1
Q
fasting pre anesthesia cats and dogs
A
-allow free access to water
Young animals: require shorter fasting times (hypoglycemia)
- 6-16 weeks: 4 hours
- Older than 16 weeks: 6-8 hours
2
Q
Aims of premedication
A
-Aims of premedication
* Sedation and anxiolysis (fear free)
* Facilitate animal handling
* Balanced anesthetic technique
* Analgesia
* Smooth and quiet recovery
3
Q
pre medication opiods + sedatives + anticholinergics drugs small animals
A
-opioids: hydro, methadone, bupernorphrine.
sedatives: ace, dexmedatomadine, midazolam.
anticholinergics: atropine, glycopyrrolate.
4
Q
pre medication for dogs ASA 1-2
A
calm dogs: ace 0.01-0.5/ hydro 0.1 or dex 1-5 /hydro 0.1
excited dogs: ace 0.1/dex 1-10/hydro 0.1
aggressive dogs add ketamine 1-10mg/kg.
5
Q
Premedication for Cats (ASA 1-2)
Standard protocol
A
-Dexmedetomidine: 8-30 μg/kg &
* Hydromorphone: 0.1 mg/kg
6
Q
heavy cat sedation kitty magic premedication
A
-more reliable ketamine based
-Dex/midazolam/ butorphanol
-dex/ketamine/butorphanol
-alfalaone/butorphanol/midazalan
7
Q
Midazolam for sedation in young cats
A
-not great in cats or young animals
-leads to excitement
-can reverse with flumazenil but need to add top up for sedation with dex or can use dex + ketamine.
8
Q
dog/cat induction of anesthesia drugs
A
-propofol
-daizepam/ ketaine
-alfaxalone
-mask induction (cats) not dogs
9
Q
ABCs of anesthesia induciton
A
A: airway intubation
B: breathing, ascultate lung sounds, check tube.
C: circulation, listen to heart beat
D: depth and drugs, assess depth pf anethesia and turn on vaporizer.
E: equipement, BP
F: fluids
10
Q
Intubation Dog - TECHNIQUE
A
-sternal, lateral or dorsal
-apply lube to tube
-open dogs mouth, pul tounge forward
-straighten head, extend tongue
* Put tip of laryngoscope blade on base of tongue, NOT on epiglottis
* Insert endotracheal tube under visualization
* Inflate cuff and check for leaks
* Secure tube
11
Q
How to confirm Endo-Tracheal Intubation?
A
- Direct visualization (use laryngoscope)
- Rebreathing bag
- Chest excursions
- Palpation of ONE trachea below the larynx
- Capnograph
-ascultate lung sounds both sides (gold standard) during manual ventilation
-hair test
12
Q
fluid rates during anesthesia cats/ dogs
A
CATS: 3 mL/kg/hr
DOGS: 5 mL/kg/hr
13
Q
Extubation in Small Animals
A
- Don’t untie tube until patient has reached final recovery spot
- ET-tube cuff should not be deflated until just before extubation
- Dogs: Extubation on return of swallowing reflex
- Cats: need to be extubated sooner
- On return of good palpebral reflex, ear flick reflex
- Prone to laryngospasm or laryngeal edema.
14
Q
difference in exotic animals vs dogs and cats
A
- Higher Metabolic rate, smaller reserves of glycogen predisposes to HYPOGLYCEMIA
- Higher oxygen consumption reduced tolerance to HYOXEMIA
- HYPOTHERMIA:
- High body surface area to volume ratio
- Radiant heat loss – cover patient
15
Q
Respiratory System - Rabbit
A
- Visualization of larynx difficult
- Prone to laryngospasm
- Obligate nasal breathers
- Thoracic cavity: very small, small tidal volume (4-6mL/kg)
16
Q
Digestive system - Rabbit
A
-allow water
-can not vomit
-fast 1-2 hr before
-dont want any food in oral cavity
-post op ileus is common
-encourage food after anesthetic
17
Q
how to reduce risk with exotic anesthesia
A
-know normal parameters
-full exam and history
-pre op blood work
-dont starve
-accurate weight
- Always calculate doses for anesthetic agents, reversals and emergenc drugs!
