20101008

Pediatric Anesthesia

Paturai

Free Download Via : 4Shared

Pediatric Anesthesia
Objectives
Physiologic differences
Preoperative evaluation
NPO requirements
Premedication
Anesthetic techniques
Important Concept
The pediatric patient is not a “small adult”
Pediatric Anatomy and Physiology
The Pediatric Airway
Varies greatly from neonate to teen
Neonatal Airway

  • small nares / nose breather
  • small mandible
  • small oral cavity
  • short neck
Epiglottis
  • long, narrow, stiff
Strong laryngeal reflex
  • apnea
  • bradycardia
  • laryngospasm
Neonatal Body Mass
Large body surface area to weight ratio

  • 1/9 BSA of adult
  • 1/20 weight of adult
  • 1/3 length of adult
Central Nervous System
Brain weight doubles at 6 mo. and triples by 1 year
Cells in cortex and brain system completely developed by 1 year
Myelinization complete by 3 years
Spinal cord

  • Birth L-3
  • 1 year L-1
PNS fully developed at birth
SNS developed at 4-6 months
Respiratory System
Lungs still developing at birth

  • Alveolar Ventilation is double in neonates to meet O2 demands
  • Achieve by high respiratory rate
Hypoxia and hypercarbia will depress respiratory drive in the infant rather than stimulate as in adults.
Neonate respiratory muscles are weak and fatigue easily
Infant versus Adult

  • lower FRC
  • lower closing volume
  • lower lung compliance (sm. Alveoli)
  • Greater chest wall compliance
  • O2 requirement 2x adult (6 ml/kg)
  • CO2 production 2x adult (ml/kg)
Cardiovascular
Change from fetal to adult circ.

  • foramen ovale closes
  • ductus venosis closes
  • ductus arteriosis closes
High cardiac output (ml/kg/min)
newborn CO = 4 ml/beat
Important: the main determinant of cardiac output up to age 2 is heart rate
Renal Function
Kidneys are immature at birth
continue to mature for 6 months
GFR increases 2x-3x in first 3 months
Pre term can not conserve sodium
ECF 40% of newborn body wt.
Hypovolemia - HR
Hourly Maintenance Fluids
4:2:1 Rule
4 ml/kg/hr 1st 10 kg +
2 ml/kg/hr 2nd 10 kg +
1 ml/kg/hr for each kg > 20
Maintenance Fluid Therapy
Term Newborn (ml/kg/day)
Day 1 50-60 D10W
Day 2 100 D10 1/2 NS
>Day 7 100-150 D5-D10 1/4 NS
Older Child: 4-2-1 rule


Normal Blood Volumes
Premature = 100 ml/kg
Full term = 85-90 ml/kg
Infant = 80 ml/kg
Adult = 65-70 ml/kg
Normal Hematocrit
Full term = 55%
3 months = 30%
6 months = 35%
Prolonged PT and PTT are common but coagulation is normal
Fetal Hemoglobin
Neonate = 60-90% HgB F
HgB F
– reduced 2,3 DPG
– O2 curve shifts left á Hg affinity for O2
– Impairs O2 release at the tissues
Offset by increased Hct
O2 curve at adult level by 4 months
Temperature Regulation
Infants lose heat rapidly
Infants do not shiver
– able to shiver by 1 year
Brown fat metabolism
– non-shivering thermogenesis
Prevention of hypothermia is essential
Infant Heat Loss
Greatest loss via radiation
– due to relatively large BSA
Hypothermia Causes:
– Increased oxygen consumption
– Increased PVR
– Increased SVR
– R to L shunting
Preventing Hypothermia
Heat the operating room
Use radiant heaters
Warming pad on bed
Cover the head (40% of heat loss)
Warm IV fluids
Humidify gases
Preoperative Evaluation
Pertinent maternal history, birth and neonatal history
Review of systems review
Physical examination; focus on cardiopulmonary problems
Always ask about medications and drugs allergies
Current status of the disease; require consultation with the pediatrician and other physician?
Congenital malformations
Previous anesthetics experience, discussion of anesthetic risk, anesthetic plans, postoperative analgesia
Address preoperative anxiety (child and parents)
Preoperative Evaluation
Preop Preparation
Pediatric anesthesia is a family affair.
Psychological preparation involves stress reduction
The two most important sources of stress are:
1. Fear of the unknown
2. Fear of separation
These stresses are best dealt with by:
Simple, honest communication
Maintain parental presence during induction of anesthesia in selected
cases.
Approach depends on age of patient :

