Short notice in neonatal anesthesia part1

Short notice in neonatal anesthesia
Aous Hani Nief, MD
Fellow of the Iraqi board for medical specialization
The board of anesthesiology (FIBM)
Zliten teaching hospital, Zliten / Libya
Department of anesthesia and RCU
E-mail: aous_hani@yahoo.com
Phone No. 00218913537076
Source of financial support: Zliten teaching hosp.

The neonatal period is defined as the first 30 days of extrauterine life
(Berry FA, Castro BA: Neonatal anesthesia. In Barash PG, Cullen BF, stoelting
RK: clinical anesthesia, pp 1181 – 1204. Philadelphia, Lippincott Williams &
Wilkins, 2006). The most important systems that concern anesthesiologist are
the CVS, Resp. System, Renal and hepatic systems, and the major differences
are exist in (1) airway anatomy, which will make intubation not difficult but
different neonate needs no pillow to have the position of intubation due to the
large occiput he has, but he needs a light pressure by the little finger of the left
hand on the larynx to have a good visualization of the vocal cords ,(2)
physiology, which include myocardium sensitivity to inhalational and the
possibility of myocardium depression which necessitate the use of atropine as
a premedication, desaturate easily due to high O2 consumption with low
reserve, easy hypothermia due to low insulating fat and underdeveloped
thermoregulation capability , and(3) pharmacokinetic and pharmacodynamic
response of the neonates to the drugs used in GA, it was very important step in
the development of anesthesia to deal with the neonates in a separated entity.

ANATOMICAL CONSIDERATION (barash, secret, companion)
• Neonates are obligatory nasal breathers and at the same time they has a
narrow nasal opening, this will easily make breathing difficult to the neonate
and increase the airway resistance when there is a nasal mucosal congestion
or mucus in the nose.
• a small mouth opening and a short neck will make intubation not difficult but
different from adults .due to the large occiput they do not need a pillow to flex
the neck for intubation .
• a large tongue will easily obstruct the airway specially during mask ventilation.
• a small face area make mask ventilation and control difficult.
• glottis is at a higher position (C4) than adults (C6) with a floppy epiglottis and
slanting vocal cords this will make visualization of the vocal cords a little bit
difficult .
• narrow cricoid cartilage which is considered the narrowest part in the trachea
is used to seal around the tube instead of the cuff, it should only leak when
airway pressure is above 20 cm H2O to confirm good fitting of the tube .
• wider jaw angles will make the tongue closer to the posterior wall of the
pharynx and facilitate airway obstruction specially during mask ventilation .
• horizontal ribs makes the ventilation mainly diaphragmatic.

PHYSIOLOGICAL CONSIDERATION (oxford, secret, companion)
Respiratory consideration:
• FRC is the volume of air in the lungs after tidal expiration in neonates it is 27 –
30 ml/kg, and it is smaller than closing volume( it is the volume of air at which
alveoli starts to collapse),in adults an FRC larger than closing volume keeping
the alveoli inflated, this will serve two purposes first to reduce the power
needed to reinflate the alveoli and second to act as oxygen reservoir , but it is
not the case in neonates a small FRC (FRC < closing volume) will cause
alveolar collapse with each respiratory cycle, a poor respiratory reserve will
cause :
a. desaturation rapidly due to the small oxygen reserve superadded by
high oxygen consumption per minute due to high metabolic rate.
b. atelactaisis (closing volume occur within Vt expiration) this will increase
work of breathing and neonates get tired very fast.
{ CPAP improves oxygenation and reduce work of breathing by
keeping alveoli opened during the respiratory cycle}
• intercostal muscles are poorly developed,( oxidative metabolism) make
respiratory muscles fatigue easy.
• respiration is mainly diaphragmatic so any abdominal distention will splint the
diaphragm and reduces it is movement and this will impair ventilation.
• minute ventilation is rate dependent (high rate 30- 50) due to small Vt.

• High alveolar minute ventilation, due to high respiratory rate (150 ml/Kg/min.
For adult 60 ml/Kg/min.) this will make rapid induction, recovery and
respiratory depression, and more fast heat loss
• narrow airways, increase airway resistance and work of breathing.
• Apnea is a common postoperative problem especially in premature. Treated
with Caffeine 10 mg/Kg iv. , Or thiophylline 5 mg/kg iv. , Or CPAP
• low PaO2 (75 mmHg) ( adult 90 – 100 mmHg) but saturation is 97% due to
HbF which form around 85% of neonate Hb has a very high affinity to oxygen
and this will reduce oxygen delivery to tissue.
• reduced central chemoreceptors sensitivity to hypercapnia, this will impair the
main respiratory drive.
• (barash)
Neonate Adult
O2 consumption 7 – 9 ml/kg/min. 3 ml/kg/min.
Vt 7 ml/kg 7 – 10 ml/kg
Rate 30 – 50 / min. 12 – 16 / min.
Minute ventilation (7ml /kg) × rate/min. (7ml /kg) × rate/min.
Example 4 kg neonate minute ventilation = 7 × 4 × 40 = 1120 ml/