Chapter 8: Anesthesia Flashcards
- Blunt hypoxic drive
- Caused unconsciousness, amnesia, some analgesia
- Most have myocardial depression, increase CBF, decrease RBF
Inhalational agent
Smallest concentration of inhalation agent at which 50% of patients will not move with incision
MAC (minimum alveolar concentration)
Fast, minimal myocardial depression; tremors at induction
Nitrous oxide (NO2)
- Slow onset / offset, highest degree of cardiac depression and arrhythmias
- Least pungent, which is good for children
Halothane
Manifestations of halothane hepatitis
Fever, eosinophilia, jaundice, increased LFTs
Fast, less laryngospasm and less pungent; good for mask induction
Sevoflurane
Good for neurosurgery (lowers brain oxygen consumption; no increase in ICP)
Isoflurane
Can cause seizures
Enflurane
- (Barbiturate) fast acting
- Side effects: decrease CBF and metabolic rate, decrease blood pressure
Sodium thiopental
- Very rapid distribution and on/off; amnesia; sedative
- Not an analgesic
- Metabolized in liver and by plasma cholinesterase’s
- Side effects: hypotension, respiratory depression
Propofol
Dissociation of thalamic / limbic systems; places patient in a cataleptic state (amnesia, analgesia).
- No respiratory depression
- Contraindicated in patients with head injury
- Good for children
Ketamine
Side effects: hallucinations, cathetcholamine release (increase CO2, tachycardia), increased airway secretions and increased cerebral blood flow
Ketamine
- Fewer hemodynamic changes; fast acting
- Continuous infusions can lead to adrenocortical suppression
Etomidate
When is RSI indicated?
- Recent oral intake
- GERD
- Delayed gastric emptying
- Pregnancy
- Bowel obstruction
Last muscle to go down and first muscle to recover from paralytics
Diaphragm
First to go down and last to recover from paralytics
Neck muscles and face
Only one is succinylcholine; depolarizes neuromuscular junction
Depolarizing agents
- Caused by a defect in calcium metabolism
- Calcium released from sarcoplasmic reticulum causes muscle excitation: contraction syndrome
Malignant hyperthermia
First sign of malignant hyperthermia
Increased end-tidal CO2
Side effects: first sign is increased end-tidal CO2, then fever, tachycardia, rigidity, acidosis, hyperkalemia
Malignant hyperthermia
Tx: dantrolene (10mg/kg) inhibits calcium release and decouples excitation; cooling blankets, HCO3, glucose, supportive care
Malignant hyperthermia
When do you NOT use succinylcholine?
Severe burns. Neurologic injury. Neuromuscular disorders. Spinal cord injury. Massive trauma. Acute renal failure.
Complications of succinylcholine
- Malignant hyperthermia
- Hyperkalemia
- Open-angle glaucoma
- Atypical pseudocholinesterases
- Inhibits neuromuscular junction by competing with acetylcholine
- Can get prolongation of these agents with myasthenia gravis
Nondepolarizing agents
Non-depolarizer
- Undergoes Hoffman degradation
- Can be used in liver and renal failure
- Histamine release
Cis-atracurium
Non-depolarizer: Fast, intermediate duration; hepatic metabolism
Rocuronium
Non-depolarizer:
- Slow acting, long-lasting; renal metabolism
- Most common side effect: tachycardia
Pancuronium
Blocks acetylcholinesterase, increasing acetylcholine
Neostigmine
Edrophonium
Should be with neostigmine or edrophonium to counteract effects of generalized acetylcholine overdose
Atropine or glycopyrrolate
Work by increasing action potential threshold, preventing Na influx.
- Can use 0.5 cc/kg of 1% lidocaine.
Local anesthestics
Why are infected tissues difficult to anesthetize with local anesthetics?
Secondary to acidosis.
Length of action of local anesthetics: greatest to least
Bupivacaine > lidocaine > procaine
Side effects of local anesthetics
Tremors
Seizures
Tinnitus
Arrhythmias (CNS symptoms occur before cardiac)
What does addition of epinephrine to local anesthetics allow?
