• Schwartz's Principles of Surgery (Nutrition in Surgery)
• Sabiston Textbook of Surgery (Wound Healing phases, factors)
• Bailey & Love's Short Practice of Surgery (Wound Healing, Surgical Infections - microbiology, SSI, abscess, necrotising fasciitis, gas gangrene)
• Multiple sources for pre/postoperative managementNow I'll compile the full comprehensive notes:

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SURGERY NOTES FOR MBBS STUDENTS

Comprehensive Revision Guide

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TOPIC 1: NUTRITION IN SURGERY

1.1 Why Nutrition Matters in Surgical Patients

• Impaired wound healing
• Increased susceptibility to infection
• Muscle wasting and weakness
• Prolonged hospital stay and recovery

1.2 Nutritional Assessment

Nutritional Scoring Tools

• NRS (Nutritional Risk Screening) - for general hospitalised patients
• NUTRIC Score (Nutrition Risk in the Critically Ill) - for ICU patients

Exam tip: Albumin < 35 g/L = hypoalbuminaemia, indicates protein malnutrition. Pre-albumin (transthyretin) has a shorter half-life (2 days vs 20 days for albumin) and is therefore a more sensitive indicator of acute nutritional status.

1.3 Metabolic Response to Surgery/Injury

• Ebb phase (0-24 hrs): reduced metabolic rate, hypoperfusion, conservation of energy
• Flow phase (days 1-5+): hypermetabolism, catabolism, negative nitrogen balance

• Males: BEE = 66.5 + (13.75 × weight kg) + (5.003 × height cm) - (6.775 × age)
• Females: BEE = 655.1 + (9.563 × weight kg) + (1.85 × height cm) - (4.676 × age)

1.4 Macronutrient Requirements

Protein Requirements

• Protein is measured via nitrogen balance: Nitrogen balance = Nitrogen in - Nitrogen out
• Positive nitrogen balance = anabolism (desired for recovery)
• Negative nitrogen balance = catabolism (seen in sepsis, major surgery, burns)
• Urine urea nitrogen (UUN) measures nitrogen excretion. Add 4g for insensible losses.

1.5 Routes of Nutritional Support

ENTERAL NUTRITION (EN) - PREFERRED

• Maintains gut mucosal integrity and barrier function
• Prevents bacterial translocation
• Cheaper and safer
• Maintains immune function (gut-associated lymphoid tissue, GALT)

PARENTERAL NUTRITION (PN / TPN)

• Non-functional GI tract
• Short bowel syndrome
• Prolonged ileus
• High-output fistulae
• Severe malabsorption

• Peripheral PN: max osmolarity ~900 mOsm/L; limited caloric density; risk of thrombophlebitis
• Central PN (TPN): via subclavian or internal jugular central line; allows hyperosmolar solutions

EXAM HIGH-YIELD: Refeeding syndrome - occurs when feeding is started after prolonged starvation. Phosphate is driven into cells by insulin, causing profound hypophosphataemia → cardiac arrhythmias, respiratory failure, encephalopathy. Prevention: start feeding slowly, supplement phosphate/potassium/magnesium.

1.6 Immunonutrition

• Glutamine: Most abundant amino acid; fuel for rapidly dividing cells (enterocytes, lymphocytes). Becomes conditionally essential in critical illness.
• Arginine: Enhances T-cell function and wound healing
• Omega-3 fatty acids (EPA/DHA): Anti-inflammatory; reduce prostaglandin E2
• Nucleotides: Support lymphocyte proliferation

1.7 Vitamins and Minerals in Surgery

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TOPIC 2: WOUND HEALING

2.1 Types of Wound Healing

Incisions are designed to lie along Langer's lines (lines of relaxed skin tension) to minimise scar formation.

