Neonatal Anesthesia
Hany El-Zahaby, MD
Dept. of Anesthesia, Ain Shams University
“Safe and effective anesthesia for neonates undergoing surgery is
one of the most challenging tasks presented to
anesthesiologist.”
Knowledge
Manual skills
Continuous practice
+
Adequate monitoring
↓
Outcome
Anesthetic
Considerations
for surgeries
on Neonates
Age-specific
considerations
Case-specific
considerations
Age Specific Consideration
Nociceptive System And Stress Response
•The central nervous system is incompletely developed at birth.
•Fully competent neuroendocrine stress reaction in response to surgical
stimulation.
•“Pain memory"
•“Programming phenomena”
•Non-analgesic technique practice is no longer acceptable.
Self-report tools of pain appropriate for different age groups
-Infant's fragile cerebral blood vessels is an important factor in the
development of intraventricular hemorrhage.
-The spinal cord extends to a lower segment of the spine than in older
children .
-The volume of cerebrospinal fluid and the spinal surface area are
proportionally larger in neonates ► increased amount of local
anesthetics (mg/kg) required for a successful spinal anesthesia
in infants.
Age-specific considerations
Airway Features
Age-specific considerations
Fast desaturation
•
•
•
•
•
High metabolic rate (5-8 ml/kg/min)
Tidal volume (6-7 ml/kg/min)
High respiratory rate (40-60 breaths/min)
High alveolar ventilation (130 ml/kg/min)
Lung compliance is less while chest wall compliance is more than
those in adults {reduced FRC and atelectasis} ►PEEP.
• Diaphragm (dominating respiratory muscle ) has less oxidative type I
fibers ► susceptible for fatigue.
• The work of breathing is composed of compliance and resistive
components. The compliance work relative to tidal volume is nearly
the same as in adult. The resistive work increases when breathing
through ETT (4th radius), and through circle system.
 “Neonates and especially ex-premature infants have a tendency
toward periodic breathing that is accentuated by anesthetics,
increasing the risk of postoperative apnea until approximately
55-60 weeks post-conceptual age and require continuous
monitoring of blood oxygen saturation and heart rate until 12hours of apnea free period”.
Apnea
(1) central apnea, due to immaturity or depression of the
respiratory drive; (2) obstructive apnea, due to an infant's
inability to maintain a patent airway; and (3) mixed apnea,
a combination of both central and obstructive apnea.
Susceptibility to Central apnea is exacerbated by hypothermia,
hypoglycemia, and hypocalcemia, anemia, opioids .
• Treatment: xanthines (caffeine & theophylline)
▲ Hct
▲ FiO2
• Never give caffeine & send the neonate home as being “safe now”.
• Even patients treated with naloxone require continuous monitoring
of blood oxygen saturation and heart rate until 12-hours of apnea
free period.
Obstructive apnea is treated by changing the head position, inserting
an oral or nasal airway, placing the infant in a prone position or by
applying continuous positive airway pressure (CPAP)
Age-specific considerations
Cardiovascular
• Fetal hemoglobin has higher affinity for oxygen.
• Oxygen delivery is facilitated by a high cardiac output.
• Cardiac output is more dependent on heart rate.
• Parasympathetic control of heart rate matures earlier and to a
greater extent than β-adrenergic control
– Do not respond to hypovolemia or an inadequate depth of anesthesia
with tachycardia
– More susceptible, to the cardiac depressant effects of volatile
anesthetics
PDA
• With expansion of the lungs during the first breath, pulmonary
vascular resistance decreases and blood flow to the lungs increases
• Neonatal hypoxia, hypercarbia, or acidosis increase PVR & may
result in a return to the fetal-type circulatory pattern with right-to-left
shunt via the PFO or PDA (PA to AO)
• Persistent PDA after declining of pulmonary vascular resistance
causes left to right shunt with pulmonary hypertension and
increased ventilatory support.
• PDA is diagnosed by bounding peripheral pulses, a harsh systolic
ejection murmur at the left sternal border and a large pulsepressure, Echo.
• PDA is treated by indomethacin, coiling or surgical ligation.
PPHN
• Sepsis and aspiration syndromes ► muscularization of pulmonary
arterial vessels.
• Difference in preductal and postductal oxygen saturations, right-toleft shunting of deoxygenated blood via PDA.
• Ultrasonography ► PPHN + no cardiac lesion
• Treatment: oxygenation, alkalosis , inhaled NO
Prevention of Heat Loss
Radiation
Evaporation
Convection
Conduction
Prevention of Heat Loss
Room temp.: 80-85 F
Avoid unnecessary
exposure & cover cotton
wraps as much as
possible
HME (active or passive)
IVF: warm
Active warming mattress
Cover exposed viscera with
warm wet towels
Incubator: keep plugged
Age-specific considerations
Renal Function
• The glomerular filtration rate is
only 15% to 30% of normal
adult levels.
