IUSM Indy General Anesthetics
Order by
42 terms
Terms | Definitions |
|---|---|
 general anesthesia | Induction of a state of unconsciousness with the absence of pain sensation over the entire body, through the administration of anesthetic drugs. |
| balanced anesthesia | anesthesia produced by safe doses of 2 or more agents or methods of anesthesia, each of which contributes to the total desired effect. Goal: desired actions summate; undesirable actions are minimized. |
| Name 4 of the preanesthetic medications considered preoperatively. | Benzodiazepines: help sedate; ↓ anxiety Antihistamines: bronchodilation; ↓ bronchospasm Antiemetics: anti-nausea Opioids: if concerned of analgesia |
| Describe the proposed mechanisms of action of general anesthetics. | General anthetics ↑ activity of GABA receptors and K⁺ channels (enhancement of inhibitory synaptic activity) and ↓ activity of ACh receptors and NMDA glutamate receptors (reduction of excitatory synaptic activity) |
| Name 3 barbiturates | thiopental, thiamylal, methohexital |
| thiopental | Action: intravenous anesthetic- barbiturate •rapid onset anesthesia (high lipid solubility → brain) Pharmacokinetics •terminated by redistribution •TERMINAL t½ LONGER W/ CONSTANT INFUSION (BUT METHOHEXITAL- rapid CLEARANCE) Clinical Use •induction of anesthesia Toxicity •↓ cerebral metabolism + blood flow •↓ BP •↓ respiration •paradoxical excitation (muscle tremors)- esp. methohexital •hiccups- esp. methohexital |
| thiamylal | Action: intravenous anesthetic- barbiturate •rapid onset anesthesia (high lipid solubility → brain) Pharmacokinetics •terminated by redistribution •TERMINAL t½ LONGER W/ CONSTANT INFUSION (BUT METHOHEXITAL- rapid CLEARANCE) Clinical Use •induction of anesthesia Toxicity •↓ cerebral metabolism + blood flow •↓ BP •↓ respiration •paradoxical excitation (muscle tremors)- esp. methohexital •hiccups- esp. methohexital |
| methohexital | Action: intravenous anesthetic- barbiturate Pharmacokinetics •rapid onset anesthesia (high lipid solubility → brain) •terminated by redistribution •TERMINAL t½ LONGER W/ CONSTANT INFUSION (BUT METHOHEXITAL- rapid CLEARANCE) Clinical Use •induction of anesthesia Toxicity •↓ cerebral metabolism + blood flow •↓ BP •↓ respiration •paradoxical excitation (muscle tremors)- esp. methohexital •hiccups- esp. methohexital |
| Propofol | Action: intravenous anesthetic Pharmacokinetics •rapid onset + duration similar to barbituate → REDISTRIBUTION still important •RAPID CLEARANCE compared to barbiturates Clinical Use •induction + maintenance anesthesia → LESS HANGOVER effect than thiopental •↑ use as sedative outside OR (RIP MJ) •poor analgesia Toxicity •same as barbiturates: ↓ cerebral blood flow + metabolism; ↓BP (hypotension); ↓ respiration •PAIN ON INJECTION |
| Etomidate | Action: intravenous anesthetic Clinical Use •Induction anesthesia •CARDIOSTABLE- used in pts with risk of HYPOTENSION •poor analgesia Toxicity •same as barbiturates: ↓ cerebral blood flow + metabolism; ↓ respiration (except NO ↓BP) •PAIN ON INJECTION (~propofol) •significant NAUSEA + VOMITING (choking risk) •SUPPRESSION of ADRENOCORTICAL STRESS RESPONSE (LONG TERM) Drug interactions •fentanyl prolongs elimination half-life |
| Ketamine | Action: intravenous anesthetic •blocks GLUTAMATE receptors (not GABAergic) •DISSOCIATIVE STATE: amnesia despite the pt being awake Metabolism: liver Clinical Use •Byitself for short procedures; maintenance (multiple injections); induction followed by different agent •ANALGESIA •↑ BP/bronchodilator- useful in pts at risk for hypotension or bronchospasm •children undergoing short painful procedure Toxicity: •same as barbituate: ↑ cerebral blood flow •CATALEPTIC STATE •EMERGENCE OF DELIRIUM: adults (not kids); disorientation, excitation, hallucinations •analog of PCP- target NMDA receptor, drug of abuse Drug interactions •potentiates nondepolarizing muscle relaxants •ketamine + theophylline predispose to seizures |
