NMDA Journal Spring 2016

vagal afferent nerves (CN X) which are more sensitive to

mechanical, chemical, and thermal stimulation. In the

oral cavity, pharynx, and larynx, it is the area of distri-

bution of the glossopharyngeal (CN IX) and trigeminal

(CN V) nerves that lend sensory and motor support the

Cough Reflex action. Stretch receptors in the conducting

airways and lungs can enhance or reduce the magnitude

of the coughing event. The protective purpose of the

Cough Reflex is to halt and reverse the inhalation of

aerosol, particulate, or gaseous irritants when the tracheal,

laryngeal, or bronchial mucosa is stimulated.

Interesting

to note about the Cough Reflex is that it can be initiated

by both external stimulation, invasion of noxious stimuli,

or by internal stimulation, mucous secretions moving up

the bronchial tract via ciliary movements and bronchial

muscle contractions. When a large enough bolus of secre-

tions have made its way high enough up the larynx, the

cough reflex is initiated to begin the secretion expulsion

process.

The Cough Reflex can be restrictive to dental

treatments, especially in long-term smokers, where secre-

tion clearance can be problematic. Persistent coughing

during dental procedures not only adds precious time to

a dental appointment, but can release aerosolized bacterial

colonies from the lower airways and increases the chances

of material loss down an open airway.

Management of the Cough Ref lex during dentistry

depends on the reason for the cough. Common stimulates

for coughing can be respiratory illness, chronic inhalation

of irritants or use of angiotensin-converting enzyme (ACE)

inhibitors taken for hypertension, or periodic aggravation

from transient irritants. If this reflex is being disruptive

due to illness, the solution is as simple as discontinuing

the appointment and allowing the patient time to recover.

If the disruptive coughing is due to a patient’s chronic

use of inhaled tobacco, marijuana, or ACE inhibitors,

or periodic, transient aggravation, the management may

include increased vigilance during suctioning, vigilance of

the dental surgeon to decrease surgical debris, and occa-

sionally stopping during the procedure to allow a patient

to clear debris collected in the airway. Sedation in the case

of a chronic cougher usually will not abolish the reflex

and may in fact complicate airway management due to the

fact that sedation may weaken the patient’s ability to effec-

tively clear the airway and lead to laryngospasm. General

anesthesia with intubation in a patient with a troublesome

cough can lead to bronchospasm and in most cases can

be a relative contraindication in the outpatient setting.

# 3 Bronchospastic Reflex

The Bronchospastic Reflex, sometimes called Reflex Bron-

choconstriction, but commonly referred to as an asthma

attack, is related to the Cough Reflex in that it can be a

progression from failure of the Cough Reflex to adequately

expel inspired harmful irritants. Like the Cough Reflex,

the Bronchospastic Reflex starts with mucosal stimulation

in the larynx, trachea, and bronchioles. Unlike the Cough

Reflex, which causes airway hyper-expansion in prepara-

tion for a violent exhalation force and mucous is used as

a carrier mechanism to further expel unwanted materials,

the Bronchospastic Reflex causes airway constriction and

increased mucous production as a protective coating to

decrease the severity of airway insult to the pulmonary

tissues. The purpose of the bronchospasm is a sort of

“hunker down” mentality of the pulmonary tissues to

protect them as they can ride out the irritant storm. A

bronchospasm in response to anesthesia equipment irri-

tation is essentially an asthma attack, so avoiding dental

work during acute exacerbation events, pre-treatment with

albuterol, beta 2-agonist therapy, and corticosteroids will

abate the reflex. In an study by Harald, et. al., lidocaine

significantly reduced bronchoconstriction of respiratory

smooth muscle cells and caused reflex suppression most

notably with inhalation administration via nebulizer.

Inhalation administration also yielded a much higher,

longer-lasting concentration of active drug in the airway

tissues and negligible increases in blood plasma lidocaine

levels, therefore decreasing the possibility of subsequent

cardiac arrhythmias. Lidocaine also blocks the vagus

pathway (CN X), this along with direct relaxation of the

smooth muscle makes nebulized lidocaine an effective

mechanism to stop the Bronchospastic Reflex.

Management of the Bronchospastic Reflex almost always

involves rescue medications and starts at the pre-operative

or screening appointment. A good history and physical

should inform the operating dentist that the patient may

have a medical condition prone to bronchospasm, such

as, asthma. As an attack begins, the dental surgeon must

first stop the procedure, clear the mouth of all dental

materials, and prepare to administer a bronchodilator

either via inhaler or nebulizing mask. For severe bron-

chospasms, subcutaneous, intramuscular, or intravenous

epinephrine may be needed. Proper training is needed

for the doctor in these situations to insure proper dosing.

Corticosteroids and histamine blockers may also be given,

but are not first-line rescue drugs for a patient facing life-

threatening pulmonary constriction.

nmdental.org

continues

