Principles of Surgery and Surgical Technique
Wound healing
Healing proceeds through haemostasis, inflammation (days 0–3, neutrophils then macrophages), proliferation (fibroblasts, angiogenesis, granulation tissue, type III collagen) and remodelling, in which type III collagen is replaced by type I and cross-linking raises tensile strength to about 80% of normal over months to a year. Healing is impaired by ischaemia, infection, diabetes, corticosteroids, smoking, radiotherapy, malnutrition, jaundice and uraemia.
Sutures and instruments
Absorbable sutures include catgut, polyglactin (60–90 days), poliglecaprone and polydioxanone (about 180 days); non-absorbable include silk, nylon and polypropylene. Monofilament sutures resist infection better than braided ones. Fine instruments, careful tissue handling and avoidance of dead space matter more than the choice of material.
Haemostasis
Primary haemostasis is the platelet plug, dependent on von Willebrand factor and glycoprotein IIb/IIIa. Secondary haemostasis is the coagulation cascade: the extrinsic pathway is measured by prothrombin time and INR, the intrinsic by APTT, and both converge on factor X, thrombin and fibrin. Fibrinolysis is driven by plasmin. Bipolar diathermy is safer near delicate structures; tourniquets demand accurate pressure and time recording.
Fluids and electrolytes
Maintenance is 4 mL/kg/h for the first 10 kg, 2 for the next 10 and 1 thereafter (4-2-1 rule). Crystalloid distributes largely extravascularly, so only about 25% of infused isotonic saline remains intravascular - replace blood loss with roughly three to four times the volume as crystalloid, or one-to-one with colloid or blood.
Rule of thumb: "if the gut works, use it" and "replace like for like" - blood for major haemorrhage, crystalloid for pure deficit.