UHS DES Entrance Exam cheat sheet

The brachial plexus arises from roots C5–T1; its cords (lateral, medial, posterior) are named by their relation to the second part of the axillary artery.

The median nerve (C5–T1) supplies all thenar muscles except adductor pollicis and the deep head of flexor pollicis brevis, which are ulnar-innervated.

Femoral triangle, lateral to medial: femoral nerve, artery, vein, empty space and lymphatics; floor is iliacus, pectineus and adductor longus, roof the fascia lata.

The inguinal canal is about 4 cm long; the deep ring lies lateral to the inferior epigastric artery, the superficial ring above and medial to the pubic tubercle.

Dermatome landmarks: C6 thumb, T4 nipple, T10 umbilicus, L1 inguinal ligament, L4 medial malleolus, S1 lateral border of the foot.

The right main bronchus is wider, shorter and more vertical, so aspirated material lodges there more often than in the left.

Porta hepatis arrangement: portal vein posterior, proper hepatic artery to the left, common bile duct anterior and to the right.

The ureter has three constrictions - pelviureteric junction, crossing of the common iliac artery bifurcation, and vesicoureteric junction - the sites where calculi lodge.

The cricothyroid membrane lies between the thyroid and cricoid cartilages and is the adult site for an emergency surgical airway.

Cardiac output = heart rate × stroke volume; mean arterial pressure = CO × systemic vascular resistance = diastolic BP + 1/3 (systolic − diastolic BP).

Arterial oxygen content = (1.34 × haemoglobin × SaO2) + (0.003 × PaO2); oxygen delivery = cardiac output × CaO2 × 10.

Henderson–Hasselbalch: pH = 6.1 + log([HCO3−] / (0.03 × PaCO2)); normal arterial pH is 7.35–7.45.

Anion gap = Na+ − (Cl− + HCO3−), normally 8–12 mmol/L; a raised gap suggests lactic acidosis, ketoacidosis, renal failure or toxin ingestion.

GFR = filtration coefficient × net filtration pressure; net pressure = glomerular capillary hydrostatic − (plasma oncotic + capsular hydrostatic).

Frank–Starling relationship: within physiological limits, greater end-diastolic volume increases stroke volume; excessive filling eventually reduces it.

The thick ascending limb is water-impermeable and uses Na-K-2Cl cotransport; it is the site of loop diuretic action and the engine of the countercurrent multiplier.

Compliance = ΔV/ΔP; by Laplace law (P = 2T/r) small alveoli need surfactant to avoid collapse.

Insulin lowers blood glucose by GLUT4 translocation, glycogen synthesis and lipogenesis; glucagon raises it through glycogenolysis and gluconeogenesis.

Glycolysis converts glucose to 2 pyruvate with a net gain of 2 ATP and 2 NADH; phosphofructokinase-1 is rate-limiting, inhibited by ATP and citrate and activated by AMP and fructose-2,6-bisphosphate.

Each acetyl-CoA entering the TCA cycle yields 3 NADH, 1 FADH2 and 1 GTP; complete oxidation of one glucose yields about 30–32 ATP.

Km is the substrate concentration at half-maximal velocity; a low Km indicates high affinity. On a Lineweaver–Burk plot the x-intercept is −1/Km.

The hexose monophosphate shunt generates NADPH and ribose-5-phosphate; G6PD deficiency impairs glutathione regeneration and causes haemolysis after oxidative stress (fava beans, primaquine).

Urea cycle: carbamoyl phosphate synthetase I is rate-limiting, activated by N-acetylglutamate; the cycle costs 4 ATP per urea and links to the TCA cycle via fumarate.

Phenylketonuria results from phenylalanine hydroxylase deficiency; management is a phenylalanine-restricted diet with tyrosine supplementation, detected by neonatal screening.

Rate-limiting enzymes: phosphofructokinase-1 (glycolysis), fructose-1,6-bisphosphatase (gluconeogenesis), glycogen synthase (glycogen synthesis), HMG-CoA reductase (cholesterol synthesis).

Thiamine pyrophosphate is a cofactor for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and transketolase; deficiency causes beriberi and Wernicke encephalopathy.

Vitamin C is required for prolyl and lysyl hydroxylation of collagen; deficiency causes scurvy with bleeding gums and poor wound healing.

Virchow triad: endothelial injury, abnormal blood flow (stasis or turbulence) and hypercoagulability.

Oncogenes (RAS, MYC, HER2) need a single activating hit; tumour suppressors (TP53, RB, APC, BRCA1/2) require loss of both alleles.

The intrinsic pathway is measured by aPTT and the extrinsic pathway by PT/INR; heparin acts via antithrombin (aPTT), warfarin by inhibiting vitamin K recycling (INR).