18
Q
anethetic protocal for exotics
A
-premedication: reduce stress, induction, anesthetic sparing, analgesia
19
Q
acepromazine (pre med)
A
- 0.1-0.25 mg/kg (IM, SC, IV)
- Long duration, not reversible – prolonged recovery
- Peak effect after 30-45 min
- Hypotension: peripheral α1 receptor blockade – vasodilation
- Only use in healthy animals, not great for exotics
20
Q
Midazolam (pre med)
A
-great for small mammels, rabbits, not great for cats and dogs causes excitment
* 0.5 - 2mg/kg (IM, SC, IV)
* Water soluble can be administered IM
* Minimal cardiopulmonary effects
* Produces moderate sedation and muscle relaxation
* Reversal: Flumazenil (0.05-0.1mg/kg IV, IM)
* Combine with an opioid
21
Q
Dexmedetomidine (pre med)
A
- 0.02-0.05mg/kg (IM, SC)
- Mild to profound sedation
- Respiratory and cardiovascular depression
- Peripheral vasoconstriction
- Reversible with Atipamezole
- Combine with an opioid
22
Q
Opioids (pre med)
A
- Provide analgesia and will increase sedation
- Reversible with Naloxone (0.01-0.1mg/kg, IM, IV)
Buprenorphine - 0.05 - 0.1mg/kg (IM, SC, IV), 6-8 hours
Butorphanol - 0.5 - 2 mg/kg (IM, SC, IV) 2 hours
Hydromorphone - 0.1- 0.3mg/kg (IM, SC, IV)
Methadone - 0.3-0.7 mg/kg (IM, SC, IV
23
Q
Anticholinergic Drugs
A
- Not routinely administered as premedication
- Used to treat bradycardia
- Negative effects on gastrointestinal motility!
Atropine - 0.1-0.2 mg/kg (IM, SC, IV)
- 61% of rabbits possess atropine esterase
Glycopyrrolate - 0.01-0.1mg/kg (IM, SC, IV)
24
Q
Induction of Anesthesia exotics
A
- Always preoxygenate
- Always have a person monitor patient during induction/intubation
- Have monitoring attached to patient
- IV catheter
-* Masking down should not be first option for rabbits
25
Induction of Anesthesia
INJECTABLE AGENTS exotics
-ketamine
-propofol
-alfalaxlone
TITRATE TO EFFECT TO AVOID INDUCTION APNEA
26
Induction of Anesthesia- VOLATILE AGENTS exotics
* Should only be 2 nd choice to IV induction
* Always use with premedication to reduce:
- Stress/ struggling
-oxygenate if possible
-ISO mac 2.5%, induction apnea
-Sevo man 3.5 faster, less breath holding.
27
facemask for exotics
* Close-fitting:
- Reduce environmental contamination
- Avoid inhalation of room air
* Diaphragm can be adapted using an exam glove
* Clear: visual assessment
* Low volume: minimize dead space
28
Lidocaine Constant Rate Infusions exotics
* Prokinetic effects
* Improved food intake and fecal output in rabbits following ovariohysterectomy
* Anesthetic sparing (reduces isoflurane MAC)
* Analgesic
* Anti-inflammatory/anti-endotoxin
29
why we use rabbit intubation
-mask
-V-gel
-intubation (blind, or direct visualization with laryngoscope)
-protects airway, allows O2 and positive pressure ventilation.
30
rabit intubation technique
* 2.0 -3.5mm (un)cuffed ET tube
* Ensure rabbit is adequately anesthetized
* Pre-oxygenate
* Prone to laryngospasm: Use lidocaine (careful toxic dose)
* Sternal recumbency with hyper-extended neck
- to align the larynx and the trachea with the oropharynx
* Continuously monitor heart rate during induction/intubation
31
Rabbit Anesthesia - INTRAVENOUS ACCESS
* In conscious rabbit – apply local anesthetic cream (EMLA)
§ Cephalic vein
§ Lateral saphenous
§ Marginal auricular vein
- Complications: sloughing, chemical phlebitis,
mechanical irritation from catheter or bandage
- Don’t use central auricular artery
§ Fluids: 10 mL/kg/h
32
blind intubation technique
* Premeasure ETT/atomizer to level of larynx
* Sternal recumbency and hyper-extend neck
* Insert ET-tube to pre-measured point
- Condensation appearing in tube during expiration
* Instill lidocaine 2% (neat) via small catheter/atomizer through ET tube
* Gently advance ET-tube during inspiration while:
- Listening at the connector end of the tube
- Watching capnograph
33
Rabbit Intubation - Complications
* Difficult placement
* Laryngospasm
* Trauma to the oropharyngeal soft tissue
* Tube dislodgement, occlusion, and kinking
* Postintubation oropharyngeal swelling
34
Rabbit anesthesia – MONITORING
Anesthetic depth:
* Palpebral reflex, eve position: unreliable
* Nictitans membrane will move over cornea
* Corneal reflex should be maintained
Cardiovascular System
* Auscultation
* Doppler
* Pulse oximetry: ear, tongue, digit
* ECG
* Temperature (Avoid Hypo and Hyperthermia)
35
procedural considerations for field anesthesia
-know injury, or procedure before hand so know what drugs/ equipment to bring. top ups, local block, standing sedation ect.
-*Only simple procedures of short duration should be attempted in the field.
