Question 12

Compare and contrast the methods of delivery of beta-2 agonists in intubated patients.

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College Answer

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".


Metered dose inhaler





Easy to set up

Lowest toxicity

Does not break the circuit


Low toxicity

Certainty regarding dose delivery

No need to break the circuit


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

Undesirable systemic effects, including hemodynamic effects and lactic acidosis



Brémont F, Moisan V, Dutau G.Continuous subcutaneous infusion of beta 2-agonists in infantile asthma. Pediatr Pulmonol. 1992 Feb;12(2):81-3.