2.2 Phases of Wound Healing

Phase 1: HAEMOSTASIS (Minutes)

• Vascular spasm → platelet aggregation → coagulation cascade
• Fibrin clot forms: acts as scaffold for healing
• Platelets release growth factors: PDGF (platelet-derived growth factor), TGF-β, EGF, VEGF
• Vasoconstriction then vasodilation

Phase 2: INFLAMMATORY PHASE (0-5 days)

• Characteristics: Rubor, calor, dolor, tumor (Celsus' cardinal signs)
• Increased vascular permeability (histamine, bradykinin, prostaglandins)
• Neutrophils arrive first (peak day 2): phagocytose bacteria and debris
• Macrophages arrive by day 3-4 (peak day 3): key "orchestrators" of healing - phagocytose debris, secrete cytokines (IL-1, TNF-α), recruit fibroblasts
• Lymphocytes peak at day 7

Key fact: Macrophages are the most important cells in wound healing. Depleting macrophages significantly impairs healing.

Phase 3: PROLIFERATIVE PHASE (Days 5-21)

• Fibroblasts migrate into wound, proliferate, and synthesise collagen (Types I and III)
• Initially Type III collagen (weaker), then replaced by Type I (stronger)
• Collagen synthesis requires: oxygen, vitamin C, zinc, iron, alpha-ketoglutarate

• New blood vessel formation driven by VEGF
• Creates the red, vascular appearance of granulation tissue

• Basal keratinocytes migrate across wound surface
• Stimulated by EGF and KGF (keratinocyte growth factor)
• Wound contraction: myofibroblasts contract the wound edges (most prominent in secondary healing)

Phase 4: REMODELLING/MATURATION PHASE (Weeks to years)

• Type III collagen replaced by Type I (stronger, organised)
• Wound strength increases: 20% at 3 weeks, 60% at 4 months, maximum 80% of original tensile strength (never reaches 100%)
• Wound contraction continues
• Scar remodels, fades, and matures
• Matrix metalloproteinases (MMPs) break down excess collagen

EXAM FACT: A mature scar achieves approximately 80% of the original skin tensile strength - it never fully regains pre-injury strength.

2.3 Key Growth Factors in Wound Healing

2.4 Factors Affecting Wound Healing

LOCAL FACTORS

SYSTEMIC FACTORS

2.5 Abnormal Wound Healing

Hypertrophic Scars

• Raised, erythematous, but remain within the wound borders
• Most common over flexor surfaces, shoulders, presternal area
• Regress spontaneously over months-years
• Treatment: topical silicone, intralesional corticosteroid injection, compression therapy, surgical excision

Keloid Scars

• Extend beyond the original wound borders - key differentiator from hypertrophic scars
• More common in: darker skin types, face, earlobes, deltoid, presternal region
• Appear months after injury
• More resistant to treatment, may be locally destructive
• Treatment: repeated excision + adjuvant radiotherapy, intralesional steroids, silicone sheets
• May recur after excision (higher recurrence than hypertrophic scars)

Wound Dehiscence

• Breakdown of wound closure
• Risk factors: malnutrition, obesity, infection, steroids, excessive tension, poor technique
• Burst abdomen (abdominal dehiscence): classically presents day 7-10 post-laparotomy with "salmon-pink" serosanguinous fluid discharge
• Management: return to theatre for reclosure (mass closure technique)

Wound Contracture

• Exaggerated contraction, especially across joints
• Can cause deformity and functional limitation

Chronic Wounds (Non-healing wounds)

• Stuck in the inflammatory phase
• Causes: ischaemia, infection, diabetes, venous hypertension, malignancy
• Examples: diabetic foot ulcers, venous leg ulcers, pressure sores, arterial ulcers
• "Over-granulation": excessive fragile granulation tissue → treat with silver nitrate or corticosteroid

Pyogenic Granuloma

• Rapidly growing, highly vascular nodule after minor trauma
• Bleeds easily
• Treatment: excision, laser, silver nitrate

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TOPIC 3: SURGICAL INFECTIONS

