Chapter 6 - Respiratory Flashcards
List some of the respiratory tracts protective mechanisms
- Coughing
- Retching gag
- Laryngospasm
- Sneezing
- Excessive mucous secretion
- Mucociliary apparatus
- Bronchoconstriction
- Macrophages
Mucociliary Apparatus
Apparatus that moves mucus and trapped materials up the bronchi and trachea via sheets of sticky mucus that trap particles, it is then swept upward by microscopic, hairlike cilia that line the respiratory tract so the mucus and trapped materials are coughed up and expelled
Bronchoconstriction
Ring of smooth muscle that surrounds the small terminal bronchioles and can narrow or close off the airway, preventing foreign materials from entering and damaging the alveoli
Cor Pulmonale
When protective mechanisms become overstimulated or act when they are nor needed for protection they are now contributing the the signs of clinical disease itself, causing changes in the lungs and leading to heart problem
Antitussive Drugs
Block the cough reflex coordinated through the cough center
Tachypnea
Rapid breathing
Productive Cough
Produces mucus
Nonproductive Cough
Dry and hacking with no significant mucus brought up
Insipissated
Dry
(True/False)
Antitussives are indicated for use in very productive coughs
FALSE.
Antitussives are contraindicated with a productive cough. In such cases the body may be relying on the cough itself to prevent obstruction of the airways or accumulation of excessive mucus/debris
Centrally Acting Antitussives
Reduces coughing by suppressing the cough center neurons in the brainstem
List 1-2 centrally acting antitussives
- Hydrocodone
- Codeine
Locally Acting Antitussives
Reduces coughing by directly soothing the irritated respiratory mucosa that is initiating the cough (cough lozenge)
(True/False)
Locally acting antitussives are not used in Veterinary medicine
TRUE.
Animal patients are unwilling to hold lozenges in their moth long enough to be effective
What are antitussives commonly used to treat in veterinary medicine?
Dry, nonproductive coughs generated by inflammation in the trachea or bronchi (or both)
Butorphanol (Torbutrol)
- Centrally acting opioid cough suppressant (IV best route of admin - oral dose 10x higher)
- Only FDA approved cough suppressant for Veterinary use
- Class IV controlled substance
Hydrocodone (Hycodan)
- Orally administered potent Mu opioid receptor agonist antitussive that is synthesized from codeine but is much more potent.
- Human drug - all Veterinary use is extra-label
- Class II controlled substance
Codeine
- Relatively weak Mu-opioid receptor agonist antitussive
- Found in a variety of oral cough and cold preparations (acetaminophen often included in these)
- Not typically used in the dog because it is not well absorbed
- Contraindicated for use in cats
Dextromethorphan
- Antitussive
- Considered a non-narcotic because it does not combine with opioid receptors to produce its effects
- Common in OTC preparations
- Caution should be used since they often contain acetaminophen
- Not recommended for use to control coughing in dogs/cats
Mucolytic Agents
Designed to break up or lyse mucus and reduce its viscosity so the cilia can more readily move it out of the respiratory tract
Reverse Sneezing
Can be caused by any irritation in the nasal cavity (allergic response, inhaled antigens, nasal polyps, tumors)
Acetylcysteine (Mucomyst)
- Mucolytic Agent - Decreases viscosity of mucus by breaking apart the disulfide bonds contributed to the mucus by DNA strands and that contribute significantly to the viscosity of the mucus
- Also used PO or IV as the antidote for acetaminophen toxicosis
Nebulization (aerosolization/aerosol therapy)
Inhalation of a fine mist containing the drug
(True/False)
Oxygen administered to animals with respiratory problems, is very dry in nature, and can dehydrate the mucociliary apparatus and decrease its efficiency
TRUE.
Oxygen is very dry and reduces the mucociliary apparatus’s function. Moisture should be added for animals on long term oxygen therapy
Expectorants
Improve the effectiveness of the mucociliary apparatus by increasing the fluidity of mucus in the respiratory tract by generating watery secretions by respiratory tract cells
Expectorate
To spit
Guaifensin (Glyceryl Guaiacolate) “GG”
Expectorant - Slightly irritates the gastric mucosa, stimulating the PSNS to create respiratory secretions
- Also used IV in horse anesthesia protocols to provide muscle relaxation
Saline Expectorants (Ammonium Chloride, Potassium Iodide and Sodium Citrate)
Expectorants that slightly irritate the gastric mucosa, stimulating PSNS to create respiratory secretions
Volatile Oil
Terpin Hydrate, Eucalyptus Oil and Pine Oil
Expectorants that directly stimulate watery respiratory secretions when their vapors are inhaled or when the absorbed volatile oil is excreted by the respiratory tract
Decongestants
Reduce congestion (vascular engorgement) of swollen nasal tissues by stimulating the SNS’s Alpha 1 receptors on the smooth muscle of blood vessels in the skin and mucous membranes
Why should animals with cardiovascular disease not be treated with decongestants?
