Distinguishing Characteristics of Neonatal Physiology

1
Distinguishing Characteristics of Neonatal
Physiology

• High oxygen consumption
• Dependence on heart rate to maintain CO and BP
• Large extracellular fluid compartment
• Blood volume per kg greater than adult
• Vulnerable to hypothermia

2
Gas Exchange Values

• Neonate (3kg) Adult (70kg)
• O2 consumption 6.4 3.5
• (ml/kg/min)
• CO2 production 6 3
• (ml/kg/min)
• Alveolar ventilation 130 60

3
Pulmonary Function Values

• Neonate (3kg) Adult (70kg)
• Tidal volume (ml/kg) 6 6
• Respiratory rate 35 15
• Vital capacity (ml/kg) 35 70
• Functional residual
• capacity (ml/kg) 30 35

4
Blood Gas Values

• Neonate (3kg) Adult (70kg)
• PaO2 65-85 85-95
• PaCO2 30-36 36-44
• pH 7.34 - 7.40 7.36 - 7.44

5
Endotracheal Tube Size

• 1 kg 2.5 (mm internal diameter)
• 3 kg (term) 3.0

6
Endotracheal Tube Size

• Age (years)
• 1 3.5 uncuffed
• 2 4.0
• 3 - 5 4.5
• 5 - 6 5.0

7
Endotracheal Tube Size

• Age (years)
• 5 - 6 5.0 cuffed
• 6 - 8 5.5
• 8 - 10 6.0
• 10 - 12 6.5

8
Body Composition

• Child
• Neonate at Puberty
• Blood Volume (ml/kg) 85 - 100 70 - 80
• Total body water ( of BW) 73 60
• Extracellular fluid ( of BW) 40 20
• Muscle mass ( of BW) 20 50
• Fat ( of BW) 12 18

9
Blood Cell Count

• Age Hb(g/dl) Hct() WBC(c/mm3)
• 1 day 19 61 18,000
• 1 month 14 43 12,000
• 1 year 12 35 10,000
• 10 years 13 39 8,000

10
Intraoperative Fluid Therapy

• (5 D/LR,ml/kg/h) Maint. Replcmt
  Total
• Herniorrhaphy 4 2 6
• Pyloromyotomy 4 4 8
• Bowel resection 4 6 10

11
Muscle Relaxants

• Infants are more sensitive to non-depolarizers.
  However, since the VD is large, dosage is the
  same as for adults.
• Infants are less sensitive to SCh
• Infant dosage is 2 mg/kg IV

12
Effects of Drugs in Neonates

• Generally prolonged, due to decreased hepatic and
  renal clearance.

13
Blood Replacement

• Blood volume is about
• 100 ml/kg neonates
• 80 ml/kg older children
• Blood replacement indicated if loss exceeds 20
• Crystalloid substitution (5 D/LR)
• about 2 - 3 times the estimated loss
• Packed RBC, 1 ml/kg, increase Hct by 1.5

14
Fresh Gas Flows Recommendedfor Coaxial Circuit

• Infants lt 10 kg 2 L/min
• Children 10 - 50 kg 3.5 L/min
• Over 50 kg 70 ml/kg/min

15
Treatment of Subglottic Edema

• Racemic epinephrine
• (0.5 ml of 2 solution diluted to 3.5 ml)
• give by aerosol
• Dexamethasone
• 4 mg infants
• 8 mg, older children
• give IV

16
Malignant Hyperthermia Principles of Treatment
(2)

• Correct metabolic acidosis
• NaHCO3 1-2 mg/kg IV
• Treat cardiac dysrhythmias with procainamide
• 15 mg/kg IV
• Monitor in an ICU

17
Pediatric Preoperative Management

• Minimum Hb values (10g/dl)
• Hydration (clear liquids up to 3 hrs before
  surgery)
• Preanesthetic medication
• Anticholinergics (atropine 0.02 mg/kg IM or IV)
• Sedation (scopolamine 0.1 - 0.15 mg IM)

18
Induction Agents

• Halothane, sevoflurane
• IV induction
• dermal lidocaine patch, 27 gauge needle
• Methohexital 15 - 25 mg/kg rectally
• Opioids
• Muscle relaxants
• Sensitive to nondepolarizers, relatively
  resistant to SCh

