Ex 2 Peds 1 Flashcards
Neonatal period
first 28 days outside uterus (“extrauterine life”)
Neonatal anesthesia
anesthesia only in this timeframe if urgent or life threatening
Which is more resistant: full term or preterm infants?
More resistant: full term
highest rate of adverse events intraop/postop
Neonates + infants < 12 months old
Preterm infants are more prone to developing
respiratory complications
Neonate - Age
0-1 month (28 days)
Infant - Age
1-12 months
Toddler - Age
1-3 years
Child - Age
4-12 years
Adolescent - Age
13-19 years
Highest mortality in pediatric anesthesia is associated with
cardiac arrest, medication related, CVS
Over half of all anesthesia related cardiac arrests were among what age group
infants < 1 y/o
*1/3 of arrests were ASA I-II
What occurs 2x as often in pediatric anesthesia (vs adults)?
Bronchospasm
Laryngospasm
Aspiration
Bradycardia is associated with
inadequate ventilation or impending catastrophe
Organogenesis takes place within
8 weeks of conception
Preterm infant
born before 37 weeks gestation
Postmature infant
born after 42 weeks gestation
Low birth weight infant
born weighing < 2500 g
What may indicate potential anesthetic implications/problems during perinatal history eval?
Problems during pregnancy: maternal drug abuse, infxn, eclampsia, diabetes
or during/after delivery: fetal distress, meconium aspiration, prematurity, postdelivery intubation
functional unit of placenta
chorionic villus
Fetal circulation is characterized by
high PVR + low systemic circulatory resistance
Why does fetal circulation have high PVR?
uninflated atelectatic lungs + hypoxic vasoconstriction
Why does fetal circulation have low systemic circulatory resistance?
High flow + low impedence of the placental vessels
Intracardiac shunts
Foramen ovale (atrial septum; RA to LA)
Extra cardiac shunts
Ductus arteriosus (RV-pulm artery to aorta) + ductus venosus (liver to inf. Vena cava)
Highest rates of AEs intra/postop
Neonates + infants (< 12m)
Risk of pediatric anesthesia most often d/t
Inadequate ventilation + unexplained CVS events
Occurs 2x as frequently in peds vs adults
Bronchospasm, laryngospasm, aspiration
Bradycardia in pediatrics
Sentinel sign of inadequate ventilation or impending catastrophe
10x as often in infants vs 4 year old
Organogenesis
Within 8 weeks of conception
1st trimester stress may cause abnormal organogenesis
Stress during 2nd trimester may result in
Abnormal functional development of organs
Stress during 3rd trimester may result in
Smaller organs or reduced muscle/fat mass
Thin layer of cells that separate maternal + fetal blood in placenta
Syncytial trophocytes
Cord blood is comprised of
2 umbilical arteries + 1 umbilical vein
What is getting bypassed in fetal circulation + how?
Lungs bypassed d/t Increased PVR via:
- Foramen ovale (RA to LA)
- Ductus Arteriosus (PA to Aorta)
Route of blood returning to mom from fetus
LV –> aorta –> common iliac artery –> umbilical arteries
PDA connects
aorta + PA
PFO connects
RA + LA
Ductus Venosus connects
sinusoids of liver to inferior vena cava
Fetal circulation of blood through the lungs is limited by
hypoxic pulmonary vasoconstriction (increased resistance in lungs d/t decreased O2)
Fetal circulation is characterized by
3 shunts: DV, DA, FO
High PVR
Low SVR
During birth, the first breath (while placenta still attached) causes what to occur?
- pulmonary alveoli open up*
- Decreased pressure in pulmonary tissue
- Decreased pressure in RH (blood rushes to fill alveolar capillaries)
- LH pressure increases (increased blood from Pulm veins)
Transitional Circulation
Occurs at birth d/t cessation of placental blood flow
- decreases PVR
- increases SVR
Transitional circulation: PVR decreases d/t
asphyxia, lung expansion, pulmonary vasodilation d/t presence of oxygen (+ no longer receiving prostaglandins from placenta - which keeps DA open)
When placenta is cut off, what significant events occur?
2 events:
- fetal asphyxia (decreased PVR)
- increased pressure in aorta + SVR
Why does the foramen ovale close?
LA > RA
d/t pulmonary vascular dilation
When does foramen ovale close?
At birth
*permenantly closes 2-3 months
Why does the ductus arteriosus close?
OXYGEN
*exposure to oxygenated blood
+ SVR > PVR
When does the ductus arteriosus close?
1-8 days
- anatomic closure 1-4 months
- premies: may take longer to close
When does the ductus venosus close?
