Pediatric Anesthesia

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Pediatric Anesthesia
Presented May 2003

• Abdulaziz Hisham Al Gain

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• Development
• Organogenesis - 1st 8 weeks
• Organ function - 2nd trimester
• Body mass - 3rd trimester

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• Changes in cardiovascular system
• Removal of placenta from circulation
• Increasing of systemic vascular resistance
• Decreasing of pulmonary vascular resistance
• True closure of PDA 2-3 weeks ? critical
  transitional circulation
• Myocardial cell mass less developed ? prone to
  biventricular failure, volume loading, poor
  tolerance to afterload, heart rate-dependent
  CO
• True for young infants

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• Changes in pulmonary system
• Small airway diameter - increased resistance
• Little support from the ribs
• VO2 2x gt adults
• Diaphragm and intercostal muscles do not achieve
  type-1 adult muscle fibers until age 2
• Obligate nasal breathers

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• Airway difference
• Large tongue
• Higher located larynx
• Epiglottis short and stubby, angled over the
  inlet
• Angled vocal cords ? we must rotate ETT to
  correct lodging at anterior comissure
• Narrowest portion is cricoid cartilage

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• Chest wall/Respiratory difference
• Ribs are horizontal in neonates (vertical in
  adults)
• Ribs and cartilages are more pliable
• Chest wall collapse more with increased negative
  intrathoracic pressure
• Atelectasis is more common
• ? FRC
• ? number of alveoli
• Alveolar ventilation/FRC
• Adults 1.51
• Infants 51 (? respiratory rate)

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• Kidney and liver difference
• Low renal perfusion pressure, immature GF, TF,
  obligate Na loser in the 1st month of life
• Complete maturation _at_ 2 years of age
• Impaired liver enzymes, including conjugation
  react.
• Lower levels of albumen and proteins - prone to
  neonatal coagulopathy, and less drug bound ?
  higher drug levels

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• GI system and thermoregulation
• Full coordination of swallowing 4-5 months ?
  increased risk for GE reflux
• Large body surface area/weight
• Limited ability to cope stress
• Minimal ability to shiver in 1st 3 months
• Heat whole body including the head

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• Pharmacology/dynamics
• Increased total body water
• Large initial dose required
• Less fat ? longer clinical drugs effect
• Redistribution of the drug into muscle will
  increase duration of clinical effect (fentanyl)
• Consider liver and kidney immaturity

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• Volatile anesthetics
• Isoflurane
• Less myocardial depression than Halothane
• Preservation of heart rate
• CMRO2 reduction rate
• Desflurane
• Increased incidence of coughing, laryngospasm,
  secretions
• Concern of hypertension and tachycardia from
  sympathetic activation

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• Volatile anesthetics (2)
• Sevoflurane
• Less pungent than Isoflurane
• Concern of compound A (nephrotoxicity)
• Most suitable for induction
• Remember MAC for potent volatile anesthetics is
  increased in neonates, but may be lower for
  sicker neonates and premies

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• Induction drugs
• Methohexital
• 1-2 mg/kg i.v. or 25-30 mg/kg per rectum
• Side effects
• burning
• hiccup
• apnea
• extrapyramidal syndrome
• Contraindication temporal lobe epilepsy
• Thiopental
• 5-6 mg/kg i.v.
• Caution in low fat children and malnourished

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• Induction drugs
• Propofol
• 3 mg/kg i.v. (until 6 years of age)
• Pain on injection - 0.2 mg/kg Lidocaine i.v.
• Ketamine
• 10 mg/kg IM, PR, orally
• Increased salivation
• Contraindications Increased ICP
• Open globe injury

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• Induction drugs
• Benzodiazepines
• Diazepam
• 0.1-0.3 mg/kg orally
• T1/2 80 hours ? contraindicated lt 6 months
• Midazolam
• Only FDA benzodiazepine approved in neonates
• 0.1-0.15 mg/kg IM
• 0.5-0.75 mg/kg orally
• 0.75-1.0 mg/kg rectally
• Reduce dose in drugs ? cause Cytochrome P- 450
  inhibition

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• Induction drugs
• Narcotics
• Morphine
• Increased permeability of blood/brain barrier
• 50 mcg/kg IV
• Meperidine
• Less respiratory depression than morphine
• Be cautious in long term administration because
  of its metabolite normeperidine

