EHPLE Anesthesia cheat sheet

Oxygen content CaO2 = (1.34 × Hb × SaO2) + (0.003 × PaO2); at Hb 15 g/dL and SaO2 100%, dissolved O2 contributes only ~0.3 mL/dL.

Closing capacity equals residual volume plus closing volume; it rises with age and exceeds functional residual capacity in supine adults around age 45, promoting airway closure and shunt.

Minimum alveolar concentration (MAC) varies inversely with potency; MAC is reduced by hypothermia, pregnancy, opioids, and volatile agents given together (additive ~1 MAC).

Hepatic clearance of drugs depends on intrinsic clearance and hepatic blood flow; for high-extraction drugs (e.g., propofol, lidocaine) clearance is flow-limited.

Local anesthetics are weak bases that block voltage-gated Na+ channels from the intracellular side; inflamed acidic tissue reduces the uncharged fraction and slows onset.

Bupivacaine is more cardiotoxic than lidocaine because it dissociates slowly from cardiac Na+ channels; ropivacaine and levobupivacaine carry lower risk.

Laplace's law P = 2T/r explains why smaller alveoli empty into larger ones without surfactant; surfactant lowers surface tension more at small volumes.

Nerve fiber sensitivity to local anesthetics follows C > A-delta > A-beta > A-alpha; sympathetic and pain fibers are blocked before motor fibers.

Revised Cardiac Risk Index scores 1 point each for ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, creatinine >2 mg/dL, and high-risk surgery; ≥3 points predicts elevated major cardiac events.

Perioperative beta-blockade should not be started on the day of surgery; abrupt withdrawal of chronic beta-blockers increases risk and should be avoided.

Metformin is generally continued through surgery; it is held if contrast dye or significant renal dysfunction is present because of lactic acidosis risk.

An A1c ≥8% or glucose >180 mg/dL predicts higher surgical infection and wound complications; elective surgery is often deferred for optimization.

Smoking cessation at least 4 weeks before surgery reduces pulmonary complications; shorter intervals may transiently increase airway reactivity.

Aspirin for secondary prevention is usually continued for most surgery; dual antiplatelet therapy after coronary stenting requires cardiology input because early discontinuation risks stent thrombosis.

STOP-BANG scores 1 point each for snoring, tiredness, observed apnea, pressure (hypertension), BMI >35, age >50, neck circumference >40 cm, and gender male; ≥3 indicates high OSA risk.

Fasting per ASA: clear liquids 2 hours, breast milk 4 hours, infant formula and nonhuman milk 6 hours, light meal 6 hours, fatty or fried meal 8 hours.

Mallampati class III–IV, thyromental distance <6 cm, mouth opening <3 cm, and limited cervical extension predict difficult laryngoscopy.

The ASA difficult airway algorithm emphasizes oxygen delivery first, limiting attempts, calling for help, and choosing between supraglottic rescue, surgical airway, and waking the patient.

Rapid sequence induction uses a rapidly acting induction agent plus succinylcholine or rocuronium 1.2 mg/kg with cricoid pressure; sugammadex 16 mg/kg can reverse rocuronium.

Suxamethonium is contraindicated in hyperkalemia, burns or denervation beyond 24–48 hours, malignant hyperthermia susceptibility, and known pseudocholinesterase deficiency.

A laryngeal mask airway seals the pharynx and does not protect against aspiration; it is unsuitable for full stomachs or prolonged positive-pressure ventilation at high pressures.

Confirmation of tracheal intubation includes sustained waveform capnography, bilateral breath sounds, chest rise, and absence of gastric sounds; capnography is the standard.

Video laryngoscopy improves glottic view in difficult airways and is recommended as first-line in many predicted-difficult scenarios.

During one-lung ventilation, hypoxemia is managed by increasing PEEP to the dependent lung, CPAP to the non-dependent lung, and checking tube position.

The anesthesia machine has a high-pressure system, intermediate-pressure system, and low-pressure system; the oxygen failure safety device cuts off nitrous oxide if oxygen pressure falls.

The oxygen flush valve delivers 35–75 L/min directly to the breathing circuit, bypassing the vaporizer, and can cause barotrauma if used during inspiration.

Soda lime absorbs CO2 via an exothermic reaction; color change from white to violet indicates exhaustion, but color is unreliable and CO2 monitoring is preferred.

Pulse oximetry relies on differential absorption of red and infrared light; it is unreliable with poor perfusion, motion, methemoglobin, and carboxyhemoglobin.

Capnography waveform shows a normal square shape; a sloping upstroke suggests obstructive ventilation, and an abrupt fall suggests disconnection or embolism.

The oxygen analyzer should read 21% in room air and near 100% with a full oxygen circuit; a low reading indicates a hypoxic mixture.

The scavenging system removes waste anesthetic gases; the AGSS should be checked for obstruction, which can cause circuit pressure and barotrauma.

Electrical safety: the operating room uses isolated power systems with line isolation monitors; microshock risk is highest with intracardiac catheters.

Propofol induction dose is 1.5–2.5 mg/kg IV; it causes hypotension and apnea and has no analgesic effect.

