Surgery test 2

Agonists

• A drug that binds to a receptor and activates it, mimicking the action of the body’s own signaling chemical.

• Binds to and stimulates target tissue.

• Most anesthetic agents and adjuncts

Analgesic

is a medication used to relieve pain by inhibiting pain pathways.

antagonists

• A drug that binds to a receptor and blocks or reverses another drug’s effects

• Competitively binds to the target tissue but doesn’t stimulate

  • Example: naloxone, atipamezole, flumazenil

Anesthetic

Used to induce a loss of sensation with or without unconsciousness

Antiemetic

A type of medication used to prevent or treat nausea and vomiting, often administered during or after surgery.

Neuroleptanalgesia

• A profound state of sedation and analgesia induced by simultaneous administration of an opioid and a tranquilizer or sedative

• Sedation used for minor procedures

• Used for the Induction of general anesthesia in dogs, but not used in cats or in young, healthy dogs

Pharmacodynamics

The study of how drugs affect the body, including mechanisms of action, therapeutic effects, and side effects.

Pharmacokinetics

• The path the drug takes through the body.

• Drug movement

Sedation

Suppression of brain activity and awareness to prevent movement; animals are usually unaware of their surroundings and are drowsy

Tranquilization

Decreases anxiety without causing excessive sedation or drowsiness, animals are usually aware of their surroundings but do not appear to care

Partial agonists

• Are opioids only

• Partially stimulates opioid receptors

  • example: Buprenorphine

Agonist-Antagonists

• Binds to more than one receptor, simultaneously stimulates one and blocks another.

  • Example: Butorphanol

Analgesia

• Creates the absence of pain

• Just because an animal is under anesthesia does not mean the perception of pain is eliminated

• The most general anesthetics are not analgesics

• Must provide analgesic per-,intra, and postoperatively

Inhalation anesthetics

Isoflurane, sevoflurane, and desflurane ( halogenated compounds) are used for inducing and maintaining anesthesia during surgical procedures.

Halogenated organic compounds

• Isoflurane and sevoflurane are the most commonly used agents in this class

• They are liquid at room temperature and become vaporized in oxygen that flows through the vaporizer

What are the effects of Halogenated organic compounds?

• CNS effects

  • Has dose-related reversible CNS depression

  • Can cause hypothermia

• Cardiovascular system effects

  • Depresses cardiovascular function

  • causes vasodilation

• Respiratory system effects

  • has a dose-dependent ventilation depression

What is the mode of action for Halogenated organic compounds

1. The liquid anesthetic is vaporized and mixed with oxygen gas

2. The mixture is delivered to the patient via a mask or endotracheal tube

3. The mixture travels to the lungs (alveoli) and diffuses into the bloodstream

4. Diffusion rate is dependent on concentration gradient ( alveoli/ capillary and lipid solubility)

5. The anesthetic delivery to tissues ( brain) is dependent on the blood supply

What are the important properties of inhalational anesthetics?

• The vapor pressure

• partition coefficient

• Minimum alveolar concentration ( MAC)

Isoflurane MAC%, Blood gas partition coefficient, and Vapor pressure STP

• MAC %: 1.3-1.63%

• Blood-Gas partition Coefficient: 1.46.

• Vapor pressure STP: 240

  • This indicates that Isoflurane has a minimum alveolar concentration of 1.3-1.63%, meaning it is effective at that concentration for 50% of patients to not respond to surgical stimuli. The blood-gas partition coefficient of 1.46 suggests it requires moderate time to achieve equilibrium in the bloodstream.

Sevoflurane MAC% , Blood gas partition coefficient, and Vapor pressure STP:

• MAC %: 2.34-2.58%

• Blood gas partition: 0.68

• Vapor pressure STP: 160

  • This indicates that Sevoflurane has a minimum alveolar concentration of 2.34-2.58%, meaning it is effective at that concentration for 50% of patients to not respond to surgical stimuli. The blood-gas partition coefficient of 0.68 suggests it achieves equilibrium in the bloodstream relatively quickly.

Vapor pressure

• In a closed container, a liquid will reach equilibrium with its gaseous form. The pressure exerted by the gas is the vapor pressure.

• It determines how readily an inhalation anesthetic will evaporate in the anesthetic machine vaporizer

• It is temperature- and anesthetic-agent dependent

Vapor pressure determines vaporizer types

• High vapor pressure Agents are volatile agents that are delivered from a precision vaporizer to control the delivery concentration

• All precision vaporizers are made to deliver only one specific agent

  • Isoflurane, sevoflurane, desflurane, and halothane

Low vapor pressure

• Nonvolatile agents are not used in vet med

• Delivered from a non-precision vaporizer

blood-gas partition coefficient

• The measure of the solubility of an inhalation anesthetic in blood as compared to alveolar gas

• indicates the speed of induction and recovery for an inhalation anesthetic agent

A low blood-gas partition coefficient

• agent is less soluble in blood than alveolar gas

• faster expected induction and recovery

What does the blood-gas Partition coefficient determines?

