of the airway. The smooth muscles of the airway also constrict, thus narrowing the passage for air exchange with an emphasis on
Standard treatments in the field and the
hospital include drugs such as albuterol, which
bronchodilates and ipratropium, which blocks
muscarinic receptors in the lungs and allows
the muscles around the airways to relax.
Other treatments include magnesium,
which is thought to stabilize T cells, thereby
limiting the production of inflammatory mediators and reducing swelling. It also acts to stimulate nitric oxide and prostacyclin production,
possibly reducing the severity of asthma. 2, 3
Epinephrine as well as terbutaline can also be
used and are potent bronchodilators working
through a beta- 2 agonist mechanism.
Ketamine is well known for its rapid onset
of behavioral control with preservation of airway reflexes, and can be given IV, IM, and
intranasal (IN). It’s a drug that’s not commonly thought of as an adjunct in the case of
severe asthma exacerbations, which served two
very important functions in the management
of this patient’s severe asthma exacerbation.
First, it served to gain behavioral control to
facilitate further treatment without the loss of
airway reflexes in a hypoxic patient. Secondly,
ketamine bronchodilates, making it another
viable treatment option in patients who are
refractory to initial therapies. This is especially
true in the case of a severe asthma exacerbation
requiring endotracheal intubation.
Ketamine will produce the necessary sedation for endotracheal intubation as well as
associated bronchodilation. It’s thought to
work both directly on the bronchial smooth
muscles and indirectly by causing the release
of endogenous catecholamines, stimulation of
the sympathetic nervous system, or inhibition
of reuptake of catecholamines. 4, 5
In one study, the beta blockade effects of
propranolol didn’t inhibit ketamine’s ability
to bronchodilate. 4 Another known anesthetic
agent to bronchodilate is propofol, however
this agent is very short acting, and can cause
apnea and hypotension. 5, 6 Ketamine can be
given to asthma patients not requiring intubation, and can also be used as a continuous
drip on both intubated and non-intubated
asthma patients. 7, 8
The severe asthmatic patient is one of the
most difficult patients for prehospital providers
to manage. First, the EMS provider’s assess-
ment needs to be accurate. Wheezing alone
can’t direct course of action. Is it an allergic/
anaphylactic reaction? Is there hemodynamic
instability? Is another obstructive lung process
to blame? Are the breath sounds equal bilater-
ally, or has your asthmatic developed a tension
pneumothorax? In the case of toddlers and
young children, have they aspirated a foreign
body? Absence of breath sounds can be a sign
of impending respiratory failure.
A detailed patient history must be taken,
if possible, including previous attacks, treat-
ment already rendered and current medi-
cations, history of previous intubations and
hospitalizations. Knowing what inhaler your
patient has been using is important as tachy-
phylaxis, develops over time from repeated use
of a medication. Also known as tolerance, it
leads to the need for higher doses to achieve
the same effect. Tachyphylaxis is common
with the beta- 2 agonists drugs used in asthma.
How much time do you have before respira-
tory arrest? The first line drugs of albuterol and
ipratropium have somewhat delayed onsets of
action in the 10–25 minute range, and steroids
even longer. 9–12 When your patient’s condi-
tion is refractory to this route of management,
something else must be considered.
Ketamine has an onset of action around
3–4 minutes when given IM, and around 60
seconds when given IV. 13
Waveform capnography will be beneficial
in monitoring this type of patient, both intubated and non-intubated. You can monitor
their expiratory phase and assess for breath
stacking and further CO2 retention. Whatever you define as your level of care, be sure to
continue treatment of the underlying problem
during your transport.
Ketamine is a consideration in conjunction
with other standard asthma medications as
part of a thorough treatment strategy in the
severe asthma patient. Endotracheal intubation of the severe asthmatic shouldn’t be
undertaken lightly. A strategy focusing on the
underlying ventilatory problem and excellent
pre-oxygenation should be the highlights of a
This case highlights the advantages ketamine
gave the crew in this including: behavioral control, bronchodilation, optimize pre-oxygenation
and continued sedation for comfort. In conjunction with appropriate ventilator settings,
an in-line DuoNeb and magnesium, ketamine
provided an effective and comfortable patient
transport on the ventilator that might otherwise
have been difficult to obtain. JEMS
1. Bledsoe B, Buchannan K, Hodnick R. Late-night wheezer:
Providers respond to pediatric asthma patient. JEMS.
2012; 37( 1): 26, 28.
2. Bichara M, Goldman R. Magnesium for treatment of asthma in
children. Can Fam Physician. 2009; 55( 9):887–889.
3. Guerrera MP, Volpe SL, Mao JJ. Therapeutic uses of magnesium. Am Fam Physician. 2009;80( 2):157–162.
4. Gateau O, Bourgain J, Gaudy J, et al. Effects of ketamine
on isolated human bronchial preparations. Br J Anaesth.
1989; 63( 6):692–695.
5. Brown R, Wagner E. Mechanisms of bronchoprotection by
anesthetic induction agents: Propofol versus ketamine. Anesthesiology. 1999;90( 3):822–828.
6. Sarma V. Use of ketamine in acute severe asthma. Acta Anaes-thesiologica Scandinavica, 1992; 36( 1):106–107.
7. Benken S, Goncharenko A. The future of intensive care unit
sedation: A report of continuous infusion ketamine as an
alternative sedative agent. J Pharm Pract. May 2, 2016. [Epub
ahead of print.]
8. Umunna BP, Tekwani K, Barounis D, et al. Ketamine for continuous sedation of mechanically ventilated patients. J Emerg
Trauma Shock. 2015; 8( 1): 11–15.
9. Albuterol. (n.d.) Medscape. Retrieved April 1, 2017,
10. Ipratroprium. (n.d.) Medscape. Retrieved April 1, 2017,
11. Decadron. (n.d.) Medscape. Retrieved April 1, 2017,
12. Solu-Medrol. (n.d.) Medscape. Retrieved April 1, 2017,
13. Ketamine. (n.d.) Medscape. Retrieved April 1, 2017,
Jennifer Keefer, BSN, CFRN, NRP, is an active flight nurse
and medic for North Colorado MedEvac and an ED/ICU/moun-tain clinic nurse for Centura Health. She can be reached at
Ryan Hodnick, DO, NRP, FAWM, is the medical director
for agencies in New Mexico including: Santa Fe Fire, Santa Fe
County Fire EMS, Artesia Fire, Carlsbad Fire the Department of
Energy’s Waste Isolation Pilot Plant and the Mescalero Apache
Tribe Fire EMS. He serves as the associate medical director and
crew member for MedFlight based out of Albuquerque and is
also medical director and paramedic for TriState CareFlight in
New Mexico. He can be reached at email@example.com.