ACEM Primary cheat sheet

Primary survey sequence: catastrophic haemorrhage control, Airway with cervical spine protection, Breathing, Circulation, Disability (GCS/pupils), Exposure with prevention of hypothermia.

GCS = eye (1-4) + verbal (1-5) + motor (1-6); range 3-15; intubate for GCS <=8.

Anaphylaxis: IM adrenaline 0.5 mg (0.5 mL of 1:1000) into anterolateral thigh in adults; repeat every 5 minutes as needed; adjuncts never precede adrenaline.

Adult cardiac arrest: compression rate 100-120/min, depth 5-6 cm, ratio 30:2, minimise interruptions to <10 s, defibrillate VF/pVT immediately.

Shock index = heart rate / systolic blood pressure; >0.9 suggests occult haemorrhage in trauma.

Burns: Parkland formula 4 mL/kg/%TBSA crystalloid in first 24 h, half in first 8 h from injury time; do not include superficial epidermal burns in TBSA.

Sepsis: qSOFA (respiratory rate >=22, systolic BP <=100, altered mentation) predicts poor outcome; lactate >=2 mmol/L with infection flags high risk.

Tension pneumothorax is a clinical diagnosis: immediate needle decompression then tube thoracostomy; never wait for imaging.

Brachial plexus roots C5-T1: '3,4,5 keeps the diaphragm alive' (phrenic C3-C5); Erb palsy = C5-C6, Klumpke = C8-T1.

Femoral triangle borders: inguinal ligament superiorly, sartorius laterally, adductor longus medially; contents NAVEL (nerve, artery, vein, empty space, lymphatics) lateral to medial.

Median nerve supplies thenar muscles (LOAF: lateral two lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis) and is compressed in carpal tunnel.

Common fibular (peroneal) nerve winds around the fibular neck; injury causes foot drop and loss of dorsiflexion and eversion.

Coronary arteries: right coronary supplies SA node in ~60% and AV node in ~85%; left anterior descending supplies anterior two-thirds of interventricular septum.

Recurrent laryngeal nerve: left loops under aortic arch, right under right subclavian artery; both run in tracheo-oesophageal groove, at risk in thyroid surgery.

Inguinal canal: deep ring lateral to inferior epigastric vessels (indirect hernia); superficial ring above and medial to pubic tubercle.

Necrosis types: coagulative (ischaemia, except brain), liquefactive (brain, abscess), caseous (TB), fat (pancreatitis), fibrinoid (vasculitis).

Apoptosis is energy-dependent, caspase-mediated, non-inflammatory; necrosis is passive and provokes inflammation.

Tumour suppressor paradigm: both alleles lost (Knudson two-hit) for retinoblastoma (RB) and for p53 in Li-Fraumeni syndrome.

Virchow's triad: endothelial injury, abnormal blood flow (stasis/turbulence), hypercoagulability.

Granuloma = collection of activated macrophages (epithelioid cells) with multinucleated giant cells, typical of TB, sarcoidosis, foreign body.

Metaplasia is reversible change of one mature cell type to another (e.g., squamous metaplasia of bronchial epithelium); dysplasia is disordered growth with atypia, not necessarily reversible.

Left ventricular hypertrophy from pressure overload shows thick fibres with boxcar nuclei; right heart failure causes nutmeg liver and cardiac cirrhosis.

Cardiac output = heart rate x stroke volume; Fick principle: CO = oxygen consumption / arteriovenous oxygen content difference.

Frank-Starling: stroke volume rises with increased end-diastolic volume up to an optimum, then falls with overstretch.

Mean arterial pressure ~ diastolic pressure + one-third of pulse pressure; cerebral autoregulation holds flow between MAP ~60 and 160 mmHg.

Oxygen delivery = cardiac output x arterial oxygen content; content = 1.34 x Hb x SaO2 + 0.003 x PaO2.

Renal: GFR = Kf x net filtration pressure; filtration ceases when Bowman's capsule pressure equals glomerular capillary pressure; clearance C = (U x V)/P.

Alveolar gas equation: PAO2 = FiO2 x (Patm - 47) - PaCO2/0.8; hypoxaemia causes are hypoventilation, diffusion, shunt, V/Q mismatch, low inspired O2.

