Respiratory Therapy
Pharmacology
Week 7
Exogenous Surfactant Administration
• Indicated for surfactant deficiency, such as
in infant respiratory distress syndrome and
following lung lavage
Exogenous Surfactant Administration
• Produced synthetically or naturally
• Administered by direct instillation into the
trachea
•
http://www.youtube.com/watch?v=4VwdsdOBwtQ
Exogenous Surfactant Administration
Drug
Response
Time
Administration
Preparation
Side effects
Synthetic
Colfosceril
(Exosurf)
Slow in onset
(several
hours)
During CMV
breath, two
divided doses
Reconstituted
No proteins to stimulate
immune response
Natural
Beractant
(Survanta)
Rapid onset
(5 – 30 min)
Four divided
doses
Refrigerated
suspension
Proteins may elicit
immune response
Surfactant
•
Surfactant is a complex substance containing phospholipids and a number of
apoproteins. This essential fluid is produced by the Type II alveolar cells, and lines
the alveoli and smallest bronchioles. Surfactant reduces surface tension
throughout the lung, thereby contributing to its general compliance. It is also
important because it stabilizes the alveoli. Laplaces Law tells us that the pressure
within a spherical structure with surface tension, such as the alveolus, is inversely
proportional to the radius of the sphere. That is, at a constant surface tension,
small alveoli will generate bigger pressures within them than will large alveoli.
Smaller alveoli would therefore be expected to empty into larger alveoli as lung
volume decreases. This does not occur, however, because surfactant reduces
surface tension, more at lower volumes and less at higher volumes, leading to
alveolar stability and reducing the likelihood of alveolar collapse. Surfactant is
formed relatively late in fetal life; thus premature infants born without adequate
amounts experience respiratory problems associated with immature lungs
Surfactant
• The baby presents with retractions (inward
movement of intercoastals on inspiration), grunting
(an attempt to increase FRC with back pressure),
cyanosis, and tachypnea. Babies born with
insufficient surfactant are determined to have a
disease called RDS (respiratory distress syndrome) or
Hyaline Membrane Disease. Surfactant can be
distilled into the lungs following birth manually down
an ETT.
Surfactant
• Common Surfactants Used: Infasurf (synthetic), Survanta (modified
natural bovine lung extract), Exosufr neonatal, Curosurf (Pig extract)
• Classification: Natural or synthetic surfactant used to treat prematurely of
the lung as demonstrated by RDS.
• How it works: The active component colfosceril palmitate
(dipalmitoylphosphatidylcholine) is the major surface active component of
natural lung surfactant and acts by forming a stable film that stabilizes the
terminal airways by lowering the surface tension of the pulmonary fluid
lining them. The lowered surface tension prevents alveolar collapse at
end-inspiration; the hysteresis effect equalizes the distension of adjacent
alveoli and hence prevents over distension which might result in alveolar
rupture and pulmonary air leak.
Surfactant
• Delivery Device: Through endotracheal tube, instilled with tracheal
adapter, surfactant is drawn up in syringe and instilled down ETT directly
into lungs.
• Doses: A dose of 5ml/kg birth weight of reconstituted Exosurf Neonatal, If
the baby is still intubated, a second equal dose should be given 12 hours
later by the same route. Survanta- 4cc/Kg given initially, second dose
2cc/Kg. Curosurf- 2.5 cc/Kg, second dose is the same; third dose is 1.25
cc/kg.
• Administration of exogenous surfactants rapidly improves oxygenation and
lung compliance. Following administration, patients should be monitored
so that oxygen and ventilatory support can be modified.
Medication frequency
BID= twice a day
Ad lib= as desired
TID= three times a day
Q4PRN= every 4 hours as needed
QID= four times a day
Qh= every hour
QD= once a day
NS= normal saline
QS= every shift
m.l.= militer
Q4=every 4 hours
Mg= miligrams
Q6= every 6 hours
NPO= nothing per mouth
HS= At bed time
PRN= AS NEEDED
EX: Albuterol 2.5 mg and 2.5 ml NS Q4 and Q2 PRN for wheezing.
Oximeter check QS
Solutions, Concentrations, &
Medication Delivery
Mixtures
MATTER
Pure Substance
(homogeneous)
elements
compounds
Mixture
(heterogeneous or homogeneous)
colloids suspension solutions
Heterogeneous mixtures
• Heterogeneous – colloid & suspension
– Not uniform
– Large particles
– Concentrations vary throughout
– May settle
– Can be easily separated by physical means
(filtration)
Homogeneous mixtures
• Homogeneous – solution
– Usually transparent
– Small (invisible) particles
– Will not settle
– Uniform concentration throughout
– Can be separated by physical means but not easily.
