35.3 Basic Surgical Principles III: Preoperative Assessment, Wound Healing, Surgical Infection and Asepsis, Postoperative Fever, Surgical Oncology, Immunology and Transplantation, Anesthesia and Patient Safety

Why this area matters

The TOS lists:

• wound healing;
• surgical infection;
• asepsis and antisepsis;
• oncology, immunology and transplantation;
• anesthesia;
• patient safety and quality of surgical care.

It also asks you to prepare patients for surgery and plan postoperative care. Surgical site infections, wrong-site surgery and preventable anesthetic complications are avoidable harms, and quality programs target them.

Preoperative Risk Stratification & Cardiac Evaluation

Preoperative assessment seeks to uncover uncompensated systemic disorders, quantify perioperative morbidity, and optimize physiological reserve prior to elective intervention.

Cardiovascular Risk Stratification: The Revised Cardiac Risk Index (RCRI)

Cardiovascular events constitute the leading cause of perioperative mortality following non-cardiac surgery. The Revised Cardiac Risk Index (RCRI), or Lee Criteria, evaluates six independent clinical predictors of Major Adverse Cardiac Events (MACE):

1. High-risk surgical procedure: Intraperitoneal, intrathoracic, or suprainguinal vascular surgery.
2. History of ischemic heart disease: Prior myocardial infarction, positive exercise stress test, current angina, nitrate use, or pathological Q waves.
3. History of congestive heart failure: Prior pulmonary edema, paroxysmal nocturnal dyspnea, bilateral crackles, S3 gallop, or cardiomegaly on chest radiograph.
4. History of cerebrovascular disease: Prior transient ischemic attack (TIA) or cerebrovascular accident (CVA).
5. Preoperative diabetes mellitus requiring insulin therapy.
6. Preoperative serum creatinine $> 2.0\text{ mg/dL}$ ($> 177\text{ }\mu\text{mol/L}$).

Functional Capacity: Metabolic Equivalents (METs)

Functional capacity is quantified in Metabolic Equivalents of Task (METs), where $1\text{ MET} = 3.5\text{ mL } \text{O}_2\text{/kg/min}$ (resting basal oxygen consumption):

• Poor functional capacity ($< 4\text{ METs}$): Inability to walk two blocks on level ground or climb one flight of stairs without stopping due to dyspnea or angina. Patients in this category with elevated RCRI scores require preoperative pharmacological stress testing (dobutamine echocardiography or dipyridamole/adenosine myocardial perfusion imaging).
• Moderate to excellent capacity ($\ge 4\text{ to } > 10\text{ METs}$): Ability to climb two flights of stairs, run a short distance, or engage in vigorous sports. Patients demonstrating $\ge 4\text{ METs}$ can safely undergo non-cardiac surgery without further non-invasive testing even in the presence of elevated RCRI factors.

Perioperative Pulmonary and Hepatic Risk

• Pulmonary Risk: Chronic obstructive pulmonary disease (COPD), cigarette smoking (stopping at least 4 to 8 weeks before surgery gives the greatest reduction in respiratory and wound complications, but stopping at any time before surgery helps), advanced age, and upper abdominal or thoracic incisions. Incentive spirometry and early post-op ambulation mitigate atelectasis.
• Hepatic Risk: Evaluated using the Child-Turcotte-Pugh (CTP) score (Albumin, Bilirubin, INR/PT, Ascites, Encephalopathy) and MELD score. Class A cirrhosis carries ~10% surgical mortality, Class B carries ~30% mortality, and Class C carries $> 75-80\%$ operative mortality, representing a relative contraindication to non-emergent elective surgery.

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Perioperative Medication Management: Antiplatelet and Anticoagulant Protocols

Balancing the risk of catastrophic intraoperative surgical hemorrhage against devastating thromboembolism (stent thrombosis, stroke, pulmonary embolism) dictates strict adherence to drug withdrawal intervals:

Biology of Surgical Wound Healing

Wound healing is a coordinated cellular and biochemical cascade divided into four continuous, overlapping phases:

