ABA ADVANCED Exam key terms

A tapered vertical tube containing a float; gas flow lifts the float, and the height indicates flow rate, calibrated for a specific gas at atmospheric pressure. Reading is inaccurate if downstream back-pressure compresses the gas or if a different gas is used.

A device that splits carrier gas so part flows over a liquid anesthetic and part bypasses it, then reunites the streams to deliver a set concentration. Output depends on temperature, flow, and the agent's saturated vapor pressure, so modern units are agent-specific and temperature-compensated.

Granules of calcium hydroxide with sodium or potassium hydroxide that absorb exhaled carbon dioxide in a circle system through a chemical reaction producing water and heat. Exhaustion is signaled by color change, rising inspired CO2, or unexpected heat loss from the canister.

A closed or semiclosed circuit in which exhaled gas passes through a CO2 absorber, unidirectional valves, and a reservoir bag before rebreathing, allowing low fresh gas flows that conserve heat, humidity, and volatile agent while reducing operating-room pollution.

Continuous display of carbon dioxide concentration versus time in respired gas. The waveform confirms tracheal intubation, detects esophageal placement, disconnection, and obstruction, and its end-tidal value approximates alveolar and arterial CO2 in healthy lungs.

Noninvasive estimation of arterial oxygen saturation by comparing red and infrared light absorption across a pulsatile vascular bed. The derived ratio is calibrated against arterial samples, but readings become unreliable with poor perfusion, motion, and dyshemoglobins such as carboxyhemoglobin.

A four-resistor circuit that converts a small resistance change into a proportional voltage; used in pressure transducers and some gas analyzers. Excitation voltage instability or temperature drift produces measurement error.

A dimensionless index of flow pattern calculated from fluid density, velocity, tube diameter, and viscosity. High values predict turbulent flow, which increases resistance and makes pressure-flow relationships nonlinear, affecting flowmeters, airway devices, and breathing tubing.

A pressure-sensitive device that reduces or stops nitrous oxide and other gas flows when oxygen supply pressure falls, preventing delivery of a hypoxic mixture. It is not a substitute for an oxygen analyzer or low-pressure alarms.

A very small current, on the order of 100 microamps, delivered directly to the myocardium through an intracardiac conductor. It can cause ventricular fibrillation at levels far below macroshock thresholds, mandating isolated patient leads and strict leakage-current limits.

The time for plasma concentration to fall by half after stopping an infusion, accounting for how long the infusion ran. It lengthens with infusion duration for lipophilic drugs such as thiopental but remains relatively flat for remifentanil, informing recovery predictions.

The modeled drug concentration at the site of action, linked to plasma concentration through a rate constant that describes equilibration delay. It explains hysteresis between plasma levels and observed clinical effect and underlies target-controlled infusion.

The alveolar concentration of a volatile agent at one atmosphere that prevents movement in response to a standard surgical stimulus in 50 percent of patients. It is an inverse measure of potency and is additive between agents.

The apparent volume relating the total amount of drug in the body to its plasma concentration at equilibrium. Large values indicate extensive tissue uptake, and the value determines the loading dose needed to reach a target concentration.

The volume of plasma from which drug is completely removed per unit time by metabolism and excretion. Together with volume of distribution it sets elimination half-life and determines the maintenance infusion rate required for steady state.

Metabolism of an orally absorbed drug in the intestinal wall and liver before it reaches the systemic circulation, reducing oral bioavailability. Drugs with high first-pass extraction need larger oral doses or an alternative route to achieve comparable effect.

Spontaneous, nonenzymatic breakdown of a quaternary ammonium compound at physiologic pH and temperature, yielding inactive metabolites. Cisatracurium undergoes this pathway, so its duration is largely independent of hepatic and renal function.

A modified gamma-cyclodextrin that encapsulates rocuronium and vecuronium in plasma, reversing deep aminosteroid neuromuscular blockade within minutes. It has no effect on succinylcholine or benzylisoquinolinium relaxants and can cause anaphylaxis and bradycardia.

Inherited or acquired reduction in plasma butyrylcholinesterase activity that prolongs succinylcholine and mivacurium blockade, sometimes for hours. Management is supportive ventilation and sedation; cholinesterase-containing blood products are rarely required.