36
minimum anesthesia equipment for horse field procedures
* IV catheters
* Sufficient amount of drugs
* Soft ropes with an appropriate halter
* Small towels – covering/protecting eyes
* OXYGEN supplementation:
* Horses are very prone to hypoxemia during GA (V/Q mismatch) E tank with nasal insufflation.
37
sedation/ premedication in horses acepromazine
* Dose = 0.01 – 0.05 mg/kg IV/IM
* May be useful as a ‘pre-med’ often in combination with other drugs
* Can be used alone for non-painful procedures, calm down mare to work with foal
* Sufficient time should be allowed for it to work (30 – 40 minutes)
* Provides anti-arrhythmic effect
* Vasodilation and hypotension does occur
(Alpha1 antagonism)
* Penile prolapse:
* Should be avoided in breeding stallion
38
sedation/ premedication in horses alpha 2 agonists
-more reliable sedation, analgesia, muscle relaxation and some ataxia.
-standing sedation: use low dose.
-preanesthetic medication use high dose.
-transient bradycardia
-xylazine lasts 20 mins, romf lasts 40 mins.
39
ALPHA2 AGONIST DRUGS AND opiods FOR SEDATION
* Butorphanol (0.02 – 0.03 mg/kg IV)
* Morphine (0.1 mg/kg) – use a longer lasting alpha2 agonist
* Can mix drugs OR give drugs separatel
40
* Alpha2 agonists with opioids and acepromazine (0.05 mg/kg IV) for sedation
* Detomidine/Butorphanol/Acepromazine mix is common
* Detomidine/Acepromazine is good for mares
* Romifidine mixed with acepromazine = precipitation – DO NOT administer
41
induction of field horse anesthesia steps
-1.)pre anethetic prep: fast 12 hr, water up to 1 hr before. history, exam.
-2.)facilities/enviro
-3.) place IV catheter (sometimes)
-4.) check halters and ropes
-5.) protect facial nerves, eye. remove halter
-6.) select site
42
COMMON ANESTHETIC horse FIELD INDUCTION PROTOCOLS
-administer xylazine (1mg/kg IV) or detamadine (wait a few minutes for peak sedation) can mix diapepam with ketamine.
* Diazepam is optional but does ‘smooth’ induction
* Butorphanol (0.05 mg/kg IV) can be added
* Often wait until horse is induced to minimize the potential for excitement
* Consider local anesthetic techniques
43
when to use ketamine in induction of anesthesia field horses
* ‘Nose to Knees’ sedation with (aplha 2 or ace) before induction with ketamine
* Check heart rate
* DO NOT INDUCE WITH KETAMINE IF:
* Sedation is poor – top up sedation with alpha2 agonist
* HR is extremely low – wait until it comes back up (2 – 3 minutes)
44
MAINTENANCE OF ANESTHESIA horses field with top ups
* Ketamine + Xylazine:
* Mix 1 / 3 – 1 / 2 the pre-medication and induction doses
* This may provide 2 – 3 ‘top – ups’
* Given every 10 – 15 minutes depending on depth of anesthesia
*Ketamine is slightly cumulative:
* After the third ‘top – up’ the dosing interval should be increased OR subsequent doses decreased
45
MAINTENANCE OF ANESTHESIA: ‘TRIPLE – DRIP horses field
-Indicated when need a little longer duration of anesthetic time
* Maximum anesthesia time 90 min
* In 1 liter 5% Guaifenesin add:
* 500 mg Xylazine
* 1000 mg Ketamine
* Given at a rate of about 2 mL/kg/hr.
-good for 60 min procedures, analgesia, good recovery
46
CHECKING DEPTH OF ANESTHESIA horse field
* Pulse quality, mucous membrane color, CRT, HR
* Respiratory rate and depth
* Check eye reflexes:
* Palpebral reflex is ‘brisk’
* At a ‘LIGHT’ plane of anesthesia:
* Spontaneous blinking
* Tearing
* Nystagmus
* Don’t use corneal reflexes
-monitor with portable BP doppler and sphygmomanometer or pulse oximeter.
47
recovery of horse field anesthesia
-dont usually reverse
-control recovery
-keep safe
-avoid noise
-keep eyes covered
-consider using xylazie if you topped up with ketamine in the last 10 mins and can cause excitable recover.
-long procedure place cathitor
48
analgesia for horse field drugs
* NSAIDs: Used pre-emptively to minimize surgical/inflammatory pain
* Opioids - Provide good analgesia and increase sedation
-butorphanol 60-90 min
-morphine 2-4 hr
-buprenorphone 12 hr slower onset 30 mins.
