Blood simple

When you first start your jobs after graduating, the chances are you'll have to take blood rather a lot. Newly qualified doctors, Peter Cartledge and Georgina Moore share their experience and look at the evidence

After years of hard grind at medical school, and armed with all that knowledge, you are ready to start saving lives. Then, suddenly you are brought back to earth with a bump when you realise that most of your first year will be spent filling in forms and taking blood. Soon enough the dreaded first night comes around. The time is 3 am, and you are struggling to take blood from a patient who needs an urgent cross match for a blood transfusion. You run through the options in your mind. Should you call a more senior doctor, or should you try again in the blind hope that you will hit the vein? Before you start to panic, try some of these helpful tips on taking blood and doing peripheral cannulation.

Myths about venepuncture

You cannot take blood from a cannula once it has been used

This is false. A number of studies have now shown that there is no significant difference between the laboratory values of samples taken from a peripheral cannula and those taken by venepuncture.^{1 - 3} But remember, the bigger the cannula, the easier it is to take blood. You should not use a cannula smaller than 20 gauge. However, you cannot take a clotting sample from a cannula if it has been flushed with heparinised saline or if a heparin infusion has been going through it.⁴

You cannot take blood from an arm with an infusion running

Again, this is false. You can take blood anywhere distal to the cannula or just stop the infusion for two to three minutes then use the cannula or new proximal insertion site.⁵

You should not insert a cannula into the feet

This is false too. But you should only do it if absolutely necessary. Cannulation in the lower extremities should usually be avoided due to increased risk of thrombophlebitis (inflammation of a vein associated with thrombus formation) and pulmonary embolism. If you need to insert one in an emergency, you should remove it as soon as you can place one in a central or upper limb extremity.

⁶

PAUL RAPSON/SPL

You cannot take cultures out of a cannula

This is true for children and false for adults. In children, evidence shows a contamination rate of 10% via a new cannula compared with 2% with good phlebotomy technique.⁷ In adults, no evidence shows that contamination rates are any higher when taking blood from a newly inserted cannula.⁸

You cannot take blood or cannulate an arm with an arteriovenous fistula

This is true: you do not want to have to explain to the patient or the renal team how you messed up the access for dialysis.⁶

You cannot take blood from an arm on the same side as a previous mastectomy

This is true; you must get senior approval first. Lymphoedema must be ruled out if there is no other site for access, such as in an emergency.⁶

You cannot send a sample off if it is clotted

This is false; it may be a pathology sample. These samples automatically clot because of the clotting accelerator in the tube.⁹

You do not have to put the address on the label

This once again is false. You must always take care to label the sample and the blood request forms correctly. Most laboratories will require patient identifiers, such as name, age, and hospital number. They also need the correct location. Do not blame the laboratory staff when you do not get your result - you probably did not label it.

You cannot inject blood into a vacuum sample bottle

This is true. If you try it you will cover yourself and the whole room in blood. To avoid covering yourself in blood use a large needle, and allow the vacuum to draw the blood into the bottle.

Phlebotomists are vampires

This is false. Phlebotomists are not vampires. Phlebotomists follow universal precautions. Vampires do not. Vampires drink blood. Phlebotomists do not.

Tips to improve your technique

1. Are you sure you really need that test? When you first start, you will be ordering tests that are not appropriate. Think before you request - tests cost money and needles hurt.
2. Have a chat with the patient before you try to take blood. You should always remember to explain the procedure.
3. Ask the patient for his or her preferred arm, they will appreciate being involved in the process.
4. Rub or tap the back of the hand.¹⁰
5. Good vein selection is crucial. Take your time - the bigger and the straighter the better. Avoid veins that move on palpation if possible.
6. When selecting a vein, a palpable vein may be a better choice than a vein you can see.
7. Chose the right needle for the right vein. Use a vacuette for big veins in the ante-cubital fossa, and a butterfly for the back of the hand or foot.
8. Avoid joints in cannulation.
9. Ask the patient to cough or curl their toes when you insert the needle. It will reduce the amount of pain they feel.¹¹
10. When asked to resite a cannula, think and ask if it is really necessary. Many lines can be flushed gently with 5 ml of saline that clears any minor blockage. Small 2 ml syringes are the most effective at clearing minor blocks.¹⁰
11. Be careful in people who have had a cerebral vascular incident. They have decreased sensation making it difficult for them to detect phlebitis.

    ⁶
    

12. If a haematoma or large swelling starts to form, do not panic. Apply pressure - it will reduce the bruise.
13. Know your hospital's policy if you get a needlestick injury. These things always occur at 2 am when you are tired.

