Why We Discard First Drop Of Blood

[Santi Dubrova]

Bloodglucose monitoring reveals individual patterns of blood glucose changes to aid with meal and activity planning and medication timing. Point-of-care capillary blood glucose testing also allows for a quick response to episodes of high blood glucose (hyperglycemia) or low blood glucose (hypoglycemia).

Obtaining capillary blood by skin puncture is an alternative when venipuncture cannot be performed to reduce the frequency of venous needlesticks and for self-management of diabetes mellitus. The procedure is less painful than venipuncture, and the ease of the skin puncture method makes it possible for patients and families to perform this procedure.

Point-of-care measurement of blood glucose requires obtaining a drop of capillary blood by skin puncture using a single-use, auto-disabling lancet and applying a drop of blood to a specially prepared chemical reagent strip. After the drop of blood is applied to the reagent strip, a reflectance meter provides a measurement of the blood glucose level.

Additionally, alternative blood glucose monitoring devices are available. Some meters allow for an alternative puncture site, including the forearm, palm, and thigh. Continuous interstitial glucose meters use a very small, fine biosensor inserted through the abdomen or the back of the arm that transmits continuous readings of interstitial glucose levels to a monitor or a computer (Figure 1). These systems support the patient with diabetes mellitus who requires assessment of glucose trends and patterns.6

If there are traces of sugar on your fingers when you test, your results can be wonky. Always wash your hands with soap and warm water first. The gentle heat will help your blood flow so you can get a full drop. Be sure to dry off completely too; dampness can dilute your sample or hinder the chemical reaction that performs your test.

I'm currently in the Peace Corps doing nursing education for my hospital in Mongolia. I'm writing up on how to care for diabetic patients and since they tend not to check blood glucose that often (but they have the means), I'm including a section on how to correctly do an accucheck.

I brought along a couple nursing books that I had when I was in school (I graduated in 2008) to help me with lesson planning, and they say to wipe away the first drop of blood when you do a stick, and test the next drop. I've never actually done this in practice, but I've heard of it and I've seen some people do it in my hospital in America.

There's the reasoning- the first drop could be full of serum (? is this true?), but if you squeeze the finger to get the second drop, the second could be as well. One of the reasons I didn't wipe the first drop was because I tended to have really old diabetic patients who seemed to not have enough blood for one drop, let alone two.

I always wipe the first drop, because with alcohol it can cause falsely elevated results. This is what I have been taught and it has been a policy in hospitals. I have seen people use the first drop and I don't think it makes much of a difference, if at all, but I just stick with the policies at the hospital.

The information given here supplements that given in Chapter 2. Users of these guidelines should read Chapter 2 before reading the information given below. This chapter covers background information (Section 7.1), practical guidance (Section 7.2) and illustrations (Section 7.3) relevant to capillary sampling.

Capillary sampling from a finger, heel or (rarely) an ear lobe may be performed on patients of any age, for specific tests that require small quantities of blood. However, because the procedure is commonly used in paediatric patients, Sections 7.1.1 and 7.1.2 focus particularly on paediatric capillary sampling.

The finger is usually the preferred site for capillary testing in an adult patient. The sides of the heel are only used in paediatric and neonatal patients. Ear lobes are sometimes used in mass screening or research studies.

Selection of a site for capillary sampling in a paediatric patient is usually based on the age and weight of the patient. If the child is walking, the child's feet may have calluses that hinder adequate blood flow. Table 7.1 shows the conditions influencing the choice of heel or finger-prick.

A lancet slightly shorter than the estimated depth needed should be used because the pressure compresses the skin; thus, the puncture depth will be slightly deeper than the lancet length. In one study of 52 subjects, pain increased with penetration depth, and thicker lancets were slightly more painful than thin ones (67). However, blood volumes increased with the lancet penetration and depth.