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• Induction drugs
• Narcotics(2)
• Fentanyl
• 12.5 mcg/kg IV during induction provides stable
  cardiovascular response
• 1-2 mcg/kg adjuvant to anesthesia
• Stable cardiovascular response
• Alfentanyl and Sufentanyl
• More rapid clearance than adults
• Can cause parasympatholysis ? bradycardia,
  hypotension

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• Induction drugs
• Muscle relaxants
• Succinylcholine
• 2.0 mg/kg IV 4.0 mg/kg IM
• Consider Atropine 10-15 mcg/kg given prior SUX
• Potential side effects
• Rhabdomyolysis
• Hyperkalemia
• Masseter spasm
• MH

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• Induction drugs
• Muscle relaxants(2)
• If tachycardia desired - Pancuronium
• Mivacurium - brief surgeries, beware of
  histamine release, bronchospasm
• Rocuronium - useful for modified RSI, and can
  be administered IM (1 mg/kg)

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Muscle relaxants - Summary
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• Premedication
• Almost all sedatives are effective
• Usually not necessary lt 6 months
• Most common route used is oral
• Side effects
• Oral - slow onset
• IM - pain, sterile abscess
• Rectal - uncomfortable, defecation, burn
• Nasal -irritating
• Sublingual -bad taste

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• Pharmacological premedication options
• Role when awake separation of child from parent
  before induction is planned.
• Its success may be judged by the peacefulness of
  the separation.
• Large volume of literature indicates lack of
  clearly ideal technique

http//metrohealthanesthesia.com/edu/ped/pedspreop
6.htm
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• Pharmacological premedication options
• Midazolam (Versed)
• PO 0.5 to 1.0 mg/kg up to 10 mg max.
• Bioavailability 30
• Peak serum levels after about 45 minutes
• Peak sedation by about 30 minutes
• 85 peaceful separation
• Mix with grape concentrate or acetaminophen
  (Tylenol) syrup or elixir or Motrin Suspension
  (10 mg/kg of the 2 suspension)

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• Pharmacological premedication options (3)
• Midazolam (Versed)(2)
• Nasal 0.2 to 0.6 mg/kg
• Peak serum level in 10 minutes
• 0.2 mg/kg same as 0.6 mg/kg except
• 0.2 mg/kg did not delay recovery
• 0.6 mg/kg may delay extubation
• Possible concern animal studies reveal
  neurotoxicity after topical applicaton.

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• Pharmacological premedication options (4)
• Midazolam (Versed)(3)
• Sublingual 0.2-0.3 mg/kg as effective as 0.2
  mg/kg intranasal
• Rectal 0.35 to 1.0 mg/kg
• Some effect by 10 minutes, peak effect 20-30
  minutes.
• 1.0 mg/kg did not delay PACU discharge.

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• Pharmacological premedication options (5)
• Methohexital (Brevital)
• Rectal 25 to 30 mg/kg as 10 solution in warm
  tap water
• 85 sleeping within 10 minutes rectal
  induction of GA (very peaceful separation)
• Sleep duration about 45 to 90 minutes
• 25 mg/kg did not delay recovery in one study, but
  some delay may be expected after a short (less
  than 30-minute) case.

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• Pharmacological premedication options (6)
• Ketamine
• PO 6 to 10 mg/kg
• May slightly prolong time to discharge after a
  short case
• IM 3 to 4 mg/kg sedation
• 2 mg/kg did not delay recovery
• 6 to 10 mg/kg IM induction of general
  anesthesia
• 10 mg/kg as effective as Midazolam 1 mg/kg but
  some delay in recovery may be expected

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• Pharmacological premedication options (7)
• Midazolam Ketamine
• PO 0.4 mg/kg 4 mg/kg respectively
• 100 successful separation
• 85 easy mask induction
• Doubling dose leads to "oral induction of general
  anesthesia" in most cases. Lasts 30 to 60
  minutes.

