اخذ عينات الدم

Definition venepuncture (also known as phlebotomy, venesection, blood draw, drawing blood or taking blood) is the process of obtaining a sample of venous blood. Steps of venepuncture Preparation for blood collection هده الخطوه هامه جدا فى سحب العينه لانها سوف يتحدد على اساسها العديد من الامور التى ستؤثر فى طريقه السحب او كميه الدم المطلوبه و نوعيه الانابيب التى سيوضع عليها الدم و ترتيب مراحل هده الخطوه يكون كما يلي: Read the request of the patient Verify the patient's condition. Fasting, dietary restrictions, timing of the test, and medical treatment Estimate the blood volume to take Prepare the suitable tubes for each test ملحوظه: تحضير الانابيب قبل سحب العينه هام جدا خاصه فى تحاليل التجلط مثل البروثرومبين لان التأخير فى تحضير الانبوبه بعد سحب العينه قد يؤدى الى تجلط الدم قبل وضعه فى الانابيب. شروط خاصه لعينات الدم اولا: عينات يشترط فيها الصيام: 1. عينات الدهون تشترط صيام 12 ساعه على الاقل 2. عينه السكر الصائم تشترط صيام من 6 -8 ساعات و يجب الا تزيد عن ذلك ختى لا يقل مستوى السكر فى الدم و يكون التشخيص غير دقيق 3. بعض التحاليل الخرى الخاصه بمرض السكر يشترط فيها الصيام مثل insulin و c-peptide 4. تحليل هرمون الكالستونين (calcitonin) فى الدم يشترط فيه الصيام ثانيا: عينات يقضل فيها الصيام: يفضل صيام من 6 -8 ساعات فى التحاليل الاتيه : ESR, uric acid, urea ثالثا: عينات تؤخد فى اوقات محدده: 1. تحاليل الهرونات الانثويه تؤخد فى مواعيد محدده اثناء الدوره الشهريه 2. عينه الدم لتحليل ACTH , Cortisol لابد ان تؤخد فى وقت محدد 9 صباحا و 9 مساء Reassuring the patient You must get the patient confidence before sampling ملحوظه: لابد من اكتساب ثقه المريض قبل البدء فى سحب العينه خاصه فى عينات الاطفال و الثقه ليست فى الاخصائى الدى سيسحب العينه فقط بل فى عمليه السحب نفسها و انها لن تسبب ضرر او الم للمريض . Note: Stress cause high glucose and enzyme activity due to adrenal stimulation Positioning the patient The patient should sit Comfortable in a chair, lie down or sit up in bed. Patients should not stand or sit on high stools because of possibility of fainting. The patient should sit 15 min in his place. Why position is important? Due to position change may cause increase as much as 13% in the concentration of plasma proteins and protein bound constituents due to redistribution of fluids in the EC space. The patient hand extend from shoulder to wrist The patient arm should not bent at elbow If the patient cannot hold the arm in position, a pillow may be used for additional support. If the patient lies down arm should extend and supported. Choosing the arm Note: Right arm is better due to working with right hand make its veins larger and fuller Avoid the following: Arm with burn area Arm with hematoma(may cause erroneous test results. If another site is not available, collect the specimen distal to the hematoma) Arm with scaring (it is difficult to puncture the scar tissue and obtain a specimen) Arm with IV line Arm with recently injected or withdrawn syringe Arm that cannot be extended well Edematous extremities (tissue fluid accumulation alters test results). Arm with sclerosed or occluded Veins (this results from frequent puncture leading to scarring, or inflammed veins, these veins are hard when palpated and generally have minimal flow.) Arm on the side of a previous mastectomy why? A patient with a mastectomy may have lymphostasis on the effected side, making the patient highly susceptiple to infections , also lymphostasis affect blood composition and test results. Note: Patients with bilateral mastectomies should have venipuncture performed on the hand. Collection of blood sample Vein selection: The vein selected should be large, readily accessible, and sufficiently close to the surface to be seen and palpated. For adults: Although the larger and fuller median cubital and cephalic veins of the arm are used most frequently, the basilic vein on the dorsum of the arm or dorsal hand veins are also acceptable