a brief description of the pediatric surgical physiology

2. By
Dr.Hisham H.Ahmed, M.D,PhD,MRCS.Eng
Professor of General & Pediatric Surgery
PEDIATRIC SURGICAL PHYSIOLOGYPEDIATRIC SURGICAL PHYSIOLOGY

3. INTRODUCTION
 Pediatric patients include neonates (less than 30 days of
age), infants (1-12 months of age), and children (1-12 years
of age) who are not merely small adults.
 Their successful and safe surgical and anaesthetic
management depends on an appreciation and clear
understanding of the physiologic, anatomic, pharmacologic
and psychologic differences between each group and
adults.
 The smaller size, immature organ systems, and differing
volume capacities present unique challenges toward
perioperative management. .

4. 1- Respiratory Function
2- Cardio-circulatory Function
3- Fluid and Electrolyte Regulation
4- Thermal Regulation
5- Metabolic Problems
Key areas of concern in the newborn include:

5. 6- Nutrition
7- Stress Response to Surgery
8- Infection in the newborns
9-Control of pain
10- Rate of deterioration
Key areas of concern in the newborn include:

6. 1-Respiratory Function
► A- Adequate ventilation in an infant may be impaired by;
 Immaturity of the pulmonary tissues
 Tiny air passages that are easily occluded by edema or
secretions.
 Narrow nasal passages
 Small pharynx
 High larynx (C3)
 Large tongue
 Long Mobile epiglottis
 Short trachea and neck

7. 1-Respiratory Function
► B- Increase Oxygen demand required for
their relatively high metabolic rate;
 Oxygen consumption in the neonate is 6 ml/Kg/min versus 3
ml/Kg/min in the adult.
 The process of pulmonary alveolar maturation is not
complete until 8-10 years of age.
 The number of saccules and primitive alveoli in the lung of
a neonate is only 8% of the number of the alveoli in an
adult.
 Alveolar ventilation in a neonate is twice that of the adult
( 100-150 ml/Kg/min versus 60 ml/Kg/min).

8. 1-Respiratory Function
►C-Normal pediatric respiratory rate for
infants, newborn, toddlers, and children
Groups of children Their ages Normal respiratory
rate
Newborns and infants Up to 6 months old 30-60 breaths/min
Infants 6-12 months old 24-30 breaths/min
Toddlers and children 1-5 years old 20-30 breaths/min
Children 6-12 years 12-20 breaths/min

9. 2-Cardio-circulatory Function
A satisfactory circulating blood volume is the most
important factor in determining whether an operation can be
undertaken safely, and in the absence of cardiac failure.
 The blood volume of a newborn infant is
approximately 10% of the total body weight.
 High hematocrit in the first few days of life (>50%) .
 A minimal deficit of 25% can lead to acute
hypovolemic shock.

10. 2-Cardio-circulatory Function
 A single surgical sponge may absorb as much as
20 ml of blood ( a few saturated sponges may prove
sufficient to precipitate shock).
 Transfusion of blood is given for losses >10% of the blood
volume. A transfusion of 10 ml/Kg is approximately equivalent
to the administration of a single unit of whole blood to a 70 Kg
adult.
 An infant can tolerate rapid infusion of 20-25 ml/Kg of whole
blood or plasma without ill effect.

11. * Normal ranges of blood pressure in children
Age Normal range
SBP (mmHg)
Normal range
DBP (mmHg)
Premature 55-75 35-45
0-3 months 65-85 45-55
3-6 months 70-90 50-65
6-12 months 80-100 55-65
1-3 years 90-105 55-70
3-6 years 95-110 60-75
6-12 years 100-120 60-75
Over age 12 110-135 65-85

12. Normal heart rates (Resting) in children
Age Normal range (resting)
Premature 120-170 b/m
0-3 months 100-150 b/m
3-6 months 90-120 b/m
6-12 months 80-120 b/m
1-3 years 70-110 b/m
3-6 years 65-110 b/m
6-12 years 60-90 b/m
Over age 12y 55-85 b/m

13. 3-Fluid and Electrolyte Regulation
In managing the pediatric surgical patient, an understanding of fluid and
electrolyte balance is critical, as the margin between dehydration and fluid
overload is small.
• The total body water (TBW) of a newborn is 75-80% at term
gestation, decreased by 4-5% during the first week of life.
• The glomerular filtration rate (GFR) of the newborn is 25%
that of the adult.
• The GFR rapidly rises during the first week of life and then
slowly increases to adult levels by 2 years of age.

