Pharmacology Flashcards
Routes of Rx Admin
IV - most reliable PO - most utilized pre op IM - poorly tolerated IN/INH - poorly tolerated Rectal - variable absorption with contents/pH
Available Inhalation Meds
N - narcan A - atropine V - valium E - epinephrine L - lidocaine
Hepatic Performance with Rx - Factors that decr metab
1 - CP450 in decr concentration
2- decr liver blood flow
3 - decr CP450 activity
4 - decr phase 2 conjugation with decr gluc-transferase (affects benzos, opioids)
Key Concepts in Peds Pharms
1 - greater amount of water (ECF % BW) alters Vd
2 - decr PRO amounts and function alters rx binding/duration
3 - decr fat/muscle content decr tissue available for drug ReD
4 - immature hepatic and renal functions alter rx metab and elimation
Rx Distribution Influences (x5)
1 - body composition (% water, % fat) 2 - tissue --> rx permeability 3 - cardiac output 4 - regional blood flow 5 - rx distribution between blood tissue (pKa, lipid soluble, pro binding)
Hepatic Maturity
Increased to mature/adult fxnl levels @ 2-3yrs, incr conc/activity of DME, incr hepatic blood flow, large liver:body size ratio
Protein Binding
Albumin –> binds acidic rx (benzos, barbs)
AAG –> binds basic rx (LA, opioids, propofol
Protein presence: Neo < Infant < child in amount and rx binding ability
Volume of Distribution Definition
Rx dose:plasma concentration
Small Vd = rx confined to intravasc space/plasma = likely water soluble
Large Vd = rx easily ReD to tissue, leaves intrvasc space/plasma = likely lipid soluble
Peds and Vd and Rx Type
Larger Vd with water soluble Rx as increased amount of ECF with neo/nb/infants. More Rx needed as expanded carrier space, and desire rapid effect.
Smaller Vd with lipid soluble Rx as decreased %BW/composition of fat/muscle. Increased BMR requires incr dosing of induction Rx. Tends to stay in VRG longer.
Induction/Sedation Drugs
Propofol: Infant 3-3.5 mg/kg, Child 2.5-3 mg/kg
Ketamine: IV 2 mg/kg, IM 5-6 mg/kg, PO/PR 3-6 mg/kg
Versed PO 0.5-.75 mg/kg, max 20mg, IV 0.1-0.2 mg/kg
Methohexital PR 20-30 mg/kg, IV 1-2 mg/kg (5hr duration)
Chloral Hydrate PO/PR 50-75 mg/kg
Problems with Opioid Use
1 - reduced clearance rates, especially with morphine & metabolites, incr age = incr clearance 2 - morphine crosses BBB easily d/t degree of ionization 3 - Fent class with incr action d/t low PRO binding in neo/inf 4 - No demerol as has long, active metabolites = seizures, atropine like structure yields tachycardia
NeuroMuscular Junction Immature d/t:
1 - decr nerve conduction velocity w/ incomp myelination
2 - immature Ach receptors (alpha/beta/gamma vs epsilon)
3 - decr Ach stores
4 - Ion channels open longer with each activation as a safety measure of immature muscles
Rationales for Peds NDMR dosing x3
1 - immature NM junction
2 - decr metab and elimination of Rx
3 - decr muscle mass
NDMR monitoring
Must use adductor poll as is = to diaphragm paralysis. Orbicularis occ = laryngeal muscles
Neos have decr TOF response and possible baseline fade d/t limited Ach storage
Muscle Relaxant Doses
Succs: infant IV 2-2.5 mg/kg IM 5 mg/kg
child IV 1.5-2 mg/kg IM 4 mg/kg
Panc/Vec IV 0.1 mg/kg Roc IV 0.6-1.2 mg/kg
Cis IV 0.15 mg/kg
Succinylcholine Characteristics
Higher dose required due to large volume of distribution
Probable longer duration with decr psuedocholinesterase activity in peds pt
IV dose likely to produce bradycardia, metab into Ach like structure producing cholinergic mediated bradycardia
Assoc with rhabdo, hyperkalemia, masseter spasm, MH
ExtraJunction Ach Receptors
Neurologic motor defects, direct muscle trauma, thermal injury, disease atrophy, sepsis, and prolonged use of relaxants can markedly increase the number of normal ACh receptors and, more important, the number of extrajunctional ACh receptors
NDMR: Pancuronium
Vagolytic property, incr HR/BP
80% excreted by kindey, unchanged, with major metabolite 3-D panc 50% active.
NDMR: Vecuronium
Hepatic metab with biliary/urinary excretion. Active metabolite 3-17D vec 10% active
NDMR: Rocuronium
Excretion via bile, mostly unchanged, useful for RSI
NDMR Reversal
Routinely reverse muscle relaxation, unless post op ventilation is planned.
Neostigmine 0.07 mg/kg, Edrophonium 1mg/kg
Glyco 0.01 mg/kg, atropine 0.02 mg/kg
Admin separately to know anti Ach is on board
Prob use atropine in pt < 1mo, incr vagal dominance
Atropine incr HR > glyco, crosses BBB while glyco doesn’t
Local Anesthetics
Metabolism of both esters (PChe) and amides (Hepatic) reduced in neo/infants.
Bound by AAG (basic rx), limited amounts in neo/inf = incr free rx
LA Max Doses:
Lidocaine: 7-10 mg/kg w/ epi // 5 mg/kg plain
Bupivicaine: 2.5-3 mg/kg w/ epi // 2-2.5 plain
Tetracaine: 1.5 mg/kg
Mepivicaine: 7 mg/kg w/ epi // 5 mg/kg plain
Epinephrine Max dose w/ halothane & dilutions
5 mcg/kg per 10m // 10 mcg/kg per 20m
1: 100,000 = 10 mcg/ml
1: 200,000 = 5 mcg/ml
1: 400,000 = 2.5 mcg/ml
1: 500,000 = 1.25 mcg/ml