Action potential phases: rapid upstroke from Na+ influx, plateau from Ca2+ influx, repolarisation from K+ efflux; refractory period prevents tetany in cardiac muscle.

Starling forces: net filtration = (capillary pressure + interstitial oncotic) - (plasma oncotic + interstitial pressure).

First-order (exponential) kinetics: constant fraction eliminated per unit time, half-life constant; zero-order (saturation) kinetics: constant amount per time, e.g., ethanol, phenytoin at high dose.

Clearance = dose rate / steady-state concentration; half-life = 0.693 x volume of distribution / clearance; steady state reached in ~4-5 half-lives.

Loading dose = target concentration x volume of distribution / bioavailability; maintenance rate = clearance x target concentration / bioavailability.

Competitive antagonists shift agonist dose-response curve right with no change in maximum; non-competitive antagonists lower maximum.

Heparin potentiates antithrombin III (aPTT monitoring); warfarin inhibits vitamin K epoxide reductase (INR monitoring); protamine and vitamin K reverse them respectively.

Organophosphate poisoning: irreversible acetylcholinesterase inhibition -> DUMBELS; treat with atropine (muscarinic) and pralidoxime (reactivates enzyme).

Paracetamol overdose: N-acetylcysteine replenishes glutathione; toxic metabolite NAPQI accumulates once sulfation/glucuronidation saturated.

Beta-blocker overdose: glucagon is antidote (bypasses beta receptor via cAMP); insulin-dextrose for calcium channel blocker toxicity.

ATLS classification of haemorrhagic shock classes I-IV based on estimated blood loss, heart rate, blood pressure, urine output and mental status.

Major trauma: permissive hypotension until haemorrhage control; avoid large-volume crystalloid which worsens dilutional coagulopathy.

Acute coronary syndrome: serial high-sensitivity troponin at 0 and 1-3 h; ST elevation mandates reperfusion within 120 min of first medical contact.

Acute asthma severity: inability to complete sentences, silent chest, bradycardia, exhaustion, SpO2 <92% indicate life-threatening attack.

Croup: single dose dexamethasone; nebulised adrenaline for moderate-severe stridor; intubation for impending airway failure.

Status epilepticus: benzodiazepine first-line at 5 min; second-line IV phenytoin or levetiracetam at 20 min; anaesthetic agents for refractory.

Opioid overdose: titrate naloxone to adequate respiration, not full consciousness; its half-life may be shorter than the opioid, requiring observation.

Cranial nerve exits: III midbrain, IV midbrain (dorsal), V pons, VI-VIII pontomedullary junction, IX-XI medulla, XII medulla.

Dermatomes: C5 lateral arm, C6 thumb, C7 middle finger, C8 little finger, T4 nipple, T10 umbilicus, L1 inguinal, L4 medial malleolus, L5 dorsum of foot, S1 lateral foot.

Axillary nerve (C5-C6) and circumflex humeral artery risk in surgical neck humeral fracture; radial nerve in midshaft humeral fracture.

Posterior tibial artery passes behind medial malleolus (palpable; dorsalis pedis over navicular); both supply foot.

Liver segments (Couinaud) numbered by portal vein branches; segment I is caudate; the hepatic veins divide right and left lobes into sectors.

Sympathetic chain: preganglionic fibres from T1-L2; parasympathetic from cranial nerves III, VII, IX, X and S2-S4.

Ureter has three constrictions (pelviureteric junction, pelvic brim, vesicoureteric junction) where stones lodge.

Inflammation: acute phase mediators include histamine (vasodilation), bradykinin (pain), leukotriene B4 (chemotaxis), TNF-alpha and IL-1 (endothelial activation).

Wound healing: primary intention (clean apposed edges), secondary intention (granulation, contraction), delayed (infection, poor perfusion).

Atherosclerosis: fatty streak -> fibrofatty plaque -> complicated plaque with rupture, thrombosis, and calcification; foam cells are lipid-laden macrophages.

Dystrophic calcification occurs in damaged tissue at normal serum calcium; metastatic calcification occurs with hypercalcaemia in normal tissue.

Tumour grade = differentiation and mitotic activity; stage = anatomical extent (TNM); stage is the stronger prognostic factor for most solid tumours.

