CRNA (NCE) key terms

The alveolar concentration of an inhaled anesthetic, at one atmosphere, that prevents purposeful movement in response to a standardized surgical stimulus in 50% of patients. It is used to compare potency.

A measure of how readily an inhaled anesthetic dissolves in blood relative to gas. Lower values mean faster equilibration and quicker induction and emergence.

The time required for the plasma concentration of a drug to fall by half after an infusion is stopped. It lengthens as infusion duration increases, especially for lipophilic drugs.

The pH at which half of a drug molecule is ionized and half is un-ionized. For local anesthetics, it influences how much uncharged drug crosses nerve membranes and thus onset speed.

The accumulation of a weak acid or base on one side of a membrane because pH differences change its ionization and prevent it from crossing back. It explains fetal accumulation of local anesthetics.

The volume of gas left in the lungs after a normal exhaled breath. It provides an oxygen reservoir during apnea and is reduced by obesity, pregnancy, and anesthesia.

The lung volume at which small airways begin to close during exhalation. When it exceeds functional residual capacity, airway closure occurs during tidal breathing and can cause hypoxemia.

The pressure gradient that drives blood flow to the brain, calculated as mean arterial pressure minus intracranial pressure. It guides management of head-injured and neurosurgical patients.

The partial pressure of oxygen at which hemoglobin is 50% saturated, normally about 27 mm Hg. It indicates the position of the oxyhemoglobin dissociation curve.

An inherited or acquired deficiency of plasma butyrylcholinesterase that slows succinylcholine breakdown, causing prolonged paralysis. Patients may require extended ventilation until the drug is cleared.

A pharmacogenetic hypermetabolic reaction to volatile anesthetics and succinylcholine, mediated by abnormal ryanodine receptors. It causes rigidity, hyperthermia, acidosis, and requires immediate dantrolene and supportive treatment.

The principle that the skull is a rigid container holding brain, blood, and cerebrospinal fluid, so an increase in one component must be offset by a decrease in another or intracranial pressure rises.

A safety device on the anesthesia machine that stops or reduces nitrous oxide flow when oxygen supply pressure falls, helping prevent delivery of a hypoxic gas mixture.

A button that delivers a high flow of 100% oxygen, typically 35 to 75 L/min at pipeline pressure, directly into the breathing circuit, bypassing the vaporizer.

A system that collects and removes waste anesthetic gases from the breathing circuit and operating room, protecting staff from occupational exposure.

A carbon dioxide absorbent used in circle breathing systems. It contains calcium hydroxide and reacts with exhaled CO2 to prevent rebreathing and conserve inhaled anesthetic.

Continuous measurement and display of carbon dioxide in exhaled gas. It confirms ventilation, endotracheal tube placement, and cardiac output trends, and helps detect esophageal intubation or disconnection.

A peripheral nerve stimulation pattern that delivers four supramaximal stimuli to assess neuromuscular blockade. The number of twitches and the ratio guide reversal and extubation decisions.

An intubation technique for patients at high aspiration risk. It uses a preplanned induction dose, avoidance of positive-pressure ventilation, and prompt tracheal intubation, often with cricoid pressure.

A supraglottic airway device that sits over the laryngeal inlet and provides ventilation without tracheal intubation. It is useful for short procedures and difficult airways but does not protect against aspiration.

Reflex closure of the vocal cords caused by irritation of the laryngeal nerves, often during light anesthesia or airway manipulation. It can cause hypoxia and may need positive pressure, deepening anesthesia, or muscle relaxants.

Total intravenous anesthesia is the delivery of anesthesia entirely by intravenous drugs, usually propofol with an opioid, without inhaled anesthetics. It is useful for malignant hyperthermia susceptibility and procedures needing evoked potentials.

An infusion pump system that uses pharmacokinetic models to adjust drug delivery to achieve a chosen plasma or effect-site concentration. It allows predictable titration of intravenous anesthetics.

Pressure applied to the cricoid cartilage to compress the esophagus and reduce aspiration risk during induction. Its effectiveness is debated, and excessive force can obstruct ventilation or intubation.

A local anesthetic solution made denser than cerebrospinal fluid by adding glucose. In spinal anesthesia, it settles with gravity to block specific nerve roots, useful for unilateral or saddle blocks.

A technique for identifying the epidural space by feeling a sudden loss of resistance as a syringe plunger is advanced through the ligamentum flavum. It is used to place epidural catheters.

A positional headache that develops after a dural puncture and is worse when upright, caused by cerebrospinal fluid leakage. Severe cases are treated with an epidural blood patch.

Local anesthetic systemic toxicity is a potentially fatal reaction to local anesthetics that causes neurologic and cardiac symptoms. Treatment includes airway support, seizure control, and intravenous lipid emulsion.

A brachial plexus block performed between the anterior and middle scalene muscles. It anesthetizes the shoulder and upper arm but frequently causes phrenic nerve palsy and hoarseness.

Transversus abdominis plane block is a regional technique that injects local anesthetic between the internal oblique and transversus abdominis muscles to provide abdominal wall analgesia after surgery.

Manual or mechanical displacement of the pregnant uterus to the left during anesthesia. It relieves aortocaval compression, improving maternal venous return and fetal oxygenation.

Ventilation of only one lung, usually by placing a double-lumen endotracheal tube or bronchial blocker. It facilitates thoracic surgery but can cause hypoxemia from shunt.

A reflex in which pulmonary blood vessels constrict in poorly ventilated lung regions, redirecting blood to better-oxygenated areas. It helps maintain oxygenation during one-lung ventilation.

A pregnancy disorder of new hypertension and proteinuria or organ dysfunction after 20 weeks. Anesthesia concerns include difficult airway, pulmonary edema, and thrombocytopenia; neuraxial techniques are often preferred.

A condition in infants with hypertrophy of the pyloric muscle causing projectile vomiting and hypochloremic, hypokalemic metabolic alkalosis. Anesthesia requires fluid and electrolyte correction and aspiration precautions.

A six-category classification of a patient's preoperative health, from ASA I (healthy) to ASA VI (brain-dead organ donor). It predicts perioperative risk and is recorded for statistics.

A standardized team checklist used before induction, before incision, and before leaving the operating room. It improves communication and reduces wrong-site surgery, retention, and other preventable harms.

Conscious recall of events during general anesthesia, sometimes with pain or distress. It is more likely with light anesthesia, trauma, cardiac surgery, and neuromuscular blockade without adequate amnesia.

A stepwise plan for managing a failed mask ventilation or intubation. It emphasizes oxygenation, limiting attempts, calling for help, and choosing rescue devices such as supraglottic airways or surgical airways.

Review of malpractice claims to identify patterns in anesthesia injuries and improve safety. It has highlighted issues such as airway complications, monitoring, and medication errors.