29-09-22 – IV Drug Administration Flashcards
Learning outcomes
- To explain the indications/contraindications for, the advantages/disadvantages of, and the risks associated with intravenous drug therapy.
- To identify the types of intravascular devices (including delivery devices and drivers) that may be used to deliver drugs and fluids.
- To interpret the effects of varying basic pharmacokinetic parameters (e.g. clearance) upon the plasma concentration of IV drugs following bolus, continuous or intermittent infusions.
What are 6 reasons for IV administration?
- Reasons for IV administration:
1) Medicine is not available in another form
2) Cannot tolerate medication by another route
3) Constant or high blood level of medicine is needed
4) A rapid onset of effect is needed
5) Some medications are more effective via IV
6) Rarely, to ensure compliance (patients following their medicine plan)
What are disadvantages of IV administration?
When should oral route be used?
- Disadvantages of IV administration:
1) Increased cost and time to administer the medicine
2) Requires trained staff to administer (plus location)
3) Rapid onset of action
4) Volume of fluid needed to dilute the medicine
5) Can cause discomfort/pain to the patient
6) Health risks (e.g. infection) - The oral route should be used when possible
What are 3 different types of intravascular devices (IVDs)?
- Different types of intravascular devices (IVDs):
1) Peripheral venous catheters (PVC)
* Catheter placed into a peripheral vein to administer intravenous therapy
* Usually inserted into lower part of the arm or the back of the hand
2) Central venous catheter (CVC)
* AKA central line
* Can stay in place longer than PVCs
* Tube that doctors place in a large vein in the neck, chest, groin, or arm to give fluids, blood, or medications or to do medical tests quickly.
* If medicine is delivered to a large volume of blood in larger veins, this can decrease the concentration of the medicine, making it safer
* Can deliver large amounts of fluids
- There are two other types of CVCs: Peripherally inserted CVCs (PICC) and Skin tunnelled CVCs (e.g Hickman and Broviac lines)
- Peripherally inserted central catheter (PICC).
- A PICC is a thin, flexible tube that is inserted into a vein in the upper arm and guided (threaded) into a large vein above the right side of the heart called the superior vena cava.
- It is used to give intravenous fluids, blood transfusions, chemotherapy, and other drugs.
- Skin tunnelled CVCs (e.g Hickman and Broviac lines)
- Can be used in order to have multiple access points for multiple medications
3) Arterial catheters
* An arterial catheter is a thin, hollow tube that is placed into an artery in the wrist, groin, or other location
* Intra-arterial catheters (also called arterial cannulas or A-lines) are often inserted for invasive blood pressure (BP) monitoring and intravascular access for blood sampling in high-risk surgical and critically ill patients.
Skin tunnelled CVC and Arterial Catheter
Skin tunnelled CVC and Arterial Catheter
What is the half-life of a drug?
What does drug stability mean?
What are the 3 methods of administering intravenous medications?
What types of medicals are infused with each type?
- The half-life of a drug is the time it takes for the amount of a drug’s active substance in your body to reduce by half (how fast drugs are metabolised)
- The term drug stability refers to the extent to which a drug substance or product retains, within specified limits and throughout its period of storage and use, the same properties and characteristics that it possessed at the time of its manufacture.
- 3 methods of administering intravenous medications:
1) Continuous infusion
* Stable drugs – if drugs break down rapidly, it would change the drug concentration
* Short half-life drugs
* Time dependent effects
* Needs dedicated IV site
2) Intermittent infusion
* Unstable drugs
* Long half-life drugs
* Concentration dependent effects
* Less compatibility concerns – as there is time the patient isn’t on the drug
3) Bolus injection
* 1 off drug is administered over the course of 5-10 minutes
* Rapid response - This can ensure rapid response, while making sure that the effects of an anaphylactic response won’t be too catastrophic
* Useful for unstable drugs - as they can’t be stored for a long period of time
* Useful for drug incompatibilities - we can administer the drug to a place that it won’t interact with another drug
What are the 7 complications of IV drug administration?
What is the difference between hypersensitive and anaphylaxis?
- Complications of IV drug administration:
1) Fear / Phobia / Pain
2) Infection / Sepsis
3) Thrombophlebitis
* An inflamed vein near the surface of the skin caused by a blood clot is known as superficial thrombophlebitis.
4) Infiltration / Extravasation
* Infiltration is when the needle can go into the vessel wall/tissue instead of the lumen, which can lead to general inflammation.
* Extravasation is infiltration, but with toxic substances that can cause extensive tissue damage e.g chemotherapy
5) Emboli
* An embolus is anything that moves through the blood vessels until it reaches a vessel that is too small to let it pass.
* When this happens, the blood flow is stopped by the embolus.
* An embolus is often a small piece of a blood clot that breaks off (thromboembolus).
* Thromboemboli cause thrombophlebitis
6) Hypersensitivity / Anaphylaxis
* Hypersensitivity reactions are exaggerated or inappropriate immunologic responses occurring in response to an antigen or allergen
* Anaphylaxis is a severe and potentially life-threatening reaction to a trigger, such as an allergy.
* Type I hypersensitivity reaction is the most widely known type of allergic reaction and includes anaphylaxis
* An allergic reaction typically refers to the signs and symptoms a person may experience, while a hypersensitivity reaction describes the immunological process that occurs in the body.
* this is where the body reacts to a stimulus, or allergen, leading to swelling of the airways, and cardiovascular and other organ system effects.
7) Overdose
What is the visual infusion phlebitis score?
Visual infusion phlebitis score
What is red man syndrome?
What symptoms and signs does red man syndrome present with?
