I have extensive material now. I have enough information from Sabiston covering: hemostasis, electrosurgery (monopolar/bipolar), ultrasonic dissectors, wound closure, sutures, knots, drains, skin preparation, antisepsis, sterilization, and surgical site infections. Let me now compile comprehensive exam notes from all the gathered content.
General Surgery: Principles & Instruments — University Exam Notes
Sources: Sabiston Textbook of Surgery (Sabiston), Mulholland & Greenfield's Surgery, Schwartz's Principles of Surgery
1. ASEPSIS & STERILISATION
Definitions
| Term | Definition |
|---|
| Asepsis | Prevention of microbial contamination of living tissue or sterile materials |
| Antisepsis | Application of antiseptic agents to living tissue to kill/inhibit microorganisms |
| Sterilisation | Complete destruction of all microorganisms including spores |
| Disinfection | Destruction of most pathogens but not necessarily all spores |
Methods of Sterilisation
| Method | Details | Used For |
|---|
| Autoclaving (steam under pressure) | 134°C for 3 min or 121°C for 15 min; most reliable | Metal instruments, drapes, gowns |
| Dry heat | 160°C for 1 hour | Oils, powders, glass |
| Ethylene oxide (EtO) gas | Cold sterilisation; penetrates packaging; toxic residue must be aerated | Plastics, scopes, rubber |
| Formaldehyde / glutaraldehyde | Chemical soaking; 2% glutaraldehyde (Cidex) for 10 hrs = sterilisation | Flexible endoscopes |
| Gamma irradiation | Industrial sterilisation | Disposable surgical items |
| Plasma (H₂O₂) — Sterrad | Low-temperature; used for heat-sensitive items | Cameras, laparoscopic instruments |
Skin Antiseptic Agents
| Agent | Notes |
|---|
| Chlorhexidine-alcohol (ChloraPrep) | Preferred — persistent action, effective against Gram+ and Gram−; avoid mucosal surfaces |
| Povidone-iodine (Betadine) | Broad spectrum; inactivated by blood/organic material |
| Iodine povacrylex + isopropyl alcohol (DuraPrep) | Comparable to ChloraPrep; single-step application |
| Alcohol (isopropyl/ethyl) | Rapid-acting; no residual effect |
Key exam point: Chlorhexidine-alcohol reduces SSI compared with povidone-iodine in clean-contaminated surgeries (9.5% vs 16.1%). Alcohol-containing solutions should NOT be used on mucous membranes. — Sabiston
Surgical Site Infection (SSI) Classification
| Class | Definition | SSI Risk |
|---|
| Clean (Class I) | No inflammation, no viscus opened | <2% |
| Clean-contaminated (Class II) | Viscus opened under controlled conditions | 5–15% |
| Contaminated (Class III) | Acute inflammation, gross spillage | 15–30% |
| Dirty/infected (Class IV) | Established infection, perforated viscus | >30% |
Antimicrobial Prophylaxis
- First-line: Cefazolin 2 g IV (3 g if patient ≥120 kg) within 60 min of incision; redose every 4 hours
- Penicillin-allergic: Clindamycin 900 mg + Gentamicin
- Colorectal surgery: add Metronidazole 500 mg
- Hair removal: clipper only — shaving increases SSI risk
2. SURGICAL INSTRUMENTS
Categories of Surgical Instruments
A. Cutting & Dissecting Instruments
| Instrument | Use |
|---|
| Scalpel (Bard-Parker) | Primary incision; size 10 blade for skin, size 15 for fine work, size 11 for stab incisions |
| Scissors | Mayo scissors (heavy, dissection), Metzenbaum scissors (fine dissection), iris scissors (ophthalmic/fine), curved/straight variants |
| Diathermy / Electrosurgical unit (ESU) | Cutting and coagulation |
B. Grasping & Holding Instruments
| Instrument | Use |
|---|
