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Basics of Surgery - Medical Student Overview

Sources: Bailey and Love's Short Practice of Surgery (28th ed.), Schwartz's Principles of Surgery (11th ed.), Mulholland & Greenfield's Surgery (7th ed.), Pye's Surgical Handicraft (22nd ed.)

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1. Surgical Terminology & Wound Classification

• Primary intention (1st intention): Wound edges are approximated immediately (e.g., surgical incision closed with sutures). Clean wounds with no tissue loss. Best cosmetic outcome.
• Secondary intention (2nd intention): Wound left open, heals by granulation tissue formation from the base upward. Used for infected or heavily contaminated wounds.
• Tertiary / Delayed primary intention: Wound left open initially, then closed 4-5 days later after infection risk decreases (e.g., perforated bowel repair).

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2. Phases of Wound Healing

Phase 1 - Hemostasis (minutes to hours)

• Injured vessels constrict; platelets adhere to exposed collagen via GP Ia/IIa complex
• Platelet aggregation forms a primary platelet plug; coagulation cascade activates -> fibrin clot
• Platelets release PDGF, TGF-β, VEGF - signaling molecules that drive subsequent healing
• The fibrin clot serves as a scaffold for migrating inflammatory cells

Phase 2 - Inflammation (days 1-4)

• PMNs (neutrophils) are the first cells recruited, peaking at 24-48 hours; they phagocytose bacteria/debris and release cytokines (TNF-α, IL-1)
• Macrophages (from monocytes) dominate by 48-96 hours - they are essential to healing; they release TGF-β, VEGF, IGF, EGF to regulate proliferation, matrix synthesis, and angiogenesis
• T-lymphocytes peak at ~1 week; CD8+ suppressor cells downregulate healing (their depletion enhances healing), while CD4+ helpers have minimal direct effect
• Clinical signs: redness, warmth, swelling, pain around wound

Phase 3 - Proliferation (days 4-12)

• Fibroblasts migrate in (chemotaxis by PDGF) -> proliferate -> synthesize collagen (types I and III) and extracellular matrix
• Lactate accumulation (~10 mmol) in the wound potently regulates collagen synthesis via ADP-ribosylation
• Angiogenesis: endothelial cells form new capillaries under VEGF, TNF-α, TGF-β stimulation
• Re-epithelialization: keratinocytes migrate from wound edges and skin appendages
• Wound contraction occurs via myofibroblasts (transformed fibroblasts)

Phase 4 - Maturation & Remodeling (weeks to 1 year)

• Collagen remodels: type III collagen is replaced by stronger type I collagen
• Collagen cross-linking increases wound tensile strength
• Maximum wound tensile strength = 80% of unwounded skin (never reaches 100%)
• Excess collagen deposition -> hypertrophic scar (stays within wound margins) or keloid (extends beyond wound margins, more common in dark skin, deltoid/presternal regions)

• Local: infection, foreign body, ischemia, radiation, poor technique
• Systemic: diabetes, malnutrition (esp. Vitamin C, zinc), corticosteroids, chemotherapy, jaundice, uremia, advanced age

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3. Surgical Asepsis & Infection Prevention

• Autoclaving (steam under pressure): 134°C for 3 min or 121°C for 15 min - gold standard for heat-stable instruments
• Dry heat: 160°C for 60 min - for heat-stable items damaged by moisture
• Ethylene oxide gas: For heat-sensitive instruments (scopes, plastics)
• Gamma irradiation: Industrial sterilization of single-use items

• Prophylactic antibiotics given within 60 minutes before incision (30 min for vancomycin)
• Hair removal with clippers (not razor shaving) if needed
• Maintain normothermia, normoglycemia intraoperatively
• Gentle tissue handling; avoid dead space and haematomas

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4. Preoperative Assessment & Preparation

• Treat respiratory infections; avoid elective surgery during acute illness
• Stop smoking 3 weeks preoperatively to reduce bronchial hypersecretion
• Carious teeth removed 3 weeks before (risk of lung abscess from dental sepsis)
• Obese patients encouraged to diet/lose weight before elective surgery
• Physiotherapy teaching of breathing exercises preoperatively

• Clear fluids: 2 hours before
• Breast milk: 4 hours before
• Solids/formula/cow's milk: 6 hours before

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5. Surgical Instruments & Sutures

Suture Classification

• Natural: Plain catgut (absorbed in 7-10 days), Chromic catgut (absorbed in 21 days)
• Synthetic: Vicryl (polyglactin), Dexon (polyglycolic acid), PDS (polydioxanone) - longer absorption, less tissue reaction, preferred

• Braided (silk, braided nylon): easier to handle and knot, tension adjustable - but cause drag and may cause stitch abscess via capillary action
• Monofilament (nylon, polypropylene/Prolene): less tissue reaction, less drag - but harder to knot and tension harder to adjust

• Cutting needles - for skin
• Round-bodied needles - for bowel, muscle, deep layers
• Fine slim-line cutting needles for facial work (4/0 suture)
• 3/0 gauge on stout cutting needle for most minor surgical procedures

• Staples: Fast; avoid on face and hands
• Adhesive strips (Steri-strips): Painless; useful for small superficial lacerations
• Tissue glue (cyanoacrylate): Clean lacerations with good apposition

Basic Instruments

• Needle holder (e.g., Gillies combined needle holder/scissors)
• Retractors: Catspaw retractors, skin hooks
• Haemostatic forceps: Mosquito/artery forceps
• Scissors: Mayo scissors (curved), Metzenbaum scissors (tissue dissection)
• For abscesses: Sinus forceps, Volkmann spoon

Drains

• Corrugated (open) drains - passive, drain by gravity
• Closed suction drains (Redivac, Jackson-Pratt) - fine perforated plastic tubes connected to negative-pressure reservoir; reduce infection risk

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6. Postoperative Care & Complications

Immediate (0-24 hours)

• Airway: Ensure muscle relaxants fully reversed; suction upper airways clear before extubation
• Oxygen: Give routinely after major surgery to counteract arterial desaturation
• Analgesia: Adequate pain control enables deep breathing; narcotics given judiciously (respiratory depression risk)
• "Stir-up" regime: Patient encouraged to breathe deeply, cough, and move every hour

Common Postoperative Complications by Timing

"The 4 Ws" of Postoperative Fever (mnemonic)

• Wind (day 1-2): Atelectasis/pneumonia
• Water (day 3-5): UTI
• Wound (day 5-7): Surgical site infection
• Walking (day 5+): DVT/PE

DVT/PE Prevention

• Early mobilisation
• TED stockings
• LMWH (low molecular weight heparin) prophylaxis
• Hydration

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7. Shock in Surgical Practice

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8. Surgical Anatomy Principles

• Langer's lines (relaxed skin tension lines): Incisions made along these lines produce least tension and best scars
• Anatomical planes: Surgeons work in tissue planes (e.g., fascial planes) to minimize blood loss and identify structures
• Surgical triangles & landmarks: e.g., Triangle of Calot (cystic artery, cystic duct, hepatic duct), Hesselbach's triangle (inguinal hernias)
• Nerve identification: Preserving motor/sensory nerves (e.g., facial nerve in parotid surgery, recurrent laryngeal nerve in thyroid surgery)

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Quick Exam Summary

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