Dr Tom Lawson Edited by Drs S.Rawlinson and R.Langford Adapted for the APA from a guide ...

58 Pages·2013·15.15 MB·English

by  Tom Lawson

Paediatric
Anaesthesia for
Beginners
Dr Tom Lawson
Edited by Drs S.Rawlinson and R.Langford
Adapted for the APA from a guide mapped
from RCoA Basic Level Curriculum currently in
use in the Peninsula Deanery
General Disclaimer

The materials and other information provided within ‘Paediatric Anaesthesia for
Beginners’ are for educational, communication and information purposes only and
are not intended to replace or constitute medical advice or treatments.
The author intends and has taken care to confirm that the information presented,
herein is accurate at time of press and describes generally accepted practices.
However, the author(s), editor(s) and publisher(s) accept no responsibility for errors,
omissions, or for any consequences from application of the information within the
book and disclaim any warranty, expressed or implied, with respect to the
currency, completeness, or accuracy of the contents of this publication. The use of
the information contained within, in a particular situation remains the professional
responsibility of the practitioner; any clinical treatments described and/or
recommended may not be considered absolute and universal recommendations,
only the approach or opinion of the author.
The author(s), editor(s) and publisher(s) have exerted every effort to ensure
that drug selection and dosage contained herein are in accordance with current
best practice at the time of publication. However, in view of the changing nature
of anaesthetics and medicine, along with changes in government regulations the
reader is urged to check the British National Formulary (BNF) or package insert for
each drug for any change in information.

The information and action plans contained
within are meant only as a guide and do not
reflect a particular method endorsed by the
APAGBI

Correspondence

Dr Tom Lawson – Speciality Registrar Peninsula Deanery

Email: - [email protected]

2! !
Contents Page
• Definitions 4
• Normal Physiological Values 4
• Formulae 5
• Paediatric Physiology 6 - 9
• Premature Infant Physiology 10 - 11
• Paediatric Anaesthesia 12
• Pre-operative Assessment 12
o General Tips 12
o Psychology of Children 12 - 13
o History 14
o Immunisation 15
o Fasting 16
o Examination 16
o Consent 17
o Explanation 18
o Children with additional or special needs 19
o Child Safety 20 - 21
o Pre-medication 22
o The Ill-Child at Pre-assessment 23
• The Anaesthetic Room and Induction 24
o Patient Positioning 24
o Distraction and Cannulation 25
o Intra-Osseous Access 26
o Monitoring 26
o Inhalation and Intravenous Induction 27 - 28
o Airway Manoeuvres, Equipment and Laryngoscopy 29 - 32
o Difficult Airway Society Algorithms 33 - 35
• Four Common Peri-operative Problems 36
• Peri-operative Fluids & Glucose 36
• Emergence and Extubation 37
• Recovery 37
• Breathing Systems 38 – 39
• Paediatric Regional Anaesthesia 40
• Paediatric Pharmacology 41
• Drugs used in Paediatric Anaesthesia 42 – 44
• PONV 44
• Critical incidents 45 – 56
o An Approach to Paediatric Emergencies 45
o Resuscitation Council Choking Algorithm 46
o Resuscitation Council Cardiac Arrest Algorithm 47
o Anaphylaxis 48
o Acute Asthma 49
o Stridor and Acute Airway Obstruction 50
o Arrhythmias 51
o Laryngospasm 52
o Bleeding Tonsil 53
o Seizure and Hypoglycaemia 54
o Paediatric Sepsis 55
o Resuscitation Council Neonatal Life Support Algorithm 56
• Curriculum Mapping 57

! 3!
Definitions
• Premature = Less than 37weeks
• Extreme Prematurity – Less than 28weeks
• Neonate = up to 44weeks from date of conception
o Post-conceptual age = gestational age at birth + post-natal age
o Low birth weight = Less than 2500g
o Very low birth weight = Less than 1500g
o Extremely low birth weight = Less than 1000g
• Infants = 1month to 1 year
• Child = 1-12 years
• Adolescent = 13-16 years

Different Age Groups and Physiological Parameters

Neonate Infant Child

Heart Rate 110 - 160 95 -140 80 - 120
Resp Rate 30 - 40 25 - 30 20 - 25
Systolic BP 50-60 80 - 100 90 - 110
Tidal Volume 7 - 8ml/kg 7 - 8ml/kg 7- 8ml/kg
FRC 30ml/kg 30ml/kg 30ml/kg
Dead Space 2ml/kg 2ml/kg 2ml/kg
Blood Volume 90 ml/kg 80 ml/kg 70 - 80ml/kg
Hb 11 - 18 11 - 13 11 - 13

4! !
Formulae
• There are several important formulae that you will need to memorize.
• It is worth doing them for each patient you anaesthetise so that they become
second nature