Ketamine 1–2 mg/kg IV provides dissociative anesthesia with analgesia and preserves airway reflexes and respiratory drive.

Spinal anesthesia typically uses hyperbaric bupivacaine 0.75% 1.5–3 mL; the block level depends on baricity, patient position, and dose.

Epidural test dose is 3 mL of lidocaine 1.5% with epinephrine 1:200,000; a heart rate rise >20 bpm suggests intravascular injection.

Interscalene brachial plexus block reliably anesthetizes the shoulder but spares the ulnar nerve and causes ipsilateral phrenic nerve palsy in most patients.

Supraclavicular block risks pneumothorax and phrenic nerve palsy; axillary block risks local anesthetic systemic toxicity from axillary artery injection.

Total intravenous anesthesia with propofol and remifentanil provides rapid recovery; remifentanil is metabolized by nonspecific esterases and has context-insensitive kinetics.

Neuraxial anesthesia in a patient on therapeutic anticoagulation requires adherence to ASRA interval guidelines; spinal hematoma risk depends on drug and timing.

Malignant hyperthermia presents with rising end-tidal CO2, tachycardia, masseter spasm, and hyperthermia; treat with dantrolene 2.5 mg/kg IV and stop triggering agents.

Anaphylaxis under anesthesia presents as hypotension, bronchospasm, and rash; epinephrine 10–100 mcg IV boluses is first-line, with fluid resuscitation.

Local anesthetic systemic toxicity presents with perioral numbness, tinnitus, seizures, and cardiac arrest; treat with 20% lipid emulsion 1.5 mL/kg bolus.

A sudden drop in end-tidal CO2 with hypotension suggests pulmonary embolism, venous air embolism, or circuit disconnection; assess and act immediately.

Hypotension after spinal anesthesia is due to sympathetic blockade; treat with left uterine displacement, fluids, and phenylephrine or ephedrine.

Massive transfusion protocol uses balanced ratios of red cells, plasma, and platelets; monitor ionized calcium and treat hypocalcemia from citrate.

Awareness under anesthesia is suggested by patient recall, tachycardia, and hypertension; use processed EEG monitoring in high-risk cases.

Perioperative aspiration presents with hypoxemia, bronchospasm, and infiltrates; suction, oxygen, and supportive care are initial steps.

Postoperative nausea and vomiting risk factors include female sex, nonsmoking, history of PONV, and opioid use; multimodal prophylaxis uses ondansetron, dexamethasone, and droperidol.

Multimodal analgesia combines acetaminophen, NSAIDs, local anesthetics, and opioids to reduce opioid requirements and side effects.

Opioid-induced respiratory depression presents with decreasing respiratory rate and sedation; naloxone 0.04–0.4 mg IV titrated is the antidote.

Postoperative hypoxemia is common after general anesthesia; supplemental oxygen and monitoring in the PACU are standard until stable.

Enhanced recovery after surgery protocols emphasize early mobilization, early oral intake, opioid-sparing analgesia, and regional techniques.

Patient-controlled analgesia with opioids requires monitoring for sedation and respiratory depression; a background infusion increases risk.

Chronic postsurgical pain is defined as pain persisting beyond 3 months after surgery; risk factors include severe acute pain and nerve injury.

Postoperative delirium is common in older adults; screen with the Confusion Assessment Method and address pain, hypoxia, and medications.

Obstructive sleep apnea patients have increased sensitivity to opioids and anesthetics; use CPAP, regional techniques where possible, and extended monitoring.

Neonates have higher water content and lower protein binding; drug doses are weight-based and require careful titration.

Pregnancy increases minute ventilation and reduces functional residual capacity, leading to rapid desaturation during apnea.

Elderly patients have reduced MAC requirements and decreased clearance of many drugs; start with lower doses and titrate.

Patients with severe aortic stenosis are preload-dependent and prone to hypotension; maintain sinus rhythm, preload, and afterload.

Chronic kidney disease alters drug clearance; avoid succinylcholine in hyperkalemia and adjust doses of renally cleared drugs.

Cirrhosis causes coagulopathy, hypoalbuminemia, and altered drug metabolism; use lower doses and monitor for encephalopathy.

Diabetic patients require glucose monitoring intraoperatively; aim for 140–180 mg/dL and avoid hypoglycemia.

Informed consent requires capacity, disclosure of risks and alternatives, and voluntary agreement; it is a process, not a signature alone.

The anesthesia record is a legal document; document events contemporaneously and avoid retrospective alterations.

Patient safety culture emphasizes reporting near misses and errors without blame; root cause analysis identifies system failures.

The WHO surgical safety checklist includes sign-in, time-out, and sign-out phases; it reduces surgical morbidity and mortality.

Confidentiality is protected by law; disclose patient information only with consent or as required by law.

When a patient lacks capacity, treatment decisions follow advance directives or surrogate decision-makers, with best-interest standards.

Conflict of interest must be disclosed; financial relationships can influence clinical decisions and must be managed transparently.

Handover of care should use structured communication such as SBAR to reduce omissions and adverse events.