| Which intravenous anesthetics cause pain at the injection site? | propofol, etomidate |
| Which intravenous anesthetics shoud be used in pts at risk for hypotension? | etomidate, ketamine |
| Which intravenous anesthetic should be used in pts at risk for bronchospasm? | ketamine |
| Which intravenous anesthetics causes nausea and vomiting as well as suppresses the stress response? | etomidate |
| Which intravenous anesthetic cause cataleptic state? | Ketamine |
| Which intravenous anesthetic is associated with emergence delirium- disorientation, excitation, hallucinations?` | Ketamine |
| Which intravenous anesthetic shows slow clearance after continuous infusion? | thiopental |
| Which intravenous anesthetics cause a depressed respiratory drive? | all of them |
| Which intravenous anesthetics cause muscular rigidity? | opioids, ketamine |
| Why is Dalton's Law important for understanding how inhalation anesthetics are administered? |  Ptotal = P₁+ P₂+ P₃ A high partial pressure of the gas in the lungs results in more rapid achievement of anesthetic levels in the blood. |
| Use Henry's Law to explain why although the partial pressure of a gas may be equal in all tissues, the concentration is not. | Concentrations of drug in liquid = partial pressure of gas x solubility (λ) The amount of gas with affinity for liquid (soluble) does not contribute to partial pressure → not available to enter other tissues |
| Define partition coefficient and how it is used to explain the amount of time to induce anesthesia. |  Ratio of concentrations of the anesthetic in two tissues when the partial pressure is the same in the tissues and is based on Henry's Law. The higher the blood/gas partition coefficient, the longer it takes to induce anesthesia and the longer the duration of action |
| Why does a higher cardiac output result in slower induction of an inhaled anesthetic? | High cardiac output results in more rapid uptake such that the rate of rise in the alveolar partial pressure and the speed of induction are slowed → delay time to reach anesthetic equilibrium. (If a lot of blood is moving through, it will be hard to saturate the system) |
| Name and describe the 4 major determinants of inhaled anesthetic concentration. | 1. INSPIRED ANESTHETIC CONCENTRATION: Dalton's Law; high partial pressure of the gas in the lungs results in more rapid achievement of anesthetic levels in the blood 2. ALVEOLAR VENTILATION: the greater the ventilation,the more rapid is the rise in the alveolar and blood partial pressure of the agent and the onset of anesthesia. 3. BLOOD/GAS SOLUBILITY (λ b/g): the more rapidly a drug equilibrates with the blood, the more quickly the drug passes into the brain to produce anesthetic effects. Drugs with a low b:g partition coefficient equilibrates more rapidly than those with a higher blood solubility. 4. PULMONARY PERFUSION (CARDIAC OUTPUT): at high pulmonary blood flows, the gas partial pressure rises at a slower rate → speed of onset of anesthesia reduced. At low flow rates, onset is faster. |
| What is MAC and why is it used in inhalation anesthetics? | Minimum Alveolar Concentration (MAC) •concentration of gas in the alveolar compartment that results in a lack of response to a noxious stimulus in 50% of subjects USED TO COMPARE POTENCY OF INHALATION ANESTHETICS and esp. useful when combining inhalation anesthetics (just combine MACs) |
| How can MAC be monitored in real time? | At equilibrium, the concentration in the alveolar compartment closely approximates the concentration in expired air |
| Name the 2 limitations of MAC. | 1. 50% of pts still respond 2. Absence of response to pain may not indicate loss of consciousness |
| halothane | Action: inhaled anesthetic •hi b/g partition coefficient → slow induction, slow offset •POTENT! (MAC = 0.75%) Clinical use •maintenance (discontinued in US) •used in developing countries (popular in peds) Toxicity •metabolite toxicity- trifluoroacetylchloride •↑ cerebral blood flow w/ potential to ↑ intracranial pressure (differs from propofol, thiopental)- like enflurane •inhibits ventilatory response to ↑ CO₂or to hypoxemia •LIVER TOXICITY- DRUG-INDUCED HEPATITIS AND HEPATIC NECROSIS •MALIGANT HYPERTHERMIA-w/ all halogenated agents esp. halothane |