• The kidneys' tubular function is
impaired and hence sodiumretaining ability.
• Renal excretion of medications
such as penicillin, gentamicin,
pancuronium is impaired
►prolonged duration
The initial doses of some medications may be greater on a weight basis than
for adults in order to achieve the desired blood concentration in the presence
of high volume of distribution. In contrast, because of immaturity of renal
function, the interval between dosages of some drugs may be increased
Caloric Consumption is about 100-120 Kcal/kg/day.
Age-specific considerations
Glucose Homeostasis
• In full-term infants, a glucose infusion rate of 5 to 8 mg/kg/min is
required to prevent hypoglycemia i.e. maintenance rate/h
• Excessively fasted, SGA infants, infants of diabetic mothers and
infants with TPN sudden withdrawal are particularly prone to
develop hypoglycemia.
• The signs and symptoms of hypoglycemia (apnea, cyanosis,
seizures, tremors, high-pitched cry, irritability, limpness, lethargy,
eye rolling, poor feeding, temperature instability, and sweating) in
infants are often blunted and nonspecific.
• Is it then justified to use only glucose solutions during operation?
Age-specific considerations
Gastrointestinal & Hepatic Function
• Prolonged gastric emptying + incompetent lower esophageal
sphincters = reflux is common.
• Preterm, hypoxemic, acidotic neonates with low serum protein levels
are liable to get Kernicterus (bilirubin encephalopathy) due to
increased levels of unconjugated serum bilirubin.
• Furosemide & sulfonamides (high protein bound) may displace
bilirubin and increase the possibility of kernicterus.
• Increased intra-abdominal pressure may compromise hepatic drug
metabolism .
Preoperative Laboratory Testing
• Hematocrit
• Blood typing and compatability screening
• Electrolyte (sodium, potassium, chloride and calcium) and acid-base
status (pH, base excess and standard bicarbonate)
• Coagulation profile :
– (APTT) at day 1 averages at 42 compared to 33 in adults.
– Platelet counts are similar to normal adult values in term neonates. The
lowest acceptable platelet count for surgery in neonates is not
specifically known.
– Due to limited reserves and insufficient supply of vitamin K by breast
feeding, intramuscular vitamin K (1 mg) is usually given.
Age-specific considerations
Fasting
Elective:
Clear fluids ►2h
Breast milk ►4h
Infant formula ► 6h
Emergency:
Stomach aspiration
Awake/Rapid sequence
Premedication
• Atropine (10-20µ/kg IV, minimum 100µ) to counteract
parasympathetic reflexes.
• Pain (increments of morphine 10-20µ/kg IV up to 100µ/kg)
Monitoring
• Standard:
ECG
Precordial or esophageal stethoscope?
NIBP
Temperature probe
Pulse oximeter (pre & postductal)
CO2 analyzer (site of sampling)
• Direct BP (significant intravascular instability)
• CVP (vasoactive drugs)
• Urine output (1 ml/kg/h)
How Long Pre-oxygenation?
60 seconds 6L/min (gives 80-90 seconds before desaturation)
(Morrison JE et al: Pediatric Anaesthesia1998:8;293)
Inhalation VS Intravenous Induction?
IV access + hemodynamically stable→ STP 4-8mg/kg (prolonged
emergence & postoperative apnea)- Propofol 3-3.5mg/kg
IV access + hemodynamically unstable → Ketamine 1.5-3mg/kg
Difficult IV access or compromised airway → Sevoflurane or halothane
Combined technique → (opioid + nondepolarizing MR + inhalation agent)
LMA VS ETT?
LMA: less than 30-45 min with spontaneous breathing
Size 1 ( 50% misplacement, NGT, large dead space &
hypercapnea, helpful for ex-premis with BPD)
ETT: “The standard practice in neonates”
Awake intubation (very stressful/painful stimulus/suboptimal
conditions/BP fluctuation)
Relaxation?
Succinyl choline (RSI) (higher doses than adults), large ECF
volume
Nondepolarizing MR (similar doses as adults), sensitivity offset
by large ECF
Deep inhalation anesthesia, disadvantages?
Technique?
•Oral Vs nasal? (lateral/prone/limited head access)
•Straight blade- Paraglossal
•Leak pressure? 20-25cmH2O, affected by head position & MR
•Non-cuffed/cuffed: 8y (upper abdominal & thoracic surgery, poor
lung compliance)
•After intubation → VCM (40cmH2O/15 sec) or TRIM (30cmH2O/10
sec)
The retromolar, paraglossal, or lateral approach to rigid
laryngoscopy utilizing a straight blade.
