Anesthesia Final Flashcards
Reversal drugs for NDMR
anticholinesterases
- inhibits AChase enzyme
- leads to increases in Ach at NMJ to compete with NDMR
Common Twitch monitoring placements
Ulnar nerve
- abbductor pollicis
Facial Nerve (CN VII)
- orbicularis occuli
- corrugator supercili
Posterior Tibial nerve
- flexor hallucis brevis
Which muscle relaxant shows fade
non-depolarizing
Constant infusion of Succinylcholine
Neuromusclar response will quickly drop (stage I) and return to almost normal before going back down (stage II)
- able to reverse with edrophonium in late stage II
Onset and duration of Succinylcholine
rapid onset (30-60s)
short duration (5-10 min)
Succinylcholine metabolism
Only a fraction reaches the NMJ
- majority metabolized by pseudocholinesterase
- rest diffuses away, limiting duration
how can you prolong the duration of Sux?
increase dose and decrease metabolism
What can decrease the amount of Pseduocholinesterases?
Pregnancy
Hypothermia
Liver disease
Drugs
What drugs decrease pseudocholinesterase?
*Echothiphate eye drops Organophosphate insecticide cytotoxic drugs MAO inhibitors Anticholinesterases Magnesium Trimethaphan Azathiprine Ester anesthetics
Homozygous for abnormal pseudocholineserase enzyme
1/3000 patients
Will have a prolonged block
6-8 hours
Dibucaine
local anesthetic that inhibits pseudocholinesterase
- Normal 80%
- Homozygous 20%
Dibucaine Number (DN) is proportional to function (quality), not amount of enzyme
Side effects and complications of Succinylcholine
- fasciculations
- increased intracranial pressure
- increase intragastric pressure
- increased intraocular pressure
- bradycardia and junctional arrhythmias
- anaphylaxis
- rhabdomyolysis
- hyperkalemia
Succinylcholine and Dysrrhythmia
Muscarinic receptors in the sinus node
- Bradycardia prone in children
- more common after 2nd dose
Hyperkalemia and Succinylcholine
Burn Patient
- OK in first 24 hours
- should not use post-burn 1-2 years after
Trauma
- 1 week post event to 60 days
Upper Motor Neuron Injury
- ok acutely
- within 6 months of onset of symptoms
Amino-Steroid NDMR
pancuronium
rocuronium
vecuronium
pipecuronium
Benzylisoquinolone NDMR
atracurium and cisatracurium
NDMR agonist or antagonist?
competitive antagonist with ACh
Long acting NDMRs
Pancuronium
Doxacurium
Pipecuronium
Short acting NDMRs
Mivacurium
Pancuronium metabolism
renal clearance 80%
Mivacurium metabolism
plasma cholinesterase
Which 2 intermediate acting NDMRs are metabolized in the bile and hepatic?
Vecuronium and Rocuronium
Which intermediate acting NDMR releases histamine?
Atracurium
Atracurium
- ester hydrolysis and spontaneous nonenzymatic degredation (Hoffman)
- histamine release
Cisatracurium
- ester hydrolysis and spontaneous nonenzymatic degredation (Hoffman)
- NO histamine release
What prolongs NDMR duration?
- volatile anesthetics
- antibiotics
- age (extremes)
- cardiovascular drugs
- electrolyte imbalances
- physiologic dysfunction
Which electrolyte mostly increases NDMR duration?
Increased Magnesium
What antibiotics mostly increase NDMR duration?
Aminoglycosides
- Gentamycin
- Tobramyclin
Tetracycline
Bacitracin
Reversal of NDMR
- binds to acetylcholinesterase receptor, blocking ACh
- increases ACh at nicotinic and muscarinic receptors
- must be given with anticholinergic (parasympatholytic)
Neostigmine for reversal
DOSE: 0.04-0.07MG/KG
ONSET: 1-3m
PEAK: 5-7m
DURATION: 40-60m
Edrophonium for reversal
DOSE: 0.5-1 mg/kg
PEAK: 1-5m
DURATION: 5-20m
Atropine for reversal
DOSE: 15-70mcg/kg
ONSET: 15-30 s
PEAK: 2 m
DURATION: 1-2 hrs
Glycopyrrolate for Reversal
DOSE: 10-20 mcg/kg
ONSET: 1m
PEAK: 5m
DURATION: 2-4hrs
Sugammadex
reverses Rocuronium and Vecuronium
- no anticholinergic necessary
- no recurarisation
- can reverse with no twitches? 16 mg/kg
What TOF ratio is needed for normal pharyngeal function?
