Unit 11 - Neonatal A&P Flashcards
normal VS for a newborn
SBP = 70
DBP = 40
HR = 140
RR = 40-60
normal VS for a 1year old
SBP = 95
DBP = 60
HR = 120
RR = 40
normal VS for a 3 year old
SBP = 100
DBP = 65
HR = 100
RR = 30
normal VS for a 12 year old
SBP = 110
DBP = 70
HR = 80
RR = 20
why do neonates have a higher RR than adults
- much higher O2 consumption & CO2 production vs adults
- Neonate must increase alveolar ventilation accordingly - metabolically more efficient to increase RR
primary determinant of cardiac output and systolic blood pressure in neonates
HR
Vt in neonates vs. adults
same on a per weight basis (6 mL/kg)
why do neonates rely on HR to maintain CO
The neonatal myocardium lacks the contractile elements to significantly adjust contractility or stroke volume
Non-compliant LV is sensitive to increased afterload
what defines hypotension in a newborn
SBP < 60 mmHg
what defines hypotension in a 1 yr old
SBP < 70 mmHg
what defines hypotension in a child > 1 yr
SBP < [70 + (child’s age in years x2)] mmHg
neonatal period
first 28 days of life
infant period
29 days to one year
what explains why a child becomes relatively less dependent on HR to support CO with age
SVR increases over time
* As the left ventricle pumps against a higher SVR, the contractile elements multiply and mature, giving the LV the ability to better adjust contractility
why do newborns respond to stressful situations (DL, suctioning) with bradycardia
ANS regulation of the heart is immature at birth - SNS is less mature than the PNS
preferred med in treating hypovolemia and bradycardia in neonates
epinephrine over atropine
epi has added benefit of augmenting contractility
why are neonates generally unable to increase HR in the setting of hypovolemia
baroreceptor reflex is poorly developed
how do s/s pain manifest in the neonate
activates SNS - tachycardia, HTN
why is neo generally a poor choice for treating hypotension in a neonate
neonates can’t significantly increase contractility to overcome increased afterload
factors that predispose neonates to intracranial hemorrhage with pain
pain = SNS response = tachycardia and HTN
combination of hypertension, an immature cerebral autoregulatory response, and a fragile cerebral vasculature
babies are preferential nose breathers until what age
5 months
how is an infant’s epiglottis different from an adult’s
infant’s is stiffer and longer
U-shaped or omega shaped
why is a more acute angle required to visualize the glottis in infants
shorter neck
cephalad larynx
larger tonge
why is sniffing position avoided in infants
tends to move laryngeal opening further from line of sight in DL
positioning an infant for DL
- Larger occiput flexes the neck when placed supine on a flat surface
- A shoulder roll helps align oral, pharyngeal, and laryngeal axes
why is it more difficult to displace the epiglottis of an infant during DL (vs. adult)
epiglottis is stiffer and longer
why is a miller blade preferred in infants
infant’s tongues occupy a relatively large area of mouth
helps to lift the tongue to better expose the pediatric larynx
level of newborn’s glottis
full term: ~C4
premature: ~C3
glottic opening in newborns vs. adults
adult glottis is at ~C5
newborn glottis is at ~C3-C4
higher glottic opening = more superior, cephalad, or rostral (not more anterior)
the only time an infant’s airway is more “anterior” is w neck flexion
why are infants at higher risk of upper airway obstruction vs. adults
tongue is closer to soft palate and more likely to obstruct
position of pediatric larynx
C3-C5
adult = C5-C6
position of pediatric larynx
C3-C5
adult = C5-C6
at what point does the pediatric larynx descend to C4
~1 year old
age pediatric larynx achieves adult position
by 5-6 yrs old
narrowest region of pediatric airway
dynamic = vocal cords
fixed = cricoid ring
changes in bronchi in children
up to 3 years of age, both bronchi take off at 55 degrees off the midline
situations that increase risk of cricoid edema in pediatric airways
- an ETT that is too large
- multiple intubation attempts
- prolonged intubation
- frequent head positioning while intubated
why do neonates require a comparatively higher alveolar ventilation to sustain normal arterial gas tensions vs. adults
Because the neonatal alveolar surface area is only 1/3 of the adult and basal oxygen consumption is 2 - 3 times that of the adult
when do distal saccules of the lung start to develop
24-28 wga
O2 consumption of neonate vs adult
neonate = 6-9 mL/kg/min
adult = 3.5 mL/kg/min
alveolar ventilation of a neonate vs adult
