Intravenous Anesthetics & Pharmacology Review

Vocabulary flashcards reviewing intravenous anesthetics, opioids, neuromuscular blockers, reversal agents, non-opioid analgesics, and inhalational anesthetics based on Clinical Anesthesiology, 7th Edition.

GABA-A Receptor (Benzodiazepines)

The receptor complex where benzodiazepines bind to a site distinct from barbiturates, increasing the frequency of chloride channel opening to enhance endogenous GABA and cause neuronal hyperpolarization.

Midazolam

A short-acting benzodiazepine ($t_{1/2} \text{ ~2 h}$) featuring an imidazole ring that makes it water-soluble at $\text{pH} < 4$ and lipid-soluble at $\text{pH } 7.4$.

Lorazepam

A benzodiazepine with an elimination half-life of approximately $15\text{ h}$ formulated in a propylene glycol vehicle.

Diazepam

A long-acting benzodiazepine ($t_{1/2} \text{ ~30 h}$) that undergoes enterohepatic circulation resulting in a second peak at $6\text{--}12\text{ h}$, with active metabolites (desmethyldiazepam) prolonging sedation.

Flumazenil

A competitive antagonist at the GABA-A benzodiazepine site characterized by rapid onset and short duration, carrying a risk of re-sedation when reversing long-acting benzodiazepines.

Ketamine

A WHO Essential Medicine noncompetitive NMDA receptor antagonist that blocks glutamate excitatory transmission, providing analgesia, amnesia, and unconsciousness as a dissociative anesthetic.

Dissociative Anesthesia

A state produced by ketamine where the patient appears awake (eyes open, intact tone, swallowing) and preserves airway reflexes, but cannot meaningfully process sensory input.

Norketamine

The major active metabolite of ketamine possessing approximately one-third the potency of the parent drug.

Ketofol

A $1:10$ ratio combination of ketamine to propofol used for procedural sedation to balance hemodynamics and reduce emergence reactions.

Etomidate

A carboxylated imidazole non-barbiturate IV hypnotic (R+ isomer active) that enhances GABA-A transmission without providing analgesia or direct myocardial depression.

Etomidate-Induced Adrenal Suppression

Inhibition of CYP11B1 (reducing cortisol) and CYP11B2 (reducing aldosterone) caused even by a single dose of etomidate; continuous ICU infusions increase mortality in septic and critically ill patients.

Propofol

An alkylphenol derivative formulated as a 1% milky white oil-in-water emulsion (containing soybean oil, glycerol, and egg lecithin) that potentiates GABA-A receptors, causes marked hypotension, and commonly induces apnea.

Propofol Infusion Syndrome (PRIS)

A severe complication associated with high doses and long infusions of propofol in critically ill children or ICU patients, characterized by metabolic acidosis, lipemia, rhabdomyolysis, cardiac failure, and death.

Fospropofol

A water-soluble prodrug of propofol with a slower onset of action used for endoscopy sedation.

Dexmedetomidine

A selective alpha-2 adrenergic agonist acting at the locus coeruleus in the brainstem to produce calm, cooperative sedation mimicking natural sleep without causing respiratory depression.

Opioid Receptor Mechanism

Activation of G-protein coupled receptors ($\text{Mu } \nu$, $\text{Kappa } \theta$, $\text{Delta } \tau$) leading to decreased adenylate cyclase and cAMP, inhibition of voltage-gated $\text{Ca}^{2+}$ channels, and activation of $\text{K}^+$ channels causing membrane hyperpolarization and reduced neurotransmitter release.

Mu (μ) Receptor Effects

Primary mediator of opioid analgesia, respiratory depression (most dangerous effect), euphoria, sedation, reduced GI motility/constipation, physical dependence, miosis (via Edinger-Westphal nucleus), and urinary retention.

Remifentanil

An ultra-short-acting opioid metabolized by plasma esterases ($t_{1/2} \text{ ~3 min}$) whose duration of action is context-insensitive.

Morphine-6-Glucuronide (M6G)

An active metabolite of morphine that accumulates in renal failure and prolongs opioid sedation and clinical effects.

Opioid-Induced Hyperalgesia (OIH)

A paradoxical increase in pain sensitivity resulting from opioid administration.

COX-1 vs COX-2

COX-1 is constitutive and provides gastric mucosal protection, platelet function, and renal blood flow; COX-2 is inducible and mediates inflammation and pain signaling.

Acetaminophen

A central-acting analgesic and antipyretic agent with minimal anti-inflammatory activity, no platelet inhibition, and no GI mucosal damage, which carries a risk of hepatotoxicity in overdose.