0.9
Bradycardia observed after administration of succinylcholine to children is attributable to which mechanism
Muscarinic stimulation at the sinus node
What is the predominant mechanism for succinylcholine-induced tachycardia in adults?
Stimulation of nicotinic receptors at autonomic ganglia
Local anesthetics shift the balance of Na+ channels to _____
closed inactivated
Mechanism of action of local anesthetics
block the Na channel
What portion of the local anesthetic is responsible for the anesthetic action?
lipophilic portion
local anesthetics:
weak potency and short duration
procaine and chloroprocaine
local anesthetics:
moderate potency and intermediate duration
lidocaine, mepivicaine, and prilocaine
local anesthetics:
high potency and long duration
tetracaine, bupivicaine, ropivicaine, and etidocaine
Pharmacokinetics of local anesthetics
- weak bases (pKa > 7.4)
- small amounts exist in lipid-soluble form
- local anesthetics with pKs nearest to physiologic pH have the most rapid onset of action
- vasodilator influences potency
- increased blood flow increases absorption and decreases duration
What cells extract amide local anesthetics through first pass?
endothelial
How does the pka affect local anesthetics?
onset
How does lipid solubility affect local anesthetics
anesthetic potency
How does protein binding affect local anesthetics
duration
How does tissue diffusibility affect local anesthetics
onset
How does vasodilator activity affect local anesthetics
potency and duration
Cm
minimum effective concentration of local anesthetic necessary to produce conduction blockade of nerve impulses
Influenced by:
- nerve fiber diameter
- increased pH
- high frequency of nerve stimulation
the Cm of motor fibers is ____ that of sensory fibers
2x
Metabolism of amide local anesthetics
enzymes in the liver
(slow)
- slower metabolism leads to increased serum concentrations and potential for increased systemic toxicity
Metabolism of ester local anesthetics
hydrolysis in plasma
What metabolite may be responsible for ester allergic reactions?
para-aminobenzoic acid (PABA)
Alkalinization of local anesthetics
- increases the unionized franction of drug
- more lipid soluble
- speeds onset
- enhances depth of block
- increases spread of epidurals
How does epinephrine prolong LA duration?
vasoconstricts which decreases blood flow
What may reduce the risk of systemic toxicity in LA
decreasing rate of absorption
Lidocaine
- metabolized in liver
- vasodilator
- intrinsic analgesic properties
Mepivacaine
- similar to lidocaine
- lacks vasodilator activity
Bupivacaine
- renal excretion
- high affinity for heart muscle
Ropivacaine
- hepatic cytochrome P450 enzymes
- less systemic toxicity
- hepatic excretion
Prilocaine
- orthotoluidine converts hemoglobin to methemoglobin
- cyanosis with decreases oxygen carrying capacity
- methemoglobinemia can be reversed by methylene blue
Which *drug is a monoamine oxidase inhibitor associated with Serotonin syndrome?
Methylene Blue
MAOIs and which two classes of drugs can produce toxicity if mixed?
SRIs and Serotonin releasers
2 SNRIs
seratonin-norepinephrine reuptake inhibitor
- effexor
- cymbalta
Benzocaine
- weak acid (unionized)
- ideal for topical anesthesia
- rapid onset
- methemoglobin possible
Cetacaine
may also cause methemoglobinemia
How does cocaine affect vessels?
vasoconstrictor
allergic reactions to LA
- esters > amides
- preservatives
- NO cross sensitivity
Risk factors for local anesthetic toxicity
- overdose
- intravascular injection
- injection into highly vascular tissue
- decreased metabolism
Location of block and toxicity
Highest to Least
- intercostal
- caudal
- epidural
- brachial plexus
- sciatic or femoral
How much local is administered in an intercostal block?
