Clinical Chem Lab (patient preparation and specimen collection)

a. alteration in acid-base balance

b. ↑ in FFA

c. ↑ in lactate dehydrogenase

d. Tchol increased and HDL decreases by 15%

a. hemoconcentration

b. anaerobiosis

increase in : proteins, Chol., TGL, calcium, potassium

decrease in: venous pO2 and pH

a.Conscious Inpatients / Hospitalized patients:

• Verbally ask their full names

• Verify the name using ID bracelet

b.Sleeping patients:

• Identified in the same manner as concious in- patients

• Must be awakened before blood collection

c.Unconcscious, Mentally incompetent patients:

• Identified by asking the attending nurse or relative; ID

bracelet

d.Infants and children:

• A nurse or relative may identify the patient or by ID

bracelet

e. Outpatient/Ambulatory patient:

• Verbally ask their full names, address or birth date

• If patient has ID card or bracelet, same manner as with

hospitalized patients

Arterial puncture, venipuncture, and skin puncture

-A process by which blood is obtained from a

patient’s artery.

- Arterial blood is the oxygenated blood with a

bright red color

-Use: for blood gas analysis and pH measurement

Sites:

 Radial 23-25 gauge

 Brachial 18-20 gauge

 Femoral 18-20 gauge

 scalp

 Umbilical

Note: blood samples are collected without a tourniquet

Note: before collection from radial artery, modified

Allen test should be done 

Major Complications:

 Thrombosis

 Hemorrhage

 Emboli

 Possible infection

Unacceptable sites:

o Irritated

o Edematous

o Near a wound

o AV shunt (arterioventricular) or fistula

Modified Allen Test

1. Have the patient make a fist and occlude both the ulnar (opposite of thumb side) and the radial

arteries (closest to the thumb) by compressing with two fingers over each artery

2. Have the patient open his or her fist, and observe if the patient’s palm has become bleached of

blood

3. Release the pressure on the ulnar artery (farthest from the thumb) only, and note if blood

return is present. The palm should become perfused with blood. Adequate perfusion is a positive

test indicating the arterial blood may be drawn from the radial artery. Blood should not be taken

if the test is negative

-A process by which blood is obtained from a

patient’s vein

- Venous blood is the deoxygenated blood with a

dark red color

Sites: Antecubital fossa region, wrist,dorsal aspects of hands, veins on the ankle

a. Median cubital- best site for venipuncture ; largest and the best anchored vein

b. Cephalic vein- second choice; superficial vein of arm ( thumb side) commonly

used for venipuncture

c. Basilic vein- should not be chosen, unless no other vein is more prominent due

to its close proximity to the brachiel artery; large vein on inner side

( “pinky side”) of arm 

Note:

• If petechiae appear- it indicates that minute amounts of blood

have escaped into the skin epithelium

• Venous blood is not the specimen of choice for Blood gas

measurement

-to obstruct the return of venous blood to the heart

- distend the veins

-If blood pressure cuff is used, it is inflated 60 mmHg

- If tourniquet closer to the site: the vein may collapse as the blood above is above the intended venipuncture site

- When used during preliminary vein selection: release and reapply after 2 minutes

-No traces of alcohol should remain:

causes hemolysis and contaminate

glucose testing

- For ethanol testing: Benzalkonium

chloride or Zephiran is used

- For blood culture: 70% alc followed

by iodophor

-For blood culture (infants) and

patients with iodine sensitivity:

Chlorhexidine gluconate

-The gauge of the needle is inversely related to the size

of the needle

- 21 gauge: standard for venipuncture

- 23 gauge: for children; 23 or 25 gauge is for winged

infusion set (butterfly)