3.1 Historical Background (High-yield for vivas)

1. Organism found in every case of the disease
2. Can be isolated and grown in pure culture
3. Reproduces the disease when injected into a healthy host
4. Can be recovered from the experimentally infected host

3.2 Classification of Wounds (Altemeier Classification)

3.3 Microbiology of Surgical Infection

Gram-Positive Organisms

• Group A Streptococcus (S. pyogenes): most pathogenic; causes cellulitis, tissue destruction via streptolysin, streptokinase, streptodornase
• S. faecalis (Enterococcus): Lancefield Group D; often synergistic
• Peptostreptococcus: anaerobic streptococcus
• Treatment: penicillin, erythromycin; cephalosporins if penicillin-allergic

• S. aureus: most important; lives in nasopharynx of 15% of population; causes suppuration and abscess
• MRSA (Methicillin-Resistant S. aureus): resistant to beta-lactam antibiotics; hospital-acquired infection; treat with vancomycin or linezolid
• "Search and destroy" MRSA screening before elective surgery

Gram-Negative Organisms

Anaerobic Organisms

• Anaerobic, Gram-positive, spore-forming
• Produces enzymes: hyaluronidase, lecithinase (alpha-toxin), haemolysin
• Causes tissue necrosis in ischaemic tissue (especially amputations)
• Prophylaxis: penicillin pre-amputation

• Anaerobic, terminal spore-bearing, Gram-positive
• Produces exotoxin tetanospasmin
• Signs: trismus (lockjaw), opisthotonus, respiratory arrest, death
• Prophylaxis: tetanus toxoid vaccination
• Treatment: benzylpenicillin, muscle relaxants, mechanical ventilation in severe cases

3.4 Surgical Site Infection (SSI)

1. Superficial SSI: Skin and subcutaneous tissue only
2. Deep SSI: Fascia and muscle layers
3. Organ/Space SSI: E.g., abdominal abscess after anastomotic leak

• Endogenous: From patient's own flora (most common); e.g., skin commensals, bowel organisms
• Exogenous: From operating theatre, instruments, theatre staff

• Mechanical: intact skin, mucous membranes
• Chemical: low gastric pH (kills bacteria)
• Humoral: antibodies, complement, opsonins
• Cellular: neutrophils, macrophages, lymphocytes

3.5 Prevention of SSI

EXAM FACT: Antibiotic prophylaxis is most effective when given 30-60 minutes before surgical incision. It should not be continued >24 hours post-operatively (prophylaxis becomes treatment at that point, and promotes resistance).

3.6 Specific Surgical Infections

Abscess

• Cardinal signs (Celsus): Calor (heat), Rubor (redness), Dolor (pain), Tumor (swelling) + Functio laesa (loss of function)
• Pus = dead/dying neutrophils overwhelmed by bacterial toxins
• Predominantly S. aureus
• Principle: "Ubi pus, ibi evacua" (Where there is pus, drain it)
• 75% of SSIs present after the patient has left hospital
• Most wound abscesses take 7-10 days to form post-surgery
• Management: Incision and Drainage (I&D); no antibiotics if left open to drain

Cellulitis

• Spreading infection of the dermis and subcutaneous tissue
• Causative organism: usually Group A Streptococcus or S. aureus
• Clinical: red, hot, swollen, tender, poorly defined borders, associated lymphangitis
• Treatment: oral/IV penicillin or cephalosporins; flucloxacillin for S. aureus

Necrotising Fasciitis (Synergistic Spreading Gangrene)

