Medical Practice N5 – Comprehensive Study Notes

Specimen Collection & General Handling

• Pathologist evaluates results sent by medical technologist / practitioner; may also examine patient directly.
• Medical secretary must ensure:
  • Correct container/holder for each specimen.
  • Correct volume filled.
  • Minimum label data: Doctor’s name, patient’s name, date, required tests.
  • Extra data (personal details, medical-fund no.) may accompany form.
• For bacteriology:
  • Use sterile, airtight container.
  • Deliver ASAP; if delayed, pack on ice.
• Keep adequate stock of specimen containers in surgery.

Routine Specimens & Collection Techniques

• Blood: see Chapter 1 (venepuncture details later).
• Urine:
  • Mid-stream, clean-catch sample; first part voided to flush urethra.
  • Send to surgery/lab promptly; if taken on site, follow same mid-stream rule.
  • Troubleshooting inability to void: run tap, turn on subconscious facilitators, reassure patient (friendly, positive secretary is vital).
• Cerebrospinal fluid (CSF):
  • Obtained by lumbar puncture between 3rd & 4th lumbar vertebrae while patient bends forward.
  • Collect 3 sterile tubes:
  1. Microbiological exam.
  2. Haematological exam.
  3. Chemical exam.
• Faeces:
  • Special container with spoon; home collection, deliver quickly to avoid drying.
  • Spoon-full is sufficient.
• Swabs ("deppers") for bacteriology:
  • Throat, vagina, rectum, abscess (lift scab, swab pus beneath).
  • Place in dry transport holder or reach lab immediately.
• Tissue specimens (biopsies/autopsies):
  • Taken in surgery/autopsy with biopsy needle.
  • Fixed, cut, processed, stained, microscopically examined.

Side-Room / Qualitative Tests

• Provide rapid presence/absence; positives followed by full lab tests.

Urine Routine Analysis

• Colour variations & causes:
  • Colourless: dilution/diabetes.
  • Milky: pus, albumin, fats.
  • Orange: certain drugs/dyes.
  • Red: beetroot pigments or bleeding (e.g., bilharzia).
  • Green/yellow: jaundice, phenol poisoning, methylene blue.
  • Dirty blue-green: decay, typhus/cholera, methylene blue.
  • Dark brown–black: concentrated urine, gall, hemoglobinuria, Blackwater fever.
• pH:
  • Tested with litmus/pH paper.
• Specific Gravity (SG):
  • Normal 1.010–1.025.
  • High/low suggests renal concentrating defects.
  • Measured with urinometer; spin gently to avoid wall adhesion.
• Chemical strip tests usually check: protein (albumin), blood, glucose, bilirubin, ketones.

Sediment Microscopy

• After centrifuging 10 ml at 1000–1500\,\text{rpm} for 4–5 min.
• Examine drop under 40\times objective for:
  • Crystals: sodium urate, calcium oxalate/sulfate/carbonate, ammonium urate, cholesterol.
  • Casts, RBCs, WBCs, renal epithelial cells, mucus threads, bacteria, parasites (e.g., Trichomonas), sperm, air bubbles, fibres.

Stool Examination

• Normal: brown, consolidated.
• Abnormalities: very hard, very soft.
• Look for occult blood, parasites (tapeworm segments, ova, hookworm, etc.).
• Mix small portion with saline on slide; cover-glass; microscope.

Human Defensive Boundaries

1. Superficial (mechanical, microbial & chemical):
   • Intact skin/mucosa, mucus + cilia, urine flushing.
   • Normal flora produce antibacterial substances & compete for nutrients (e.g., vaginal Lactobacillus --> lactic acid).
   • Chemical factors: fatty acids in sebum toxic to fungi, lysozyme in tears, gastric HCl lethal to most bacteria.
2. Cellular (phagocytic):
   • Neutrophils & macrophages increase during infection; attracted chemotactically.
   • Phagocytosis enhanced by opsonization (antibodies/complement coat pathogen).
   • Some pathogens survive inside leucocytes.
3. General non-specific resistance varies with species, race, individual health.

Immunity

• Antigen: foreign substance provoking specific antibody.
• Antibody = immunoglobulin (IgG, IgA, IgM, IgD, IgE).
  • IgA: local (mucosal) short-lived.
  • IgE: allergy.
  • IgM: first exposure, large, can’t cross placenta.
  • IgG: later, long-lived, crosses placenta.
• Antigen–antibody binding causes agglutination, precipitation, neutralization.