for venipuncture. Foot veins are a last resort because of the higher probability of complications. Note: the elbow area does not have many nerves so this is a good site Note: Avoid using dorsal hand veins in diabetics and patients with poor circulation For babies: Jugular, scalp veins or femoral vein can be used. If the vein is difficult to be seen: For most people, venipuncture is quick, easy, and relatively painless. But some people, however, have veins that are quite small or difficult to access. The following methods can be done to help: Ask the patient to make fist this helps make the vein more prominent. Apply tourniquet to distend the vein You can force blood into the vein by massaging the arm from wrist to elbow Palpate and trace the path of veins with the index finger. Feel vein using the tip of finger and think in four things during feeling the vein Bounce, direction, depth and size of needle Lower the extremity over the bedside to allow the veins to fill. Apply a warm, damp washcloth to the site for 5 minutes this increases your blood circulation, which makes it easier for the phlebotomist to find a vein. Drinking water helps blood flow better and makes the veins more likely to stick up and be found easily (even if the patient is fasting) What I do if I can't find the vein? After all these methods if the phlebotomist does not succeed in reaching the vein, another phlebotomist may step in to complete the procedure. This keeps both the patient and the phlebotomist from becoming flustered and should be seen as a reassuring step. Blood collection from Cannula In general, blood should not be drawn from an arm with a cannula because intravenous therapy (IV) fluid may dilute the specimen, so collect from the opposite arm if possible. Otherwise, follow these procedures: Turn off the IV for at least 2 minutes before venipuncture. Apply the tourniquet below the IV site. Select a vein other than the one with the IV. Draw 5 ml of blood and discard before drawing the specimen tubes for testing. Alcohol Decontamination Use 70% alcohol as disinfectant. Let it to dry to avoid hemolysis and burning sensation. Note: if sample is collected for ethanol concentration determination use another disinfectant other than alcohol Apply tourniquet Apply the tourniquet 3-4 inches above the selected puncture site. Tourniquet obstructs the venous return so it helps to distend the vein. As a rule, the tourniquet should not be placed too tightly (as to stop arterial flow) or left on the patient for more than 2 min. What are the effects if it left for more than 2 min? Prolonged application of the tourniquet results in partial stasis of blood and changes many quantitative values of blood components as: Concentration of total protein, lipids, iron, GOT and bilirubin will increase Concentration of potassium will decrease. Note: Check the pulse at the wrist to make sure that arterial circulation is not cut off. Venipuncture with needle and syringe 1. Check the syringe · Check to be sure that the syringe works smoothly by pressing the piston. · The syringe must be dry to avoid hemolysis of the red cells. · The plunger must be pushed firmly to the bottom of the cylinder to prevent injection of air into the vein, this can be fatal. 2. Feel the vein by left hand 3. Fix the vein by drawing skin tight over the vein to prevent vein from moving 4. Enter by the needle at 45 degree angle (under the skin and then into the vein) When the needle enter the vein there is sudden lose of resistance and blood come in the head of needle Note: Do not probe or move the needle horizontally, as discomfort and possible nerve damage may result. 5. Remove the tourniquet once the needle has been inserted Note: If the needle were removing prior to the Tourniquet being removed, blood would be forced out of the venipuncture site, resulting in hematoma. 