• Rare but life-threatening infection spreading along deep fascia
• Polymicrobial (coliforms, staphylococci, Bacteroides, anaerobic streptococci, peptostreptococci)
• Types:
  • Type I (polymicrobial): Most common; diabetes, immunocompromised
  • Type II (Group A Strep): "Flesh-eating disease"; can affect healthy individuals
• Eponyms: Meleney's gangrene (abdominal wall); Fournier's gangrene (scrotal/perineal)
• Clinical: Severe pain (out of proportion to appearance), spreading erythema, crepitus (gas), foul smell, systemic sepsis → multiorgan failure
• Finger test: 2 cm skin incision under LA down to deep fascia; dishwater fluid + lack of bleeding = positive = necrotising fasciitis
• Management: Urgent, aggressive surgical debridement (extensive) + IV antibiotics (piperacillin-tazobactam or meropenem + metronidazole) + ICU support + hyperbaric oxygen (adjunct)
• Mortality: 20-40%

Gas Gangrene (Clostridial Myonecrosis)

• Causative organism: Clostridium perfringens
• Characteristics: gas production (crepitus on palpation), foul smell, rapidly spreading
• Occurs in devitalised/ischaemic tissue
• Most at risk: immunocompromised, diabetics, post-amputation
• Treatment: aggressive surgical debridement + high-dose IV penicillin + hyperbaric oxygen

3.7 Hospital-Acquired Infections (HAI/Nosocomial)

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TOPIC 4: PREOPERATIVE AND POSTOPERATIVE MANAGEMENT

4.1 Preoperative Assessment

Goals of Preoperative Assessment

1. Identify medical conditions that increase operative risk
2. Optimise patient's medical status before surgery
3. Obtain informed consent
4. Plan anaesthesia and analgesia
5. Prevent complications

History and Examination

• Full medical, surgical, drug, family, and social history
• Drug history (anticoagulants, antiplatelets, oral hypoglycaemics, steroids)
• Allergies
• Previous anaesthesia problems
• Exercise tolerance (functional capacity in METs)
• Cardiovascular and respiratory systems

ASA Physical Status Classification

Preoperative Investigations

Fasting Guidelines (NBM - Nil By Mouth)

• Solids and milk: Nil from midnight (or 6 hours before surgery)
• Clear fluids: Allowed up to 2 hours before anaesthesia (improves comfort, reduces anxiety, does not increase aspiration risk)
• Special considerations: Diabetic patients (risk of hypoglycaemia), emergency surgery (always assume full stomach - rapid sequence induction)

Mnemonic - "6-4-2 rule": 6 hours solids, 4 hours breast milk, 2 hours clear fluids

4.2 Specific Preoperative Considerations

Cardiovascular Disease

• Assess using Goldman Cardiac Risk Index or Lee Revised Cardiac Risk Index
• ECG changes: recent MI (< 6 weeks = very high risk), uncontrolled arrhythmia, uncontrolled HF
• Hypertension: Should be controlled preoperatively; diastolic > 110 mmHg → delay elective surgery
• Antiplatelet therapy (aspirin): Continue for cardiac stents; stop 7 days before elective surgery otherwise
• Anticoagulation (warfarin): Stop 5 days before surgery; bridge with LMWH if high thrombotic risk. Target INR < 1.5 for most procedures.
• DOACs (rivaroxaban, apixaban, dabigatran): Stop 24-48 hours before (48-72h if CrCl < 50 mL/min)

Diabetes Mellitus

• Target blood glucose: 6-10 mmol/L perioperatively (avoid hypoglycaemia and hyperglycaemia)
• Variable rate insulin infusion (VRIII/sliding scale) for major procedures or if glucose uncontrolled
• Metformin: Stop on day of surgery (risk of lactic acidosis, especially if contrast used)
• Schedule diabetics first on the operating list

Steroids

• Patients on long-term steroids have HPA axis suppression → perioperative adrenal crisis
• Steroid cover:
  • Minor surgery: Continue usual dose + 25-50 mg hydrocortisone IV at induction
  • Moderate surgery: 50 mg hydrocortisone IV at induction + 25 mg every 8h for 24h
  • Major surgery: 100 mg hydrocortisone at induction + infusion/regular doses for 24-48h then taper