• It determines the clinical use of the anesthetic agent

• Questions to ask when using an anesthetic agent

  • Maintenance: how fast will the anesthetic depth change in response to changes in the vaporizer setting

  • Recovery: how long will the patient will sleep after anesthesia and how quickly the patient will recover from anesthesia.

How long does it take to see a change in a patient when using Isoflurane

it can take 10 minutes to see a change in a patient when using ISO

How long does it take to see a change in the patient when using Sevoflurane

• Sevo takes much less time than ISO to see a change in a patient

• A sevo patient wakes up faster

The lower the MAC the more BLANK the has is?

potent the anesthetic

Minimum Alveolar concentration (MAC)

• The potency of the drug

• The minimum inhalant concentration required to keep 50% of patients under anesthesia with the inhalant alone

• The lower the MAC of an anesthetic is, the more potent the anesthetic agent, and the lower the vaporizer setting

What can MAC be altered by

It can be altered by age, metabolic activity, body temperature, disease, pregnancy, obesity, and other agents present

is MAC lower in dogs than in cats

yes it is lower in dogs than cats

Isoflurane MAC

1.3% to 1.63%

Why is Sevo faster than ISO

it has a lower blood-gas partition coefficient, meaning it dissolves less in the blood and moves more rapidly into and out of the brain

What are some adjuncts that lower the MAC

• Acepromazine

• Dexmedetomidine

• ketamine

• opioids

• lidocaine

• Gabapentin

• trazodone

Injectable anesthetics

• Can produce unconsciousness

• Don’t provide analgesia

• must be used with other agents to produce the complete effects of general anesthesia

• Administered to effect IV

  • These are: propofol, etomidate, alfaxalone, and barbiturates

Propofol

• an ultra-short-acting, nonbarbiturate anesthetic

• commonly used to induce anesthesia in small animals

• Other uses: IV bolus and CRI to treat status epilepticus in dogs and cats

Properties of Propofol

• It is a highly fat-soluble drug

• Its potency increases in animals with low plasma protein levels

  • Onset of action: 30- 60 seconds

  • Duration of action: 5- 10 minutes

  • complete recovery: 20 -30 minutes

• When pushing propofol, wait 30- 60 seconds to prevent overdose in the patient

Propofol effects on the Central Nervous system

• Has dose-dependent depression from sedation to general anesthesia

• Transient excitement and muscle tremors (induction)

• paddling, muscle twitching, nystagmus, opisthotonos

  • nystagmus: rapid involuntary eye movement

  • opisthotonos: a severe, involuntary spasm where an animal's head, neck, and back are rigidly arched backward

Propofol effects on the Cardiovascular system

Causes cardiac depression and transient hypotension

Propofol effects on the respiratory system

depressant with possible apnea

The use of propofol

• Titrate IV slowly over 1-2 minutes to effect

• IM produces mild sedation and ataxia only ( hurts when given IM)

• Dose depends on premedication’s

• It is a highly protein-bound drug and should not be used in patients with low albumin

• Should not be used in hypoproteinemic animals

• May cause excitement if given too slowly

Alfaxalone

• Short duration of action

• Wide margin of safety

• Use IV for induction and maintenance anesthesia

• Use IM in cats for deep sedation/light anesthesia

• It is a Schedule IV controlled substance in the US

• Not safer for cardiac patients

Alfaxalone effects on the central nervous system

Dose-dependent CNS depression

Alfaxalone effects on the cardiovascular system

heart rate, rhythm, blood pressure, and cardiac output are minimally affected

Alfaxalone’s effects on the respiratory system

• apnea, especially if used with inhalants

• Apnea: a temporary pause in breathing that lasts for at least 10 seconds

Alfaxalone’s effects on the musculoskeletal system

muscle relaxation with no excitement or twitching

Etomidate

• Short-acting intravenous anesthetic agent

• Minimal effect on the cardiovascular system

• Administered only IV; painful on injection

• adverse effects

  • vomiting

  • Muscle contractions minimized by premedication and slow administration

• Not commonly used

• Needs to be given over a long period of time, like an IV pump

Barbiturates

• large class of controlled drugs

• used as a general anesthetic declined due to new drug developments

• has specific uses

short-acting pentobarbital (Barbiturate)

