Compare and contrast the methods of delivery of beta-2 agonists in intubated patients.
Consideration should be given to pharmacodynamics (dose requirements, side effect profile, effectiveness), as well as cost and other interrelated effects. Methods of delivery include intravenous, sub-cutaneous, via metered dose inhaler and via nebuliser.
Intravenous: excellent systemic delivery assured, but to areas that are perfused. Systemic effects maximal so side effects are more pronounced.
Sub-cutaneous: easy to administer, but less predictable effects as delayed peak effect and lower bioavailability. Systemic side effects still prominent.
Metered dose inhaler: easy to administer via adapter; many multiples of non-
intubated dose are required [eg. 10 puffs per treatment]; does not require breaking of ventilatory circuit; very low bioavailability, optimal via inline spacer (but adds cost, breaks circuit at least once, may become reservoir for infection); minimal systemic side effects.
Nebuliser: can be given continuously; maximises local delivery while minimising systemic absorption; easy to administer but requires specific equipment; requires break in circuit for each treatment; variable interaction with ventilator [some cannot compensate for flow].
Prior to reading this question, I was not aware that beta-2 agonists could be given subcutaneously.Turns out, people have done this to infants, and "no local or general adverse reactions were observed".
Features |
Metered dose inhaler |
Nebuliser |
Intravenous |
Advantages |
Cheap Easy to set up Lowest toxicity Does not break the circuit |
Cheap Low toxicity |
Certainty regarding dose delivery No need to break the circuit |
Disadvantages |
Spacer adds dead space into the circuit Drug precipitation occurs in the upper airways and the tubing Needs to be timed with ventilator breaths Unreliable drug delivery to the site of action |
Drug precipitation occurs in the upper airways and the tubing Unreliable drug delivery to the site of action |
Greatest toxicity
|
Brémont F, Moisan V, Dutau G.Continuous subcutaneous infusion of beta 2-agonists in infantile asthma. Pediatr Pulmonol. 1992 Feb;12(2):81-3.