ExAC cheat sheet

Difficult airway prediction: Mallampati III–IV, thyromental distance <6 cm (3 fingerbreadths), mouth opening <3 cm, limited cervical extension, short thick neck, and prior difficult intubation each raise risk; no single test is sensitive alone.

Laryngoscopy: align oral, pharyngeal, and laryngeal axes; sniffing position uses ~25° lower cervical flexion and ~15° atlanto-occipital extension; optimal laryngeal view (Cormack-Lehane grade 1) exposes the glottis fully.

Cormack-Lehane grades: 1 = full glottis visible, 2 = partial glottis/posterior commissure, 3 = epiglottis only, 4 = no laryngeal structures; grade 3–4 predicts difficult intubation.

Failed airway algorithm: optimize first attempt (positioning, suction, BURP, bougie), limit attempts to avoid trauma and edema, then supraglottic rescue device, then surgical airway (cricothyrotomy) if cannot intubate/cannot oxygenate.

Cricothyrotomy landmarks: identify cricothyroid membrane between thyroid and cricoid cartilage; standard 6.0 cuffed tube in adults; contraindicated in children under ~8–12 years (use needle or surgical approach per protocol).

Supraglottic devices (LMA) seal at the hypopharynx and protect less against aspiration than a cuffed ETT; contraindicated with full stomach, high aspiration risk, or low pulmonary compliance.

Confirmation of tracheal placement: continuous waveform capnography is the gold standard; auscultation, chest rise, and tube fogging are adjuncts and can be falsely reassuring.

Preoxygenation: 3–5 minutes of tidal-volume breathing or 8 vital-capacity breaths of 100% O2 raises functional residual capacity oxygen stores and prolongs safe apnea time, especially in obesity and pregnancy.

Minute ventilation = tidal volume × respiratory rate; normal adult ~6–8 L/min; alveolar ventilation = (tidal volume − dead space) × rate.

Dead space: anatomic (~150 mL) plus alveolar; increased by hypotension, pulmonary embolism, and excessive PEEP; V/Q mismatch drives hypoxemia while hypoventilation drives hypercapnia.

Oxygen content CaO2 = (1.34 × Hb × SaO2) + (0.003 × PaO2); dissolved oxygen contributes little, so anemia and low saturation dominate oxygen delivery.

Oxygen delivery DO2 = cardiac output × CaO2; hypoxemia, anemia, low output, and high metabolic demand each threaten tissue oxygenation.

Pulse oximetry: reads saturation, not ventilation; falsely normal with carboxyhemoglobin (reads ~normal despite CO), methemoglobin (reads ~85%), poor perfusion, and nail polish.

Capnography waveform: end-tidal CO2 normally 35–45 mmHg; sudden drop suggests disconnection, obstruction, or cardiac arrest; gradual rise suggests hypoventilation or hypermetabolism.

Ventilator modes: volume control guarantees tidal volume but risks barotrauma; pressure control limits peak pressure but tidal volume varies with compliance; SIMV and PSV support spontaneous effort.

Lung-protective ventilation: tidal volume 6–8 mL/kg predicted body weight, plateau pressure <30 cmH2O, and permissive hypercapnia reduce ventilator-induced lung injury.

Cardiac output = heart rate × stroke volume; stroke volume depends on preload, afterload, and contractility (Frank-Starling relationship).

Mean arterial pressure ≈ diastolic + 1/3 (systolic − diastolic); MAP ≥65 mmHg is a common perfusion target in shock and critical care.

Shock categories: hypovolemic (low preload), cardiogenic (low contractility), distributive (low afterload, e.g., sepsis), and obstructive (tamponade, tension pneumothorax, PE).

ECG ischemia: ST elevation in contiguous leads localizes injury (inferior II/III/aVF, anterior V1–V4, lateral I/aVL/V5–V6); reciprocal changes support acute injury.

Life-threatening rhythms: ventricular fibrillation and pulseless VT require immediate defibrillation; asystole and PEA require CPR and epinephrine, not shocks.

ACLS epinephrine 1 mg IV every 3–5 minutes for cardiac arrest; amiodarone 300 mg then 150 mg for refractory VF/VT; adenosine 6 mg rapid push for stable narrow-complex SVT.