14. 3-Fluid and Electrolyte Regulation
 The immaturity of the newborn kidney contribute to the inability
to concentrate and conserve fluid and electrolyte, and so rapid
development of respiratory and metabolic acidosis or alkalosis.
 The normal urinary output in adequately hydrated
infant should approximate 1-2 ml/kg/hr.
♠ What is the maintenance IV fluid for children?
D5 ¼ NS + 20 mEq KCL
♠ How are maintenance fluid rates calculated in children?
4,2,1 per hour
*4 cc/kg for the first 10 kg of Body weight
*2 cc/kg for the second 10 kg of body weight
*1 cc/kg for every kilogram over the first 20 kg.

15. 4-Thermal Regulation
Newborn infants are potentially thermolabile as a
consequence of;
 Increased body surface area relative to weight.
 Thinner layer of insulating S.C fat.
 Immature thermal regulatory mechanisms.
 Incomplete myelination of the heat regulating
center in the hypothalamus

16. 4-Thermal Regulation
 Inadequate vasoconstriction of cutaneous
vessels in response to cold.
 Minimal shivering and sweating mechanisms.
All premature babies and most neonates will require incubators or
at least wrapping of limbs and body with cotton wool to minimize heat loss.

17. 4-Thermal Regulation
Normal Temperatures by Age and Method
Age Oral Rectal Axillary
(Armpit)
Ear
0-2 years - 97.9-100.4 94.5-99.1 97.5-100.4
3-10 years 95.9-99.5 97.9-100.4 96.6-98.0 97.0-100.0
Over age
11
97.6-99.6 98.6-100.6 95.3-98.4 96.6-99.7
To convert to Celsius (F-32)x5/9=c

18. 5-Metabolic Regulation
There are 3 major potential metabolic abnormalities
that can be occurred in a neonate.
2-Hypocalcaemia
3-Hyperbilirubinemia1-Hypoglycaemia

19. 5-Metabolic Problems
►1-Hypoglycaemia;
It’s common and dangerous
complications in the newborn
stressed by surgical trauma or
disease .
It’s due to
♠ Deficiency of glycogen stores
♠ Impaired gluconeogenesis
♠ Difficulties with insulin regulation
►2-Hypocalcaemia;
(especially in premature infants)
Overall, one of the most common
causes of hypocalcemia is renal
failure because of inadequate
1-hydroxylation of 25-hydroxyvitamin D.
Other causes of hypocalcaemia:
♠ Prematurity
♠ Birth asphyxia
♠ Exogenous phosphate load
♠ Hypoparathyroidism
♠ Abnormal vitamin D production
♠ Intrauterine growth retardationN.B; The normal range of glucose
production in a newborn is
about 5-8 mg/kg/min.

20. 5-Metabolic Problems
►3-Hyperbilirubinaemia; (Neonatal Jaundice)
♦ It is virtually a normal physiological occurrence in almost all
newborn especially in the first 3-7 days.
♦ It is the result of accumulation of unconjugated bilirubin in
healthy neonates.
♦ In white and black infants the peak level of bilirubin is ~6 mg/dl at 72
hours of age. In Asian infants the bilirubin level peaks later(3-5days)
at a higher level ~ 12 mg/dl.
♦ Bilirubin is neurotoxic and can cause death in newborns or Kernicterus
which is a bilirubin staining of the basal ganglia, thalamus, cerebellum,
hippocampus, and cranial nerve nuclei leading to long-term sequelae
in children.

21. 5-Metabolic Problems
Neonatal physiologic jaundice results from simultaneous
occurrence of the following 2 phenomena;
♥ Increased bilirubin production because of increased
breakdown of fetal erythrocytes.
♥ Hepatic excretory capacity is low both because of low
concentrations of the binding protein and low activity of
glucuronyl transferase enzyme
Jaundice in infants that persists longer than 2 weeks should not be considered
Physiologic, especially if the predominant fraction is conjugated bilirubin .

22. 6-Nutrition
♣ Because of limited caloric reserves and the high demands due to
rapid growth and maturation, maintenance of adequate nutritional
support is of paramount important.
♣ The best feed for infant is fresh maternal breast milk, if not possible,
parentral feeding should be started, using solutions of amino acids
(Vamin),fats (Intralipid 10% or 20%) and carbohydrates ( Dextrose)
with electrolytes, vitamins and trace elements via a central venous or
peripheral venous line.

