Peds Flashcards
How to calculate Postgestational age (PGA).
(# weeks gestation @ birth) + (current age in weeks)
Former Premature infants up to 60 weeks PGA are at an increased risk for?
post operative apana and bradycardia, requiring postoperative monitoring and admission
Which peds patient is in the most vulnerable peds population?
Extrememly low gestational age (ELGAN): 23-27 weeks gestation – all organs immature
low birth weight
<2500 grams
ALL pre terms have potential for:
- respiratory distress
- apnea
- hypoglycemia
- electrolyte disturbances (dec Mg, Ca)
- infection
- hyperbilirubinemia
- polycythemia
- thrombocytopenia
Fetal circulation has ____ pulmonary vascular resistance and ____ systemic vascular resistance.
high; low
At birth, explain the primary changes that occur in circulation
- ductus venosus closes, ductus arteriosus closes (due to increased PaO2)
- pulmonary vascular resistance decreases
- pulmonary vascular resistance increases
- foramen ovale closes
Explain the significance of only a “functional closure” of the foramen ovale and ductus arteriosus at birth.
Because they are only “funcitonally closed” and not “anatomically closed”, this means they can reopen.
For the first several weeks, the infant is undergoing transitional ciruclation. List events that can lead to increases in pulmonary artery pressures and subsequent implications.
- hypoxia, hypercapnia, hypothermia can lead to increased PAP
- this can lead to reversal of flow through foramen ovale, re opening of ductus arteriosus & shunting
- **this hypoxia is difficult to correct**
Structural differences of the newborn heart and subsequuent implications.
- structurally IMMATURE
- fewer myofibrils
- sarcoplasmic reticulum immature
- cardiac calcium stores are reduced – GREATER DEPENDENCY ON SERUM IONIZED CA++
Explain compliance of the newborn heart and subsequent implications.
- because the cells are immature, ventricules are less compliant (don’t get as much stretch) – CO IS HR DEPENDENT!
- consider frank starling curve – in a child, don’t have the ability to increase their compliance and stroke volume is “RELATIVELY” fixed – fluid CAN make a difference, but you only have a small window in which fluid will make a difference.
Discuss the baroreceptor reflex in the neonate and subsequent implications
- inability to substantially compensate for hypotension with reflex tachycardia
- keep in mind that hypotension for a child is a very late sign of hemodynamic compromise!!
Appropriate BP calculations for a child NOT under anesthesia (discussed in class)
- min. SBP for a neonate without anesthesia: 70 mmHg
- min. SBP for ages 2 - 10: 70 mmHg + age x 2 (I.e. 5 year old – 70 + (5x2) = 80 mmHg)
- >10 years old: min SBP 90 mmHg
Leading cause of bradycardia in children.
Hypoxia (99.9% of the time)
**so anytime you see a child’s HR drop, you should first think about oxygenation and ventilation!!** – open the airway, clear an obstruction, and give 100% oxygen
Autonomic nervous system in the neonatal heart: tend to have ____________ dominance; SNS is _________.
parasympathetic dominanace; SNS is immature
**tendency to have bradycardia with suctionaling and laryngoscopy**
Resting CO: neonate @ birth
~400 ml/kg/min
Resting CO: infant
200 ml/kg/min
Resting CO: adolescent
100 ml/kg/min
General overview of CV considerations
- dependence on ionized calcium: particularly vulnerable to effects of citrated blood products
- neonatal myocardium is not as compliant compared to an older child: increased preload does increase SV to the same degree
- hypovolemia and bradycardia produce dramatic decreses in CO that threaten organ perfusion
- Epinephrine rather than atropine increases contractility AND HR: preferred treatment of bradycardia and decreased CO
Pulmonary system: alveoli increase in number & size up until age ___.
8
Pulmonary system: why do infants have increased airway resistance?
small airway diameter
Discuss chest wall compliance, airway complicance, muscle fiber maturity, and subsequent implications.