Respiratory Disease

• Optimise: stop smoking (≥8 weeks preoperatively for maximum benefit), treat COPD exacerbations, physiotherapy
• Incentive spirometry to reduce postoperative pulmonary complications

Anaemia

• Optimise preoperatively: treat iron deficiency with oral/IV iron (allow 4-6 weeks for oral)
• Consider erythropoietin for elective surgery in Jehovah's Witnesses or when avoiding transfusion

DVT Prophylaxis

• Risk assessment using Caprini Score or Wells criteria
• Low molecular weight heparin (LMWH) e.g., enoxaparin
• Compression stockings (TED stockings) - measure before applying
• Intermittent pneumatic compression devices (IPC) intraoperatively
• Early mobilisation

Bowel Preparation

• Mechanical bowel prep (e.g., PEG solution, sodium picosulphate) - controversial; used selectively
• Current evidence: not routinely needed for most colorectal surgery
• Still used for left-sided colonic surgery in many centres

Consent

• Valid consent requires: capacity, information, voluntariness (no coercion)
• Must discuss: diagnosis, proposed procedure, benefits, risks (including serious and common ones), alternatives (including no treatment)
• Written consent for most surgical procedures

4.3 Intraoperative Care

4.4 Postoperative Management

Immediate Postoperative Care (Recovery Room / PACU)

• Airway management and oxygen delivery
• Vital signs monitoring: BP, HR, SpO2, temperature, RR, pain score, urine output
• Level of consciousness (GCS)
• Check surgical site for bleeding

Fluid Management

• Replace insensible losses: ~500-1000 mL/day
• Assess and replace surgical losses (haemorrhage, nasogastric drainage)
• Urine output target: > 0.5 mL/kg/hour (= adequate renal perfusion)
• Avoid over-hydration (fluid overload → pulmonary oedema, anastomotic oedema, prolonged ileus)

Analgesia (WHO Pain Ladder approach)

• Multimodal analgesia is the gold standard
• Regional blocks: epidural, nerve blocks (e.g., TAP block for abdominal surgery) - reduce opioid requirements
• NSAIDs: Avoid if: renal impairment, GI ulcers, anastomotic procedures (risk of leak), thrombocytopaenia
• PCA (Patient-Controlled Analgesia): Patient self-administers IV morphine via pre-programmed pump

Monitoring for Postoperative Complications

Classic pattern of fever post-surgery (5 W's mnemonic):

• Day 1-2: Wind (atelectasis, pneumonia)
• Day 3-5: Water (urinary tract infection)
• Day 5-7: Wound (wound infection)
• Day 5-7: Walking (DVT/PE)
• Day 7+: Wonder drug (drug fever) or Womb (in women - endometritis)

Enhanced Recovery After Surgery (ERAS)

• Preoperative: carbohydrate loading 2 hours before surgery, avoid prolonged fasting
• Intraoperative: minimally invasive approach, restrictive fluid therapy, normothermia, short-acting anaesthetics
• Postoperative: early oral feeding (within 24h), early mobilisation (day of surgery), multimodal analgesia, early catheter/drain removal

Drains

• Indications: dead space obliteration, haematoma prevention, drainage of abscess cavity, monitoring of anastomotic leak
• Types: Active (Redivac, Jackson-Pratt), Passive (Corrugated, Penrose)
• Remove when output < 30-50 mL/24h (serous fluid)
• Drains do NOT prevent anastomotic leak - they help detect it

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TOPIC 5: SURGICAL INSTRUMENTATION

5.1 Operating Theatre Environment

Theatre Zones

1. Unrestricted zone: Reception, corridors, changing rooms
2. Semi-restricted zone: Corridors adjacent to theatres, storage areas (scrubs required)
3. Restricted zone: Operating theatre itself (full theatre attire, mask, hat required)

Theatre Attire

• Theatre scrubs (clean), theatre cap/hat (covers all hair), surgical mask, clogs/boots
• Surgical team additionally: Gown (sterile), gloves (sterile), eye protection