6. Withdraw blood gradually by gently pulling upon the syringe plunger (don not use negative pressure) Note: Vigorous pulling on the plunger of the syringe can collapse the vein, produce hemolysis of the blood specimen 7. Place a sterile cotton piece over the point where the needle entered the skin. 8. Remove the syringe quickly 9. Patient press cotton for 5 min to stop bleeding and do not bend arm 10. Dispose of contaminated materials/supplies in designated containers. Venipuncture with evacuated tubes 1. Insert the stopper of the first tube to be drawn into the adaptor. 2. Do not pushes too far as that might cause premature loss of vacuum if it is punctured by the needle. Before using the tube it should be tapped gently to dissolve any additives from stopper and this prevents aspiration of additives into vein 3. Insert the needle into the vein. 4. After entry into the vein push the tube all the way into the holder; vacuum is broken, and blood flows freely into the tube. The vacuum in the tube causes blood to move through the needle and into the tube. 5. Remove the tourniquet once the blood flow has begun. 6. Fill the tube until the vacuum is exhausted. 7. Remove tube from adaptor and insert subsequent tubes. Note: ensure the needle is not moved while tubes are being changed. 8. Place a sterile cotton piece over the point where the needle entered the skin. 9. Remove the needle quickly 10. Patient press cotton for 5 min to stop bleeding and do not bend arm Order of the tubes When we use evacuated system tubes must be drawn in a specific order to avoid cross-contamination of additives between tubes. The recommended order of draw is: Coagulation tube (light blue top) If there is a concern regarding contamination by tissue fluids or thromboplastins, then one may draw a non-additive tube first, and then coagulation tube Non-additive tube (red top) ESR tube Additive tubes in this order: Sodium heparin (green top) EDTA (lavender top) Fluoride (light gray top) Can I use local anesthetic? If a patient is really needle phobic cream containing local anesthetics may help. This should be applied for at least 30 minutes to allow the local anesthetics to take effect. If a blood sample is unobtainable what I do? 1. Change the position of the needle. If the needle has penetrated too far into the vein, pull it back a bit. If it has not penetrated far enough, advance it farther into the vein. Adjust the angle (the bevel may be against the vein wall). 2. Loosen the tourniquet. It may have been applied too tightly, thereby stopping the blood flow. 3. Re-anchor the vein. Veins sometimes roll away from the point of the needle and puncture site. 4. Try another tube. There may be no vacuum in the one being used. If a blood stops flowing into the tube what I do? The vein may have collapsed. Collapsed veins occur when there is excessive vacuum in the syringe. Smaller veins and veins of geriatric patients are prone to collapse. Note: Reduce the aspiration rate during your blood drawto avoid vein collapse. In this case resecure the tourniquet to increase venous filling. If this is not successful, remove the needle, take care of the puncture site, and redraw. Handling of specimen butting samples in test tube Be sure that the tube is dry Remove the needle from the syringe Pour the blood gently from the syringe at the wall of the tube Mix well blood with anticoagulant if found Label the tube and write the name, tests and date Order of the tubes المبدأ العام هنا هو البدء بالعينات التى تحتاج الى كميه محدده من الدم مثل سرعه الترسيب ثم العينات المأخوده على مانع للتجلط ثم اخيرا العينات السيرم و بناء على دلك يجب ان يكون ترتيب العينات كالاتى: Coagulation tube ESR tube Heparin tube EDTA tube Fluoride tube Plain tubes لاحظ: هدا الترتيب يختلف عن ترتيب الانابيب فى نظام vacuum system . Separation of serum or plasma For plasma: For plasma samples, blood