11.1 Preoperative Risk Assessment, Wound Healing & Surgical Infections

Preoperative Risk Assessment

The cornerstone of surgical success lies not only in operative technique but in meticulous preoperative preparation. The primary goal of preoperative evaluation is to identify and mitigate risks, ensuring the patient is in optimal condition to withstand the physiological stress of surgery and anesthesia. A detailed history and physical examination remain the most critical components.

ASA Physical Status Classification System The American Society of Anesthesiologists (ASA) classification is universally utilized to assess a patient's pre-anesthesia medical co-morbidities.

• ASA I: A normal healthy patient.
• ASA II: A patient with mild systemic disease (e.g., controlled hypertension, well-controlled diabetes without systemic effects, mild obesity, social drinker, smoker).
• ASA III: A patient with severe systemic disease (e.g., poorly controlled hypertension or diabetes, morbid obesity, chronic renal failure, prior myocardial infarction).
• ASA IV: A patient with severe systemic disease that is a constant threat to life (e.g., recent MI or stroke, severe valve dysfunction, sepsis).
• ASA V: A moribund patient who is not expected to survive without the operation (e.g., ruptured abdominal aortic aneurysm, massive trauma).
• ASA VI: A declared brain-dead patient whose organs are being removed for donor purposes. The addition of "E" denotes an emergency surgery.

Cardiac and Pulmonary Risk Assessment Cardiac complications are a leading cause of perioperative morbidity. The Revised Cardiac Risk Index (RCRI) assesses six independent predictors: high-risk surgery (intraperitoneal, intrathoracic, or suprainguinal vascular), history of ischemic heart disease, history of congestive heart failure, history of cerebrovascular disease, preoperative treatment with insulin, and preoperative serum creatinine > 2.0 mg/dL. Patients with multiple risk factors or poor functional capacity (<4 METs) may require further evaluation such as echocardiography or stress testing prior to elective procedures.

Pulmonary risk is equally critical, particularly for upper abdominal or thoracic surgeries. The ARISCAT score predicts the risk of postoperative pulmonary complications (PPCs). Risk factors include advanced age, low preoperative oxygen saturation, recent respiratory infection, anemia, and prolonged duration of surgery. Optimization strategies involve smoking cessation (ideally 4-8 weeks preoperatively), chest physiotherapy, and optimizing treatments for asthma or COPD.

Venous Thromboembolism (VTE) Prophylaxis Surgical patients are inherently at high risk for VTE due to Virchow's triad: venous stasis, endothelial injury, and hypercoagulability. The Caprini Risk Assessment Model is widely used to stratify general surgery patients. Depending on the score, prophylaxis ranges from early ambulation (very low risk) to mechanical methods like intermittent pneumatic compression devices (low risk), and pharmacological prophylaxis using low molecular weight heparin (LMWH) or unfractionated heparin (moderate to high risk). High-risk patients, especially those undergoing cancer surgery, may require extended prophylaxis post-discharge.

Wound Healing

Wound healing is a complex, dynamic process traditionally divided into three overlapping phases:

1. Inflammatory Phase (Days 0-4): Characterized by hemostasis (platelet aggregation, fibrin clot formation) and inflammation. Neutrophils are the first cells to arrive, clearing debris and bacteria, followed by macrophages, which release cytokines and growth factors to coordinate the subsequent phases.
2. Proliferative Phase (Days 4-21): Fibroblasts synthesize collagen, promoting tissue strength. Angiogenesis occurs to supply nutrients, and epithelialization resurfaces the wound. Granulation tissue, which is highly vascular and beefy red, fills the defect.
3. Remodeling Phase (Weeks to Years): Type III collagen is gradually replaced by stronger Type I collagen. The wound gains tensile strength, ultimately reaching about 80% of the strength of uninjured skin.

Types of Wound Closure

• Primary Intention: The wound edges are closely approximated (e.g., sutured surgical incision). Healing is rapid with minimal scarring.
• Secondary Intention: The wound is left open to heal by granulation, contraction, and epithelialization. This is used for contaminated or infected wounds where closure would trap bacteria.
• Tertiary Intention (Delayed Primary Closure): The wound is initially left open to resolve heavy contamination or infection, then surgically closed a few days later.

Surgical Site Infections (SSIs)

SSIs account for a significant proportion of healthcare-associated infections. They are classified into three categories: superficial incisional (involving skin and subcutaneous tissue), deep incisional (involving deep soft tissues like fascia and muscle), and organ/space (involving any part of the anatomy other than the incision, manipulated during the procedure).

Prevention and Management The most critical step in preventing SSIs is the timely administration of prophylactic antibiotics. Antibiotics should be administered within 60 minutes prior to surgical incision to ensure adequate tissue concentrations. Cefazolin is a common choice for clean and clean-contaminated procedures. If MRSA is suspected or the patient is allergic to beta-lactams, vancomycin or clindamycin may be used. For procedures involving the lower gastrointestinal tract, coverage must include anaerobic organisms (e.g., addition of metronidazole). Other preventive measures include appropriate hair removal (clipping, not shaving), normothermia, glycemic control, and meticulous surgical technique.