Paediatrics - Durban University of Technology
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Transcript Paediatrics - Durban University of Technology
PAEDIATRICS
EMC IV
2015
ADULT VERSUS CHILD
Anatomy
upper and lower airway
anatomy.
less compliant ventricles in
the myocardium.
larger skin surface area.
poorly formed blood brain
barrier.
These anatomical differences
may then result in a
difference in physiology.
mike.shannonandmike.net
PHYSIOLOGY
Physiologically, neonates have differences in
various systems following separation from the
placenta.
Many of these functions resolve within a few days
or weeks following birth, but others only years later
(Porter, 2011).
This becomes relevant for drug dosing!
PHARMACOKINETICS
Absorption- GI changes
Distribution- depends on 2 factors: body composition (water,
fat and protein) and plasma protein binding.
Metabolism- At normal doses some drugs may cause toxicity.
Excretion- Immature kidneys, therefore elimination of drugs
affected.
(Porter, 2011)
FLUID THERAPY
Requirements for children are higher than those for
adults for multiple reasons:
“the higher metabolic rate of children requires a greater
caloric expenditure, which translates into higher fluid
requirements.”
“children, especially infants, have a much higher body
surface area to weight ratio, and this translates into
relatively more water loss from skin compared with adults.”
“children, especially infants, have higher respiratory rates,
and this equates to higher insensible losses from the
respiratory tract” (Meyers, 2009).
The 3 types of fluid therapy are:
Maintenance
Deficit
Replacement
DRUG-DOSING
Drug dosing in children can be done using:
Age-based formula- may be ineffective due to the
varying growth patterns of children today and does not
accurately reflect the pharmacokinetics at that specific
developmental age.
Weight-based formula- preferred method to calculate a
drug dosage.
Body surface area-based formula- complex and timeconsuming.
Allometric scaling- complicated and no longer used.
VOLUME OF DISTRIBUTION
Total body weight (TBW) is the actual mass in
kilograms weighed on a scale.
The ideal body weight (IBW) is an estimation of
weight based on sex, height and frame size.
The lean body weight (LBW) is the TBW minus
the fractional fat mass (measured using skinfold
thickness or underwater weighing).
The adjusted body weight (ABW) is calculated by
adding a correction factor above the IBW to
normalize the volume of distribution (Green &
Duffull, 2004).
WEIGHT ESTIMATION METHODS
Healthcare provider or parent guessing
Age-based
APLS
Leffler’s
Luscombe’s
Best Guess etc.
Length-based
PAWPER
Broselow
Miscellaneous
Mercy tape
Haftel formula
Bavdekar Formula
Carroll Technique
Mercy Tapehttps://www.innovateforchildren.org/projects/weightmeasurement-tapes
PAWPER
Tape with
body
habitus
Broselow Tape
REFERENCES
Berlin, C., 2013. Pharmacokinetics in Children. [Online] Available at:
http://www.merckmanuals.com/professional/pediatrics/principles_of_drug_treatment_i
n_children/pharmacokinetics_in_children.html [Accessed 6 June 2014].
Carasco, C., Fletcher, P. & Maconochie, I., 2012. Review of commonly used age based
weight estimates for paediatric drug dosing in relation to the pharmacokinetic
properties of resuscitation drugs. Archives of Disease in Childhood, 97(3), pp.A147-49.
Fernandez, E. et al., 2011. Factors and Mechanisms for Pharmacokinetic Differences
between Pediatric Population and Adults. Pharmaceutics, 3(1), pp.53-72.
Green, B. & Duffull, S., 2004. What is the best size descriptor to use for
pharmacokinetic studies in the obese? British Journal of Clinical Pharmacology,
58(2), pp.119-33.
Meyers, R.S,. 2009. Paediatric fluid and electrolyte therapy. Journal of Paediatric
Pharmacological Therapy. 14 (2), pp.204-211.
Porter, R., 2011. Merck Manual. 19th ed. New Jersey: Merck.
Tayman, C., Rayyan, M. & Allegaert, K., 2011. Neonatal Pharmacology: Extensive
Interindividual Variability Despite Limited Size. Journal of Pediatric Pharmacology
and Therapeutics, 3(16), pp.170-84.
Wells, M., 2009. Weight prediction in children in the emergency department. Master
of Science in Medicine in Emergency Medicine, University of Witswatersrand,
Johannesburg.
Wells, M., Goldstein, L. & Botha, M., 2012. Emergency Drug Dosing in Children: A
Resuscitation Aid for Paediatric Emergencies. 1st ed. London: Elsevier.