ACVAA key terms

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents gross purposeful movement in 50 percent of subjects exposed to a standardized noxious stimulus. It is used to compare potency and guide vaporizer settings.

The rate at which anesthetic partial pressure in the alveoli rises toward the inspired value after induction. It depends on ventilation, blood solubility, cardiac output, and the alveolar-to-venous gradient.

The ratio of anesthetic concentration in blood to that in gas at equilibrium. A low value means rapid equilibration and fast induction and recovery; a high value means slower onset and offset.

The ratio of anesthetic concentration in a lipid-like solvent to that in gas at equilibrium. It correlates with potency, so agents with higher values generally have lower MAC.

The accelerated rise in alveolar concentration of a second, less soluble anesthetic caused by rapid uptake of a highly soluble first gas such as nitrous oxide, which concentrates remaining gases.

The phenomenon in which a high inspired fraction of a soluble anesthetic raises its own alveolar concentration faster than expected, because large uptake shrinks alveolar gas volume and draws in more fresh gas.

Deliberately setting a vaporizer above the target concentration during induction to speed equilibration between alveolar and brain partial pressures, then reducing to the maintenance setting once the desired depth is reached.

The reduction in the alveolar concentration of an inhalant needed to maintain anesthesia when another drug, such as an opioid, alpha-2 agonist, or local anesthetic, is co-administered.

The alveolar anesthetic concentration at which 50 percent of subjects respond to command. It estimates the threshold for loss of consciousness and is typically about one-third of MAC.

The overall level of central nervous system depression produced by anesthetic drugs, judged from reflexes, muscle tone, eye position, and autonomic responses and balanced against surgical stimulation.

Combining several drugs with different actions, such as a hypnotic, an analgesic, and a muscle relaxant, so each is given at a lower dose to reduce total side effects.

The neural encoding of a noxious stimulus by sensory receptors and pathways, which can occur with or without conscious perception of pain and is often inferred from autonomic or motor responses under anesthesia.

An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. In animals it is inferred from behavior and physiologic changes.

Using two or more analgesic drugs or techniques that act at different points in the pain pathway, allowing lower doses of each and better relief with fewer adverse effects.

Administering analgesia before a noxious event so that central and peripheral sensitization is prevented or reduced, rather than treating pain only after it has become established.

A progressive increase in the response of spinal dorsal horn neurons to repeated noxious stimulation, reflecting central sensitization that can amplify postoperative pain.

An activity-dependent increase in the excitability of neurons in the central nervous system after intense or repeated nociceptive input, producing amplified pain responses and expanded receptive fields.

An increased painful response to a stimulus that normally provokes pain, often resulting from sensitization of peripheral nociceptors or central pain pathways.

Pain produced by a stimulus that does not normally evoke pain, such as light touch, and a sign of altered sensory processing after nerve injury or sensitization.

Paradoxical increased pain sensitivity during or after opioid exposure, distinct from tolerance, arising from central sensitization and often managed by reducing the opioid or adding adjuncts.

A reduced response to a drug after repeated administration, so that a higher dose is required to produce the original effect; with opioids it develops to some effects more than others.

A ligand that binds a receptor and produces a submaximal response even at full occupancy, so it can act as an agonist alone but may blunt full agonists given concurrently.

An opioid that activates one opioid receptor type while blocking another, producing analgesia with a ceiling effect and potentially precipitating withdrawal in animals already receiving pure agonists.

A delivery system applied to clipped skin that provides slow, sustained drug absorption over hours to days, commonly used with fentanyl or lidocaine for longer-term pain control.

Continuous intravenous or other administration of a drug at a fixed rate, calculated from dose, concentration, and patient weight, to maintain steady plasma levels for analgesia or anesthesia.

A pump-driven technique in which a computer model adjusts the infusion rate to reach and hold a chosen predicted drug concentration, typically in plasma or at the effect site.

A drug that reversibly blocks voltage-gated sodium channels in nerve membranes, preventing impulse conduction and producing loss of sensation in the supplied region when applied near the nerve.

Producing insensibility in a body region by blocking nerve conduction with local anesthetic, using techniques such as epidural, spinal, or peripheral nerve blocks.

Injection of local anesthetic, with or without an opioid, into the epidural space to block spinal nerve roots and provide analgesia or anesthesia to the hindquarters or abdomen.

The upper limit of local anesthetic dose calculated from body weight, intended to avoid systemic toxicity; it varies with agent, route, and whether a vasoconstrictor is added.

Adverse central nervous and cardiovascular effects after local anesthetic reaches the circulation, ranging from excitation and tremors to seizures, arrhythmias, and cardiovascular collapse.

The history, physical examination, and selected laboratory or imaging assessment performed before anesthesia to identify risks and to plan drugs, monitoring, and supportive care.

A five-category classification, with an added emergency designation, that grades a patient's overall systemic health before anesthesia to communicate risk among clinicians.

The likelihood of an adverse event during or after anesthesia, influenced by patient health status, procedure invasiveness, drug choices, monitoring, and the skill of the team.

Continuous measurement and display of inspired and expired carbon dioxide concentration, used to confirm tracheal intubation, assess ventilation, and detect circuit or equipment problems.

The carbon dioxide concentration measured at the end of expiration, which approximates alveolar and arterial carbon dioxide and helps guide ventilation during anesthesia.

Noninvasive estimation of arterial hemoglobin oxygen saturation from light absorption across a pulsatile vascular bed, used to detect hypoxemia during anesthesia and recovery.

An abnormally low oxygen content or partial pressure in arterial blood, detected by pulse oximetry or blood gas analysis and requiring prompt correction of ventilation, airway, or circulation.

Inadequate alveolar ventilation relative to metabolic needs, producing rising arterial carbon dioxide and falling oxygen and often seen with anesthetic-induced respiratory depression or airway obstruction.