23. 6-Nutrition
Caloric requirements by age for the following patients
• Premature infants
• Children < 1 year
● Children ages 1-7 years
● Children ages 7-12 years
● Children ages 12-18 years
80 kcal/kg/day
100 kcal/kg/day (90-120)
85 kcal/kg/day (75-90)
70 kcal/kg/day (60-75)
40 kcal/kg/day (30-60)

24. 7- Stress Response to Surgery
♣ The endocrine and metabolic response to surgical stress in newborn is
characterized by catabolic metabolism.
♣ An initial elevation in catecholamines, cortisol and endorphins upon
stimulation by noxious stimuli occurs.
♣ Responsiveness during the first week of life is diminished , due to
immaturity of the adrenal gland.
♣ During surgical stress newborn release glucose, fatty acids, ketone
bodies and amino acids necessary to meet body energy needs in time
of increased metabolic demands.
♣ Early post-operative parenteral nutrition can result in significant rate of
weight gain due to solid tissue and water accumulation.

25. 7- Stress Response to Surgery
* ACTH
* Endorphins
* Growth hormone
* Vasopressin (ADH)
* Prolactin
* Catecholamine
* Aldosterone
* Cortisol
* RAS activation
* Temperature
* O2 consumption
* CO2 production
* Urinary potassium loss
* Blood glucose level
* Salt and water retention
* Mobilization of fatty acids.
* Insulin resistance.
A-Hormonal
Response
B-Metabolic
Response

26. 7- Stress Response to Surgery
Phases of the metabolic response;
1-Catabolic phase(3-10 days)
a-Ebb; is the initial phase occurring within the 1st
24 hours
where a decrease in metabolic rate is seen
b-Flow; is the next phase which is associated with an increase
in metabolic rate.
2-Anabolic Phase ( 10-60 days)
Characterized by replacement of lost tissues

27. 7-Stress Response to Surgery
Factors contributing to a prolonged catabolic response
 Degree of neuro-endocrinal maturation
 Duration of operation
 General condition of the patient
 Amount of blood loss
 Type of surgical procedure
 Type of pathology
 Extent of surgical trauma
 Associated conditions ( hypothermia, prematurity, etc.).

28. 8- Infection in Newborn
 In stable newborn infants the intra-cellular phagocytosis-killing of
bacteria is normal, but with the added stress of sepsis or operation
there is a significant decrease in bactericidal activity as a result of
the immunosuppressive effect of operation and anaesthesia.
 Gram +ve ( staphylococcus aureus or albus) and gram –ve (E-coli)
sepsis account for the major and most serious infections, that may
lead to severe acidosis, hypothermia and circulatory collapse in
late cases.
 Broad spectrum antibiotics are indicated when complex surgical
procedures are performed in neonates

29. 9- Pain Control
♠ The past 20 years have seen many changes in the understanding and treatment
of acute pain in infants and children.
♠ The first step was to disprove the previously held misconceptions that neonates,
infants and children did not feel or react to pain like adults.
♠ This belief was based on the misconception of the immaturity of the CNS of
infants made them less likely to perceive pain.
♠ This theory compounded by fears of addiction and adverse effects from opioids,
resulted in the inadequate treatment of pain.

30. 9- Pain Control
♠ Recent studies have shown that infants and children experience a severity of
postoperative pain similar to adults and that even premature infants demonstrate
alterations in heart rate, blood pressure, and oxygen saturation in response to
painful stimuli.
♠ Considerations in the treatment of acute pain includes;
* The severity of pain
* The setting in which it is treated
(inpatient Vs outpatient)
♠ One approach is to use a three step ladder, initially described by the World
Health Organization for the treatment of cancer related pain.

31. 9-Pain Control
The World Health Organization Ladder for Pain Control
♣ Mild Pain
-1- NSAIDs
-2-Acetaminophen
♥ Moderate Pain
1 - NSAIDs or acetaminophen with a weak opioid ( codeine)
2- Intravenous opioid with addition of fixed interval NSAIDs or
acetaminophen either;
a- IV opioid by (PCA)
b- Continuous infusion of opioid with as needed rescue doses
of opioid.
c- Fixed interval dosing of opioid
3- Regional anesthetic techniques
♠ Severe Pain ( continue use of NSAIDs or acetaminophen)
1- IV opioid by PCA
2- Regional anesthetic technique

32. 9- Pain Control

33. 10-Rate of Deterioration
♥ Newborns deteriorates rapidly than
adults.
♥ A child can become dehydrated from
gastroenteritis to the extent of
peripheral circulatory failure in a day.