Pharmacology pediatric anesthesia Flashcards
There is a large volume of distribution for
water soluble medications (higher TBW)
______ Vd of fat-soluble drugs occurs in pediatrics
decreased
Children have altered and reduced
protein binding- increases free fraction of medications
Children have an immature
blood brain barrier
Children have longer
half-lives (secondary to immature hepatic/renal function)
Pediatric dosing is typically based on a
per kilogram recommendation
Weight can be roughly estimated by the following:
50th percentile weight (kg)= (Age x2) + 9
<1: age (mo)/2+ 4
Regarding volume of distribution, neonates have a
proportionately higher total water content 70-75% (adult is 50-60%)
reduced % of fat
reduced amounts of lean muscle mass
-these differences result in a ECF volume of distribution proportionately HIGHER than that of an adult
There is an increased Vd of ________
water-soluble drugs (related to higher total water content)
The increased Vd of water-soluble drugs is due to
- larger initial doses of water-soluble drugs are required
- potentially delayed excretion
- succinylcholine, bupivacaine, many antibiotics
There is a decreased Vd of
fat soluble drugs (related to decreased fat & muscle mass)
With fat-soluble drugs, there is an
increased duration of action because there is less tissue mass into which the drug can distribute
-thiopental, fentanyl
Decreased Vd of fat soluble drugs is improved by age 2 related to
improved BBB
Membrane permeability is ______ in the newborn
HIGH
There is reduced total
serum protein concentrations
leading to more of the administered drug free in the plasma to exert a clinical effect (e.g. lidocaine & alfentanil)
In regards to protein binding, _______ may be needed for drugs such as barbiturates and local anesthetics
reduced dosing
Hepatic enzymes usually convert medications from a
less polar state (lipid soluble) to a more polar, water-soluble compound
in general this ability is reduced in neonates
The ability to metabolize a conjugate medication improves with
age with both increased enzyme activity and increased delivery of drugs to the liver
_________ have a prolonged elimination half-life in neonates
aminoglycosides & cephalosporins
_______ develops rapidly in first few months of life
GFR & tubular function
Renal function is______
less efficient than in adults
-incomplete glomerular development, low perfusion pressure, and inadequate osmotic load
The concentration of inhaled anesthetics in the alveoli
increase more rapidly with decreasing age: infants>children>adults
In pediatrics, the inhalation induction is
more rapid
overdose occurs quickly and is leading cause of serious complications
Excretion and recovery of inhaled anesthetics is
more rapid
Determinates of the wash-in of inhalational agents includes
inspired concentration
alveolar ventilation
functional residual capacity
cardiac output
solubility- wash-in is inversely related to the blood solubility
alveolar to venous partial pressure gradient
In regards to inhalational anesthetics, the pediatric population has:
increased respiratory rate (higher minute ventilation)
decreased FRC
increased cardiac output distribution to vessel-rich groups*****
It is popular to use
N2O to allow for 2nd gas effect that will speed induction further
Possible explanations for the increased induction speed include
cerebral maturation age-related differences in blood-gas partition coefficients state of hydration/dehydration type of anesthesia circuit vaporizer design
Faster induction + immature cardiac development equals
INCREASED risk of overdose
Blood pressure is VERY sensitive to volatiles because
- lack compensatory mechanisms
- immature myocardium
- reduced calcium stores
MAC changes with age:
infants have a higher MAC than noted in older children or adults
peaks around 3 months of age
Inhalation anesthetics potentiate the actions of
NDMRS
Describe the stages of anesthesia:
Stage I: disorientation
Stage II: excitement or delirium
Stage III: surgical anesthesia; plane III: this was the desired plane for surgery when muscle relaxants were not used
Stage IV: overdose
Nitrous oxide is commonly used in pediatrics to
facilitate inhalation induction
- enhances the rate of uptake of inhaled anesthetics into the alveoli (2nd gas effect)
- analgesia and amnesia during maintenance
The blood/gas partition coefficient and MAC of nitrous oxide is
0.47
104%
Nitrous oxide is contraindicated in
pneumothorax, necrotizing enterocolitis, bowel obstructions, etc.
may contribute to PONV
N2O doubles the size of a pneumothorax in
12 minutes
The 2nd gas effect relates to
Dalton’s law of partial pressure
The agent of choice for inhalation inductions is
sevoflurane
least irritating to the airway of the inhaled anesthetics
The blood gas solubility of sevoflurane is
0.68
The following can increase the production of Compound A:
high temperature as mixtures
low fresh gas flow rates <2L/min
use of Co2 absorbers containing barium hydroxide or soda lime
With sevoflurane there is a
dose related depression in RR & TV
The blood gas coefficient of isoflurane is
1.43
Pertinent info regarding isoflurane includes
slower & more pungent (major disadvantage)
appropriate to use in pediatrics, especially after inhalation induction
potentiates NDMR to a greater extent than sevoflurane or desflurane
least costly inhalation agent
The blood gas coefficient of desflurane is
0.42
Pertinent info regarding desflurane includes
most pungent, causes airway irritation (50% incidence of laryngospasm if used during induction) better use is maintenance use with LMA is controversial emergence is rapid
Propofol is _____ liphophilic and distributes rapidly from plasma to peripheral tissues
highly
Propofol requires _______ induction doses related to increased volume of distribution
larger
The elimination half time of propofol is
shorter due to higher rates of plasma clearance
Common IV induction for propofol is
1-3 mg/kg
- pain on injection
- associated with reduced PONV
TIVA infusion of propofol is
25 mcg-200 mcg/kg/min
-intraoperative nerve monitoring: <120-130 mcg/kg/min.