| Tissue forceps (dissecting forceps) | Toothed (Adson, rat-tooth) — hold skin/tough tissue; Non-toothed (Russian, DeBakey) — bowel, vessels |
| Babcock forceps | Atraumatic; bowel, fallopian tube |
| Allis forceps | Hold fascia, intestine; slightly traumatic |
| Sponge-holding forceps (ring/sponge forceps) | Swabbing, packing, holding gauze |
C. Clamping & Occluding Instruments
| Instrument | Use |
|---|
| Haemostat (Halsted mosquito) | Fine vessels; small bites |
| Kelly / Crile clamp | Larger vessels, haemostasis |
| Kocher (Rochester-Ochsner) clamp | Cross-serrated teeth; tough/fibrous tissue; do NOT use on bowel |
| Intestinal clamps (Dennis, Doyen) | Non-crushing; bowel occlusion |
| Intestinal crushing clamps (Payr) | Crushing clamp for bowel resection |
| Vascular clamps (Satinsky, DeBakey) | Partial or complete occlusion of blood vessels |
D. Retracting Instruments
| Instrument | Use |
|---|
| Langenbeck retractor | Hand-held; general retraction |
| Deaver retractor | Liver, deep abdominal retraction |
| Balfour retractor | Self-retaining; abdominal surgery |
| Finochietto retractor | Self-retaining; chest |
| Weitlaner / Gelpi retractor | Self-retaining; small wounds |
| Ring retractor (Bookwalter) | Modular self-retaining; pelvic/deep surgery |
E. Suturing Instruments
| Instrument | Use |
|---|
| Needle holder (Mayo-Hegar, Webster) | Hold needles; blunt smooth jaws — Mayo for heavy sutures, Webster for fine |
| Castroviejo needle holder | Ophthalmic/microsurgery |
F. Dilating & Probing Instruments
| Instrument | Use |
|---|
| Bougies / dilators | Oesophageal/urethral dilatation |
| Probes (Bowman, lacrimal) | Probing fistulae, ducts |
G. Suction Instruments
| Instrument | Use |
|---|
| Yankauer (tonsil sucker) | Oropharyngeal suction |
| Poole sucker | Abdominal/peritoneal cavity suction |
| Frazier sucker | Neurosurgery/fine field |
3. HAEMOSTASIS
"Meticulous dissection and intimate knowledge of surgical anatomy are mandatory for minimisation of intraoperative blood loss. Surgical bleeding obscures the operative field, prolongs operating time, induces coagulopathy." — Sabiston
Methods of Haemostasis
A. Mechanical
- Direct pressure — initial control
- Ligation (ties): vessels <1 mm → monopolar diathermy alone sufficient; vessels >1 mm → ligation required. Named vessels → suture ligation
- Suture ligation (transfixion): large vessels; prevents tie slipping
- Clips (titanium/polymer): applied with clip applier; used in laparoscopic surgery
- Staples: skin, bowel, vessels
- Tourniquets: limb surgery
- Bone wax: cancellous bone bleeding
B. Thermal (Electrosurgery)
Monopolar Electrosurgery
- Current passes from active electrode → through patient → to dispersive (grounding) plate → back to generator
- Cutting mode: continuous low-voltage high-frequency current → rapid cell heating → vaporisation
- Coagulation mode: interrupted high-voltage current → desiccation
- Blend mode: mixture of cut + coag
- Complications: burns at dispersive plate site, interference with pacemakers, arcing to adjacent structures
- Contraindicated near pacemaker/ICD without precautions
Bipolar Electrosurgery
- Current passes only between the two tips of the instrument (forceps)
- Limited lateral thermal spread — safer near nerves/vessels
- Cannot cut — only coagulates
- Used in neurosurgery, microsurgery, vasectomy
Advanced Energy Devices
| Device | Mechanism | Feature |
|---|
