Anesthetics

Question 1

Discuss the mechanism of action and types of local anesthetics

Answer 1

Mechanism
- reversibly block voltage gated Na channels to prevent depolarization of cell thereby stopping action potential
- minimal affect on type A alpha nerve so have motor control
- very effective type A delta and type C for pain control
- very post-ganglionic block for sympathetic control
Lidocaine
- Duration 2hr (4 with epinephrine)
- 4.5mg/kg or 7mg/kg with epinephrine
Bupivacaine
- Duration 4hr (8 with epinephrine)
- 2.5mg/kg or 3mg/kg with epinephrine
Cocaine
- used for procedure involving high surface activity and vasoconstriction

Question 2

Discuss the systemic toxicity of local anesthetics

Answer 2

Progression
1. peri-oral numbness, lighteadedness, tinnitus, blurred vision
2. muscle twitching, decreased LOC and general seizure
3. coma and respiratory depression with cardiovascular collapse
CNS
- excitation: peri-oral numbness, lightheadedness, blurred vision
- excitation: muscle twitching, seizure, agitation
- depression: abnormal LOC, respiraotry depression
Cardiac
- prolonged PR interval, widened QRS, sinus bradycardia, heart block and arrest

Question 3

Discuss the management for local anesthetic toxicity

Answer 3

• Stop administration
• Get anesthesia help
• Stabilize
  
  • protect airway and provide 100% O2
  • monitor heart rhythm
  • anti-epileptic if indicated
• Reverse anesthetic
  
  • bupivicaine and ropivicaine reversed with 20% intralipid lipid emulsion given bolus IV

Question 4

Define regional anesthesia

Answer 4

• Injection of local anesthetic near nerve, resulting in anesthesia in large portion of body
  
  • include neuraxial anesthesia and peripheral nerve block

Question 5

Discuss the contraindications to neuraxial anesthesia

Answer 5

Absolute
- refusal
- lack of resuscitation equipment
- allergy
- INR >4 or platelets <80
- local or untreated systemic infection
- increased ICP
Relative
- Uncorrected hypovolemia
- fixed cardiac output state
- neurological deficit
- spina bifida
- previous back surgery

Question 6

Discuss the complications of neuraxial anesthesia

Answer 6

Immediate Local
- technical failure
- Intravascular injection
- mechanical injury
Immediate Remote
- hypotension due to sympathetic blockade
     - corrected with IV fluids and vasopressor (phenylephrine 50-100mcg)
- bradycardia
- anaphylaxis
Delayed
- Post-dural puncture headache
- infection

Question 7

Discuss the mechanism and indications for spinal anesthesia

Answer 7

Mechanism
- delivers local anesthetic or opioid into subarachnoid space directly on unmyelinated spinal nerves
- block all neural conduction below highest dermatome (usually L2)
Indication
- General surgical, Urology, and Orthopedic procedures
- OBGYN including C-section

Question 8

Discuss the mechanism and indications for epidural anesthesia

Answer 8

Mechanism
- delivers local anesthetic or opioid into epidural space by single injection or catheter
- block only around spinal nerve
Indication
- Analgesia during Labor and delivery
- supplement general anesthesia for post-op pain
- surgical correction of the respiratory system

Question 9

Discuss the goal of general anesthesia and the stages

Answer 9

Goals
- amnesia
- anesthesia
- analgesia
- areflexia (motor, autonomic)
- anxiolytic
Stages
- Induction is beginning of amnesia
- Excitement when have loss of consciousness, muscle become tense, have swallowing and gag reflex
- surgcial when have respiratory depression and 4:
- eyes initial roll back and then become fixed
- loss of corneal and laryngeal reflex
- dilation of pupil and loss of light reflex
- paralysis of intercostals and shallow abdominal breathing

Question 10

Discuss different types of IV anesthesia

Answer 10

Propofol
- rapid onset and recory
- have cardiovascular and respiratory depression
Etomidate
- Rapid onset and recovery
- Stable cardiovascular and respiratory
- have involuntary muscle movement
Ketamine
- moderate onset and recovery
- stimulate/stable for cardiovascular and respiratory systems (used in patients with shock)
- renal toxicity
Midazolam
- slow onset and recovery
- used in balance anesthesia and conscious sedation
 - Reversed with flumazenil
- Stable cardiovascular but respiratory depression
Fentanyl
- slow onset
- used in conscious sedation
- has cardiovascular and respiratory depression

Question 11

Discuss the minimal alveolar concentration and types of inhaled anesthetics

Answer 11

Minimal Alveolar Concentration
- concentration of vapor in lung needed to be effective
    - lower MAC is more potent
Desflurane
- rapid onset
- low potency
- cleared by lungs
Sevoflurane
- less pungent so can be used for induction and maintenance
- more potent
- some fluoride metabolite leftover

Question 12

Discuss the cardiovascular, respiratory, cerebral blood flow, renal function and liver function of the inhaled anesthetics

Answer 12

Cardiac
- decrease BP
- no change to HR
- decrease CO
Resp
- decrease RR
- Increase VT
- Increase PaCO2
Cerebral Blood Flow
- increase
Renal and Liver Function
- decrease

Question 13

Discuss the indications and method of rapid sequence intubation

Answer 13

• done to reduce likelihood of aspiration
  Indication
• patients requiring intubation who did not fast
• decreased LOC
• impaired airway reflexes
• Abnormal anatomy
• Decreased gastro-esophageal competence
• Raised intra-gastric pressure
• Delayed gastric empyting
  Method
• Suction
• Patient pre-oxygenated for >=3 minutes
• Cricoid pressure applied to close esophagus
• medication administered one after the other
• no Bag mask ventilation
• Intubate after 30 seconds after medication delivered