ANESTHESIA Flashcards
TYPES OF ANESTHESIA
o general
o sedation
o regional
GENERAL VS SEDATIVE VS REGIONAL
o GENERAL = suppression of activity in the CNS; unconscious & total lack of sensation
o SEDATION = Inhibition of transmission of nerve impulses between higher & lower centers of the brain; inhibition of anxiety & memory
o REGIONAL = use of local anesthetics to make a portion of the body insensate by blocking transmission of nerve impulses between a part of the body and the spinal cord
⦁ Peripheral = inhibits sensory perception within a specific location (nerve blocks)
⦁ Central = local anesthetic delivered around the spinal cord - removes sensation of the body below the level of the block (spinal & epidural)
ENDPOINTS OF ANESTHESIA
⦁ Hypnosis = temporary loss of consciousness & loss of memory
⦁ Analgesia = lack of sensation; autonomic reflexes are blocked
⦁ Muscle Relaxation
Amnesia (memory loss) = Benzodiazepines
Immobility = Muscle relaxants & Paralytics
Analgesia = Opiates, local anesthetics, Ketamine, NSAIDS
Hypnosis = Barbiturates, Propofol, Etomidate
Anesthesia (inhaled agents) = all of the above!
post op cognitive dysfunction more common with
cardiac surgery & elderly patients
anesthesia risks
⦁ death ⦁ MI ⦁ PE ⦁ Post op N/V ⦁ Post op cognitive dysfunction (persistent confusion lasting weeks or months; more common with cardiac surgery & in the elderly)
the greatest predictor of the probability of a complication occurring
ASA classification
the higher the ASA class =
increased likelihood of surgical or anesthetic complications
the ROOT CAUSE of 11% of adverse anesthetic events =
INCORRECT PRE-OP ASSESSMENTS
ASA CLASSIFICATION
⦁ ASA I = normal healthy patient; no smoking, and none/minimal drinking
⦁ ASA II = pt with mild systemic dz; smoker, or more than minimal drinking, pregnancy, obesity, well controlled DM, well controlled HTN, mild lung dz
⦁ ASA III = pt with severe systemic dz, not incapacitating; DM, poorly controlled HTN, distant hx of MI / CVA / TIA / cardiac stent / COPD / ESRD. Dialysis, active hepatitis, implanted pacemaker, EF < 40%, congenital metabolic abnormalities
⦁ ASA IV = pt with severe systemic dz that is a constant threat to life = recent hx of MI / CVA / TIA / cardiac stent. Ongoing cardiac ischemia or severe valve dysfunction, implanted ICD, EF < 28%
⦁ ASA V = moribund pt who is not expected to survive without the operation; ruptured abdominal or thoracic aneurysm, intracranial bleed with mass effect, ischemic bowel in the face of significant cardiac pathology
⦁ ASA VI = pt is has already been declared brain dead, and whose organs are being removed for transplant
regional / local anesthesia
pain blocked from a part of the body using local anesthetics
types of regional anesthesia
⦁ Infiltrative ⦁ Peripheral nerve block ⦁ IV regional anesthesia ⦁ Central nerve block ⦁ Topical anesthesia ⦁ Tumescent anesthesia
INFILTRATIVE ANESTHESIA (type of regional)
local anesthetic injected in a small area to stop sensation
local anesthetic injected in a small area to stop sensation
infiltrative
PERIPHERAL NERVE BLOCK (Regional type)
local anesthetic injected near a nerve that provides sensation to a portion of the body
local anesthetic injected near a nerve that provides sensation to a portion of the body
peripheral nerve block (regional / local)
IV Regional Anesthesia (Bier Block) (type of regional)
dilute local anesthetic infused to a limb through a vein with a tourniquet placed to prevent the drug from diffusing out of the limb
dilute local anesthetic infused to a limb through a vein with a tourniquet placed to prevent the drug from diffusing out of the limb
IV regional anesthesia (bier block)
dental block or digital nerve block =
peripheral nerve block