1. Hemostasis (Minutes to Hours): Tissue injury exposes subendothelial collagen, initiating the intrinsic coagulation cascade and platelet aggregation. The provisional fibrin-fibronectin clot seals the wound. Degranulating platelets release Platelet-Derived Growth Factor (PDGF) and Transforming Growth Factor-beta (TGF-$\beta$), which act as potent chemoattractants for inflammatory cells.
2. Inflammation (Day 1 to Day 4):
   • Neutrophils (First 24-48 hours): First circulating cells to infiltrate; clear bacterial contaminants and devitalized debris via phagocytosis, reactive oxygen species, and proteases.
   • Macrophages (Day 2 to Day 4): The essential orchestrators of wound healing. Macrophages release critical cytokines (TGF-$\beta$, VEGF, FGF, PDGF) that stimulate angiogenesis, re-epithelialization, and fibroblastic recruitment. Absence of macrophages arrests repair.
3. Proliferation (Day 4 to Day 21): Characterized by four interdependent events:
   • Fibroplasia: Fibroblasts proliferate and synthesize ground substance (glycosaminoglycans, proteoglycans) and Type III collagen (immature, thin, non-crosslinked).
   • Angiogenesis: Vascular Endothelial Growth Factor (VEGF) promotes budding of new capillary loops, producing beefy-red granulation tissue.
   • Epithelialization: Keratinocytes migrate across the viable wound bed from wound edges and adnexal structures (hair follicles, sweat glands) until contact inhibition occurs.
   • Wound Contraction: Specialized myofibroblasts containing alpha-smooth muscle actin anchor to extracellular fibronectin and contract the wound margins.
4. Remodeling / Maturation (Day 21 to 1-2 Years): Type III collagen is systematically degraded by matrix metalloproteinases (MMPs) and replaced by Type I collagen (thick, organized parallel fibrils). Tensile strength rises progressively: 3% at 1 week, 20% at 3 weeks, and plateaus at a maximum of 80% of original unbroken skin strength by 6 to 12 weeks. Wounds never regain 100% tensile strength.

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Surgical Wound Classification and Infection Prevention

Surgical Site Infections (SSIs) are classified according to the Centers for Disease Control and Prevention (CDC) operative field contamination scheme:

Evidence-Based SSI Prevention Protocols

• Antimicrobial Prophylaxis Timing: First-line parenteral antibiotic (typically Cefazolin $2\text{ g}$ IV, or $3\text{ g}$ if weight $> 120\text{ kg}$) must be fully infused within 60 minutes prior to surgical incision (within 120 minutes for vancomycin or fluoroquinolones) to establish tissue levels exceeding minimum inhibitory concentration (MIC). Prophylaxis must be redosed if surgery exceeds two drug half-lives ($3-4\text{ hours}$ for cefazolin) or blood loss exceeds $1,500\text{ mL}$. Prophylactic antibiotics must be discontinued within 24 hours postoperatively.
• Hair Removal: Never use razors, which create microscopic dermal abrasions serving as bacterial nidi. If hair interferes with the field, use electric clippers immediately prior to surgery.
• Skin Antisepsis: Chlorhexidine-gluconate with alcohol is superior to povidone-iodine.
• Physiologic Maintenance: Maintain intraoperative normothermia ($> 36.0^\circ\text{C}$), perioperative euglycemia (blood glucose $< 180\text{ mg/dL}$), and adequate tissue oxygenation.

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Diagnostic Approach to Postoperative Fever: The "5 Ws"

Postoperative pyrexia (temperature $\ge 38.0^\circ\text{C}$ or $100.4^\circ\text{F}$) follows a predictable chronologic differential diagnosis governed by the mnemonic "5 Ws":