Amyloid is a beta-pleated fibrillar protein (Congo red, apple-green birefringence under polarised light); AA from chronic inflammation, AL from plasma cells.

Cell injury: ATP depletion, mitochondrial damage, calcium influx, reactive oxygen species, membrane permeability are final common pathways.

Respiratory: minute ventilation = respiratory rate x tidal volume; alveolar ventilation = rate x (tidal volume - dead space).

Compliance = change in volume / change in pressure; surfactant from type II pneumocytes lowers surface tension and prevents alveolar collapse.

Oxyhaemoglobin dissociation shifted right (reduced affinity, more unloading) by raised CO2, H+, temperature, 2,3-DPG; left by fetal Hb and carboxyhaemoglobin.

Acid-base: Henderson-Hasselbalch pH = 6.1 + log([HCO3-]/0.03 x PaCO2); respiratory compensation changes PaCO2, metabolic changes HCO3-.

Anion gap = Na+ - (Cl- + HCO3-); normal 8-16 mmol/L; raised in ketoacidosis, lactate, urate, toxins (methanol, ethylene glycol, salicylate).

Aldosterone acts on distal tubule/collecting duct to reabsorb Na+ and secrete K+ and H+; ADH increases water permeability via aquaporin-2.

Glomerular filtration barrier: fenestrated endothelium, basement membrane, podocyte slit diaphragms; albumin loss indicates podocyte injury.

Cardiac conduction velocity fastest in Purkinje fibres, slowest at the AV node, producing the physiological delay.

Volume of distribution = amount of drug in body / plasma concentration; large for lipophilic drugs (e.g., digoxin, amiodarone), small for plasma-protein-bound or polar drugs.

Bioavailability is reduced by first-pass hepatic metabolism; intravenous bioavailability is 1 by definition.

Cytochrome P450 inducers (rifampicin, carbamazepine, phenytoin, St John's wort) lower levels of substrates; inhibitors (erythromycin, ketoconazole, grapefruit) raise them.

Aminoglycosides: concentration-dependent killing, nephrotoxic and ototoxic, monitored by trough levels; beta-lactams are time-dependent.

NSAIDs inhibit cyclo-oxygenase, reducing prostaglandin synthesis; risk of gastric ulceration and acute kidney injury with reduced renal perfusion.

Digoxin inhibits Na+/K+-ATPase; toxicity worsened by hypokalaemia and hypercalcaemia; treated with digoxin-specific antibody fragments.

Anticholinergic toxidrome: dry skin, mydriasis, urinary retention, tachycardia, delirium; cholinergic is the opposite with salivation, lacrimation, bronchorrhoea.

Selective serotonin reuptake inhibitors with monoamine oxidase inhibitors or tramadol risk serotonin syndrome: clonus, hyperthermia, agitation.

Head injury: anticoagulated patients with minor head injury need CT and observation; GCS drop >=2 points mandates urgent imaging.

Paediatric: weight estimate (age + 4) x 2 kg; fluid bolus 10-20 mL/kg crystalloid in children with shock, reassess after each.

DKA management: isotonic saline, insulin infusion 0.1 units/kg/h, potassium replacement once K+ <5.5, add dextrose when glucose <14 mmol/L.

Toxic alcohol (methanol/ethylene glycol) causes high anion gap with osmolar gap; treat with fomepizole or ethanol plus haemodialysis.

Acute upper GI bleed: resuscitate, transfuse to restrictive threshold (~70 g/L), start proton pump inhibitor, endoscopy within 24 h.

Ankle injury: Ottawa rules - malleolar tenderness, inability to weight-bear four steps, or tenderness at base of fifth metatarsal/navicular indicate need for radiography.

Heat stroke: core temperature >40 C with CNS dysfunction; cool rapidly, do not give antipyretics.

Heart auscultation: aortic area right second intercostal space, pulmonary left second, tricuspid left fourth, mitral apex fifth intercostal midclavicular line.

Lung lobes: right has three lobes and two fissures (oblique, horizontal); left has two lobes and one oblique fissure; lingula is left equivalent of middle lobe.

Inguinal hernia boundaries: anterior wall aponeurosis of external oblique, posterior wall transversalis fascia (reinforced medially by conjoint tendon).

