Inhaled Anesthetics Flashcards
Isoflurane (Furane)
- Inhaled General Anesthetic
- Halogenated Methyl Ethyl Ether
- Minimum Alveolar Concentration; 1.2
- Blood gas solubility; 1.4
- Vapor Pressure; 240 mmHg
- metabolized; 0.2 - 2%
Dose; MAC; 1.2 age 26 --> 1.28 age 44 --> 1.15 age 64 --> 1.05
used;
- induction and maintenance of GA,
- *pungent odor; less useful as induction agent
- rapid increase in concentration (such as over pressurizing during induction) can cause transient increase in HR and BP
MOA; Unknown but thought to be target proteins;
- presynaptic VGNa channel
- 2 pore potassium channels; TREK & TASK
- Inotropic & metabotropic; GABA & glycine (glycine major inhibitory NT in SC, thought to cause immobility in SC)
- Glutamate (NMDA, AMPA, Kainate)
Pharmacokinetics; Ventilation limited anesthetic VP 240 mmHg B/G; 1.4 [[high rate of uptake into the blood prevents alveolar partial pressure from rising rapidly]]
Metabolism; 0.2 - 2% metabolized
in liver by the CYP450 enzyme into trifluroacetic acid (risk of halothane hepatitis)
Vd for equilibration
- 2.1 minutes to vessel rich group
- 88 minuets to muscle group
- 2039 minutes to fat group
Elimination; by the lungs
0.17% taken up excreted in urine
Side Effects; CNS -Silent EEG @ 2 MAC -enhances CSF absorption -Increases CBF, ICP and decreases CMR02 @ 1 or >1 MAC -MUSCLE RELAXATION
CV
- myocardial depression (decrees SVR, BP and minimal increase in HR )
- rapid increase in concentration can cause transient increase in HR and BP
- Coronary Steal Syndrome; risk of cardiac ischemia in CAD pt
- coronary artery vasodilation
- activate KATP channels – hyper-polarizing effect; Hyperpolarize vessel and myocardium and if there is an ischemic event it will be less problematic
Resp
-increased RR decreased TV
-decrease in MV
decrease response to hypoxia and hypercarbia
-bronchodilation
-*respiratory irritant r/t odor in kids can lead to laryngospasm and coughing
-Reduces hypoxic pulmonary vasoconstriction at doses >1 MAC increasing the risk of hypoxia during one lung ventilation
GI
- N/V
- NO change in hepatic blood flow
GU
-decreased Renal BF, GFR and UOP
other;
Potentiates effects of NMBD
N20 decreases MAC of Iso
Can react with C02 scrubber and cause carbon monoxide leading to carboxyhemoglobin in pts
Contraindication;
hypersensitivity
MH
pregnancy (category C)
Sevoflurane
Inhaled General Anesthetic
Fluorinated Methyl Isopropyl Ether
MAC; 2%
VP; 160
B/G; 0.69
Metabolism; 2 - 5% *no risk of halothane hepatitis
*risk of compound A formation administer with at least 2L of FGF
Dose;
MAC; 2%
varies based on patient status, age, procedure, medications co-administered, Renal function
MOA; unknown but thought to be target proteins
- VGNa channels
- 2 pore potassium channels; TREK and TASK
- Inotropic and Metabotropic: GABA and Glycine (glycine is the major inhibitory NT in the SC and causes SC immobility)
- Glutamate; NMDA; AMPA; Kainate
Pharmacokinetics;
-B/G 0.69; rapid equilibrium between inspired and alveolar concentration (but not as fast as desflurane)
-rapidly taken up into the tissues
metabolism; 2 - 5% metabolized by the CYP450 enzymes in the liver; NO trifluoroacetic acid production
*NO risk of halothane hepatitis
Elimination; eliminated via exhalation by the lungs
- 5% excreted in urine as inorganic fluoride
* fluoride concentrations drop rapidly; renal toxicity not expected
Side Effects;
CNS;
-increases ICP, CBF and decreases CMR02
*best IA for neuro bc increases CBF the LEAST and decreases CMRO2 the MOST
-Muscle relaxant; potentiates effects of NMBD
-High rate of emergence delirium especially in pedi
-Seizures
CV;
- Dose related myocardial depression; Minimal/NO change in HR causing CO to drop more than other IA
- SVR and BP decrease
- NO SNS activity with increased concentrations
- activated K-ATP channels; hyper-polarizes vessel and myocardium protecting heart from ischemic events
- *hyperkalemia has occurred in pedi patients and caused arrhythmias and death
Resp;
- increased RR, decreased TV
- decreased MV
- decreased response to hypoxia and hypercarbia
- BRONCHODILATOR
- reduces hypoxic pulmonary vasoconstriction (HPV) increased risk of hypoxia with one lung ventilation
GI;
- N/V
- no change in hepatic blood flow
GU;
- decreased RBF, GFR, UOP
- potential risk for nephrotoxicity from compound A formation; administer Sevo with 2L FGF
- Sevo broken down into Free Fluoride ions; potential for acute renal failure; but no reports of renal toxicity r/t elevated fluoride ions
Contraindications;
-MH
Caution;
patients with hypotension, hypertension, elderly, obese and RENAL insufficiency