* Local Anesthetic Blocks: Can provide a useful part of a balanced analgesia, Intra-testicular for castration
49
Cardio Pulmonary Arrest (CPA)
Etiology and outcome
-survival rate of CPA is poo 4-9%
3 catagories of patients
-anesthesia and drug related
-underlying disease
-reversible disease/injury
50
Compressions – Thoracic Pump
* For animals > 10kg
* Compression over widest part of the thorax
* Increases overall intra-thoracic pressure, compresses aorta moving blood out of thorax.
51
Chest compression technique
Flat-chested confirmation
-can put dog in dorsal recumbency and it stays without being held
-flat chested dogs
-between legs on sternum like human CPA
52
ventilation during CPA
Use 100% Oxygen!
* Use Anesthesia machine or Ambu®-bag
* Don’t forget to turn off the vaporizer
* Room air 21% O 2/ higher than own breath
53
airway intubation during CPA
* Securing airway for provision of ventilation is critical
* Check for any obstruction (blood, fluid) – have suction ready
-mask: not ideal, must stop compressions to ventilate, do 30 compressions 2 breaths ratio.
-MOUTH TO SNOUT, possible if emergency
-Intubation: same as usual but in lateral recumbency, can be performed while doing chest compressions
54
ventilation rate during CPA
* Respiratory Rate: 10 breaths per minute
* Do NOT go too fast!
* Tidal volume 10 mL/kg
* Inspiratory time: 1 second
* Airway pressure: sufficient to result in a visible chest rise
* Airway Pressure (IPPV) 30-40 cmH2O during chest compression
* In between chest compressions less than 20 cmH2O.
55
Advanced Life Support (ALS)
* Initiate monitoring: ECG, Capnography, Femoral pulse
* IV Access
* Reversals
56
Monitoring – ECG under CPA
* Diagnosis of arrest rhythm
* Determine ALS therapy (pharmacologic vs defibrillation)
* ECG analysis: never interrupt 2 min cycle of chest compression
-no not delay resumption of chest compressions
57
arrest rhythms types
Non-shockable:
* Asystole
* Pulseless Electrical Activity (PEA)
Shockable:
* Pulseless Ventricular Tachycardia
* Ventricular Fibrillation (Vfib)
- Initial rhythm can change during CPR
58
asystole in CPA
* Most common arrest rhythm in dogs and cats
* Non-shockable
* “Flat line”: indicates no electrical activity in the heart
* Treatment:
* Continue basic life support: supplements heart action
* Drugs:
* Recommended Epinephrine +/- vasopressin (every other cycle)
* Atropine: (only once, early on
59
Pulseless Electrical Activity rythm in CPA
* Common arrest rhythm in veterinary patients
- Overdose GA (barbiturates)
* Non-shockable
* Normal heart rate and rhythm on ECG, but NO myocardial contractility
* Heart rate less than 200bpm
* Continue basic life support: supplements heart action
* Drugs:
* Recommended Epinephrine +/- vasopressin (every other cycle)
60
Ventricular Fibrillation (fine or coarse) in CPA
* Unorganized electrical activity in the heart
-> poor myocardial contractions -> loss of cardiac output
* Most common initial arrest rhythm in people
* Uncommon in cats and dog
* Treatment:
- Electrical defibrillation
- Precordial thump
61
Electrical Defibrillation
* Electrical impulse depolarizes myocardial cells “reset button”
* Electrical and uncoordinated mechanical activity stops
* Allows regular pacemaker cells to regain control ->
- Sinus rhythm
- Asystole: if SA node doesn’t refire
* Start BLS at the same time you charge the defibrillator
62
how to use electrical defibrillation
* Lubricate paddles with conductive gel
* Do not use alcohol – combustible
* Place patient in dorsal recumbency
* Place paddles on opposite sides of thorax
- Over the heart at costo-chondral junction
* Check that NO one is in contact with patient or table
* Shout ‘CLEAR’ when ready
63
after defibrillating patient
* Restart chest compressions immediately! (full 2-min cycle)
* Desired outcome:
* Normal ECG rhythm
* Asystole
-resume chest compressions for 2 mins before we check ECG
-if shockable rhythm persists after the first defibrillation attempt
* Double energy dose for next shock
* Stay at that dose for subsequent doses
* Low dose epinephrine
64
Monitoring - End tidal CO2 during CPA
* Provides information about cardiac output and pulmonary perfusion
* Measure of efficacy of chest compressions
- EtCO2 < 18 mmHg means poor perfusion (poor cardiac output)
* MOST predictive prognostic indicator:
* Higher EtCO 2 values (> 15mmHg) during CPR associated with increased rate of return of
spontaneous circulation
65
Epinephrine during CPA
* Catecholamine with nonspecific α and β adrenergic effects
* Alpha mediated vasoconstriction: key for CPR - > increased myocardial/cerebral blood flow
* Blood volume - > central circulation
* Βeta mediated effects may be harmful: - > increased contractility and HR -> increased
myocardial O 2 demand -> myocardial ischemia and arrhythmias
* Dose:
- Low dose: (0.01 mg/kg) IV
- High dose: (0.1mg/kg) NO LONGER RECOMMENDED
-repeat every 2-5 mins of arrest
-doesnt work in acidodic, hypoxemic or hypothermic patients.
