Chapter 13: Pharmacology, Anatomy, and Physiology Flashcards
Respiration is driven automatically by the ________
Brainstem (Medulla Oblongata)
Respiration controlled voluntarily by the _______
Cerebral Cortex
Anatomy of Upper Airway
Nose, Pharynx, Nasopharynx, Oropharynx, Laryngopharynx
Anatomy of Lower Airway
Larynx, Trachea, Bronchi, Bronchioles, Respiratory Zone
What does the nose do? What is its function with inhalation sedation?
Warms air
Humidifies air
Filters particulate matter
Primary entrance of gases used in inhalation sedation
It is critical that the patient can breathe well (enlarged tonsils, deviated septum, seasonal allergies)
Pharynx
Cylindrical tube of muscles 3 sections -Nasopharynx -Oropharynx -Laryngopharynx
Nasopharynx
Behind nasal cavity
Contains adenoids, tonsils, Eustachian tubes
Oropharynx
Bordered superiorly by soft palate and inferiorly by the epiglottis
Opens into the mouth
Larygnopharynx
Epiglottis
Cricoid cartilage
Larynx
Vocal cords
Glottal opening is the narrowest part of the adult airway
Cricoid ring is narrowest part of the pediatric airway (younger 7-10y)
Cough is a protective reflex that stays intact when using N2O.
What is the narrowest part of the pediatric airway (7-10 years and younger)
Cricoid ring
What is the narrowest part of the adult airway?
Glottal opening
What makes up the respiratory zone?
Alveolar duct, sac and alveoli
Trachea
part of the lower airway; bifurcates asymmetrically at carina
Bronchi
- R bronchus…2.5cm long and deviates 25 degrees
- L bronchus…5cm long and deviates 45 degrees
- L bronchus is smaller and deviates more
- Aspirated objects usually in R bronchus
Bronchioles
Conducting; cannot exchange gases
Physiology of the respiratory mechanism
Medullary center in brainstem controls the automatic respiratory process of breathing
What controls the automatic respiratory process of breathing?
medullary center in the brainstem
Muscles of the respiratory mechanism
Diaphragm
Intercostals
Scalenes
Sternocleidomastoids
Respiratory distress vs. failure
abnormal breathing vs. clinical state of inadequate oxygenation, ventilation or both
What happens during inspiration?
Diaphragm contracts and creates a negative pressure and air moves in…this continues until lung pressure equals atmospheric pressure
What happens during expiration?
Diaphragm relaxes and chest wall recoils
What is tidal volume?
Amount of gas inspired into lungs…usually about 500ml
What is minute ventilation?
Tidal volume x RR…usually about 6-7l/min
What is anatomic dead space?
Portion of inspired air that occupies the conducting airway and does not participate in the exchange of gases
What is air made up of?
79% N2
21% O2
0.04% CO2
-gases move from high to low pressure
N2O movement
N2O/O2 is administered, high concentrations of these gases is found in the alveoli, the capillary having no N2O is quickly filled. When the N2O is terminated capillary concentrations are higher than alveolar and N2O rapidly moves into the alveoli and is exhaled
Pulse oximetry
O2 saturation of arterial blood, oxyhemoglobin concentration
Usually 98-100%
Usually measures HR as well
Pulse Ox measurement below 90% is significant
Is pulse ox required for minimal sedation?
Not required for minimal sedation, it is required for moderate sedation
Diffusion hypoxia
Results from N2O leaving lungs at a high rate (faster than that of replacement by N2)…diluting the O2
Headache, lethargy, nausea
Prevented by 100% O2 for 5 min and should always be used
Some researchers claim diffusion hypoxia is insignificant
Management of patients experiencing moderate sedation (greater than 50% N2O)
Practitioner is responsible for complications in intended level and deeper level
Obstruction of upper airway
Fasting guidelines
What could obstruct the upper airway?
Tongue
Foreign body
What should remain intact during moderate sedation?
Laryngeal and pharyngeal reflexes should remain intact
Cough
Gag
Obstruction of upper airway caused by foreign body (choking)
-Universal distress sign
-Are you choking?
-Heimlich maneuver
-If patient becomes unconscious
(Medical emergency)
-CAB’s
-Chest compressions
Obstruction due to tongue
Tongue
Head tilt – chin lift should open airway not caused by foreign body
Partial airway obstruction – snoring – risk factor
Complete airway obstruction – no sounds or exchange of air
should you use a pulse oximeter during moderate sedation?
yes - use a pulse ox during moderate sedation
What do you do if someone is vomiting during moderate sedation?
Discontinue N2O
Turn head to side
Suction, NOT THE SALIVA EJECTOR
Nedley’s notes: You could vomit and have that go down into the lungs – silent regurgitation
If it’s gastric fluid, that’s less harmful than a breakfast burrito
What are the fasting guidelines for moderate sedation?