1. Wind (Postoperative Days 1-2): Atelectasis & Early Pulmonary Complications
   • Mechanism: General anesthesia, immobility, diaphragmatic splinting from pain, and decreased tidal volumes cause alveolar collapse in lung bases.
   • Workup & Management: Chest auscultation reveals decreased breath sounds and bibasilar crackles. Treatment: Incentive spirometry, deep breathing exercises, aggressive pulmonary toilet, adequate multimodal analgesia, and early mobilization. Routine chest radiographs and antibiotics are not indicated for early uncomplicated atelectasis.
2. Water (Postoperative Day 3): Urinary Tract Infection (UTI)
   • Mechanism: Associated with indwelling transurethral Foley catheters (Catheter-Associated UTI, CAUTI); bacterial ascent (Escherichia coli, Klebsiella, Enterococcus).
   • Workup & Management: Urinalysis, urine culture and sensitivity. Prompt removal of indwelling catheter; initiate targeted antimicrobial therapy.
3. Wound (Postoperative Day 5): Surgical Site Infection (SSI)
   • Mechanism: Bacterial proliferation at incision site (Staphylococcus aureus, coagulase-negative staphylococci, enteric gram-negative bacilli). Note: Streptococcus pyogenes (Group A Strep) or Clostridium perfringens can cause fulminant, toxic wound infections within 24-48 hours.
   • Workup & Management: Examine wound bed; look for erythema, induration, warmth, fluctuating fluid collection, and purulent discharge. Management: Suture or staple removal, opening and drainage of the surgical incision, packing with moist gauze, allowing healing by secondary intention. Parenteral antibiotics are reserved for surrounding invasive cellulitis or systemic sepsis.
4. Walking (Postoperative Day 7): Deep Vein Thrombosis (DVT) & Pulmonary Embolism (PE)
   • Mechanism: Virchow's triad (stasis from bed rest, endothelial vessel injury, perioperative hypercoagulability).
   • Workup & Management: Unilateral lower extremity swelling, calf tenderness (Homan's sign is unreliable), tachycardia, pleuritic chest pain, acute tachypnea, desaturation. Duplex venous ultrasonography for DVT; CT Pulmonary Angiography (CTPA) for suspected PE. Treatment: Therapeutic anticoagulation (LMWH, unfractionated heparin infusion, or DOACs).
5. Wonder Drugs & Deep Collections (Postoperative Day 10+):
   • Mechanism: Drug-induced fever (beta-lactams, sulfonamides, heparin-induced thrombocytopenia, phenytoin) or occult deep surgical complications (intra-abdominal abscess, anastomotic leak, infected seroma/hematoma).
   • Workup & Management: Contrast-enhanced abdominal/pelvic CT scan to rule out anastomotic dehiscence or fluid collections. Discontinue non-essential offending medications. Percutaneous image-guided catheter drainage of loculated abscesses.

Wound closure and abnormal healing

• Types of wound closure:
  • primary intention: edges closed at once in clean wounds;
  • secondary intention: left open to heal by granulation and contraction, as in contaminated wounds or abscess cavities;
  • tertiary intention (delayed primary closure): left open for 3 to 5 days, then closed if clean, as in contaminated trauma.
• Factors that impair healing:
  • infection;
  • ischemia;
  • diabetes;
  • malnutrition (protein, vitamin C, zinc);
  • corticosteroids (vitamin A partly reverses their effect);
  • smoking;
  • radiation;
  • chemotherapy;
  • old age;
  • tension.
• Abnormal scars:
  • hypertrophic scars stay within the wound borders and may regress;
  • keloids extend beyond the wound borders, are more common in darker skin and on the earlobes, chest and shoulders, and recur after simple excision. Treat keloids with intralesional steroids, pressure and silicone sheets, and excision plus adjuvant therapy.
• Chronic wounds (venous, arterial, diabetic and pressure ulcers): treat the cause, debride and offload. A non-healing ulcer in an old scar or chronic sinus may be a Marjolin ulcer (squamous cell carcinoma), so biopsy it.

Surgical infection, asepsis and antisepsis

• Sterilization destroys all microbes including spores:
  • steam autoclave, for example 121°C for at least 15 minutes, is the standard for heat-stable instruments;
  • dry heat;
  • ethylene oxide for heat-sensitive items;
  • hydrogen peroxide plasma;
  • glutaraldehyde as a high-level disinfectant or chemical sterilant for endoscopes.
• Disinfection levels: high-level (endoscopes), intermediate and low-level (surfaces). Antisepsis applies to living tissue: chlorhexidine-alcohol, povidone-iodine and alcohol hand rub.
• Surgical hand antisepsis and sterile technique (gowns, gloves, drapes, OR traffic control) reduce infection.
• Surgical infections:
  • abscesses need drainage;
  • cellulitis needs antibiotics;
  • necrotizing soft-tissue infections need emergency debridement;
  • intra-abdominal infections need source control plus antibiotics;
  • hospital-acquired infections include SSI, pneumonia, catheter-associated UTI and central-line infection.
• Tetanus prophylaxis for wounds:
  • for a clean minor wound, give Td or Tdap if the patient has had fewer than 3 doses or the last dose was more than 10 years ago;
  • for other wounds (contaminated, puncture, crush, burns), give Td or Tdap if the patient has had fewer than 3 doses or the last dose was more than 5 years ago, plus tetanus immune globulin if fewer than 3 doses or unknown history.

