ABA BASIC key terms

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in response to a standardized surgical stimulus in 50% of patients. It indexes potency and falls with age, hypothermia, pregnancy, and sedative coadministration.

The time needed for the plasma concentration of a drug to fall by half after a continuous infusion is stopped. It lengthens as infusion duration increases for lipophilic drugs that accumulate in peripheral compartments.

The apparent volume relating the amount of drug in the body to its plasma concentration. A large value implies extensive tissue uptake and supports a larger loading dose, but it does not by itself predict elimination rate.

The volume of plasma completely cleared of drug per unit time. Along with volume of distribution it sets elimination half-life, since half-life equals 0.693 times volume of distribution divided by clearance.

Potency is the dose required to produce a given effect and is shown by the curve's position on the dose axis; efficacy is the greatest effect a drug can produce. Potency does not imply high efficacy.

Elimination in which a constant fraction of the drug present is removed per unit time, producing an exponential decline in concentration. Most anesthetic drugs follow this pattern at usual clinical doses.

Inherited or acquired deficiency of plasma butyrylcholinesterase that prolongs paralysis from succinylcholine or mivacurium. Management is continued ventilation and sedation until recovery; cholinesterase inhibitors do not help and may worsen the block.

The amplitude of the fourth evoked twitch divided by the first during four supramaximal stimuli at 2 Hz. A ratio of at least 0.9 at the adductor pollicis indicates adequate recovery from nondepolarizing blockade.

Depolarizing agents such as succinylcholine open the nicotinic receptor channel persistently, causing fasciculations then flaccid paralysis. Nondepolarizing agents compete with acetylcholine at the receptor without activating it, and are reversed by cholinesterase inhibitors or sugammadex.

A modified gamma-cyclodextrin that encapsulates rocuronium and vecuronium, rapidly reversing even deep nondepolarizing blockade. It does not reverse succinylcholine or benzylisoquinolinium agents; adverse effects include anaphylaxis, bradycardia, and coagulation concerns.

The principle that increasing ventricular filling volume increases stroke volume up to a physiologic plateau, because stretched sarcomeres generate more force. It explains why fluid boluses raise output in preload-dependent patients.

A sigmoid curve relating arterial oxygen tension to hemoglobin saturation. Acidosis, hypercapnia, hyperthermia, and high 2,3-DPG shift it right, lowering affinity so oxygen unloads more readily in tissues.

The product of cardiac output and arterial oxygen content, roughly 1000 mL/min in a healthy adult. Content depends mostly on hemoglobin concentration and saturation, since dissolved oxygen contributes little.

The portion of cardiac output that passes through the lungs without contacting ventilated alveoli. Because shunted blood is already desaturated, supplemental oxygen corrects it poorly compared with low ventilation-perfusion regions.

The portion of each tidal breath that does not take part in gas exchange, combining anatomic and alveolar dead space. It rises with pulmonary embolism, hypotension, and high airway pressures, and is estimated by the Bohr equation.

A continuous waveform of carbon dioxide concentration in respired gas. The end-tidal value approximates alveolar tension, and the trace's shape reveals esophageal intubation, bronchospasm, circuit disconnection, or exhausted absorbent.

A pharmacogenetic condition in which volatile anesthetics or succinylcholine trigger excessive skeletal muscle calcium release, causing rigidity, hypercarbia, acidosis, and hyperthermia. Dantrolene, cooling, and supportive care are the treatment.

A noninvasive estimate of arterial hemoglobin saturation derived from the differing absorption of red and infrared light by pulsatile tissue. It cannot reliably distinguish carboxyhemoglobin or methemoglobin from oxyhemoglobin and fails with poor perfusion.

A six-level scale (I to VI) describing a patient's preexisting health before anesthesia, from healthy to declared brain-dead organ donor. It broadly correlates with perioperative risk but does not account for surgical complexity.

A bedside score from I to IV describing which oropharyngeal structures are visible when the patient sits upright, opens the mouth, and protrudes the tongue. Higher scores suggest a higher chance of difficult direct laryngoscopy.

A four-grade classification of the glottic view during direct laryngoscopy, from grade I with the vocal cords fully visible to grade IV with no glottic structure seen.

The ASA decision pathway for difficult ventilation, difficult laryngoscopy, failed intubation, or failed rescue. It stresses limiting attempts, calling for help, maintaining oxygenation, and choosing among supraglottic devices and surgical airway.

A technique for patients at risk of aspiration, combining preoxygenation, a fast-acting induction agent, and succinylcholine or rocuronium, with immediate intubation and minimal interposed positive-pressure ventilation.

General anesthesia maintained solely with intravenous drugs, usually propofol plus an opioid, often by target-controlled infusion. It avoids volatile agents and postoperative nausea but carries awareness risk and depends on secure intravenous access.

Explicit recall of events during intended general anesthesia. Risk is higher with light anesthesia, neuromuscular paralysis without depth monitoring, obstetric and cardiac surgery, and total intravenous anesthesia.

The difference between aortic diastolic pressure and left ventricular end-diastolic pressure. Because coronary flow occurs mainly in diastole, this gradient is critical in coronary disease and aortic stenosis.

Constriction of small pulmonary arteries in response to low alveolar oxygen, diverting blood toward better-ventilated lung. It improves gas exchange but can strain the right ventricle and is blunted by vasodilators and volatile anesthetics.

Ventilation of a single lung, usually through a double-lumen tube or bronchial blocker, to collapse and isolate the operative lung. It demands fiberoptic confirmation of position and active management of hypoxemia and airway pressures.

Intravenous magnesium sulfate prevents and treats eclamptic seizures, given as a loading dose then infusion. Toxicity causes loss of deep tendon reflexes, respiratory depression, and arrest; calcium gluconate is the antidote.

Anesthesia from local anesthetic injected into the spinal or epidural space to block nerve roots. Sympathectomy causes hypotension and bradycardia; coagulopathy, local infection, and severe hypovolemia are contraindications.

A headache that is worse upright and relieved by lying flat, caused by cerebrospinal fluid leaking through a dural puncture. It follows spinal or epidural procedures and is treated conservatively, with caffeine, or by epidural blood patch.

A required pre-procedure pause in which the team confirms patient identity, procedure, site, consent, allergies, and readiness. It is intended to prevent wrong-patient, wrong-site, and wrong-procedure events.

An unexpected occurrence involving death, serious physical or psychological harm, or the risk of either. Such events prompt immediate investigation and root cause analysis rather than individual blame.

A structured team investigation that asks why an adverse event happened by tracing active and latent system failures, then proposes changes. Its focus is system redesign, not punishment of individuals.

James Reason's model in which harm occurs only when holes in several layers of defense line up. Latent conditions and active errors both contribute, so safety depends on strengthening multiple barriers.

A review of malpractice claims against anesthesiologists that identifies recurring injury patterns and mechanisms. Its findings have driven safety changes such as mandatory pulse oximetry and capnography.