Resuscitation
• Weight (kg)
o All purpose = (Age in years + 4) x 2
 Tends to underestimate weights
o APLS Age specific
 <1 year = (Age in months x 0.5) + 4
 1-5 years = (Age in years x 2) + 8
 6 -12 years = (Age in years x 3) + 7
• Electricity = 4J/kg
• Tracheal tube
o Uncuffed size = (Age/4) + 4
o Cuffed size = (Age/4) + 3.5
o Length = (Age/2) + 12 (oral) or 15 (nasal)
• Fluid bolus = 20ml/kg (or 10ml/kg if trauma or cardiac concerns)
• Adrenaline = 10mcg/kg = 0.1ml/kg of 1:10,000 or 0.01ml/kg of 1:1000
• Glucose = 2ml/kg of 10% Dextrose

Physiological Parameters
• Approximate Systolic BP = 80 + (age x 2)
• Neonates are exceptions to this – Systolic BP = 50-60mmHg

Fluid Formulae
• Bolus = 20ml/kg (or 10ml/kg if trauma or cardiac concerns)
• Normal Hourly Maintenance Requirement
o 4ml/kg for first 10 kg
o 2ml/kg for second 10kg
o 1ml/kg for every additional kg
 I.e. a 22kg child will require 62ml/hr (40ml for 1st 10kg, 20ml
for 2nd 10kg and 2ml for the remaining 2kg)
• Normal Daily Maintenance Requirement
o 100ml/kg for first 10kg
o 50ml/kg for second 10kg
o 20ml/kg for every additional kg
• Nil By Mouth Deficit
o = Hourly requirement x number of hours NBM
• Dehydration Definitions
o Dehydration without shock = <10% fluid loss  slow replacement
o Dehydration with shock = >10% fluid loss  rapid replacement
o Replacement fluid (ml) = % dehydrated x weight (kg) x 10
• Blood
o Transfusion (ml) = 4 x weight (kg) x Desired rise in Hb
o I.e. if Hb is 8g/dl and you want it to be 10g/dl
 Transfusion (ml) = 4 x weight (kg) x 2

! 5!
Paediatric Anatomy and Physiology

Airway Anatomy
• Neonates / Infants
• Head and Neck
o Large Head with prominent occiput  pillows are unhelpful as they
may position the head and neck in a way to obstruct the airway
o Relatively larger tongue  easier to obstruct the airway
o Short Neck and Small Mandible
o Obligate nose breathers when <5months – narrow nasal passages.
• Larynx
o Floppy U-shaped epiglottis  lifted out of the way on
laryngoscopy
o More anterior and cephalad larynx (C4)  hence moving head
more anterior (‘sniffing the morning air’ will not help during
laryngoscopy)
o Cricoid ring = narrowest part of the upper airway  easy to
damage mucosa if ETT is too tight
• Trachea
o Short trachea (from cricoid to carina)  easy endobronchial
intubation
o Soft tracheal cartilage – can collapse with negative inspiratory
pressure
• Lungs
o Bronchi at same angles  bronchial intubation as likely on both
sides
o Higher airway resistance (nasal passages are responsible for 50%)
• Chest
o Horizontal ribs  no bucket handle movement  increased work of
breathing
o Weak respiratory muscles  easy to fatigue if work of breathing is
high
o Diaphragm dependent ventilation  any limitation of
diaphragmatic movement has a large effect e.g. bowel obstruction
• Toddlers
• Head and Neck
o Head is more proportional to body size
o Baby teeth begin to erupt (permanent teeth begin to erupt from
6years)
o Jaw becomes larger
• Larynx
o Epiglottis Is less floppy and may not need to be lifted on
laryngoscopy
• Chest
o <7 years the diaphragm Is the main muscle of respiration

6! !
Respiratory
• Neonates / Infants
• Immature respiratory centres  apnoea risk up to 60 weeks post-
conceptual age  hence give opioids with care
• Lower airway compliance (stiff lungs) – but compliant chest wall
• High Respiratory Rate
• Higher closing volume  risk of hypoxaemia
• Small O2 reservoir, high metabolic rate + oxygen consumption  rapid
desaturation

Cardiovascular
• Neonates / Infants
o Sinus arrhythmia is common
o Stiff, poorly compliant ventricles with less contractile elements
o Reduced contractility
o Limited Starling Response  fluid overload can result in heart failure
o Rate dependent cardiac output
o HR <60bpm = unable to support cardiac output
o High Vagal tone  prone to bradycardia
• Toddlers
o HR decreases
o Systolic BP rises
• School Age and above
o Systolic BP increases
o HR decreases
o Increased Blood Volume
o Heart approaches full size

