Monday, 8-22-General Anesthetics-DSA-Kruse Flashcards
__ and ___ in conscious sedation protocols have the advantage of being reversible by the specific receptor antagonist drugs (flumazenil and naloxone, respectively)
Benzodiazepines and opioid analgesics
IV agents used in deep sedation protocols mainly include the sedative-hypnotics __ and __, sometimes in combo with potent __, depending on the level of pain associated with the surgery or procedure
Propofol and midazolam
Opioid analgesics or ketamine
These channels remain the primary inhibitory ion channels considered legitimate candidates of anesthetic action
Cl channels (GABAa and Glycine receptors) and K channels
What are some of the excitatory ion channel targets of general anesthetics?
Those activated by Ach (nAChRs and mAChRs), by EAAs (AMPA), kainite, and NMDA receptors, or by 5-HT receptors
Halothane, enflurane, isoflurane, desflurane, and sevoflurane are examples of these anesthetics
Volatile inhaled
NO is an example of this type of anesthetic
Gaseous inhaled
The driving force for uptake of an inhaled anesthetic is the __
Alveolar concentration
Describe the FA/F1 ratio and speed of inhaled anesthesia induction
The faster FA/F1 approaches 1, the faster anesthesia will occur during an inhaled induction
Agents with __ blood solubility (NO, desflurane), reach high arterial pressure rapidly, which in turn results in rapid equilibration with the brain and fast onset of action
Low
Agents with __ blood solubility (halothane) reach high arterial pressures slowly, which in turn results in slow equilibration with the brain and a slow onset of action
High
Describe the onset and recovery with inhaled NO
Rapid onset and recovery; incomplete anesthetic
Describe the volatility and recovery from inhaled desflurane
Low volatility; poor induction agent; rapid recovery
Describe the onset and recovery from inhaled sevoflurane
Rapid onset and recovery
Describe the onset and recovery with inhaled isoflurane, enflurane, and halothane
Medium rate of onset and recovery
These tissues are highly perfused and receive over 75% of the resting CO, and as a result have higher immediate concentrations of anesthetic
Brain, heart, liver, kidneys, and splanchnic bed
Inhaled anesthetics that are relatively insoluble in the blood and brain are eliminated at __ rates compared to more soluble anesthetics
Faster
Clearance of inhaled anesthetics via ___ is the major route of eliminate from the body
The lungs
Although recovery may be rapid with more soluble agents following a short period of exposure, recovery is slow after prolonged administration of ___
Halothane or isoflurane
In regards to the stages of increasing depth of CNS depression, this stage is described by the pt experiencing analgesia without amnesia. Both analgesia and amnesia are produced at the end of this stage
Stage 1
In regards to the stages of increasing depth of CNS depression, this stage is described by the pt appearing delirious. Respiration is irregular in both volume and rate, retching and vomiting may occur if pt is stimulated, and regular breathing is established at the end of this stage
Stage 2
In regards to the stages of increasing depth of CNS depression, this stage is described by beginning with regular breathing and extending to complete cessation of spontaneous respiration (apnea)
Stage 3
In regards to the stages of increasing depth of CNS depression, this stage is described by including severe depression of the vasomotor center in the medulla as well as the resp center
Stage 4
In regards to the effects of inhaled volatile liquid anesthetics on the CV system:
___ can cause bradycardia
___ increase heart rate
Halothane
Desflurane and isoflurane
Depression of mucociliary function in the airway due to volatile anesthetics can result in ___
Pooling of mucus and post-op resp infx
What are some common side effects of inhaled anesthetics?
Common-nausea and vomiting
__ may cause hepatitis with or without previous exposure and develops 2-3 weeks after exposure
Halothane
Symptoms –> anorexia, nausea, myalgias, arthalgias, and rash, eosinophilia, hepatomegaly, and jaundice
Agents metabolized to products including fluoride ions (enflurance and sevoflurane) may cause ___
Renal toxicity
In combo with ___, inhaled volatile anesthetics may cause malignant hyperthermia, which consists of rapid onset tachycardia and HTN, severe muscle rigidity, rhabdomyolysis, hyperthermia, hyperK, and acid-base imbalance with acidosis. What is the antidote to this?
Succinylcholine
Dantrolene is the antidote
__ are widely used to facilitate rapid induction of anesthesia and have replaced inhalation as the preferred method of anesthesia induction in most settings
Nonopioid IV anesthetics
__ anesthetics are highly lipophilic and preferentially partition into highly perfused lipophilic tissues (brain and SC), which accounts for their quick onset of action
IV
__ is the most commonly used parenteral anesthetic in the US. Its PK properties allow for continuous infusions and maintenance of anesthesia, sedation in the ICU, conscious sedation and short-duration general anesthesia in locations outside the OR
Propofol
What is the MOA of Propofol?