Decongestants are not specific of A1 (alpha) receptors, most have some B1 (beta) receptor activity and increase the HR as a side effect. For an animal with cardiovascular disease, the additional O2 demand by the stimulated B1 myocardial cells could result in arrhythmia
What decongestant is closely similar to Methamphetamine in its chemical structure?
Pseudoephedrine
This decongestant is not regulated like Pseudoephedrine and it is also less effective
Phenylephrine
(True/False)
Decongestants are very commonly used in Veterinary medicine
FALSE.
They are very rarely used, but owners should be informed of the risks if they administer their own OTC medications to their pets at home
Bronchoconstriction
Contraction of smooth muscles surrounding the small terminal bronchioles deep within the respiratory tree
Dyspnea
Difficult breathing
Acetylcholinesterase
Enzyme that normally breaks down acetylcholine and terminates its activity
List 2-4 inflammatory mediators released by inflammatory cells that cause bronchoconstriction and airway inflammation
- Serotonin
- Histamine
- Prostaglandins
- Leukotrienes
PSNS effect on bronchcoconstriction (slightly more dominant than SNS)
Release of acetylcholine and stimulation of the bronchiolar smooth muscle muscarinic receptors creates a constant, slight degree of bronchoconstriction
SNS effect on bronchoconstriction
Antagonizes the PSNS primary effect by causing bronchodilation via norepinephrine stimulation of B2 receptors
Beta-Adrenergic Agonist Bronchodilators
More selective B2 agonists (than older generation epinephrine) and have fewer (but still some) B1 side effects (increase HR and force of contraction). These drugs last longer
MDI’s
Metered-Dose Inhalers “rescue inhalers” usually contain drugs like Terbutaline or Albuterol
RAO
Recurrent airway obstruction - asthma syndrome in horses
Albuterol/Terbutaline
Used to treat bronchoconstriction, asthma like syndromes in small animals and RAO in horses
Epinephrine
Older B2 agonist bronchodilator - non-selective meaning they stimulated B1 + B2 receptors, increasing the HR and force of contraction. Still used for emergency treatment of life-threatening bronchoconstriction
Methylxanthine Bronchodilators
There are two mechanisms that are reported
1) Phosphodiesterase inhibition mechanism - B2 stimulated by B agonists and the cell produces cAMP, causing relaxation of the bronchiolar smooth muscle
2) Blocking of adenosine receptors or direct interference with the calcium mobilization required for the contractile elements of the muscle to connect, forcing bronchiolar smooth muscles to remain in a relaxed state
Aminophylline
Methylxanthine bronchodilator - 80% theophylline and 20% ethylenediamine salt to make the drug better tolerated by the GI tract when given orally. Very interactive with other drugs
Theophylline
Methylxanthine bronchodilator of choice due to refinements in sustained release formulations which are capable of establishing longer therapeutic concentrations in dogs
Very interactive with other drugs
Antimicrobials
Drugs used to combat infections by a variety of microorganisms including bacteria, fungi, and protozoa
Corticosteroids
Indicated in situations in which the inflammation itself is potentially more life threatening than a temporary suppression of the immune response - Large doses are known to impair the immune response to infection and have the potential to delay healing
(True/False)
Corticosteroids are used frequently to treat feline asthma syndrome
TRUE.
Cats with feline asthma syndrome appear to respond well to corticosteroid treatment
Antihistamines
Antihistamines block the H1 receptors - but this alone does little to alleviate clinical signs of respiratory disease
Diuretics
Used to remove accumulated fluid from the lungs by promoting loss of body water through decreased reabsorption of water by the kidneys. Think of it as therapeutic tissue dehydration.
Oxygen
Indicated in animals that are transiently hypoxic
Hypoxia
An absence of enough oxygen in the tissues to sustain bodily functions
(True/False)
Using diuretics to remove accumulated fluid edema does not dry the respiratory secretions or affect the mucociliary apparatus
FALSE.
Diuretics promote water loss through the kidneys, which tend to dry the respiratory secretions, rendering the mucociliary apparatus less effective