19
Monitoring of the Pediatric Patient

• ECG (does not localize ischemic areas)
• BP (non-invasive preferable, right radiala is a
  preductal site)
• Temperature
• Precordial or esophageal stethoscope
• Pulse oximeter
• Capnography (limited by small tidal volume and
  leaks around uncuffed tubes)

20
Neonatal Diseases

• Respiratory distress syndrome
• Bronchopulmonary dysplasia
• Diaphragmatic hernia
• Tracheoesophageal fistula

21
Postoperative Risks in Neonates

• Apnea spells
• Retinopathy of prematurity
• Intracranial hemorrhage
• Hypothermia
• Hypoglycemia
• Sepsis

22
Abdominal Wall Defects

• Omphalocele Gastroschisis
• Umbilical herniation Abdominal wall defect
• Congenital heart disease Congenital anomalies
• unlikely
• Prematurity unlikely Prematurity likely

23
Craniofacial Abnormalities

• Cleft lip and palate
• Often associated with other congenital anomalies
• Mandibular hypoplasia (may require LMA)
• Pierre Robin
• Treacher Collins
• Goldenhar syndromes

24
Anesthetic Problems with Craniofacial Surgery

• Difficult intubation
• Excessive blood loss
• Hypothermia
• Corneal abrasions
• Postoperative respiratory obstruction

25
Croup Epiglottitis

• Croup Epiglottitis
• Age lt 2 years 2-6 years
• Incidence 80 5
• with stridor
• Etiology Viral H. influenzae
• Onset Rapid Gradual

26
Respiratory Problems

• Postintubation laryngeal edema
• Foreign body aspiration
• Laryngeal papillomatosis
• Lung abscess

27
Malignant Hyperthermia Susceptibility

• Family history
• Myopathic syndromes
• Abnormal elevation of CPK
• Muscle biopsy (isometric contracture with
  caffeine)

28
Malignant Hyperthermia Prophylaxis

• Dantrolene 5 mg/kg q.6 x 4 orally
• or 2.4 mg/kg IV prior to induction
• Follow with 1.2 mg/kg IV in 6 hrs
• Avoid triggering drugs

29
Malignant HyperthermiaSigns of Onset

• Masseter spasm after admin. of SCh (50)
• Tachycardia
• Increased CO2 production
• Hypoxemia
• Rise in body temperature
• may be a late sign

30
Malignant HyperthermiaPrinciples of Treatment (1)

• Terminate anesthesia with inhaled anesthetics
• Give 100 oxygen, hyperventilate
• Dantrolene 2-3 mg/kg IV, repeat q.5 -10 min until
  signs are controlled (max. 10 mg/kg total)
• Initiate cooling
• Administer fluids to maintain urine output

31
Fasting Deficit in Neonates

• Hourly maintenance fluid requirement (4
  ml/kg/hr) times the number of hours since the
  last feeding
• Give half the deficit during the first hour of
  anesthesia
• Give the other half in the next 2 hrs plus
  maintenance

32
Intravenous Solutions

• 5 D/LR For maintenance 3d space loss
• Limit to 15 - 20 ml/kg
• If 3d space loss is moderate to extensive,
  substitute 5 D/NS for maintenance
• If 3d space loss is massive, give 5 albumin to
  restore 1/3 to 1/4 of the loss

33
Daily Fluid Maintenance Requirements

• First 10 kg 4 mg/kg/hr
• Second 10 kg 2 mg/kg/hr
• Over 20 kg 1 mg/kg/hr

34
Pediatric Breathing Circuits

• Jackson-Rees system (Mapleson D)
• Coaxial circuit (Bain)
• Magill system (Mapleson A)
• Closed absorption

35
Regional Technics

• Bier block
• Ilioinguinal iliohypogastric blocks (hernia)
• Penile block (bupivacaine 0.5, 1 ml/kg, without
  epinephrine)
• Spinal anesthesia (tetracaine 0.4 mg/kg)
• Epidural anesthesia caudal
• (bupivacaine 0.25 with 1200,000 epinephrine,
  3 mg/kg limit)