Pharm 36 Objectives Flashcards
What are the halogenated inhaled agents?
- Desflurane
- Isoflurane
- Sevoflurane (preferred)
- Halothane
What are the non-halogenated inhaled agents?
Nitrous oxide
What is the PK of the halogenated inhaled agents?
- Absorbed through the lungs into the blood
- Rate of absorption determined primarily by regional blood flow.
- Distributed rapidly to the brain
- Primarily excreted to the brain
What is the PK of the non-halogenated inhaled agent (nitrous oxide)?
- Rapid induction and recovery
- Less able to induce full LOC
- No dose dependent effect on B/P and respiration
What is the MOA of halogenated inhaled agents?
- Potentiates GABA at the GABA-A receptor
- Opening of the chloride channel –> hyperpolarization of the neuron
- Enhances the inhibitory effects of GABA
- Depresses transmission at excitatory synapse
What is the MOA of parental agents?
Promotes release of GABA and major inhibitory neurotransmitter in the brain
What is the chemical advantage that correlates with easier administration when a phosphate group is added to the chemical structure of phenytoin or propofol –> fosphenytoin and fospropofol?
- More water soluble and may produce less injection site pain
- Dyslipidemia w/ prolonged infusion
- Less chance for bacteremia
Define the “MAC” and how it correlates to potency for inhalational anesthetics.
- Minimum alveolar concentration
- Measures the alveolar air that will produce immobility of 50% of pts exposed to painful stimulus
How does nitrous oxide relieve pain, induce loss of consciousness, and suppress respiratory function and blood pressure?
- Low anesthetic potency (no LOC)
- High analgesic/pain relief
- No suppression on respiratory function and blood pressure
What are two potential advantages of adding nitrous oxide to other inhalation anesthetic agents for general anesthesia?
Enhance analgesia effect and “push” other agent —>CNS
What is the primary role of nitrous oxide?
Provide pain relief for a dental and minor surgeries where patient does not need to be unconscious.
What are the inhaled risks and toxicities?
- Airway irritation
- Potential for aspiration of gastric contents
- Respiratory and cardiac depression: HypoTN, cardiac arrhythmias, sensitization of the heart to catecholamines.
- Malignant hyperthermia
- Hepatotoxicity
What are the risks and toxicities associated with IV Propofol?
- CNS depression- respiratory depression
- Apnea
- HypoTN
- Infection
- Transient pain at injection site
- Metabolic acidosis
- Heart and kidney failure
- Rhabdomyolysis
- TMI
- Death
What are the risks and toxicities associated with IV Ketamine?
- ICP
- Increase HR
- HTN
- Muscle rigidity
- Flashbacks
- Paranoia/dissociation
What is balanced anesthesia?
Using multiple drugs at lower dosages.
- This decreases the risk of toxicity seen at higher doses needed if using just one drug.
What is the roles of barbiturates as an adjunct to general anesthesia?
Rapid induction of anesthesia- LOC in 20 seconds
What is the roles of benzos as an adjunct to general anesthesia?
Promotes tranquility and reduce anxiety
What is the roles of opiods as an adjunct to general anesthesia?
Promote analgesia w/o affecting other senses (sight, touch, smell, hearing)
What is the roles of NM blockers as an adjunct to general anesthesia?
Reduce the amount of anesthesia needed and prevent contraction of skeletal muscles
What parenteral anesthetic is relatively contraindicated in the setting of head trauma and elevated intracranial pressure.
Ketamine
What are the Non-depolarizing NMB?
- Pancuronium
- Cisatracurium
- Rocuronium
- Vecuronium
What are the depolarizing NMB?
Succinylcholine
What is the MOA of the Non-depolarizing NMB?
- Competitive antagonist of acetylcholine at nicotinic receptors in skeletal muscles
- Do not cross the BBB and now well absorbed in the gut
- Do not cause fasciculations and their effects can be reversed by cholinesterase inhibitors
- Used in critically ill pts w/renal and hepatic failure
- Longer duration of action
What is the MOA of the depolarizing NMB?
- Binds to nicotine receptors in skeletal muscles and causes persistent depolarization of the motor end plate
- Produces muscle fasciculation followed by muscle paralysis effects cannot be reversed
- Used to produce muscle relaxation before and during surgery and to facilitate intubation of the airway
- Preferred for adults w/emergency surgery situations
- Short duration of action
What are 3 uses for neuromuscular blocking agents?
