Pediatric Anesthesia Flashcards
Why are neonates/preterm infants at increased anesthetic risk?
- pulmonary factors
- cardiovascular factors
- thermoregulation factors
- pharmacologic factors
What are the pulmonary factors affecting neonates?
- anatomic differences
- lower FRC, VC is 1/2 and RR is 2x that of adults
- higher O2 consumption
- rightward shift of CO2 response curve
- agents have more profound effects on ventilation & oxygenation
What are the cardiovascular factors affecting neonates?
- ventricles are non-compliant; increasing contractility does not increase CO
- CO is HR-dependent
- parasympathetic system is more active – more prone to bradycardia
- agents have more profound myocardial depressant effects
What are the thermoregulation factors affecting neonates?
- poor central thermoregulation
- little muscle mass –> cannot shiver effectively
- non-shivering thermogenesis –> uses brown fat; inefficient (consumes more O2)
What are the pharmacologic factors affecting neonates?
- larger volume of distribution
- less protein-binding affinity
- immature kidneys and liver
- larger initial dose but slower clearance
- more rapid uptake of volatile agents
- lower MAC
Why are neonates/preterm infants at high risk of regurgitation/reflux?
Incompetent LES, slow gastric emptying time
What are the 2 most common causes of morbidity in the neonatal period?
Apnea
Bradycardia
Why is apnea dangerous?
Chemoreceptors are not very sensitive to hypercarbia and hypoxia. Apnea lasting >15 seconds may lead to bradycardia and worsen hypoxia.
What are the mechanisms of heat loss?
Radiation, conduction, evaporation, convection
In what order do the mechanisms contribute from greatest to lowest heat loss?
- Radiation
- Convection
- Evaporation
- Conduction
How to minimize heat loss?
- Warm room at least 1 hour prior (>24C)
- Use warming blanket & lights, head cover
- Cover exposed skin with plastic
- Use forced-air warming devices
What are common intraoperative problems?
- hypoxia
- bradycardia
- hypothermia
- hypotension
What are the usual causes of bradycardia in neonates?
hypoxia
vagal stimulation - laryngoscopy
volatile anesthetics, succinylcholine
What is the usual cause of sudden intraoperative hypoxia in neonates?
dislodged/displaced ETT OR pressure on chest/abdomen during surgical manipulation
Up to what age do you expect postoperative apnea?
60 weeks post-conceptual age (PCA), even with minor surgery.
What are the most common neonatal surgeries?
TEF/EA
Gastroschisis
Omphalocele
Congenital Diaphragmatic Hernia
Patent Ductus Arteriosus
Pyloric Stenosis
Intestinal Obstruction
What other preparations be done in anesthetizing a neonate?
- Multiple sizes of airway (both smaller and larger) ready
- Compute for MF, EBV, and ABL
- Use a Buretrol or Soluset
- Consider using a precordial stet
Is surgical repair of pyloric stenosis emergent?
No. Make sure to correct fluid and electrolyte imbalances before proceeding with surgery.
What are the metabolic disturbances present in pyloric stenosis?
Dehydration
Hypochloremia
Metabolic alkalosis
How to induce a neonate with congenital diaphragmatic hernia (CDH)?
Awake intubation
Mask ventilation is CONTRAINDICATED (because it can cause visceral distention and worsen oxygenation)
Decompress the stomach with OGT/NGT
What are the ventilation strategies for CDH?
Low pressures (<25 cmH2O) - to prevent barotrauma
Permissive hypercapnia (45-60 mmHg) - secondary to lower TV
Pre-ductal 85-95%, post-ductal >70% - to avoid O2 toxicity
Is surgical repair of CDH emergent?
No. Severity of pulmonary hypertension depends on underlying lung hypoplasia.
What are other congenital anomalies that may present with TEF?
VATER/VACTERL:
Vertebral
Anus (imperforate)
Cardiac
Renal
Limb
What other anomalies may present with omphalocele?
cardiac, urologic, and metabolic
What other anomalies may present with gastroschisis?
usually none
Which surgeries usually necessitate delayed extubation?
CDH
Repair of gastroschisis/omphalocele
Describe the baroreceptor reflex in a child.
Infants have an immature baroreceptor reflex –> cannot effectively compensate for hypotension by increasing HR
What are the anatomic differences between adult and pediatric airways?
- obligate nose breather - easily blocked by secretions
- large tongue - obstruction, difficult laryngoscopy
- large occiput - sniffing position is achieved by placing a shoulder roll
- anterior larynx & vocal cords slant anteriorly - difficult intubation
- larynx & trachea are funnel-shaped - vocal cords are the narrowest portion
What are the differences between adult and pediatric pulmonary mechanics?
- ↓ pulmonary compliance – prone to airway collapse
- ↑ airway resistance d/t small airways – ↑ work of breathing
Prone to diseases affecting small airways - ↓ TLC, ↑ RR and O2 consumption - more rapid desaturation
- ↑ closing volume – ↑ dead space
- horizontal ribs, pliable ribs and cartilage – inefficient chest wall mechanics
- Less type 1 high-oxidative muscle – fatigue more easily
How to induce anesthesia in children?