neonates = 130 mL/kg/min
adult = 60 mL/kg/min
FRC in neonates
slightly reduced
30 mL/kg vs. 34 mL/kg in adults
FRC in neonates
slightly reduced
30 mL/kg vs. 34 mL/kg in adults
why do neonates rapidly desaturate during hypoventilation or apnea
neonate’s relatively higher oxygen consumption will quickly exhaust the oxygen reserve contained in the FRC
also decreased FRC
why do neonates rapidly desaturate during hypoventilation or apnea
neonate’s relatively higher oxygen consumption will quickly exhaust the oxygen reserve contained in the FRC
also decreased FRC
why do neonates experience a faster inhalation induction vs. adults
Increased ratio of alveolar ventilation relative to the size of the FRC
primary muscle of inspiration
diaphragm
types of muscle fibers in diaphragm and intercostals
type 1 = slow-twitch, endurance
type 2 = fast-twitch, bursts of heavy work (tire easily)
predominant type of diaphragm muscle fibers in neonates
25% type 1
75% type 2
why are neonates at risk for resp fatigue and failure
The neonatal diaphragm only has 25% type 1 fibers (adults have 55%)
age that should be admitted for apnea monitoring after surgery
< 60 weeks PCA
post conceptual age
age that should be admitted for apnea monitoring after surgery
< 60 weeks PCA
post conceptual age
meds to reduce risk of postop apnea
caffeine 10 mg/kg
theophylline (higher risk toxicity)
lung and chest wall compliance in neonates vs adults
- decreased lung compliance d/t fewer alveoli
- increased chest wall compliance d/t cartilaginous ribcage
lung volumes that are decreased in neonates
FRC
VC
TLC
lung volumes that are increased in neonates
RV
CC
3 processes that support a neonate’s FRC
- Sustained tonic activity of inspiratory muscles
- Narrowing of glottis during expiration
- Shorter expiratory time with a faster respiratory rate creates end-expiratory pressure
why do neonates have increased WOB
a function of increased airway resistance (particularly in small airways)
ABG from umbilical vein
pH = 7.35
PaO2 = 30
PaCO2 = 40
ABG from umbilical artery
pH = 7.3
PaO2 = 20
PaCO2 = 50
ABG of mother at term
pH = 7.4
PaO2 = 90
PaCO2 = 30
ABG of newborn 10 min after delivery
pH = 7.2
PaO2 = 50
PaCO2 = 50
ABG of a newborn 1 hr after delivery
pH = 7.35
PaO2 = 60
PaCO2 = 30
ABG of a newborn 24 hrs after delivery
pH = 7.35
PaO2 = 70
PaCO2 = 30
supplies oxygen to fetus in utero
umbilical vein
what causes a newborn to breathe rhythmically after birth
Clamping of the umbilical cord
acute rise in PaO2 promotes continuous breathing
when do neonates develop a relatively normal FRC
in the first 20 minutes of life
why do neonates hyperventilate during the first hour of extrauterine life
likely due to its poor buffering capacity and compensation for nonvolatile acids in the blood
After this time, the pH and PaCO2 stabilize
why do neonates hyperventilate during the first hour of extrauterine life
likely due to its poor buffering capacity and compensation for nonvolatile acids in the blood
After this time, the pH and PaCO2 stabilize
when does neonatal respiratory control mature
42 - 44 weeks post-conceptional age
when does neonatal respiratory control mature
42 - 44 weeks post-conceptional age
how does hypoxemia affect neonates before and after respiratory control matures
- Before maturation: hypoxemia depresses ventilation
- After maturation: hypoxemia stimulates ventilation
P50 of fetal Hgb
19 mmHg
how does fetal Hgb affect the oxyhgb dissociation curve
shifts to the left
how does the low P50 of fetal Hgb benefit the fetus
creating an oxygen partial pressure gradient across the uteroplacental membrane that facilitates the passage of O2 from mother to fetus
composition of Hgb A vs Hgb F
Hgb A = 2 alpha and 2 beta chains
Hgb F = 2 alpha and 2 gamma chains
explains why Hgb F has a higher affinity for oxygen
does not bind 2,3-DPG since it has 2 gamma chains instead of 2 beta
the binding site fo 2,3-DPG is only on the beta chain
how does 2,3-DPG affect oxyhgb dissociation curve
right shift
lifespan of fetal RBCs
70-90 days
hgb at birth
17 g/dL
how long does it take for Hgb A to replace Hgb F
6 months - P50 at this time same as adult (26.5)
in 1st 2 months, erythrocytes containing Hgb F are replaced by those that produce Hgb A
what age is assoc with physiologic anemia in newborns
2-3 months
Hgb ~ 10 g/dL
age Hct begins to rise
4 months
erythropoesis increases, hgb concentrtation rises
age Hct begins to rise
4 months
erythropoesis increases, hgb concentrtation rises
when does P50 reach adult level
4-6 months old
RBC transfusion trigger < 4 mo
