Anesthesia
And
The Neonate
Dr: M.A. Zaghloul
Prof. of Anesthesia
Ain-Shams University
Main differences Between
Adults and Neonates
1- METABOLISM
 The resting O2 consumption of the neonate is double
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that of the adult ( 6 ml/kg/min ).
CO2 production is also doubled.
So pulmonary ventilation must be increased ( RR of
neonate is 50 ± 10 ).
If resp. obstruction occurs, neonates become seriously
hypoxic in about half the time than adults.
They are more susceptible to lack of food & water &
become more rapidly hypoglycemic & dehydrated.
Neonates have high resting C.O. to supply enough O2
& remove metabolites.
2- Respiratory System
 Neonates are obligate nasal breathers.
 The combination of small nares & large tongue,
abundant lymphoid tissue, big head, short neck,
increases susceptibility of air way obstruction.
 The long, narrow, omega, shaped epiglottis &
more cephalad vocal cords makes intubation
more difficult.
 The narrowest part of upper airway is opposite
cricoid cartilage ( up to 10 years).
 A rough estimate of endotracheal tube size is:
Diameter (mm) = Age/4 + 4 (above 4y)
Or
ID = ( 16 + age )/4 over 2 y
 The length of neonatal trachea 2.5 cm.
 Nasal tubes need to be longer by 2 cm.
3- Pulmonary Ventilation
 Because of horizontally placed, flexible ribs &
relatively underdeveloped intercostal muscles
they are diaphragmatic breathers &
susceptible to ventilatory embarrassment by
abdominal distension.
 The diaphragm can fatigue under repeated
stress especially in prematures.
 The alveolar bed is incompletely developed at
birth, it reach adult type by 8 years.
 Tidal vol. are the same as in adults on terms
of cc/kg, but O2 reserve during apnea is
smaller .
Age dependent Respiratory variables
NB
6m
1y
5y
RR(b/min) 50±10 30±5 24±6 18±5
TV (ml)
21
45
78
270
MV(L/min)
1
1.35 1.8
5.5
AV(ml/min) 385
1245 1800
DS/TV
0.3
0.3
0.3
0.3
O2 consump.6 -8 ml/kg/min
Pa co2 (mmHg) 30 - 35
30 - 40
30 Pa O2 (mmHg) 60-90
80 -100
80 -
A
12
575
6.4
3100
0.3
3-4
40
100
4- Heat loss & Temperature Controle
There is increased heat loss & decreased
heat production up to 6m of age.
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A- HEAT LOSS
Great surface area in relation to body weight.
Preterms has less subcutaneous fat.
Evaporation from exposed wound.
Infusion of cold fluids.
B- Heat production
 Newborns are unable to shiver.
 Reduced metabolism of brown fat &
carbohydrates due to block sympathetic
system by GA.
 Hypothermia may cause difficulty in
reversing muscle relaxants, hypoglycemia
&. lactic acidosis
5- CIRCULATORY SYSTEM
 The resting C.O. is 2-3 times of adults.
 The resting H.R. is variable ( 110 – 160 ).
 The resting blood volume is about 85 ml/kg.
 The haemoglobin is high (16 – 18 gm/100ml).
 Blood should be given if 10% of bl. vol. is lost
& should be accurate.
 Give Ca gluconate (0.1 of 10% sol./10 ml bl.).
Age Related Circulatory Variables
HR (b/min)
SBP(mmHg)
DBP(mmHg)
SV(ml/b)
CI(L/min/m2)
Hb(g/dl)
NB
133
80
46
4.5
2.5
16.5
6m
120
90
60
7.5
2
11.5
1y
5y
120 90
96
95
66
55
11.5 27.5
2.5 3.7
12 12.5
A
75
120
80
85
3.7
14
Normal & Accepted Hematocrit
Value In Pediatric Patient
Age
Normal
Accepted
( mean/range)
Premature
NB
3m
1y
6y
45 (40-45)
54 (45-65)
36 (30-42)
38 (34-42)
38 (35-43)
35
30 - 35
25
20 – 25
20 - 25
6- Water And Electrolyte Balance
 Water electrolyte turnover in neonate is 2 – 3
times of the adult.
 However the ability to deal with excess or
deficiencies is less ( immature renal function).
Age And Distribution of Body Water
ECF
ICF
Neonate
40%
35% of BW
Adult
20%
40%
of BW
7- Renal Function
Renal Function of Infants, Children & Adults
GFR
U.cl.
