CRNA (NCE) cheat sheet

MAC at 1 atm in adults: nitrous oxide ~105%, desflurane ~6.0%, sevoflurane ~2.0%, isoflurane ~1.15%, halothane ~0.75%.

Arterial oxygen content: CaO2 = (1.34 x Hb x SaO2) + (0.0031 x PaO2), reported in mL O2 per dL blood.

Clearance = 0.693 x volume of distribution / elimination half-life; volume of distribution = dose / plasma concentration.

Potency tracks lipid solubility (Meyer-Overton rule): the higher the lipid solubility, the lower the MAC and the greater the potency.

Phase I depolarizing block: reduced twitch height with no fade and no post-tetanic facilitation; nondepolarizing block: fade and post-tetanic potentiation.

Resting membrane potential is about -70 mV and is set mainly by potassium permeability; hypokalemia hyperpolarizes and hyperkalemia depolarizes the cell.

Laplace law P = 2T/r predicts small alveoli empty into large ones; surfactant lowers surface tension, raises compliance, and stabilizes alveolar volume.

GFR = filtration coefficient x net filtration pressure; renal blood flow is autoregulated between mean arterial pressures of roughly 80 and 180 mmHg.

E cylinder holds about 660 L of oxygen at 1900 psi; remaining liters can be estimated as gauge pressure in psi x 0.28.

Pipeline supply is about 50 psi for oxygen, medical air, and nitrous oxide; cylinder regulators deliver roughly 45 psi to the machine.

Pin Index Safety System prevents cylinder-to-yoke misconnection; the Diameter Index Safety System prevents hose misconnection; oxygen pins are 2 and 5.

Oxygen failure safety device senses low supply pressure, shuts off nitrous oxide, alarms, and allows the oxygen flush to deliver 100% oxygen.

Vaporizer output depends on fresh gas flow, carrier gas composition, and temperature; desflurane needs a heated (~39 C), pressurized (~2 atm) vaporizer.

Soda lime absorbs roughly 26 L of CO2 per 100 g; exhaustion raises inspired CO2 and changes indicator color; desiccated absorbent generates carbon monoxide.

Normal capnogram: phase I dead space, phase II ascending, phase III alveolar plateau; end-tidal CO2 35-45 mmHg; sudden fall to zero suggests disconnection or esophageal intubation.

Circle system contains two unidirectional valves, a CO2 absorber, reservoir bag, and adjustable pressure-limiting valve; fresh gas flow below 1 L/min is considered low flow.

Pulse oximetry compares 660 nm and 940 nm absorption and becomes unreliable with methemoglobin, carboxyhemoglobin, poor perfusion, motion, and nail polish.

1 MAC is the ED50 for immobility; about 1.3 MAC prevents movement in 95% of patients, and MAC-awake is roughly 0.3-0.4 MAC.

MAC values are additive: 0.6 MAC of a volatile plus 0.6 MAC of nitrous oxide approximates 1.2 MAC total.

Induction doses: propofol 1.5-2.5 mg/kg, etomidate 0.2-0.3 mg/kg, ketamine 1-2 mg/kg, thiopental 3-5 mg/kg.

Rapid sequence induction: 3-5 minutes preoxygenation, rapid induction agent, succinylcholine 1-1.5 mg/kg, cricoid pressure, then intubation.

Reversal thresholds: train-of-four ratio 0.9 or greater confirms recovery; neostigmine 0.04-0.07 mg/kg with glycopyrrolate, or sugammadex 2 mg/kg at TOF count 2 and 4 mg/kg at post-tetanic count 1-2.

Succinylcholine is contraindicated with hyperkalemia, burns or denervation older than 24-48 hours, spinal cord injury, myopathy, and malignant hyperthermia susceptibility.

Malignant hyperthermia: stop triggers, 100% oxygen at high flow, dantrolene 2.5 mg/kg repeated to 10 mg/kg, active cooling, and treatment of hyperkalemia and acidosis.

