First Lecture by Dr Albert Flashcards
Why is surface area a special concern in pediatric anesthesia?
Because it parallels metabolic rate
What are some physiologic differences between adults and children?
- Head size
- Airway/respiratory
- Cardiovascular
- Temp regulation
- liver
- Kidney
- Fluids and electrolytes
- pharmokinetics
What is different about the pediatric head/neck?
large head compared to adult
weak neck muscles
short neck
What is different about the airway of the pediatric pt?
- narrow nasal path
- small mouth
- large tongue
- narrow/floppy epiglottis (omega shaped)
- epiglottis is higher (c3-c4 vs c4-c5 in adult)
- sloping cords
- funnel shaped
- Narrow cricoid ring
What are some differences with the pediatric rids?
- They are more horizontal and less mechanical (don’t expand as well as adults)
- Cage is more cartilage and more pliable
Peds have a higher amount of Type II muscles vs Type I muscles in the chest. What is the difference?
Type I muscles are for endurance and Type II will fatigue quickly when stressed.
How many arteries and veins are in the umbilical cord?
2 arteries and 1 vein
What is different about fetal hemoglobin?
Has a higher affinity for O2 (low 2,3 DPG), therefore it does not release oxygen at the tissue level well.
How is the fetal heart different than an adult?
Fetal heart is 30% contractile mass vs 60% in adults - lower contractile mass results in lower compliance.
How do infants increase cardiac output?
by increasing HEART RATE
In the newborn, what variable does not change, HR, SV or CO?
Stroke volume - newborns have low cardiac mass –> lower compliance –> Frank-Starling mechanism is not functional. To increase CO in infants, you must increase HR.
What are some efferent responses to cold in an infant?
- Behavioral (unable to do this like pulling up blankets)
- Vasoconstriction (not highly effective)
- nonshivering thermogenesis
- shivering
What is brown fat? When does it develop and when is it gone?
Brown fat helps keep babies warm and can double their metabolic heat production.
- develops ~ 26-30 wks and is gone by 2 yrs.
What’s the afferent input for warm/cold sensation?
A-delta fibers (most cold fibers)
C (most warm fibers)
How is hypovolemia manifested in newborns?
hypotension without tachycardia
The pediatric pt’s major mechanism for heat production is?
NONSHIVERING THERMOGENESIS (per Valley review)
An appropriate blood pressure for a term neonate would be?
65/40
why can’t newborns shiver?
maybe due to immaturity of musculoskeletal systems.
Maybe due to small muscle mass - shivering would be ineffective.
What is the maximum amount of heat loss prevented by vasoconstriction?
25-50% - this could take hours to reach this amount of heat loss.
What are the 4 major routes of heat loss/transfer?
Radiation (39%)
Convection (37%)
Evaporation (21%) - increased with surg prep
Conduction (3%)
What are some anesthesia effects on heat loss?
- Lower threshold - more loss of temp before body attempts to compensate
- vasoconstriction begins @ 34-35 C vs 36.7C
- Nonshivering thermogenesis inhibited
- Post anesthesia shivering not applicaple in infants
How much can 1 unit of PRBC or 1 Liter of fluids at room temp decrease your body temp?
0.25 degrees C
What are some intraoperative strategies to maintain body heat?
- heat and humidify gases
- Cutaneous heating like lamps, water blanket, forced air blanket, raise room temp
- Warm IV fluids (prevents loss of heat)
when is an infant’s liver function usually functional? Mature?
Functional - 1-2 wks (postnatal)
Mature - 6-12 months
*enzyme function r/t postnatal age NOT gestational age
What are the 3 steps to Phase I liver function?
Oxidation
Reduction
Hydrolysis
In phase I liver function - what does hydrolysis do to drugs?
turns fat soluble drugs to water soluble so they can be eliminated
After birth, when do the kidneys start functioning well?
Day 5 shows improved renal function. By 1 month kidneys are approximately 70% mature.
Most have mature kidneys by 3 months but could take up to 2 yrs
Do infants have a larger or smaller amount of body fluid?
Larger amount - Approx 80% vs 60% in adults
Since infants have an increased metabolic rate, does that mean they metabolize water quicker, too?
Yes. They also have an increased risk of metabolism
What is a normal K+ level in newborns?
5 to 6.5 vs 3.5 to 5 in adults
If an infant’s K+ is 3 to 3.5 with GI loss, is this a problem?
yes. would need rehydration and replacement of electrolytes prior to surgery
Do infants have good gastrointestinal uptake of drugs?
No. Enzyme levels mature over first 3 months of life.
For inhalation agents, put the groups that have the highest to lowest MAC. (Adult, children or newborns)
Newborns»_space; child > adults
Why do newborns have a higher uptake of inhalation agents?
- increased HR
- Decreased FRC and increase Vt
- Increased tissue perfusion
Know how to calculate fluids using the 4:2:1
0-10 kg - 4 ml/kg/hr
11-20kg - 2ml/kg/hr + 40 ml
>20kg - 1ml/kg/hr + 60
What is the approx. blood volume of a premature infant?
100ml/kg
What is the approx. blood vol of 0-2 yr old
80ml/kg
What is the approx. blood vol of 2-16 yr old?
70 ml/kg
What is the formula for Allowable blood loss in children?
Kg x EBV x Hct initial - Hct Allowable / 100
How fast should you give fluid deficit to a pt?
1/2 deficit in first hr
1/4 deficit in 2nd and 3rd hrs
How much and when should you give fluids to replace 3rd space loss?
2-10ml/kg depending on the procedure and give over 2nd and 3rd hrs.
How much should you replace blood loss with crystalloids?
3:1. As you approach 70% of allowable blood loss, consider replacing 25% of blood loss with PRBC
How much urine output should you expect on an infant in surgery?
1-2ml/kg/hr
What is the best way to monitor cardiovascular stability?
Urine output
What are the 3 types of dehydration?
Isotonic
Hypotonic
Hypertonic
What is the most common type of dehydration?
Isotonic - can be caused by pyloric obstruction, upper and lower bowel loss, peritonitis, starvation
What are some causes of hypotonic dehydration?
Fever
Diarrhea
starvation
What are some causes of hypertonic dehydration?
burns
sweating
diarrhea
What is the most common cause of metabolic alkalosis in an infant?
Pyloric Stenosis
Is Pyloric stenosis usually an emergency?
No, rarely
What should be done for a child before they have surgical repair of pyloric stenosis?
correction of fluid balance, k+ level, and metabolic abnormalities
Why do kids with pyloric stenosis develop metabolic alkalosis?
from vomiting - leads to loss of H+, Cl and H2O.
What other electrolyte can be abnormal from emesis?
K+