INHALATIONAL
and
INTRAVENOUS
How to do inhalational induction?
70% N2O + 30% O2 for 1 minute > > add sevoflurane
How to do inhalational in an uncooperative child?
RAPID induction:
Hold the kid down
Use 70% NO + 30% O2 + 8% sevoflurane
Place mask against the child’s face
Decrease sevoflurane once induced
How to induce a sleeping child?
STEAL induction:
Hold the mask near the face while gradually increasing sevoflurane
What are the common induction meds and doses?
Propofol 2-3 mg/kg IV
Etomidate 0.2-0.3 mg/kg IV
Ketamine 1-3 mg/kg IV or 2-5mg/kg IM
What is EMLA?
Eutectic Mixture of Local Anesthetics: 2.5% lidocaine + 2.5 % prilocaine
Apply at least 60 minutes prior to use
What happens in left-to-right shunting?
right-sided & pulmonary circulation volume overload > ↓ pulmonary compliance & congestive heart failure
What happens in right-to-left shunting?
hypoxemia, LV overload
Which type of shunt causes cyanosis?
right-to-left is cyanotic
left-to-right is acyanotic
How does a left-to-right shunt affect induction?
INHALATIONAL: minimally affected
INTRAVENOUS: prolonged onset
How does a right-to-left shunt affect induction?
INHALATIONAL: delayed uptake
INTRAVENOUS: shorter onset
What other considerations are necessary for a child with CHD?
Maintain PVR
Avoid air bubbles
Prophylactic antibiotics to prevent IE
What are conditions/drugs that increase left-to-right shunt?
low HCT
↑ SVR, ↓ PVR
hyperventilation
hypothermia
isoflurane
What are conditions/drugs that increase right-to-left shunt?
↑ PVR, ↓ SVR
hypoxia
hypercarbia
N2O, ketamine
What is the effect of pulmonary vascular resistance on intracardiac shunting?
Left-to-Right:
↑ PVR - reversal of blood flow
↓ PVR - pulmonary edema
Right-to-Left:
↑ PVR - worsen oxygenation
↓ PVR - improve hemodynamics
What are the 4 lesions in TOF?
- pulmonary artery atresia/stenosis (right ventricular outflow tract) obstruction
- overriding aorta
- VSD
- right ventricular hypertrophy
How to manage a tet spell?
- maintain airway
- volume infusion
- increase depth of anesthesia
decrease surgical stimulation - beta-blocker to control HR
- phenylephrine to ↑ SVR
How to estimate ETT size?
Cole formula:
Uncuffed = (age/4)+4
Cuffed = (age/4)+3
Insert ETT ~3x the internal diameter
Can cuffed ETT be used in < 8yo?
Yes, advantages include:
- lower number of intubation attempts
- decreased air leak
- allow use of lower FGF
What is the effect of age on MAC?
1-6months: highest MAC - least potent
children > adults
premature & neonates < children
How to compute for the maintenance fluid?
Use the 4-2-1 rule (Holliday-Segar)
What is the estimated blood volume in children?
neonates ~90ml/kg
1 y/o ~80ml/kg
>1 y/o ~70ml/kg
How to compute for the allowable blood loss?
[EBV x (actual hct - lowest acceptable hct)] / average hct
What is the most common type of regional anesthesia done in children?
Caudal block
- bupivacaine 0.125 - 0.25%
- ropivacaine 0.2%
What is the dose for caudal block?
Depending on level of block
- sacral/lumbar: 0.5ml/kg
- lumbar/thoracic: 1ml/kg
- upper thoracic: 1.2ml/kg
What are common postoperative concerns/complications?
PONV
Laryngospasm, stridor
Emergence agitation
What are the risk factors for PONV in children?
Age > 6yo
Procedure > 20min
Eye & inner ear surgeries
Tonsillectomy/adenoidectomy
History of motion sickness
Preop nausea/anxiety
Use of opioid, nitrous oxide
How to manage PONV in children?
Limiting oral intake
IV hydration
Prophylaxis if high-risk (ondansetron, dexamethasone, metoclopramide)
Differentiate laryngospasm from stridor
Laryngospasm is the transient, reversible spasm of the vocal cords
Stridor - high-pitched sound usually occurring at inspiration; may be associated with laryngospasm
How to manage laryngospasm?
ASK FOR HELP
Jaw thrust, establish airway
Suction secretions
CPAP + 100% O2
May give propofol or NMB as necessary
Which agents are associated with emergence agitation?
Sevoflurane, desflurane (shorter-acting volatile agents)
Ketamine
What is the general guideline on children with URTI for an elective procedure?
Postpone 4-6weeks
- risk for adverse respiratory events is 9-11x
How to minimize adverse respiratory events in a child with ‘mild’ URTI?
Minimize airway manipulation: mask > LMA > > ETT
Anticholinergics to decrease secretions
Beta-agonist to decrease airway reactivity