Femoral nerve (L2-L4) supplies quadriceps and skin of anterior thigh and medial leg; obturator nerve (L2-L4) supplies medial compartment of thigh.

Circle of Willis: anterior communicating, paired anterior cerebral, internal carotid, posterior communicating, posterior cerebral, basilar.

Spleen lies in left hypochondrium against ribs 9-11; pain referred to left shoulder via phrenic nerve (Kehr sign) when ruptured.

Thyroid gland: recurrent laryngeal nerve lies in tracheo-oesophageal groove posterior to the gland; superior thyroid artery is a branch of external carotid.

Thrombosis vs embolism: thrombus forms in situ with lines of Zahn; embolus travels and lodges (pulmonary from deep veins, systemic from left heart or atheroma).

Infarction: red (venous, loose tissue, dual supply) vs pale (arterial, solid organs); brain and lung have dual supply so infarcts are often haemorrhagic.

Neoplasia: benign tumours are encapsulated and well differentiated; malignant tumours invade and metastasise; carcinoma = epithelial, sarcoma = mesenchymal.

Tumour markers are adjuncts not diagnoses: alpha-fetoprotein (hepatocellular, germ cell), CA-125 (ovarian), CEA (colorectal), calcitonin (medullary thyroid).

Hypersensitivity: type I IgE (anaphylaxis), II antibody-mediated (haemolysis), III immune complex (SLE, serum sickness), IV delayed T-cell (TB, contact dermatitis).

Cirrhosis: bridging fibrosis with regenerative nodules; portal hypertension leads to varices, splenomegaly, ascites and encephalopathy.

Nephrotic syndrome: proteinuria >3.5 g/day, hypoalbuminaemia, oedema, hyperlipidaemia; nephritic has haematuria and hypertension.

Cardiac cycle: systole includes isovolumetric contraction and ejection; diastole includes isovolumetric relaxation and filling; S1 from AV valve closure, S2 from semilunar closure.

Blood pressure = cardiac output x total peripheral resistance; baroreceptors in carotid sinus (glossopharyngeal) and aortic arch (vagus) buffer acute changes.

Lung volumes: tidal volume ~500 mL; vital capacity = inspiratory reserve + tidal + expiratory reserve; residual volume cannot be exhaled.

Ventilation-perfusion: apex has high V/Q (low perfusion), base has low V/Q (high perfusion); overall V/Q ~0.8.

Insulin lowers blood glucose by promoting cellular uptake and glycogen synthesis; glucagon raises it via glycogenolysis and gluconeogenesis.

Countercurrent mechanism in loop of Henle establishes medullary osmotic gradient; descending limb permeable to water, ascending limb pumps Na+/Cl- and is water-impermeable.

Resting membrane potential set mainly by K+ permeability (Nernst ~ -90 mV); depolarisation to threshold opens voltage-gated Na+ channels.

Thyroid hormones increase basal metabolic rate; calcitonin lowers serum calcium; parathyroid hormone raises it via bone, kidney and vitamin D activation.

Agonist potency relates to EC50 (lower = more potent); efficacy relates to maximal response; partial agonists have intermediate efficacy.

Local anaesthetics block voltage-gated Na+ channels; they are weak bases, so inflamed acidic tissue reduces their efficacy.

Loop diuretics (furosemide) inhibit Na+/K+/2Cl- cotransporter in ascending limb; thiazides act on distal convoluted tubule; spironolactone antagonises aldosterone.

Adrenaline: alpha-1 vasoconstriction, beta-1 cardiac stimulation, beta-2 bronchodilation; used in anaphylaxis and cardiac arrest.

Statins inhibit HMG-CoA reductase, reducing hepatic cholesterol synthesis and upregulating LDL receptors.

Opioids act on mu receptors causing analgesia, respiratory depression, miosis and constipation; naloxone is a competitive antagonist.

Antibiotic mechanisms: cell wall (penicillins, cephalosporins, vancomycin), protein synthesis (aminoglycosides, macrolides, tetracyclines), DNA/folate (quinolones, trimethoprim).

Therapeutic index = toxic dose / effective dose; narrow-index drugs (digoxin, lithium, warfarin, phenytoin) require monitoring.

