EHPLE Anesthesia key terms

The volume of gas left in the lungs after a normal passive exhalation. It reflects the balance between outward chest wall recoil and inward lung elastic recoil, and it is the main oxygen reservoir during apnea.

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

Collapse or loss of inflation of lung tissue. In anesthesia it commonly develops in dependent lung regions soon after induction, producing shunt, reduced compliance, and postoperative pulmonary complications.

A transient sustained increase in airway pressure intended to reopen collapsed alveoli. It is usually followed by adequate positive end-expiratory pressure to keep the recruited lung open.

Airway pressure maintained above atmospheric at the end of exhalation during positive-pressure ventilation. It increases functional residual capacity, reduces atelectasis, and can impair venous return and cardiac output at high levels.

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in response to a standardized surgical stimulus in 50 percent of patients. It allows comparison of potency between volatile agents.

The phenomenon in which rapid uptake of a high-concentration soluble gas such as nitrous oxide increases the alveolar concentration of a concurrently administered less soluble agent, speeding its induction.

The time required for the plasma concentration of a drug to fall by half after stopping an infusion, measured from the moment the infusion ends. It lengthens as infusion duration increases for drugs with slow redistribution or slow elimination.

The estimated concentration of a drug at its site of action, such as the brain, rather than in plasma. Target-controlled infusion systems model it to predict onset and offset of clinical effect.

The point at which increasing a drug dose produces no further increase in the desired effect but continues to increase adverse effects. It is clinically important with local anesthetics and opioid analgesics.

Administration of high inspired oxygen before induction of anesthesia to replace nitrogen in the lungs with oxygen. It prolongs the safe apnea time before desaturation, particularly in obese, pregnant, or critically ill patients.

Continued oxygen delivery to the lungs during apnea without active ventilation, driven by mass flow of oxygen from the pharynx into the alveoli as oxygen is absorbed. It slows the rate of desaturation during airway procedures.

Delivery of warmed, humidified oxygen at flows up to around 60 liters per minute through nasal cannulae. It provides a modest positive airway pressure, washes out nasopharyngeal dead space, and supports oxygenation during sedation or airway management.

A six-category scale from one to six that describes a patient's overall health before anesthesia, from healthy to brain-dead organ donor. It is used for risk communication and audit, not as a precise outcome predictor.

The process of estimating the likelihood of adverse cardiac, pulmonary, or other outcomes around surgery using clinical history, functional capacity, and validated tools such as the Revised Cardiac Risk Index or cardiopulmonary exercise testing.

A collaborative process in which the clinician explains options, benefits, and risks and the patient's values and preferences are incorporated into the chosen plan of care. It is central to informed consent for anesthesia.

A patient's voluntary agreement to a procedure after receiving and understanding information about its nature, purpose, material risks, alternatives, and the consequences of refusal, with the capacity to decide.

A clinical situation in which a trained anesthesia professional experiences difficulty with face-mask ventilation, supraglottic airway placement, laryngoscopy, tracheal intubation, or emergency invasive airway access. It is anticipated or unanticipated and requires an algorithm-based response.

A four-grade scale describing the laryngeal view obtained at direct laryngoscopy, from full visualization of the vocal cords to no visible laryngeal structures. Higher grades predict greater intubation difficulty.

Use of a laryngoscope with a camera at the blade tip to display the glottis on a screen. It improves glottic visualization compared with direct laryngoscopy, especially in difficult airways and cervical spine precautions.

A life-threatening emergency in which neither tracheal intubation nor any other method of oxygenation succeeds. It mandates immediate emergency front-of-neck airway access, such as scalpel-bougie cricothyrotomy.

An airway device inserted blindly into the pharynx that seals around the laryngeal inlet to deliver ventilation without entering the trachea. It is used for rescue ventilation and for short procedures in appropriately selected patients.

An induction technique designed to minimize the interval between loss of protective reflexes and tracheal intubation, typically using a rapid-onset induction agent and neuromuscular blocker with minimal or no mask ventilation, to reduce aspiration risk.

Chemical lung injury caused by inhalation of gastric contents, leading to bronchospasm, hypoxemia, and sometimes acute respiratory distress. Risk is reduced by fasting, cricoid pressure where indicated, and rapid sequence induction.

A modified gamma-cyclodextrin that encapsulates and inactivates aminosteroid neuromuscular blockers such as rocuronium and vecuronium. It can reverse even deep blockade rapidly, unlike acetylcholinesterase inhibitors.

The ratio of the fourth to the first evoked muscle response to four supramaximal ulnar nerve stimuli. A ratio above 0.9 indicates adequate recovery from neuromuscular blockade and reduces residual paralysis risk.

Continuous measurement and display of carbon dioxide concentration in respiratory gas over time. The waveform confirms tracheal tube placement, detects esophageal intubation and disconnection, and reflects ventilation and cardiac output.

Noninvasive estimation of arterial oxygen saturation using light absorbance differences between oxygenated and deoxygenated hemoglobin. It is affected by poor perfusion, motion, dyshemoglobinemias, and certain dyes.

A catheter placed in a peripheral artery, usually the radial, for continuous blood pressure monitoring and repeated blood sampling. It is indicated when hemodynamic instability or frequent arterial blood gases are expected.

Intraoperative fluid administration guided by dynamic measures of fluid responsiveness, such as stroke volume variation or pulse pressure variation, rather than fixed volumes. It aims to optimize cardiac output while avoiding overload.

A multimodal perioperative pathway combining evidence-based elements such as preoperative counseling, opioid-sparing analgesia, early feeding, and early mobilization to reduce complications and shorten hospital stay.

The combined use of two or more analgesic techniques or drug classes with different mechanisms, such as regional blocks, paracetamol, NSAIDs, and opioids, to improve pain relief and reduce individual drug side effects.

A reduced analgesic response to opioids after repeated exposure, requiring higher doses for the same effect. Patients on chronic opioids need higher intraoperative requirements and careful postoperative planning.

A spectrum of neurologic and cardiac toxicity caused by excessive plasma concentrations of local anesthetic, ranging from perioral tingling and seizures to arrhythmias and cardiac arrest. Treatment includes lipid emulsion therapy and airway support.

Production of insensibility in a region of the body by blocking nerve conduction, using local anesthetic deposited near peripheral nerves, plexuses, or the neuraxis. It may be used alone or combined with general anesthesia.

An inherited pharmacogenetic disorder in which volatile anesthetics or succinylcholine trigger uncontrolled skeletal muscle hypermetabolism, causing hyperthermia, rigidity, acidosis, and hyperkalemia. Dantrolene is the specific treatment.

Nausea or vomiting occurring within 24 hours after surgery. Risk is predicted by factors including female sex, nonsmoking status, history of motion sickness, and postoperative opioids, and is reduced by prophylaxis and opioid-sparing techniques.

Persisting muscle weakness after anesthesia due to incomplete reversal of neuromuscular blockade. It increases aspiration, airway obstruction, and hypoxemia risk, and is prevented by quantitative monitoring and adequate reversal.

A structured, confidential review of adverse events and deaths in which clinicians examine contributing factors and system weaknesses. It supports learning and quality improvement rather than individual blame.

A safety framework that distinguishes human error, at-risk behavior, and reckless conduct, responding with support, coaching, or sanctions accordingly. It encourages reporting while maintaining accountability.

A standardized verbal checklist completed before induction, before incision, and before the patient leaves the operating room, confirming identity, procedure, allergies, airway risk, and instrument counts to reduce avoidable harm.