Spring 25 - Basics - Pharmacology of Anesthesia Flashcards
Primary effects of Dex.
- sedation
- analgesia
- anxiolysis
- reduced postoperative shivering and agitation
- cardiovascular sympatholytic actions
Precedex onset/duration
- Onset 10 - 20 minutes
- Duration 10 - 30 minutes
Precedex loading dose/gtt
- ld =1 mcg/kg over 10 minutes
- gtt = 0.2 to 0.7 mcg/kg/hour
Dex. main side effects
- Bradycardia
- hypotension
Etomidate MOA
- Hypnotic
- GABA receptor modulator
Etomidate induction dose
- 0.3 mg/kg
Etomidate duration/Half-life
- Duration 5 - 15 minutes
- half-life is 2 - 5 hours
Etomidate adverse effect
- Nausea / Vomiting
- Burn on injection
- Thrombophlebitis
Etomidate Contraindications
- Porphyria
- Adrenal suppression
- Known sensitivity to Etomidate
Key points of etomidate
- Minimal cardiorespiratory depression
- Reduced ICP
- Myoclonia on induction
Ketamine MOA
- NMDA receptors antagonist
- Blocks signals of pain perception to the thalamus and cortex
Ketamine CNS effects
- Increases ICP/CBF/CMRO
- Dissociative state of anesthesia
- Vivid illusions and confusional disturbances on emmergence
Ketamine CV effects
- Increases BP/HR
- Increased cardiac contractility CO/CVP
Ketamine Respiratory effects
- minor and short-lived.
- Ventilation is generally preserved,
- Bronchodilation
Ketamine induction dosage IV/IM
- 2-4 mg/kg IV
- 4-6 mg/kg IM
Ketamine maintenance dose
- 15 - 45 mcg/kg/min
- 0.5 - 1 mg/kg
Ketamine sedation and analgesia dose
- 0.2 - 0.8 mg/kg
- 5 - 20 mcg/kg/min
Ketamine key points
- Dissociative anesthesia
- Increased ICP and IOP
- Emergence delirium
- Releases catecholamines
- Moderate analgesic property
Propofol induction/maintenance/sedation doses
- Induction 1-2 mg/kg
- Maintenance 100-200 mcg/kg/min
- Sedation 25-75 mcg/kg/min.
Propofol systemic effects
- Rapid (10 - 50 secs) onset
- Reduces ICP, IOP and CMRO
- Decreased BP, CO and SVR
- Respiratory depression/apnea
- Mild anti-emetic properties
Midazolam uses
- Anxiolysis
- Anesthesia (at high doses)
- Amnesia
- Anticonvulsant
- Muscle-relaxing properties.
Midazolam systemic effects
- Anterograde amnesia
- Minimal CV effects
- Most respiratory depressive benzo
Flumazenil onset and duration
- Onset 1 - 2 minutes
- Duration 45 - 90 minutes
What receptors are targeted by opioids?
- Mu
- Delta
Both are located in the respiratory center in the brainstem
Morphine order of action (Sedation vs analgesia)
- Sedation first, followed by analgesia.
- Induced sedation should not be considered an indicator of appropriate analgesia.
Morphine metabolism occurs in
Liver
Morphine Dose / Onset / Peak /Duration
- IV 0.05 - 0.15 mg/kg
- Onset 20 min
- Peak 30 - 60 minutes
- Duration 4 - 5 hours
Fentanyl duration
20 - 40 minutes
Fentanyl metabolism/elimination
- first-pass uptake in the lungs
- Termination of action reflects elimination and
not redistribution (when given as gtt) - elimination is prolonged in the elderly and neonates.
- Eliminated in the urine and bile
Alfentanil metabolism
- Metabolized in the liver by oxidative N-dealkylation and O-demethylation in the cytochrome P-450 system.
- The inactive metabolites are excreted in the urine
Alfentanil notable drug interation
Erythromycin has been shown to prolong the metabolism of Alfentanil
Hydromorphone Dose/Onset/Peak/Duration
- 0.01 - 0.02 mg/kg
- Onset 15 - 30 minutes
- Peak 30 - 90 minutes
- Duration 4 - 5 hours
Meperidine key points
- Same structural and antispasmodic effects as atropine
- Effective in reducing shivering as precedex
- Accumulation can lead to CNS excitation and seizures
Remifentanil key points
- rapid onset,
- ultrashort duration,
- titratability
- simple metabolism
Remifentanil elimination 1/2 life
8 - 20 minutes
Morphine Dose
Hydromorphone (Diluadid) Doses
Fentanyl Doses
Sufentanil Dose
Alfentanil Doses
Remifentanil Doses
Buprenorphine key points
- Partial agonist opioid that binds to mu receptor
- Duration about 8 hrs due to slow dissociation from receptor
- Ceiling effect does not increase respiratory depression
- Minimal effect on GI motility
- USED in opioid use disorder treatment
Butorphanol key points
- Highly lipophilic
- Kappa agonist / Weak mu antagonist
- More analgesia than morphine but has a ceiling effect (less respiratory depression)
- USED for post-op pain and the treatment of migraines
Nalbuphine key points
- Both agonist (kappa) and antagonist (mu) of opioid receptor
- Equal analgesia as morphine
- Ceiling effect but difficulty reversal with naloxone
- USED antagonizing pruritus and respiratory depression induced by other opioids.