| LigaSure (vessel sealing) | Bipolar RF + pressure — denatures collagen/elastin | Seals vessels up to 7 mm; burst pressure >500 mmHg |
| Harmonic Scalpel (ultrasonic) | 55,500 Hz vibration → frictional heat (80°C) | Cuts + coagulates; less smoke; less lateral thermal spread than monopolar |
| THUNDERBEAT | Combined ultrasonic + bipolar | Fastest sealing |
C. Chemical / Topical Haemostatic Agents
| Agent | Mechanism |
|---|
| Oxidised regenerated cellulose (Surgicel) | Absorbs blood; mechanical tamponade; antimicrobial |
| Gelatin foam (Gelfoam) | Absorbs blood; mechanical; resorbed in 4–6 weeks |
| Thrombin (bovine/recombinant) | Converts fibrinogen → fibrin directly |
| Fibrin glue (Tisseel) | Thrombin + fibrinogen + factor XIII + Ca²⁺ → fibrin clot |
| Bone wax (beeswax) | Physical tamponade of cancellous bone |
| Tranexamic acid | Antifibrinolytic; systemic or topical |
4. SUTURES
Suture Classification
By Absorbability
| Type | Examples | Absorption Time | Use |
|---|
| Absorbable (natural) | Catgut (plain), Chromic catgut | Plain: 7–10 days; Chromic: 21 days | Bowel, subcutaneous |
| Absorbable (synthetic) | Vicryl (polyglactin 910), Dexon (polyglycolic acid), PDS (polydioxanone), Monocryl (poliglecaprone) | Vicryl: 60–90 days; PDS: 180–200 days | All layers; PDS for abdominal closure |
| Non-absorbable (natural) | Silk, Linen | Encapsulated but not resorbed | General; but high tissue reaction |
| Non-absorbable (synthetic) | Nylon (Ethilon), Prolene (polypropylene), Ethibond (polyester), PTFE (Gore-Tex) | Permanent | Skin, vascular anastomosis, hernia |
By Structure
| Type | Examples | Properties |
|---|
| Monofilament | Nylon, Prolene, PDS, Monocryl | Low drag, low infection risk, difficult to knot |
| Multifilament (braided) | Vicryl, Silk, Ethibond | Easy to handle, better knot security, higher infection risk (capillarity) |
| Twisted | Catgut, linen | Natural fibre structure |
Suture Sizes
- USP scale: 5-0 (finest) → 2 (heavy); #1, #2 are thicker still
- Metric system: gauge in 0.1 mm increments
Types of Suture Techniques
| Technique | Features |
|---|
| Interrupted | Each suture individual; failure of one doesn't compromise whole line; more time-consuming |
| Continuous (running) | Faster; distributes tension; if one breaks — whole line fails |
| Subcuticular (intradermal) | Running stitch in dermis; cosmetic closure; no marks |
| Mattress (horizontal/vertical) | Inverts or everts wound edges; strong; reduces dead space |
| Purse-string | Circles opening (e.g., appendix stump, anastomosis) |
| Figure-of-8 | Strong, haemostatic |
Knots
- Reef (square) knot: standard; two throws in opposite directions
- Surgeon's knot: first throw doubled → less slippage during second throw
- Granny knot: incorrect — same direction both throws; weak, slips
- Rule: minimum 3 throws for synthetic monofilament; 2 sufficient for braided
- Instrument tie vs. hand tie
Needles
| Feature | Options |
|---|
| Point | Cutting (reverse cutting, conventional cutting) — skin/tough tissue; Round body (tapered) — viscera, vessels |
| Shape | ½ circle, ⅜ circle, straight, J-needle |
| Body | Swaged (atraumatic, fused to suture) vs. eyed (traumatic) |
5. ELECTROSURGERY (DIATHERMY) — Detail
Principles
- Uses high-frequency alternating current (>100,000 Hz) — avoids neuromuscular stimulation
- Heat generated = I² × R × t (current², resistance, time)
- Tissue effects depend on power density (current density) and waveform
Monopolar Circuit
Generator → Active electrode (tip) → Patient tissue → Dispersive plate → Generator