66
routes of drug administration under CPA
-preffered IV
-ntraosseous (IO)
* If can’t achieve IV within 2 min.
-dont use intracardiac
-intratracheal: if other 2 are not possible.
67
Drug administration - Intratracheal technique during CPA
* Only if IV or IO are not possible
* Pass a feeding tube or red rubber tube down ET tube to level of carina
* Flush the catheter with air and give a few good breaths
* Drug dose is doubled!
* Epinephrine use “high dose”
* Drugs diluted in 0.9% NaCl
* Atropine, Epinephrine, Vasopressin, Lidocaine, Naloxone
68
vasopressin in CPA
* Non-catecholamine vasopressor
* Acts on V1 receptors of the vascular smooth muscle
* Profound peripheral vasoconstriction
* More effective in hypoxemic, hypothermic, acidemic environment
* Dose: 0.8 IU/kg IV (Double for IT)
* As a substitute or in combination with epinephrine every 3-5min
69
atropine in CPA
* Most useful in patients that have arrested due to high vagal tone
* Vagolytic drug inhibits parasympathetic tone
- Increases heart rate
- Increase AV nodal conduction
* Dose: 0.04 mg/kg IV
- As early as possible during CPR
- Only once
70
CPA resuscitation complications
* Ischemia-reperfusion injury: Sepsis like syndrome
* Brain injury: Injury occurs during reperfusion, Mannitol, hypothermia, seizure prophylaxis
* Myocardial dysfunction
* Something killed you originally!
* Persistent precipitating pathology
71
clinical signs of cardiopulmonary arrest CPA
* Unresponsive
* Lack of Spontaneous ventilation
* Lack of Heart beat
Unresponsive patient (5-10 sec)
* STIMULATE – no response – call for help
72
Cardiopulmonary Arrest (CPA)
Complete cessation of effective: VENTILATION and CIRCULATION
Definitive clinical signs of CPA:
* Loss of consciousness – collapse - unresponsiveness
* Respiratory arrest
* No heartbeat, no pulse (can take > 30s to identify!) so dont use this, start CPR in unresponsive, apneic patients don't wait and try to find heart beat.
73
Basic life support- First step in CPA
* Delays in initiation of CPR are associated with worse outcome
* Benefits of early CPR outweigh risks
-call for help
-3 minute emergency (brain damage after that)
-turn off anesthetic
-check airway
-early ventilation is most important in dogs and cats
-Single rescuer BLS: 30 compressions : 2 breaths
74
Basic life support (BLS) steps
-2 full mins, no pauses
-1: chest compressions 100-120/ min
-2: ventilation every 6 seconds
-pause and check pulse and rythm
-3 monitoring
-4: IV access
-5: reversal
75
chest compressions
* Rate: 100-120 bpm
* Depth: 25% of depth/width of chest
* Lock your elbows! (gravity vs muscle strength)
* Duration: Rescuer fatigue! - Perform uninterrupted cycles of 2 min
* Relaxation => 1:1 compression to relaxation ratio
- Allow full chest recoil
76
Why the full recoil is so important during CPR?
-No leaning on the chest because:
* Increased intrapleural pressure
* Reduced venous return
* Suboptimal ventricular filling
77
Compressions – Cardiac Pump
* For animals < 10kg or dogs with narrow, keel-chest conformation
* Direct compression of the heart (3 rd to 6 th IC space)
-> pushes blood out into circulation
* Can also cup hand around sternum to squeeze with one hand
* Avoid using fingertips (no pinching)
A. One-handed thumb-to-fingers
B. Circumferential (two hands or two thumbs)
C. One-handed palm
78
Multimodal (balanced) Analgesic Plan
1.) OPIODS
2.) NSAIDS
3.) LOCAL ANESTHETIC
4. Decide if administration of α2-agonist would be beneficial
5. Choose analgesic adjuncts (ketamine, lidocaine, gabapentin) if needed
6. Use nonpharmacologic techniques to minimize pain
79
Differentiating pain from other conditions:
Uncoordinated agitated activity and vocalizing causes
* Pain
* Emergence delirium
* Dysphoria
* Anxiety
80
Emergence Delirium perioperative
* Anesthesia related behavior
* Attributed to residual inhalant anesthesia
* Only in immediate recovery period (after extubation)
* Self limiting – resolve within several minutes
* Sometimes requires sedation
81
Dysphoria perioperative
* Reaction to (“overdose” of) opioids, not always some animals just it with opiods
* Animals difficult to distract or calm by interaction
* Don’t respond to light palpation of painful area
* Treatment:
- Sedation (low dose acepromazine, dexmedetomidine)
- Partial opioid reversal (careful titration) butorphanol or Naloxon (μ antagonist) 2-10μg/kg (IV)
82
ANXIETY perioperative
* Animals can be temporarily distracted
* Calmed by interaction, will resume behavior when left alone
* NO source of pain can be identified!
