ABPS Anesthesiology (BCA) key terms

The alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in 50% of patients in response to a standardized surgical stimulus; a potency index inversely related to lipid solubility.

The time needed for plasma drug concentration to fall by 50% after stopping a continuous infusion. It increases with infusion duration for lipid-soluble agents such as fentanyl but remains nearly constant for remifentanil.

The volume of gas left in the lungs after a normal passive exhalation. It reflects the balance between lung elastic recoil and chest wall outward pull, and falls with obesity, supine posture, and general anesthesia.

The portion of each breath that reaches the alveoli but does not participate in gas exchange, plus the volume in conducting airways. Bohr's equation calculates it from arterial and mixed expired carbon dioxide tensions.

The product of cardiac output and arterial oxygen content (DO2 = CO x CaO2), normally about 1000 mL per minute. It determines tissue oxygen supply and falls sharply with anemia, low output, or hypoxemia.

An inherited or acquired reduction in plasma butyrylcholinesterase activity that slows hydrolysis of succinylcholine and mivacurium, causing prolonged paralysis. Prolonged apnea may require continued ventilation and sedation until neuromuscular function returns.

The property of local anesthetics whereby blockade strengthens with repeated or high-frequency nerve firing, because drug binds preferentially to open and inactivated sodium channels. It explains why rapidly firing nerves are blocked more readily.

The difference between mean arterial pressure and intracranial pressure, or central venous pressure if that is higher. It drives cerebral blood flow and is specifically targeted in neuroanesthesia and after traumatic brain injury.

Continuous display of carbon dioxide concentration in respiratory gas over time, usually measured by infrared absorption. The end-tidal value and waveform shape confirm tracheal placement, ventilation, and cardiac output, and can reveal bronchospasm or disconnection.

Noninvasive estimation of arterial oxygen saturation by comparing light absorption at red and infrared wavelengths. Readings depend on adequate pulsatile flow and are unreliable with poor perfusion, dyshemoglobinemia, or motion artifact.

Peripheral nerve stimulation delivering four supramaximal twitches at 2 Hz to assess nondepolarizing neuromuscular blockade. The ratio of the fourth to first response guides reversal and extubation decisions.

A distorted arterial pressure waveform in which the tubing system or transducer adds compliance or resistance, flattening the systolic peak, lowering systolic readings, and abolishing the dicrotic notch.

A preoperative tool estimating major cardiac complications after noncardiac surgery using six factors: ischemic heart disease, heart failure, cerebrovascular disease, insulin-treated diabetes, creatinine above 2 mg/dL, and high-risk surgery.

An eight-item screening questionnaire for obstructive sleep apnea covering snoring, tiredness, observed apnea, hypertension, body mass index, age, neck circumference, and gender. Higher scores indicate greater risk and prompt consideration of perioperative monitoring.

A scoring system grading cirrhosis severity by bilirubin, albumin, INR, ascites, and encephalopathy, giving classes A to C. Higher classes predict perioperative mortality and guide the postoperative level of care.

A bedside airway classification based on visible oropharyngeal structures with the patient seated, mouth open, and tongue protruded. Classes III and IV suggest difficult laryngoscopy, although sensitivity and specificity are limited.

A grading of the laryngeal view during direct laryngoscopy, from grade 1 with a full glottic opening to grade 4 with only soft palate visible. Higher grades predict difficult intubation.

A life-threatening state in which both tracheal intubation and supraglottic or mask ventilation fail. Management is immediate front-of-neck access, usually scalpel-bougie cricothyrotomy, following a failed airway algorithm.

A supine position with the upper body and head elevated so that the external auditory meatus aligns with the sternal notch. It improves the laryngoscopic view in obese patients by reducing the effect of chest and breast tissue.

Anesthesia produced entirely by intravenous agents, typically propofol with an opioid, without inhaled anesthetics. It is used when inhalational agents are undesirable, such as for malignant hyperthermia susceptibility or frequent airway procedures.

Nitrous oxide is far more soluble in blood than nitrogen, so it diffuses into closed gas-filled spaces faster than nitrogen leaves, increasing volume and pressure. This can worsen pneumothorax, bowel distension, and air embolism.

A rare but potentially fatal complication of local anesthetic injection or absorption, presenting with perioral numbness, seizures, arrhythmias, and cardiovascular collapse. Treatment includes airway support, benzodiazepines, and early lipid emulsion.

A 20% lipid emulsion given for severe local anesthetic systemic toxicity, typically as a bolus followed by infusion. It is thought to create an intravascular lipid compartment that sequesters anesthetic and restores cardiac function.

A small volume containing epinephrine, and sometimes local anesthetic, injected before an epidural dose to detect intravascular or intrathecal placement. A heart rate rise or rapid motor block signals misplacement.

An ultrasound-guided fascial plane block injecting local anesthetic between the internal oblique and transversus abdominis muscles. It provides somatic analgesia for abdominal incisions but does not cover visceral pain.

A simplified risk score for postoperative nausea and vomiting using four predictors: female sex, nonsmoking status, history of PONV or motion sickness, and expected postoperative opioids. Scores guide prophylactic antiemetic selection.

Persisting neuromuscular weakness after anesthesia from incomplete reversal or clearance of muscle relaxants. It increases aspiration, airway obstruction, and hypoxemia, so extubation should be guided by a train-of-four ratio of at least 0.9.

A pharmacogenetic hypermetabolic crisis triggered by volatile anesthetics or succinylcholine, causing rigidity, hypercarbia, tachycardia, and fever. Treatment is dantrolene, aggressive cooling, and supportive care, with avoidance in susceptible patients.

A decline in memory, attention, or executive function persisting weeks to months after surgery, most common in older patients. Its causes are multifactorial and it is distinct from delirium.

Acute hypoxemic respiratory failure within a week of a known insult, with bilateral opacities not explained by heart failure and a PaO2/FiO2 ratio below 300 on positive pressure. Severity is graded as mild, moderate, or severe.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, defined operationally by a rise in SOFA score of at least 2. Septic shock adds vasopressor requirement and lactate above 2 mmol/L.

Placing a patient face down to improve oxygenation in severe acute respiratory distress syndrome by recruiting dorsal lung and reducing ventral overdistension. Sessions of at least 12 to 16 hours improve survival when applied early.

A developmental disorder in infants born before 37 weeks, with pauses in breathing over 20 seconds, or shorter pauses with bradycardia or desaturation. Former preterm infants are at risk after anesthesia and may need caffeine and monitoring.

Compression of the inferior vena cava and aorta by the gravid uterus after about 20 weeks of pregnancy, reducing venous return and cardiac output when the mother lies supine. Left uterine displacement relieves it.

A structured, systems-based investigation of a serious adverse event that asks why it happened and identifies contributing factors, rather than blaming individuals, to produce preventive recommendations.

A three-phase checklist covering sign-in, time-out, and sign-out that standardizes communication before induction, before incision, and before leaving the operating room. Its use reduces surgical morbidity and mortality.

Retrospective review of malpractice claims to identify patterns in injury, care, and payment, used to guide safety and quality improvement in anesthesiology. It describes associations rather than proving causation.