The product of cardiac output and arterial oxygen content, roughly 1000 mL per minute at rest. It reflects the adequacy of convective oxygen transport; below critical thresholds, tissue extraction rises and anaerobic metabolism with lactate production begins.

Blood passing through lung regions with a ventilation-perfusion ratio near zero, so it returns to the left heart without taking up oxygen. Shunt causes hypoxemia that responds poorly to supplemental oxygen and is quantified as a fraction of cardiac output.

The portion of each breath that does not participate in gas exchange, comprising anatomic airways and nonperfused alveoli. It is estimated by the Bohr equation and increases with hypotension, pulmonary embolism, and high positive-pressure ventilation.

Constriction of small pulmonary arteries in response to alveolar hypoxia, diverting blood toward better-ventilated regions. It improves gas exchange but raises right ventricular afterload, and the response is blunted by volatile anesthetics and vasodilators.

The intrinsic ability of cerebral arterioles to keep blood flow nearly constant across a range of mean arterial pressures, typically about 60 to 150 mmHg. It is impaired by trauma, ischemia, and some anesthetics, making pressure extremes hazardous.

The volume of gas remaining in the lungs at end-expiration during quiet breathing, set by the balance of lung and chest wall recoil. It falls with supine position, obesity, and anesthesia, promoting atelectasis and airway closure.

The difference between calculated alveolar oxygen tension and measured arterial oxygen tension. It widens with shunt, ventilation-perfusion mismatch, and diffusion impairment, helping separate hypoxemia caused by hypoventilation from that caused by intrinsic lung disease.

The difference between measured serum cations and anions, calculated as sodium minus chloride and bicarbonate. An elevated gap indicates accumulation of unmeasured acids such as ketones, lactate, or toxins; a normal gap acidosis suggests bicarbonate loss.

Prolonged absence of agonist, as after spinal cord injury or major burns, increases postsynaptic acetylcholine receptor number, and receptors may spread beyond the motor end plate. Subsequent succinylcholine can then cause exaggerated potassium release and cardiac arrest.

An induction technique that minimizes the interval between loss of consciousness and tracheal intubation to reduce aspiration risk, typically using a fast-acting hypnotic plus succinylcholine or rocuronium, with cricoid pressure and avoidance of bag-mask ventilation.

A pharmacogenetic hypermetabolic crisis triggered by volatile anesthetics and succinylcholine, marked by rising end-tidal CO2, muscle rigidity, tachycardia, and later hyperthermia. Treatment is dantrolene, removal of triggers, active cooling, and management of hyperkalemia and rhabdomyolysis.

A spectrum of neurologic and cardiac effects from excessive local anesthetic in the bloodstream, ranging from perioral numbness and tinnitus to seizures and cardiovascular collapse. Management includes airway support, benzodiazepines, and lipid emulsion rescue with prolonged resuscitation.

A risk tool for postoperative nausea and vomiting based on four predictors: female sex, nonsmoking status, history of postoperative vomiting, and planned postoperative opioid use. Each adds a point and guides prophylactic antiemetic selection and combination therapy.

A multimodal perioperative pathway using evidence-based elements such as preoperative counseling, opioid-sparing analgesia, goal-directed fluids, avoidance of drains and prolonged fasting, early feeding, and early mobilization to shorten stay and reduce complications.

Postoperative weakness from incomplete recovery at the neuromuscular junction, defined by a train-of-four ratio below 0.9. It increases aspiration, hypoxemia, and reintubation risk; quantitative monitoring and adequate reversal are the main preventive measures.

The clinical situation in which a trained anesthesiologist has difficulty with mask ventilation, supraglottic device placement, laryngoscopy, or intubation. A preformulated algorithm guides progression from optimization and alternative devices to rescue and, if needed, front-of-neck access.

Myocardial damage after noncardiac surgery identified by elevated troponin without another explanation, frequently silent and linked to higher short-term mortality. Screening is considered in high-risk patients, and care centers on hemodynamic optimization, monitoring, and secondary prevention.

A core temperature below 36 degrees Celsius developing around anesthesia because of vasodilation, impaired thermoregulation, and cold exposure. It worsens bleeding, surgical site infection, and drug metabolism, and is prevented with active cutaneous warming and warmed intravenous fluids.