Urine exc.
ml/min/1.73m2 ml/min/1.73m2
Term
6m
1y
3y
Adult
38.5
110
117.5
127
127
36
22-46
17
75
75
ml/24 h.
15 – 60
250 – 450
500 – 600
500 – 600
500 – 600
 Neonates have difficulty in reabsorbing bicarbonate
from their urine. Which results in persistent
metabolic acidosis.
 By 6 m, renal function is 80 – 90 % of adult.
 Sodium loading & conservation is not efficient
in neonates.
Weight And Hourly Fluid requirements
Wt. (Kg)
< 10
10 - 20
> 20
Fluid (ml/h)
4 ml/Kg
40 + 2 ml/kg > 10
60 + 1 ml/kg > 20
Fluid Replacement
Clinical situation
vol.( ml/Kg/h)
Intra-abdominal S.
2
Peritonitis/Perforation
4
Two cavity S.
6
• Halve of the deficit fluid is given in
the 1st hour& the other ½ is divided
equally in the subsequent 2 hours
Clinical Significance Of Dehydration
Sig.
Poor skin turg., dry mouth
Sunken font.,tachycard.,olig.
Sunken eyes & fontanel's
Coma
Estimated vol. loss(%)
5
10
15
20
HYPOGLYCEMIA
 The 1st day of the baby have low BG level & low
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glycogen stores in the liver.
It may be necessary to estimate BG conc.
during anesthesia & give 10% G if needed.
Normal BG of full term neonate is 60 – 80 mg/dl
Hypoglycemia if < 30 mg/dl in FT.
Hypoglycemia if < 20 mg/dl in preterm, which is
common especially if BW< 2.5 Kg.
Caloric Requirements
Up to 10 Kg = 100 cal/Kg/day
10–20 Kg = 1000 cal+50 cal/Kg/day for each Kg >10
> 20 Kg = 1500 cal+20 cal/Kg/day for each Kg >20
Drugs In Pediatric Anesthesia
Always Remember That NB Has:
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Higher metabolic rate.
More water content, 75% ( more vol. of dist.).
Less plasma & tissue protein.
Lesser fat & muscle.
Large dist. of C.O. to vessel rich tissue.
Uptake of inhalation agents is more rapid.
Diminished liver & kidney function.
NB are sensitive to CNS depressants.
Intramuscular absorption is unreliable.
Preoperative Evaluation
History:
course of preg. Mode of deliver, premature
labor, sickle cell dis.,…..
 NB of IDDM have a sig. decrease in
myocardial contractility in 1st few days of life.
 There is sig. dep. Of neonates if the mother
received large doses of narcotics or MgSo3 .
 Evaluation of organ systems is necessary.
Premedication
 The only premedication is atropine < 10 Kg.
 Older children IM opiates + atropine or
hyoscine are commonly used.
 Ketamine is also commonly used in children
but not neonates.
Induction Of Anesthesia
 Awake intubation.
 Inhalational induction.
 IV induction.
Maintenance Of anesthesia
 Inhalational + MR + CMV.
 Reverse MR at the end of surgery.
 Awake extubation.
 Return to incubator.
Monitoring
 Precordial stethoscope.
 BP with suitable cuff size.
( width of cuff = 2/3 length of arm )
 IBP through umbilical artery catheter in NB.
 ECG.
 Oxygen saturation.
 End-tidal CO2 .
 Inspired O2 conc.
 Temperature.
Doses of Some Drugs Used In
Pediatric Anesthesia
 Atropine
0.01mg/Kg
 Morphine
0.1mg/Kg
 Meperidine
1mg/Kg
 Prostigmine
0.02 – 0.04 mg/Kg
+ atropine 0.02 -0.03 mg/Kg
Caudal Anesthesia
 Use 23 gauge & ¾ inch long needle.
 For cont. Epidural a 22 g cannula can be used.
 The dose of Lidocaine calculated by the
equation: y = 0.056 × BW (Kg )
 It produce analgesia up to T 6 – 8.
 Or ½ ml/Kg of 1.5 % lidocaine.
 Infants have less toxicity than adults.
Always Remember That:
 Our 1st responsibility in any critically ill patient is to
resuscitate & then give anesthesia as tolerate.
 NB feel pain as children & adults.
 It is unacceptable technique to give only MR in
NB even if stable.
 Always monitor fluid balance and keep IV fluids warm.