Fasting guidelins Ingested material Minimum fasting period Clear liquid 2 hours Nonhuman milk 6 hours Light meals 6 hours
How does N2O interact with the cardiovascular system?
N2O does not negatively affect the cardiovascular system to produce any significant physiologic changes
N2O has positive effects on myocardial ischemia
N2O may decrease blood pressure but is dose related…usually not affected at concentrations used in the ambulatory care setting
How does N2O interact with the CNS?
Depresses the CNS…mechanism is unknown
Chronic exposure results in peripheral neuropathy, weakness, ataxic gait
How does N2O interact with the respiratory system?
URTI…inadequate sedation
- Expansive, increases pressure in patients with sinusitis
- Silent regurgitation and aspiration…want to maintain protective reflexes…don’t allow patients to go unconscious vs sleep in pediatric patients, many times patients haven’t fasted
- Titrate the N2O
- No reported allergies to N2O
- Contraindicated in patients on hypoxic drive
- -COPD
- -Emphysema
- -Usually very ill…ASA III or IV
Relative contraindications for the use of N2O/O2 sedation
First trimester of pregnancy Current URTI COPD’s Psychologic impairment Current or recovering drug addiction Middle ear disturbances
recommendations regarding N2O/O2 sedation
Emphysema, MD consult for hypoxic drive COPD’s, MD consult for hypoxic drive Tuberculosis, sterilize HIV, sterilize URTI, postpone Pneumothorax postpone Cystic fibrosis postpone?...No active infection
Hematopoetic system
Affects bone marrow after increased concentrations for extended periods may interfere with vit B12 dependent methionine synthase involved in DNA synthesis and erythrocyte production Ok for Anemias Methemoblobinemia SCA Leukemia Hemophilia Polycythemia vera
What is the interaction like between N2O and the endocrine system? What is the endocrine system?
No negative effects
the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things
Effects of N2O on the hepatic system?
no negative effects
Effects of N2O on the gastrointestional system?
N2O is expansive and is contraindicated in patients with a bowel obstruction
Ask about kid on stool softeners
Effects of N2O on the genitourinary system
Not during 1st trimester of pregnancy
MD consult for 2nd and 3rd trimesters of pregnancy
Leave decision to use or not use N2O to patient and medical personnel
Ok with kidney disease
Effects of N2O on the neuromuscular system
Ok to use with Multiple Sclerosis Muscular Dystrophy Cerebral Palsy Myasthenia Gravis
What are the concerns with N2O on ear and eye?
Ear Middle ear conditions Recent ear infections Eye Recent surgery…gas bubble in patients that were expose to perfluorpropane or hexafluoride gas could expand and complicate healing
What kind of effect does N2O have with sedative medications?
synergistic effect
What is the interaction with N2O and bleomycin sulfate?
bleomycin sulfate is a cancer medication that increases the incidence of pulmonary fibrosis
Benefits of using N2O with pediatric patients?
- Nasal hood restricts the field of vision
- Use O2 only in patients that won’t give consent
- Sometimes patients aren’t breathing nasally
- Helps with head position
What do you want to ask parents and patients about prior to sedation?
- Abnormalities of major organ systems
- Previous adverse events with sedation or analgesia
- Drug allergies, current medications
- Time and nature of last oral intake
- History of tobacco, alcohol, or substance abuse
ASA I
- Normal healthy patient
- Patient with no systemic disease
- Candidate for N2O/O2 sedation
ASA II
- Patient with mild systemic disease
- Mild to moderate physiologic disturbance that is under good control
- No compromise of normal activity
- Candidate for N2O/O2 sedation
ASA III
- Patient with severe systemic disease
- Patients with major systemic disturbances that are difficult to control
- Creates a major impact on surgery or anesthesia
- Candidate for N2O/O2 sedation following medical consultation
ASA IV
- Patient with severe systemic disease that is a constant threat to life
- Patients with severe and potentially life threatening systemic disease
- Significantly limits their activity
- Medical emergencies are likely
- N2O/O2 sedation is usually not indicated
ASA V
- Moribund patient that is not expected to live without an operation
- Moribund patient in whom surgery is last effort to save their life
ASA VI
- Declared brain-dead patient whose organs are being removed for donor purposes
- Clinically dead but being maintained for organ donation
ASA E
- Patient requires emergency procedure
- Designation for a patient in any ASA classification requiring an emergency procedure
Pre-procedural patient evaluation
Vital signs Height Weight Body temperature Blood pressure (BP) Pulse (HR) Respiration (RR)
What’s measured preoperatively, intraoperatively, and postoperatively?
BP, HR, RR usually measured preoperatively, intraoperatively, and postoperatively
What do you use to evaluate the airway?
Precordial-pretracheal stethoscope
Why is a pre-procedure evaluation of the airway necessary?
Pre-procedure evaluation of the airway
Uncovers abnormalities that could increase the likelihood of airway obstruction
Positive pressure O2 may be necessary if respiratory compromise occurs during sedation
What may be necessary if respiratory compromise occurs during sedation?