- Dispersive (return) electrode must be large surface area to avoid burns at plate site
Electrosurgical Hazards
- Capacitive coupling: current transfer through intact insulation to adjacent tissue (laparoscopic)
- Direct coupling: active electrode contacts another instrument
- Insulation failure: current escapes through defect in laparoscopic instrument
- Alternate site burns: current returns via alternative pathway (ECG electrodes)
- Pacemaker/ICD: use bipolar or short bursts of monopolar away from device; use magnet
6. WOUND HEALING & CLOSURE
Phases of Wound Healing
| Phase | Timing | Key Events |
|---|
| Haemostasis | Immediate (0–minutes) | Platelet plug, coagulation cascade, fibrin clot |
| Inflammatory | 0–5 days | Neutrophils (0–48 h), macrophages (2–5 days); débridement, growth factors |
| Proliferative | 3 days–3 weeks | Fibroblasts, collagen III → I conversion, angiogenesis, granulation tissue, epithelialisation |
| Remodelling (maturation) | 3 weeks–2 years | Collagen crosslinking; tensile strength returns to 80% maximum |
Wound tensile strength reaches only 80% of normal tissue strength — Sabiston
Types of Wound Closure
| Method | Indication |
|---|
| Primary intention (1° closure) | Clean wound, low contamination; immediate closure |
| Secondary intention | Contaminated/infected wound; left open to granulate |
| Tertiary (delayed primary closure) | Contaminated wound closed 4–5 days later once clean |
Wound Closure Materials
| Material | Type | Use |
|---|
| Sutures | Absorbable/non-absorbable | Universal |
| Staples | Skin staples | Rapid skin closure, linear wounds |
| Adhesive strips (Steri-strips) | Tape | Low-tension superficial wounds |
| Tissue adhesive (Dermabond/2-octyl cyanoacrylate) | Glue | Paediatrics, cosmetic, superficial lacerations |
Wound Drains
| Type | Mechanism | Examples |
|---|
| Open (passive) | Gravity/capillary; relies on pressure differential | Corrugated rubber drain, Penrose drain |
| Closed (active suction) | Negative pressure prevents contamination | Jackson-Pratt (JP), Blake drain, Redivac |
| Closed (passive) | Underwater seal | Intercostal chest drain |
Drain indications: dead space obliteration, anticipated fluid collections (bile, lymph, serum), anastomotic protection, abscess drainage
Drain removal: when output <30 mL/24h for 2 consecutive days (general principle)
7. PREOPERATIVE ASSESSMENT & SURGICAL RISK
ASA Physical Status Classification
| Class | Definition |
|---|
| ASA I | Normal healthy patient |
| ASA II | Mild systemic disease |
| ASA III | Severe systemic disease |
| ASA IV | Severe systemic disease — constant threat to life |
| ASA V | Moribund; not expected to survive without operation |
| ASA VI | Brain-dead; organ donor |
Cardiac Risk Assessment
- Revised Cardiac Risk Index (RCRI/Lee Index): 6 factors — ischaemic heart disease, CHF, cerebrovascular disease, diabetes on insulin, creatinine >2.0 mg/dL, high-risk surgery. Score ≥3 = >10% MACE risk
- MET (Metabolic Equivalent of Task): ≥4 METs (climbing stairs, walking on flat) = adequate functional capacity
- ACC/AHA guidelines: proceed to surgery if functional capacity ≥4 METs without further testing
Nutritional Assessment
- Serum albumin <3.5 g/dL = hypoalbuminaemia → impaired wound healing, immunosuppression
- Prealbumin (transthyretin) — shorter half-life (2 days) → better acute marker of nutritional status
- SGA (Subjective Global Assessment), NRS-2002, MUST — nutritional screening tools
