RAA cheat sheet

MAC is the alveolar concentration at 1 atm that abolishes movement in 50% of subjects to a standard surgical stimulus; MAC-awake is roughly one-third of MAC and MAC-BAR (blunting autonomic response) is roughly 1.5 times MAC.

Oxygen content of blood: CaO2 = (1.34 × Hb × SaO2) + (0.003 × PaO2); the dissolved component is negligible at atmospheric pressure, so anemia lowers CaO2 even with normal saturation.

Dalton's law: total pressure equals the sum of partial pressures; at sea level dry gas PO2 = 0.21 × 760 ≈ 160 mmHg, and humidification and altitude both lower the effective inspired PO2.

Poiseuille's law: flow through a tube varies with the fourth power of radius and inversely with length and viscosity, so a 16-fold resistance rise follows a 50% reduction in airway radius.

Turbulent flow resistance depends on gas density (heliox reduces it) while laminar resistance depends on viscosity; Reynolds number predicts the transition.

The oxyhemoglobin dissociation curve shifts right (reduced affinity) with increased temperature, PCO2, 2,3-DPG, and acidosis; fetal hemoglobin and carboxyhemoglobin shift it left.

Propofol and etomidate act primarily on GABA-A receptors; ketamine antagonizes NMDA receptors; opioids act on mu receptors producing analgesia, respiratory depression, and bradycardia.

First-order elimination means a constant fraction is removed per unit time; a drug with a 4-hour half-life is ~94% eliminated after four half-lives (16 hours).

ASA physical status: I healthy; II mild systemic disease; III severe systemic disease; IV constant threat to life; V moribund not expected to survive without operation; add E for emergency.

Mallampati classes III and IV, thyromental distance under 6 cm, interincisor opening under 3 cm, and limited neck extension each raise the risk of difficult direct laryngoscopy.

Revised Cardiac Risk Index predictors: ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, creatinine above 2 mg/dL, and high-risk surgery; each scores one point.

Metformin is generally continued perioperatively, but SGLT2 inhibitors are typically held 3-4 days before surgery because of euglycemic ketoacidosis risk.

Patients on ACE inhibitors or ARBs are commonly held on the morning of major surgery to reduce intraoperative hypotension; beta-blockers are usually continued.

A fasting duration of 2 hours for clear liquids, 4 hours for breast milk, and 6 hours for light solids applies to elective anesthesia in healthy patients.

Anticoagulation planning: neuraxial block generally requires stopping prophylactic low-molecular-weight heparin 12 hours and therapeutic dosing 24 hours beforehand.

Informed consent must document discussion of risks, benefits, alternatives, and the possibility of blood transfusion or postoperative ventilation when relevant.

The oxygen failure safety device cuts off nitrous oxide and other hypoxic gases when oxygen supply pressure falls, and alarms sound below roughly 30 psig pipeline or 1000 psig cylinder pressure.

The pin index safety system prevents cylinder misconnection; the diameter index safety system prevents wall-outlet misconnection; the DISS and PISS do not prevent crossover of hoses at the machine.

The oxygen flush valve delivers 35-75 L/min of 100% oxygen directly to the breathing circuit, bypassing the vaporizer and flowmeters.

Soda lime absorbs CO2 via an exothermic reaction; exhaustion is suggested by fading indicator color, increasing inspired CO2, and heat loss from the canister.

Pulse oximetry relies on differential absorption of red and infrared light; it is unreliable with poor perfusion, motion, methemoglobinemia, and carboxyhemoglobin, which reads falsely high.

Capnography waveform phases: phase I dead space, phase II ascending, phase III alveolar plateau; an abrupt drop to zero suggests disconnection or esophageal intubation.

The anesthesia machine low-pressure leak test checks the circuit from the flowmeters to the common gas outlet at 40 cmH2O with the vaporizers off.

Electrical safety: current above 100 mA across the heart can cause ventricular fibrillation; line isolation monitors and ground-fault protection reduce macroshock risk.

Difficult mask ventilation predictors include age over 55, body mass index above 30, edentulousness, beard, and snoring; each is a component of the MOANS mnemonic.

The Mallampati examination is performed with the patient seated, mouth wide open, tongue protruded, and no phonation; classes III and IV expose only the soft palate or hard palate.

Laryngeal mask airway cuff volumes are typically 20-30 mL for size 3-5; excessive inflation raises oropharyngeal leak pressure and causes sore throat.

Confirmation of tracheal intubation: continuous waveform capnography is the standard, supplemented by bilateral breath sounds and chest rise; an esophageal detector device is adjunctive only.

Rapid sequence induction uses a rapidly acting induction agent plus succinylcholine 1-1.5 mg/kg with cricoid pressure and no interposed ventilation in patients at aspiration risk.

A cannot-intubate, cannot-oxygenate emergency calls for supraglottic rescue, then surgical airway (cricothyrotomy) as the final step.

During one-lung ventilation, hypoxemia is managed by confirming tube position, applying CPAP to the non-dependent lung, PEEP to the dependent lung, and accepting permissive hypercapnia.

Neuromuscular block is monitored at the adductor pollicis or orbicularis oculi; a train-of-four ratio above 0.9 indicates adequate recovery for extubation.