Allows higher doses to be used, stays locally
When do you not use epinephrine with local anesthetics?
No epi with:
Arrhythmias, unstable angina, uncontrolled hypertension, poor collaterals (penis and ear), uteroplacental insufficiency
Two different genres of local anesthetics
Amides (all have “i” in first part of their name)
Esters
Allergic reactions: amides vs esters
Esters: increased allergic reactions due to PABA analogue
Metabolism: opioids
Metabolized by the liver and excreted via kidney
What can narcotics cause precipitate in patients on MAOIS?
Hyperpyrexic coma
Analgesia, euphoria, respiratory depression, miosis, constipation, histamine release (causes hypotension), decreased cough
Morphine
Analgesia, euphoria, respiratory depression, miosis, tremors, fasciculations, convulsions
Demerol
Does demerol cause histamine release?
NO.
Why avoid demerol in patients with renal failure?
Can cause seizures (buildup of normeperidine analogues)
simulates morphine, less euphoria
Methadone
Fast acting; 80x strength of morphine (does not cross-react in patients with morphine allergy); no histamine release
Fentanyl
Very fast acting narcotics with short half lives
Sufentanil and remifentanil
Most potent narcotic
Sufentanil
Anticonvulsant.
Amnesic.
Anxiolytic.
Respiratory depression.
Benzodiazepines
Do benzodiazepines have pain relief?
No.
Metabolism: benzos
Liver
Benzo:
- Short acting
- Contraindicated in pregnancy
- Crosses placenta
Versed (midazolam)
Benzo:
- Intermediate acting
Valium (Diazepam)
Benzo:
- Long acting
Ativan (lorazepam)
- Benzo OD
- Competitive inhibitor
- May cause seizures and arrhythmias
- Contraindicated in patients with elevated ICP or status epilepticus
Flumazenil
MC side effect flumazenil
Nausea
Allows analgesia by sympathetic denervation.
Vasodilation.
Epidural anesthesia
Epidural with morphine
Can cause respiratory depression
Lidocaine in epidural
Decreased heart rate and blood pressure
How can motor function be spared with epidural?
Dilute concentrations
Tx: acute hypotension / bradycardia with epidural
Turn epidural flows down.
Fluids.
Phenylephrine.
Atropine
Epidural level: affect cardiac accelerator nerves
T1-5
Contraindications: epidural
Hypertrophic cardiomyopathy.
Cyanotic heart disease.
Why h-cmp and cyanotic heart disease contraindications to epidural anesthesia?
Sympathetic denervation causes decreased after load, which worsens these conditions
Injection into subarachnoid space, spread determined by baricity and patient position
Spinal anesthesia
Contraindications: spinal
Hypertrophic cardiomyopathy.
Cyanotic heart disease.
Caused by CSF leak after spinal / epidural.
Headache gets worse sitting up.
Spinal headache
Tx: Spinal headache
Rest. Fluids. Caffeine. Analgesics. Blood patch to site if it persists > 24 hours.
Associated with most postop hospital mortality
- Pre-op renal failure
2. CHF
May have no pain or EKG changes. Can have hypotension, arrhythmias, increased filling pressures, oliguria, bradycardia.
Postop MI
Patients who need cardiology workup pre-op (x13)
Angina. Previous MI. SOB. CHF. METs 5min. High grade heart block. Age >70. DM. Renal insufficiency. Patients undergoing major vascular surgery.
Considered high risk surgery
Most aortic, major vascular, peripheral vascular surgery
Risk: carotid endarterectomy (CEA)
Considered moderate risk surgery
Biggest risk factors for post MI
Age > 70. DM. Previous MI. CHF. Unstable angina.
Best determinate of esophageal vs tracheal intubation
End-tidal CO2
Intubated patient undergoing surgery with sudden transient rise in ETCO2
Dx? Tx?
Dx: most likely hypoventilation.
Tx: increased tidal volume or increased respiratory rate.
Goal endotracheal tube placement
2cm above the carina
Associated with lower mortality for abdominal aortic aneurysm repair and for pancreatic resection
Higher volume hospitals
MC PACU complication
nausea and vomiting.
