Arab Board Anesthesia Part 1 key terms

The volume of gas remaining in the lungs at the end of a normal passive expiration, equal to expiratory reserve volume plus residual volume. It is the main oxygen reservoir during apnea and falls markedly under general anesthesia and in obesity.

The lung volume at which small airways begin to close during expiration. When closing capacity exceeds functional residual capacity, airway closure occurs during tidal breathing, causing shunt and hypoxemia, especially in the elderly, obese, and supine patients.

Inequality between the amount of air reaching the alveoli and the blood flow perfusing them. Extreme forms are shunt, where perfused alveoli are unventilated, and dead space, where ventilated alveoli are unperfused; both impair gas exchange.

The portion of each breath that does not participate in gas exchange, comprising anatomic dead space of the conducting airways plus alveolar dead space from unperfused alveoli. It is normally about one third of tidal volume and increases with hypotension and lung disease.

Continued oxygen uptake from the alveoli into the blood during apnea, which draws gas down the airways and can maintain oxygenation for several minutes. It depends on a patent airway and a high alveolar oxygen fraction, and does not remove carbon dioxide.

Administration of a high inspired oxygen concentration before induction of anesthesia or tracheal intubation to replace nitrogen in the functional residual capacity. This creates an oxygen reservoir that prolongs the safe apnea time before desaturation occurs.

The total amount of oxygen transported to the tissues per minute, calculated as cardiac output multiplied by arterial oxygen content. It depends on hemoglobin concentration, arterial saturation, and blood flow, and is a key target in critical illness.

The sum of oxygen bound to hemoglobin and oxygen dissolved in plasma per unit volume of arterial blood. Hemoglobin-bound oxygen predominates, so anemia reduces content far more than a fall in dissolved oxygen does.

The sigmoid relationship between oxygen partial pressure and hemoglobin saturation. It shifts right, releasing oxygen more readily, with raised carbon dioxide, hydrogen ions, temperature, and 2,3-diphosphoglycerate, and shifts left with fetal hemoglobin and stored blood.

The oxygen saturation of blood in the pulmonary artery, reflecting the balance between whole-body oxygen delivery and consumption. A low value suggests inadequate delivery or increased demand, while a high value may indicate sepsis-related extraction failure or shunt.

The proportion of cardiac output that passes through the lungs without taking part in gas exchange, mixing deoxygenated blood with arterial blood. It causes hypoxemia that responds poorly to supplemental oxygen and is measured with pulmonary artery catheters.

The change in volume produced by a given change in pressure, describing the distensibility of the lungs or chest wall. Reduced compliance increases the pressure needed for ventilation and is seen in pulmonary edema, fibrosis, and abdominal distension.

The pressure gradient needed to produce a given gas flow through the airways. It rises with bronchoconstriction, secretions, and small endotracheal tube caliber, increasing the work of breathing and the peak pressure needed during positive-pressure ventilation.

The plateau airway pressure minus positive end-expiratory pressure during controlled ventilation. It reflects the cyclic stretch applied to lung tissue, and higher values are associated with ventilator-induced lung injury and worse outcomes in acute respiratory distress syndrome.

Maintenance of positive airway pressure at the end of expiration during mechanical ventilation. It recruits collapsed alveoli, improves oxygenation, and reduces atelectasis, but can reduce venous return and cause barotrauma at excessive levels.

A transient increase in airway pressure designed to reopen collapsed alveoli in ventilated lungs. It is often followed by appropriate positive end-expiratory pressure to keep the alveoli open, and may cause hypotension or barotrauma.

The apparent volume in which a drug dose would need to be distributed to achieve the observed plasma concentration. It determines the loading dose and is influenced by body size, protein binding, and lipid solubility.

The volume of plasma from which a drug is completely removed per unit time. It determines the maintenance dose rate needed to sustain a steady-state concentration and depends on hepatic metabolism and renal excretion.

The time required for plasma concentration to fall by half after stopping a continuous infusion, measured from the moment of cessation. It lengthens with longer infusion duration for lipid-soluble drugs that accumulate in peripheral tissues, such as thiopental.

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in response to a standardized surgical stimulus in half of subjects. It allows comparison of potency and is reduced by opioids, hypothermia, pregnancy, and age.