Which highly lipophilic opioid Can produce more analgesia than morphine but has a ceiling effect below that of mu-agonist
Butorphanol’s
Partial Agonists and Agonists-Antagonists
- Receptor affinity
- Buprenorphine = High affinity for mu receptors
- Butorphanol = Angonist at kappa and weak antagonist at mu receptors
- Nalbuphine = Agonist effect at kappa and antagonist effect at mu receptors.
Partial Agonists and Agonists-Antagonists
- Clinical uses
- Buprenorphine = opioid use disorder treatment and for cancer pain
- Butorphanol for migraine and postoperative pain
- Nalbuphine for antagonizing pruritus and respiratory depression induced by other opioids
Naloxone key points
- Pure opioid antagonist
- Competitive antagonism at mu, kappa,
and delta receptors - Duration is less than other (possible return of respiratory depression)
- Reverse the side effects of epidural opioids while preserving some analgesic effects
Naltrexone key points
- Same receptor binding capabilities as naloxone but higher oral efficacy and lasts longer
- USED in ETOH use disorder and for patients addicted to opioids to prevent the euphoric effects of opioids
Nalmefene key points
- Structurally similar to naloxone but longer acting parenteral
- 1/2 life about 10 hours
- Duration 8 hours
- USED in alcohol use disorder programs. In acute opioid overdose
- Dose 0.5 - 1.6 mg IV
Narcotic Antagonists
- Duration of Action
Naloxone has the shortest duration of action, while Naltrexone and Nalmefene have longer durations, making them suitable for longer-term management of opioid addiction or overdose
Narcotic Antagonists
- Use in addiction
Naltrexone and Nalmefene are used in alcohol use disorder programs, whereas Naloxone is primarily used for the emergency treatment of opioid overdose
Narcotic Antagonists
- Metabolic pathway
Naltrexone produces an active metabolite, contributing to its longer duration of action,
while Nalmefene’s longer action is due to its inherent pharmacokinetic properties.
Ketorolac key points/contraindication
- IV NSAID
- Can be administered IV & IM
- No CV and GI dysfunction
- CONTRAINDICATION (Atopic/asthmatic patients/elderly/renal or GI dysfunction, or
bleeding disorders)
Ibuprofen key points dosage / Onset / Duration
- Similar effects to Ketorolac
- Analgesic and antipyretic
- Dosage 400 - 800 mg (IV Over 30 min)
- Onset 30 minutes
- Duration 4 - 6 hours
Acetaminophen (Not-Nsaid) key points
- Analgesic and antipyretic
- Adult > 13 yo dose 1000 mg (IV over 15 minutes)
- Child <13 dose 15 mg/kg
- Max daily dose 4000 mg
Non-Narcotic Analgesics
- Mechanism of action
Both Ketorolac and Ibuprofen are NSAIDs and work by inhibiting cyclooxygenase enzymes, whereas Acetaminophen’s mechanism is less clear but is believed to involve central inhibition of prostaglandin synthesis.
Non-Narcotic Analgesics
- Analgesic properties
- Ketorolac and Ibuprofen are effective for mild to moderate pain
- Acetaminophen is used for mild pain and fever
Non-Narcotic Analgesics
- Side effects
- Ketorolac and Ibuprofen can have GI and CV side effects
- Acetaminophen can cause hepatotoxicity at high doses.
Relationship between gas uptake in the blood and alveolar concentration
The greater the uptake, the slower the rate of rise of the alveolar concentration and the lower the FA: FI ratio
Relationship between agent solubility and uptake (in the blood)
- Insoluble agents like nitrous oxide are taken up less
avidly by the blood. - More soluble agents like sevoflurane uptake is faster than non-soluble agents
Relationship between cardiac output, alveolar partial pressure and uptake
- An increase in cardiac output increases anesthetic uptake, slowing the rise in alveolar partial pressure
and delaying induction - Low-output states can lead to overdosage with
soluble agents.