With skin punctures, the haematology specimen is collected first, followed by the chemistry and blood bank specimens. This order of drawing is essential to minimize the effects of platelet clumping. The order used for skin punctures is the reverse of that used for venepuncture collection. If more than two specimens are needed, venepuncture may provide more accurate laboratory results.

Show the child that you care either verbally or physically. A simple gesture is all it takes to leave the child on a positive note; for example, give verbal praise, a handshake, a fun sticker or a simple pat on the back.

Adhere strictly to a limit on the number of times a paediatric patient may be stuck. If no satisfactory sample has been collected after two attempts, seek a second opinion to decide whether to make a further attempt, or cancel the tests.

Phlebotomists are considered to have occupational exposure to blood borne pathogens. The performance of routine vascular access procedures by skilled phlebotomists requires, at a minimum, the use of gloves to prevent contact with blood. Airborne precautions may be considered to provide a level of safety against infectious diseases such as tuberculosis, influenza, and COVID-19. Precautions include a medical grade face mask. With risk for blood spatter a face shield provides protection. A face mask reduces risk for blood culture specimen contamination.

Laboratory coats or work smocks are not typically needed as personal protective equipment during routine venipuncture, but an employer must assess the workplace to determine whether certain tasks, workplace situations, or employee skill levels may result in an employee's need for laboratory coats or other personal protective equipment to prevent contact with blood. It is an employer's responsibility to provide, clean, repair, replace, and/or dispose of personal protective equipment/clothing. As part of presenting a professional appearance, an institutional dress code may include wearing of a laboratory coat or smock.

Patient identification is critical for safety. At least two patient identifiers, such as name and date of birth, are needed. Label collection tubes after identification of the patient. Interruptions and distractions during medical encounters and procedures should be avoided.

A requisition form must accompany each sample submitted to the laboratory. This requisition form must contain the proper information in order to process the specimen. The essential elements of the requisition form are:

Evacuated Collection Tubes - The tubes are designed to fill with a predetermined volume of blood by vacuum. The rubber stoppers are color coded according to the additive that the tube contains. Various sizes are available. Blood should NEVER be poured from one tube to another since the tubes can have different additives or coatings (see illustrations at end).

Needles - The gauge number indicates the bore size: the larger the gauge number, the smaller the needle bore. Needles are available for evacuated systems and for use with a syringe, single draw or butterfly system.

Second - coagulation tube (light blue top). If just a routine coagulation assay is the only test ordered, then a single light blue top tube may be drawn. If there is a concern regarding contamination by tissue fluids or thromboplastins, then one may draw a non-additive tube first, and then the light blue top tube.

NOTE:Tubes with additives must be thoroughly mixed. Erroneous test results may be obtained when the blood is not thoroughly mixed with the additive. Transferring a sample from one collection tube to another or mixing blood from different collection tubes must be avoided.

The phlebotomist's role requires a professional, courteous, and understanding manner in all contacts with the patient. Greet the patient and identify yourself and indicate the procedure that will take place. Effective communication - both verbal and nonverbal - is essential.

Proper patient identification MANDATORY. If an inpatient is able torespond, ask for a full name and always check the armband or bracelet for confirmation. For an inpatient DO NOT DRAW BLOOD IF THE ARMBAND OR BRACELET IS MISSING. For an inpatient the nursing staff can be contacted to aid in identification prior to proceeding.

An outpatient must provide identification other than the verbal statement of a name. Using the requisition for reference, ask a patient to provide additional information such as a birthdate. A government issued photo identification card such as a driver's license can aid in resolving identification issues.

The Patient's Bill of Rights has been adopted by many hospitals as declared by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO). The basic patient rights endorsed by the JCAHO follow in condensed form are given below.

Expect that any discussion or consultation involving the patient's case will be conducted discretely and that individuals not directly involved in the case will not be present without patient permission.

Reasonable informed participation in decisions involving the patient'shealth care. The patient shall be informed if the hospital proposes to engagein or perform human experimentation or other research/educational profits affecting his or her care or treatment. The patient has the right to refuseparticipation in such activity.

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