Microcuff ETT
More anatomical fit
Sealing at low pressures
More distal position
Greater permeability for nitrous oxide
For neonates ≤3 kg and infants ≤1 year, ID
3.0-mm
Post-intubation croup was 0.4% (2/500
children)
Spontaneous Vs controlled?
-Spontaneous: more than 6 M, less than 30 min.
Pressure Vs volume control?
-Pressure control: First few days, premature, respiratory
distress or lung pathology, compensate for leaks.
-Volume control: surgical manipulations interfere with
ventilation.
-Pressure control/volume guaranteed.
-Peep 3-4 is routine.
“ Whatever the technique, an expired tidal volume & PIP
should be tailored to the desired levels”
Maintenance:
• All inhaled anesthetics depress baroreceptor reflex.
• Halothane depress the myocardium more.
• Halothane decrease the heart rate more .
(Hypotension is treated by atropine & lowering halothane)
• Sevo/Isoflurane decrease PVR more (treated by 5-10ml/kg fluid
bolus).
• Nitrous oxide 60% decreases MAC of halothane, isoflurane &
sevoflurane by 60%, 40% & 25% respectively.
• Narcotics:
-Fentanyl 1-2µ/kg if regional block was done.
-Fentanyl based anesthesia for prolonged major
surgery with postoperative ventilation.
-Morphine 0.05mg/kg .
“The use of light general volatile anesthetic with a
central or peripheral nerve block has proved to
be of great benefit in neonatal surgery”
Bosenberg AT et al, Pediatr Surg Int, 1992:7, 289
Larsson BA et al, Anesth Analg 1997:84, 501
Intraoperative Volume Replacement
Hypovolemia with blood loss accounts for 12% of causes of cardiac
arrest in OR with almost half of it due to under estimation of blood
loss.*
*Anesthesia-Related Cardiac Arrest in Children: Update from the Pediatric Perioperative
Cardiac Arrest Registry
Bananker et al, Anesthesia & Analgesia, August 2007
Assessment of dehydration
Wt loss%
Behavior
Thirst
Mucous memb.
Tears
Anterior fontanel
Skin turgor
Urine output
Mild
(50ml/kg)
Moderate
(100ml/kg)
Severe
(150ml/kg)
5
Normal
Slight
Normal
Normal
Flat
Normal
<2ml/kg/hr
10
Irritable
Moderate
Dry
+
+
+
<1ml/kg/hr
15
++irrit/lethargic
Intense
Parched
Absent
Sunken
Increased
<0.5ml/kg/hr
Fluid & blood loss
Type of fluid? Dextrose? BSS? Why?
Weighing swabs before it dries.
Intraoperative blood loss should be replaced with balanced
salt solution (1:3), or colloid (1:1)
Estimated maximum allowable blood loss =
EBV x (Hctstarting – Hctacceptable)
Hctstarting
Emergence
Reversal of MR after spontaneous movement even with adequate time
after last dose
Extubation:
Regular spontaneous breathing
Vigorous movements of all limbs
Gagging
Eye opening or pronounced grimacing
Stable hemodynamics & good oxygen saturation
Absence of significant hypothermia
“Extubate when fully awake”
Case-specific considerations
Case 1
• A 5 days old 3.6 kg male with history of
prematurity (34 W) scheduled for
ventriculo-peritoneal shunt & repair of
encephalocele.
Encephalocele
Neural tube defect with variable neural
dysfunction
+ Hydrocephalus + Arnold Chiari type II
Wet/soft covering
Avoid pressure
Antibiotics
Prone (nasal intubation)
Blood loss
Hypothermia
Latex – free procedure
Document spontaneous breathing
postoperatively
Case-specific considerations
Case 2
• A 2 days old 2.6 kg male 36 W conceptual
age coming from NICU 2.5 ET in place,
ventilated on PCVG mode with moderate
ventilatory setting & and acceptable ABG
planed for repair of esophageal atresia
with tracheoesophageal fistula.
Thoracic Surgeries
Esophageal Atresia/TEF
1cm
Thoracic Surgeries
Esophageal Atresia/TEF
1:3000
M:F 25:3
First fed chocking, cyanosis
CHD, VACTERL association 13%
Thoracic Surgeries
Esophageal Atresia/TEF
Management:
Head up
Continuous low suction on blind pouch
Echocardiography
Antibiotics
Vit K
Next day surgery
Case-specific considerations
Case 3
• 65 W postconceptual age ex-premi male
baby who has been on chronic ventilatory
support-sepsis-PDA-IVH-NEC-multiple
medications-BPD - extubated with great
difficulty in NICU & planed to have
inguinal hernial repair.