Relationship between partial pressure differences and agent uptake
The gradient between alveolar gas and venous blood, which depends on tissue uptake, also affects the uptake of anesthetic by the pulmonary circulation.
Reason for discrepancy (Missmatch) between alveolar and arterial anesthetic partial
- Venous admixture
-Alveolar dead space - Nonuniform alveolar gas distribution
What are the alveolar and arterial consequences of a mismatch between alveolar and arterial partial pressures?
- Increase in alveolar partial pressure (especially for highly soluble agents)
- Decrease in arterial partial pressure (especially for poorly soluble agents)
Relationship between inspired concentration and alveolar concentration
Increasing the inspired concentration not only
increases the alveolar concentration but also its rate of rise.
Factors that speed up induction and accelerate recovery
- Elimination of rebreathing,
- High fresh gas flows
- Low anesthetic-circuit volume
- Low absorption by the anesthetic circuit
- Decreased solubility
- High cerebral blood flow,
- Increased ventilation.
Diffusion Hypoxia
- Rapid Elimination of Nitrous Oxide
Nitrous oxide is quickly eliminated from the body through the alveolar membrane. This rapid elimination is one factor that speeds up recovery from anesthesia.
Diffusion Hypoxia
- Dilution of Oxygen and Carbon Dioxide
Due to the rapid exhalation of nitrous oxide, the oxygen (O2) and carbon dioxide (CO2) concentrations in the alveolar gas are diluted. This can lead to a relative state of hypoxia.
Diffusion Hypoxia
- Prevention of Diffusion Hypoxia:
To prevent diffusion hypoxia, it is recommended to administer 100% oxygen for 5 to 10 minutes after discontinuing nitrous oxide. This practice helps to maintain adequate oxygen levels in the alveoli and bloodstream, countering the dilution effect caused by the rapid exit of nitrous oxide.
Nitrous oxide key points
- NMDA antagonist
- CV stimulant (Mask respiratory depression
- Respiratory rate increased and decrease tidal volume
- Depress hypoxic drive
- Increased cerebral blood flow and ICP (Mildly)
- No muscle relaxation
- Decreased kidney and hepatic blood flow
- PONV
How is Nitrous oxide Eliminated? and contraindications
- Primarily eliminated by exhalation
- Small amount diffusing through the skin
-CONTRAINDICATED in conditions where rapid diffusion into air-containing cavities can be hazardous, such as pneumothorax, bowel distention, or intracranial air.
Definition of MAC
The alveolar concentration of an inhaled anesthetic that prevents movement in 50% of patients in response to a standardized stimulus, such as a surgical incision
Utility of MAC
- It reflects the partial pressure of the anesthetic in the brain
- Allows for comparisons of potency between different anesthetic agents
- Serves as a standard for experimental evaluation
Explain the Additivity of MAC Values
A mixture of 0.5 MAC of nitrous oxide and 0.5 MAC of isoflurane produces a similar effect in suppressing movement in response to surgical incision as 1.0 MAC of isoflurane alone.
MAC Value ISO
Alone - 1.17
+ N2O - 0.56
MAC Value Sevo
Alone - 2
+ N2O - 0.66
MAC Value Des
Alone - 6
+ N2O - 2.38
MAC Value Nitrous
104
What is the effect of the 3 Main Gases
- On the cardiovascular system?
All three anesthetics have similar effects on the
cardiovascular system, primarily causing a decrease in systemic vascular resistance and arterial blood pressure.
Which of the 3 Main Gases
- Causes airway irritation?
Desflurane is an airway irritant.
What is the effect of the 3 Main Gases
- on the Brain?
All increase CBF and intracranial pressure, with sevoflurane and desflurane having similar effects on CBF autoregulation.
Which of the 3 Main Gases
- Decrease peripheral nerve stimulation
Desflurane
Which of the 3 Main Gases
- Has minimal nephrotoxic effects
Desflurane
Which of the 3 Main Gases
- Has the highest rate of metabolism?
Sevoflurane has a higher rate of metabolism with potential nephrotoxic byproducts
All three leading gases potentiate which class of meds?
All three anesthetics share similar contraindications and potentiate NMBAs.
Progressive Disappearance of Twitches TOF
- If T4 disappears (3 twitches) → 75% to 80% neuromuscular blockade
- If T4 and T3 disappear (2 twitches) → 80% to 85% neuromuscular blockade
- If T4, T3, and T2 disappear (1 twitche) → 90% to 95% neuromuscular blockade
- If no twitches are seen (0 twitches) → 100% paralysis (complete neuromuscular blockade)
Timing for Reversal of NMBA using TOF
- 1 response to TOF = 30 minutes.