Acute severe hypertension with end-organ damage (encephalopathy, aortic dissection, pulmonary oedema) requires controlled IV reduction; avoid rapid drops that cause cerebral or coronary ischaemia.

Aortic dissection: sudden tearing chest pain with pulse deficit or blood pressure differential; CT angiography diagnostic; blood pressure control with beta-blocker first.

Pulmonary embolism: Wells score guides D-dimer (low/intermediate probability) or CT pulmonary angiography; high-risk with haemodynamic instability needs thrombolysis.

Raised intracranial pressure: head elevation, normocapnia (PaCO2 ~35 mmHg), osmotherapy (mannitol or hypertonic saline), avoid hypotension and hypoxia.

Fracture management: analgesia, neurovascular assessment, immobilisation; open fractures need antibiotics and tetanus prophylaxis and early debridement.

Paediatric febrile seizure: most are simple (generalised, <15 min, once in 24 h); investigate source, not routine EEG or imaging.

Toxicology: activated charcoal within 1 h of ingestion for appropriate poisons, contraindicated if airway unprotected or hydrocarbon/corrosive ingestion.

Shoulder: rotator cuff comprises supraspinatus (abduction), infraspinatus (external rotation), teres minor (external rotation), subscapularis (internal rotation).

Knee: anterior cruciate ligament prevents anterior tibial translation; posterior cruciate prevents posterior translation; medial collateral resists valgus stress.

Carpal tunnel contents: median nerve and flexor tendons (flexor digitorum superficialis/profundus, flexor pollicis longus); ulnar nerve passes Guyon's canal.

Vertebral column: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 4 coccygeal; spinal cord ends at L1-L2 (conus medullaris); lumbar puncture below L3.

Pleura and lungs: visceral pleura adherent to lung, parietal to chest wall; intercostal neurovascular bundle runs in the costal groove (vein, artery, nerve from above down).

Facial nerve exits stylomastoid foramen and divides in parotid gland into temporal, zygomatic, buccal, marginal mandibular, cervical branches.

Biliary tree: common hepatic duct + cystic duct = common bile duct, which joins pancreatic duct at ampulla of Vater in second part of duodenum.

Cell adaptation: hypertrophy (increase in size), hyperplasia (increase in number), atrophy (decrease in size), metaplasia (change in type).

Ischaemia-reperfusion injury: restoration of flow generates reactive oxygen species, calcium overload and complement activation, worsening damage.

Shock types: hypovolaemic, cardiogenic, distributive (septic, anaphylactic, neurogenic), obstructive (tamponade, tension pneumothorax, massive PE).

Disseminated intravascular coagulation: widespread activation of coagulation with consumption of platelets and factors, causing both thrombosis and bleeding.

Granulomatous disease: caseating (TB) vs non-caseating (sarcoidosis, Crohn disease); giant cells at periphery of granuloma.

Diabetes mellitus: type 1 autoimmune beta-cell destruction; type 2 insulin resistance with relative deficiency; microvascular complications (retinopathy, nephropathy, neuropathy).

Oedema mechanisms: increased hydrostatic pressure, reduced plasma oncotic pressure, lymphatic obstruction, sodium retention, increased vascular permeability.

Cardiac output is product of heart rate and stroke volume; stroke volume determined by preload, afterload and contractility.

Renal blood flow ~20% of cardiac output; autoregulation maintains flow over a range of perfusion pressures via afferent arteriolar tone.

Respiratory control: central chemoreceptors respond to PaCO2/pH in cerebrospinal fluid; peripheral chemoreceptors (carotid body) respond to hypoxia.

Body fluid compartments: total body water ~60% of body weight; intracellular ~40%, extracellular ~20% (interstitial ~15%, plasma ~5%).

Glomerular filtration rate ~125 mL/min; filtration fraction = GFR / renal plasma flow (~0.2).

Haemostasis: vascular spasm, platelet plug formation, coagulation cascade, fibrinolysis; vitamin K-dependent factors II, VII, IX, X.

Gastrointestinal secretion: gastric parietal cells secrete HCl stimulated by histamine, gastrin and acetylcholine; intrinsic factor needed for B12 absorption.

Temperature regulation: hypothalamus integrates; heat loss via radiation, conduction, convection, evaporation; sweating is the main evaporative mechanism.