* Animals responsive to TLC, sedation (trazadone, gabapentin)
* Limit time in hospital
83
MU AGONIST OPIOIDS
MU AGONIST OPIOIDS
full agonists: hydro, meth, morphine, fetanyl
partial:buprenorphone
* Analgesia +++
* Sedation +++
* Vomiting ++
* Bradycardia ++
* Respiratory depression ++
REVERSIBLE with NALOXONE: (10-40 μg/kg
84
Hydromorphone (0.05-0.2mg/kg)
-opioid
* One dose lasts 1-4 hours
* Dose-dependent side effects:
* Panting (dogs)
* Nausea, vomiting
* Dysphoria, hyperthermia? (cats)
* Respiratory depression, bradycardia
* Urine retention, GI-ileus
85
Buprenorphine (20 – 40 μg/kg)
* Partial μ-agonist opioid, popular for cats
* Preferred route of administration: IV, IM
* Avoid OTM (oral transmucosal) and SC
* Slow onset time
* Duration: 4-6 hours
* Rarely causes vomiting or dysphoria
* Euphoria in cats
* Ideal for mild to moderate pain
* Avoid if planning to use a pure μ-agonist in the near future
86
Butorphanol
-opioid
* Kappa agonist
* (0.2-0.4 mg/kg IV, IM, SC)
* Can reverse μ-opioid agonist (dilute, slow to effect)
* 30 -90 min duration
* Weak analgesic
* Mild sedative
* Potent antitussive
* Does not cause panting in dogs
87
Opioids: Continuous Rate Infusions
* Provides consistent levels of analgesia of opioids
* Adverse side effects are minimized
(compared to intermittent boluses)
* Less drug used overall
-fetnal strongest analgesia opioid, * Potent analgesic, sedative, respiratory depression
88
Effects of Ph
-pH changes effect enzyme function and excitability of nerve and muscle cells
-ACIDOSIS: low ph >7.35
-alkalosis: high Ph >7.45
89
acidosis
decreased PH= decreased excitability. alters cardiac contractions.
-decreased vascular response to catecholamines.
-can lead to loss of consiousness.
90
alkalosis
-increased pH = increased excitability.
* Impaired neurological function
* Impaired muscular function
* Tingling sensations, nervousness,
muscle twitches
91
metabolic acidosis
* Caused by an imbalance in the production and excretion of acids or bases by the KIDNEYS
-pH < 7.35, HCO3- < 22 mmol/L
* Too much acid build up:
* Shock
* DKA
* Renal Failure
* Diarrhea
* Diuretics
* Lactic Acidosis
* Ethylene Glycol Poisoning
* Clinical Signs:
* Headache, lethargy, nausea, anorexia, vomiting,
diarrhea, coma , death
92
metabolic alkalosis
* Caused by an imbalance in the production and excretion of acids or bases by the KIDNEYS
-ALKALOSIS = pH > 7.45, HCO3- > 26 mmol/L
* Excess loss of acid in the blood:
* Excessive vomiting
* GI obstruction
* Clinical Signs:
* Dizziness, lethargy, weakness, muscle twitching,
cramps, tetany, coma, death
93
respiratory acidosis
-caused by lungs or breathing abnormalities
-ACIDOSIS = pH < 7.35, PaCO2 > 45 mmHg
* Caused by HYPOVENTILATION:
* Obstruction of gas exchange
* Respiratory depression
* Clinical signs:
* Dyspnea, respiratory distress, shallow
respirations, tachycardia, dysrhythmias,
headache, restlessness, confusion
94
respiratory alkalosis
-caused by lungs or breathing abnormalities
ALKALOSIS = pH > 7.45, PaCO2 < 35 mmHg
* Caused by HYPERVENTILATION:
* Pain
* Fear
* Anxiety
* Fever
* Clinical signs:
* Dyspnea, nausea, vomiting, headaches,
restlessness, lethargy, coma
95
chemical buffering in acidosis
-an immediate response to changes in acid/base balance
* ACIDOSIS – compensatory response:
* H + moves into the cell while K + moves
out of the cell
* Results in HYPERKALEMIA
96
chemical buffering in alkalosis
-an immediate response to changes in acid/ base balance
* ALKALOSIS – compensatory response:
* H + moves out of the cell while K + moves
into the cell
* Results in HYPOKALEMIA
97
respiratory buffering in pH
* Normal by product of cell metabolism = CO 2
* CO2 travels via the blood → lungs
* Excessive CO2 combines with H 2O → H 2CO3
-blood ph changes due to how much carbonic acid (H2CO3) is present
-lungs change respiration
-responds in seconds to minutes
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chemoreceptors
* In the blood – concentrations of the
following stimulate the RESPIRATORY
RATE:
* CO2
* pH
* O2
* Central chemoreceptors located on the
ventral surface of the medulla respond to
changes in pH of the CSF
* Peripheral chemoreceptors located in the
CAROTID and AORTIC arches
99
renal buffering in pH
* To maintain blood pH – kidneys retain or excrete bicarbonate (HCO 3-)
to compensate
* When pH decreases – kidneys retain HCO3-
* When pH increases – kidneys excrete HCO3-
* RENAL BUFFERING – may take hours to days
100
NSAIDs for analgesia in horses
-analgesic and anti-inflammatory
-side effects with chronic use: gastric and colonic ulcers, renal tubule necrosis
-usages: administered pre op anticipating inflammation during surgery.
