8 Anesthesia Flashcards
Concerning findings on airway exam for anesthesia?
BMI >31
Interincisor or intergingival distance >3cm
Class III or IV mallampati classification
Inability to protrude lower incisors to meet or extend past upper incisors
Radiation changes or thick obese neck
Limited extension or possible unstable cervical spine
Presence of full beard
Mallampati classification of the airway
Class I - Can see everything
Class II - cannot see all of pillars or uvula
Class III - cannot see pillars
Class IV - Cannot see anything
MAC
Minimum alveolar concentration - smallest conc of inhalation agent at which 50% of patients will not move with incision
Small MAC - more lipid soluble = more potent
Speed of induction is inversely proportion to solubility
Common AE for inhaled anesthetics?
Unconsciousness, amnesia, analgesia
Blunt hypoxic drive
Myocardial depression, increase cerebral blood flow and decrease renal blood flow
Nitrous oxide
Fast
Minimal myocardial depression
Tremors at induction
Halothane
Slow onset/offset
Highest degree of cardiac depression and arrhythmias
Least pungent - good for children
Halothane hepatitis
Fever
eosinophilia
Jaundice
Increased LFTs
Sevoflurane
Fast
Less laryngospasm
Less pungent
Good for mask induction
Isoflurane
Good fro neurosurgery - lowers brain consumption, no increase in ICP
Enflurane
Can cause seizures
Sodium thiopental
Barbiturate
Fast acting
AE: decreased cerebral blood flow and metabolic rate; decreased blood pressure
Propofol
Very rapid distribution and on/off
Amnesia, sedative, NOT analgesic
AE: Hypotension, respiratory depression, egg allergy
Metabolized in liver and by plasma cholinesterases
Ketamine
Dissociation of thalamic/limbic systems Cataleptic state (amnesia, analgesia) AE: Hallucinations, catecholamine release (increased CO2, tachycardia), increased airway secretions, increased cerebral blood flow CI: head injury Good for children
Etomidate
Fewer hemodynamic changes
Fast acting
Continuous infusions can lead to adrenocortical suppression
What is the last muscle to go down and first muscle to recovery from paralytics?
Diaphragm
What is the first muscle to go down and last muscle to recover from paralytics?
Neck muscles and face
Succinylcholine
Fast, short acting
AE: Fasciculations, increase ICP, malignant hyperthermia
CI: Hyperkalemia, open-angle glaucoma, atypical pseudocholinesterases
Malignant hyperthermia
Defect in calcium metabolism
Calcium release from sarcoplasmic reticulum causes muscle excitation-contraction syndrome
AE: increase ETCO2, fever, tachycardia, rigidity, acidosis, hyperkalemia
Treatment: dantrolene, cooling blankelts, HOC3, glucose, supportive care
What is the first sign of malignant hyperthermia?
Increased ETCO2
Dantrolene - MOA, dose
Inhibits Ca release and decouples excitation complex
Dose 10mg/kg
Hyperkalemia and succinylcholine
Depolarization release more K
CI: Severe burns, neurologic injury, neuromusclar disorders, spinal cord injury, massive trauma, acute renal failure
Atypical pseudocholinesterases and succinylcholine
Causes prolong paralysis
Seen in Asians
Non-depolarizing paralytic agents
Inhibit neuromuscular junctions by competing with acetylcholine
Get prolongation of these agents with myasthenia graves
Cis-atracurium
Hoffman degradation
Can be used in liver and renal failure
Causes histamine release
Rocuronium
Fast, intermediate duration
Hepatic metabolism
Pancuronium
Slow acting, long-lasting
Renal metabolism
AE: tachycardia
Neostigmine
Edrophonium
Blocks acetylcholinesterase, increasing acetylcholine
Reversing drugs for non-depolarizing agents
Neostigmine
Edrophonium
Atropine/glycopyrrolate - given with to counteract the effects of generalized acetylcholine overdose
MOA - local anesthetics
Works by increasing action potential, preventing Na influx
Why are infected tissues hard to anesthetize?
Acidosis inactivates it
AE of local anesthetics?
Tremors Seizures Tinnitus Arrhythmias (CNS symptoms present before cardiac)
Epinephrine with local anesthetics?