(evaporation)
Mixtures
• Three types:
–Colloids
–Suspensions
–Solutions
MIXTURES - Colloid
• Examples: Cellular protoplasm, milk,
fat in blood, proteins in blood
(albumin)
– Heterogeneous
– Large molecules
– Attract and hold water
– Usually uniformly dispersed
– Usually do not settle
– Suspended in a gel
MIXTURES - Suspension
• Examples: red blood cells in plasma
– Heterogeneous
– Large particles that float in the liquid
– Dispersed by agitation
– Will settle if agitation stops
MIXTURES - Solution
• Example: Saline (salt + water), medications,
electrolytes in body fluids
– Homogeneous
– Solute evenly dispersed throughout solvent so
concentration is same throughout
• Solute – smaller quantity dissolved, can be solid, liquid
or gas, “active ingredient”.
• Solvent – larger quantity, where solute is dissolved.
– “Aqueous” solution has water as the solvent.
Solutions - Gases in liquids
• Ability of a gas to dissolve in a liquid
depends upon :
– Henry’s Law – dissolving (into)
– Graham’s Law – diffusion (through)
– Fick’s Law - overall relationships
•
•
•
•
Surface area
Thickness
Partial pressure
Diffusion coefficient
Solutions - Solids & liquids in liquids
• Ability of a solute to dissolve in a solvent
also depends upon:
– Physical properties of solute & solvent
(density, solubility coefficient)
– Pressure of solute
– Temperature of solute & solvent
– Presence of other solutes
Concentrations of solutions
– More or less solute or solvent will change the overall
concentration of the solution.
• Dilute – small amount of solute in solvent
• Saturated – maximum amount of solute in solvent
• Precipitate – Excess solute in solvent where some solute settles
out at bottom of solvent.
– As the concentration changes, the properties of the
solution change (freezing point, boiling point…)
• Examples: salt on roads, anti-freeze in radiator
Concentrations of solutions
(A) Dilute solution
with relatively
few solute
particles.
(B)Saturated
solution where
the solvent
contains all the
solute it can
hold in the
presence of (C) Supersaturation solution - Heating
excess solute.
the solution dissolves more solute
particles.
Concentrations of Medications
• Concentration can be expressed as:
–
–
–
–
–
–
–
%weight/volume (g/mL) – solids in liquid (meds)
%vol/vol (mL/mL) – both liquids
%solution
Ratio (weight:volume or g:mL) (meds)
Molal solution
Molar solution
Parts per million or parts per billion (extremely
dilute)
Medications (drug solutions)
• Medications are solutes in solvents.
• Calculations help quantify amounts of drug
(solute) in sterile water or saline (solvent).
• Calculations also help express different
concentrations:
– %weight/volume (g/mL) – solids in liquid (meds)
– Ratio (weight:volume or g:mL) (meds)
– Parts per million or parts per billion (extremely
dilute)
Respiratory Therapy Medications
• Preparations:
– Multi dose – need to be measured and
diluted
– Unit dose – already diluted and ready to use
• Ultimate Goal of calculating is to know
how many cc or mL to administer.
Treatment Demonstration
• Nebulization of medication
– Solute = medication
– Solvent = saline or water
• Order: 2.5 mg Albuterol in 2.0 mL N/S by hand held
nebulizer Q4 hours.
–
–
–
–
–
Medication
Drug dosage
Diluent
Method of delivery
Frequency
Weight/Volume Solutions
• Weight/volume solutions are ALWAYS expressed as
a % where the percent represents the number of
grams of drug in 100ml of solvent.
– 0.5% Solution = 0.5 grams per 100 mL
– 2.25% Solution = 2.25 grams per 100 mL
– In order for us to use this, we must convert the
g/100 mL to mg/mL
– 0.5% = 0.5 grams per 100 mL OR 500 mg per 100 mL
– 2.25% = 2.25 grams per 100 mL OR 2,250 mg per 100
mL
Weight/Volume Solutions
• milligrams per ml.
•
0.5% solution contains ……. 5mg/ml
•
1% solution contains ………. 10mg/ml
•
2% solution contains ………. 20mg/ml
•
3% solution contains ………. 30mg/ml
•
4% solution contains ……… 40mg/ml
•
1:100 solution is 1%
•
1:200 solution is .5%
•
1:1000 solution is .05%
Example
• How many milligrams are in 2 ml of a 3%
solution?
• 30mg/ml • 2ml = 60mg.
• Since 3% = 30 mg/ml and the question asks
how much of this is in 2 ml, we simply multiply
30 by 2
Respiratory Therapy Medications
• Preparations:
– Multi dose – need to be measured and
diluted
– Unit dose – already diluted and ready to use
• Ultimate Goal of calculating is to know
how many cc or mL to administer.
Treatment Demonstration
• Nebulization of medication
– Solute = medication
– Solvent = saline or water
• Order: 2.5 mg Albuterol in 2.0 mL N/S by hand held
nebulizer Q4 hours.
–
–
–
–
–
Medication
Drug dosage
Diluent
Method of delivery
Frequency
Medication Example
• The physician order states that you are
to administer 2.5 mg of albuterol. You
have a 0.5% albuterol solution. How
much medication (in mL) should you
draw up?
• How many milligrams are in a 0.5% solution?
Medication Order
• Isuprel 5 mg of a 1:100 mL solution in 2mL
normal saline by small volume nebulizer Q4
hours.
– Medication
– Drug dosage
– Diluent
– Method of delivery
– Frequency
Ratio Solutions
• Ratio solutions = 1 gram/??? mL
– 1:100 = 1 gram per 100 mL
– 1:200 = 1 gram per 200 mL
» Convert to mg/mL
• 1:100 = 1000 mg per 100 mL
• 1:200 = 1000 mg per 200 mL
Medication Example
• The physician orders 5 mg of Isuprel. You
have a 1:100 solution. Determine how
much medication (in mL) to give.
– What concentration of drug do you have?
• 1:100…What does that mean?
Universal Drug Calculation
Need to convert the ratio to a percentage.
1:100 = 1/100 = .01 = .01 * 100% = 1%
Universal Drug Calculation
• The physician orders 5 mg of Isuprel. You have a 1:100
solution. Determine how much medication to give (#mL).
•
1:100 = 1% solution
Pressures in solutions


Solutes in solvents exert a pressure
Two kinds of pressure gradients exist:

Diffusion


The passive movement from an area of high
concentration to one of lower concentration
Osmotic

The movement of water from an area of low
concentration to an area of high concentration.
Diffusion
• Solute pushing across a semi-permeable
membrane
– Solute can move across membrane
• The movement will continue until there
is an equilibrium in concentrations.
Osmotic pressure
• Solvent (usually water) moving across a semipermeable membrane
– Solute cannot move across membrane.
• The movement will continue until there is an
equilibrium in concentrations.
Solvent
movement is
indicated by
arrows
through the
membranes.
Osmotic pressure
• Pressure that exists in the body because of a
solvent moving across a semi-permeable
membrane.
– Solute cannot move across membrane.
Solution
0.9%
Cell
0.5%
Cell shrinks
Solution
0.9%
Cell
0.5%
Water Movement
• Attempting to have equal concentrations on both
sides of membrane.
Tonicity
• Def: The amount of osmotic
pressure in a solution.
– Isotonic – having the same
concentration as that of the body
fluids (such as 0.9% “normal” saline)
– Hypertonic – higher concentration
that cause cells to shrink (crenation)
– Hypotonic – lower concentration that
cause cells to swell (hemolysis)
Hypertonic
• Higher concentration that cause cells to shrink
(crenation)
IV 3% saline
Fluid moves from cells into vasculature
0.9%
0.9%
0.9%
3%
Cells shrink - crenation
Hypotonic
• Lower concentration that cause cells to swell
(hemolysis)
IV 0.45% saline
Fluid moves into cells from vasculature
0.9%
0.9%
0.9%
0.45%
Cells swell - hemolysis
Dilution Example
• If you have 10cc of 20% Mucomyst
and need a 10% solution, what do
you need to do?
Question: How many cc of saline
need to be added to 10 cc of 20%
Mucomyst to obtain 10%
Mucomyst?
Dilution
• If you have 20cc of 0.9% normal saline
and need 0.3% saline, what do you
need to do?
Question: How many cc of sterile water
need to be added to 20 cc of 0.9%
Saline to obtain 0.3% Saline?
Questions
• When you add more solvent (water or saline) to a
medication will you be giving more medication
(solute)?
• When you add more solvent (water or saline) to a
medication what will happen to the concentration
(tonicity)? (increase, decrease or stay the same)
• When you add more solvent (water or saline) to a
medication what will happen to the time it takes
to aerosolize? (increase, decrease or stay the
same)
Pediatric calculations
• Body surface area (Dubois Chart)
– (Child BSA m2 / 1.73) x adult dosage
• Fried’s Rule
– Infants < 1 year
– (Infant age in months / 150 months ) x adult
dosage
• Young’s Rule
– Child 1 – 12 years
– (Child’s age in years/age + 12) x adult dosage
• Clark’s Rule
– (Child’s weight in pounds/150 pounds) x adult
dosage