Surgical Principles and Perioperative Care
This section covers asepsis, wound healing, haemostasis, fluid and electrolyte management, nutrition, transfusion and anaesthesia basics. Questions typically ask for the next step, the error in a management plan, or the safest perioperative choice in a comorbid patient.
Asepsis and theatre discipline
- The WHO Surgical Safety Checklist has three phases: sign in (before induction), time out (before incision) and sign out (before leaving theatre).
- Skin preparation with chlorhexidine-alcohol reduces surgical site infection more than povidone-iodine (Darouiche, NEJM 2010); avoid alcohol near mucous membranes and the eye.
- Hair is removed with clippers, not a razor; shaving causes micro-abrasions and increases infection.
- Double gloving reduces perforation and blood contact; change gloves after any breach.
Wound healing and wound care
- Healing by primary, secondary or tertiary intention. Dehiscence typically occurs days 5–10; burst abdomen needs urgent closure.
- Impaired healing: hypoxia, diabetes, steroids, radiotherapy, malnutrition, uraemia, jaundice, infection.
- Sutures: monofilament resists infection better than braided; absorbable versus non-absorbable chosen by tissue and tension.
- Negative-pressure wound therapy improves granulation in open wounds but must not be used on ischaemic or malignant tissue.
Haemostasis and transfusion
- Platelet plug then coagulation cascade; tranexamic acid 1 g is given within 3 hours in trauma and many elective settings.
- Restrictive transfusion: haemoglobin threshold 7 g/dL (8 g/dL in cardiac disease). Transfuse single units and reassess.
- Reactions: acute haemolytic (ABO error, fever, loin pain, DIC), TRALI (within 6 hours, bilateral infiltrates), TACO (volume overload), delayed haemolytic.
- Fresh frozen plasma for active bleeding with INR above 1.5; platelets for count below 50 × 10⁹/L with bleeding.
Fluids, electrolytes and nutrition
- Maintenance 4-2-1 rule (4 mL/kg/h first 10 kg, 2 for next 10, 1 thereafter); roughly 25–30 mL/kg/day.
- Excessive 0.9% saline causes hyperchloraemic metabolic acidosis; balanced crystalloid is preferred in large volumes.
- Enhanced recovery: carbohydrate loading, avoidance of drains and nasogastric tubes, early feeding and mobilisation.
- ESPEN surgical nutrition: 25–30 kcal/kg/day and 1.2–1.5 g/kg/day protein; enteral route preferred.
Anaesthesia basics
- Spinal anaesthesia causes hypotension from sympathectomy; preload and vasopressors as needed.
- Malignant hyperthermia: hypercapnia, rigidity, rising temperature - dantrolene 2.5 mg/kg and stop the trigger.
- Suxamethonium is avoided in hyperkalaemia, burns beyond 24 hours and spinal cord injury because of potassium efflux.
Worked example
A 70 kg man is nil by mouth on day 1 after laparotomy with no oral intake. Maintenance by the 4-2-1 rule is (4×10) + (2×10) + (1×50) = 110 mL/h, about 2.6 L/day, plus replacement of nasogastric losses and any deficit. Potassium is added once urine output is adequate. Over-resuscitation with saline would produce oedema and hyperchloraemic acidosis.
Traps that lose marks
Adding potassium before confirming urine output; using 5% dextrose as resuscitation fluid; forgetting steroid cover in a patient on long-term corticosteroids; transfusing to a normal haemoglobin rather than a threshold.