- highly compliant airway & chest wall - MORE COLLAPSBILE – will see retactions under distress
- eartly fatigue and diphragmatic & intercostal muscles until age 2 (type 1 muscle fibers (slow twitch) not mature)
O2 consumption is _____ the adult with increased alveolar ventilation.
2 - 3 x’s
What is an anatomical difference of the right mainstem bronchus and important implications.
- ANGULATION of right mainstem bronchus – more likely to cause right mainstem intubation
- So anytime you have a position change, turning, or head movement with a pediatric patient, recheck tube position
- **in a neonate, flexing the head can push the tube into right mainstem intubation and extenstion can extubate!!**
oxygen consumption: neonate and adult
- neonate: 6 ml/kg/min
- adult: 3.5 ml/kg/min
alveolar ventilation: neonate and adult
- neonate: 130 ml/kg/min
- adult: 60 ml/kg/min
respiratory rate: neonate and adult
- neonate: 35 bpm
- adult: 15 bpm
tidal volume: neonate and adult
- neonate: 6 ml/kg
- adult: 6 ml/kg
**note tidal volume is consistent across age**
List anatomical differences of the infant airway.
- larger tongue in a smaller submental space - HARDER TO GET A VIEW
- high larynx (C2 to C4) - more “anterior view”
- omega shaped epiglottic - narrower; more difficult to lift - CLASSICALLY, USE MILLER BLADE
- angled vocal cords (slant caudally)
- funnel shpaed larynx with narrowest region @ cricoid ring
- okay to use cuffed ETT as long as monitoring pressures
- size down 1/2 size when using cuffed ETT
- obligate nasal breathers
- large occiputs – the “sniffing” position is favored for axis alignment - but NOT hyperextended
- edentulous - be sure to assess for presence of natal teeth (these would be easy to dislodge
- short trachea (4-5 cm)
Anatomical differences in the infant airway (APEX chart)
Gas flow: turbuelent airflow is present up to the ___ bronchial division; a 50% reduction in radius increased the pressure ___ fold. What does this mean for AW management?
5th; 32
- Very prone to respiratory distress with any upper AW irritation and swelling – GIVE STEROIDS LIBERALLY WITH AW EDEMA – also, keep in mind that steroids do not have a quick onset so give steroids early on.
- also, consider the what is causing the AW swelling - maybe consider racemic epinephrine vs albuterol - goal is not bronchodilation, but a reduction in swelling
Child O2 brain consumption vs adult.
- child: 5.5 ml/100 g/min
- adult: 3.5 ml/100 g/min
Child CBF vs adult
- child: 70-110 ml/min/100 g
- adult 50 ml/min/100 g
Discuss Anesthesia Induced Developmental Neurotoxicity
- knowledge is still growing in this area
- increased and accelerated neuroapoptosis with virutally all anesthetics (IV and VA)
- single exposures of short duration are usually of no consequence
- repeated &/or prolonged exposures at a young age (< 3 - 4 years (when synaptogenesis is still taking place)) may be associated with later behavioral & learning difficulties - we dont have conclusive evidence
- current thought is to delay non urgent and elective surgeries until age < 3 - 4 years.
The nervous system is _______ complete at birth, but _______ immature.
- anatomically; functionally
- myelinization & synaptic connections NOT complete until age 3-4 years (7 years of age per cote) – rapid growth of brain in first 2 years of life
Anterior fontanel closed by ______.
18 months
Posterior fontanel closed by ______.
~ 2 months
Discuss fontanel assessment and importance.
- can help you determine hydration status, or information about hydrocephalus
- important to assess appropriate fontanel opening/closure at certain ages (I.e. if 6 month old baby has synostosis of cranial vault, would notify surgery team and likely cancel surgery for further assessment) – imporant for brain to have room for growth up until typical fontanel closure timelines
Discuss somatic pain in the neonate.
How is the pain conveyed?
Are fibers mature?
Do neonates have suppresses or exaggerated response to nociceptive stimuli?