1-3 after birth
- mechanism unknown; muscular constriction
- portal venous pressure increases
- results in all vena cava blood = deoxygenated
Risk factors for prolonged transitional circulation
Prematurity Acidosis Infection Pulmonary Disease Hypothermia Hypercarbia
Flip Flop
Revert back to fetal circulation
Flip Flop is d/t
Hypoxia, Hypercapnia, anesthesia induced changes in peripheral or pulmonary vascular tone
Mechanism of flip flop
Hypoxia (via any mechanism) causes pulmonary vasoconstriction (increased PVR) = R to L shunt (PDA or PFO)
Tx: Flip flop
Hyperventilation
*increased PA pressure will return to normal d/t decreased PaCO2
When would RA > LA in a baby?
pHTN
Anesthetic goals of baby at risk for transitional circulation/flip flop
- keep infant warm
- maintain normal arterial O2 + CO2 tensions
- minimal anesthetic induced myocardial depression
PPHN
Persistent Pulmonary HTN of the Newborn
Persistent fetal circulation
PPHN
PPHN: characteristics
Sustained elevation of PVR R to L shunt (PFO/PDA) *vicious cycle* RV + CO decreased May be d/t Bronchopulmonary Dysplasia or CV disease
Risk of PPHN
RV dysfunction + RV hypertrophy (cor pulmonale)
PPHN Tx
Pulmonary Vasodilators - NO -Sildenafil -Milrinone -Bonsentan -Prostanoids Ventilation strategies: high frequency ventilation or exogenous surfactant administration Avoidance of Hypoxemia, acidosis Normal Hematocrit
Prostanoids
Iloprost, Prostacyclin, or treprostinil
Why does a normal hematocrit help treat PPHN?
To ensure adequate oxygen carrying capacity while avoiding polycythemia (hyperviscosity can increase PVR)
CV System: immature components
- myocardium
- contractile components
- baroreceptor reflex
- sympathetic NS
Cardiac output is solely dependent on
heart rate
Autonomic innervation is predominately controlled by the
parasympathetic nervous system
What may occur with suctioning + laryngoscopy?
bradycardia
Immature baroreceptor reflex may lead to _____ ; Tx =
inability to compensate for HOTN
Tx: atropine or epi if refractory
ventilation with high peak pressures in neonate may result in
LV dysfunction + overload of RV
Neonates have a poor sensitivity to
volume loading
-may develop CHF d/t stiff LV compressing RV (decreasing CO)
Preterm Neonate: Vital Signs
HR: 120-180
SBP: 45-60
DBP: 30
Term Neonate: Vital Signs
HR: 100-180
SBP: 55-70
DBP: 40
1 Year old: Vital Signs
HR: 100-140
SBP: 70-100
DBP: 60
2 Year old: Vital Signs
HR: 84-115
SBP: 75-110
DBP: 70
5 Year old: Vital Signs
HR: 80-100
SBP: 80-120
DBP: 70
HOTN in anesthetized newborn
SBP < 60 mmHg
EBV: Premature
90-100 mL/kg
EBV: Neonate (< 1 month)
80-90 mL/kg
EBV: Infant (3 months-3 years)
75-80 mL/kg
EBV: Children > 6 y/o
65-70 mL/kg
Newborns blood volume is dependent on
time of cord clamping (transfusion from placenta)
Intravascular volume of newborn changes how
- Decreases 25% in immediate postnatal period (loss of intravascular fluid)
- blood volume increases over next 2 months, peaks at 2 months old
HOTN in anesthetized 1 year old
SBP < 70 mmHg
HOTN in anesthetized older child
SBP 70 mmHg + (age x 2)
Why is the cardiac output of a neonate higher than that of an adult?
Necessary to meet higher metabolic oxygen consumption demands
Newborn cardiac output
180-240 mL/kg
2-3x adults CO: 70mL/kg
Predominant hemoglobin in babies
fetal hemoglobin
Normal Hemoglobin at birth
18-20 g/dL
Normal Hct: Full term baby
55%
Normal Hct: 3 months old
30%
Normal Hct: 6 months old
35%
At what age in babies does the Hgb hit lowest point?
3 months old - decline in Hgb reaches nadir
“physiological anemia”
Type of cell that secretes surfactant
Type II pneumocytes
When does fetus begin to produce surfactant? Peak surfactant production?
Begins: 22-26 weeks gestation
Peaks: 35-36 weeks gestation
Why would a baby not have enough surfactant?
Premature neonate: absence of surfactant = stiff, noncompliant alveoli
What mechanism describes surfactant effect on lungs?
