Basic Principles of Surgery and Perioperative Care
Wound healing and the perioperative arc
Healing proceeds through haemostasis, inflammation, proliferation and remodelling. Questions test modifiers: ischaemia, diabetes, steroids, smoking, radiotherapy and infection impair healing; malnutrition and vitamin C deficiency impair collagen cross-linking. Distinguish primary, secondary and delayed primary closure, and recognise that abdominal wall dehiscence often presents with serosanguinous discharge around day 5–8.
Haemostasis relies on primary (platelet plug) and secondary (coagulation cascade) mechanisms. Know when to reverse anticoagulation, and the inherited disorders (haemophilia A/B, von Willebrand disease) versus acquired (liver disease, vitamin K deficiency, disseminated intravascular coagulation).
Fluids, electrolytes and nutrition
Isotonic losses (vomiting, diarrhoea, fistula, third space) cause hypovolaemia; replace with balanced crystalloid, not dextrose. Maintenance can be estimated by the 4-2-1 rule (4 mL/kg/h for the first 10 kg, 2 for the next 10 kg, 1 mL/kg/h thereafter). Hyponatraemia from excessive hypotonic fluid is a classic exam trap; so is hypokalaemia from vomiting despite total body potassium depletion. Enteral nutrition is preferred; start early and monitor for refeeding syndrome (hypophosphataemia).
Shock, infection and anaesthesia
Classify shock as hypovolaemic, cardiogenic, distributive (septic, neurogenic, anaphylactic) and obstructive. Septic shock is vasodilated with warm peripheries, not cold. Surgical site infection prevention: prophylaxis within 60 minutes of incision, redosing for long operations and blood loss, normothermia and glycaemic control. Anaesthetic traps include malignant hyperthermia triggers (volatile agents, suxamethonium) and the need for careful airway assessment.
Traps and rule of thumb
Postoperative fever timing is a favourite: day 1–2 atelectasis, day 3–5 urinary or line sepsis, day 5–8 wound or anastomotic leak. Do not chase fever with antibiotics before examining the wound. Rule of thumb: a patient who is oliguric, tachycardic and has a rising lactate after surgery has hypovolaemia or sepsis until proven otherwise - reassess, culture and resuscitate before imaging.