< 13 g/dL with severe cardiopulmonary disease
< 10 mg/dL in child presenting for major surgery or moderate cardiopulmonary disease
10 mL/kg of PRBCs will increase Hgb by ___
1-2 g/dL
PRCB transfusion practice guidelines for > 4 mo
- Transfusion is rarely indicated if Hgb > 10 g/dL
- Transfusion is almost always indicated if Hgb < 6 g/dL
- Transfusion should be considered on a need’s basis if Hgb is 6 - 10 g/dL
- The use of a universal transfusion trigger is not recommended
indications for neonatal FFP admin
- Emergency reversal of warfarin
- Correction of coagulopathic bleeding with increased PT or PTT
- Correction of coagulopathic bleeding if > 1 blood volume has been replaced and coagulation studies are not easily obtained
indications for plt admin in neonates
Recommended for invasive procedures to maintain the platelet count above 50,000
indications for plt admin in neonates
Recommended for invasive procedures to maintain the platelet count above 50,000
platelet transfusion dose if obtained from apheresis
5 mL/kg
neonatal platelet transfusion dose from pooled plt concentrate
1 pack/10 kg
single aphresis plt unit = ____ pooled concentrations
6-8
5 complications of massive transfusion in the neonate
- metabolic alkalosis or acidosis
- hypothermia
- hyperglycemia
- hypocalcemia
- hyperkalemia
P50 of hgb A
26.5 mmHg
purpose of fetal Hgb
facilitates passage of O2 from mother to fetus
Hgb F is compeltely replaced by Hgb A by what age
6 months old
why can giving neonates PRBCs cause hyperkalemia and cardiac arrest
When RBCs are stored, the cell membrane becomes dysfunctional, which allows potassium to leak into the supernatant
cause of graft vs host disease from PRBC transfusion in neonate
donor leukocytes attack recipient bone marrow
leads to pancytopenia, fever, hepatitis, diarrhea
prevention of graft v host disease from PRBC transfusion in neonates
irradiated blood
hgb & hct in newborn
Hgb 14-20 g/dL
Hcg 45-65%
Hgb & Hct in 3 month old
Hgb 10-14 g/dL
Hct 31-41 %
hgb & hct in 6-12 month old
Hgb 11-15 g/dL
Hct 33-42%
hgb & hct in 6-12 month old
Hgb 11-15 g/dL
Hct 33-42%
Hgb & Hct in adult female
hgb 12-16 g/dL
hct 37-47%
hgb & hct in adult male
hgb 14-18 g/dL
hct 42-50%
dose range for FFP
10-20 mL/kg
EBV of premature neonate
90-100 mL/kg
EBV of term neonate
80-90 mL/kg
EBV of infant
75-80 mL/kg
EBV of 1 year old
70-75 mL/kg
kidneys at birth vs. adult
immature at birth
* decreased perfusion pressure
* decreased GFR
* decreased diluting and concentrating ability
why are neonates intolerant of fluid swings
poor job conserving water - intolerant of fluid restriction
unable to excrete large volumes of water - don’t do well with overload
how do neonates lose most of their water
through evaporation
surface area to body weight ratio that is four times higher than the adu
how do neonates lose most of their water
through evaporation
surface area to body weight ratio that is four times higher than the adu
why do neonates lose most of their body water through evaporation (via skin)
- surface area to body weight ratio that is four times higher than the adult
- immature skin is thinner and more permeable to water
how long does it take for GFR to reach adult levels
8-24 months old
when does renal tubular function achieve full concentrating ability
~ 2 years of age
TBW in a premature neonate vs term neonate
preterm = 85%
term = 75%
why are neonates oligate sodium losers at birth
kidneys have an immature concentrating mechanism
when is TBW highest
at birth
decreases with age
when is TBW highest
at birth
decreases with age
when is ECF highest
at birth
decreases with age
when is ECF highest
at birth
decreases with age
when is ICF highest
lowest at birth and increases with age
in what age groups is ECF > ICF
neonates (premature and term)
when does TBW approximate adult values
by 1 yr old
4:2:1 rule for fluid replacement
first 0-10 kg = 4 mL/kg/hr
next 10-20 mg add 2 mL/kg/hr
> 20 kg add 1 mL/kg/hr to previous total
fluid replacement for third space losses
- Minimal surgical trauma = 3 - 4 mL/kg/hr
- Moderate surgical trauma = 5 - 6 mL/kg/hr
- Major surgical trauma = 7 - 10 mL/kg/hr
As a general rule, third-space loss is not included in the first hour of
fluid replacement for third space losses
- Minimal surgical trauma = 3 - 4 mL/kg/hr
- Moderate surgical trauma = 5 - 6 mL/kg/hr
- Major surgical trauma = 7 - 10 mL/kg/hr
As a general rule, third-space loss is not included in the first hour
when should glucose-containing fluids be used in neonates
reserved for infants and children at risk of developing hypoglycemia