Sterilisation Methods

Sterilisation = destruction of ALL microorganisms including spores Disinfection = destruction of most pathogens, NOT spores Antisepsis = prevention of infection by destroying/inhibiting microorganisms on living tissue

5.2 Basic Surgical Instrument Categories

1. CUTTING AND DISSECTING INSTRUMENTS

2. GRASPING AND HOLDING INSTRUMENTS (Forceps)

3. RETRACTORS

4. CLAMPING INSTRUMENTS

5. SUTURING INSTRUMENTS

6. SUTURE MATERIALS

Suture sizes: Sized by USP scale - 10-0 (finest; ophthalmic) to 1-0, 1, 2 (coarsest). Or by gauge: 3-0 for skin, 1 or 2 for mass abdominal closure.

7. WOUND CLOSURE METHODS

5.3 Diathermy (Electrosurgery)

Monopolar Diathermy

• Current passes from active electrode (surgical instrument), through patient's body, to dispersal pad (patient plate) on thigh/calf
• Cut mode: continuous sinusoidal current → vaporises cells
• Coagulation mode: interrupted current → desiccates/coagulates
• Blend mode: combination

• Burns at patient return electrode site
• Risk of stimulating neuromuscular structures
• Contraindicated near cardiac pacemakers (interfere with sensing); use bipolar instead
• Risk of stray currents in laparoscopic surgery (capacitance coupling)

Bipolar Diathermy

• Current passes between the two tips of the forceps only (very localised)
• Safer for: nerve tissue, vascular surgery, microsurgery, near pacemakers
• Cannot cut (coagulate only)

5.4 Laparoscopic Instruments

5.5 Drains

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SUMMARY / HIGH-YIELD EXAM POINTS

Mnemonics

Key Numbers to Remember

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What's Covered

Topic 1: Nutrition in Surgery

• Metabolic response to surgery (ebb and flow phases)
• Nutritional assessment tools (NRS, NUTRIC score, albumin, pre-albumin)
• Caloric and protein requirements with practical formulas
• Enteral vs parenteral nutrition - routes, indications, complications
• Refeeding syndrome (very high-yield exam topic)
• Immunonutrition (glutamine, arginine, omega-3s)
• Vitamins and minerals critical for surgical healing

Topic 2: Wound Healing

• Three types of healing (primary, secondary, tertiary intention)
• All four phases with cellular timeline (who arrives when, and why)
• Growth factors (PDGF, TGF-β, VEGF, EGF, KGF) and their sources
• Local and systemic factors impairing healing
• Abnormal healing: keloids vs hypertrophic scars (key differentiator), dehiscence, chronic wounds

Topic 3: Surgical Infections

• Altemeier wound classification with SSI risk percentages
• Microbiology: Streptococci, Staphylococci, MRSA, anaerobes, Clostridia
• Necrotising fasciitis - types, finger test, management
• Gas gangrene, tetanus
• SSI prevention bundle (antibiotic timing, skin prep, temperature, glycaemic control)
• Hospital-acquired infections (MRSA, C. difficile)

Topic 4: Pre/Postoperative Management

• ASA classification, preoperative investigations, NBM guidelines (6-4-2 rule)
• Specific conditions: DM, steroids, anticoagulants, cardiovascular disease
• DVT prophylaxis (Caprini score, LMWH, TED stockings)
• Postoperative complications with timeline and the 5 W's fever mnemonic
• ERAS protocol, fluid management, analgesia ladder

Topic 5: Instrumentation

• Theatre zones, attire, sterilisation methods (with temperatures)
• Cutting, grasping, retractors, clamps - named instruments with uses
• Suture materials: absorbable (Vicryl, Monocryl, PDS) vs non-absorbable (Prolene, Nylon, Silk)
• Diathermy - monopolar vs bipolar, indications and dangers
• Laparoscopic instruments, drains (types and uses)