Aspirin-Induced Asthma

A reaction occurring in up to 20% of asthmatics caused by leukotriene overflow following COX inhibition by aspirin, seen with higher incidence in patients with chronic rhinitis and nasal polyps.

Gabapentinoids

Antiepileptic-derived drugs (gabapentin and pregabalin) that bind to the alpha-2-delta subunit of voltage-gated $\text{Ca}^{2+}$ channels to reduce neurotransmitter release, without acting directly on GABA receptors.

Neuromuscular Blocking Agents (NMBs)

Quaternary ammonium compounds that do not cross the blood-brain barrier and provide skeletal muscle paralysis ONLY, without providing unconsciousness, amnesia, or analgesia.

Train-of-Four (TOF) Ratio

An objective monitoring measurement for neuromuscular blockade where a ratio $\text{>= 0.90}$ indicates safe recovery; fade is observed in nondepolarizing blocks or Phase II succinylcholine blocks.

Adductor Pollicis

The most sensitive muscle to neuromuscular blocking agents, recovering last from paralysis and used as the standard site for objective TOF monitoring.

Succinylcholine

The only depolarizing NMB in routine clinical use, consisting of two linked ACh molecules that cause persistent end-plate depolarization (Phase I block) with the fastest onset ($30\text{--}60\text{ seconds}$) and short duration ($< 10\text{ minutes}$).

Pseudocholinesterase

Plasma cholinesterase responsible for metabolizing succinylcholine in the bloodstream before it reaches the neuromuscular junction.

Dibucaine Number

A laboratory measurement testing the quality and function of pseudocholinesterase; normal enzyme produces a number of $\text{~80}$, whereas homozygous atypical enzyme ($\text{~20}$) causes prolonged paralysis lasting $4\text{--}8\text{ hours}$.

Succinylcholine-Induced Hyperkalemia

A dangerous elevation of serum potassium (normally $0.5\text{ mEq/L}$, but capable of causing cardiac arrest) triggered by succinylcholine in patients with burns, spinal cord injury, stroke, denervation, Duchenne MD, GBS, or severe sepsis.

Hofmann Elimination

An organ-independent chemical breakdown process in plasma responsible for the metabolism of atracurium (combined with ester hydrolysis) and cisatracurium (exclusive elimination route).

Rocuronium

A steroidal nondepolarizing NMB with the fastest onset among nondepolarizing agents ($0.9\text{--}1.2\text{ mg/kg}$ RSI dose), reversible with sugammadex.

Pancuronium

A long-acting steroidal nondepolarizing NMB that causes vagal blockade and sympathomimetic effects resulting in tachycardia and hypertension; contraindicated in CAD and elderly patients.

Cholinesterase Inhibitors

Reversal agents (neostigmine, pyridostigmine, edrophonium) that inhibit acetylcholinesterase to increase ACh at the NMJ, requiring co-administration of an anticholinergic (glycopyrrolate or atropine) to prevent muscarinic side effects.

Physostigmine

A tertiary amine cholinesterase inhibitor that crosses the blood-brain barrier, used to treat central anticholinergic syndrome and atropine/scopolamine overdose.

Sugammadex

A modified gamma-cyclodextrin selective relaxant-binding agent that encapsulates steroidal NMBs (rocuronium > vecuronium) in a 1:1 complex in plasma, requiring no anticholinergic and ineffective against benzylisoquinoliniums or succinylcholine.

Minimum Alveolar Concentration (MAC)

The alveolar concentration of an inhalational anesthetic at which 50% of patients do not move in response to surgical incision ($1.3\text{ MAC} \rightarrow 95\text{\%}$ immobile; $0.3\text{--}0.4\text{ MAC} \rightarrow$ awakening).

Nitrous Oxide (N2O)

An NMDA antagonist inhalational agent with a MAC of 105% that expands closed gas spaces, causes diffusion hypoxia upon discontinuation, and does NOT trigger malignant hyperthermia.

Halothane Hepatitis

A key hepatotoxicity associated with halothane, occurring predominantly in middle-aged obese women following repeated anesthetic exposures.

Compound A

A nephrotoxic breakdown product formed when sevoflurane interacts with soda lime (nephrotoxic in rats, but with no proven clinical harm in humans).

Malignant Hyperthermia (MH) Triggers

Pharmacologic agents including all volatile inhalational anesthetics (halothane, isoflurane, desflurane, sevoflurane) and succinylcholine; nitrous oxide does not trigger MH.