* Prematurity
* < 48 hours of age
* Small for gestational age
* Newborns of diabetic mothers
* DM & received insulin on the day of surgery
* TPN dependent
at what glucose level do s/s hypoglycemia develop when < 72 hours old
30-40 mg/dL
at what glucose level do s/s hypoglycemia develop when > 72 hours old
< 40 mg/dL
treating neonatal hypoglycemia
IV 10% dextrose (2 mL/kg)
4 mL/kg if seizures present
after bolus, D10 gtt at 8 mg/kg/hr to maintain serum glucose > 40
CO in the newborn
200 mL/kg/min
why do neonates have a faster circulation time vs adults
increased CO (200 mL/kg/min)
MAC of sevo in a 3 month old
3.2%
why are neonates more sensitive to sedative-hypnotics
An immature BBB allows passage of drugs that would otherwise not be able to enter the brain
when do babies reach adult values of drug biotransformation
by 1 yr old
when is normal GFR achieved
8-24 months of age
when is normal tubular function achieved
age 2
dosing highly-protein bound drugs in infants
Before 6 mo, there are lower concentrations of albumin and alpha-1 acid glycoprotein, so for drugs that are usually highly protein-bound, the neonate will experience increased free drug levels and have a higher risk of toxicity
dosing water solube drugs in neonates
Neonates have a higher percentage of total body water, (higher Vd) so they require higher doses of water-soluble drugs to achieve a given plasma concentration
dosing drugs that require fat for redistribution in neonates
Neonates have a higher percentage of TBW and a lower percentage of fat and muscle mass. Drugs that require fat for redistribution and termination of effect have a longer duration of action
MAC changes in infancy
- Neonate (0 - 30 days): MAC is lower than the infant
- Premature: MAC is lower than the neonate
- Infant 1 - 6 months: MAC is higher than the adult
- Infant 2 - 3 months: MAC peaks at its highest level
MAC changes with age in infancy
- Neonate (0 - 30 days): MAC is lower than the infant
- Premature: MAC is lower than the neonate
- Infant 1 - 6 months: MAC is higher than the adult
- Infant 2 - 3 months: MAC peaks at its highest level
MAC of sevo in 6mo-12 yr old
2.5%
dosing succinylcholine in neonates
2 mg/kg
combination of an increased ECF and normal sensitivity to succinylcholine necessitates a higher dose
dosing succinylcholine in neonates
2 mg/kg
combination of an increased ECF and normal sensitivity to succinylcholine necessitates a higher dose
NMB that can cause HTN in neonates
pancuronium
black box warning on succinylcholine
warns of hyperkalemia (risk of cardiac arrest) associated with undiagnosed muscular dystrophy in children under 8 years old
first line treatment when child experiences cardiac arrest following succs admin
IV calcium is the first-line treatment
anytime a child experiences cardiac arrest following succinylcholine, hyperkalemia should be assumed until proven otherwise
dosing IM succinylcholine
- The dose for neonates and infants is 5 mg/kg
- Older children should receive 4 mg/kg
dosing neostigmine in neonates
0.05-0.07 mg/kg
dosing edrophonium in neonates
1 mg/kg
maximum inspiratory force (MIF) that predicts adequate NMB recovery in peds
less than -25 cm HO (e.g., - 30)
most common metabolic disturbance in newborns
hypoglycemia
children at risk of developing hypoglycemia
- premature
- SGA
- < 48 hours old
- newborns of diabetic mothers
- diabetics who received insulin DOS
- TPN dependent
neonate’s UOP in the first week of life
< 1 mL/kg/day
Compared to the adult, what 3 kidney functions are lower in the neonate?
- Renal perfusion pressure
- Glomerular fitration rate
- Diluting & concentrating ability
how do neonates lose most body water
evaporation
Why is so much body fluid lost through the skin of neonates?
- Surface area to body weight ratio is four times higher than the adult.
- Immature skin is thinner and more permeable to water.
why are neonates intolerant of both fluid restriction and overload
restriction: poor job of conserving water
overload: unable to excrete large volumes of water
neonates are obligate ____ losers in the first few days of life
sodium
consequences of glycosuria in the neonate
osmotic diuresis
dehydration
increased serum osmolarity (can cause ICH)
why does the erythrocyte transfusion trigger vary with age
depends on how much Hgb F the child has
In what age groups is ECF greater than ICF?
- premature neonates
- term neonates
What is the PO2 When fetal hemoglobin is 50% saturated by oxygen?
19 mmHg
10 mL/kg PRBCs estimated to increase Hgb by ___
1-2 g/dL