Types of Acquired Immunity

Allergic Reactions

• IgE binds mast cells/basophils; upon re-exposure releases histamine & serotonin → vasodilation, bronchoconstriction.
• Severe = anaphylactic shock; treat with antihistamines, adrenaline, oxygen.
• Desensitization possible via graded immunization.
• Medic-Alert program: IDs for allergy/condition (penicillin, tetanus antitoxin, diabetes, epilepsy, etc.).

Rh Problem (Erythroblastosis Foetalis)

• Rh- mother × Rh+ father → Rh+ foetus.
• Foetal RBCs enter maternal circulation at delivery/trauma → mother forms anti-Rh IgG.
• Subsequent Rh+ pregnancies: IgG crosses placenta → haemolysis, jaundice (bilirubin), anaemia; may be fatal.
• Prevention: administer anti-Rh (Rho(D) immune globulin) within \le 72\,\text{h} after delivery; monitor antibody titres during pregnancy.
• Treatment newborn: exchange transfusion, phototherapy (UV) for physiologic vs. pathological jaundice.

Sterilization & Disinfection

• Sterilization = complete destruction of all life.

Mechanical (Heat)

1. Dry heat
   • Burning (bands, syringes, lab loops).
   • Hot-air oven 160^{\circ}\text{C},\,1.5\,h (glassware, oils).
2. Moist heat / Steam under pressure
   • Autoclave 121^{\circ}\text{C},\,15\,\text{min},\,3.4\,\text{kg/cm}^2.
   • Items: instruments, bandages, culture media.
3. Filtration
   • For thermo-labile fluids (serum); membrane pores exclude microbes.

Chemical Methods

• Ethylene oxide (explosive, mixed with CO₂) & β-propiolactone (irritant, good penetration).
• Phenols & derivatives: cresol, hexachlorophene (skin antiseptic; max twice daily).
• Halogens: chlorine (water, bleaches), hypochlorites, iodine tincture / iodophores (slow release, less staining).
• Heavy-metal compounds: silver nitrate (newborn eye prophylaxis), mercurochrome, merthiolate.
• Hydrogen peroxide: strong oxidizer.
• Dye disinfectants: crystal violet, malachite green (weak).
• Quaternary ammonium compounds (QACs): effective, work at room temp & high dilution, low toxicity.
• Detergents/soaps: mechanical removal.

Radiation

• Gamma irradiation for pre-packed disposables (syringes, bandages).

Disinfection vs. Antisepsis

• Disinfection: kills majority on objects.
• Antiseptic: safe on living tissue; often less potent.
• Ideal disinfectant traits: broad-spectrum, active at room temp & low conc, non-toxic, soluble, non-irritant, long-acting, cheap, pleasant smell (no single agent meets all).

Haematology

Skin Prick Collection

• Sites: palmar finger tip, ear lobe, heel (infant), big toe.
• Avoid: oedematous, cyanotic, scarred, traumatized, calloused areas.
• Instruments: sterile disposable lancet, automatic lancet, Hagedorn needle, No.12 scalpel. Avoid blunt/rusted pins.

Venipuncture

• Common vein: median cubital.
• Clean with 70\% isopropyl alcohol.
• Use tourniquet above elbow.
• Vacutainer system: colour-coded plugs, evacuated tubes with/without anticoagulant.
• Secretary duties: prepare equipment, ID forms, correct tubes, accurate labelling, timely dispatch, match forms & tubes, maintain communication.
• Universal precautions: risk of hepatitis B; use autoclaved or gamma-irradiated equipment.

Complete Blood Count (CBC)

1. RBC count / Haematocrit.
2. WBC count (total & differential).
3. Haemoglobin.

Counting Chamber (Improved Neubauer)

• Grid: 9 mm²; corner large squares for WBCs (L-areas), central for RBCs (E-areas).
• RBC dilution:
  • Blood to 0.5 mark + diluent to 101 = 1:200.
• Count formula: \text{RBC}\,/\,\text{mm}^3 = \frac{\text{cells counted} \times 20\,000}{\text{areas counted}}.
• WBC dilution:
  • 0.5 to 11 mark \Rightarrow 1:20.
  • Formula: \text{WBC}\,/\,\text{mm}^3 = \text{cells counted} \times 50.

Haemoglobin (Sahli method)

• 20\,\text{mm} blood + HCl; dilute to match colour standard.
• Read \text{g}/100\,\text{ml}.
• Normal: men 14–18, women 12–16.

Differential Count

• Thin smear, air-dry, Giemsa/Wright stain 5 min.
• Count 100 WBCs under \times 40–100:
  • Neutrophils 60–70\%.
  • Lymphocytes 20–35\%.
  • Monocytes 2–8\%.
  • Eosinophils 1–5\%.
  • Basophils 0–1\%.