Desflurane
Inhaled General Anesthetic
Fluorinated Methyl Ethyl Ether
MAC; 6%
VP; 669
B/G; 0.42
Metabolism; 0.02%
*VP 3-4X higher than other IA; special vaporizer Tec6 is used to heat and pressurize gas
*risk of carbon monoxide poisoning with dried our sodalyme/baralyme scrubber
Dose;
MAC; 6%
varies based on patient status, age, procedure, medications co-administered
MOA; unknown but thought to be target proteins
- VGNa Channel
- 2 pore potassium channels; TREK and TASK
- Inotropic and Metabotropic; GABA and Glycine (glycine major inhibitory NT in SC and causes SC immobility)
- Glutamate; NMDA, AMPA, Kainate
Pharmacokinetics
-B/G 0.42; rapid equilibrium between inspired and alveolar concentration
- uptake in first minute; 146 mL
- metabolized 0.2% by liver CYP450 enzymes into trifluoracetic acid (very little risk of halothane hepatitis)
- rapid elimination via exhalation by lunges
Side Effects;
CNS;
-increases ICP, CBF decreases CMR02 (particularly at 1 MAC or greater)
-Muscle relaxation; potentiates effects of NMBD
-Emergence delirium in pedi population
CV;
- transient SNS activity (increased HR, BP) with rapid increase in inspired concentration
- after transient SNS activity; myocardial depression; decreased BP, SVR and increased HR (baroreflex)
- activates K-ATP channels; hyperpolarizes vessel and myocardium; protecting heart from ischemic event
Resp;
- increased RR decreased TV
- decreased MV
- decreased response to decreased 02 and increased C02
- pungent odor can cause breath holding, coughing, laryngospasm
- concentration used for induction (10%) can cause respiratory irritation; coughing and bronchospasm
- reduces HPV at > 1 MAC; increases risk of hypoxia with one lung ventilation
GI;
- N/V
- decreases hepatic blood flow
- transient increase in LFTs
GU;
-decrease RBF, GFR, UOP
other;
-biggest risk of carbon monoxide with degradation of Des in a dried C02 baralyme/ sodalyme scrubbier
Contraindicated;
- MH
- Inhalation induction in kids r/t laryngospasm
Caution;
asthmatics
CAD and MI r/t myocardial 02 demand and increase HR from rapid increase in concentration >6%
Nitrous Oxide (N20)
Inhaled Anesthetic MAC; 105 VP; 38,770 B/G; 0.47 metabolism; 0.004% odorless/ sweet smelling
Uses;
-used in combination with opioids and VA for GA
MOA is unknown, its is thought to be target proteins
- VGNa channel
- 2 pore K channels (TREK & TASK)
- Inotropic and metabotropic (glycine and GABA)
- Glutamate (NMDA, AMPA, Kainate)
Pharmacokinetics;
-B/G; 0.47
alveolar/ arterial equilibrates very fast
metabolized 0.004% into nitrogen in the GI tract
eliminated via the lungs
Side Effects; CNS; - increases CBF, CMR02 and ICP CV; -myocardial depression and sympathomimetic Resp; -increased RR, decreased TV -decreased response to hypoxia - transient hypoxia r/t second gas effect GI/GU -decreased RBF, UOP and GFR -decreased hepatic blood flow other; -expansion of gas -impaired fetal development - deceased hearing post op
Contraindications;
- closed air spaces (pneumo, bowel surgery/ obstruction, intra-ocular bubble procedure, inner ear surgery, VAE)
- MH; weak trigger
Caution;
- exposure to N20 during pregnancy linked with increased miscarriage rates
- Hx of PONV
Dantrolene
Centrally acting muscle relaxant
Uses;
-tx malignant hyperthermia
[[Without dantrolene 70% mortality, with dantrolene 5% mortality]]
MOA;
- Reduced muscle tone and metabolism; restores the balance between release and uptake of Ca
- prevents ongoing release of calcium from the Sarcoplasmic reticulum of muscle
- blocks the external entry of Ca through the VG channels into the sarcoplasm
- hypothesized to inhibit calcium conductance through ryanodine channel (the channel VA act directly on to allow release of Ca from the SR)
Dose;
- Initial Bolus; 2.5 mg/kg IV followed by
- Treatment; 2 mg/kg IV q 5 min to a (max 10 mg/kg)
- Maintenance; 1mg/kg q6 for 72 hours (may be switched to oral form)
Formulation of Dantrolene;
- Each vial is 20 mg Dantrolene and 3 mg mannitol; need to be diluted with 60 mL of sterile water (makes 60 mL/vial)
- (your facility should have 36 vials)
Pharmacokinetics;
-Half-life; 10 – 15 hours
Side Effects;
- can cause some muscle relaxation on its own
- May cause significant muscle weakness in patients with pre-existing muscle disease
- Phlebitis often follows administration of dantrolene
- liver dysfunction
Caution;
- calcium channel blockers & dantrolene sodium in combination may produce life-threatening hyperkalemia and myocardial depression
- pre-existing liver dysfunction (can cause hepatotoxicity)
- people with pre-existing muscle weakness