Pharmacokinetics ADME: absorption, distribution, metabolism (mainly hepatic phase I oxidation and phase II conjugation), excretion (mainly renal).

Renal clearance of a drug equals GFR for freely filtered unbound drug; secretion and reabsorption modify it.

Protein binding: only unbound drug is pharmacologically active; displacement raises free fraction and can cause toxicity (e.g., warfarin with sulfonamides).

Beta-1 selective antagonists (metoprolol, bisoprolol) reduce cardiac rate and contractility; non-selective also block beta-2 causing bronchospasm.

Angiotensin-converting enzyme inhibitors reduce angiotensin II and raise bradykinin, causing cough and angioedema; contraindicated in pregnancy and bilateral renal artery stenosis.

Antiplatelet drugs: aspirin irreversibly inhibits cyclo-oxygenase-1; clopidogrel blocks P2Y12 ADP receptor; glycoprotein IIb/IIIa inhibitors block platelet aggregation.

Antidotes: N-acetylcysteine (paracetamol), naloxone (opioids), flumazenil (benzodiazepines), atropine (organophosphates/cholinesterase), hydroxocobalamin (cyanide).

Antiepileptics: phenytoin shows saturation kinetics and zero-order metabolism at high doses; monitor levels and watch for gingival hyperplasia.

Trauma: log-roll to examine back, apply pelvic binder for suspected pelvic fracture, avoid repeated log-rolls; FAST scan for free intraperitoneal fluid.

Acute limb ischaemia: 6 Ps (pain, pallor, pulselessness, paraesthesia, paralysis, perishing cold); immediate vascular referral, heparin and analgesia.

Burns airway: hoarseness, stridor, soot in sputum, singed nasal hair, facial burns suggest inhalation injury requiring early intubation.

Cardiogenic pulmonary oedema: sit up, oxygen, nitrates if systolic BP adequate, non-invasive ventilation; diuretics only if fluid overloaded.

Anaphylaxis in children: IM adrenaline 0.01 mg/kg (max 0.5 mg) of 1:1000 into anterolateral thigh.

Acute coronary syndrome in patients with STEMI: aspirin 300 mg chewed, plus P2Y12 inhibitor, anticoagulation, and reperfusion; avoid nitrates in right ventricular infarction.

Carbon monoxide poisoning: treat with high-flow oxygen; hyperbaric oxygen for severe poisoning, neurological signs, or pregnancy; pulse oximetry is falsely normal.

Cervical spine: C1 (atlas) has no body and articulates with occipital condyles; C2 (axis) has the dens (odontoid process); atlantoaxial joint allows rotation.

Arm: brachial artery lies medial to biceps tendon; it divides into radial and ulnar arteries at the cubital fossa; radial artery is palpable at the wrist.

Thoracic: diaphragm attaches to xiphoid, lower six ribs and costal cartilages, and L1-L3 vertebrae; phrenic nerve (C3-C5) supplies it.

Pelvis: sacroiliac joint transmits weight from spine to lower limbs; pubic symphysis is a secondary cartilaginous joint; obturator nerve exits obturator foramen.

Abdominal aorta branches: coeliac trunk (T12), superior mesenteric (L1), renal arteries (L1-L2), inferior mesenteric (L3), bifurcates at L4.

Cranial fossae: anterior (frontal lobe), middle (temporal lobe, pituitary), posterior (cerebellum, brainstem); foramen magnum transmits medulla and vertebral arteries.

Posterior triangle of neck: bounded by sternocleidomastoid, trapezius and clavicle; contains accessory nerve, brachial plexus and subclavian vessels.

Atheroma risk factors: smoking, diabetes, hypertension, hyperlipidaemia, family history; plaque rupture triggers acute coronary syndrome.

Myocardial infarction: coagulative necrosis begins ~6 h, neutrophil infiltrate 1-3 days, granulation tissue 1-2 weeks, fibrous scar by 6-8 weeks.

Pneumonia: lobar (Streptococcus pneumoniae) with consolidation; bronchopneumonia patchy; atypical (Mycoplasma) with interstitial pattern.

Cirrhosis complications: portal hypertension, ascites, spontaneous bacterial peritonitis, variceal bleeding, hepatic encephalopathy, hepatocellular carcinoma.