What causes red man syndrome?
What 2 ways can the incidence of red man syndrome be reduced?
- Red man syndrome is a hypersensitivity reaction due to histamine release
- Symptoms and signs red man syndrome presents with:
1) Erythematous (exhibiting abnormal redness of the skin or mucous membranes due to the accumulation of blood in dilated capillaries) rash of face, neck, and upper torso
2) Diffuse burning, itching, generalised discomfort
3) In rare cases: hypotension, angioedema (swelling of deep layers of skin due to fluid build-up), chest pain, dyspnoea
- Red man syndrome is caused by infusing patient too quickly with vancomycin, which is used to treat MRSA (Methicillin-resistant Staphylococcus aureus)
- 2 ways the incidence of red man syndrome be reduced:
1) Slowing infusion rate
2) More dilute drug solution
What is vancomycin administered for?
How is vancomycin administered?
- Vancomycin is administered continuously for patients with severe/ deep seated infections (e.g pneumonia, endocarditis, bone and joint infections)
- Can be infused intermittently (pulsed) on occasion
- When infusing vancomycin, we give a larger initial dose (loading dose) based on patient bodyweight to get our patient’s blood plasma concentration boosted
- This loading dose is diluted to a certain concentration and given over a long period of time to reduce the risk of inducing red man syndrome
- We then give a lower concentration of vancomycin over a longer period of time to maintain boosted plasma levels
- We can decide what we want the plasma concentration to be maintained at and adjust the lower dose accordingly
What are 3 complications of IV drug administration?
- Complications of IV drug administration:
1) Insufficient mixing
* This can vary the concentration the patient is exposed to (i.e if all the drug goes to the bottom of the IV bag, this will lead to great concentration of infused liquid)
* Ensuring that what you are infusing isn’t precipitating out and risking the formation of an emboli
2) Stability of medicines in solution
* Certain medicines can become unstable due to the following factors:
1) Light (e.g. total parenteral nutrition [TPN])
2) Temperature (e.g. insulin, TPN)
3) Concentration (e.g. amiodarone)
4) pH (e.g. midazolam - precipitates out of solution due to pH)
3) Interaction of medicines with the syringe/bag
What is bioavailability?
What is the bioavailability of IV injections?
How do curves for the plasma concentration of drug against time differ with continuous infusion of drug, intermittent infusion once a day, and intermittent infusion twice a day?
- Bioavailability is the fraction of unchanged drug that reaches the systemic circulation
- IV injection gives 100% of bioavailability, as it doesn’t have any barriers to go through to reach systemic circulation
- The curve for plasma concentration of drug against time with continuous infusion of plasma is smooth and plateaus
- The curve for plasma concentration of drug against time with intermittent infusion once a day has peaks and troughs
- The curve for plasma concentration of drug against time with intermittent infusion twice a day has smaller peaks and troughs
- They all roughly average out to make the same plasma concentration of blood
Why does continuous infusion not lead to a linear increase in blood plasma concentrations of drug?
What effect does this have on the graph?
What is this plateau called?
What does the time taken to reach Css depend on?
What is the elimination half-life of a drug?
What is related to the amount of drug eliminated per unit time?
- Continuous infusion does not lead to a linear increase in blood plasma concentrations of drug because drug is being eliminated from the body as soon as it is in the circulation
- This leads to the graph of plasma concentration of drug against time for most infusions bending towards a plateau
- This plateau is called the ‘steady state’ or Plasma steady state concentration (Css), and is where the rate of drug infusion matches the rate of elimination (metabolism)
- Css = infusion (X) / Clearance (CL)
- The time taken to reach Css depends on the elimination half-life (t1/2) of a drug,
- The half-life of a drug is the time it takes for the amount of a drug’s active substance in your body to reduce by half (how fast drugs are metabolised)
- For most drugs, the amount of drug eliminated per unit time is related to the concentration of drug in the plasma (first-order kinetics):
- Higher concentrations, more drug is removed per unit of time
- Lower concentrations, less drug is removed per unit of time
What is clearance (CL)?
What can be classed as part of clearance?
What is CL in first order kinetics?
What is an analogy to think related to this?
- Clearance (CL) is defined as the volume of blood or plasma cleared of drug in a unit time e.g 10ml/min
- Clearance is anything that removes drug from the body e.g kidneys, liver
- In first order kinetics, whilst amount of drug eliminated per unit time varies based on concentration, CL is constant (e.g cant clear a greater volume of blood in a shorter amount of time, can only stay the same)
- Analogy
- Bath filled with water and glitter
- A cup (clearance) of bath water and glitter are removed and strained to removed the glitter, with the bath water returned afterwards
- The glitter concentration decreases, but will decrease less and less with every cup strained (amount of drug eliminated per unit time varies based on concentration)
- The cup can’t remove any more water at 1 time (clearance)
Formulas with plasma steady state concentration (Css)
What does Vd equal?
Vd = volume of distribution, and is the total volume of fluid that the drug has gone into
Formulas with plasma steady state concentration (Css)
How does curve for rate of removal of drug from blood compare with the curve for rate of infusion of drug into the blood?
How many half-lives does it take to reach Css?
How many half lives does it take to remove all of the drug from the system after infusion stops?
- The curve for rate of removal of drug from blood follows the same profile for the curve for rate of infusion of drug into the blood
- It takes roughly 5 half lives to reach Css
- After infusion stops, it also takes roughly 5 half lives to remove all of the drug from the system
- E.g if 1 half-life of a drug is 2 minutes, it will take 10 minutes to each Css, and 10 minutes to completely remove the drug from the body after infusion stops.