Law of Laplace
P=2T/R
Surfactant decreases surface tension within the alveoli to decrease alveolar collapse
Treatment for infantile respiratory distress syndrome
Synthetic surfactant
Continuous positive airway pressure
Mechanical ventilation
*steroids if preterm labor before 26w
Narrowest portion of neonate airway
Cricoid Cartilage
beyond vocal cords aka glottis
Which law explains why pediatric airway anatomy is at higher risk for problems?
Poiseuilles Law
- small changes in radius can significantly increase resistance to airflow
- resistance is inversely proportional to radius^4 (laminar) or radius^5 (turbulent)
Biggest difference between adult + pediatric airway anatomy
- Shallow vallecula
- larynx directed towards nasopharynx (nasal breathing); C2-C4
- large arytenoids, tongue, occiput
- Subglottic regon = small, conical shaped
- cricoid lumen = ellipsoid, not round
- Cricoid cartilage lined w/ pseudostratified epithelium (easily injured = edema, stridor)
- should roll = best
Best position for infant intubation
Headrest + shoulder roll
- glabella + chin plane horizontally aligned
- neck: wide/open
- external auditory meatus + substernal notch plane horizontally aligned
Best position for toddler intubation
Simple head extension
Infants are obligate nose breathers until
3 months
Airway obstruction risks in infants
choanal atresia, nasal secretions
failure of development of the posterior opening between nasal cavity + nasopharynx
choanal atresia
Alveoli increase in size and number until
child is 8 years old
Breathing mechanics in children
- pliable chest wall = paradoxical breathing
- horizontal rib orientation
- decreased FRC
- belly breathing
Muscle fibers involved in respiratory mechanics + their importance
Type I - resistant to fatigue, slow twitch
Type II - susceptible to fatigue, fast twitch
**neonates have more Type II, not enough Type I. At risk for respiratory failure d/t reduced reserve
FRC in infant vs adult
25mL/kg in infant
45mL/kg in adult
*less effective reserve d/t increased metabolism + O2 consumption rates
Postop monitoring required for
infants < 45-55 weeks postconception
*24h observation in hospital
over-inflation of lung
Hering breur reflex
-pulmonary stretch receptors present in smooth muscle of airways respond to excessive stretching of lung during large inspiration
Maturation of Nervous system in infant
PNS: myelination begins in motor roots then sensory
CNS: myelination in sensory system precedes that of motor systems
*incomplete myelination
incomplete myelination can be seen in which CNS responses in infants?
Moro + Palmar Grasp Reflex
Myelination is not complete until what age?
3 years old
Moro Reflex
Response to sudden loss of support, when infant feels as if it is falling:
- spreading out arms (abduction)
- unspreading the arms (adduction)
- Crying
* present in newborns until 3-4months
Palmar Grasp Reflex
Object placed in infants hand, palm of child stroked, fingers close reflexively
-object is grasped
Which muscles are more easily depolarized in infants?
Immature
d/t prolonged opening of ion channels.
*risk of diaphragm - susceptible (fewer Type I fibers)
Which NMBs are effective in infants? Why?
increased ECF + ____
(NMBS = highly H2O soluble)
- increased sensitivity to NDMR
= normal dose
*Prolonged DOA (immature clearance) - normal sensitivity to Sux
= increased dose
Sux dose
2mg/kg IV
4mg/kg IM
Postop apnea Tx
Caffeine 10mg/kg IV
Risk of pain in neonate
HTN + immature cerebral autoregulatory response + fragile cerebral vasculature
=risk of intracerebral hemorrhage +pHTN
most damage from anesthesia occurs when?
during maturation periods when synaptogenesis rapidly occurs
*in utero: post 20 weeks
Infants/Kids: Conus medularis terminates between
L2 and L3
Age 8: L1
Nerves within spinal cord mature until completion at age
6-7
Dural sac ends between _____ in kids?
Between S2-S3 until 6 years old
Brain size in infants
2x size by 6m old
3x size by 1y/o
Maturation of cerebral cortex + brainstem is nearly complete by what age
1 y/o
Anterior fontanelle closes by
2 y/o
Posterior fontanelle closes at
4 months
Blood brain barrier in infants
immature until 1 y/o
Higher permeability
What should be avoided in neonates d/t their BBB immaturity?
Hypertonic solutions
-can damage cerebral vessels, prone to intracranial bleeding (+ hypoxia, hypercarbia, hypo- or hyperglycemia, swings in BP)
Primary fuel for brain
Glucose
major source of morbidity in infants
hypoglycemia
s/s hypoglycemia in infants
jitteriness, cyanosis, lethargy, hypotonia, apnea, HOTN, bradycardia, convulsions, brain injury
Why are neonates at higher risk for hypoglycemia?