Fluid responsiveness: passive leg raise or stroke-volume variation predicts response better than static CVP; CVP alone poorly predicts volume status.

Vasopressors: norepinephrine first-line for septic shock; phenylephrine for tachyarrhythmia-associated hypotension; vasopressin as adjunct in refractory shock.

Glasgow Coma Scale: eye 1–4, verbal 1–5, motor 1–6; total 3–15; score ≤8 generally indicates need for airway protection.

Sedation depth: RASS ranges −5 (unarousable) to +4 (combative); target 0 to −2 for most ventilated patients; SAS and Ramsay scales are alternatives.

Bispectral index (BIS) 40–60 is a common intraoperative target; values are affected by muscle activity, hypothermia, and electrical interference.

Pupillary exam: fixed dilated pupils suggest herniation or severe hypoxia; pinpoint pupils suggest opioid toxicity; unequal pupils suggest mass effect.

Cushing triad (hypertension, bradycardia, irregular respirations) signals raised intracranial pressure and impending herniation.

Delirium screening: CAM-ICU assesses acute onset, inattention, altered consciousness, and disorganized thinking; nonpharmacologic measures first, antipsychotics not routinely recommended.

Seizure management: benzodiazepines first-line for status epilepticus, then second-line antiepileptics (levetiracetam, fosphenytoin, valproate); monitor airway and glucose.

Sedation-related respiratory depression: capnography detects hypoventilation earlier than pulse oximetry, especially with supplemental oxygen masking desaturation.

Opioid reversal: naloxone 0.04–0.4 mg IV titrated to respiration; short half-life (~30–90 min) may require repeat dosing or infusion because opioids outlast it.

Benzodiazepine reversal: flumazenil 0.2 mg IV titrated; risk of seizures in chronic benzodiazepine users and in mixed overdose; avoid routine use.

Neuromuscular blockade reversal: sugammadex 2 mg/kg for moderate block, 4 mg/kg for deep block, 16 mg/kg for immediate reversal; encapsulates rocuronium and vecuronium.

Neostigmine 0.03–0.07 mg/kg with an anticholinergic (glycopyrrolate or atropine) reverses nondepolarizing block; requires train-of-four ≥2 twitches and adequate time.

Succinylcholine: depolarizing blocker; contraindicated in hyperkalemia, burns/trauma >24–48 h, spinal cord injury, malignant hyperthermia susceptibility; metabolized by plasma cholinesterase.

Malignant hyperthermia: dantrolene 2.5 mg/kg IV, repeat to 10 mg/kg; stop triggering agents, hyperventilate with 100% O2, cool, and treat hyperkalemia.

Propofol: rapid onset, short duration, hypotension and respiratory depression; ketamine preserves airway reflexes and blood pressure but can cause emergence reactions.

Local anesthetic systemic toxicity: stop injection, airway support, benzodiazepines for seizures, and 20% lipid emulsion (1.5 mL/kg bolus) for cardiovascular collapse.

ASA physical status: I healthy, II mild systemic disease, III severe systemic disease, IV severe disease with constant threat to life, V moribund, VI brain-dead organ donor; add E for emergency.

Revised Cardiac Risk Index (RCRI): ischemic heart disease, heart failure, cerebrovascular disease, insulin-dependent diabetes, creatinine >2 mg/dL, and high-risk surgery; each adds risk.

STOP-BANG for obstructive sleep apnea: snoring, tiredness, observed apnea, pressure (hypertension), BMI >35, age >50, neck circumference >40 cm, male sex; ≥3 indicates increased risk.

Mallampati classification and airway exam belong to pre-procedure risk assessment; difficult mask ventilation risk factors include age >55, BMI >30, beard, and edentulous status.

Sepsis screening: qSOFA (respiratory rate ≥22, altered mentation, systolic BP ≤100) plus suspected infection flags high risk; SOFA scores organ dysfunction.

Shock index = heart rate / systolic blood pressure; >0.9–1.0 suggests occult hypoperfusion and worse outcome in trauma and hemorrhage.

Preoperative labs and testing should be guided by history and surgery risk; routine testing in healthy patients rarely changes management.

Frailty and functional status (e.g., walking stairs, ADLs) predict perioperative complications better than chronologic age alone.