Laboratory Safety, Hazards, and Specimen Processing – Comprehensive Study Notes

Types of Safety Hazards

• Biological (infectious agents)

  • Possible injury: bacterial, fungal, viral, or parasitic infection

• Sharps (needles, lancets, broken glass)

  • Possible injury: cuts, punctures, blood-borne pathogen exposure

• Chemical (preservatives, reagents)

  • Possible injury: exposure to toxic, carcinogenic, or caustic agents

• Radioactive (equipment & radioisotopes)

  • Possible injury: radiation exposure

• Electrical (ungrounded/wet equipment, frayed cords)

  • Possible injury: burns or electrical shock

• Fire / Explosive (open flames, organic chemicals)

  • Possible injury: burns or dismemberment

• Physical (wet floors, heavy boxes, patients)

  • Possible injury: falls, sprains, strains

Biological Hazards

• Greatest risk comes from direct contact with specimens/patients.

• Infection occurs only if the entire Chain of Infection is complete:

  1. Infectious agent

  2. Reservoir (source)

  3. Exit portal

  4. Mode of transmission

  5. Entry portal

  6. Susceptible host

Hand Hygiene

• Most important infection-control practice is friction while washing.

• Hand-washing procedure:

  • Duration: 15–20 s (sing “Happy Birthday” 2×).

  • Rinse downward (finger-tips lowest).

  • Turn faucet off with a clean paper towel to avoid re-contamination.

• If hands visibly soiled ⟶ hand-wash.

• If NOT visibly soiled ⟶ use alcohol-based hand rub.

Precautionary Systems

1. Universal Precautions – treat all patients as potential blood-borne pathogen carriers;
   excludes urine & body fluids not visibly bloody.

2. Body Substance Isolation – applies to all moist body substances; gloves mandatory; does NOT require hand-washing after glove removal unless visible contamination.

3. Standard Precautions – union of 1 & 2; modern laboratory standard.

Biological Waste

• Discard into containers bearing the biohazard symbol.

• Decontaminate via incineration, autoclave, or certified pick-up.

• Urine: pour into sink; discard emptied container as non-biohazard.

Sharps Hazards

• Dual threat: physical injury + transmission of blood-borne pathogens.

• Dispose immediately in puncture-resistant, biohazard-labelled sharps containers.

Chemical Hazards

• Assume every chemical is hazardous.

Response to Chemical Spills

• On body: do not neutralize; flush with copious water ≥$15$ min; then seek medical help.

• On floor/benchtop: neutralize (if appropriate) then absorb with wet rags or spill pillows.

Chemical Labels

• Must state hazards: “Poisonous”, “Corrosive”, “Carcinogenic”, etc.

• NFPA 704 “Fire Diamond” indicates:

  • Health (blue), Flammability (red), Instability (yellow), Specific (white).

  • Degree indices $0$ (minimal) → $4$ (extreme).

Classes of Hazardous Chemicals

• Teratogens – impair fetal/embryonic development.

• Corrosives – damage skin, eyes, respiratory/GI mucosa.

• Reactive chemicals – may ignite, explode, release heat or gases spontaneously.

• Carcinogens – proven cancer-causing agents.

NFPA Hazard Code Quick Table

• Health Hazard: $4$ = Deadly → $0$ = Normal material.

• Fire Hazard (flash point): $4$ < $73^{\circ}F$, … $0$ = Will not burn.

• Instability: $4$ May detonate → $0$ Stable.

• Specific symbols: ACID, ALK, COR, OX, W (no water), Radiation.

Radioactive Hazards

• From laboratory radioisotope use; effects are cumulative.

• Personnel wear exposure-monitoring devices.

• Radiation during pregnancy endangers fetus.

Electrical Hazards

• All devices must be 3-prong grounded.

• Hospital engineering department should routinely inspect.

• If someone is shocked: do NOT touch victim/equipment; cut power first.

Fire / Explosive Hazards

• Store flammables in safety cabinets & explosion-proof refrigerators located remotely.

• Annual fire drills mandatory for all lab staff.

Fire Classification & Extinguishers

• Class A (Solids) – Pressurized water.

• Class B (Liquids) – Dry chemical, CO$_2$.

• Class C (Electrical) – Halon, Dry chemical, CO$_2$.

• Class D (Metals) – Metal-X extinguisher.

• Class K (Cooking oils) – Special wet chemical units.

PASS Technique

1. Pull pin

2. Aim nozzle

3. Squeeze trigger

4. Sweep side-to-side at base of fire

Physical Hazards

• Avoid running; watch wet floors; bend knees when lifting; keep hair tied; remove dangling jewelry; maintain orderly workspace.

• Wear closed-toe, supportive shoes.

Technical Components of Laboratory Testing

Specimen Types & Processing

1. Whole blood – contains plasma + cells.

2. Serum – liquid after clot; lower fibrinogen, higher $K^+$ from platelets.

   • Allow to clot $20$ min before centrifugation.

3. Arterial blood – for blood gases/pH; collected with heparinized syringe.

   • Primary sites: radial, brachial, femoral.

   • Perform Modified Allen Test before radial puncture.

   • Centrifuge any whole-blood components $10$ min at $1000$–$2000\,g$ (RCF).