-Phenylbutazone: musculoskeletal pain
-Flunixin meglumine (banamine) soft injury, abdominal pain, endotoxemia
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alpha 2 agonists in horses analgesia
* Xylazine
* Detomidine
* Medetomidine
* Dexmedetomidine
* Romifidine
- Usages:
* Pre-medication primarily for sedation
* Intra-operatively as a Constant rate infusion for analgesia
* Post-operatively for sedation to ensure smooth recoveries from inhalational anesthesia
102
alpha 2 agonists in horses analgesia benifits and effects
* Benefits:
* Analgesia
* Sedation
* Anesthetic sparing
* Potential negative side effects:
* Bradycardia
* Vasoconstriction and hypertension
* Increased urine output (Hyperglycemic diuresis)
* Decreased GI motility
* Ataxia
103
xylazine in horse anelgesia
* Used with KETAMINE and GGE (Guaifenesin) in ‘triple
drip’
* Total Intravenous Anesthesia (TIVA)
104
DETOMIDINE in horse analgesia
* Used for sedation and analgesia for longer standing procedures, less ataxia than xylazine.
* Often combined with an opioid
* Administered as an infusion (Variable rate infusion)
-want noes to knees sedation so protect neck when in stocks so they dont occlude airway from pressing it on bars
105
DEXMEDETOMIDINE in horse analgesia
* Used for invasive procedures with inhalational
anesthesia (PIVA)
106
KETAMINE for analgesia in horses
* Used as an induction agent
* Used in ‘triple drip’ mixture
* Provides great analgesia:
* Somatic
* NMDA antagonism – good for chronic (‘wind up’) pain
* Other beneficial effects:
* Local anesthetic effects
* Potent anti-inflammatory effects
* Anesthetic sparing (↓ MAC by 37%)
-can be used at very low doses in conscious horse
-risk of excitement which can be controlled with sedatives
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Mu agonist opiods
1. Morphine (used most in horses)
2. Meperidine
3. Pentazocine
4. Methadone
5. Fentanyl
6. Alfentanil
7. Remifentanil
108
Partial Mu agonist and kappa agonsit opioids used in Large animal
-Partial Mu agonist: Buprenorphine
-Kappa Agonist: Butorphanol (used commonly in horses)
109
use of opioids in LA analgesia
* Primarily used intra-operatively:
* Not good sedatives unless combined with an alpha-2 agonist
* Appear to be effective in horses in pain OR undergoing
invasive procedures:
* Good analgesia
* Do not reduce isoflurane requirements, not anesthetic sparing in horses and LA due to potential for excitement.
-are anethetic sparing in dogs and cats
110
OPIOIDS – SIDE EFFECTS LA
-Excitement:
* Control with sedatives – Acepromazine, Alpha-2 agonists.
-to decrease excitement: detamadine aplha 2 first then use butorphenol (opioid)
* Decreased GI motility:
* Decrease incidence if administered IM, or one bolus, and dont give long term.
111
OPIOIDS – DOSAGE GUIDELINES LA analgesia
* The more severe the pain, the greater the dose of opioid analgesic
required, and the lower the risk of excitatory side effects.
* In pain free horses – giving appropriate doses of alpha-2 agonists
matched for duration of action eliminates the risk of excitation.
* In pain free horses – sedation with acepromazine reduces but does not
eliminate the risk of excitation
-should be given to effect
-signs of underdose (pain)
-signs of overdosage (excitement) hard to determine difference
112
MORPHINE in LA analgesia
* Used at low doses for horses in pain:
* 0.05 – 0.1 mg/kg IV or IM (Duration approximately 4 hours)
* Side effects when use repeated dosing or high dosages:
* Reduced GI motility
* Urinary retention
* Increased locomotor activity and ataxia
-effects: cardio stimulation when used alone.