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• Pharmacological premedication options (8)
• Fentanyl "lollipops" (oral transmucosal Fentanyl)
  
• 15 to 20 mcg/kg
• Increased volume of gastric contents
• Nausea and vomiting
• Pruritus
• Hypoventilation (SpO2 lt90)

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• Pharmacological premedication options (9)
• Metoclopramide (Reglan) PO or IV 0.2 mg/kg
• Ranitidine (Zantac) PO 2.5 mg/kg
• EMLA cream Eutectic mixture of Lidocaine and
  Prilocaine. For cutaneous application by
  occlusive dressing one hour preoperative
• Glycopyrrolate consider for selected patients
  for planned airway instrumentation e.g.
  fiberoptic endoscopy, oral or upper airway
  surgery, cleft palate)5-10 mcg/kg IV or 10
  mcg/kg IM

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• Fasting
• Clear liquids - 2-3 h before the procedure
• If infants are breast fed - 4 h before the
  procedure
• For older patients the adults rule
• Be aware of dehydration

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• Induction of Anesthesia
• Inhalational induction
• Younger than 12 months
• After the induction, place the intravenous
  catheter
• Use suggestions in older child (pilots mask)
• In a case of difficult airway - Fiberoptic
  intubation

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• Induction of Anesthesia
• Rectal induction
• Methohexital
• Thiopental
• Ketamine
• Midazolam
• Technique no more intimidating than rectal
  temperature measurement
• Usual time of onset 10-15 min

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• Induction of Anesthesia
• Intramuscular induction
• Most common used Ketamine
• Disadvantage painful needle insertion
• Advantage reliability

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• Induction of Anesthesia
• Intravenous induction
• The most reliable and rapid technique
• Disadvantage - starting intravenous line
• If patient is older ask the patient
• If you insert IV line
• I. Do not allow the patient to see it
• II. Use EMLA cream
• III. If use local - ask the patient if there is
  any sensation on puncture

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• Patient with full stomach
• Treat the same as adult with full stomach
• RSI with ODL using cricoid pressure
• Tell the patient that will feel touching on the
  neck
• Be aware of ? VO2 (desaturation)
• 0.02 mg/kg of Atropine administer before SUX to
  avoid bradycardia (usually after 2nd dose)
• Use Rocuronium 1.2 mg/kg
• Use Succinylcholine 1-2 mg/kg ? if really need
  short duration (difficult airway)

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Endotracheal tubes
4 (1/4) (age) size 12 (1/2)
(age) depth
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Intravenous fluids
Include if present Fluid deficits Third spaces
losses Hypo/hyperthermia Unusual metabolic
fluids demands
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• Fluid requirements in neonates
• During the 1st week reduced fluid requirements
• Day 1 - 70 ml/kg
• Day 3 - 80 ml/kg
• Day 5 - 90 ml/kg
• Day 7 - 120 ml/kg
• Concern is immaturity of the neonatal kidney
• The volume of extracellular fluids in neonates
  is large
• Consider use of radiant warmers, and heated
  humidifiers - decrease insensible water loss
• Use LR for replacement, D5 with 0.45 NS by
  piggyback

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• Packed Red Blood Cells
• The use has diminished because of disease
  transmission (HIV, Hep C,B. etc)
• Blood volume
• Premature infant - 100 -120 ml/kg
• Full-term infant - 90 ml/kg
• 3-12 month old child - 80 ml/kg
• 1 year and older child - 70 ml/kg
• EBV (starting Hct - target Hct)
• MABL
• Starting Hct

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• Packed Red Blood Cells (2)
• Child usually tolerates Hct 20 in mature
  children
• If
• Premature,
• Cyanotic congenital disease Hct 30
• ? O2 carrying capacity
• No one formula permits a definitive decision
• Replace 1ml blood with 3 ml of LR
• Lactic acidosis is a late sing of decreased O2
  carrying capacity
• Be aware of blood disorders (sickle cell disease)

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• Fresh Frozen Plasma
• Use to replenish clotting factors during massive
  transfusion, DIC, congenital clotting factor
  deficits
• Usually replenished if EBL 1-1.5 TBV
• A patient should be never given FFP to replace
  bleeding that is surgical in nature
• If transfused faster than 1.0 ml/kg/min severe
  ionized hypocalcemia may occur
• If occurs - Rx. with 7.5-15 mg/kg Ca gluconate
• Ionized hypocalcemia can occur in neonates
  frequently because of decreased ability to
  mobilize Ca and metabolize citrate