If you fail

• Try exercising the arm or placing it in warm (not hot) water, try other sites - for example, a vein in the foot

  ¹²

• If you fail at cannulation, come back and try later. Consider using subcutaneous fluids. Glucose and 0.9% saline can be given subcutaneously via a butterfly needle

  ⁶¹²

• Use a sphygmomanometer cuff, inflating it to above diastolic blood pressure
• If this fails, pump it up to above systolic pressure and leave it in place for two minutes. After the cuff is released, the lactic acid that has accumulated will cause a reflex vasodilatation. This method is painful, so you should only use it as a last resort^10-13
• Tighten the tourniquet, feel for the veins that cannot be visualised, and release the tourniquet. Anything that "disappears" to palpation is a vein
• Two or three attempts is the most you should allow yourself ^6-13
• Repeated unsuccessful attempts are distressing for the patient and may ruin those few accessible veins that the patient has¹³
• Use paediatric tubes, which only require a few drops of blood, for patients with difficult veins⁵ If the tips above are not helping and you still have not managed to get access then get senior help
• Keep going; when you first start out you will miss a lot. Practice makes perfect.

Times when a cannula must be in place¹⁰

There are times when you really do have to have intravenous access. These are:

• When a patient is acutely ill or unstable
• If there is hypovolaemia or poor oral intake
• When there is serious danger of blood or fluid loss
• For certain drug infusions - for example, antibiotics or heparin.

Taking blood from a cannula^9-10

Once the cannula is in place:

• Raise the arm above the level of the left atrium
• Remove the cap and place a syringe into the back of the cannula
• Lower the arm and tighten the tourniquet
• Throw away the first 5 ml if the cannula has been previously used
• Gently aspirate the required amount of blood
• Flush the cannula with saline and reapply the cap.

Warning - be careful of taking blood out of a cannula in a precious vein, such as the back of the hand. If you damage the vein you will have to put a new cannula in and take blood again.

Taking blood from a central line

Central lines should only be used for taking blood as a last resort. Risking catheter sepsis or a clotted line is not worth it for a full blood count.¹⁰

• Stop any infusions going into the central line at least one minute before sampling
• Place the patient in a supine position. Have the patient turn their head away from the central venous catheter site during the procedure
• Clamp the line before removing the cap
• Connect a 5 ml syringe to the line before unclamping then discard the first 5 ml of blood withdrawn
• Remove required blood for the sample
• Flush with 10-20 ml of 0.9% isotonic saline (or heparinised saline if hospital protocol).

Order of tubes

If you are using a vacuette system then the order in which you take the sample is important. This is especially true for blood cultures, which should always be taken first to minimise the risk of contamination:

1. Blood cultures
2. Chemical pathology
3. Clotting screen
4. Transfusion
5. Haematology..

Who should be taking blood and cannulating patients?

As a newly qualified doctor, you are going to be pretty busy. The General Medical Council has made it clear that the people you work for should be making steps for other healthcare professionals to be doing these roles for you. Just remember that nurses are busy too, but encourage them to take more of your bloods and cannulate more of your patients when possible.¹⁴

Peter Cartledge, preregistration house officer
Email: petercartledge@doctors.org.uk

Georgina Moore preregistration house officer, St James's University Hospital, Leeds


studentBMJ 2005;13:221-264 June ISSN 0966-6494

1. Himberger JR, Himberger LC. Accuracy of drawing blood through infusing intravenous lines. Heart Lung 2001;30:66-73.
2. Seemann S, Reinhardt A. Blood sample collection from a peripheral catheter system compared with phlebotomy. J Intraven Nurs 2000;23:290-7.
3. Mohler M, Sato Y, Bobick K, Wise LC. The reliability of blood sampling from peripheral intravenous infusion lines: complete blood cell counts, electrolyte panels, and survey panels. J Intraven Nurs 1998;21:209-14.
4. Pinto KM. Accuracy of coagulation values obtained from a heparinized central venous catheter. Oncol Nurs Forum 1994;21:573-5.
5. Read DC, Viera H, Arkin C. Effect of drawing blood specimens proximal to an in-place but discontinued intravenous solution.Can blood be drawn above the site of a shut-off i.v.? Am J Clin Pathol 1988;90:702-6.
6. Terry J, Baranowski L, Lonsway RA, Hedrick C. Intravenous therapy, clinical principles and practice. 1st ed. London: Saunders, 1995.
7. Norberg A, Christopher NC, Ramundo ML, Bower JR, Berman SA. Contamination rates of blood cultures obtained by dedicated phlebotomy vs intravenous catheter. JAMA 2003;289:726-9.
8. Smart D, Baggoley C, Head J, Noble D, Wetherall B, Gordon DL. Effect of needle changing and intravenous cannula collection on blood culture contamination rates. Ann Emerg Med 1993;22:1164-8.
9. Guder WG, Narayanan S, Wisser H, Zawta B. Samples: from the patient to the laboratory Darmstadt: Git Verlag, 1996.
10. Donald A, Stein M. Hands-on guide for house officers Oxford: Blackwell, 1996.
11. Usichenko TI, Pavlovic D, Foellner S, Wendt M. Reducing venipuncture pain by a cough trick: a randomized crossover volunteer study. Anesth Analg 2004;98:343-5.
12. Ballinger A, Patchett S. Clinical medicine. 2nd ed. London: Saunders, 2000.
13. Fisken RA. House physician's survival guide. Reprinted ed. London: Churchill-Livingstone, 1996.
14. General Medical Council. The new doctor: recommendations for general clinical training London: GMC, 1997.