Allows higher doses to be used - vasoconstriction keeps the anesthetic local
CI: arrhythmias, unstable angina, uncontrolled HTN, poor collaterals (penis, ear), uteroplacental insufficiency
AE of opioids
Profound analgesia
Respiratory depression (decrease CO2 drive)
No cardiac effects
Blunt sympathetic response
Morphine
Analgesia Euphoria Respiratory depression Miosis Constipation Histamine release (hypotension) Decrease cough
Demerol
Analgesia Euphoria Respiratory depression Miosis Tremors Fasciulations Convulsions NO histamine release Can cause seizures - build up of normeperidine analogue (renal failure)
Methadone
Simulates morphine
Less euphoria
Fentynal
Fast acting
80x strength of morphine
No histamine release
Sufentanil
Remifentanil
Fast-acting narcotics
Short half-life
Most potent narcotic?
Sufentanil
Effects of benzodiazepines
Anticonvulsant Amnesic Anxiolytic Respiratory depression NOT analgesia Liver metabolism
Versed
Midazolam
Short acting
CI: pregnancy (crosses placenta)
Valium
Diazapam
Intermediate acting
Ativan
Lorazepam
Long acting
Benzo overdose
Flumazenil
Competitive inhibitor
AE: seizures, arrythmia
CI: elevated ICP, status epilepticus
AE of morphine in epidural
Respiratory depression
AE of lidocaine in epidural
Decreased heart rate and hypotension
Treatment of acute hypotension and bradycardia in patient with epidural?
Turn epidural down
Fluids
Phenylephirine, atropine
CI for epidural
Hypertrophic cardiomyoptahy
Cyanotic heart disease
(Sympathetic denervation causes decreased afterload, which worsens these conditions)
Spinal anesthesia
Injection into subarachnoid space - spread determined by baricity and patient position
- Neurological blockade is above motor blockade
CI: hypertrophic cardiomyopathy, cyanotic heart disease
Caudal block
Through sacrum
Good for pediatric hernias and perianal surgery
Epidural and spinal complications
Hypotension Headache Urinary retention (require catheter) Abscess/hematoma formation Respiratory depression (with high spinal)
Spinal headache
Caused by CSF leak after spinal/epidural
Headache gets worse with sitting up
Tx: rest, fluids, caffeine, analgesics; blood patch to site if it persists >24 hours
What pre-op conditions are associated with the most post-op hospital mortality?
Renal failure*
CHF
Symptoms of post-op MI
May have no pain or EKG changes
Sx: hypotension, arrhythmias, increased filling pressures, oliguria, bradycardia
What patients need pre-op work up?
Angina Previous MI SOB CHF Walk <2 blocks secondary to SOB or CP FEV1 <70% predicted Severe valvular disease PVCs >5/min High grade heart block Age <70 Dm Renal insufficiency Major vascular surgery
ASA class 1
Healthy
ASA class 2
Mild disease without limitations (controlled HTN, obesity, DM, sig smoking history, older age)
ASA class 3
Severe disease (angina, previous MI, poorly controlled HTN, DM with complications, mod COPD)
ASA class 4
Severe constant threat to life (unstable angina, CHF, renal failure, liver failure, severe COPD)
ASA class 5
Moribund (ruptured AAA, saddle PE)
ASA class 6
Donor
ASA class E
Emergency
Aortic, major vascular and peripheral vascular surgeries are ___ risk?
High
Carotid endarterectomy is ____ risk?
Moderate
Biggest risk factors for post-op MI?
Age >70yo DM Previous MI CHF Unstable angina
High cardiac risk Stratification for non-cardiac surgical procedures?
Cardiac risk >5%
- Emergent operations (esp elderly)
- Aortic, peripheral and other major vascular surgery (except CEA)
- Long procedure with large fluid shifts
Intermediate cardiac risk Stratification for non-cardiac surgical procedures?
Cardiac risk <5%
- CEA
- Head and neck surgery
- Intraperitoneal and intrathoracic surgery
- Orthopedic surgery
- Prostate surgery
Low cardiac risk Stratification for non-cardiac surgical procedures?
Cardiac risk <1%
- Endoscopic procedures
- Superficial procedures
- Cataract surgery
- Breast surgery
Best determinant of esophageal vs. tracheal intubation?
ETCO2
Intubated patient undergoing surgery with sudden transient rise in ETCO2
Most likely hypoventilation
Tx: increase TV or increase RR
Intubated patient with sudde drop in ETCO2?
MC: disconnected from the vent
PE - when associated with hypotension
MC PACU complication
Nausea and vomiting
High volume hospitals are associated with lower mortality for:
AAA repair
Pancreatic resection
