MRCS Part A Principles of Surgery-in-General Syllabus

What does end-tidal $\mathrm{CO_2}$ (capnography) confirm intraoperatively, and its normal value?

It confirms correct tracheal tube placement, ongoing ventilation and pulmonary perfusion. Normal $\mathrm{EtCO_2} \approx 4.6\text{–}6.0\ kPa$ ($35\text{–}45\ mmHg$).

Define diathermy and the difference between monopolar and bipolar.

Diathermy uses high-frequency alternating current ($\sim 400\ kHz\text{–}10\ MHz$) to cut/coagulate tissue. Monopolar: current passes from active electrode through the patient to a return plate. Bipolar: current passes only between the two limbs of forceps — safer near end-arteries and with pacemakers.

What are the main risks of monopolar diathermy and how are they mitigated?

Burns (from poor plate contact, channelling in narrow pedicles, or alternative earthing), fire with alcohol preps, and pacemaker interference. Mitigate with correct plate placement, avoiding end-arteries, bipolar near appendages, and dry skin prep.

State Poiseuille's law and its surgical relevance to IV access/fluid resuscitation.

$$Q = \frac{\pi \Delta P\, r^{4}}{8 \eta L}$$ Flow is proportional to $r^{4}$ and inversely to length — so a short wide cannula gives far faster flow than a long narrow one.

What are Halsted's principles of surgical technique?

Gentle tissue handling, meticulous haemostasis, preservation of blood supply, strict aseptic technique, minimal tension on tissues, accurate tissue apposition, and obliteration of dead space.

Describe the four phases of wound healing and their approximate timing.

Haemostasis (immediate), Inflammation (days $0$–$3$), Proliferation/granulation (days $3$–$21$), and Remodelling/maturation (weeks to $\sim 1$ year). Wound gains only $\approx 80\%$ of original tensile strength.

Distinguish healing by primary, secondary, and tertiary intention.

Primary: clean wound edges apposed directly (e.g. sutured incision). Secondary: wound left open to granulate from the base (e.g. abscess cavity). Tertiary (delayed primary): wound left open then closed after a few days once contamination controlled.

Classify surgical sutures by absorbability with one example each.

Absorbable: Vicryl (polyglactin), Monocryl (poliglecaprone), PDS (polydioxanone), catgut. Non-absorbable: silk, nylon (Ethilon), polypropylene (Prolene), stainless steel.

What does a suture's USP gauge indicate (e.g. 3-0 vs 5-0)?

It denotes thread diameter: the more zeros, the thinner the suture. So $5\text{-}0$ is thinner than $3\text{-}0$. Thinner sutures are used for finer, less load-bearing tissue (e.g. face, vessels).

Define minimally invasive (laparoscopic) surgery and list three physiological effects of the pneumoperitoneum.

Surgery through small ports using a camera and long instruments. $\mathrm{CO_2}$ pneumoperitoneum causes: raised intra-abdominal pressure (reduced venous return, splinted diaphragm), hypercarbia/absorption acidosis, and reduced renal/splanchnic perfusion.

List advantages of minimally invasive surgery over open surgery.

Less postoperative pain, smaller scars, reduced wound infection/hernia, shorter hospital stay, faster return to normal activity, and less blood loss — at the cost of longer operating time, cost and a learning curve.

Why is $\mathrm{CO_2}$ chosen as the insufflation gas for laparoscopy?

It is non-combustible (safe with diathermy), highly soluble/rapidly absorbed and excreted (low risk of gas embolism), colourless, and inexpensive.

Name three advanced/robotic surgical technologies and one benefit of robotic surgery.

Robotic platforms (e.g. da Vinci), image-guided/navigation surgery, and intraoperative fluorescence (indocyanine green). Robotic benefit: wristed instruments with $7$ degrees of freedom, tremor filtration and 3D magnified vision improving precision in confined spaces.

Define the systemic inflammatory response syndrome (SIRS) criteria.

Two or more of: temperature $>38\,^{\circ}\mathrm{C}$ or $<36\,^{\circ}\mathrm{C}$; heart rate $>90/min$; respiratory rate $>20/min$ or $\mathrm{PaCO_2}<4.3\ kPa$; WCC $>12$ or $<4 \times 10^{9}/L$.

What is the current (Sepsis-3) definition of sepsis and septic shock?

Sepsis: life-threatening organ dysfunction (rise in SOFA score $\geq 2$) caused by a dysregulated host response to infection. Septic shock: sepsis with persistent hypotension needing vasopressors to keep MAP $\geq 65\ mmHg$ and lactate $>2\ mmol/L$ despite fluids.

List the components of the 'Sepsis Six' bundle to be delivered within 1 hour.

Give: oxygen, IV fluids, IV antibiotics. Take: blood cultures, lactate, and monitor urine output. (3 in, 3 out.)