Tumour spread: local invasion, lymphatic (carcinoma), haematogenous (sarcoma, also renal cell, follicular thyroid), transcoelomic (ovarian, gastric).

Anaemia classification: microcytic (iron deficiency, thalassaemia), normocytic (chronic disease, haemolysis), macrocytic (B12, folate deficiency).

Autoimmune disease: loss of tolerance, HLA associations (e.g., HLA-B27 with ankylosing spondylitis), often female predominance.

Cardiac output, preload, afterload: increased afterload reduces stroke volume for a given contractility; vasodilators improve output in heart failure.

Oxygen-haemoglobin curve: sigmoid shape reflects cooperative binding; P50 is the partial pressure at 50% saturation (~26-27 mmHg).

Ventilation increases with exercise, hypoxia, hypercapnia and acidosis; hypoxic drive is important in chronic CO2 retainers.

Renal handling of glucose: reabsorption in proximal tubule via SGLT; renal threshold ~10 mmol/L, above which glucosuria occurs.

Hormones: cortisol from adrenal cortex raises glucose and suppresses inflammation; catecholamines from adrenal medulla raise heart rate and blood pressure.

Muscle physiology: fast-twitch (type II) fibres for power, slow-twitch (type I) for endurance; tetany occurs with high-frequency stimulation.

Blood: haemoglobin ~13-17 g/dL male, 12-15 female; platelets 150-400 x 10^9/L; white cells 4-11 x 10^9/L.

Cardiac output distribution at rest: ~20% to kidneys, ~15% to brain, ~5% to heart, ~25% to liver/gut.

Pharmacodynamics: drug-receptor interaction; agonists activate, antagonists block; reversible vs irreversible binding determines duration.

Dose-response: log dose-response curve is sigmoid; ED50 is dose producing 50% of maximal effect.

First-pass effect: oral drugs absorbed into portal circulation are metabolised by liver before reaching systemic circulation; reduces oral bioavailability.

Antihypertensives: ACE inhibitors/ARBs, calcium channel blockers (dihydropyridines vasodilate, non-dihydropyridines slow heart rate), thiazides, beta-blockers.

Anticoagulants: heparin (parenteral, aPTT), low-molecular-weight heparin (anti-Xa), warfarin (INR), direct oral anticoagulants (factor Xa or thrombin inhibitors).

Corticosteroids: anti-inflammatory and immunosuppressive; long-term use causes osteoporosis, hyperglycaemia, hypertension and adrenal suppression.

Antiemetics: ondansetron (5-HT3 antagonist), metoclopramide (dopamine antagonist, prokinetic), cyclizine (H1), dexamethasone.

Drug interactions: warfarin with antibiotics alters INR; statins with macrolides increase myopathy risk; MAOIs with sympathomimetics cause hypertensive crisis.

Shock: recognise by tachycardia, tachypnoea, cool peripheries, prolonged capillary refill, altered mental state; treat cause and restore perfusion.

Cervical spine clearance: no high-risk features, no distracting injury, no neurological deficit, able to actively rotate neck 45 degrees both ways (Canadian C-spine rule).

Acute abdomen: serial examination, early surgical review; perforation shows free gas on erect chest radiograph; peritonism indicates surgical emergency.

Paediatric dehydration: assess weight loss, skin turgor, mucous membranes, capillary refill, tears; oral rehydration preferred, IV if severe.

Electrolyte emergencies: hyperkalaemia with ECG changes (peaked T waves, wide QRS) needs IV calcium, insulin-dextrose, salbutamol; severe hyponatraemia with seizures needs hypertonic saline.

Head injury anticoagulation: reverse with vitamin K and prothrombin complex concentrate if intracranial haemorrhage; CT within 8 h regardless of symptoms.

Rhabdomyolysis: dark urine, raised creatine kinase, risk of acute kidney injury and hyperkalaemia; treat with aggressive IV fluids.

Lower limb compartments: anterior (deep fibular nerve), lateral (superficial fibular), posterior superficial (tibial), posterior deep (tibial); compartment syndrome risks.

Femoral canal: medial to femoral vein, contains lymphatics; site of femoral hernia, more common in women and at risk of strangulation.

