hInfections: viral, bacterial, mixed,rate
systemic diseases – rheumatoid arthritis, lupus,
oncological diseases,
thickening of the blood due to dehydration
Total protein67-88 g/lmultiple myeloma,Exhaustion – cachexia, nephrotic syndrome – loss of protein in the urine, chronic diarrheal syndrome, malabsorption syndrome
thickening of blood
autoimmune pathologies
Total cholesterolUp to 5 mmol/LAtherosclerosis: ischemic heart disease, cerebral ischemia, familial hypercholesterolemia,exhaustion
chronic kidney disease
ALT, ASTUp to 35 IU/LHepatitis: toxic, infectious, idiopathic,rate
cirrhosis of the liver,
myocardial infarction,
poisoning,
overdose of certain medications,
taking statins, oral contraceptives, antibiotics,
irrational diet,
fatty hepatosis
Alkaline phosphatase30-120 U/lAcute and chronic pancreatitisrate
Urea2,8-7,6 mmol/lRenal failure, fever, sepsis, dehydration, intestinal obstructionLiver pathology
CreatinineUp to 100 μmol/LChronic kidney disease due to glomerulonephritis, amyloidosis, pyelonephritis, urolithiasis, etc.Liver pathology
prolonged fasting,
excessive physical activity,
Bilirubin5,2-17 μmol/lLiver damage: infectious, toxic hepatitis, cirrhosis, gallstone disease, Gilbert’s syndromerate
Glucose2,5-6,0 mmol/lDiabetes mellitus, impaired glucose tolerance, blood donation after mealsInsulinoma, pheochromocytoma, fasting, overdose of hypoglycemic drugs or insulin

Complications after donating blood from a vein

During the analysis, it is important to follow the rules of antiseptics. But often the infection still enters the body.

Contribute to this:

  • Weakened immunity
  • Cold,
  • Immunodeficiencies
  • Vascular wall defects
  • Failure to comply with antiseptic rules.

Then, a few hours after the injection, the injection site becomes infected. Phlebitis – inflammation of a section of a vein or thrombophlebitis – may develop when the inflamed vein becomes thrombosed.

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Without treatment, thrombophlebitis will spread up the vein, causing more and more extensive damage. Phlegmon, an inflammation of the soft tissues, may develop. Cellulitis appears when an infection from a vein spreads to the surrounding muscles and fatty tissue. This is a dangerous infectious complication that requires immediate attention.

Phlegmon and thrombophlebitis are fraught with the development of sepsis – blood poisoning. This is a common infection where bacteria proliferate in the bloodstream. Sepsis quickly leads to liver, kidney, and lung failure. Without timely treatment, sepsis leads to death.

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Tatyana Jakowenko

Editor-in-chief of the Detonic online magazine, cardiologist Yakovenko-Plahotnaya Tatyana. Author of more than 950 scientific articles, including in foreign medical journals. He has been working as a cardiologist in a clinical hospital for over 12 years. He owns modern methods of diagnosis and treatment of cardiovascular diseases and implements them in his professional activities. For example, it uses methods of resuscitation of the heart, decoding of ECG, functional tests, cyclic ergometry and knows echocardiography very well.

For 10 years, she has been an active participant in numerous medical symposia and workshops for doctors - families, therapists and cardiologists. He has many publications on a healthy lifestyle, diagnosis and treatment of heart and vascular diseases.

He regularly monitors new publications of European and American cardiology journals, writes scientific articles, prepares reports at scientific conferences and participates in European cardiology congresses.

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