• primary agent in euthanasia injectables

• induce and maintain general anesthesia in lab animals

• treat status epilepticus in small animals

Long-acting phenobarbital (Barbiturate)

• seizure control

Dissociative anesthetics

• Agents that induce dissociative anesthesia

• characterized by, among other things, a cataleptoid state

• unique CNS, cardiac, and respiratory effects

  • Ketamine hydrochloride, tiletamine (in telazol)

  • Guaifenisin

What are Dissociative anesthetics mode of action

• Disrupts nerve transmission in some brain sections

• Selective stimulation in parts of the brain

• Decreases windup through NMDA inhibition

• Induces a trance-like state

  • Animal appears awake

  • immobile and unaware of surroundings

Ketamine

• Dissociative anesthetics

• Peak action: 1-2 minutes after IV injection

• Duration of action: 20-30 minutes

• Metabolized:

  • Primarily metabolized in the liver or excreted unchanged in urine

  • Avoid use in animals with liver or kidney disease

Dissociative effects on the CNS

• Cataleptoid state ( a condition that simulates or resembles catalepsy.)

• intact reflexes

• central dilated pupil

• muscle tone

  • normal to muscle rigidity

  • counteract with concurrent tranquilizer

• analgesia

• potential for bizarre behavior

• may produce nystagmus- more common in cats

catalepsy

a state of unresponsiveness and immobility, resembling a trance, where reflexes may remain intact.

Dissociative effects on the cardiovascular system

• Stimulation of the sympathetic nervous system

• Increase in HR

• Increased cardiac output

• Increased mean blood pressure

• Puts a lot of strain on the cardiovascular

• May decrease inotropy

  • Screen patients for heart disease

• Can cause cardiac arrhythmias

Dissociative Effects on the respiratory system

• Respiratory depression is usually insignificant

• Apneustic respiration at a higher dose ( holding their breath)

• Overdose may cause severe respiratory depression or arrest

• Significant increase in salivation ( can cause airway obstruction)

Use of dissociative anesthetics

• Administration: IM, IV, SQ or oral

• Used in combination with other agents

  • Anesthetic induction for intubation

  • Chemical restraint/immobilization for short procedures

  • pain control

• No effective reversal agent

What are the objectives of preanesthetic medication?

• Reduce FAS

• minimize adverse drug effects

• reduce the dose of concurrent drugs

• smoother anesthetic induction and recovery

• analgesia

• muscle relaxation

• Allows for less propofol to be given

Acepromazine

• Phenothiazines

• Onset: 15 minutes IM ( takes too long to work)

• Peak: 30-60 minutes

• Duration: 4-8 hours, but highly variable in how long the sedation lasts; not good for wanting a patient to wake up quickly after a procedure

  • Can be administered IV or IM

  • There is no reversal agent

  • Metabolized by the liver

  • Will slowly cross the placenta

Acepromazine effects on the central nervous system

• Calming effect

• reluctance to move

• decreased interest in surroundings

• sedation less pronounced in cats

Acepromazine effects on the cardiovascular system

Peripheral vasodilation that leads to hypotension, increased Heart rate, and hypothermia

Acepromazine causes what to the veins

Vasodilation leading to increased blood flow and decreased blood pressure.

Acepromazine effects on the respiratory system

worsens the depressive effect of the other drugs

Acepromazine effects on the GI system

antiemetic

What does Acepromazine do to the spleen?

• Acepromazine causes splenic engorgement, which can lead to increased blood volume in the spleen and potential effects on overall circulatory dynamics.

• Causes a decrease in PCV

Acepromazine effects

• Causes variable sedation

• Vasodilation that leads to hypotension

• anti-arrhythmic

• anti-emetic

• big spleen

• There is no reversal

Benzodiazepines

• A group of minor tranquilizers

  • Diazepam

  • Zolazepam- a combination drug

  • midazolam

• has a rapid onset of action

• A short duration of action

• Is a DEA Schedule IV controlled substance

Benzodiazepines effects on the central nervous

• has a calming and anti-anxiety effect only in old or ill patients

• Disorientation and excitement in young and healthy dogs

• Dysphoria and aggression in cats

• Anticonvulsant use with animals having seizures ( does not prevent seizures)

Benzodiazepines effects on the cardiovascular and respiratory systems

has minimal effect with a high margin of safety

Benzodiazepines effects on the skeletal muscle

causes skeletal muscle relaxation

Benzodiazepines is a BLANK general anesthetic

• a potentiate

• allows for larger doses

Benzodiazepines is A BLANK for cats and ruminants

Appetite stimulant

What are the uses of Diazepam

• Not a water-soluble medication; can’t be combined in a syringe with other drugs

  • Ketamine can be the exception to this

  • Commonly used with ketamine to induce anesthesia in small animals and horses

• has to be administered IV slowly, or it can be given rectally for seizures

  • oral diazepam in cats can cause liver failure

  • IM administration can cause irritation and abscess

What are the uses for Midazolam?