| Volatile anesthetics can cause malignant hyperthermia. How does malignant hyperthermia predispose patients to muscle rigidity? | Anesthetic agents trigger an increase in intracellular calcium in skeletal muscle. |
| enflurane | Action: inhaled anesthetic •hi b/g partition coefficient → slow induction Clinical use •maintenance (diminished substantially in US) Toxicity •↑ cerebral blood flow w/ potential to ↑ intracranial pressure- like halothane •inhibits ventilation response to ↑CO₂or to hypoxemia- like halothane •↑ SEIZURE ACTIVITY |
| isoflurane | Action: inhaled anesthetic •lower b/g partition coefficient than halothane (1.2 v 2.4) → induction can be achieved in 10 minutes Clinical Use •maintenance b/c PUNGENT ODOR •most commonly used anesthetic in US for many years Side effects •tachycardia •peripheral vasodilation and hypotension (common) •DILATES CORONARY ARTERIES → CORONARY STEAL → AVOIDED IN PTS W/ CAD |
| desflurane | Action: inhaled anesthetic •LOWEST b/g partition coefficient → rapid onset + rapid changes + rapid emergence (5-10 min) •low fat solubility Clinical Use •maintenance (not induction due to airway irritant) •outpatient surgeries Side effects •concentration dependent ↓ in BP BUT CO NOT affected •COUGHING, SALIVATION, BRONCHOSPASM IN AWAKE PTS → strong AIRWAY IRRITANT → NOT used for induction •may produce carbon monoxide with dry soda lime (CO₂absorbent) |
| sevoflurane | Action: inhaled anesthetic •low b/g partition coefficient → rapid onset + rapid recovery Clinical use •induction •outpt anesthesia + peds b/c not irritating to airway •no significan tachycardia Side effects •some concern that interaction of sevoflurane with soda lime (CO₂absorbent) produces nephrotoxic substance "Compound A." →FDA recommends sevoflurane be given as fresh gas flow |
| nitrous oxide | Action: inhaled anesthetic •IMPOTENT (MAC = 105%) •insoluble in blood and tissues → rapid induction + emergence Clinical use •weak anesthetic agent but significant analgesia •used primarily as adjunct to other inhalational or IV anesthetics •N2O CANNOT be used at concentration above 80% → HYPOXIA. Only used as adjunct to other anesthetics at [50-70%] Side effects •accumulates in gas-filled spaces → BOWEL DISTENTION + PNEUMOTHORAX + PAIN W/ OBSTRUCTED INNER EAR •GIVE 100% O₂at END of anesthesia → avoid DILUTING O₂and causing "DIFFUSIONAL HYPOXIA" •CONTRAINDICATED in pts with PULMONARY HTN due to ↑ vascular resistance |
| methoxyflurane | Action: inhaled anesthetic •slow onset + offset Clinical Use •foreign ambulance services as an ER analgesic Side Effects •EXTENSIVE METABOLISM IN KIDNEY (only 35% excreted unchanged by exhalation) → production of FLUORIDE ions → KIDNEY damage |
| Which inhaled anesthetic causes gaseous space enlargement? | nitrous oxide |
| Which inhaled anesthetics cause metabolite toxicity? | trifluoroacetylchloride w/ halothane kidney damage w/ methoxyflurane |
| Which inhaled anesthetics cause malignant hyperthermia? | Halogenated agents except nitrous oxide; halothane may be worse than others |
| A high blood-gas λ leads to a shorter or longer induction time? | LONGER The lower the blood solubility of an anesthetic, the shorter its induction time |
| The lower the MAC, the stronger or weaker the potency of an inhaled anesthetic? | STRONGER The lower the minimal concentration of an anesthetic required to prevent pain in 50% of subjects (MAC), the higher its potency |
| The lower the oil-gas λ, the stronger or weaker the potency of the inhaled anesthetic? | WEAKER The higher the lipid solubility of an anesthetic, the higher its potency. ENANTIOMERS CAN BE AN EXCEPTION TO THIS RULE. |
First Time Here?
Welcome to Quizlet, a fun, free place to study. Try these flashcards, find others to study, or make your own.