- 2 to 3 responses = 4 to 15 minutes
- 4 responses to TOF recovery can be achieved within 5 minutes of reversal with neostigmine or 2 to 3 minutes after using edrophonium.
Succinylcholine MOA
- Competitive agonist at nicotinic acetylcholine (nACh) receptors, causes depolarization without repolarization.
Succinylcholine onset/half-life/duration/full recovery time
- onset 30 - 60 secs
- 1/2 life 2 - 4 minutes
- duration 5 - 10 minutes
- full recovery 12 - 15 minutes
Succinylcholine dose
- 0.5 to 1.5 mg/kg
- ED95 is approximately 0.30 mg/kg
Succinylcholine metabolism
Plasma cholinesterase produced in the liver.
Liver damage may prolong the effects of the drug
Succinylcholine absolute contraindication
- Patients with known or suspected MH or who have MH in their families
- Indirect increase in ICP
- Only in emergency for children under 8 years old
Explain Phase I (intended) block
Succinylcholine initially acts by mimicking (ACh) at the neuromuscular junction, leading to depolarization. The muscle is depolarized and cannot be repolarized immediately, leading to paralysis.
Explain Phase II block
With prolonged exposure to high doses or repeated dosing, the muscle membrane starts repolarizing but becomes less responsive to acetylcholine. This transition is what characterizes the Phase II block
Treatment of phase II block
If a Phase II block is identified, it can often be treated with anticholinesterase drugs, similar to the treatment of a block induced by nondepolarizing NMBAs
Rocuronium Bromide MOA
Competitive antagonist at nicotinic acetylcholine (nACh) receptors
Rocuronium onset/duration/half-life(elimination)
- Onset is dose dependant
- duration 30 - 60 minutes
- Elimination 1/2 life 60 - 120 minutes
Rocuronium intubation dose and onset
- 2nd most used RSI (after Succs)
- 0.6 - 1.2 mg/kg
- onset 45 - 90 seconds
Rocuronium key points
- Cardioprotective
- Duration of action is prolonged in patients with hepatic disease
- Prolonged elimination half-life in patients with renal disease.
Rocuronium elimination 1/2 life children/adults/elderly
- Children 38.3 minutes
- Normal adults 56 minutes
- Elderly 137 minutes
Vecuronium Bromide MOA
Competitive antagonist at nicotinic acetylcholine (nACh) receptors
Vecuronium dose/onset/duration
- Dose 0.1 mg/kg
- Onset 3 minutes
- Duration 3 - 45 minutes
Vecuronium elimination/metabolism
- Eliminated via hepatic and renal mechanisms
- The duration of action is prolonged in patients with decreases in renal and liver function
Cisatracurium MOA
Competitive antagonist at nicotinic acetylcholine (nACh) receptors
Cisatracurium dose/half-life
- Dose 0.1mg/kg
- Half-life 26 to 36 minutes
Cisatracurium key points
- Maintains cardiovascular stability and does not cause histamine release
- Suitable choice for patients with renal or hepatic impairment
- The kinetics of cisatracurium are not significantly changed in elderly patients.
- Preferred in obese patients due to its lack of
histamine release and reliable kinetics.
Atracurium MOA
Competitive antagonist at nicotinic acetylcholine (nACh) receptors
Atracurium dose/onset/duration
ED95 0.10 - 0.25 mg/kg
onset 1.2 - 2.8 minutes
duration 30 - 60 minutes
Atracurium key points
- Undergoes Hofmann elimination
- Safe to use in patients with liver and kidney diseases
- Can cause histamine release and may lead to hypotension and tachycardia
Cholinesterase inhibitors MOA
- Edrophonium
A reversible inhibitor of cholinesterase
Cholinesterase inhibitors MOA
- Neostigmine
Degrades ACh-cholinesterase complex, leaving AChE unable to hydrolyze ACh
Edrophonium vs. Neostigmine Pharmacokinetic Profiles
Edrophonium binds reversibly with the negatively charged enzyme site, while neostigmine forms a more stable enzyme
Neostigmine dose/onset/duration
- 25-75 mcg/kg
- Onset of 5-15 minutes
- Duration 45-90 minutes
Sugammadex 3 doses
- 2 mg/kg for patient with 2 or more twitches, spontaneous recovery
- 4 mg/kg for 1 -2 PTC and no response to TOF
- 16 mg/kg to reverse NMB soon after administration of a single dose of 1.2 mg/kg of rocuronium
Sugammadex common reactions
- Nausea/vomiting
- Allergy, hypertension, and headache
- Anaphylaxis
Sugammadex and oral contraception
Binds oral contraceptives, and women of childbearing age should be counseled about using alternative contraceptive methods for 1 week after exposure to sugammadex
Two most used anticholinergics
Atropine and Glycopyrolate
Specific Anticholinergic Agents
- Atropine + Edrophonium: Dose
Atropine + edrophonium give 7 mcg/kg.
