alzheimer
08-06-2005, 12:57 PM
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.<SUP>1 - 3</SUP> 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.<SUP>4</SUP>
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.<SUP>5</SUP>
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.
<SUP>6</SUP>
<CENTER>http://www.studentbmj.com/issues/05/06/education/images/view_11.jpg
PAUL RAPSON/SPL </CENTER>
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.<SUP>7</SUP> In adults, no evidence shows that contamination rates are any higher when taking blood from a newly inserted cannula.<SUP>8</SUP>
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.<SUP>6</SUP>
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.<SUP>6</SUP>
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.<SUP>9</SUP>
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
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.
Have a chat with the patient before you try to take blood. You should always remember to explain the procedure.
Ask the patient for his or her preferred arm, they will appreciate being involved in the process.
Rub or tap the back of the hand.<SUP>10</SUP>
Good vein selection is crucial. Take your time - the bigger and the straighter the better. Avoid veins that move on palpation if possible.
When selecting a vein, a palpable vein may be a better choice than a vein you can see.
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.
Avoid joints in cannulation.
Ask the patient to cough or curl their toes when you insert the needle. It will reduce the amount of pain they feel.<SUP>11</SUP>
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.<SUP>10</SUP>
Be careful in people who have had a cerebral vascular incident. They have decreased sensation making it difficult for them to detect phlebitis. <SUP>6</SUP>
If a haematoma or large swelling starts to form, do not panic. Apply pressure - it will reduce the bruise.
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 <SUP>12</SUP>
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 <SUP>612</SUP>
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<SUP>10-13</SUP>
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 <SUP>6-13</SUP>
Repeated unsuccessful attempts are distressing for the patient and may ruin those few accessible veins that the patient has<SUP>13</SUP>
Use paediatric tubes, which only require a few drops of blood, for patients with difficult veins<SUP>5</SUP><LIDO feel guilty about taking blood or cannulating a patient - you are not doing it for fun 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 place<SUP>10</SUP>
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<SUP>9-10</SUP>
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.<SUP>10</SUP>
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:
Blood cultures
Chemical pathology
Clotting screen
Transfusion
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.<SUP>14</SUP>
Which cannula to use<SUP>6 10</SUP> <TABLE summary="Table distinguishing cannulas by colour, size and use" border=0><TBODY><TR><TD>Colour</TD><TD>Size></TD><TD>Use</TD></TR><TR><TD>Blue</TD><TD>22G></TD><TD>Small fragile veins; children or elderly people</TD></TR><TR><TD>Pink</TD><TD>20G></TD><TD>Giving intravenous drugs and fluids</TD></TR><TR><TD>Green</TD><TD>18G></TD><TD>Blood transfusions, fluids</TD></TR><TR><TD>Grey</TD><TD>16G></TD><TD>Rapid fluid administration, gastrointestinal bleeds</TD></TR><TR><TD>Orange</TD><TD>14G></TD><TD>Rarely used, serious bleeds</TD></TR></TBODY></TABLE>
Peter Cartledge, preregistration house officer
Email: petercartledge@doctors.org.uk (petercartledge@doctors.org.uk)
Georgina Moore preregistration house officer, St James's University Hospital, Leeds
studentBMJ 2005;13:221-264 June ISSN 0966-6494
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.<SUP>1 - 3</SUP> 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.<SUP>4</SUP>
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.<SUP>5</SUP>
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.
<SUP>6</SUP>
<CENTER>http://www.studentbmj.com/issues/05/06/education/images/view_11.jpg
PAUL RAPSON/SPL </CENTER>
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.<SUP>7</SUP> In adults, no evidence shows that contamination rates are any higher when taking blood from a newly inserted cannula.<SUP>8</SUP>
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.<SUP>6</SUP>
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.<SUP>6</SUP>
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.<SUP>9</SUP>
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
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.
Have a chat with the patient before you try to take blood. You should always remember to explain the procedure.
Ask the patient for his or her preferred arm, they will appreciate being involved in the process.
Rub or tap the back of the hand.<SUP>10</SUP>
Good vein selection is crucial. Take your time - the bigger and the straighter the better. Avoid veins that move on palpation if possible.
When selecting a vein, a palpable vein may be a better choice than a vein you can see.
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.
Avoid joints in cannulation.
Ask the patient to cough or curl their toes when you insert the needle. It will reduce the amount of pain they feel.<SUP>11</SUP>
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.<SUP>10</SUP>
Be careful in people who have had a cerebral vascular incident. They have decreased sensation making it difficult for them to detect phlebitis. <SUP>6</SUP>
If a haematoma or large swelling starts to form, do not panic. Apply pressure - it will reduce the bruise.
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 <SUP>12</SUP>
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 <SUP>612</SUP>
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<SUP>10-13</SUP>
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 <SUP>6-13</SUP>
Repeated unsuccessful attempts are distressing for the patient and may ruin those few accessible veins that the patient has<SUP>13</SUP>
Use paediatric tubes, which only require a few drops of blood, for patients with difficult veins<SUP>5</SUP><LIDO feel guilty about taking blood or cannulating a patient - you are not doing it for fun 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 place<SUP>10</SUP>
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<SUP>9-10</SUP>
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.<SUP>10</SUP>
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:
Blood cultures
Chemical pathology
Clotting screen
Transfusion
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.<SUP>14</SUP>
Which cannula to use<SUP>6 10</SUP> <TABLE summary="Table distinguishing cannulas by colour, size and use" border=0><TBODY><TR><TD>Colour</TD><TD>Size></TD><TD>Use</TD></TR><TR><TD>Blue</TD><TD>22G></TD><TD>Small fragile veins; children or elderly people</TD></TR><TR><TD>Pink</TD><TD>20G></TD><TD>Giving intravenous drugs and fluids</TD></TR><TR><TD>Green</TD><TD>18G></TD><TD>Blood transfusions, fluids</TD></TR><TR><TD>Grey</TD><TD>16G></TD><TD>Rapid fluid administration, gastrointestinal bleeds</TD></TR><TR><TD>Orange</TD><TD>14G></TD><TD>Rarely used, serious bleeds</TD></TR></TBODY></TABLE>
Peter Cartledge, preregistration house officer
Email: petercartledge@doctors.org.uk (petercartledge@doctors.org.uk)
Georgina Moore preregistration house officer, St James's University Hospital, Leeds
studentBMJ 2005;13:221-264 June ISSN 0966-6494