Most likely targets GABAa receptors as an agonist and potentiates the Cl current
Describe the pharmacokinetics of propofol:
- Rapidly metabolized in the liver
- Low hangover effect (high plasma clearance)
- rapid rate of onset, rapid recovery, pts can ambulate quickly after use
- time of onset is 15-30 secs
Describe some CNS effects with propofol
- no analgesic properties
- decreases cerebral blood flow which decreases ICP and intraocular pressure
- burst suppression in EEG when administered in large doses –> neuroprotective effect during neurosurg procedures
Describe CV effects with propofol:
Pronounced decrease in systemic BP due to profound vasodilation
Hypotensive effects augmented by inhibition of normal baroreflex response
List respiratory effects of propofol
- potent resp depressant
- greater reduction in upper airway reflexes than thiopental does
__ is a water-soluble prodrug of propofol that is rapidly metabolized by alkaline phosphatase. Its onset and recovery are prolonged (compared to propofol) because the prodrug must first be converted into an active form
Fospropofol
What are some common adverse effects with administration of Fospropofol?
Common adverse effect is the experience of parasthesias and pruritis are mostly limited to the first 5 minutes of admin and usually described as mild-moderate in intensity (unknown mechanism)
__ has hypnotic but no analgesic effects. Its MOA enhances the actions of GABA on GABAa receptors. It causes minimal CV and resp depression and useful in pts with impaired CV and pulm systems. It produces rapid loss of consciousness and less rapid recovery rate compared to propofol. It is extensively metabolized by the liver and in the plasma
Etomidate
What are CNS effects of Etomidate?
Potent cerebral vasoconstrictor; decreases cerebral blood flow and ICP
What are some CV effects of Etomidate?
CV stability is maintained even after bolus injection; minimal change in HR and CO
What are endocrine effects with Etomidate?
- causes adrenocortical suppression by producing a dose dependent inhibition of 11 B-hydroxylase
- suppression lasts 4-8 hrs after induction dose
- endocrine adverse effects limit use for continuous infusion
___ is an NMDA receptor antagonist and produces a dissociative anesthetic state characterized by catatonia, amnesia, and analgesia with or without loss of consciousness (pts eyes remain open with a slow nystagmic gaze). Similar in structure to PCP
Ketamine
Lacrimation and salivation are increased upon administration and premedication with an anticholinergic may be indicated
What is a CNS contraindication for ketamine?
Not recommended for use in pts with intracranial pathology, especially increased ICP
Ketamine increases cerebral blood flow as well as CMRO2
___ is an a-2 adrenergic agonist that produces hypnosis presumably from stimulation of a-2 receptors in the locus ceruleus and analgesic effects at the level of the SC. Its sedative effect more completely resembles a physiologic sleep state through activation of endogenous sleep pathways
Dexmedetomidine
___ is principally used for short-term sedation of intubated and ventilated pts in an ICU setting or as an adjunct to general anesthesia
Dexmedetomidine
What are some common opioid analgesics? What are their MOA?
Fentanyl, sufentanil, remifentanil, and morphine
MOA: agonists at opioid receptors
List some barbiturate anesthetic adjuncts:
Thiopental (prototype) and Methohexital
__ are anesthetic adjuncts that are highly lipophilic and quick plasma:brain equilibrium. It causes dose-dependent CNS depression ranging from sedation to general anesthesia (no analgesia) and causes respiratory depression
Barbiturates
What is the MOA of barbiturates?
Acts on the GABAa receptor to increase duration of channel opening (agonist) and enhances inhibitory neurotransmission
This barbiturate may be preferred over thiopental for short ambulatory procedures due to is rapid elimination
Methohexital
List some common benzodiazepine anesthetic adjuncts
Diazepam, lorazepam, and midazolam
This anesthetic adjunct is commonly used in the perioperative period because of their anxiolytic properties and ability to produce anterograde amnesia; actions can be terminated by the antagonist flumazenil
Benzodiazepines
This benzodiazepine anesthetic adjunct is frequently administered IV before pts enter the OR because it has a more rapid onset, shorter elimination 1/2 life (2-4 hrs), and steeper dose-response curve than other benzodiazepines
Midazolam
This anesthetic adjunct has potent anticonvulsant properties; used in tx of status epilepticus, alcohol withdrawal, and local anesthetic-induced seizures
Benzodiazepines
Monitored anesthesia care is performed without general anesthesia. It typically involves the use of __ for premedication (to provide anxiolysis, amnesia, and mild sedation), followed by a __ infusion (to provide moderate to deep levels of sedation). A potent ___ may be added to minimize the discomfort associated with the injection of local anesthesia and surgical manipulations
Midazolam
Titrated propofol
Opiod analgesic or ketamine