Neurological
• Neonates / Infants
o General
 Immature sympathetic nervous system  high vagal tone
 Incomplete myelination  complete by age 2
 Pain pathways are intact and functional
o Brain
 Immature BBB (more permeable)
 Higher cerebral metabolic rate, O2 and glucose requirement
 Cerebral blood flow = 50ml/min/100g
 CSF volume = 4ml/kg
 Skull sutures are open
o Spinal Cord / Column
 Spinal cord ends at L3 at term, L2-3 at age 1
 Intercristine line = L5/S1
 Thin sacrococcygeal membrane
• Toddlers
o Parasympathetic and sympathetic activity more equal
o BBB fully formed
o Cerebral blood flow = 100ml/min/100g
o Spinal cord terminates at L1/2 at 8 years
• School Age and above
o Fully developed nervous system by mid-adolescence
o Cerebral blood flow = 50ml/min/100g
! 7!
Hepatic / Renal / Gastrointestinal
• Neonates / Infants
o Hepatic
 Ductus Venosus = patent for 7-10days post-birth
 Phase 1 + 2 reactions are normal from 2-3months
 Low hepatic storage reserves of platelets, glucose and bicarb
 can lead to coagulopathy, hypoglycaemia and acidosis
o Renal
 Full number of nephrons are present at birth, however, they do
not have full filtering / concentrating ability until 2-3months
 High renal vascular resistance at birth  falls at week 2 – 4
 Low Renal Blood Flow at birth  rises at week 2-4
 Low GFR at birth  adult levels by 1 year
o Higher total body water than in older children
 80% in the neonate
 The proportion of ECF to ICF differs
 ECF decreases with age, whilst ICF increases with age.
• Toddlers
o Frequent stomach upsets
o Calorific requirement less than in infancy / adolescence
o Better blood glucose control than in infancy
• School Age and above
o Stomach upsets less frequent
o Stomach size and capacity at adult levels by 14 years of age

Musculoskeletal
• Neonates / Infants
o Immature musculature  easy to fatigue
• Toddlers
o Increased bone and muscle growth
o Incomplete bone mineralisation
o Immature musculature  easy to fatigue

Thermoregulation
• Neonates / Infants
o Immature hypothalamus
o Increased body surface area: weight
o Increased basal metabolic rate
o Poor insulation – thin skin, low fat and immature muscles
 Reduced ability to shiver and produce endogenous heat
o High vagal tone  less able to vasoconstrict
o Non-shivering thermogenesis
 Brown fat = fat with high number of mitochondria (large iron
content makes it brown)
 Noradrenaline stimulates triglyceride oxidation  utilises
oxygen and glucose to generate heat_
 Poorly efficient

8! !
Immunological
• Neonates / Infants
o Reduced ability to synthesize Ig’s  at adult levels by 1 year
o ABO antibodies appear by 2months
• Toddlers
o Immune system immature
• School Age and above
o Lymphatic tissue at peak from age 10-12
o Then regresses to adult levels

Haematopoietic
• Neonates / Infants
o 80% of total Hb at birth = HbF  falls to 5-10% by 4months
o HbF shifts Oxy-Hb curve to the left (alkalosis is bad)
o Hb = 18g/dl at birth  11g/dl at 3months
o Blood volume = 100ml/kg for prems, 90ml/kg for neonates
o High lymphocyte and leucocyte count
• Toddlers
o Blood volume = 80ml/kg
• School Age and above
o Blood volume = 70ml/kg
o Normal adult values

Endocrinological / Metabolic
• Neonates
o Lower glycogen stores
o Immature pathways for gluconeogenesis
o Therefore hypoglycaemia occurs more easily and is less well tolerated

! 9!
Premature Infants
• The overarching consequence of prematurity is that there is incomplete organ
development at the time of birth and this is associated with increased morbidity
and mortality.
• Respiratory
• General
o Chronic Lung disease is common in very-low birth weight infants
o Increased susceptibility to respiratory infections
• Apnoea of Prematurity
o = Pause in breathing of >20secs or
o = Pause in breathing of <20secs with bradycardia +/- cyanosis
o Prem/neonatal Response to hypoxia
 = Brief hyperventilation  apnoea + blunted response to
hypercapnia
 Typically returns to normal by 3weeks, this may take longer
in prems – up to 60weeks post-conceptual age.
 This is of key concern in ex-premature infants.
 Ideally elective surgery should be delayed

o Respiratory Distress Syndrome
 Inadequate surfactant production before 32-34weeks
 Antenatal corticosteroids in preterm labour stimulates surfactant
production and reduces incidence
 Surfactant may need to be given after birth
o Bronchopulmonary Dysplasia
 Affects neonates that receive oxygen / mechanical ventilation
for >28days
 Features include oxygen dependency, hypoxia, hypercarbia,
etc
 Results in reduced lung compliance, increased oxygen
requirements and reversible airway obstruction
o Respiratory Tract injury
 Related to the number/duration of tracheal intubation(s)
 Increased incidence of acquired subglottic stenosis
• Cardiovascular
o Patent Ductus Arteriosus
 Usually closes within 3-4days in 90% of well prems
 Results in increased pulmonary blood flow, worsening RDS,
cardiac failure and low diastolic pressure
 Medical closure with Indomethacin
 Surgical closure in failed medical treatment / NSAID
contraindication
o Difficult venous access
10!!