- 23 gauge butterfly: for small and difficult veins

-25 gauge: collection from scalp or other tiny veins of

infants

Needle length: 1 – 1.5 in: 21-23 gauge

½ to ¾ in: butterfly needle

 Clotting time for tubes using gel separators is

approx 30 minutes

 Tubes with clot activators, such as thrombin, will

clot in 5 minutes

 Plain red tubes with no additives take about 60

minutes to clot completely

1. IV lines in both arms

2. Burned areas

3. Areas with hematoma

4. Thrombosed veins

5. Edematous arms

6. Mastectomy on one or both arms

7. Arms with AV shunt

8. Casts

a. Immediate local complication

1. Hemoconcentration – increase in the number of

formed elements in blood resulting either from a

decrease or increase in plasma volume

2. Failure of blood to enter the syringe/vacutainer tube

3. Syncope (fainting) – transient loss of consciousness

due to lack of oxygen in the brain

- if seated patient feels faint, the needle should be

removed immediately, the patient’s head should

be lowered between the legs, and the patient

should be instructed to breathe deeply

.

b. Late local complication

1. Thrombosis – an abnormal vascular condition in which

thrombus develops within a blood vessel of the body

2.Thrombophlebitis – is an inflammation of a vein accompanied

by a clot which occurs as a result of trauma to the vessel wall

c. Late general complication

1. Serum hepatitis

2. AIDS

1. Using needle that is too small

2. Pulling a syringe plunger back too fast

3. Expelling the blood vigorously into a tube

4. Forcing the blood from a syringe into an

evacuated tube

5. Shaking or mixing the tubes vigorously

6. Performing blood collection before the

alcohol has dried at the collection site

1. Vein is fragile or too small for the

needle size

2. Needle penetrates all the way

through the vein

3. Needle is partly inserted in to vein

4. Needle is removed while the

tourniquet is still on

5. Pressure is not adequately applied

after venipuncture

 Usually preferred for children older

than one year old

 Length of lancet: 1.75mm

 Depth of incision:

 Measurements should be performed within 45 mins to 1 hr after collection

 Serum or Plasma: separated w/in 1hr

 3000 RCF for 10 mins: centrifugation requirement

a. To prevent glycolysis

∞ 2mg NaF/mL of blood – prevents glycolysis for up to 48-72 hours

∞ Glucose conc in unseparated serum or plasma- decreases rapidly in the first 24 hours

b. Certain substances are very unstable

∞ increase in: total bilirubin, sodium, urea, nitrogen, albumin, calcium, magnesium and total protein

c. To prevent shift of electrolytes

∞ results in: false increase of potassium and decrease of sodium in serum/plasma

d. To prevent hemolysis

∞ Increased enzymes (LD, ACP, ALT, AST); electrolytes (Mg, P, K); TP; albumin; cholesterol and iron

∞ Interferes with the color reactions

∞ Increases bilirubin levels

a clear colorless, sterile, extravascular fluid that circulates in the

ventricles of the brain the subarachoid spaces & the spinal cord.

90 to 150 mL= normal CSF of the adult

10 to 60 mL = newborn

∞ Most common method of collection: Lumbar puncture (between the 3rd or 4th lumbar

vertebrae, or between the 4th and 5th lumbar vertebrae)

∞ Other methods: cisternal puncture, lateral cervical puncture

Main functions of CSF

1. Serve as mechanical buffer

2. Regulates the volume of intracranial contents

3. Provides nutrient medium for CNS

4. Acts as excretory channel for metabolic products of CNS.

* 4 sterile test tubes 5 ml each

1. chemical test

2. microbiological studies

3. Total cell counts & differential counts

4. immunology & serology studies

Purpose:

 Bacterial, fungal, mycobacterial, amebic meningitis

 Malignancy

 Subarachnoid bleeding

 Multiple sclerosis

Note:

© Required pressure before collection: between 90 and 180 mmHg

© Volume collected: 20 mL of CSF (not more than 2mL can be

removed when pressure is greater than 200 mmHg)

∞ Random specimens

∞ First- morning specimen: most concentrated

∞ 24 hr urine collection: Sodium fluoride can be added to urine for glucose

determinations to inhibit bacterial growth and cell glycolysis