Surgical oncology, immunology and transplantation

• Diagnosis:
  • tissue diagnosis by fine-needle aspiration, core needle biopsy, incisional biopsy (part of a large mass) or excisional biopsy (the whole lesion);
  • sarcomas and limb masses are biopsied along the line of the future incision.
• Staging: TNM staging (tumor size and invasion, nodes, metastasis) guides treatment and prognosis. Grading describes differentiation.
• Principles of oncologic resection:
  • en bloc removal with clear (R0) margins;
  • removal of the regional nodes or sentinel lymph node biopsy (breast cancer, melanoma);
  • avoiding tumor spillage.
• Multimodal therapy:
  • neoadjuvant treatment (before surgery) to shrink tumors, as in rectal, breast and esophageal cancer;
  • adjuvant therapy (after surgery) to treat micrometastases;
  • palliative surgery for obstruction or bleeding.
• Tumor markers monitor recurrence: CEA, AFP, CA 19-9, CA-125, PSA, calcitonin, hCG.
• Transplant immunology:
  • HLA matching and crossmatch reduce rejection;
  • hyperacute rejection occurs within minutes from preformed antibodies (ABO or HLA) and is prevented by crossmatching;
  • acute rejection occurs in weeks to months, is mainly T-cell mediated and is reversible with steroids;
  • chronic rejection occurs over months to years with fibrosis and vasculopathy and is irreversible.
• Immunosuppressants:
  • calcineurin inhibitors (tacrolimus, cyclosporine): nephrotoxicity, hypertension, tremor;
  • mycophenolate: myelosuppression;
  • corticosteroids;
  • mTOR inhibitors;
  • induction antibodies.
  • Risks are opportunistic infections (CMV) and cancers (skin cancer, post-transplant lymphoproliferative disorder).
• Organ donation follows RA 7170: brain death determination and informed consent. Commercial organ trade is prohibited.

Anesthesia

• ASA physical status:
  • I: healthy;
  • II: mild systemic disease;
  • III: severe systemic disease;
  • IV: severe systemic disease that is a constant threat to life;
  • V: moribund;
  • VI: brain-dead organ donor;
  • "E" is added for emergencies.
• Fasting before elective surgery: clear fluids up to 2 hours, breast milk 4 hours, a light meal or formula 6 hours, a heavy meal 8 hours.
• Airway assessment: Mallampati class, mouth opening, neck mobility. Prepare for a difficult airway.
• Drugs for general anesthesia:
  • propofol: hypotension, antiemetic;
  • ketamine: maintains BP and airway reflexes, bronchodilator, causes emergence reactions; useful in shock and asthma;
  • etomidate: cardiovascularly stable, causes adrenal suppression;
  • volatile agents (sevoflurane, isoflurane);
  • opioids;
  • neuromuscular blockers: succinylcholine (depolarizing, fast onset) causes hyperkalemia in burns, crush injury, denervation and immobilization after the first days, and is a trigger for malignant hyperthermia. Non-depolarizing blockers (rocuronium) are reversed with neostigmine or sugammadex.
• Malignant hyperthermia:
  • an inherited ryanodine receptor (RYR1) disorder triggered by volatile anesthetics and succinylcholine;
  • rising end-tidal CO2, masseter rigidity, tachycardia, hyperthermia, hyperkalemia, acidosis and rhabdomyolysis;
  • treat by stopping the trigger, giving dantrolene, cooling and correcting hyperkalemia.
• Regional anesthesia:
  • spinal anesthesia (subarachnoid) is fast and dense, and causes hypotension and post-dural puncture headache;
  • epidural anesthesia can be continued for postoperative analgesia;
  • check coagulation first, because of the risk of epidural hematoma.
• Local anesthetics:
  • maximum lidocaine dose is about 4.5 mg/kg plain or 7 mg/kg with epinephrine; bupivacaine about 2.5 mg/kg (cardiotoxic);
  • local anesthetic systemic toxicity causes perioral numbness, tinnitus, seizures, arrhythmias and cardiac arrest. Treat with airway support, seizure control and 20% lipid emulsion;
  • epinephrine-containing solutions are used with caution in end-arteries.

Patient safety and quality of surgical care

• WHO Surgical Safety Checklist:
  • sign in, before induction: identity, site, consent, site marking, anesthesia check, allergies, airway and aspiration risk, risk of blood loss;
  • time out, before incision: team introductions, confirm patient, site and procedure, antibiotic prophylaxis given, anticipated critical events, imaging displayed;
  • sign out, before the patient leaves the room: procedure recorded, instrument, sponge and needle counts correct, specimen labeling, equipment problems, recovery concerns.
  • The checklist lowers complications and deaths.
• Never events: wrong-site, wrong-procedure and wrong-patient surgery, and retained foreign objects. Prevent them with site marking, time-outs and counts.
• Quality measures:
  • surgical site infection rates;
  • morbidity and mortality conferences;
  • clinical audit and outcome tracking;
  • VTE prophylaxis;
  • informed consent;
  • teamwork and communication (structured handoffs such as SBAR);
  • ERAS pathways;
  • a culture of reporting errors without blame.