- Indications for preoperative nutrition: severe malnutrition (weight loss >10–15%, albumin <3 g/dL) — 7–14 days of enteral/parenteral support before elective surgery
8. SURGICAL APPROACHES & INCISIONS
Common Abdominal Incisions
| Incision | Description | Use |
|---|
| Midline (median laparotomy) | Through linea alba; bloodless; rapid entry; weak | General access, emergency laparotomy |
| Paramedian | 2.5 cm lateral to midline; through rectus sheath | More secure closure; less popular now |
| Kocher (subcostal) | Oblique below costal margin | Open cholecystectomy, splenectomy |
| Pfannenstiel | Transverse suprapubic | Gynaecological, caesarean |
| Gridiron (McBurney's) | Muscle-splitting at McBurney's point | Appendicectomy |
| Lanz | Transverse variant of gridiron; better cosmesis | Appendicectomy |
| Rooftop (chevron) | Bilateral subcostal | Oesophagogastrectomy, liver transplant |
| Thoracoabdominal | Extends into chest | Oesophagus, aorta |
9. LAPAROSCOPIC SURGERY — PRINCIPLES
Pneumoperitoneum
- CO₂ used: non-combustible, rapidly absorbed, cheap
- Intraperitoneal pressure maintained at 12–15 mmHg
- Entry techniques: Veress needle (closed — blind) vs. Hasson technique (open — cut-down, safer)
- Physiological effects: ↑ intrathoracic pressure, ↓ venous return, ↑ PaCO₂, shoulder-tip pain (phrenic nerve irritation from CO₂)
Trocar Types
- Pyramidal (cutting) tip: sharp, for dense abdominal wall
- Dilating (conical) tip: less bleeding, fascial defect closes better
- Bladeless (optical): visualise entry layer by layer
Advantages of Laparoscopy
- Reduced pain, shorter hospital stay, faster return to work, reduced SSI, fewer adhesions, better cosmesis
Disadvantages
- Loss of tactile feedback, steep learning curve, risk of trocar injuries, gas embolism, port-site hernia
10. DIATHERMY — QUICK REVISION TABLE
| Feature | Monopolar | Bipolar |
|---|
| Current path | Active tip → through patient → plate | Between two tips only |
| Cutting | Yes | No |
| Coagulation | Yes | Yes |
| Lateral spread | More | Less |
| Safe near pacemaker? | Caution needed | Safer |
| Safe near nerves? | Caution | Preferred |
11. KEY EXAM MNEMONICS
Wound Infection Risk Factors — "ABCDE"
- A — Age (elderly)
- B — Blood supply (poor perfusion)
- C — Contamination (wound class)
- D — Diabetes / Drugs (steroids, immunosuppressants)
- E — Existing infection / Elsewhere (remote site infection)
Suture Absorbability Memory
- "COPS are Permanent": Catgut, (chromic) catgut are natural-absorbable; Prolene, nylon = synthetic permanent
- "Vicryl PDS Monocryl" = synthetic absorbable
Haemostasis Methods — "PLTCB"
- Pressure, Ligation, Thermal (diathermy), Chemical (agents), Bone wax
SUMMARY QUICK-REFERENCE
| Topic | Key Points |
|---|
| Sterilisation gold standard | Autoclaving (steam under pressure) |
| Best skin prep | Chlorhexidine-alcohol |
| SSI prophylaxis | Cefazolin 2 g within 60 min of incision |
| Vessel sealing >1 mm | Ligation/clip/LigaSure |
| Harmonic scalpel temp | ~80°C; 55,500 Hz |
| Monopolar frequency | >100,000 Hz (avoids nerve stimulation) |
| Suture for abdominal closure | PDS (polydioxanone) — long-lasting absorbable |
| Wound tensile strength | Max 80% of original at full maturation |
| Laparoscopy pressure | 12–15 mmHg CO₂ |
| Safest laparoscopy entry | Hasson (open) technique |
References: Sabiston Textbook of Surgery, pp. 315–405 | Schwartz's Principles of Surgery 11e | Mulholland & Greenfield's Surgery 7e
