Introduction Flashcards
Anesthesia is
Loss of feeling or sensation (including pain)
Partial or complete
Drug induced; intentional
Used to perform surgery or other painful procedures
Reversible
Local, regional or general
Local anesthesia
Loss of feeling or sensation to a specific area due to local desensitisation of a peripheral nerve bed
Freezing, line blocks
Regional anesthesia
Loss of feeling or sensation to a large portion of the body (such as a limb, lower half of the body, abdomen)
Due to desensitisation of spinal nerves and/or peripheral nerve bundles
Spinal block, epidural
General anesthesia
Anesthesia due to depression of the CNS
Comal-like state; affects the entire body
Patient neither perceives nor recalls noxious stimuli
Increased risk of adverse effects
Tranquilization means
Reduces anxiety and produces sense of tranquillity
Anti-anxiety, calm and chillout
Reduces the ability respond to a stimulus
There is no change in the ability to perceive pain
Sedation is
More profound that tranquilization and produces drowsiness and/or hypnosis
The sedatives reduce anxiety, reduce the ability to respond to stimulus
Sedatives also decrease sensation of pain
Animal is CONSCIOUS
3 levels
Light
Moderate
Heavy
Hypnosis, narcosis is
Greater degree of CNS depression
Degree of consciousness is noticeably affected; patient is entering unconscious state
Will learn that this overlaps with stage 1 and 2 of general anesthesia
Surgical anesthesia
Patient is unconscious
There is no perception of pain
Significant CNS depression
Analgesia
Relief of pain without loss of consciousness
Analgesic
A drug that relieves pain
Balanced anaesthesia (aka multimodal anesthesia/analgesia) is and includes
Using multiple drugs in combination
In smaller doses than if only using one drug on its own
To obtain appropriate CNS depression to perform a specific procedure
Includes
Premed
Induction agent
Maintenance anesthesia
Analgesia (pre- and intra- operative)
Benefits of balanced anesthesia
Limits adverse effects of each individual drug
Maximize the benefits of each drug
Accounts for motor, sensory (PAIN), reflex and mental aspects of the nervous system
The anesthetic protocol must take into account:
Patient
Procedure
Facilities available
NOTE: your anesthetic protocol is always changing between patients…. and sometimes for the same patient
What is the RVTs role in anesthesia
Preparation, operation and maintenance of anesthetic equipment
Administration of anaesthetic agents
Endotracheal intubation
Patient monitoring
Planning
Patient
Equipment and materials
Patient assessment
Premedication
Surgical fluids
Induction
Surgical prep
Maintenance anesthesia
Recovery (period when anesthetic drug is removed and vital return to normal, animal is conscious)
Postoperative analgesia
What does the RVT do to plan anesthesia
Patient
Estimates, required diagnostics, pre-surg medications
Organizing with owner (incl fasting requirements)
Consents
Equipment and materials
Drugs, anesthetic equipment, surgical equipment
Patient assessment
Weight, TPRs
Asses for pre-procedure mentation and pain
Any pre-anesthetic diagnostics (bloods,rads)
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What does the RVT do to patient assessment before anesthesia
Weight, TPRs
Asses for pre-procedure mentation and pain
Any pre-anesthetic diagnostics (bloods,rads)
What does the RVT do for premed
Calculating doses, administration medications
Assessing degree of sedation after administration
Responding to adverse reaction to sedation/premed
What does the RVT do for surgical fluids
Setting up surgical fluids
Catheter placement
Calculating fluid rates based on fluid plan
What does the RVT do for induction of anesthesia
Calculating and administering injectable anesthetic dose
Endotracheal; intubation
Assessing depth of anesthetic
Patient monitoring
What does the RVT do for maintaining anesthesia
Operating anesthetic machine
Oxygenation
Delivery of inhalant drugs
Ensuring fluids and thermosupport
Patient assessment
Assessing depth of anaesthesia
Assessing patient vitals
Monitoring and responding to drug effects; ability to rapidly respond in case of overdose/arrest
Differentiating pain from other stress