Propofol may produce
profound hypotension in critically ill infants**
Ketamine causes a
dissociation of the cerebral cortex
analgesic & amnestic- commonly used in burns/dressing changes
Side effects of ketamine include
secretions, vomiting, & hallucinations
-consider supplementing with glycopyrrolate 0.01 mg/kg IV to prevent excessive secretions
Ketamine preserves
spontaneous respirations and aids to maintain a patent airway, however apnea & laryngospasm may still occur
Ketamine dosages include
oral: 6-10 mg/kg
sedation IM: 2-5 mg/kg
IV induction: 1-2 mg/kg
IM induction: 5-10 mg/kg
Etomidate is not widely used in children because of
pain on injection, myoclonus, anaphylactoid reactions, and suppression of adrenal function
Etomidate is a
hypnotic steroid-based induction agent
Dose of etomidate is
0.2-0.3 mg/kg
Main advantage & disadvantage of etomidate includes:
advantage: CV stability in hypovolemic patients
disadvantage: adrenocortical suppression not well tolerated in critically ill children
With opioids in pediatrics there are
more potent effects
- considered to be a result of an immature blood brain barrier
- increased sensitivity of the respiratory centers
Describe the dose and use of morphine
dose 0.025-0.05 mg/kg IV
histamine release
hepatic conjugation is reduced
renal clearance is decreased
Fentanyl has a ______ duration of action
increased duration of action in high doses related to decreased fat/muscle
neonates & preterm infants may metabolize fentanyl more slowly
Describe the IV dose of fentanyl
- 25-1 mcg/kg IV
0. 5-2 mcg/kg/hr infusion
With hydromorphone, patients with compromised renal function are at risk for
metabolite accumulation & neuroexcitatory symptoms (tremor, agitation, cognitive dysfunction)
Naloxone may be used to
antagonize opioids
dose for reversal of opioid-induced respiratory depression is 0.25-0.5 mcg/kg, repeated doses until effect
Describe midazolam doses:
- 5 mg/kg PO (onset 20 minutes)
- 2-0.3 mg/kg intranasal
- 05 mg/kg IV (onset 5 minutes)
Clonidine may be administered as an
oral premed at 4 mcg/kg (60-90 min onset)
may cause residual sedation postop
Dexmedetomidine is useful for
sedation without respiratory depression
IV 0.25-1 mcg/kg over 10-15 minutes***
Neonates have a _______ sensitivity to NMBDs
increased
- reduction in release of acetylcholine and reduced muscle mass
- fetal receptors have a greater opening time, allowing more sodium to enter the cell
All muscle relaxants have a _____ onset
shorter onset because of faster circulation times
-may be difficult to monitor effects of relaxants with a peripheral nerve stimulator
Describe the dose of succinylcholine for infants
infants require larger doses because of the increased ECF volume of distribution
With succinylcholine, pediatrics are at increased risk for:
cardiac arrhythmias hyperkalemia rhabdomyolysis myoglobinuria masseter muscle spasm malignant hyperthermia
If cardiac arrest occurs after succinylcholine administration, treat for
hyperkalemia*******
______ should be given to prevent bradycardia
atropine 0.02 mg/kg IV/IM
Non-depolarizing muscle relaxants have a much greater
variability with dose & response
- immaturity of the nmj and increased extra-junctional receptors may result in increased sensitivity to drugs
- immaturity of the hepatic system may result in prolonged duration of action required for the liver to metabolize
For urgent or emergent reversal of large doses of rocuronium, the mean time to neuromuscular recovery is significantly faster with
sugammedex compared to spontaneous recovery with succinylcholine
Caution with ketorolac is used in
impaired renal, increased risk of bleeding, impaired bone healing
may be reserved for children >1 year
Neonates have very low
glycogen stores & are prone to hypoglycemia during NPO & stress (such as periods of illness & surgery)
symptoms of hypoglycemia include
jitteriness, convulsions, and apnea
Acute hypoglycemia management includes
10% dextrose 1-2 mL/kg
never administer bolus of D50% due to risk of vessel necrosis and higher osmolarity
maintenance on supplemental IV dextrose infusions
minimize preoperative fasting
D50% is equal to
50 grams of dextrose per 100 mLs= 0.5 grams/mL
To dilute D50% to D10% for PIV administration:
take 1 mL of D50% dilute into total of 5 mLs–> 0.1 gram/mL or D10%
Describe epinephrine dose for resuscitation:
1 mcg/kg to treat hypotension IV; 10 mcg/kg for cardiac arrest repeated q3-5 as needed
Describe atropine dose for resuscitation:
20 mcg/kg IV (for symptomatic bradycardia). max dose: 1 mg for child & 2 mg for adolescent