-can make the effects of sedatives worse when used with standing sedation
-intra-articular analgesia.
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MORPHINE – INTRAOPERATIVE USES horses
* Constant Rate Infusion (CRI): low dose, Improved recovery characteristics
* Higher dosages (0.25 mg/kg):
* Used for analgesia
* May increase Isoflurane requirements
* May result in rough recoveries
* Clinical dosages (0.05 – 0.1 mg/kg):
* Do not affect recovery quality
114
REMIFENTANIL used in horses analgesia
* Used with success intra-operatively
* Dosage: 3-6 mcg/kg/hr IV
* Good recoveries
* Some reported hyperthermia
* Can only be used as a CRI due to short half life
* Take care to ensure analgesia in place before turning off
115
BUPRENORPHINE for analgesia LA
-partial Mu agonist
* Long duration of action – up to 12 hours
* Side effects:
* Restlessness
* Head shaking
* Decreased GI motility for up to 4 hours
-Sub-lingual administration might prove useful:
* Dosage: 6 mcg/kg
- Some new evidence that this may provide better post-
operative analgesia than butorphanol for minimally
invasive procedures
116
BUTORPHANOL used in horse analgesia
-kappa agonsit opioid
-can still produce excitement (delta receptors) but less and less GI ileus than Mu
* Often used intra-operatively
* Effective for VISCERAL analgesia
* Duration of effect:
* 45 minutes – 1 hr
* Re-dosing is often necessary
* not anesthetic sparing
* Does provide a more ‘stable’ anesthesia
-post op: IM or infusion for several days as anaglesic
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LOCAL ANESTHETICS - LIDOCAINE horses
* As an infusion intra-operatively - WITHOUT EPINEPHRINE!!
* Pharmacological benefits:
* Analgesia
* Anti-inflammatory
* Anti-endotoxemic
* Pro-kinetic
* Anesthetic sparing
-IV low dose
* CRI 50 mcg/kg/min IV
* Stop infusion at least 30 minutes prior to recovery from general anesthesia – to prevent ATAXIA
118
PARTIAL INTRAVENOUS ANESTHESIA (PIVA) in horse analgesia
-used for anethetic sparing
-combinations for multimodel anesthesia
* Drugs in which we can use via PIVA and their indications
include:
1. Alpha-2 agonists:
* Invasive/painful procedures
* Orthopedic procedures – musculoskeletal pain and inflammation
2. Lidocaine:
* Colic surgeries
3. Opioids:
* Orthopedic surgeries
4. Ketamine:
* Somatic Analgesia – supplement other drugs
119
EPIDURALS LA
* Good for standing procedures
* Require sterile technique for placement
* Relatively easy to place in the standing horse –
sacrococcygeal (‘caudal epidural’)
* Use preservative free drugs
* Usually once or twice daily treatment
* Administer drugs SLOWLY
-can have epideral catheter for long term pain management
-ruminants: morphone lasts 10 hr in sacrococcygeal administration
120
WOUND/SOAKER CATHETERS horses
-if you have a large wound you put this at incision site and can add local block for long time pain management
* Can provide postoperative analgesia for 2 – 3 days
* Preplace during surgery
* Commercial kits are available
* Use LIDOCAINE infusions – 2 – 5 mL/hr
* Use BUPIVICAINE infusions – 2 – 5 mL every 6 – 10 hrs
121
considerations for recovery in horses
* Must stop all infusions prior to moving into the recovery
box
* Give NSAIDs if warranted
* Consider local blocks if applicable
* Usually sedate with an alpha-2 agonist:
* Xylazine: 0.2 – 0.5 mg/kg IV
* Romifidine: 10 – 25 mcg/kg IV
122
opioids in ruminant analgesia
* Dose may need to be adjusted if start to see
behavioral side effects:
* Sedation
* Dysphoria
* Excessive locomotor activity
* Excitement
* Can develop intestinal stasis with long term use of
opioid
-morphine (4-12 hr) or butorphanal (4-6 hr)
123
KETAMINE - RUMINANTS
* Benefits:
* Anesthetic sparing
* NMDA antagonist – good for chronic pain
* Good for somatic analgesia
* Typically use higher dosages than in small animals
124
LIDOCAINE - RUMINANTS
* As an infusion intra-operatively - WITHOUT EPINEPHRINE!!
* Pharmacological benefits:
* Analgesia
* Anti-inflammatory
* Anti-endotoxemic
* Pro-kinetic
* Anesthetic sparing
* Dosage* (higher than horses and small animals):
-stop infusion at least 30 mins before recovery to prevent prolonged recoveries
veterinary anesthesia
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