Necrosis causes cell swelling, membrane rupture and inflammation; apoptosis is caspase-dependent, energy-requiring and non-inflammatory.

Amyloid is confirmed by Congo red staining showing apple-green birefringence under polarised light; it consists of misfolded β-pleated sheet proteins.

Metaplasia → dysplasia → carcinoma in situ → invasive carcinoma is the classic progression in squamous epithelium such as bronchus and cervix.

Grade describes tumour differentiation while stage describes anatomical spread (TNM); stage is the stronger prognostic factor for most solid tumours.

Hyperplasia is an increase in cell number and hypertrophy an increase in cell size; both are usually reversible adaptations, unlike neoplasia.

First-order elimination removes a constant fraction per unit time so half-life is constant; zero-order elimination removes a constant amount per unit time (ethanol, phenytoin, high-dose aspirin).

Volume of distribution = dose / plasma concentration; loading dose = (Vd × target concentration) / bioavailability; maintenance dose rate = clearance × target concentration.

Warfarin inhibits vitamin K epoxide reductase, is monitored by INR, and is reversed with vitamin K plus prothrombin complex concentrate.

Unfractionated heparin potentiates antithrombin III, is monitored by aPTT, and is reversed with protamine sulphate.

Antidotes: N-acetylcysteine for paracetamol, folinic acid for methotrexate, naloxone for opioids, flumazenil for benzodiazepines, fomepizole or ethanol for methanol and ethylene glycol.

Aminoglycosides are bactericidal 30S inhibitors, poorly absorbed orally, and cause nephrotoxicity and ototoxicity; they act synergistically with β-lactams.

β1-selective blockers (metoprolol, atenolol) are preferred in bronchospastic disease; esmolol has a very short half-life and suits acute rate control.

CYP3A4 inhibitors such as grapefruit juice, ketoconazole and erythromycin raise levels of substrates including statins and ciclosporin.

Antibiotic target sites: 30S - aminoglycosides (misreading) and tetracyclines (block tRNA binding); 50S - macrolides, chloramphenicol, clindamycin.

Gram-positive cocci in clusters that are catalase and coagulase positive indicate Staphylococcus aureus; coagulase-negative staphylococci are usually skin flora except S. lugdunensis.

Streptococcus pyogenes is Group A, β-haemolytic and bacitracin-sensitive; post-infectious sequelae are rheumatic fever and post-streptococcal glomerulonephritis.

Mycobacterium tuberculosis is acid-fast on Ziehl–Neelsen staining and grows on Löwenstein–Jensen medium, with culture taking 4–8 weeks.

Hepatitis B serology: HBsAg = current infection, anti-HBs = immunity, HBeAg = high infectivity, IgM anti-HBc = acute infection, anti-HBc IgG = past exposure.

HIV gp120 binds CD4 on helper T cells and macrophages; screening ELISA is confirmed by Western blot or HIV RNA PCR.

Endotoxin is lipopolysaccharide of the gram-negative outer membrane, heat-stable, and signals through TLR4 causing fever and shock; exotoxins are heat-labile proteins.

Autoclave standard: 121 °C at 15 psi for 15 minutes; biological controls use Geobacillus stearothermophilus spores, and indicator tape is only a process marker.

Plasmodium falciparum shows banana-shaped gametocytes and causes severe malaria (cerebral malaria, hypoglycaemia, blackwater fever); diagnosis uses thick and thin films.

Selective media: MacConkey for gram-negative bacilli, mannitol salt agar for staphylococci, blood agar for streptococci and for haemolysis patterns.

Diabetes diagnosis: fasting plasma glucose ≥126 mg/dL, 2-hour OGTT or random glucose ≥200 mg/dL with symptoms, or HbA1c ≥6.5 %; confirm with a repeat test unless unequivocal.

STEMI reperfusion: primary PCI within 90 minutes of first medical contact, or fibrinolysis within 30 minutes if PCI is unavailable and there is no contraindication.

CURB-65 for pneumonia: confusion, urea >7 mmol/L, respiratory rate ≥30/min, systolic BP <90 or diastolic ≤60 mmHg, age ≥65; 0–1 outpatient, 2 consider admission, ≥3 severe.

Nephrotic syndrome: proteinuria >3.5 g/day, albumin <3 g/dL, oedema, hyperlipidaemia. Nephritic syndrome: haematuria, red cell casts, hypertension, oliguria.

Hyperkalaemia with ECG changes: give IV calcium gluconate first to stabilise the myocardium, then insulin–dextrose and salbutamol; dialysis for refractory or renal failure cases.

Primary hypothyroidism shows raised TSH with low free T4; subclinical hypothyroidism is a raised TSH with normal free T4.

Anaemia by MCV: microcytic <80 fL (iron deficiency, thalassaemia, anaemia of chronic disease), normocytic 80–100 fL, macrocytic >100 fL (B12, folate, alcohol, hypothyroidism).