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Ionized Hypocalcemia
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• Platelets
• Find etiology - TTP, ITP, HIT, DIC, hemodilution
  after massive blood transfusion
• Consider transfusion if Platelets lt 50.000
• In certain hospitals platelet function test is
  available
• If Platelets lt 100.000 and EBL 1-2 TBV -
  transfusion more likely
• If Platelets gt 150.000 and EBL gt 2 TBV
  transfusion more likely

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• Monitoring the Pediatric Patients
• Must be consistent with the severity of the
  underlying medical condition
• Minimal monitoring
• I. 5 ASA monitors
• II. Precordial stethoscope
• III. Anesthetic agent analyzer
• Use of capnograph and O2 analyzers is associated
  with high incidence of false alarms from
• movement artifact
• light interference
• electrocautery

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Special Monitoring the Pediatric Patients

• Intraarterial catheter - most common radial
• Pulmonary artery catheters are rarely indicated
  because equalization of the pressure right/left
  heart
• In a case of severe multisystem organ failure
  insertion of PAC might be particularly useful
• Multilumen catheters are valuable in ICU
  patients
• In a case of rapid fluid replacement peripheral
  venous catheter might be very useful
• Short-term cannulation of femoral/brachiocephalic
  or umbilical vein may be life-saving

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• Anesthesia Circuits
• Nonrebreathing circuits
• 1. Minimal work of breathing
• 2. Speeds-up rate of inhalational induction
• 3. Compression and compliance volumes are
  less (small circuit volume)
• Use of Mapleson D system is recommended in
  children lt 10 kg
• More sensitive to changes in gas flow
• More sensitive to humidification
• Actual delivered volume is greater than other
  systems

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Mapleson D Circuit
Gas disposition at end-expiration during
spontaneous ventilation
Gas disposition at controlled ventilation
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• Neonatal Anesthesia
• Understand differences in
• Physiology
• Pharmacology
• Pharmacodynamic response
• Most of the complications that arise are
  attributable to a lack of understanding of these
  special considerations prior to induction of
  anesthesia
• Be aware of
• Sudden changes in hemodynamics
• Unexpected responses
• Unknown congenital problem

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• Neonatal Anesthesia (2)
• Children lt 1 year old have more complications
• I. Oxygenation
• II. Ventilation
• III. Airway management
• IV. Response to volatile agents and medications
• Stress response is poorly tolerated
• Consider
• 1. Organ system immaturity
• 2. High metabolic rate
• 3. Large ratio body surface/weight
• 4. Ease of miscalculating a drug dose

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• Neonatal Anesthesia (3)
• Prevention of paradoxical air emboli
• Fluids instituted with volume-limiting devices
• Minimize thermal stress
• Use flow-through capnograph if possible
• Prevent retinopathy of prematurity by
• Lower FiO2
• Keep CO2 within normal range

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• Neonatal Anesthesia (4)
• Stress Response
• Poorly tolerated
• Use opioid technique (blunt pain response)
• Ketamine is excellent choice stable
  intraoperative hemodynamics
• Potent volatile anesthetics are poorly tolerated
• No one should be denied anesthesia because of
  the age or weight

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• Special Problems in Neonatal Anesthesia
• Meningomyelocele
• Underestimating fluid or blood loss from the
  defect
• High association with hydrocephalus
• Possibility of cranial nerve palsy
• Potential for brain-stem herniation

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• Special Problems in Neonatal Anesthesia (2)
• Pyloric stenosis
• First 3-6 weeks in life
• Anesthesiologist concern
• I. Full stomach with barium
• II. Metabolic alkalosis with
• Hypochloremia and Hypokalemia
• III. Severe dehydration
• Surgery is never emergency
• Metabolic correction mandatory before the
  surgery
• Suction the stomach before induction
• Consider awake intubation or RSI

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• Special Problems in Neonatal Anesthesia (3)
• Omphalocele and Gastroschisis
• Omphalocele occurs because of failure of the gut
  to return to the abdominal cavity at 10th week
  of life
• Fine membrane covers intestines and abdominal
  contents
• Gastroschisis develops later in life after gut
  has returned into abdominal cavity
• Abdominal contents and organs are not covered
  with any membrane risk of infection

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• Special Problems in Neonatal Anesthesia (3)
• Omphalocele

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• Special Problems in Neonatal Anesthesia (3)
• Gastroschisis