Laryngospasm: 100% oxygen with continuous positive airway pressure and deepen anesthesia; if it persists, succinylcholine 0.5-1 mg/kg IV or 4 mg/kg IM.

Key dermatomes: nipple T4, xiphoid T7, umbilicus T10, inguinal ligament L1, perineum S2-S4.

Maximum local anesthetic doses: lidocaine 4.5 mg/kg (7 mg/kg with epinephrine), bupivacaine 2-2.5 mg/kg, ropivacaine 3 mg/kg, mepivacaine 7 mg/kg.

Local anesthetic systemic toxicity: stop injection, 100% oxygen, benzodiazepine for seizures, 20% lipid emulsion 1.5 mL/kg bolus then 0.25 mL/kg/min infusion.

Spinal solutions: hyperbaric bupivacaine 0.75% in dextrose settles with gravity so patient position determines block height; isobaric solutions spread less predictably.

Postural puncture headache: conservative therapy first, then epidural blood patch with 15-20 mL autologous blood.

Neuraxial anticoagulation: hold prophylactic low-molecular-weight heparin 12 hours and therapeutic dosing 24 hours; clopidogrel 5-7 days; aspirin alone requires no delay.

Interscalene block commonly causes ipsilateral phrenic paresis and Horner syndrome; supraclavicular has the highest pneumothorax risk; axillary may spare the radial nerve.

Transversus abdominis plane block covers T6-L1; adductor canal block preserves quadriceps strength, whereas femoral block causes weakness and fall risk.

Pediatric tracheal tube internal diameter: uncuffed = (age in years / 4) + 4; cuffed = (age in years / 4) + 3.5.

Pediatric fasting intervals: clear liquids 2 hours, breast milk 4 hours, formula and solids 6 hours.

After 20 weeks gestation, displace the uterus leftward to relieve aortocaval compression; treat spinal-induced hypotension with phenylephrine boluses.

Geriatric physiology: MAC declines about 6% per decade after age 40, and closing capacity exceeds functional residual capacity, promoting atelectasis and desaturation.

Neurosurgery: target PaCO2 30-35 mmHg for acute intracranial hypertension, cerebral perfusion pressure (MAP - ICP) 60-70 mmHg, and mannitol 0.25-1 g/kg.

One-lung ventilation: tidal volume 4-6 mL/kg predicted body weight, PEEP about 5 cmH2O, plateau pressure under 30 cmH2O; hypoxemia is treated with CPAP to the non-dependent lung and PEEP to the dependent lung.

Chronic kidney disease: avoid succinylcholine if potassium exceeds 5.5 mEq/L; cisatracurium and remifentanil are organ-independent; meperidine accumulates normeperidine.

Bariatric and obstructive sleep apnea patients: ramped position, careful preoxygenation, opioid-sparing multimodal analgesia, and early extubation when criteria are met.

ASA physical status: I healthy, II mild systemic disease, III severe but not incapacitating, IV incapacitating constant threat to life, V moribund, VI brain-dead organ donor; suffix E denotes emergency.

Negligence requires four elements: a duty owed to the patient, breach of that duty, injury, and causation linking breach to injury.

Closed-claims data show respiratory events and nerve injury as leading damaging events, with death and severe brain injury dominating indemnity payments.

Universal protocol: preprocedure verification, site marking, and a time-out immediately before incision with the whole team.

Fire triad is oxidizer (oxygen or nitrous oxide), fuel (drapes, tracheal tube), and ignition source (electrocautery, laser); airway fire is managed by stopping gases, removing the tube, and flooding with saline.

Needlestick transmission risk: HIV about 0.3%, hepatitis B up to 30% in unvaccinated hosts, hepatitis C about 1.8%; postexposure prophylaxis should start within 2 hours.

NIOSH exposure limits: nitrous oxide 25 ppm time-weighted average and halogenated agents 2 ppm (0.5 ppm when nitrous oxide is also present).

Structured handoff uses SBAR (Situation, Background, Assessment, Recommendation) and must include airway findings, allergies, lines, blood loss, drugs given, and plan.