Specific Anticholinergic Agents
- Glycopyrrolate: Dose/benefit(s) over atropine
- Dose10 - 20 mcg/kg
- Less initial tachycardia, no CNS effects
Neostigmine Dose/Onset (min)/Duration
Edrophonium Dose/Onset (min)/Duration
Atropine Dose/Onset (min)/Duration
Glycopyrrolate Dose/Onset (min)/Duration
Sugammadex Dose/Onset (min)/Duration
Ephedrine MOA
- sympathomimetic
- Stimulates alpha and beta receptors
- Effects similar to epinephrine but moderate, no hyperglycemia
- longer duration of action than epinephrine
Ephedrine dose/onset/duration
- Dose 5 to 25 mg,
- Onset immediate
- Duration 15 - 90 minutes
Ephedrine caution
Patient with questionable coronary perfusion it can increase myocardiac oxygen requirement
Phenylephrine MOA
- Purely Alpha, no beta stimulation
- Sharp rise in blood pressure
Phenylephrine onset/duration
- Onset immediate
- Duration 5 - 20 minutes
Phenylephrine other clinical uses
You can stick it in
- Eyes (Mydriatic)
- Ears
- Nose (prevent/reduce bleeding)
- Throat (reduce bleeding during ENT sx)
Esmolol loading dose/infusion/boluses
- Loading 500 mcg/kg
- Infusion 100 - 300 mcg/kg/min
- boluses 10 - 20 mg
Esmolol onset/half-life/duration
- onset 2 minutes
- 1/2 life 9 minutes
- duration 10 - 15 minutes
Metoprolol MOA
Beta-blocking effects, which include negative chronotropic, dromotropic, inotropic,
antiarrhythmic, and antiischemic actions
Metoprolol doses
- IV 5-mg Q5 minute maximum dose of 15 mg.
- po 50 - 200 mg daily
- po XL 25 - 400 daily
Labetalol MOA
- Nonselective beta-blocker but is unique in that it
- Also possesses an alpha-blocking component
- 7:1 beta to alpha-blockade ratio.
Labetalol dose bolus/gtt/duration
- Bolus 0.25 mg/kg,
- gtt 2 mg/min
- Duration 2 - 6 hours
Anticholinergics
- Atropine summary
- Antisialagogue effects,
- Prevention or treatment of bradycardia
- Used in conjunction with Edrophonium
- HR increase dose 0.4 to 0.6 mg onset 1 - 2 minutes
Anticholinergics
- Scopolamine
- Bella Dona alkaloid
- Periop used for sedation, amnesia and PONV
- 1.5 mg patch applied behind the ear 4 hours pre-op and last up to 3 days post-po
Anticholinergics
- Glycopyrrolate
- Most antisialagogue effect
- Use in conjunction with Neostigmine
- Prevents Bradycardia without creating tachycardia
Cefazolin MOA
a β-lactam antibiotic works primarily via time-dependent killing
Cefazolin dose
Adults 2g IV (Q4 hours for longer procedures)
Antiemetics
- Dexamethasone (Decadron) Dose/ Duration
- Dose 4 or 8 mg
- Duration 72 hours
Antiemetics
- Methylprednisolone (Solu-Medrol) Dose
40 mg prophylactic treatment
Antiemetics
- Ondansetron dose/duration
- Dose 4mg IV (at the end of the case)
- Duration 4 - 6 hours
Antiemetics
- Droperidol dose/contraindication
- 0.625 to 1.25 mg IV
- Parkinson Disease
CAUSE QT prolongation
Antiemetics
- Haloperidol dose
1 - 2 mg
SAME QT effect as. Droperidol
Antiemetics
- Midazolam:
Recent studies suggest a significant antiemetic effect. Decreases dopamine’s emetic effect in the chemoreceptor trigger zone and decreases serotonin release by binding to the GABA receptor complex
USE MAY DELAY RECOVERY DUH!!
Antiemetics
- Metoclopramide dose/half-life
- Dose 20 mg
- half-life 30 - 45 minutes (Weak one)
DO NOT GIVE IN PARKINSON’S disease