A measure of the solubility of an inhaled anesthetic in lipid relative to gas, which correlates inversely with potency. Higher values indicate greater lipid solubility and lower minimum alveolar concentration, as described by the Meyer-Overton relationship.

The ratio of anesthetic concentration in blood to that in gas at equilibrium, reflecting blood solubility. Low solubility produces faster alveolar and brain equilibration and therefore quicker induction and emergence, as with desflurane and sevoflurane.

The phenomenon in which rapid uptake of a high-concentration gas such as nitrous oxide increases the alveolar concentration of a concurrently administered volatile agent, speeding its uptake. It results from concentration and volume effects in the alveolus.

Inhibition of voltage-gated sodium channels in nerve membranes, preventing depolarization and propagation of action potentials. This is the shared mechanism of local anesthetics and of class I antiarrhythmic drugs, and is enhanced in alkaline pH.

The pH at which half of the drug molecules are ionized and half are un-ionized. The closer the tissue pH is to the pKa, the greater the fraction of lipid-soluble un-ionized base available to cross the nerve membrane, influencing onset speed.

The progressive loss of autonomic, pain, and temperature sensation before touch and motor function during local anesthetic blockade. It reflects differing sensitivity of nerve fiber types and is exploited clinically to preserve motor power while providing analgesia.

A dose-related syndrome of central nervous system excitation followed by depression, and cardiac conduction slowing, arrhythmia, and cardiovascular collapse, caused by unintentional intravascular injection or overdose of local anesthetic. Treatment includes airway support and intravenous lipid emulsion.

Administration of a lipid emulsion as an antidote for severe local anesthetic systemic toxicity. It is believed to create an intravascular lipid compartment that sequesters the drug and supports cardiac energetics, and is given alongside standard resuscitation.

The airway pressure below which blood flow through a collapsible vessel ceases because the surrounding pressure exceeds the intravascular pressure. It explains how raised intrathoracic or intracranial pressure can abolish perfusion despite adequate arterial pressure.

The difference between mean arterial pressure and intracranial pressure, representing the driving force for cerebral blood flow. It is targeted in neurocritical care and is affected by head positioning, carbon dioxide tension, and anesthetic agents.

The intrinsic ability of cerebral resistance vessels to maintain relatively constant blood flow across a range of arterial pressures, roughly between 50 and 150 millimeters of mercury in healthy adults. It is impaired by trauma, ischemia, and some anesthetics.

The cyclic change in arterial pulse pressure during positive-pressure ventilation, expressed as a percentage of the mean. A high value suggests volume responsiveness in a patient on controlled ventilation, but it is unreliable with arrhythmia or spontaneous breathing.

The respiratory variation in beat-to-beat stroke volume during mechanical ventilation, used as a dynamic predictor of fluid responsiveness. Like pulse pressure variation, it requires controlled ventilation, sinus rhythm, and adequate tidal volumes to be reliable.

The continuous display of carbon dioxide concentration against time during the respiratory cycle. Its shape and amplitude confirm tracheal tube placement, detect esophageal intubation, disconnection, obstruction, and low cardiac output, and guide ventilation.

The partial pressure of carbon dioxide measured at the end of expiration, approximating alveolar and arterial values in healthy lungs. It falls with hyperventilation, low cardiac output, and embolism, and rises with hypoventilation and increased metabolism.

A structured method for reviewing adverse events by collecting detailed accounts of the incident from involved staff. It identifies contributing system factors rather than individual blame and informs quality improvement and safety training.

A systematic retrospective investigation that traces an adverse event back to underlying system failures rather than stopping at the actions of front-line staff. Its findings should generate changes in protocols, equipment, and training to prevent recurrence.

The study of how human capabilities, limitations, and behaviors interact with equipment, tasks, and teams in the workplace. In anesthesia it underpins design of alarms, checklists, and training to reduce error and improve performance under stress.

The continuous perception of relevant elements in the environment, comprehension of their meaning, and projection of future states. Loss of situation awareness is a common precursor to anesthesia crises and is supported by checklists and closed-loop communication.

A set of non-technical skills for managing emergencies, including leadership, role assignment, closed-loop communication, resource use, and mutual monitoring. It is taught through simulation and improves team performance during rare critical events.