What does the RVT do for recovery of anesthesia
Patient monitoring and assessment
Extubation, assessing for pain/other physiological stress
Requesting appropriate analgesia/sedation if indicated
Providing non-pharmacological comfort and care
What does the RVT do for postoperative analgesia
Patient monitoring
Assessing for pain and comfort
Calculating and administering analgesics and ancillary support (i.e., PT, IV fluids, antibiotics, nutrition)
Fundamental challenges, inherent risks of anesthesia
Very narrow therapeutic index
Consequences of a calculation or administration error → may be serious
Vital signs and indicators and anaesthetic depth
MUST BE closely monitored
Accurate interpretation of visual, tactile, and auditory info from the patient, anaesthetic equipment, and monitoring devices
Comprehensive understanding of the significance of physical parameters (ex. HR,RR, reflexes) and machine generated data (ex. BP, O2 sat’n)
Potential for patient harm during administration of anaesthetic is relatively high
Competence and confidence are earned through
Study, practice,, persistence, caring attitude, dedication to excellence
What is essential to know for anesthesia
Pharmacology of common drugs
Desired effects
Expected SIDE EFFECTS
Unacceptable side effects
Pharmacy laws
Controlled drugs
Dose calculations
Normal patient physiology
What is not “normal” is automatically abnormal
Also know how “normals” change when under the influence of anaesthetic drugs
How to recognize and respond to adverse effects
Preanesthetic assessment should include
Patient history
Signalment
Current and past illness
Medications currently being administered
Allergies or drug reactions
Status of preventive care
Physical examination
Haematology/biochemistry
Anesthetic plan
The anesthetic protocol should incldude
Pre-anesthetic treatment
Premed
Induction
Maintenance
Analgesia
Blocks
Emergency drugs
Monitoring/special equipment
Recovery/post-procedure analgesia plan
Functions of the nervous system
Sensory
Integrating
Motor
Two types of nervous sytem
A central nervous system (CNS)
Brain and spinal cord
Peripheral nervous system (PNS)
Nerves that link the CNS with the rest of the body
Neuron
Basic functional unit of the nervous system. Composed of a cell body, dendrites, and an axon. Initiate nerve impulses, and also conduct them.
Neurotransmitters
Chemical released by the presynaptic neuron that diffuses across the synaptic cleft, binds with the receptor on the postsynaptic membrane, and stimulates or inhibits the postsynaptic neuron
Synapse
Junction between two neurons or between a neuron and target cell
Receptor
A specialized protein to which neurotransmitters bind
“lock and key”
Nerve impulse
Wave of cell membrane depolarization that travels from the point of stimulus down the length of a nerve cell process
Conducted along a nerve fibre by the “flipping” of electrical charges across the cell membrane (depolarization), followed quickly by “unflipping” of the electrical charges (repolarization)
Local anesthetics
Drugs injected to block the conduction of sensations
Ex. Lidocaine
Prevents sensory nerves from depolarizing despite stimulation
Epidural anesthesia
Anesthetic agents are injected into the space outside the spinal cord dura mater to produce large areas of local anaesthesia
Block depolarization waves through spinal nerves thus removing the perception of pain from the part of the body they supply
The body can more readily maintain normal autonomic function during this type of anaesthesia
Neurotransmitters classifications
Excitatory
Inhibitory
Both
Acetylcholine, Catecholamines (norepinephrine, epinephrine, dopamine), GABA (gamma-aminobutyric acid) and glycine
Excitatory neurotransmitters are
Have an excitatory effect on the postsynaptic membrane when combine with the receptor
Inhibitory neurotransmitters are
Tend to depress or decrease depolarization of other neurons or target tissues
Neurotransmitters and receptors of the somatic nervous system
Conscious or voluntary control of skeletal muscles
Sympathetic nervous system (SNS) does what
Fight or flight
Neurotransmitter: catecholamines; primarily norepinephrine but also epinephrine and dopamine
Adrenergic neurons