Asthma: inhaled corticosteroid-containing therapy is the cornerstone; SABA-only treatment is no longer recommended for routine maintenance in adults and adolescents.

Acute coronary syndrome: 12-lead ECG within 10 minutes of arrival and chewed aspirin 300 mg, plus a P2Y12 inhibitor and anticoagulation for most patients.

ATLS primary survey follows A-B-C-D-E with cervical spine protection; permissive hypotension is acceptable in penetrating trauma without head injury until bleeding is controlled.

Acute appendicitis: periumbilical pain migrating to the right iliac fossa, McBurney point tenderness, positive Rovsing, psoas and obturator signs; ultrasound or CT confirms.

Parkland formula: 4 mL × body weight (kg) × % total body surface area burnt over 24 hours, half in the first 8 hours from injury, using Ringer lactate; urine output target 0.5–1 mL/kg/hour.

Indirect inguinal hernia passes lateral to the inferior epigastric vessels through the deep ring; a direct hernia passes medial to them through Hesselbach triangle.

Postoperative fever timing: atelectasis and pneumonia days 1–2, urinary infection days 3–5, wound infection days 5–7, deep vein thrombosis after day 7; drugs cause drug fever at any time.

Thyroidectomy risks: recurrent laryngeal nerve injury (hoarseness), external branch of the superior laryngeal nerve (voice fatigue), hypocalcaemia from parathyroid injury, and haematoma causing airway obstruction.

Small bowel anastomosis needs 3–4 cm of serosal apposition; colonic repair demands adequate blood supply and a tension-free technique because leak risk is higher.

Acute cholecystitis: right upper quadrant pain, positive Murphy sign, fever and leucocytosis; ultrasound shows wall thickening >3 mm and pericholecystic fluid.

Haemorrhagic shock classes by blood loss: class I <15 %, class II 15–30 % (tachycardia), class III 30–40 % (hypotension), class IV >40 % (marked hypotension, anuria).

Sepsis-3: sepsis = suspected infection with a SOFA score rise ≥2; septic shock = vasopressors required to keep MAP ≥65 mmHg plus lactate >2 mmol/L despite adequate fluids.

qSOFA bedside screen: respiratory rate ≥22/min, altered mentation (GCS <15), systolic BP ≤100 mmHg; two or more positive criteria flag high risk.

Adult CPR: 30 compressions to 2 ventilations, rate 100–120/min, depth 5–6 cm, full chest recoil, interruptions under 10 seconds.

Shockable rhythms (ventricular fibrillation, pulseless VT) receive immediate defibrillation; asystole and pulseless electrical activity receive CPR and adrenaline and are never shocked.

Anaphylaxis: IM adrenaline 0.5 mg (0.5 mL of 1:1000) into the anterolateral thigh, repeated every 5 minutes; fluids, oxygen, antihistamine and steroid follow, never replace, adrenaline.

Glasgow Coma Scale 3–15: eyes 1–4, verbal 1–5, motor 1–6; a score of 8 or less indicates the need for airway protection.

DKA management: isotonic saline, fixed-rate insulin infusion, potassium replacement once K+ <5.5 mmol/L, and treatment of the precipitant; cerebral oedema is a paediatric risk.

Organophosphate poisoning: cholinergic excess with bradycardia and SLUDGE; give atropine titrated until secretions dry, plus early pralidoxime.

Naloxone reverses opioid respiratory depression but its half-life is shorter than many opioids, so patients need observation for re-sedation.

Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV = TP/(TP+FP); NPV = TN/(TN+FN). PPV and NPV change with prevalence; sensitivity and specificity do not.

Prevalence ≈ incidence × mean duration of disease; prevalence falls with cure or death, whereas incidence measures new cases per population at risk per time.

Cohort studies yield relative risk; case-control studies yield odds ratio; attributable risk = incidence in exposed − incidence in unexposed.

Herd immunity threshold = 1 − 1/R0; measles (R0 12–18) needs roughly 92–95 % coverage to interrupt transmission.

Levels of prevention: primary (immunisation, sanitation), secondary (screening, early treatment), tertiary (rehabilitation, disability limitation).

Infant mortality rate = deaths under 1 year per 1000 live births in the same year; maternal mortality ratio = maternal deaths per 100,000 live births.

Cold chain: OPV at −20 °C, most other vaccines at +2 to +8 °C; freeze-sensitive vaccines (hepatitis B, DPT, tetanus) must never be frozen.

Screening criteria (Wilson and Jungner): important disease, accepted treatment, detectable latent stage, suitable test, agreed policy, cost-effective.

Endemic = constant usual occurrence; epidemic = cases above the expected level; pandemic = epidemic spreading across continents.