Heart valves: tricuspid (right AV), pulmonary (right semilunar), mitral (left AV), aortic (left semilunar); auscultation sites differ from anatomical positions.

Brain lobes: frontal (motor, executive), parietal (sensory), temporal (hearing, memory), occipital (vision); Broca and Wernicke areas in dominant hemisphere.

Renal anatomy: kidneys at T12-L3, right lower than left; hilum transmits renal vein (anterior), renal artery (middle), ureter (posterior).

Scapula: spine of scapula, acromion, coracoid process, glenoid cavity, suprascapular notch (suprascapular nerve).

Hip joint: ball-and-socket, supplied by medial circumflex femoral artery (retinacular branches); fracture risks avascular necrosis of femoral head.

Cellular injury: reversible (swelling, fatty change) vs irreversible (nuclear pyknosis, karyolysis, karyorrhexis, membrane rupture).

Free radical injury: lipid peroxidation, protein and DNA damage; antioxidants include glutathione, superoxide dismutase, catalase.

Neoplasia nomenclature: adenoma (glandular benign), papilloma (surface), lipoma (fat); carcinoma (epithelial malignant), sarcoma (mesenchymal), lymphoma (lymphoid).

Carcinogenesis: initiation (mutation), promotion (proliferation), progression (additional mutations); oncogenes (RAS, MYC) and tumour suppressors (p53, RB, APC).

Inflammation: acute (neutrophils, exudate, vasodilation) vs chronic (lymphocytes, macrophages, fibrosis); granulomatous when macrophages predominate.

Haemostasis and thrombosis: Virchow's triad; arterial thrombi are pale and platelet-rich, venous thrombi are red and fibrin-rich.

Genetic disease: autosomal dominant (Huntington, Marfan, familial hypercholesterolaemia), autosomal recessive (cystic fibrosis, sickle cell), X-linked (haemophilia, Duchenne).

Cardiovascular: cardiac output = heart rate x stroke volume; blood pressure = cardiac output x peripheral resistance.

Respiratory: gas exchange by diffusion; oxygen carried mostly by haemoglobin, carbon dioxide as bicarbonate (~70%).

Renal: nephron segments; proximal tubule reabsorbs ~65% of filtered Na+ and water; loop of Henle creates medullary gradient; collecting duct under ADH control.

Acid-base: respiratory acidosis (raised CO2), respiratory alkalosis (low CO2), metabolic acidosis (low HCO3-), metabolic alkalosis (high HCO3-); compensation changes the other parameter.

Endocrine: insulin lowers glucose, glucagon raises it; thyroid hormones increase metabolic rate; cortisol raises glucose and is anti-inflammatory.

Nerve conduction: action potential all-or-none; refractory periods; myelination increases conduction velocity via saltatory conduction.

Gastrointestinal: peristalsis, secretion, absorption; small intestine main site of absorption (duodenum iron, ileum B12 and bile salts).

Thermoregulation: hypothalamus controls; fever is a raised set point due to pyrogens, not simply overheating.

Receptor types: ligand-gated ion channels (fast, nicotinic), G-protein coupled (adrenergic, muscarinic), kinase-linked (insulin), nuclear (steroid, thyroid).

Sympathomimetics: alpha-1 (vasoconstriction), alpha-2 (presynaptic inhibition), beta-1 (cardiac), beta-2 (bronchodilation, uterine relaxation).

Parasympathomimetics: muscarinic effects (bradycardia, secretions, bronchoconstriction, miosis); anticholinergics reverse these.

Antibiotic resistance: beta-lactamase production, altered penicillin-binding proteins, efflux pumps, reduced permeability; combination therapy and stewardship.

Analgesia: paracetamol, NSAIDs for mild-moderate; opioids for severe; multimodal analgesia; avoid NSAIDs in renal impairment and peptic ulcer.

Anaesthesia: induction (propofol, thiopentone), maintenance (volatile agents), muscle relaxation (suxamethonium depolarising, non-depolarising agents).

Chemotherapy: alkylating agents, antimetabolites, anthracyclines, taxanes; side effects include myelosuppression, mucositis, alopecia, cardiotoxicity.

Vaccines and immunisation: live attenuated (MMR, BCG), inactivated (influenza), toxoid (tetanus); live vaccines contraindicated in immunosuppression and pregnancy.