Allergic rxns are more common with (ester / amide) anesthetics
ESTER
Sxs of allergic rxn to local anesthetic
dermatologic manifestations to anaphylaxis
How common is a true allergic rxn to local anesthetic?
unlikely w/ preservative-free lidocaine
intraneural injection of anesthetic:
sxs
pain, paresthesias, subsequent local damage to nerve
intravascular injection of local anesthetic:
sxs
- (lower doses) circumoral numbness, lightheadedness, tinnitus
- (higher doses) seizures, coma, respiratory arrest
mortality of ASA Class III,
mortality of ASA Class IV
4% mortality in class 3
25% mortality in class 4
pulseless electrical activity
any organized rhythm w/o a palpable pulse; most common rhythm after defibrillation
how is pulseless electrical activity (PEA) treated?
administer epinephrine in 1 mg doses IV every 3-5 minutes
- treated like asystole
- NOT a shockable rhythm bc electrical system in heart is working properly
- do NOT use atropine
stress-induced adrenal insufficiency:
effects
hypotension or cardiac arrest
stress-induced adrenal insufficiency:
cause
- chronic steroid use
- trauma patients w/ adrenal hemorrhage
- septic patients w/ adrenal infarcts
stress-induced adrenal insufficiency:
TREATMENT
IV bolus of hydrocortisone 100 mg or dexamethasone 4 mg is administered if adrenal shock is suspected, esp if pt is not responding to initial resuscitation efforts →
if therapeutic dose of glucocorticoid is not administered, patient may die
calcium sulfate:
use and characteristics
- vehicle for local Abx delivery
- not even a fraction of exothermic rxn as PMMA
- peak @ 3 hours, elutes over 72 hours
- *ABX MUST BE IN POWDER FORM
main mechanism of local anesthetics
block voltage-gated sodium channels on the neuronal cell membrane
which nerve fibers are most sensitive to local anesthetics?
Type B fibers (sympathetic tone)
nerve fibers, by most sensitive → least to local anesthetics
- Type B (sympathetic tone) - most sensitive
- Type C (pain)
- Type A delta (temp)
- Type A gamma (proprioception)
- Type A beta (sensory touch & pressure)
- Type A alpha (motor)
why are Type B fibers more sensitive to local anesthetics than Type C?
Type B fibers are myelinated, so they are more sensitive even though than are thicker than the thin, unmyelinated C fiber
propofol:
systemic effects
- dose-dependent respiratory depression
- systemic reduction in blood pressure
- anticonvulsant properties
propofol:
mechanisms
- direct effect on myocardium
- direct on vascular smooth muscle
- decrease in sympathetic activity
(decreased vascular resistance in arterial and venous smooth muscle)
spinal anesthesia:
relative contraindications
- anti-coagulation
- sepsis
- local cellulitis
- hypovolemia or shock
- increased intracranial pressure
- MI < 6 months prior to surgery
what type of hemostasis is recommended in an actively bleeding post-op patient?>
mechanical hemostasis (e.g. intermittent pneumatic compression);
pharmacologic chemoprophylaxis is CONTRAINDICATED in actively bleeding patients
abx that can be mixed with PMMA
tobramycin
erythromycin
vancomycin
cephalosporins
why would LA block be delayed or fail on severely infected paronychia?
ST in area of infection are ACIDIC → fractionates the drug largely to its cationic form, creating a marked decrease in transport across the cellular membrane
all local anesthetics are:
[acids / bases]
weak bases; two forms
- lipid-soluble uncharged
- hydrophilic charged
how does pKa of LA affect use?
closer the pKa of the LA is to the pH of the soft tissues, the more e_fficient, effective, and quicker_ the block will be