Decreased stores of glycogen
CBF in premature infant
40mL/100g/minute
CBF in older children
adult level
100mL/100g/minute
Loss of cerebral autoregulation may occur in infants due to?
- hypoxia
- severe hypercapnia > 80 mmHg
- BBB disruption (head trauma, hemorrhage, cerebral ischemia)
- after admin of IAs or vasodilators (SNP)
Bradycarda in infant, Tx focuses on
1st hypoxia
-treat laryngospasm, post-extubation croup, bronchospasm, aspiration, inadequate O2, pneumothorax
Drugs that may cause bradycardia in infants
Sux, anticholinesterases, IAs
Neurogenic causes of bradycardia in infants
Oculocardiac reflex
Metabolic causes of bradycardia in infants
Hypoglycemia, anemia, hypothermia, acidosis
Infancy: Autonomic Nervous System
PNS > SNS
SNS in infants develops when?
4-6 months old
Infants: renal system considerations
“obligate sodium losers”
- unable to conserve sodium
- cannot fully respond to aldosterone
- decreased GFR + concentration ability
When are infants kidneys developed?
70% mature by 1 month
Adult level by 1 year old
Infants have low GFR due to?
- decreased systemic arterial pressure
- increased renal vascular resistance
- decreased permeability of the glomerular capillaries
infant PO requirement
150mL fluids/kg/day
Infants cannot reduce urine output below
1mL/kg/hr
What may occur if hypoglycemia in preterm neonates is not treated?
Neurologic damage
Increased risk of hypoglycemia if infants are
- premature
- SGA
- infants of diabetic mothers
Which other electrolyte may be off in babies?
Calcium
*risk of hypocalcemia
Hypocalcemia is common in infants who are
- premature
- SGA
- asphyxiated
- offspring of diabetic moms
- offspring of mothers who received transfusions with citrated blood or FFP
Explain the process of glycogen synthesis in the infant
Fetal liver synthesizes glycogen
- w/in first 48h of life, 98% of stored glycogen is released from liver
- glycogen levels not restored until 3weeks old
- SGA/preterm = susceptible to hypoglycemia
Fetal hepatic system - effect on Rx
Immature Phase II liver enzymes
-Rx metabolized by P450 = prolonged elimination half life
Fetal hepatic system - why is jaundice seen?
Decreased glucuronyl transferase activity
enzyme responsible for breakdown of bilirubin
Fetal hepatic system - effect on protein and drugs
-lower total protein
*albumin + alpha-1-acid glycoprotein (binds Rx) decreased
= decreased protein binding of Rx
= higher free drug concentration
When does the ability to coordinate swallowing with breathing take place?
4-5 months old
Upper intestinal abnormalities in infants present as
vomiting + regurgitation
Lower intestinal abnormalities in infants present as
Distention + failure to pass meconium
Why are neonates/infants at higher risk for hypothermia?
- Large surface area
- poor insulation
- small mass
- inability to shiver
What does cold stress cause in neonates/infants?
Increased O2 consumption + metabolic acidosis
In infants who cannot shiver, how do they stay warm?
Non-shivering thermogenesis (NST)
- increases heat production by 100%
- brown fat metabolism: high density of mitochondria, activated by norepi: acts on brown fat to uncouple oxidative phosphorylation
Majority of heat loss in babies is due to
Radiant Heat Loss
-transfer of heat to environment
Counteract radiant heat loss how?
- Preheat OR to 26 C
- Double shelled isolette during transport
- wrap neonate in warm blanket
- head = 60% total heat loss
What type of heat loss is due to a cold operating table?
Conductive
*also warm irrigation, blankets, bair hugger
What type of heat loss is due to air currents?
convection
What type of heat loss is due to wet clothing, liquid from body cavities/resp tract?
Evaporative
*vaporization of liquid from body to air
What is the most effective means of warming children?
Hot air blankets
Premature fluid compartment volumes: TBW, ECF, ICF
TBW: 80-90%
ECF: 50-60%
ICF: 60%
Infant fluid compartment volumes: TBW, ECF, ICF
TBW: 75%
ECF: 40%
ICF: 35%
Child fluid compartment volumes: TBW, ECF, ICF
TBW: 65-70%
ECF: 30%
ICF: 40%
Adult fluid compartment volumes: TBW, ECF, ICF
TBW: 55-60%
ECF: 20%
ICF: 40%
Volume of distribution equation
Dose of drug/plasma concentration
Lipid soluble drugs in infants = _____ plasma concentration
higher
Water soluble drugs in infants = ______ plasma concentration
lower
Pharmacokinetics - infants cardiac output effects this how?