Haematocrit / Packed Cell Volume (PCV)

• Micro-method: capillary tube ¾ full, seal, centrifuge; read %.
• Normal: men 40–50\%, women 37–47\%.

ESR (Erythrocyte Sedimentation Rate)

• Venous blood with anticoagulant; measure fall of cells per hour.
• Normal: men 0–9\,\text{mm/h}, women 0–15\,\text{mm/h}.
• Elevated with ↑fibrinogen or globulins (infection, inflammation); used for monitoring TB, rheumatoid arthritis, etc.

Other Routine Blood Tests

• Prothrombin time.
• Coombs (Rh factor).
• Jaundice index.
• Blood glucose (hyper/hypo-glycaemia).
• Cholesterol levels.

Pharmacology Basics

• Drug/medicine/pharmaceutical preparation used for prevention, diagnosis, cure, symptom relief.
• Pharmacy = preparation & dispensing.
• Continuous research introduces new drugs.
• Classification: chemical structure, effect, legal schedule.

Nomenclature

• Generic (international non-proprietary), Brand (trade), Chemical.
  • Example: Generic zidovudine; Brand Retrovir; Chemical 3-azido-3-deoxythymidine.

South African Scheduling (similar principles elsewhere)

• Schedule 1: sold by licensed persons >16 yrs.
• Schedule 2: pharmacist without prescription (>16 yrs needs Rx).
• Schedule 3: pharmacist needs written Rx; must record.
• Schedule 4: verbal order allowed, written within 7 days.
• Schedule 5: psychotropic; limited repeats, intervals specified.
• Schedule 6: strict regulation/recording.
• Schedule 7: habit-forming narcotics; high control.
• Schedules 8–9: research/analytical only; Director-General permit.
• Schedule drugs stored in locked steel cabinet; doctor/chemist responsible for register & balance.

Dosage Forms (External)

• Ointment (oil base), Cream (water base): epidermic, endodermic, diadermic categories.
• Emulsions: shaken mixtures of immiscible liquids.
• Powders: dry surfaces; can carry chemicals/antibiotics.
• Pastes/Plasters: protective/lubricant layers.
• Antiseptic fluids: skin/wound disinfection.

Dosage Forms (Internal)

• Tablets (mouth/buccal, sublingual, enteric-coated, timed-release).
• Capsules (gelatine shells, time-release variants).
• Mixtures/Syrups: water-alcohol or sugar solutions with flavour.
• Fluid extracts/Tinctures.
• Suppositories (rectal, vaginal), pessaries.
• Injections: ampoules or powder + solvent.

Routes of Administration

1. Oral.
2. Inhalation.
3. Instillation (ear, eye, nose).
4. Rectal.
5. Vaginal.
6. Topical (skin, mucous membranes).
7. Poultice/unction.
8. Parenteral injections:
   • Intracavitary (pleural, cardiac, peritoneal).
   • Intracutaneous.
   • Subcutaneous.
   • Intramuscular.
   • Intravenous.
   • Intrathecal.
   • Intra-articular.

Reasons for Injection Use

• Rapid effect.
• Drug destroyed in GIT or patient unable to take orally.
• Localized reaction required.

Hazards of Injection

• Infection, nerve/vein injury, broken needle, shock, abscess from poor sterilization.

Therapeutic Categories (Select Examples)

• Analgesic: pain relief.
• Anaesthetic: temporary loss of sensation.
• Antacid: neutralize stomach acid.
• Antibiotic: kill/inhibit bacteria (natural or biosynthetic).
• Antispasmodic: reduce smooth-muscle spasm, secretions.
• Antidepressant: elevate mood.
• Antidiabetic: manage blood glucose.
• Antidote: counter poison.
• Antihistamine: oppose histamine effects.
• Astringent: contract tissue, reduce discharge (e.g., alum).
• Biologicals: antigen, antitoxin, toxoid (formalin-treated toxin for immunization).
• Cathartic/laxative/purgative: promote bowel evacuation (irritant, lubricant, bulk agents).
• Depressant: lessen activity (sedatives, hypnotics).
• Diuretic: increase urine output.
• Emetic: induce vomiting.
• Expectorant: aid sputum ejection.
• Haemostatic: arrest bleeding (promote clotting).
• Cardiac stimulants: increase heart action (digitalis, caffeine, adrenaline).

Habit-Forming / Controlled Drugs

• Act on central nervous system; risk of dependence, physical & mental degeneration.
• Strict manufacturing, dispensing & record-keeping requirements.
• Prescription must include:
  • Doctor’s name/address, date, patient details.
  • Drug name, strength, quantity, directions, refills.
  • Doctor’s signature & qualification.
• Pharmacists keep records; drugs in locked cabinet; report thefts to police.

End of Notes