Anesthesia Board key terms

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in 50% of patients given a standardized surgical stimulus; it is used to compare potency and guide dosing.

The time needed for the plasma concentration of a drug to fall by half after an infusion is stopped; it depends mainly on how long the infusion ran, plus redistribution and elimination.

The pH at which half of the drug molecules are ionized and half are uncharged; it determines how much uncharged drug can cross nerve membranes at tissue pH.

The amplitude of the fourth evoked muscle response divided by the first after four supramaximal nerve stimuli; a ratio of 0.9 or higher indicates adequate recovery from nondepolarizing blockade.

The partial pressure of oxygen at which hemoglobin is 50% saturated, normally about 27 mmHg; a higher value means reduced affinity and easier oxygen release to tissues.

Three vertical lung regions defined by the interplay of alveolar, arterial, and venous pressures; they explain gravity-dependent differences in ventilation and pulmonary blood flow.

The lung volume at which small airways begin to close during exhalation; when it exceeds functional residual capacity, closure occurs during tidal breathing, producing shunt and hypoxemia.

The fraction of each breath that takes no part in gas exchange, consisting of anatomic dead space plus ventilated but unperfused alveoli; it is calculated with the Bohr equation.

Mean arterial pressure minus intracranial pressure, or minus central venous pressure when that is higher; this driving pressure for cerebral blood flow must be protected after head injury.

Aortic diastolic pressure minus left ventricular end-diastolic pressure; it sets coronary blood flow, most of which reaches the left ventricle during diastole.

A formula relating pH to the ratio of bicarbonate to dissolved carbon dioxide (pH = 6.1 + log[HCO3−]/(0.03 × PaCO2)); it is used to interpret acid–base disorders.

The apparent volume that would hold the entire amount of drug in the body at the measured plasma concentration; a large value suggests extensive uptake into tissues.

An induction technique for patients at risk of aspiration that shortens the interval between loss of protective reflexes and tracheal intubation, usually with a fast-acting induction agent, a neuromuscular blocker, and cricoid pressure.

A situation in which a practitioner trained in airway management has trouble with mask ventilation, a supraglottic device, laryngoscopy, intubation, or extubation; management follows a rehearsed algorithm.

A device placed blindly into the pharynx that ventilates through openings sitting above the larynx; it is used for selected elective cases and as a rescue tool in difficult airways.

A small volume of local anesthetic, often with epinephrine, injected through an epidural catheter to detect unintended intravascular or intrathecal placement before the main dose is given.

A four-item score (female sex, nonsmoking status, history of postoperative nausea and vomiting or motion sickness, planned postoperative opioids) that estimates nausea and vomiting risk and guides prophylaxis.

A scoring tool that rates activity, respiration, circulation, consciousness, and oxygen saturation to judge whether a patient is ready for discharge from the postanesthesia care unit.

Maintenance of general anesthesia using only intravenous drugs, typically propofol with an opioid, with no inhaled agent; it suits cases where inhalation is undesirable or malignant hyperthermia is a concern.

An infusion pump run by a pharmacokinetic model that varies delivery to reach and hold a user-set predicted plasma or effect-site concentration of a drug.

A modified gamma-cyclodextrin that encapsulates rocuronium and vecuronium and rapidly reverses even deep aminosteroid blockade; it does not reverse succinylcholine or benzylisoquinolinium relaxants.

A inherited hypermetabolic crisis triggered by volatile anesthetics and succinylcholine, with rising temperature, rigidity, hypercarbia, and acidosis; treatment is stopping triggers and giving dantrolene.

A range of neurologic and cardiovascular effects caused by excess local anesthetic in the bloodstream; management includes airway support, seizure control, and early intravenous lipid emulsion.

Passage of gastric contents into the tracheobronchial tree, causing chemical pneumonitis, obstruction, and infection; risk falls with fasting, aspiration prophylaxis, and rapid sequence induction in high-risk patients.

Ventilation of only one lung to create surgical exposure in thoracic procedures, usually via a double-lumen tube or bronchial blocker, with close attention to hypoxemia and tube position.

An extracorporeal circuit that oxygenates and circulates blood while the heart is stopped, requiring full anticoagulation and careful control of hemodynamics, coagulation, and inflammation.

A technique in which a spinal injection is followed by placement of an epidural catheter, giving fast onset plus a route to extend or supplement analgesia during labor or surgery.

A hypertensive disorder arising after 20 weeks of pregnancy with proteinuria or organ dysfunction; neuraxial analgesia is preferred, and severe disease calls for magnesium and careful blood pressure control.

An ultrasound-guided injection near the saphenous nerve in the distal thigh that relieves knee pain while preserving quadriceps strength better than a femoral nerve block does.

Injection of local anesthetic between the internal oblique and transversus abdominis muscles to block anterior abdominal wall nerves and provide somatic analgesia after abdominal surgery.

A six-level scale (I through VI) summarizing a patient's health and systemic disease burden before anesthesia; it aids communication and risk discussion but does not alone quantify operative risk.

The process of describing a proposed anesthetic's benefits, risks, and alternatives to a patient with decision-making capacity and obtaining voluntary agreement before proceeding.

The type and level of care that a reasonably prudent practitioner with similar training would deliver under similar circumstances; it serves as the benchmark in negligence claims.

A physician order recording a patient's wish to forgo cardiopulmonary resuscitation; before anesthesia it should be reviewed and either reaffirmed, suspended, or limited by explicit agreement.

A structured retrospective review of an adverse event that seeks underlying system failures rather than individual blame and recommends changes to prevent recurrence.

A four-step improvement method in which a change is planned, tried on a small scale, studied for its effects, and then adopted, adapted, or abandoned.

A short structured team confirmation performed before induction, before incision, and before leaving the operating room that verifies patient identity, planned procedure, and key safety steps.

Review of malpractice claims data, such as the ASA Closed Claims Project, to find recurring mechanisms of patient injury and to guide safety improvements.