| Minimum Alveolar Concentration|
|Lowest concentration of an inhalant that obliterates movement in 50% of patients when pain is applied. Low MAC= Potent Inhalant.|
|Factors that increase MAC in patients||Young patients, hyperthermia, CNS Stimulant, Physostigmine, Alcohol dependancy.|
|Factors that decrease MAC in patients||Elderly, hypothermia, acute ETOH ingestion, CNS depressants (barbiturates, Propofol, Benzos) TRanquilizers, Narcotics, Pregnancy, Alpha 2 adrenergic agonists (Clonidine and Dexmedetomine).|
|Order of Inhalant Anesthetic uptake in tissues||Directly proportional to vascularization of tissue.|
1. Highly Vascular regions- heart, brain, liver kidney
2. Moderately perfused regions- muscle, skin
3. Mildly perfused regions- Fat, Bone Marrow
4. Poorly perfused regions- Tendon, Ligaments, Bone
Elimination occurs in the reverse order with poorly perfused regions storing Inhalant Anesthetic longer
|Swallowing, retching and vomiting||These disappear in this order on induction and reappear in this order on emergence.|
|Inhalant Malignant Hyperthermia Triggers||All inhalants except Nitrous Oxide.|
|Increased Emergence Delirium associated with what Inhalants?||Sevoflurane, Desflurane, Isoflurane, and Halothane.|
|Inhalants used for Mask Induction||Halothane and Sevoflurane|
|Isoflurane||CV- decrease BP and Peripheral resistance (dilation), but increase HR so no change in CO. May promote Coronary Steal. |
Strong pungent irritating odor.
Rapid recovery- lucid w/in 15-30 minutes after termination.
Potentiates neuromuscular blockade
Post-op shivers may increase heat loss d/t vasodilation.
Less dysrhythmias from less myocardial sensitivity to catecholamines.
|Desflurane|| Used for Maintenance only. Not mask induction.|
Possibly promotes Coronary Steal/Ischemia
Rapid onset and recovery. Little residual.
Anticipate need for analgesia immediately post op.
Commonly used in ambulatory setting.
Similar solubility to Nitrous Oxide.
Promotes neuromuscular blockade.
|Sevoflurane|| Useful in mask inductions d/t pleasant smelling and non-irritating.|
Minimal increase in ICP and Cardiac dysrhythmias. Does not appear to promote Coronary Steal.
Rapid onset and offset.
More frequently used in peds and ambulatory setting.
May cause agitation in children.
|Enflurane|| Used for maintenance anesthesia. May cause coughing and laryngospasm. |
Shivering on emergence, hypotension, respiratory depression, and decreased renal blood flow.
Slow onset and offset.
Contraindicated w/ seizures.
|Halothane|| Used for mask induction and maintenance.|
Pleasant smelling and non-irritating.
Causes increased ICP.
Bradycardia, decreased contractility, SV and CO. Impairs AV node conduction.
Decreased renal flow improved w/preop hydration.
Potential to develop Halothane Hepatitis 5-6 days after exposure.
|Nitrous Oxide||Rapid onset and offset. |
Not potent enough to use alone. Produces mild amnesia.
No irritation of respiratory tract.
Initially increases HR, SVR and Contractility but ultimately decreases all.
Increased analgesia w/ opioids.
Decreases volatile agent dose needed.
May increase ICP.
Decrease renal blood flow.
Increase potential for diffuse hypoxia
Potential for gas to fill cavities, i.e. the middle ear causing tympanic rupture and hearing loss.
Only Inhalant not MH trigger.