Propofol induction dose is 1.5-2.5 mg/kg IV; it causes hypotension from vasodilation and myocardial depression, and pain on injection is reduced by lidocaine or a large vein.

Etomidate 0.2-0.3 mg/kg provides hemodynamic stability but transiently suppresses adrenal cortisol synthesis via 11-beta-hydroxylase inhibition.

Ketamine 1-2 mg/kg IV produces dissociative anesthesia with analgesia and sympathetic stimulation; it is relatively contraindicated in uncontrolled hypertension and raised intracranial pressure.

Succinylcholine 1-1.5 mg/kg has an onset of 45-60 seconds and duration of 5-10 minutes; it is avoided in hyperkalemia, burns older than 24-48 hours, and malignant hyperthermia susceptibility.

Rocuronium 0.6-1.2 mg/kg provides intubating conditions in 60-90 seconds; sugammadex 2-4 mg/kg reverses moderate block and 16 mg/kg reverses deep block.

Sevoflurane is nonpungent and suitable for inhalational induction; desflurane causes airway irritation and should be avoided for mask induction.

Local anesthetic maximum doses: lidocaine 4.5 mg/kg plain or 7 mg/kg with epinephrine; bupivacaine 2.5-3 mg/kg; bupivacaine is more cardiotoxic than lidocaine.

Neuraxial block: spinal anesthesia typically uses 0.5% bupivacaine 10-15 mg; hypotension results from sympathetic blockade and is treated with fluids and vasopressors.

Mean arterial pressure = (systolic + 2 × diastolic) / 3; a MAP of 65 mmHg is the usual lower autoregulation threshold for vital organs.

Cardiac output = heart rate × stroke volume; stroke volume depends on preload, afterload, and contractility, which are the targets of hemodynamic therapy.

Hypotension from anesthesia is usually vasodilation plus myocardial depression; treatment is fluid plus a vasopressor such as phenylephrine 40-100 mcg or ephedrine 5-10 mg.

Norepinephrine is the first-line vasopressor for septic shock; it raises mean arterial pressure with modest effect on heart rate compared with dopamine.

Goal-directed fluid therapy uses dynamic measures such as pulse pressure variation above 13% or stroke volume variation to predict fluid responsiveness in ventilated patients.

The normal urine output target is 0.5 mL/kg/h in adults; oliguria warrants assessment of volume status, perfusion, and obstruction.

Malignant hyperthermia is treated with dantrolene 2.5 mg/kg IV repeated as needed, active cooling, hyperventilation with 100% oxygen, and stopping the triggering agent.

Tranexamic acid reduces bleeding in trauma and major surgery; dosing is typically 1 g IV over 10 minutes, and it is contraindicated in active intravascular thrombosis.

Anaphylaxis under anesthesia: stop the trigger, give epinephrine 10-100 mcg IV boluses (or 0.5 mg IM), fluids, 100% oxygen, and consider a vasopressin infusion for refractory shock.

Malignant hyperthermia presents with rising end-tidal CO2, masseter or generalized rigidity, tachycardia, and hyperthermia; dantrolene 2.5 mg/kg is the specific treatment.

Local anesthetic systemic toxicity: stop injection, secure the airway, give 20% lipid emulsion 1.5 mL/kg bolus followed by 0.25 mL/kg/min infusion, and avoid vasopressin and calcium channel blockers.

Last-resort treatment for severe bronchospasm includes epinephrine 10-50 mcg IV, deepening anesthesia, and nebulized beta-agonists; consider tension pneumothorax in sudden deterioration.

Awareness under anesthesia is suggested by patient report and confirmed with the isolated forearm technique or end-tidal agent monitoring; BIS monitoring may reduce risk.

Postoperative nausea and vomiting is multifactorial; a multimodal approach combines dexamethasone 4-8 mg, ondansetron 4 mg, and droperidol or scopolamine.

Negative-pressure pulmonary edema after laryngospasm is treated with positive-pressure ventilation, diuretics, and oxygen; reintubation may be needed.

Cardiac arrest in the operating room follows ACLS: compressions at 100-120/min, epinephrine 1 mg every 3-5 minutes, and defibrillation for shockable rhythms.

The Aldrete score assesses discharge readiness using activity, respiration, circulation, consciousness, and oxygen saturation; a score of 9-10 is typically required.

A postanesthesia care unit stay requires continuous monitoring of oxygen saturation, respiratory rate, and blood pressure; pulse oximetry detects hypoxemia before clinical signs.

Postoperative shivering raises oxygen consumption and is treated with forced-air warming and meperidine 12.5-25 mg IV.

Multimodal analgesia combines acetaminophen, NSAIDs, opioids, and regional techniques; the goal is to reduce opioid consumption and related adverse effects.

Opioid-induced respiratory depression is treated with naloxone 40-100 mcg IV titrated, with airway support and monitoring for renarcotization.

Acute pain service protocols use patient-controlled analgesia with demand doses and lockouts; background infusions increase respiratory depression risk.

Epidural analgesia requires monitoring for hypotension, motor block, and catheter-related infection; high block can cause bradycardia and respiratory compromise.

Discharge criteria after ambulatory anesthesia include stable vital signs, no nausea or vomiting, controlled pain, and ability to ambulate and void when required.