Adrenergic neurons in the SNS
Alpha 1: found on blood vessels, and cause vasoconstriction of the skin, GI tract and kidney
Beta1: increase HR and force of contraction
Beta2: bronchodilation
Parasympathetic nervous system (PNS) does what
Rest and restore
Neurotransmitter: acetylcholine
Cholinergic neurons
Nicotine
Muscarine
Anesthetic agent is
Any drug to induce a loss of sensation w/ or w/o unconsciousness
Adjunct is
Drug that is not a true anesthetic, but is used during anesthesia to produce other desired effects
Sedation, muscle relaxation, analgesia, reversal, neuromuscular blockade, or parasympathetic blockade
Classifications of anaesthetic agents
Route of administration
Time period of administration
Priciple effect
Chemistry
Classifications of anaesthetic agents by route of admin
Inhalant
Injectable
Oral
Classifications of anaesthetic agents by time period of admin
Preanesthetic medication
Induction agent
Maintenance agent
Classifications of anaesthetic agents by principle effect
Local anaesthetic
General anesthetic
Sedatives
Tranquilizers
Muscle relaxants
Neuromuscular blockers
Anticholinergic agents
Reversal agents
Drug classifications based on “chemistry”
Anticholinergics
sedatives/tranquilizers
Phenothiazines
Benzodiazepines
Alpha2- agonists
Opioids
Propofol
Etomidate
Alfaxalone
Barbiturates
Dissociatives
Guaifenesin
England anaesthetics
Angonist and antagosnist are
After administration, most drugs are distributed throughout the body by the blood. Each drug binds to specific receptors in one or more “target tissues”. After binding to specific receptors, the drug stimulates the receptor, causing one or more specific effects.
Agonists work by
Bind to and stimulate tissue receptors
Antagonists work by
Bind to, but do not stimulate receptors
Reversals
Competitively bind to receptors and displace the corresponding agonist, blocking further action
Partial agonists work by
Bind to and partially stimulate receptors
Agonist-antagonists work by
Bind to more than one receptor type and simultaneously stimulate one and block at least one
Drugs in anesthesia work by
Mimicking inhibitory neurotransmitters that turn down nerve function- Turning “on” the off signals
OR
Can bind to and block action of the naturally occurring neurotransmitters- Blocking the “on” signals
Agonists = Drugs that bind to nerves and turn ON
Drugs that have the same activity as naturally occurring neurotransmitters
Bind to and “TURN ON”; effect is to increase a naturally occurring response
Ex: diazepam which binds to and turns on the neurons that “turn down” the brain
Turning on the “OFF” switch
Antagonist = drug that block activity of normal neurotransmitters
Drugs that bind to and block the naturally occurring response at the nerve synapse
Decreases or prevents an action
Most commonly act by binding to receptors and blocking neurotransmitters from binding
Blocking the “On” switch
All of the drugs used in general anaesthesia are nerve depressants:
General anesthetics depress CNS function, especially the brain
Regional anesthetics are directed at peripheral nerve bundles and/or spinal segments
Local anaesthetics block peripheral nerves
Tranquilizers and sedatives depress CNS function to a lesser degree
CNS depressants are
Aka central-acting drugs
Tranquilizers, sedatives and general anesthetics
Act directly on the brain
Wide-ranging effects; usually also affect the ANS
Low therapeutic index
All the the ability to cause death
Tranquilization→ sedation→ narcosis/hypnosis→ loss of consciousness→ brain stem shut-down → death
Effect of anesthesia on the autonomic nervous system
Drugs also influence the ANS
May be a directed side-effect of the drug
Part of turning on the parasympathetic response (rest and digest)
Especially sedatives and tranquillisers
Effects of turning up the PS response are
Decreased RR, bronchoconstriction
Peripheral vasodilation
Decreed HR and stroke volume
Increased bronchial and GI secretions
Miosis
Effects of turning up the SN response are
Increase HR
Increase RR
Dilate of bronchioles; increase air blow
Pupils dilate, mydriasis
Decreased Gi motily and blood flow to skin
Increased blood to muscle
Decreased diameter of kidney blood vessels
