Paediatrics - Durban University of Technology

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Transcript Paediatrics - Durban University of Technology

PAEDIATRICS
EMC IV
2015
ADULT VERSUS CHILD
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Anatomy
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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.
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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,
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fat and protein) and plasma protein binding.
Metabolism- At normal doses some drugs may cause toxicity.
 Excretion- Immature kidneys, therefore elimination of drugs
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affected.
(Porter, 2011)
FLUID THERAPY
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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).
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The 3 types of fluid therapy are:
Maintenance
 Deficit
 Replacement
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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.
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Weight-based formula- preferred method to calculate a
drug dosage.
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Body surface area-based formula- complex and timeconsuming.
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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).
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WEIGHT ESTIMATION METHODS
Healthcare provider or parent guessing
 Age-based
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APLS
 Leffler’s
 Luscombe’s
 Best Guess etc.
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Length-based
PAWPER
 Broselow
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Miscellaneous
Mercy tape
 Haftel formula
 Bavdekar Formula
 Carroll Technique
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Mercy Tapehttps://www.innovateforchildren.org/projects/weightmeasurement-tapes
PAWPER
Tape with
body
habitus
Broselow Tape
REFERENCES
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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.