Anesthesia

Question 1

Diff types of anesthesia?

Answer 1

• general: suppression of activity in CNS, unconsciousness and total lack of sensation
• sedation: inhibition of transmission of nerve impulses b/t higher and lower centers of the brain inhibition of anxiety and memory
• regional: use of local anesthetics to make a portion of body insensate by blocking transmission of nerve impulses b/t a part of body and spinal cord -
  peripheral: inhibits sensory perception w/in a specific location, nerve blocks.
  central: local anesthetic delivered around spinal cord and removes sensation of body below level of bloc (spinal and epidural)

Question 2

Endpts of anesthesia? Agents used?

Answer 2

• analgesia: opiates, local anesthetics, ketamine, NSAIDs
• amnesia: benzos
• hypnosis: barbiturates, propofol, etomidate
• immobility: muscle relaxants
• hemodynamic stability: BBs, sympathomimetics

Question 3

Risks of anesthesia?

Answer 3

• death
• MI
• PE
• post-op N/V

Question 4

What is the ASA classification?

Answer 4

• American society of anesthesiologists - classification of pt’s physicla status
• the greatest predictor of the probability of a complication occuring
• higher the ASA class = increased likelihood of surgical or anesthetic complications

Question 5

ASA classes?

Answer 5

• ASA I: a normal healthy pt (no smoking, no or very minimal drinking)
• ASA II: pt w/ mild systemic disease, (smoker, more than min. drinking, pregnancy, obesity, well controlled diabetes, well controlled HTN, mild lung disease)
• ASA III: pt w/ severe systemic disease, not incapacitating (diabetets, poorly controlled HTN, distant hx of MI, CVA, TIA, cardiac stent, COPD, ESRD, dialysis, hepatitis, pacemaker, EF below 40%)
• ASA IV: pt w/ severe systemic disease that is a constant threat to life ( recent hx of MI, CVA, TIA, cardiac stent, ongoing cardiac ischemia or severe valve dysfxn, implanted ICD, EF below 25%)
• ASA V: moribund pt who isn’t expected to survive w/o the operation (ruptured abominal or thoracic aneurysm, intracranial bleed w/ mass effect, ischemic bowel in face of sig cardiac pathology)
• ASA VI: a pt who has already been declared brain dead and whose organs are being removed for transplant

Question 6

What is regional/local anesthesia?

Answer 6

• pain blocked from a part of the body using local anesthetics

Question 7

Types of regional anesthesia?

Answer 7

• infitrative
• peripheral nerve block
• IV regional anesthesia
• central nerve blockade
• topical anesthesia
• tumescent anesthesia

Question 8

What is infiltrative anesthesia?

Answer 8

• local anesthetic injected into small area to stop sensation

Question 9

What is a peripheral nerve block?

Answer 9

• local anesthetic injected near a nerve that provides sensation to portion of the body

Question 10

What is IV regional anesethesia (aka Bier block)?

Answer 10

• dilute local anesthetic infused to a limb through a vein w/ a tourniquet placed to prevent the drug from diffusing out of the limb

Question 11

What is a central nerve blockade?

Answer 11

• infusion or injection of local anesthetic in or around a portion of the CNS
• spinal (intrathecal) and epidural

Question 12

What is topical anesthesia?

Answer 12

• special formulation that diffuses through the skin or mucous membranes (EMLA patcthes)

Question 13

What is Tumescent anesthesia?

Answer 13

• large amts of dilute local anesthesia infiltrated into subq tissue used in liposuction (puff up surrounding tissue w/ anesthesia)

Question 14

Indications and CIs for Neuroaxial anesthesia?

Answer 14

Indications:
surgery or pain
appropriate distribution

CIs:
pt refusal
infection
coagulopathy

Question 15

Benefits of spinal anesthesia?

Answer 15

• decreased surgical time by 12%
• 25% less blood loss
• 50% less intraop transfusion requirements
• may decrease the incidence of DVT or PE

Question 16

Benefits of epidural anesthesia and analgesia? Complications?

Answer 16

• less blood loss
• reduced platelet aggregation
• reduced stress response to surgery
• decreased incidence of DVT
• improved graft patency after LE revascularization
• pts w/ combined (general and epidural) for aortic surgery had lower incidence of death and major periop complications
• complications:
  MC: post procedural HA
  spinal hematoma or abscess

Question 17

Comparison of spinal and epidural anesthesia?

Answer 17

Spinal:
- location of injection:
lumbar region only (below L2)
- no specific levels affected
- many times just a 1 time dose

Epidural:

• injection: anywhere along the spine
• specific levels: chest, abdomen, pelvis and legs
• often a catheter is left in place for multiple injections

Question 18

Diff nerve blocks? How do you localize?

Answer 18

• brachial plexus: interscalene, supraclavicular, axillary
• digital block (no Epi!!)
• use paresthesias, US, and nerve stimulation for nerve localization

Question 19

How does a nerve block work?

Answer 19

• blocks Na channels

Question 20

Diff types of local anesthetics?

Answer 20

• Esters:
  short infiltration: 45-60:
  procaine (novocaine), 2-chloroprocaine
  long infitration 180-360 - tetracaine
• Amides:
  intermediate: lidocaine, mepivacaine
  long: bupivacaine, Ropivacaine

Question 21

Differential block - concentration and block produced?

Answer 21

• low concentration = sympathetic block
• intermediate = sensory
• high = motor
• anesthetic effect: dose dependent

Question 22

Diff blocks dependent on diff agents?

Answer 22

• Bupivacaine:
  sympathetic: 0.125% and below
  motor: 0.5% and greater
• lidocaine:
  sympathetic: below 0.5%
  motor: 2% and greater

Question 23

Why do we add Epi to LAs?

Answer 23

- prolong surgical anesthesia time: 
procaine from 45-60 to 60-90min
lidocaine from 75-90 to 90-180 min 
bupivacaine from 180-360 to 200-400 
- decrease peak serum levels
- intravascular marker 
- decrease surgical site bleeding

Question 24

When should you not add epi?

Answer 24

• when vasoconstrictive properties of Epi may compromise tissue perfusion (end arteries)
• fingers/toes
• penis
• ear/nose
• skin flaps

Question 25

Local anesthetic toxicty of lidocaine?

Answer 25

low plasma levels to high levels of lidocaine: - dizziness - tinnitus - shivering, dysphoria, nystagmus - somnolence, muscle twitching - seizures - cardiac arrhythmias - **CV instability and collapse

Question 26

Tx for local anesthetic toxicity?

Answer 26

1. stop injection 2. call for help 3. supportive care (ABCs) 4. 20% intralipid 1.5ml/kg/min, may repeat bolus (1-2x) 5. cardiopulmonary bypass