Infusion or injection of local anesthetic in or around a portion of the CNS (ex: Spinal - intrathecal, and epidural)
central nerve block
central nerve block
Infusion or injection of local anesthetic in or around a portion of the CNS (ex: Spinal - intrathecal, and epidural)
topical anesthesia
special formulation that diffuses through the skin or mucous membranes (ex: EMLA patches)
tumescent anesthesia
large amount of dilute local anesthesia is infiltrated into the subcutaneous tissue (used in liposuction / various other procedures)
NEUROAXIAL ANESTHESIA INDICATIONS & CONTRAINDICATIONS
= spinal (intrathecal) or epidural
- Indications
⦁ surgery or pain
⦁ appropriate distribution of anesthesia - Contraindications
⦁ Patient refusal
⦁ Infection (near site of injection)
⦁ Coagulopathy (on any blood thinner)
BENEFITS OF SPINAL ANESTHESIA
⦁ decreases surgical time by 12%
⦁ 25% less blood loss
⦁ 50% less intraoperative transfusion requirements
⦁ may decrease the incidence of DVT or PE
decreased surgical time, decreased blood loss, decreased intraoperative infusions, decreased risk of DVT/PE
BENEFITS OF EPIDURAL ANESTHESIA & ANALGESIA
⦁ less blood loss
⦁ reduced platelet aggregation
⦁ reduced stress response to surgery
⦁ decreased incidence of DVT
⦁ improved graft patency after LE revascularization
⦁ Patients with combined (general & epidural) for aortic surgery had lower incidence of death & lower incidence of major perioperative complications
COMPLICATIONS OF NEUROAXIAL ANESTHESIA
⦁ **MOST COMMON = post procedural headache
⦁ spinal hematoma or abscess
most common complication of neuroaxial anesthesia
post-procedural headache
SPINAL VS EPIDURAL
Spinal: injection = lumbar region only (below L2)
Epidural: injection = anywhere along the spine
Spinal: no specific levels
Epidural: levels of chest, abdomen, pelvis, legs
Spinal injection: many times just a one time dose
Epidural injection: often a catheter is left in place for multiply injections
nerve localization for regional block (finding the nerve)
o Paresthesia
o Nerve stimulation
o Ultrasound
common plexus blocks
⦁ Interscalene
⦁ Supraclavicular
⦁ Axillary
local anesthetics = esters or amides
Esters = rapid hydrolysis in blood by pseudocholinesterase
amides = metabolized in the liver
examples of Esters: and duration of action
- Short Acting: 45-60 min
⦁ Procaine (Novacaine)
⦁ 2-Chloroprocaine - Long Acting (180 - 360 min)
⦁ Tetracaine
examples of Amides: and duration of action
- Intermediate acting (75 - 90 min)
⦁ Lidocaine (Xylocaine)
⦁ Mepivicaine - Long acting (180 - 360 min)
⦁ Bupivacaine (Sensorcaine, Marcaine)
⦁ Ropivacaine (Naropin)
DRUG CONCENTRATION
- drug concentration = expressed as %
- to convert % to mg/mL = multiply % x 10
- ex: 0.25% x 10 = 2.5 mg / mL
- Epinephrine expressed as grams/mL (1:200,000) = 1 gram in 200,000 mL = 5 ug / mL (ug = have to move decimal 6 places over)
how to calculate dose
volume x concentration
ex: 30 mL x 0.25%
= 30 mL x 2.5 mg / mL = 75 mg
DIFFERENTIAL BLOCK
- Low concentration = sympathetic block
- Intermediate concentration = sensory block
- high concentration = motor block
low concentration = ________ block
intermediate concentration = ________ block
high concentration = _______ block
sympathetic
sensory
motor
BENEFITS OF ADDING EPINEPHRINE TO LOCAL ANESTHETICS
1) prolongs surgical anesthesia time
2) decreases peak serum levels; because maximum safe doses are higher when epinephrine is used
3) intravascular marker
4) decreases surgical site bleeding
WHEN TO NOT ADD EPI TO LOCAL ANESTHETICS
- when the vasoconstrictive properties of epi may compromise tissue perfusion ("end" arteries)
⦁ fingers / toes
⦁ penis
⦁ ear / nose
⦁ skin flapsmax dose of lidocaine with & without epi
4.5 mg/kg = without epi
7 mg/kg = with epi
treatment for local anesthesia toxicity
LIPOSIN (intralipid)