3-5 cc per level
Toxic plasma concentration of lidocaine/mepivicaine/prilocaine
5-10 mcg/mL
What 2 things may reduce seizure thresholds?
increased serotonin and CO2
Hypokalemia hyperpolarizes the cell and _____ seizure threshold
increases
Paradox of Local Anesthetics
Low concentrations block Na channels and prevent arrhythmias
High concentrations eventually block automaticity and conduction
Why is Bupivicaine more likely than Lidocaine to bind to heart muscle?
largely unbound to protein
Large LA IV injection may cause:
- PVCs
- wide QRS
- V-tach
- Asystole
LA Toxicity increases with:
- pregnancy
- beta blockers
- CCB
- digitalis
- epinephrine
- phenylephrine
- hypoxemia
- acidosis
- hypercarbia
Lipid Emulsion Therapy
- 1.5 mg/kg 20% lipid bolus
- 0.25 mg/kg/min infusion for at least 10 minutes
ACLS for LA
- limit epinephrine to 10-100mcg boluses
- amiodarone preferred
- vasopressin not recommended
- avoid CCB and BB
If failure to respond to lipid emulsion and vasopressor therapy, begin ______
Cardiopulmonary Bypass
Transient Neurologic Syndrome (TNS)
- lower back and butt pain
- 6-36 hours after spinal anesthesia
- more common after lidocaine spinal
Cauda Equina Syndrome
diffuse injury across the lumbosacral plexus
Anterior Spinal Artery Syndrom
lower extremity weakness and paresis
- more common in older patients
- immediate imaging required
Max dosage of Lidocaine
4.5 mg/kg (7 mg/kg)
Max dosage of Mepivacaine
5 mg/kg (7 mg/kg)
Max dosage of Bupivacaine
2.5 mg/kg (3 mg/kg)
Max dosage of Tetracaine
1.5 mg/kg (2.5 mg/kg)
EMLA cream
Eutectic Mixture of Local Anesthetics
- 2.5% Lidocaine and 2.5% prilocaine
1 amp (1cc) of 1:1000 in 10 cc =
1:10,000
1 amp of 1:1000 in 200cc
1:200,000
Spinal Anesthesia
- rapid in onset
- gravity dependent
- sensory and sympathetic block (2 level differential) [sensory farther down]
Epidural Anesthesia
- subarachnoid effect
- diffuses into paravertebral area
- test dose
- continuous
COX2 inhibitor drug
Celecoxib (celebrex)
COX-1 vs COX-2
COX - (constitutive)
COX-2 (inducible)
TXA2
platelet activation
PGI2 and PGE2
GI mucosa protection
Renal vasculature
PGE2 and PGD2
bronchodilation and renal function
PGH2
inflammation
COX-1 produces what?
Thromboxane A2
Prostacyclin
Prostaglandin E2
COX-2 produces what?
proteases
prostaglandins
other inflammatory mediators
Aspirin and Platelets
aspirin binds permanently to platelets
- blocks thromboxane
- platelets must be replaced (7-14 days)
NSAIDS and renal function
- NSAIDS and COX-2 inhibitors reduce GFR
- PGE2: peripheral edema
- PGI2: hyperkalenia and acute renal failure
What is your enemy when taking care of a person using NSAIDS?
Hypovolemia
- Check creatinine levels before giving Toradol
- Normal 0.6-1.2
NSAIDS and PUD
- increase HCL secretion
- decrease mucin secretion
Which NSAID is the worse for GI?
Aspirin
Cardiovascular side effects of NSAIDS?
- heart failure
- myocardial infarction
- hypertension
Which NSAID is worse for the heart?
Celecoxib
NSAIDS and increased venous thromboembolus
COX2 inhibitrs result in decreased prostacyclins and unapposed thromboxane
AERD
Aspirin Exacerbated Respiratory Disease
Sampter’s Triad
- aspirin sensitivity
- nasal polyps
- asthma
2 unlikely drugs that could cause Reye’s syndrome
Alka Seltzer and Pepto-Bismol
Steven-Johnson Syndrome
hypersensitivty reaction, likely to Aspirin
- toxic epidermal necrolysis
Leading cause of acute liver failure in the US
Acetaminophen overdose
- co-toxic with ETOH
Capsaicin
decreases C-fiber activation in the presence of substance P
Clonidine
increases effect and duration of pain relief
- centrally acting a2 agonist
- hypotension