• It is water-soluble, so it can be mixed with other medications

• Administered IM or SC

• Excellent sedative for swine, ferrets, rabbits, and birds

• Excellent per-med when combined with opioids in older, compromised patients

  • Causes excitement in younger patients

Summary of Benzodiazepines

• Is a mild sedative

• heart safe

• anticonvulsant

• Causes hyperactivity in young patients

• Reversible with flumazenil

Alpha2-adrenoceptor agonists

• A non-controlled agent

• acts on the alpha receptors of the sympathetic nervous system

  • Decreases release of norepinephrine

  • No fight-or-flight response

• Metabolized in the liver; excreted in the urine

• rapid sedation that has a 1- 2 hour duration

  • duration of effect typically longer in dogs than in cats

• readily reversed with alpha-2 antagonists

Medications that are in the alpha 2- agonists class

• Dexmedetomidine ( Dexdomitor)

• Xylazine ( rompun,anaSed)

• Medetomidine-vatinoxan (Zenalpha)

• detomidine (Dormosedan)

• Romifidine ( Sedivet)

The effects of Alpha 2 agonists on the cardiovascular system in the early phase

• Dose-dependent vasoconstriction and hypotension ( causes a dramatic vasoconstriction of everything)

• bradycardia

• Cardiac arrhythmias, such as 2nd-degree AV block, can reduce cardiac output due to decreased heart rate.

The effects of Alpha 2 agonists on the cardiovascular system in the late phase

• Decreased cardiac output

• hypotension and further bradycardia

The effects of Alpha 2 agonists on the Central nervous system

• Has a dose-dependent sedative effect

• The analgesia is short-acting (Dexdom should not be used by itself, as it does not provide proper pain relief)

• hypothermia

• Aggressive behavior ( alpha-1) does not happen often

Why should dexdom be used with other medications

to provide adequate pain relief and prevent inadequate analgesia.

The effects of Alpha 2 agonists on the respiratory system

• dose-dependent depression

• More severe if given with other drugs

What are some other effects of alpha 2 agonists

• causes MAC-reduction

• muscle relaxation

• vomiting: immediate response seen in cats and dogs, but seen more often when given IM or SQ

How to used Dexmedetomidine

• 2 to 5 mcg/kg when used as part of a multimodal protocol

• Can be given IM or IV

• Likely to cause vomiting if given SQ

• Dexmedetomidine works synergistically with opioids, reducing the dose requirements of each ( allows for much smoother sedation)

• Needs to be avoided in cardiac patients, geriatric, diabetic, pregnant, neonatal, or profoundly ill patients.

Alpha 2- antagonists

• Reverses all effects of alpha-2 agonists

  • Beneficial and detrimental effects

  • zenalpha is a combo agonist-antagonist ( the medetomidine can still be reversed)

• Administered IM

What are the effects of an overdose of an Alpha2-antagonists

• Neurological: excitement and muscle tremors

• Cardiovascular: hypotension and tachycardia

• Gastrointestinal: salivation and diarrhea

a summary of Alpha2 effects

• Sedation

• bradycardia

• emetic

• vasoconstriction

• some analgesia

• reversible

Opioids

• Produce analgesia and sedation effects

• Anesthetic induction when combined with other drugs

• classified as agonists, partial agonists, agonists-antagonists, or antagonists

Sevoflurane is expected to provide a more rapid anesthetic induction than isoflurane due to its lower ________________.

blood-gas partition coefficient

Which of the following statements is INCORRECT?

A morbidly obese dog will require more anesthetic per unit body weight than a dog of the same breed with a healthy body condition score.

NMDA receptor antagonist used to induce dissociative anesthesia

Ketamine

Sedative medication that is contraindicated in abdominal surgery due to causing splenomegaly

acepromazine

Local anesthetic also used to treat ventricular arrhythmias

lidocaine

Fast-acting injectable anesthetic delivered in a lipid emulsion

Propofol

Commonly used inhalant anesthetic agent known for rapid induction and recovery

sevoflurane

Potent sedative that cause vasoconstriction and bradycardia in its initial phase

dexmedetomidine

Which physical parameter is assessed by lightly tapping the skin near the medial or lateral canthus?

palpebral reflex

When performing chest compressions using the thoracic pump method, the chest should be compressed to ________________________ .

1/3 to 1/2 the width of the chest