should be cooled and centrifuged as soon as possible and separated immediately after centrifuging. Stoppers should not be opened during the centrifuging. For plasma, blood should spin 15 minutes at 2000g to 3000g. The plasma should be separated from cells and transferred to a clean tube. For serum: The blood samples are allowed to clot at 15-24 °C. The clotting time should be minimally 30 minutes and maximally one hour. For serum samples, blood should be centrifuged within one hour after blood collection. For serum preparation blood should spin for 10 minutes at 1500 g. The serum should be separated from clot and transferred to a clean tube. ملحوظه هامه: ينبغى الا يغادر المريض المعمل حتى تتاكد من سلامه العينات و دلك بعد فصلها فى السنترفيوج و التأكد من عدم وجود تحلل (hemolysis) او التأكد من عدم وجود جلطه فى العينات المأخوده على مانع تجلط. Preservation of sample لا يتم حفظ العينات فى المعمل بعد اخد العينه بصوره عشوائيه و لكن لابد ان يتم دلك على اساس علمى بناء على نوع التحليل و لابد من معرفه الامور الاتيه عن كل تحليل حتى تكون عمليه الحفظ سليمه : هل لابد من ان تفصل العينه سريعا ام لا؟ بعض المواد تتاثر بمده بقاء البلازما او السيرم مع كرات الدم الحمراء دون ان تفصل Glucose and ammonia must be separated quickly ما هى درجه الحراره الملائمه لحفظ العينه؟ و يختلف دلك من نوع تحليل لاخر فمثلا : Troponine and D – dimmer must be preserved at room temperature and don’t freeze it Enzymes as GOT, GPT, ALP, ….. , must be preserved at refrigerator at 4°C the test may be done in this case within 7 days. If it is anticipated that analysis can not occur within 7 days, samples should be frozen immediately at -20°C. Coagulation factors must be preserved at freezer at -70°C هناك بعض التاثيرات التى تطرأ على العينه عند حفظها فى درجه حراره الغرفه مثل : High temperature may affect enzyme activities MCV increase due to swelling of RBCs Prothrombin time slowly increase ESR, PLT, WBCs decrease ما هى اقصى مده زمنيه لحفظ العينه بحيث تظل العينه محتفظه بنشاطها؟ و هدا يعنى ان لكل تحليل مده زمنيه معينه ادا تاخر عمل التحليل عن هده المده فان الماده المراد قياسها يمكن ان تتكسر فى حاله تحاليل الكيمياء او تموت الخلايا فى حاله تحاليل الهيماتولوجى و بدلك تكون نتيجه التحليل خاطئه و من امثله دلك : Most enzymes are stable at refrigerator for about 1 week Reticulocytic count must be made during 6h after blood collection Prothrombin time must be analyzed within 12h Only 1 h allowed for platelets and blood smear before changes starts to occurs Only 3 h allowed for PCV and ESR Only 20 h allowed for Hb, RBCs, WBCs هل يوجد شروط خاصه اخرى للحفظ؟ بالطبع هدا لا ينطبق على جميع التحاليل و لكن فى بعض التحاليل يكون هناك شرط اضافى لحفظ العينه بطريقه سليمه و يمكن معرفه الشرط من ورق الكيماويات الخاص بالتحليل. من امثله دلك : Bilirubin must be stored at dark (because light can degrade bilirubin ) Calcium is preserved at plastic tube ملحوظات هامه : لا ترمى عينات الدم مباشره بعد انتهاء التحليل لانك من الممكن ان تحتاج العينه للاعاده مره اخرى(مثلا لتقييم باقى النتائج) ايضا لا ترمى عينات الدم فى نفس اليوم بل احتفظ بها فى الثلاجه يوم اخر على الاقل لانك ربما تحتاجها للاعاده او اضافه تحليل اخر لنفس المريض كلما كانت درجه الحراره التى تحفظ عندها العينه اقل كلما زادت مده بقاء العينه Specimen transport عند نقل العينات خارج المعمل (لارسلها الى فرع اخر او معمل اخر لعمل تحليل معين ليس عندك فى المعمل ) لابد من ملاحظه الاتى : فصل العينه و حفظها بطرقه صحيحه لابد ان توضع العينه فى انبوبه محكمه الغلق تكتب كل البيانات الخاصه بالعينه على الابوبه و كدلك فى ورقه مع العينه اذا كان للمريض وضع خاص يفضل ابلاغ المعمل بذلك (مثلا ان يكون صائما او ياخد ادويه معينه مثل مضادات التجلط) ادا كان لابد من ارسال العينات مجمده نستخدم لها الثلج الجاف (solid co2 dry ice) يفضل الاحتفاظ بعينه احتياطى فى المعمل من العينات الخارجيه (قد تحتاج لارسالها معمل اخر او اعادتها فى نفس المعمل او عمل تحليل اخر لنفس المريض للتاكد من النتيجه التى و هده العينه الاحتياطيه توفر الوقت بدلا من انتظار المريض و سحب عينه اخرى منه)