       

           

	Responses published this month

Articles	Responses
EDUCATION Blood simple       Peter Cartledge (June 2005)	Debs White (June 30, 2005) Read this response
EDUCATION Blood simple       Peter Cartledge (June 2005)	Dr Stephen Mathieu (August 01, 2005) Read this response

	EDUCATION Blood simple       Peter Cartledge (June 2005)
	Debs White (June 30, 2005)       Final year medical student, University of Aberdeen debs.white@doctors.org.uk
	As someone going to commence their PRHO posts in a month, I thought this was a very helpful article, presenting the evidence and putting to bed a number of myths on a subject that I, like most medics, have learned about from house officers and other students who were never really properly taught themselves. We may joke about nurses having to do 40 (or whatever it is) supervised cannulations before being able cannulate independently, but this must be better than the medical "see one, do one..." learning model, which is how I learned to cannulate (with much spilling of blood!) I also remember a student colleague of mine who was taking blood from a central line being asked by a nurse if she had read the relevant protocol. "Protocol?!" was the response from both of us; such a procedure you just get on and do if someone has shown you once. I do think medical education is improving with respect to the teaching of such practical skills and procedures, but probably not fast enough. One question remains for me having read this article: what is the evidence about using alcohol wipes to clean the skin before venepuncture or cannulation? Various medics have told me that their only usefulness is to irritate the vein and make it easier to access, and there is no point in using them for reducing infections. Nurses seem quite keen on them, though...

	EDUCATION Blood simple       Peter Cartledge (June 2005)
	Dr Stephen Mathieu, BMedSci MRCP (August 01, 2005)       SHO Anaesthetics, Anaesthetic Deparmtent. Poole General Hospital stevemathieu@tiscali.co.uk
	Response to Debs White (June 30, 2005) question raised from original article entitled `Blood simple` by Peter Cartledge (June 2005) The necessity to prepare the skin prior to invasive procedures has been a much-debated area of practice. Whilst the evidence is available for decontamination of skin prior to central venous cannulation (Snydman et al 19821, Pratt et al, 20012), there is less compelling literature for peripheral access. Whilst the literature is sparse, It has been demonstrated that Isopropyl alcohol, 0.5% alcoholic chlorhexidine and 2% iodine tincture have all been effective agents for skin preparation prior to peripheral intravenous cannulation (de Vries et al, 19973, Goldman et al, 19974; Mimoz et al, 19995). However, 70% Isopropyl alcohol (e.g. Steret) is recommended as the antiseptic of choice due to its effectiveness, availability and ease of use. It does seem reasonable to conclude that avoiding the introduction of skin contaminants intravascularly is prudent. Whilst skin preparation should therefore be a routine practice, it is important not to overlook other simple measures such as hand washing, use of gloves and avoiding palpating the vessel after cleaning. Snydman DR, Gorbea HF, Pober BR, Majka JA, Murray SA, Perry LK; 1982; Predictive value of surveillance skin cultures in total-parenteral-nutrition-related infection; Lancet, vol. 2,no. 8312; 1385-1388. Pratt RJ, Pellowe CM, Loveday HP, Robinson N, Smith GW; 2001;The epic Project: Developing National Evidence-based Guidelines for Preventing Healthcare associated Infections; Journal of Hospital Infection (supplement); 47; S1-S82. De Vries JH, van Dorp WT, van Barneveld PWC; 1997; A randomized trial of alcohol 70%versus alcoholic iodine 2% in skin disinfection before insertion of peripheral infusion catheters; Journal of Hospital Infection; 36(4); 317-320. Goldman M, Roy G, Frechette N, Decary F, Massicotte L, Delage G; 1997; Evaluation of donor skin disinfection methods; Transfusion; 37(3) 309-312. Mimoz O, Karim A, Mercat A, Cosseron M, Falissard B, Parker F, Richard C, Samii K, Nordmann; 1999; Chlorhexidine compared with povidone-iodine as skin preparation before blood culture. A randomized, controlled trial; Ann Intern Med.; 131 (11); 834-837.