Inhaled anesthetics Flashcards
What are the side effect of N2O?
Postop N/V
Inhibits B12-dependent enzymes –> pernicious anemia and CI in pregnancy
Pulmonary HTN
Second gas effect
What are the effects of N2O?
Does NOT drop BP Minimal changes in CV No change in minute ventilation Increased ICP, CBF and O2 consumption of brain Decreased renal/hepatic flow Increase SNS Analgesia
What is the MAC of N2O?
105%
When is N2O contraindicated?
Air embolus, Intracranial air, pulm. HTN, pregnancy, pneumothorax, GI obstruction
Of the 4 main inhaled anesthetics, which one is analgesic?
N2O
What is the MAC of Isoflurane?
1.2
Which inhaled anesthetic has the lowest blood/gas and fat/gas ratio?
Desflurane
What are the 3 volatile inhaled anesthetics?
Desflurane, isoflurane, sevoflurane
What two inhaled anesthetics are not irritants to the airway?
N2O and Sevoflurane
What do all 3 volatile inhaled anesthetics do to the HR and BP?
Drop the BP
Increase the HR
Which inhaled anesthetic has the fastest induction and emergence?
desflurane because has low solubility
Why are isoflurane and desflurane only used for maintenance?
Because they are irritants to the airway and may cause cough or laryngospasm
Which inhaled anesthetic is associated with carbon monoxide poisioning?
Desflurane
Which inhaled anesthetic is associated with the accumulation of vinyl compound A?
Sevoflurane - compound A is renal toxic
What are the effects of isoflurane on CV?
decreased SVR
Increased HR
May cause coronary steal syndrome if rapid increase (increase HR and BP)
What are the pulmonary effects of isoflurane?
Rapid shallow breaths that cause a decrease in minute ventilation
Increase partial pressure of CO2
Normal response to hypoxia and hypercarbia is abolished
What are the cerebral effects of isoflurane?
Increased CBF and ICP
What are the renal effects of isoflurane?
Decreased RBF
What are the CV effects of desflurane?
Decreased BP/SVR
Increased HR
Rapid increase –> release of catecholamines
What are the pulmonary effects of desflurane?
Rapid shallow breaths that cause a decrease in minute ventilation
Increase partial pressure of CO2
Irritant to upper airway
What are the cerebral effects of desflurane?
Increased CBF and ICP
What inhaled anesthetic is the most lipid soluble?
Methoxyflurane
What inhaled anesthetic is responsible for causing vasopressin-resistant high output renal failure?
methoxyflurane with metabolite fluoride
Which inhaled anesthetic causes no change in SVR?
Halothane
What are the CV effects of sevoflurane?
Slight decrease in myocardial contractility, BP, and SVR so slight decrease in CO because no increase in HR.
What are the pulmonary effects of sevoflurane?
Potent bronchodilator
Rapid shallow breaths that cause a decrease in minute ventilation
Increase partial pressure of CO2
What are the renal effects of sevo?
Reduces RBF proportionate to decrease in BP
What are the CV effects of Halothane?
direct myocardial depressant
depresses baroreflex receptors so no reflex tachy
CO increases
sensitizes heart to catecholamines
What are the pulmonary effects of halothane?
Potent bronchodilator (inhibits release of intracellular calcium)
Rapid shallow breaths that cause a decrease in minute ventilation
Increase partial pressure of CO2
What are the CV effects of methoxyflurane?
HR rises
CO decreases
Decreased cardiac contractility
What are the CV effects of enflurane?
Direct myocardial depressant
Decreased SVR
CO drops significant
What are the cerebral effects of enflurane?
Deep anesthesia level and hypocapnia cause EEG changes from high voltage, high frequecy to spike-and-wave pattern, then epileptic form.
What is the MOA of thiopental, phenobarbital, thiamylal, and methohexital?
Inhibits presynaptic excitatory NTs
Increases postsynaptic sensitivity to GABA
Stimulates GABA receptors
Chloride channels open longer
Why are lower induction doses required for the elderly?
- Decreased binding protein
- Decreased volume of central compartmen
- Decreased hepatic blood flow
Which agents can potentiate the effects of barbs?
BZDs, narcotics, EtOH, H1 blockers
What is the MOA of BZDs?
Increased frequency of Chloride channels opening
Facilitates GABA binding
Which BZDs are well absorbed from the GI tract?
Diazepam and lorazepam
Which BZDs are well absorbed via the IM route?
Midazolam and lorazepam
What is a possible side effect of a barb?
Acute intermitent porphyria by induction of aminolevulinic acid synthetase
What are the cerebral effects of barbs?
Depression of central vasomotor center in the brain Vasoconstriction Decreased CBF and ICP Decreased O2 consumption Protection against global ischemia
What are the CV effects of barbs?
vasodilation and increased HR
What are the pulmonary effects of barbs?
Decreased tidal volume and minute ventilation
Blunted response to hypoxia and hypercapnia
The release of what is associated with morphine and meperidine?
histamine
What are the pulmonary effects of opioids?
Increase PCO2
Blunted response to hypercapnia
Chest wall rigidity
What are the CV effects of ketamine?
Increased BP, SVR, HR and CO due to increase SNS
What are the pulmonary effects of ketamine?
potent bronchodilator Increased secretions (prevent with glycopyrrolate)
What are the cerebral effects of ketamine?
Increased O2 consumption, CBF and ICP
What are some side effects of ketamine?
dissociation
analgesia
nystagmus
Ileus/constipation
What are the side effects of etomidate?
Inhibition of B-11 hydroxylase and adrenocortical suppression
myoclonus
seizures
What is unique about etomidate?
little change on the heart. It is the DOC when CV stability is in question
What is the CV effects of propofol?
Myocardial depression
Vasodilation
What are the benefits of propofol?
Rapid Induction and emergence
Antipruritic and antiemetic
How are BZDs metabolized?
By the liver into water soluble glucoronides
What is the MOA of ketamine?
NMDA receptor antagonist
Causes dissociation of the thalamus from the cerebrum
What does ketamine do to CO?
Increases CO
What is the MOA of etomidate?
Depresses the RAS by enhancing GABA affinity for its receptor.
What is the MOA of propofol?
modulates GABA receptors