- somatic pain: conveyed in part by unmyelinated C fibers (“slow”)
- leads to protective relfexes such as autonomic reactions, muscle contraction, and rigidity
- C fibers are fully functional from early fetal life onward
- connections between C fibers and dorsal horn neurons are not mature before the second week of postnatal life but nociceptive stimualtions transmitted to the dorsal hortn by C fibers elicit long lasting responses
- probably as a result of extensive depolarization to the prodcution of large amounts of substance
- inhibitor control pathways are immature at birth and develop over the first 2 weeks
Explain the importance of pre remptive analgesia in the neonatal period.
- painful procedures during the neonatal period modify subsequent pain responses in infancy and childhood
- pre emptive analagesia leads to a reduction in the magnitude of long term changes in pain behaviors
What does FLACC stand for?
- faces
- legs
- activity
- cry
- consolability
General neuraxial considerations for the neonate: spinal curvature and timing of neuraxial
- lack of a lumbar lordosis compared to older children predisposes the infant to high spinal blockade with changes in positioning
- generally do neuraxial anesthesia AFTER GA, unlike in adults
Neuraxial considerations: discuss landmark differences of the conus medullaris, dural sac, and intercristal line.
- conus medullaris ends at approximately L1 in adults (migrates to L1-L2 by age 3)
- ends at L2 - L3 in neonates (level L3 @ birth)
- in infants, the line across the top of both iliac crests (the intercristal line) crosses the vertebral column at L4-L5 or L5-S1 interspace, well below the termination of the spinal cord
- dural sac in neonates and infants also terminates in a more caudad location compared ot adults, usually at about the level of S3 compared to the adult level of S1
Describe the functionality of GFR in the neonate and timeline of full maturation. What does this mean for your anesthetic?
- GFR is significantly impaired at birth but improves throughout 1st year
- greatest impairment is in 1st 4 weeks of life
- renal maturation will be delayed further with prematruity
- half life of medicacations excreted by glomerular filtration are prolonged in the very young
****GFR immaturity is important in drug selection for drugs that rely on renal clearance**** – remifentanil is a good choice for immature GFR because plasma esterases are fully functional in the neonate
Decribe ther functionality of renal tubular concentrating abilities and timeline for full maturity. What does this mean for your anesthetic?
- renal tubular concentrating abilities do not achieve full capcity until ~2 years
- very premature infants easily bcome hyponatremic because of reduces proximal tubular reabsorption of sodium and water and reduced receptors for hormones that influence tubular sodium transport
Liver: enzyme systems are still developing up until ___ year/years of age.
1
Liver: Phase I cyp 450 system is ____% of adult values at birth.
50%
(phase 1 reactions are responsible for the majority of drug metabolism in the liver via the CYP 450 enzyme systems (3A4 ~50% of drugs & 2D6 10 - 20%)
Liver: Phase II (conjugation reactions) are _________ in neonates. What does this mean for your anesthetic?
impaired
(phase II - conjugation reaction makes drugs more water soluble to facilitate renal excretion)
- long half life of BZD and morphine
- decreased bilirubin breakdown due to reduction in glucuronyl transferase (leading to jaundice) – glucuronyl transferase also needed for metabolism of tylenol (can easily develop acetaminophen poisoning)
Liver: hepatic synthesis of clotting factors reach adult levels within _____ week/weeks of birth.
one week
- at birth, vitamin K dependent factors (I.e. II, VII, IX, and X) are 20 to 60% of adult values
- in preterm infants, the values are even less
Liver: Discuss albumin levels/protein levels in the neonate and subusequent anesthetic implications.
- lower levels of albumin/other proteins for drug binding in newborns
- LARGER PORTION OF UNBOUND DRUG CIRCULATING
Liver: discuss glycogen stores in the neonate and subsequent implications.
- minimal glycogen stores - PRONE TO HYPOGLYCEMIA
GI: Important pearl to note about poor feeding/FTT in the infant.
Poor feeding equates to poor aerobic activity in infant. An infant that cannot feed well is equivalent to an adult that can’t walk out to their mailbox.