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• Special Problems in Neonatal Anesthesia (3)
• Omphalocele and Gastroschisis(2)
• Anesthesiology concern
• 1. Dehydration
• 2. Massive fluid loss (exposed
• viscera and 3rd space loss)
• 3. Heat loss
• 4. Difficulty of surgical closure
• 5. High association with prematurity, congenital
  defects, including cardiac anomalies
• Minimize infection, Replenish fluids, be liberal
  in muscle relaxants, consider hypotension and
  difficulty ventilation

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• Special Problems in Neonatal Anesthesia (3)
• Omphalocele and Gastroschisis(3)
• During closure consider
• difficulty ventilation
• hypotension
• ? abdominal pressure may compromise liver
  function and alter drug metabolism
• During closure of big defects monitoring of the
  bladder pressures is important if the pressure
  is
• lt 20 cm H2O attempt is to close, gt 20 cm H2O
  closing in stages.

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• Special Problems in Neonatal Anesthesia(3)
• Omphalocele and Gastroschisis (4)
• Be aware of Beckwith-Wiedemann syndrome
• Profound hypoglycemia
• Hyperviscosity syndrome
• Associated visceromegaly

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• Special Problems in Neonatal Anesthesia(3)
• Omphalocele and Gastroschisis ddx. (5)
• Much greater associated defects with Omphalocele
• More fluid loss associated with Gastroschisis

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• Special Problems in Neonatal Anesthesia(4)
• Tracheoesophageal fistula anomaly(1)
• 90 proximal atresia of esophagus
• with distal fistula
• Consider aspiration pneumonitis.
• VATER syndrome
• I. Vertebral
• II. Anal
• III. Tracheoesophageal
• IV. Renal
• MCC of death cardiac anomalies

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• Special Problems in Neonatal Anesthesia(4)
• Tracheoesophageal fistula anomaly(1)
• 90 proximal atresia of esophagus
• with distal fistula
• Consider aspiration pneumonitis.
• VATER syndrome
• I. Vertebral
• II. Anal
• III. Tracheoesophageal
• IV. Renal
• MCC of death cardiac anomalies

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• Special Problems in Neonatal Anesthesia(4)
• Tracheoesophageal fistula anomaly(2)
• Major issues are
• Aspiration pneumonia
• Overdistention of the stomach
• Inability to ventilate
• Postoperative intensive care

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• Special Problems in Neonatal Anesthesia (4)
• Tracheoesophageal fistula anomaly(3)
• Induction
• Awake intubation
• Deliberate right main stem intubation
• Catheter in esophagus
• Prone position with head-up
• Avoid massive distention of the stomach
• by gentle ventilation
• Careful confirmation of tube position
• by moving tube mm by mm (position must be
  between fistula and tracheal bifurcation)
• Tape precordial stethoscope over the left chest

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• Special Problems in Neonatal Anesthesia (5)
• Diaphragmatic hernia
• Usually presentation on
• 1st day of life
• Almost all viscera can be in the
• chest cavity
• Anesthesia concerns
• I. Hypoxemia
• II. Hypotension
• III. Stomach herniation
• IV. Pulmonary hypertension
• V. Systemic hypotension

Shifted mediastinum
Diaphragmatic hernia
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• Special Problems in Neonatal Anesthesia (5)
• Diaphragmatic hernia (2)
• 1. Awake intubation
• 2. Intraarterial catheter
• 3. Use opioids (stress response)
• 4. Use Pancuronium
• 5. Avoid hypothermia
• 6. Avoid any myocardial depressant
• 7. Avoid N2O (abdominal distention)
• 8. Aware of barotrauma-induced pneumothorax
• 9. Adequate intravenous access
• 10. Plan postoperative care

Shifted mediastinum
Diaphragmatic hernia
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• Special Problems in Neonatal Anesthesia (6)
• Former preterm infant (lt37 weeks)
• High incidence of apnea risk factors Respirato
  ry distress syndrome
• Bronchopulmonary dysplasia
• Neonatal dyspnea
• Necrotizing enterocolitis
• Ongoing apnea at the time of surgery
• Use of narcotics
• Long acting muscle relaxants
• Anemia (Hct lt 30)

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• Regional Anesthesia and Anesthesia
• (brief overview)
• Most regional anesthetics are safe to use
• Strict attention to
• Dose
• Route of administration
• Proper equipment used
• Common
• Caudal blocks