Higher CO = faster drug delivery + removal
Albumin binds to ____ Rx
acidic
AAG binds to _____ Rx
Basic
Highly protein bound drug
Lidocaine
Highly protein bound drugs will have what effect in infants?
greater free fraction of drug, potentially greater pharmacological effect…. narrow therapeutic index (high risk of toxicity) –> reduce the dose!
Water soluble drugs
NMBDs
How is acetaminophen, chloramphenicol, and sulfonamides metabolized in neonates?
Reduced enzyme activity …
Neonates lack the capacity to effectively conjugate bilirubin (decreased glucuronyl transferase activity)
*same enzyme needed to metabolize these Rx
Drugs with prolonged half lives in neonates/infants
bupivacaine (25 hrs) mepivacaine (8.5 hrs) diazepam (100 hours) indomethacin (15-20 hours) meperidine (22 hours) phenytoin (21 hrs)
Which drugs may be effected in infants due to their immature enzyme activity?
LA, sux, atracurium, cisatracurium, esmolol
oral/rectal drug administration relies on ______ for absorption
passive diffusion
Rectal administration of drugs: superior rectal veins empties into
portal system
Rectal administration of drugs: middle/inferior rectal veins empties into
IVC (systemic circulation)
oral drugs degree of ionization depends on
gastric/intestinal pH levels
Oral drugs degree of ionization depends on gastric/intestinal pH levels. Acidic drugs are ____
- non-ionized
- favored absorption in stomach
Oral drugs degree of ionization depends on gastric/intestinal pH levels. Basic drugs are ____
absorbed in the intestines
Upper 1/3 of rectum - superior rectal veins
Which Rx avoid this area?
Avoid opioids + midazolam
*acetaminophen okay to give there
Rapid equilibrium of IAs in infants d/t
- increased ventilation (relative to FRC)
- increased cardiac output
- decreased solubility of IA
Neonates have _____ MAC but ____ at ___ days
lower MAC but peaks at 30 days
intracardiac shunts will cause what during induction (inhaled)?
prolonged time (R to L shunt)
FA/FI ratio is affected by
delivered IA concentration, IA blood-gas coefficient, alveolar ventilation, cardiac output, distribution to vessel rich (heart, brain, liver, kidneys)
Why may IV agents have a prolonged DOA in infants?
decreased muscle/fat (therefore less redistribution)
Highly ionized, low lipophilicity, limited ability to cross BBB
Neuromuscular blocking drugs
Which NMBD are infants more resilient to?
Sux
*only used in emergencies < 12 y/o d/t severe hyperkalemia risk in undx myopathies
Important rule of NMBD
ALWAYS reverse
Which system in infants is inhibited by anesthesia?
RAAS - renin angiotensin
Neonate maintain urine osmolality between
200-400 mOsm/L
Neonate specific gravity should be maintained
1.006-1.012
Neonate normal serum osmolality
270-280 mOsm/kg
Neonate on TPN - what fluids to give?
continue or infuse dextrose solution + monitor BG
NPO requirements - breast milk
4 hours
NPO requirements - clear liquids
2 hours
NPO requirements - formula
6 hours
Preterm + SGA neonates glucose requirement
8-10 mg/kg/min to prevent hypoglycemia
If preterm or SGA neonate becomes hypoglycemic intraop, Tx?
D5 or D10 solution followed by 10-15% Dextrose solution titrated to serum BG > 40 mg/dL
electrolyte abnormality d/t excess water loss in infants
hypernatremia
electrolyte abnormality d/t respiratory alkalosis/aggressive diuresis
hypokalemia
Hyperglycemia in neonate/infants intraop may lead to
intraventricular hemorrhage, osmotic diuresis, dehydration, release of insulin –> hypoglycemia
How to estimate blood loss from neonate/infant
1gm sponge weight = 1 mL blood loss
Which should be transfused at higher Hgb levels: neonate, infant, child?
Neonate
Most common cause of cardiac arrest in noncardiac procedures
hyperkalemia
What will reduce the risk of hyperkalemia d/t blood transfusion in neonate/infant?
Fresh ( < 1 week old)
Washed blood
Radiated
pRBC NOT whole blood
Which patient population should receive irradiated blood?
Immunocompromised patients
Electrolyte abnormality seen in blood transfusions
hypocalcemia
d/t citrate in blood
= CV instability