GI: coordination of swallowing with respiration is not mature until ________ months of age. What does this mean for the neonate?
4-5 months of age
**high incidence of refulx especially in preterm infants**
Compare and contrast the GI tracts of children and adults.
- gastric juices are less acidic (more neutral) up to ~3 yrs
- absorption of oral meds is generally slower compred to adults
- GI tract is generally slower in children compred to adults.
- adults have a larger GI tract, faster emptying time, and more protein transporters, which all cause an increase in absorption compared with children
- children have differences in gastric pH, emptying time, intestinal transit, immaturity of secretions, and activity of both bile and pancreatic fluids
Thermoregulation: list 4 ways you can lose heat and give an example of each.
- conduction (3%) - IV fluid
- evaporation (24%) - mask ventilation with gases from machine
- convection (34%) - air stream across exposed skin
- radiation (39%) - putting off body heat out into the environment
Explain difficulties of thermoregulation in neonate.
- large surface area to body wt
- lack of SQ tissue as an insulator
- inability to shiver: metabolize brown fat to increase heat production; can lead ot metabolic acidosis & increased O2 consumption
List mechanisms to actively warm.
- warm the OR
- use a warming mattress
- use incubators (when kid in NICU/PICU)
- cover with blankets
- head coverings (up to 60% of heat loss)
- transport in isolette
- humidy gases (HME exchanger?)
- use plastic wrap on the skin
- warm prep & irrigation solutions
- change wet diapers
- remove wet clothing
- forced air warmers - MOST EFFECTIVE STRATEGY TO MINIMIZE HEAT LOSS IN SURGERY IN CHILDREN > 1 HR
How do anesthetics alter thermogenesis in the neonate?
- alter non shivering thermogenesis
List mechanisms for appropriate temp monitoring in pediatric cases.
- core temp best measure; mid esophageal probe placed
- advantage to axillary temp if properly positioned: proximity to deltopectoral group improves recognition of elevated temp in MH
- 10 MH episodes occurred that were unrecognized with forehead temp
**TEMP MONITORING ESSENTAIL FOR ALL PEDS CASES**
Discuss problems associated with hypothermia and hyperthemia.
- HYPOTHERMIA
- delayed emergence
- reduced degradation od drugs
- increased infection
- decreased perfusion to new anastamoses/wounds
- HYPERTHERMIA
- suspect MH until proven otherwise
Discuss body composition of the neonate compared to adults. What does this mean for Vd, dosing, and excretion of drugs
- TBW is highest in premature infants & decreases with age
- water soluble drugs have a larger Vd
- need a larger initial dose of succ and dose/kg of abx
- larger Vd can delay excretion
- half life of meicatiosn in >2 years of age is hsorter than adults or equivalent due to significant CO to liver & kidneys (remember GFR is mature at this point)
Discuss body composition (fat + muscle) and associated drug effects.
- neonates hae less fat & muscle
- drugs that depend on redistribution to fat for termination of action will have prolonged effects (I.e. propofol, more dependent on this factor with infusion vs one time dose)
Discuss protein binding in the neonate and associated effect of drugs.
- < 6 mo old have reduced albumin & alpha 1 glycoprotein
- higher free fraction of protein bound drugs
- free fraction of lidcoaine will be higher in the very young
- acidic drugs (diazepam, barbs) tend to bind mainly to albumin
- basic drugs (amide local anesthetic agents) bind to globulins, lipoproteins, and glycoproteins
At what age do infants have a physiologic anemia. Why?
2 - 3 months of age - fetal hemoglobin is being replaced with adult hemoglobin from 3-6 months – happens gradually over time
How do we dose 1 unit of PRBCs inthe infant? What increase do we expect to see in both hgb and hct?
5 ml/kg to increase hgb 1 g/dL and hct about 3%
Calculation: maximum allowable blood loss calculation
MABL = EBV x (starting hct - target hct (lowest hct you’ll allow))/starting hct
**remember, we don’t reach MABL before we start thinking about blood (have to think about rate of blood loss, how easy of a time the surgeon is having a gaining hemostatic control, the trajectory of future blood loss in the case)**
Transfusion threshold for neonates.