Give the formula for Mean Arterial Pressure (MAP) and its critical organ-perfusion threshold.

$$MAP = DBP + \frac{1}{3}(SBP - DBP)$$ A MAP of at least $65\ mmHg$ is generally required to maintain vital organ perfusion.

Classify haemorrhagic shock by the ATLS four classes (blood loss and signs).

Class I: $<15\%$ (up to $750\ mL$), normal signs. Class II: $15\text{–}30\%$, tachycardia, narrowed pulse pressure. Class III: $30\text{–}40\%$, hypotension, confusion. Class IV: $>40\%$, marked hypotension, negligible urine output — immediately life-threatening.

Describe the classification of postoperative pyrexia by timing ('the 5 Ws').

Wind (atelectasis/pneumonia, days $1$–$2$), Water (UTI, days $3$–$5$), Wound (infection, days $5$–$7$), Walking (DVT/PE, days $5$+), and Wonder drugs / lines (drug reaction, IV-line sepsis).

What are the components of Virchow's triad predisposing to venous thromboembolism?

Stasis (immobility), endothelial injury (surgery/trauma), and hypercoagulability (malignancy, pregnancy, thrombophilia).

List methods of VTE prophylaxis in surgical patients (mechanical and pharmacological).

Mechanical: early mobilisation, graduated compression stockings, intermittent pneumatic compression. Pharmacological: low-molecular-weight heparin, unfractionated heparin, or DOACs — balanced against bleeding risk.

Define wound dehiscence and give its typical presentation.

Partial or complete separation of the layers of a surgical wound. Classically presents around day $5$–$8$ with a serosanguinous ('pink') discharge; 'burst abdomen' with bowel evisceration is a surgical emergency.

Distinguish an anastomotic leak's typical onset and key clinical signs.

Usually presents around days $5$–$7$ with fever, tachycardia, prolonged ileus, abdominal pain/peritonism, raised inflammatory markers, and sometimes faeculent drain output. Requires urgent imaging (CT with contrast) and intervention.

What is the Clavien-Dindo classification used for, and outline its grades?

It grades the severity of surgical complications by the treatment required. Grade I: any deviation, no treatment; II: pharmacological treatment/transfusion; III: surgical/endoscopic/radiological intervention (IIIa no GA, IIIb with GA); IV: life-threatening/organ failure (ICU); V: death.

Outline the metabolic (Cuthbertson/Moore) phases of the stress response to surgery.

Ebb phase (first $\sim 24$ h): hypometabolism, hypovolaemia, catecholamine surge. Flow phase: catabolism, hypermetabolism, negative nitrogen balance, insulin resistance. Anabolic recovery phase: restoration of protein/fat stores.

Define daily maintenance fluid and electrolyte requirements for an adult (NICE).

Water $\approx 25\text{–}30\ mL/kg/day$; sodium, potassium and chloride $\approx 1\ mmol/kg/day$ each; glucose $\approx 50\text{–}100\ g/day$ to limit ketosis.

State the daily energy and protein requirements to consider in surgical nutritional support.

Approximately $25\text{–}30\ kcal/kg/day$ energy and $\approx 1.0\text{–}1.5\ g/kg/day$ protein (nitrogen $\approx 0.15\text{–}0.25\ g/kg/day$), guided by catabolic state.

What is refeeding syndrome and its biochemical hallmarks?

A dangerous fluid/electrolyte shift on reintroducing nutrition to a starved patient, driven by insulin surge. Hallmarks: hypophosphataemia (key), hypokalaemia, hypomagnesaemia, and thiamine deficiency — risking arrhythmia and cardiac failure.

Define the four principles (pillars) of medical ethics relevant to surgical decision-making.

Autonomy (respect patient self-determination), Beneficence (act in the patient's best interest), Non-maleficence ('first do no harm'), and Justice (fair distribution of resources and equal treatment).

What is a DNACPR decision and does it require patient consent?

A Do Not Attempt CPR decision recording that cardiopulmonary resuscitation will not be attempted. It is a clinical decision, but there is a legal duty to consult and inform the patient (or, if they lack capacity, those close to them) — established by Tracey (2014).

Define the doctrine of double effect in end-of-life surgical/palliative care.

Providing treatment (e.g. opioids/sedation) with the primary intention of relieving suffering is ethically and legally permissible even if a foreseen but unintended secondary effect is to hasten death — provided the intent is symptom relief, not to kill.

What is the QALY and how is it used in resource allocation (e.g. NICE)?

The Quality-Adjusted Life Year combines length and quality of life ($1$ QALY = one year in perfect health). Cost-effectiveness is judged by cost per QALY; NICE typically uses a threshold around $£20{,}000\text{–}£30{,}000$ per QALY to allocate finite resources justly.