- Endotracheal intubation
- Mechanical ventilation
- Electroconvulsion therapy
(Surgical procedures requiring skeletal muscle relaxation)
What is the risks with NMB?
- Pts that only receive a NMB are paralyzed but can still feel pain and are conscious “anesthesia awareness”
- Cont. to administer other prescribed medication and opioids even though the pt appears unresponsive
- Apnea and HypoTN
What is the potentially fatal risk/COD with NMB?
Hypoxia or Malignant hyperthermia
How would you manage Malignant hypothermia?
- MH kit or crash cart in the operating room with adequate supply of dantrolene
- Dantrolene + sterile water repeat every 5 minutes
- Stop administration of triggering agent
- Hyperventilate w/ 100% oxygen
- Bicarb for metabolic acidosis
- Cooling measures: cold bottled fluids, cold IV bags, cold pack
What is the reversal agent for non-depolarizing NMBs-pancuronium and citacurium?
Neostigmine
What is the MOA of Neostigmine?
Increases acetylcholine levels at the neuromuscular junction and counteracts the neuromuscular blockade
(reverse neuromuscular blockade)
What is the reversal agent for non-depolarizing NMBs-rocuronium and vecuronium.?
Sugammadex
What is the MOA of Sugammadex?
- Modified gamma cyclodextrin compound that forms a tight inactive complex
- Fast recovery of neuromuscular function compared to neostigmine
Why is Neostigmine and Sugammadex not useful in reversing succinylcholine?
Because succinylcholine is irreversibly bound to the receptors
What is the etiology of Malignant hyperthermia?
A rare genetic disease triggered by inhaled anesthetic and NBMs (esp. succinylcholine) d/t presence of abnormal proteins in the muscle cells of the body
- Abnormal release of Ca+ from the SR occurs
What is the first sign of Malignant hypothermia?
Steady rise in ETCO2 output
What are other S/Sx of Malignant hypothermia?
- Elevation in temp 43 degree Celsius
- Difficulty intubating sustained muscle contractions
- Generalized rigidity
- Steady rise in HR
- Increased respiratory drive
- Vascular dysrhythmias- tachy and PVCs, hyperkalemia
What are late/severe S/Sxs of Malignant hypothermia?
- Shock
- Cardiac arrest
- Kidney failure
- Blood coagulation problems
- Internal hemorrhage
- Brain injury
- Liver failure
What drugs are associated with Malignant hypothermia?
- All anesthesia inhalations: Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane
- Depolarizing NMB: Succinylcholine
Room air oxygen is what %?
21%
2 liters nasal prongs of oxygen is what %?
28%
5 liters face mask oxygen is what %?
40%
5 liters face mask oxygen 2/ reservoir bag is what %?
60%
What IV anesthetic is used in children with septic shock?
Ketamine
Succinylcholine is primarily used for what procedures?
muscle relaxer for endotracheal intubation
- very brief duration so poorly suited for prolonged procedures
Pancuronium should be avoided in who?
- May tachy-avoid in high-risk cardiac pts
- Pts with kidney and liver disease
What is unique about Rocuronium?
- Aside from succinylcholine, it the fastest NMB with an onset in 1-3 minutes
- Persists for 20-40 minutes
Vecuronium has less effect on what?
Cardiovascular effects
Cisatracurium should be used in pt with what?
Kidney or liver dysfunction
IV etomidate is useful in pts with what?
- CVD (safe than barbiturates)
- rapid induction of anesthesia
ASE of IV Etomidate
Highly emetogenic
What are the indications for IV propofol?
- MC’ly used anesthetic
- considered an induction, maintenance general anesthesia
- Mechanical vent
- Radiation therapy
- Endoscopy, MRI, etc.
What is the MOA of Nitrous oxide?
Blocks the NMDA receptors
Desflurane is more irritating to what?
Respiratory tract
Isoflurane produces more what?
- Muscle relaxation, causing more respiratory depression
Why is Sevoflurane an ideal anesthetic?
- Rapid and smooth induction and recovery
- Little cardiovascular or other organ tox
Why is Halothane so dangerous and no longer used in the US?
- Risk for cardiac dysrhythmias
- Produce hepatitis and hypersensitivity rxn