40% instead of 30% related to L shift, decreased CV reserve, higher CBF, increased O2 consumption
In which neonatal populations do we consider blood sooner and why?
- preterm infants
- term newborns
- children with cyanotic congenital heart disease
- those with respiratory failure in need of high O2 carrying capacity
Carry an increased risk for post operative apnea and respiratory complications when anemic – not even entirely sure why.
Normal hgb/hct values (chart)
Estimated blood volume – EBV cc/kg (chart)
Neonates have _______ susceptibility to infection: related in part to _______ of leukocytes.
increased; immaturity
Describe the components of CLASSIC fluid replacement.
- fasting (NPO) deficit (maintenance rate x hours of NPO for deficit)
- baseline maintenance fluid requirement - using LR in most cases (4, 2, 1)
- replacement of blood loss - (3:1 crystalloid replacement; 1:1 blood or colloid replacement)
- evaporative losses - (based on invasiveness of sx)
Fluid replacment of 75-100 ml/kg may encounter _____________.
dilutional coagulopathy
Describe how to calculate fluid repalcement using the Holliday - Segar formula: 4:2:1. (chart)
Describe the new trends of intra operative fluid management.
- new guidelines are recognizing the impact of ADH secretion on fluid status
- simple stategy for healthy children undergoing elective sx
- administrations of 20-40 ml/kg of crystalloid (balanced salt solution) over the duration of the case
- takes into account maintenance fluid as well as NPO deficit
- administrations of 20-40 ml/kg of crystalloid (balanced salt solution) over the duration of the case
Describe the new trends for fluid managment in the post operative period.
- new 2 - 1 - .5 rule applies (2 ml/kg for the first 10 kg, 1 ml/kg for 10-20 kg, and 0.5 mlg/kg for each kg above 20 kg in weight)
- this therapy now recognizes the common dysregulation of ADH seretion after sx and prevents hyponatremia
- If NO oral intake after 12 hours, then D5 0.45% saline should be given using the 4 - 2 - 1 rule.
Fluid Replacement: how can you minimize potential for error?
- smaller IV bags
- buretrols
- eliminate all air from IV line
Which pt populations may require glucose contian IVF?
- infants < 6 months
- at risk for hypoglycemia
- children with mitochondrial disease
**only D51/2NS for maintenance rates!!, LR for the rest**
How do manage TPN rates regarding fluid managment?
- TPN should not be stopped suddenly
- circulating insulin levels have acclimated to this basal infusion of glucose & hypoglycemia will be problematic
- either continued in OR or ramped down & bridged with glucose containing IVF (ok to stop lipids)
- deduct this from hourly maintenance calculated rate
- some do cut back to 1/3 or 1/2 due to the increase in glucose released d/t surgical stress - if you choose to do this then be sure to monitor glucose
What is the best way to measure dehydration/fluid deficit in infants? List the effects at mild, moderate and severe dehydration.
WEIGHT
- mild - 50 ml/kg deficit
- dry mouth, poor skin turgor
- moderate - 100 ml/kg
- mild sx plus suken fontanel, oliguria, tachycardia
- severe - 150 ml/kg
- moderate sx plus sunken eyes, hypotension & anuria
Questions to consider with intra operative fluid managment.
- Is the HR persistently increased or does It vary with surgical stimulation?
- Is the pulse pressure narrow or more ominously, is teh BP reduced for age?
- Does It vary with positive pressure breaths?
- Are the extremities warm?
- Is capillary refill brisk?
- What is the u/o?
- Are these variables changing?
- What is the rate of change?
WHEN HYPOVOLEMIA IS SUSECTED, OBSERVING THE RESPONSE TO A 10 - 20 ML/KG BOLUS OF ISOTONIC CRYSTALLOID OR COLLOID MAY TEST THE HYPOTHESIS.