Early infancy (neonate to about 7 months of age):
Parents are the primary focus
Gentle, comfortable separation is usual
Later infancy to about 3 years:
Separation anxiety major
Surgery ought be outpatient
Selected parental presence Gentle, comfortable separation is usual
3 to 6 years: Child becomes primary focus.
Explain exactly what will happen; what you will do
Then do it that way. (Be trustworthy!)
From 3 of 4 years through adolescence:
Give child choices
Parental presence often helpful
Physical Exam
Upper airway
Chest
General body habitus
Coexisting disease
Lab Testing
Healthy children for routine elective surgery DO NOT need routine lab testing.
Order tests only if indicated.
NPO Status
NPO orders vary with age
Give specific instructions
2 hours sufficient for clear liquids
4 hours for breast milk
NPO after midnight for solid food
Pediatric Premedication
Many drugs and many routes
– IM, IV, nasal, oral, rectal
Narcotics, sedatives are most common
Learn from those with experience
Pediatric Premedication
Preoperative sedatives in children
Oral
Midazolam (0.5-0.75 mg/kg, onset 30 minutes and lasts approximately 30 minutes)
Ketamine (5-6 mg/kg)
Transmucosal fentanyl (facial pruritus, nausea and vomiting, oxygen desauration)
Clonidine (4 μg/kg)
Nasal
Midazolam (0.2 mg/kg, rapid absorption as avoids first pass metabolism, disadvantage is transient nasal irritation)
Rectal
Midazolam (0.5-1.0 mg/kg)
Intramuscular
Midazolam (0.3 mg/kg, anxiolysis in 5-10 minutes)
Ketamin (3-4 mg/kg)
Pediatric Induction
Inhalation is most common for small children
All types of adult inductions have been used for children
Key is to have fun and work with the child

Inhalation Induction
Each staff have their own technique
Pre-oygenate ?
Nitrous oxide ?
Which agent ? x
Start IV prior to intubation
Have unit doses available
Airway Control
Mask management
– fingers on mandible (not neck)
– gentle chin lift
Endotrachial intubation
– pediatric blade
– proper tube size



Tube Size
For children over age 2:
– Age + 16
4
No cuff until at least age 8
– cuff increases size by 0.5
Check for air leak
– how much pressure?
Tube depth:
– (age divided by 2) + 12
Check bilateral breath sounds
Bronchi equal angles under age 3







Intravenous Induction
Older children will allow IV
Drugs and doses are similar to adult on mg/kg basis
Consider use of EMLA cream
Required on small children who require rapid sequence induction
Narcotics
Children have post op pain too!
Too much may depress respiration
May slow wake-up
Most children tolerate small doses of fentanyl and still wake up quickly
Muscle Relaxants
Succinylcholine
– use only for emergency
– may use IV or IM
– increased dose / kg required
– consider atropine premedication
– infants do not fasiculate
Non-depolarizing relaxants
– receptors are more sensitive
– response is variable
– large ECF volume dilutes drug
– duration may be prolonged due to immature liver
 
Breathing Systems
Should:

  • prevent rebreathing of CO2
  • offer low resistance to breathing
  • be light weight
  • have unidirectional valve or high gas flow
Nonrebreathing circuits minimize the work of breathing
Pediatric circle system can also be used very effectively in infants and children
Monitoring
Should be monitored continuously with precordial or esophageal stetoschope.
Pulse oximetry, capnography, blood pressure, temperature, and ECG should also be monitored routinely in children.


Postanesthesia Care
Challenges during recovery of the young
child in the postanesthesia care unit

  • Hypothermia
  • Nausea and vomiting (prophylactic ondansteron)
  • Postoperative pain (self reported or physiologic signs including hypertension, tachycardia, agitation, nausea and vomiting; treat severe pain with fentanyl or morphine iv)
  • Fear associated with awakening in a strange environment (permit parent to be present)

===============================================================

(Bestsellers in Instant Video)(Bestsellers in Featured Categories)(Bestsellers in Automotive)(Bestsellers in Baby Products)(Bestsellers in Beauty)(Bestsellers in Subjects)(Bestsellers in Camera & Photo Features)(Bestsellers Cell Phones & Wireless Store)(Bestsellers Classical Music)(Bestsellers Computers)(Bestsellers DVD in Movies & TV)(Bestsellers Electronics)(Bestsellers Gourmet Food)(Bestsellers in Grocery & Gourmet Food)(Bestsellers in Home, Garden & Pets)(Bestsellers in Health & Personal Care)(Bestsellers in Industrial & Scientific)(Bestsellers in Jewelry)(Bestsellers in Kindle Store)(Bestsellers in Kitchen & Housewares)(Bestsellers in Magazines & Newspapers)(Bestsellers MP3 Downloads in Featured Categories)(Bestsellers Music in Styles)(Bestsellers Musical Instruments in Featured Categories)(Bestsellers Office Products in Office Products)(Bestsellers in Shoes)(Bestsellers in Software)(Bestsellers in Sports & Outdoors)(Bestsellers in Tools & Hardware Home Improvement)(Bestsellers in Toys & Games)(Bestsellers in VHS)(Bestsellers in Video Games)(Bestsellers in Watches)(Bestsellers in Wireless Accessories)

0 comments: