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 AdministrationDrug Response

TimeAdministration Preparation Side effects

SyntheticColfosceril (Exosurf)

Slow in onset (several hours)

During CMV breath, two divided doses

Reconstituted No proteins to stimulate immune response

NaturalBeractant (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 Mixture (homogeneous) (heterogeneous or homogeneous)

elements compounds 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

(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 excess solute.

(C) Supersaturation solution - Heating the solution dissolves more solute particles.

Concentrations of solutions

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 semi-permeable 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.

• Attempting to have equal concentrations on both sides of membrane.

Solution 0.9%

Cell 0.5% Solution

0.9%Cell

0.5%

Cell shrinks

Water Movement

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% salineFluid moves from cells into vasculature

Cells shrink - crenation

0.9% 0.9% 0.9%

3%

Hypotonic

• Lower concentration that cause cells to swell (hemolysis)

IV 0.45% salineFluid moves into cells from vasculature

Cells swell - hemolysis

0.9% 0.9% 0.9%

0.45%

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