EDAIC flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Oxygen content formula

CaO2 = 1.34 × Hb × SaO2 + 0.003 × PaO2. At normal haemoglobin, dissolved oxygen contributes little; anaemia lowers content even with normal saturation.

Context-sensitive half-time

Time for plasma concentration to halve after stopping an infusion. It rises with infusion duration for lipophilic drugs but stays short and predictable for remifentanil and propofol.

Nernst equation

E = (61.5/z) × log([ion]out/[ion]in) mV at 37 °C. It predicts the equilibrium potential for an ion; the resting membrane potential lies near the potassium equilibrium potential.

Starling equation

Jv = Kf[(Pc − Pi) − σ(πc − πi)]. Capillary hydrostatic pressure drives filtration; plasma oncotic pressure opposes it; increased permeability raises Kf and lowers the reflection coefficient.

Local anaesthetic ionisation

Local anaesthetics are weak bases; only the uncharged form crosses the axon membrane. Acidic inflamed tissue increases the charged fraction and reduces block efficacy.

Rightward oxygen curve shift

Increased 2,3-DPG, hydrogen ions, carbon dioxide and temperature reduce haemoglobin oxygen affinity, shifting the curve right and favouring oxygen unloading to tissues.

Hypoxic pulmonary vasoconstriction

Alveolar hypoxia constricts small pulmonary arteries, diverting blood from poorly ventilated lung to better-ventilated regions. Volatile anaesthetics and vasodilators blunt this response, worsening shunt.

Clearance and half-life

t½ = 0.693 × Vd/CL. A large volume of distribution or low clearance prolongs half-life; this explains delayed recovery in obesity and hepatic or renal impairment.

Functional residual capacity

Volume of gas remaining in the lungs after a normal expiration. It is reduced by supine position, obesity, pregnancy, general anaesthesia and abdominal surgery, promoting atelectasis and shunt.

Neuromuscular junction transmission

Acetylcholine binds nicotinic receptors, depolarising the motor endplate and opening voltage-gated sodium channels. Non-depolarising blockers compete; suxamethonium is a partial agonist causing fasciculations.

Bainbridge reflex

Atrial stretch from increased venous return raises heart rate via vagal afferents. It explains tachycardia with rapid fluid loading and opposes the baroreceptor-mediated bradycardia of hypertension.

Henderson–Hasselbalch equation

pH = 6.1 + log([HCO3-]/(0.03 × PaCO2)). It shows how bicarbonate and carbon dioxide determine pH and underpins interpretation of arterial blood gases.

Renal autoregulation

Renal blood flow is held near constant across mean arterial pressures of roughly 80–180 mmHg by afferent arteriolar myogenic tone and tubuloglomerular feedback. Hypotension below this range causes ischaemia.

Malignant hyperthermia treatment

Stop triggers, hyperventilate with 100% oxygen, give dantrolene 2.5 mg/kg IV repeated to 10 mg/kg, actively cool, and treat hyperkalaemia and arrhythmias with standard measures.

Anaphylaxis adrenaline dose

Adult IV dose is 50 micrograms (0.5 mL of 1:10,000), repeated every 5 minutes as needed. Remove the trigger, give fluids, and sample tryptase after resuscitation.

CICO emergency management

Cannot intubate, cannot oxygenate: declare emergency, give 100% oxygen, and perform scalpel–bougie–tube cricothyroidotomy. Oxygenation takes priority over intubation attempts.

Lipid emulsion for LAST

For local anaesthetic systemic toxicity give 20% lipid emulsion 1.5 mL/kg bolus then 15 mL/kg/h. Avoid vasopressin, calcium channel blockers, beta-blockers and further local anaesthetic.

Sepsis initial resuscitation

Give broad-spectrum antibiotics within 1 hour, crystalloid 30 mL/kg for hypotension or lactate ≥4 mmol/L, and noradrenaline to maintain mean arterial pressure ≥65 mmHg.

Apfel PONV score

Four risk factors: female sex, non-smoker, history of PONV or motion sickness, and postoperative opioids. Each adds roughly 20% risk; three or more warrants multimodal prophylaxis.

Perioperative myocardial infarction

Troponin elevation with ischaemic symptoms or ECG changes defines infarction. Type 1 is plaque rupture; type 2 reflects supply–demand mismatch from hypotension, anaemia or tachycardia.

KDIGO AKI staging

Stage 1: creatinine 1.5–1.9× baseline or urine output <0.5 mL/kg/h for 6 hours. Stage 2: 2.0–2.9× or 12 hours. Stage 3: ≥3×, renal replacement therapy or 24 hours.

Acute respiratory distress syndrome

Berlin criteria: onset within 1 week, bilateral opacities, respiratory failure not fully explained by cardiac failure, and PaO2/FiO2 ≤300 mmHg on PEEP ≥5 cmH2O.

Lung-protective ventilation

Tidal volume 6 mL/kg predicted body weight, plateau pressure ≤30 cmH2O, driving pressure ≤15 cmH2O, and appropriate PEEP reduce ventilator-induced lung injury in ARDS.

Difficult airway extubation

Assess risk factors, plan reintubation, use an airway exchange catheter or staged extubation, and ensure equipment and personnel for immediate re-intubation are present.

Rapid sequence induction

Preoxygenate, give a rapid-onset induction agent with a neuromuscular blocker such as rocuronium 1.2 mg/kg or suxamethonium 1.5 mg/kg, and intubate without bag-mask ventilation.

Local anaesthetic maximum doses

Common adult limits: lidocaine 3 mg/kg plain or 7 mg/kg with adrenaline; bupivacaine 2 mg/kg; ropivacaine 3 mg/kg. Add adrenaline to slow absorption and prolong block.

Neuraxial hypotension

Sympathetic blockade causes venodilation and reduced venous return. Treat with fluids, left uterine displacement in pregnancy, and vasopressors such as phenylephrine or noradrenaline.

Postoperative delirium

Acute fluctuating inattention and altered cognition after surgery. Risk rises with age, cognitive impairment, sensory deprivation and anticholinergic drugs; prevention targets orientation, analgesia and early mobilisation.

Massive transfusion protocol

Give balanced red cells, plasma and platelets, limit crystalloid, keep calcium and temperature normal, and use tranexamic acid early in trauma. Monitor for hypocalcaemia, hyperkalaemia and coagulopathy.

Preoperative fasting rules

Clear fluids up to 2 hours, breast milk 4 hours, and light meal or formula 6 hours before anaesthesia. Prolonged fasting offers no benefit and increases dehydration and discomfort.

Bier block

Intravenous regional anaesthesia: exsanguinate the limb, inflate a tourniquet, inject local anaesthetic into a distal vein, and keep the tourniquet inflated at least 20 minutes to limit systemic toxicity.

Post-dural puncture headache

Positional headache from CSF leak after dural puncture. Conservative treatment, caffeine, and an epidural blood patch for persistent symptoms; spontaneous resolution usually occurs within a week.