Positive Pressure O2
What needs to be done prior to a pre-sedation appointment?
History & Physical exam
What are doctors looking for during a history?
Previous problems with anesthesia or sedation?
Stridor, snoring, or sleep apnea?
Advanced rheumatoid arthritis?
Chromosomal abnormalities?
What are you looking at during a physical exam?
Habits, Head and Neck, Mouth, Jaw
Concern with habits for sedation?
obesity - are they overweight?
What kinds of things are you looking for during a head and neck exam?
Short neck Limited neck extension Mass Trauma Tracheal deviation Dysmorphic facial features
What kinds of things are you looking for when examining the mouth?
Limited opening
Macroglossia
Tonsillar hypertrophy
Nonvisible uvula
What are you looking for when examining the jaw?
Micrognathic
Retrognathic
Trismus
What does the ASA task force recommend to monitor during sedation?
Level of consciousness
Pulmonary ventilation
Oxygenation
Hemodynamics
How can you determine a patient’s level of consciousness?
Monitored by the patients response to verbal commands
How do you monitor pulmonary ventilation?
1) Observation: observe chest rise and fall and check the reservoir bag
2) Auscultation: Pre-trachael stethoscope
How do you monitor oxygenation?
with a pulse oximeter
How often should intraoperative documentation of monitoring vital signs during moderate sedation be done?
Intraoperative documentation monitoring of vital signs for moderate sedation is recommended every 5 min
How can you be prepared for emergencies?
- BLS certified including management of airway obstruction
- AED
Additional equipment needed during emergencies (5 things)
- Antagonist medications
- Positive pressure ventilation system
- Adequate suction…not a saliva ejector
- Advanced airway equipment
- Resuscitation equipment
Titration of N2O/O2 gases
Titration is a method of drug administration in which definitive amounts of the substance are given in incremental doses until a specific endpoint is reached; its the current standard of care
Using “fixed dose” or rapid induction?
Large concentrations of N2O initially, up to 50% used especially in children is not recommended except under specific conditions administered by a trained pediatric dentist
Advantages of using N2O
- Only amount of drug required by the patient is given
- Allows for biovariability
- Uncovers idiosyncratic reactions early
- Minimizes negative experiences with oversedation
What are the benefits to adjusting N2O levels? When should you increase and decrease levels?
- Great advantage is the ability to adjust the levels of sedation
- Increase level when more painful approaches
- Decrease level when procedure nears completion
- Previous sedation levels are not important?…Biovariability
- Negative experiences are usually due to oversedation…medication is blamed rather than operator error
What are the signs and symptoms of appropriate minimal sedation?
Patient is comfortable and relaxed
Patient acknowledges reduced fear and anxiety
Patient is aware of surroundings
Patient responds to directions and conversation
Protective cough and gag reflexes remain intact
Eyes become less active and glazed look appears
Patient may experience…tingling in extremities, heaviness, warmth, light feeling, vasodilation of face and neck
Why should you limit talking?
Limit talking to receive the drug’s effects
Questions should focus on how patient is feeling as opposed to what they are feeling
- Biovariability suggests that some patients will have tingling and others will not
- If patient doesn’t feel what you told them they should they may believe that the drug is not having an effect
What happens during oversedation?
Signs of oversedation may not always be obvious
Operator should always be present to monitor the patient
Instruct patient to inform operator if they feel uncomfortable (hard in kids)
Engage the patient verbally periodically to assess response…need constant chatter with kids
Nedley’s Notes:
“what’d you have for breakfast?”
“how does your stomach feel?”
Keep at 50% … can be above for injection… he stays routinely above it because that’s just what the flowmeter says 60%
Tell a story and distract when injecting so they can’t respond
Signs and Symptoms of Oversedation
Detachment/dissociation from environment
Dreaming, hallucination, or fantasizing
Floating and/or flying
Inability to move, communicate or keep mouth open
Humming or vibrating sounds that progressively worsen
Patient may experience…drowsiness, dizziness, nausea, lightheadedness, fixed eyes, uncomfortable warmth
Patient may progress to…sluggish, delayed responses, slurred words or no verbal response, agitated or combative behavior, vomiting (especially in children), unconsciousness
Nedley’s Notes:
Silent regurgitation - Prevent with patient being NPO, add monitor to listen for signs of vomitus coming up,
If you just turn off the nitrous they’ll wake up and you can’t finish the procedure… just turn it down
Why is N2O/O2 called laughing gas?
uncontrolled laughter
2 Keys to successful administration of N2O/O2?
- Titration of the drug
- Careful monitoring (observe and evaluate)
Fundamental principles for appropriate administration
Informed consent
Bio-variability, do not adopt a fixed dose philosophy
100% O2 at beginning and end
Do not leave patient unattended
NPO status…will not prevent vomiting but could decrease the chance of aspiration
Pre-operative Unit Preparation
Equipment
Flowmeters
Scavenging masks
Vacuum system