4. Urine, CSF, Pleural/Pericardial/Peritoneal fluids, Amniotic fluid

   • Analyze ≤$4$ h; $8$ h if refrigerated at $4^{\circ}C$; $24$ h if frozen at $-20^{\circ}C$.

Serum Appearance Codes

• Normal: clear, straw-colored.

• Hemolyzed – red (↑ free Hb).

• Lipemic – milky (↑ lipids).

• Icteric – yellow-brown (↑ bilirubin).

Venipuncture

• Site: antecubital fossa.

• Veins (order of preference): Median cubital ➔ Cephalic ➔ Basilic.

• Alternative: dorsal hand/foot veins, heels (infants). Legs/ankles/feet require physician order.

• Never use veins on underside of wrist.

• In obese pts, cephalic vein preferred.

• Needle sizes: adults $21$-gauge ($1$–$1.5$ in); pediatrics $23$-gauge.

Order of Draw (Venipuncture)

1. Blood culture bottles / $\text{SPS}$ – Sterile (Yellow)

2. Sodium citrate – Light Blue

3. Plain (Red) / SST (Red-Gray or Gold)

4. Heparin – Green (Light Green, Green, Green/Black)

5. EDTA – Lavender / Pink / Royal Blue w/ EDTA

6. Sodium fluoride/Potassium oxalate – Gray

Capillary Puncture

• Site: 3rd or 4th finger (adults) OR lateral heel (infants).

• Used for Newborn Screening & POCT.

• Capillary blood compared to venous:

  • ↓ RBC, Hct, Hb (tissue-fluid dilution)

  • ↓ Platelets (activation)

  • ↑ Glucose (less utilization)

  • ↑ WBC (pseudo-neutrophilia)

Order of Draw (Capillary)

1. Blood gas specimens

2. Slides/Smears

3. EDTA micro-collection tubes

4. Other anticoagulants

5. Serum

Arterial Puncture – Modified Allen Test

1. Locate radial & ulnar arteries; patient makes tight fist $30$ s.

2. Occlude both arteries.

3. Open hand (blanches).

4. Release ulnar pressure.

   • Flush <$5$–$15$ s → Negative test (adequate collateral circulation) – radial puncture safe.

   • No flush ≥$15$ s → Positive test – do not puncture radial artery.

Evacuated Tube Colors & Additives

• Red (glass) – no additive (plain).

• Red (plastic) / Gold / Red-Gray (SST) – silica clot activator (+ gel in SST); invert $5$×; not for TDM.

• Light Blue – $3.2\%$ Na citrate (9:1 ratio) for coagulation; invert $3$–$4$×.

• Black – $3.8\%$ Na citrate (4:1) for ESR; invert $3$–$4$×.

• Lavender (glass) – liquid $K_2EDTA$ (Sequestrene) – ideal for peripheral blood smears.

• Lavender (plastic) – spray-dried $K_2EDTA$ – Hematocrit, ESR.

• Green – Na/Li heparin.

• Light Green / Green-Black – Li-heparin + separator gel.

• Royal Blue – Na-heparin or $K_2EDTA$ – trace metals/toxicology.

• Gray – Na fluoride + K oxalate (antiglycolytic).

  • Lithium iodoacetate – alternative antiglycolytic (used for BUN; does not inhibit urease).

• Yellow (sterile) – $\text{SPS}$ for microbiology.

• Yellow (blood bank) – Acid Citrate Dextrose (ACD) for preserving cells.

• Tan (glass) – Na-heparin (lead testing).

• Tan (plastic) – $K_2EDTA$ (lead testing).

• Yellow/Gray & Orange – rapid serum tubes with thrombin.

Anticoagulants & Additives – Actions

1. Silica / Thrombin – activate clotting.

2. EDTA / Sodium citrate – chelate ${Ca^{2+}}$.

3. Heparin – inhibits thrombin.

4. Sodium fluoride – inhibits glycolysis.

5. SPS – inhibits phagocytes, complement, some antibiotics.

6. ACD – preserves leukocytes.

Complications of Blood Collection

• Vascular: Ecchymosis, Hematoma, Thrombosis, Pseudoaneurysm, Reflex arteriospasm, Arteriovenous fistula.

• Syncope (fainting): second most common; remove needle immediately if fainting starts.

• Infection, Cardiovascular stress, Iatrogenic anemia, Neurological injury, Dermatologic damage.

Physiologic Factors Affecting Test Results

1. Posture – Standing $\Rightarrow$ hemoconcentration after $10$ min; Supine $\Rightarrow$ hemodilution within $30$ min.

2. Diurnal rhythm – analyte levels follow circadian patterns.

3. Exercise – transient analyte shifts.

4. Stress – causes $\uparrow$ cortisol, catecholamines; produces pseudoneutrophilia.

5. Diet – lipemia after high-fat meal → turbidity → falsely ↑ concentrations.

6. Smoking – hypoxia stimulates EPO → ↑ RBC & Hb.

Summary

These notes consolidate all safety protocols, specimen handling rules, tube selections, and physiological/technical considerations essential for safe and accurate laboratory practice. Memorize hazard classes, orders of draw, tube additives, and emergency procedures to ensure compliance and high-quality test results.